Safety Guidelines for Design,
Construction and Operation of Tugs
July 2014
Guidance Note
NI 617 DT R00 E
Marine & Offshore Division
92571 Neuilly sur Seine Cedex – France
Tel: + 33 (0)1 55 24 70 00 – Fax: + 33 (0)1 55 24 70 25
Marine website: http://www.veristar.com
Email: [email protected]
 2014 Bureau Veritas - All rights reserved
MARINE & OFFSHORE DIVISION
GENERAL CONDITIONS
ARTICLE 1
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ARTICLE 2
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ARTICLE 3
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are a collection of minimum requirements but not a standard or a code of construction neither a
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ARTICLE 11
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ARTICLE 13
13.1. - These General Conditions constitute the sole contractual obligations binding together the
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whether express or implied. They may be varied in writing by mutual agreement. They are not varied by any purchase order or other document of the Client serving similar purpose.
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13.3. - The definitions herein take precedence over any definitions serving the same purpose which may
appear in other documents issued by the Society.
BV Mod. Ad. ME 545 L - 7 January 2013
GUIDANCE NOTE NI 617
NI 617
Safety Guidelines for Design,
Construction and Operation of Tugs
SECTION 1
GENERAL
SECTION 2
STABILITY
SECTION 3
TOWING EQUIPMENT
SECTION 4
FIRE SAFETY FOR TUGS OF LESS THAN 500 GT
SECTION 5
LIFE SAVING APPLIANCES FOR TUGS OF LESS THAN 500 GT
SECTION 6
RADIO INSTALLATIONS FOR TUGS OF LESS THAN 300 GT
SECTION 7
NAVIGATION EQUIPMENT FOR TUGS OF LESS THAN 500 GT
SECTION 8
HULL OUTFITTING
SECTION 9
ASSISTED SHIP
July 2014
Section 1
General
1
Foreword
7
1.1
2
Introduction
2.1
2.2
2.3
2.4
3
10
Bollard Pull
Escort forces and speed
Reference towline force
Design Load
Winch Brake Holding Load
Towline breaking strength
General
1.1
2
3
12
Scope of application
Openings
2.1
2.2
12
General
Ventilation openings of machinery space and emergency generator room
Intact stability
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
12
Loading conditions
Stability criteria
Additional stability criteria for service notations harbour tug and tug
Additional stability criteria for service notation escort tug
Escort performance simulations
Escort performance trials
Operating information for service notation escort tug
Icing considerations
Elements reducing stability
Alterations
Towing Equipment
1
Towing equipment for service notations harbour tug and tug
1.1
1.2
1.3
1.4
1.5
1.6
2
Scope of application
Service notations and additional service feature
Specific considerations for escort tugs
Stability
1
Section 3
8
Definitions
4.1
4.2
4.3
4.4
4.5
4.6
Section 2
General
Typical operational profiles
Typical design arrangements
Other design arrangements
General
3.1
3.2
3.3
4
7
18
General
Documents to be submitted
Design Load
Design requirements for towing winches
Design requirements for towing hooks
Design requirements for towlines
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July 2014
1.7
1.8
1.9
1.10
2
Towing equipment for service notation escort tug
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
Section 4
Design requirements for towline guiding fittings
Design requirements for towing equipment supporting structures
Fendering
Testing requirements
21
General
Documents to be submitted
Design Load
Design requirements for escort winches
Design requirements for towlines
Design requirements for towline guiding fittings
Design requirements for towing equipment supporting structures
Testing requirements
Inclinometer
Fire Safety for Tugs of less than 500 GT
1
General
1.1
1.2
1.3
2
Scope of application
Fire safety objectives
Requirements for fire safety equipment
Fire pumps and fire main systems
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3
25
25
Purpose
Capacity
Fire pumps
Portable fire pumps
Fire main
Pressure in the fire main
Fire Hydrants
Fire-hoses
Nozzles
Fire safety measures
28
3.1
3.2
3.3
3.4
3.5
3.6
3.7
Purpose
Structural fire protection
Materials
Surface of insulation
Ventilation systems
Oil fuel arrangements
Special arrangements in Category A machinery spaces and where necessary
other machinery spaces
3.8 Arrangements for gaseous fuel for domestic purposes
3.9 Space heating
3.10 Means of escape
4
Fixed fire detection and fire-alarm systems
4.1
5
July 2014
General
Fire-extinguishing arrangements
5.1
5.2
5.3
5.4
5.5
5.6
31
31
Purpose
Fixed fire-extinguishing arrangements in Category A machinery spaces
Fixed fire-extinguishing systems
Protection of paint lockers and flammable liquid lockers
Fixed fire-extinguishing systems not required by this section
Portable Fire-extinguishers
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3
6
Fire-fighting equipment
6.1
6.2
6.3
7
Section 5
Scope of application
Requirements for life saving appliances
General
1.1
1.2
36
Scope of application
Requirements for radio installations
Navigation Equipment for Tugs of less than 500 GT
1
General
1.1
1.2
37
Scope of application
Requirements for navigation equipment
Hull Outfitting
1
Anchoring equipment
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
4
34
Radio Installations for Tugs of less than 300 GT
1
Section 8
Purpose
General
Engineering analysis
Evaluation of the alternative design and arrangements
Re-evaluation due to change of conditions
General
1.1
1.2
Section 7
32
Life Saving Appliances for Tugs of less than 500 GT
1
Section 6
General
Fire-fighter’s outfit (which includes an axe)
Description of fire control plans
Alternative design and arrangements for fire safety
7.1
7.2
7.3
7.4
7.5
32
38
Equipment number
Wire ropes
Tugs of less than 500 GT
Number of anchors
Anchors
High holding power anchors
Chain cables
Water depths greater than 82,5 m
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July 2014
Section 9
Assisted Ship
1
Towing fittings
1.1
2
43
General
Making fast
3.1
July 2014
General
Side structure
2.1
3
43
44
General
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6
Bureau Veritas
July 2014
NI 617, Sec 1
SECTION 1
1
GENERAL
Foreword
1.1
1.1.1 This Guidance Note has been developed on the basis
of cooperative research and development work performed
within the scope of the SafeTug Joint Industry Project and
through bilateral cooperation with industry stakeholders.
The purpose of the Guidance Note is to provide recommended criteria for the design, construction and operation
of tugs.
The recommended criteria are to be used in conjunction
with the Bureau Veritas Rules for The Classification of Steel
Ships (NR 467) and may be applied as an alternative to
and/or in addition to the requirements of NR 467, Pt D,
Ch 14 as applicable for the service notations tug and escort
tug defined in NR 467, Pt A, Ch 1, Sec 2.
Application of the recommended criteria of this Guidance
Note as alternative to the requirements of NR 467, Pt D, Ch 14
is subject to agreement by the Society on a case by case basis.
2
Introduction
2.1
General
2.1.1 Tugs are considered to be ships specially equipped
for towing and/or pushing other (generally larger) ships
and/or floating offshore units. Both the tasks assigned to
tugs as well as the operational profiles show a broad variation. Therefore, differences between tugs can be very significant in terms of general arrangement design, hull lines,
structural reinforcements, machinery and electrical systems,
deck and towing equipment and safety systems.
2.1.2 In order to provide the industry with adequate guidelines and rules, the class requirements for tugs should take
this variation into account. A logical way of doing so is to
define a set of different service notations for tugs, which
reflect the nature of operation of the tug as well as the operational profile. The class requirements for each type of tug are
then defined as a function of the selected service notation.
2.1.3 An overview of typical operational profiles for which
tugs are designed and equipped is provided in [2.2]. The
operational profile is to be considered as a combination of
the function (type of operation) and service (operating area)
of the tug.
July 2014
2.1.4 A general and indicative description of typical tug
design arrangements for towing and pushing operations is
provided in [2.3]. It is recognised that other, specialised tug
design arrangements exist in addition to the ones specified
in [2.3]. The guidelines are applicable to the specific design
arrangements mentioned in [2.3.1], [2.3.2] and [2.3.3], but
may also be applied to other design arrangements, as far as
deemed reasonable and practicable (refer to [2.4]).
2.2
2.2.1
Typical operational profiles
Harbour tugs
Harbour tugs are considered to be tugs specially equipped
to assist ships and/or floating offshore units while entering
or leaving port and during berthing and unberthing operations. Harbour tugs are considered to navigate in calm
stretches of water (sheltered area). Usually harbour tugs
work from a fixed port; the crew is familiar with the operating area and shore side facilities for maintenance, repairs,
spare parts, etc., are directly available. In case of emergency
shore side assistance is directly available.
2.2.2
Seagoing tugs
Seagoing tugs are considered to be tugs specially equipped
to assist ships and/or floating offshore units at sea, but may
also be involved in harbour towage operations. Seagoing
tugs can either operate without any restriction (deep sea
towage, in any sea area and any period of the year), within
short distance from shore (coastal towage), or at a specified
location (offshore terminal tugs). Salvage tugs are considered as seagoing tugs having specific equipment for salvage
operations.
For coastal towage and offshore terminal tugs the crew is
considered to be generally familiar with the operating area
and shore side facilities for maintenance, repairs, spare
parts, etc., are readily available. It is also considered that in
case of emergency shore side assistance is readily available
if the tug does not proceed in the course of the voyage more
than four hours at operational speed from a place of safe
sheltered anchorage.
For deep sea towage the crew is not necessarily familiar
with the operating area and shore side facilities for maintenance, repairs, spare parts, etc., are generally not readily
available. It is also considered that in case of emergency
shore side assistance is not readily available.
Salvage tugs, due to the nature of their operations, are to be
able to operate fully autonomously under all conditions.
Consequently, even if the crew may be familiar with the
operating area, it is considered that shore side facilities and
emergency assistance are not readily available.
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NI 617, Sec 1
2.2.3
2.4
Escort tugs
Escort tugs are considered to be tugs specially equipped for
escorting ships during navigation. Escorting is considered to
include active (emergency) steering, braking and otherwise
controlling of the assisted ship while approaching a port or
terminal, or, while navigating in confined waters. Typically
escorting involves indirect towage at speeds in excess of
6 kn. Escort tugs are considered to operate in open sea
areas and/or in sheltered (confined) waters (e.g. in ports).
If escort tugs operate from a fixed station, the crew is generally familiar with the operating area and shore side facilities
for maintenance, repairs, spare parts, etc. are readily available. It is considered that in case of emergency shore side
assistance is readily available if the escort tug does not proceed in the course of the voyage more than four hours at
operational speed from a place of safe sheltered anchorage.
2.3
2.3.1
Typical design arrangements
Conventional tugs
Conventional tugs have fixed single or multiple shaft
arrangement. The propeller(s) can be of fixed pitch or controllable pitch type, normally fitted with Kort nozzle(s).
Steering is done by means of rudder(s) or steerable nozzle(s). The towing point is normally located slightly aft of
the centre of lateral resistance for towing over the stern with
a towing hook and/or towing winch.
2.4.1 Other tug design arrangements, having towing and
propulsion configurations different from the design arrangements described in [2.3.1], [2.3.2] and [2.3.3], have been
developed and built:
• Reference is made to tugs, other than the tractor tugs
and ASD tugs as described in [2.3.2] and [2.3.3],
respectively, which are equipped with omnidirectional
thrusters installed at a single location along the length,
effectively mixing the characteristics of both design concepts.
The guidelines provide specific recommendations
regarding the anticipated effective towline forces acting
in the transverse direction and the associated heeling
moments in relation to the towing and/or escorting stability requirements.
• Reference is also made to tugs which are equipped with
multiple omnidirectional thrusters distributed along the
length. Such tugs have the capability to generate relatively high transverse thrust compared to tugs with
omnidirectional thrusters installed at a single location
along the length described above.
This aspect needs to be specially considered when
applying these Guidelines. Particular attention is to be
paid to the anticipated effective towline forces acting in
the transverse direction and the associated heeling
moments in relation to the towing and/or escorting stability requirements.
Conventional tugs may also be equipped to perform pushing operations.
3
2.3.2
3.1
Tractor tugs
Tractor tugs are fitted with omnidirectional thrusters (typically two steerable propellers or Voith-Schneider type
cycloidal propulsion units), which are located forward of
the towing point (usually not more than 30% of the length
from the forward end). A skeg or vertical fin is fitted aft.
Towing is performed over the stern with a towing winch
and/or towing hook.
Other design arrangements
General
Scope of application
3.1.1 These Guidelines is applicable to tugs having a (freeboard) length LLL, as defined in the International Convention
on Load Lines (ICLL) in force, of not more than 100 m and
to which one or more of the service notations specified in
[3.2] are assigned.
Tractor tugs may also be equipped to perform pushing operations.
3.1.2 These Guidelines may also be applied to other ships
engaged in towing, such as anchor handling tugs, anchor
handling tug supply vessels, salvage tugs and standby rescue vessels, as far as deemed practicable by the Society.
2.3.3
3.2
Azimuth Stern Drive tugs
Azimuth Stern Drive (ASD) tugs are fitted with multiple
steerable propellers located near the aft end. Typically, ASD
tugs can perform towing operations over the bow with the
forward towing winch (towing operation similar to a tractor
tug) and over the stern with a towing hook and/or second
towing winch (towing operation similar to a conventional
tug). In both cases the towing point is located forward of the
thrusters. ASD tugs may be fitted with a skeg, the size and
location depending on the intended function).
Azimuth Stern Drive tugs may also be equipped to perform
pushing operations.
8
Service notations and additional service
feature
3.2.1 On the basis of the typical operational profiles of
tugs, as described in [2.2], the following service notations
are defined:
• harbour tug for tugs specially equipped for towing
and/or pushing within the limits of a port,
• tug for tugs specially equipped for towing and/or pushing at sea, as well as in port
• escort tug for tugs specially equipped for escorting ships
during navigation.
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July 2014
NI 617, Sec 1
3.2.2 The service notations harbour tug and tug are to be
completed by the design performance limit as follows:
• (Bollard Pull = [TBP/9,81] t)
where TBP is defined in [4.1.1].
Note 1: In direct towing mode the trust is directly applied to generate the towline force, whereby hydrodynamic lift and drag forces
play no significant role.
Example: tug (Bollard Pull = 60 t)
3.2.3 The service notation escort tug is to be completed by
the design performance limits as follows:
• (maximum steering force = [TY,MAX/9,81] t, maximum
braking force = [TX,MAX/9.81] t, maximum escort speed
= [Vmax] kn)
where TY,MAX and TX,MAX are defined in [4.2.6], while VMAX is
defined in [4.2.4].
Example: escort tug (maximum steering force = 65 t, maximum braking force = 90 t, maximum escort speed = 10 kn)
3.2.4 The service notations tug and escort tug may be
completed by the following additional service feature:
• sailing time ≤ 4 h from a safe sheltered anchorage
for tugs which do not proceed in the course of their voyage
more than four hours at operational speed from a place of
refuge.
3.2.5 Multiple service notations may be assigned.
3.3
hydrodynamic lift and drag forces acting on the hull and
appendices of the tug advancing through the water at a drift
angle relative to the water flow, the thrust vector and the
towline force.
Specific considerations for escort tugs
3.3.1 For the purpose of these Guidelines escorting is considered to include active (emergency) steering, braking and
otherwise controlling of the escorted ship by the tug operating in indirect towing mode, whereby the ahead speed of
the escorted ship is within a typical speed range of 6 to
10 kn.
3.3.2 In indirect towing mode the towline force is the
resulting from the (quasi-static) equilibrium condition
reached between the forces and moments arising from the
3.3.3 Escort tugs may work in different indirect towing
modes, depending on the required action towards the
escorted ship (e.g. steering, braking). The main indirect towing modes relevant for escort tugs are schematically shown
in Fig 1.
Where reference is made to “indirect steering” the objective
is to maximise the steering force in indirect towing mode.
Where reference is made to “indirect braking” the objective
is to maximise the braking force in indirect towing mode.
3.3.4 In (basic) indirect mode the towline force is generated primarily by the hydrodynamic forces acting on the
hull and skeg, with the thrust used solely to maintain the
desired drift angle (also referred to as yaw angle).
3.3.5 In powered indirect mode (indirect steering) the
transverse component of thrust is used to maintain the
desired drift angle, while a significant longitudinal component of thrust is applied in forward direction of the tug.
Compared to the (basic) indirect mode, the tug is operating
more sideways of the escorted ship with a relatively large
towline angle, generating a higher steering force.
3.3.6 In combination mode (indirect braking) the same
principle as for the indirect steering mode is applied, except
that the longitudinal component of thrust is applied in aftward rather than forward direction.
Compared to the (basic) indirect mode, the tug is operating
more behind the escorted ship with a relatively small towline angle, generating a higher braking force.
Figure 1 : Schematic overview of indirect towing modes (escort tug)
July 2014
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NI 617, Sec 1
3.3.7 For indirect towing modes it is recommended to
design the tug to generate high (indirect) towline forces with
minimal propulsion thrust, while respecting the limits
imposed by stability and strength considerations (towing
equipment, general hull structure).
Figure 2 : Typical escort configuration
3.3.8 The propulsion engines are to ensure sufficient thrust
for manoeuvring the tug quickly for any drift angle (refer to
angle β as defined in [4.2.2]).
3.3.9 In the case of loss of propulsion, the heeling moment
due to the remaining forces is to lead to a safe equilibrium
position of the tug with reduced heeling angle.
4
Definitions
4.1
Bollard Pull
4.1.1 The Bollard Pull TBP, in kN, is the maximum sustained
towline force the tug is capable of generating at zero forward speed, to be initially specified by the Designer and to
be verified by a full scale test, generally referred to as Bollard Pull test.
4.1.2 The Bollard Pull is to be verified by means of a Bollard Pull test performed in accordance with a recognised
standard.
For tugs capable of towing over the stern (ahead towing) as
well as over the bow (astern towing), the Bollard Pull test is
to be performed for towing over the stern (ahead towing)
and for towing over the bow (astern towing).
The maximum measured Bollard Pull is to be referenced in
the service notation, see [3.2].
4.1.3 Where the value of the Bollard Pull is not provided,
the following default values may be used for preliminary
design review:
• TBP = 0,204 N PS
for conventional tugs with propellers fitted with nozzles;
• TBP = 0,176 N PS
for tractor tugs and ASD tugs with steerable propellers
fitted with nozzles.
where:
N
: Number of propellers
PS
: Maximum continuous power per propeller
shaft, in kW.
4.2
Escort forces and speed
4.2.1 The steady towline force during escorting, TESC, in kN,
is the towline force associated with the considered (quasistatic) equilibrium in indirect towing mode, excluding short
time-duration dynamic effects, for a given loading condition
and escort speed V, see Fig 2. The steady towline force is
applied by the tug on the stern of the escorted ship.
10
4.2.2 The following angles are defined in relation to escort
operations (see Fig 2):
• The towline angle α, in deg, is the angle between the
towline and the centreline of the escorted ship, and
• The drift angle β, in deg, is the angle between the centreline of the tug and the centreline of the escorted ship
(also referred to as yaw angle).
4.2.3 The steady towline force TESC can be decomposed
into a steering force TY and a braking force TX (see Fig 2):
• The steering force TY, in kN, is the transverse component of the steady towline force TESC with respect to the
escorted ship
• The braking force TX, in kN, is the longitudinal component of the steady towline force TESC with respect to the
escorted ship.
4.2.4 The maximum escort speed VMAX, in kn, is the highest
escort speed V for which the escort tug is considered to perform escort operations, to be specified by the Designer and
not to be taken higher than 10 kn.
Note 1: For high powered escort tugs with a free running speed of
more than 15 kn the Society may, on a case-by-case basis, accept a
maximum escort speed of 12 kn.
4.2.5 For the purpose of these Guidelines the following
rated values of the above defined escort forces are specified:
• The rated steady towline force TESC,R, in kN, is the highest anticipated steady towline force TESC, as obtained
from the evaluation of the escort forces for a particular
loading condition and escort speed, taking into account
the applicable stability and strength criteria of these
Guidelines
• The rated steering force TY,R, in kN, is the m highest
anticipated steering force TY, as obtained from the evaluation of the escort forces for a particular loading condition and escort speed, taking into account the
applicable stability and strength criteria of these Guidelines
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July 2014
NI 617, Sec 1
• The rated maximum braking force TX,R, in kN, is the
highest anticipated braking force TX, as obtained from
the evaluation of the escort forces for a particular loading condition and escort speed, taking into account the
applicable stability and strength criteria of these Guidelines.
4.3
4.2.6 For the purpose of these Guidelines the following
maximum values of the above defined rated escort forces
are specified:
• The maximum steady towline force TESC,MAX, in kN, is the
highest rated steady towline force TESC,R over the applicable range of loading conditions and escort speeds
• The maximum steering force TY,MAX, in kN, is the m highest rated steering force TY,R over the applicable range of
loading conditions and escort speeds
• The maximum braking force TX,MAX, in kN, is the m highest rated braking force TX,R over the applicable range of
loading conditions and escort speeds.
• the maximum steady towline force TESC,MAX for service
notation escort tug, see [4.2].
4.2.7 The matrix of rated steady towline forces TESC,R, steering forces TY,R and braking forces TX,R is to be initially specified by the Designer and to be verified by the Society on the
basis of the results of:
• full scale trials, or
• model testing, or
• a computer simulation programme accepted by the
Society.
4.2.8 Full scale trials, where applicable, should be performed in accordance with a procedure agreed with the
Society before prior to commencement of the trials and
comply with the requirements of Sec 2, [3.6].
4.2.9 Model testing, where applicable, should be performed in accordance with a procedure agreed with the
Society before prior to commencement of the tests and
comply with the requirements of Sec 2, [3.6]. Special attention is to be paid to scale effects when processing the measurement result to create predictions at full scale.
4.2.10 Computer simulation programmes for predicting
escort performance are to comply with the requirements of
Sec 2, [3.5].
July 2014
Reference towline force
4.3.1 The reference (quasi-static) towline force T, in kN, is
considered to represent:
• the Bollard Pull TBP for service notations harbour tug
and tug, see [4.1]
4.4
Design Load
4.4.1 The Design Load DL, in kN, is the force taken into
consideration for the strength assessment and testing of the
towing equipment and the associated supporting structures,
and is to be taken as not less than:
DL = DAF T
where,
DAF
: Dynamic Amplification Factor
The DAF takes into consideration dynamic effects. Reference values for the DAF are given in Sec 3, [1.3] for service
notations harbour tug and tug, and in Sec 3, [2.3] for service notation escort tug.
4.5
Winch Brake Holding Load
4.5.1 The winch Brake Holding Load BHL, in kN, is the
maximum towline force the towing winch can withstand
without slipping of the (activated) brake, considering the
towline at the first layer.
4.5.2 The BHL is a reference for the strength assessment
and testing of towing winches and associated towing fittings
(e.g. fairlead, staple, gob-eye) as well as their supporting
structures.
4.6
Towline breaking strength
4.6.1 The towline breaking strength, in kN, is the tension
required to cause failure of the towline (parting of the towline).
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11
NI 617, Sec 2
SECTION 2
1
1.1
STABILITY
General
3
Scope of application
Intact stability
3.1
1.1.1 All tugs having a Load Line length LLL equal to or
greater than 24 m may be assigned class only after it has
been demonstrated that their intact stability is adequate.
Adequate intact stability means compliance with standards
laid down by the relevant Administration or with the
requirements specified in this section taking into account
the tug’s size and type.
3.1.1
Loading conditions
Standard loading conditions
Standard loading conditions are to be included in the stability booklet:
• lightship condition
• tug in lightest anticipated loading condition, with full
stores and fuel
In any case, the level of intact stability is not to be less than
that provided by the Guidelines.
• same condition as above, but with 10% stores, provisions and consumables
1.1.2 The Guidelines also apply to tugs with a load line
length LLL of less than 24 m in length.
• tug in the departure condition at the waterline corresponding to the maximum draught, with full stores, provisions and consumables
2
Openings
• same condition as above, but with 10% stores, provisions and consumables.
General
For the lightship condition, not being an operational loading condition, the Society may accept that part of the mentioned criteria is not fulfilled.
2.1
2.1.1 Openings in the hull, superstructures or deckhouses
which cannot be closed weathertight are to be considered
as unprotected openings and, consequently, as down-flooding points for the purpose of stability calculations (the lower
edge of such openings is to be taken into account).
2.2
3.1.3 When a tropical freeboard is to be assigned to the
tug, the corresponding loading conditions are also to be
included.
Ventilation openings of machinery
space and emergency generator room
2.2.1 It is recognised that for tugs, due to their size and
arrangement, compliance with the requirements of ICLL
Reg. 17(3) for ventilators necessary to continuously supply
the machinery space and the emergency generator room
may not be practicable. Lesser heights of the coamings of
these particular openings may be accepted if the openings:
• are positioned as close to the centreline and as high
above the deck as practicable in order to maximise the
down-flooding angle and to minimise exposure to green
water
• are provided with weathertight closing appliances in
combination with suitable arrangements, such as separators fitted with drains
• are equipped with efficient protective louvers and mist
eliminators
• have a coaming height of not less than 900 mm above
the deck
• are considered as unprotected openings and, consequently, as down-flooding points for the purpose of stability calculations.
12
3.1.2 In case a tug is fitted with water ballast tanks the
lightest anticipated loading condition may be a ballast condition (in particular for larger tugs).
3.1.4 For the loading condition corresponding to the maximum draught, when necessary, deck cargo may be applied
to arrive at the required draught. Attention is to be paid to
the associated wind profile for verification of the severe
wind and rolling criterion, refer to part A, 2.3 of the International Code on Intact Stability, 2008.
3.1.5
Additional loading conditions to be included
in the stability booklet
Additional loading conditions are to be included in the stability booklet:
• tug in the worst anticipated operating conditions for
towing, covering the relevant range of draughts, for service notations harbour tug and tug
• tug in the worst anticipated operating conditions for
escorting, covering the relevant range of draughts, for
service notation escort tug.
Further loading conditions may be included when deemed
necessary or useful.
Bureau Veritas
July 2014
NI 617, Sec 2
3.2
Stability criteria
3.2.1 The intact stability of tugs should comply with the
provisions given in part A, 2.2 and 2.3 of the International
Code on Intact Stability, 2008, except that the alternative
criteria given in part B, 2.4.5, which apply to offshore supply vessels, may be used for tugs of similar design and characteristics.
3.2.2 With reference to Part B, 5.1.4 of the International
Code on Intact Stability, 2008, tugs should possess an adequate reserve of stability to withstand the anticipated heeling moment arising from the towline. It is considered that
this requirement is complied with in case a tug meets the
additional stability criteria as specified in [3.3] and/or [3.4],
as applicable.
3.3
Additional stability criteria for service
notations harbour tug and tug
3.3.6 A harbour tug or tug may be considered as having
sufficient stability to withstand the heeling moment arising
from the towline if the following condition is complied with
(see Fig 1):
A≥B
where:
A
: Area, in m.rad, contained between the righting
arm and the heeling arm curves, measured from
the heeling angle θC to the heeling angle θD
B
: Area, in m.rad, contained between the heeling
arm and the righting arm curves, measured from
zero heel (θ = 0) to the heeling angle θC
θC
: Heeling angle of equilibrium, corresponding to
the first intersection between heeling and righting arm curves
θD
: Heeling angle, to be taken as the lesser of:
• heeling angle corresponding to the second
intersection between heeling and righting
arms heeling and righting arm curves
3.3.1 All the loading conditions reported in the trim and
stability booklet which are intended for towing operations
are also to be checked in order to investigate the tug’s capability to withstand the effect of the transverse heeling
moment induced by the combined action of the towline
force and the thrust vector.
• angle of downflooding.
Figure 1 : Heeling and righting arm curves
3.3.2 The stability calculations are to be performed on the
basis of the Bollard Pull, as defined in Sec 1, [4.1].
3.3.3 For tugs capable of towing over the stern as well as
over the bow, this check is to be performed for both towing
situations, duly taking into account the location of the associated towing points. If different values of the ahead and
astern Bollard Pull are available, it is acceptable to consider
the ahead Bollard Pull for towing over the stern and the
astern Bollard Pull for towing over the bow.
3.3.4 The values of the ahead and astern Bollard Pull, as
applicable, are to be specified by the Designer in the stability booklet. In addition, an arrangement drawing with the
location of the towing point(s) and propulsion unit(s) is to
be included in the stability booklet. In this drawing the longitudinal and vertical distance, in m, from each of the towing points to the relevant centrelines of the propulsion
unit(s) and the baseline, respectively, are to be specified.
T BP hc
- cos θ
b H = ---------------9, 81 Δ
where:
bH
: Heeling arm, in m
TBP
: Bollard Pull, in kN, as relevant for the considered towing situation
h
: Vertical distance, in m, between the towing
point (fairlead, staple, towing hook or equivalent fitting) and the horizontal centreline of the
propulsion unit(s), as relevant for the considered
towing situation
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13
3.3.5 Preliminary stability calculations on the basis of estimated Bollard Pull values may be submitted for (preliminary) examination. If after completion of the Bollard Pull
test the measured Bollard Pull values exceed the estimated
values, the stability calculations have to be updated for the
measured Bollard Pull values. It is recommended to include
a reasonable margin in the estimated values (on the basis of
design experience).
July 2014
3.3.7 The heeling arm curve is to be calculated as follows:
NI 617, Sec 2
c
: Coefficient to be taken equal to:
• c = 0,50 for tugs with non-azimuth propulsion (conventional tug, see Sec 1, [2.3.1])
• c = 0,90 / (1 + d / LLL) for tugs with azimuthing thrusters installed at a single point along
the length (tractor tug and ASD tug, see Sec
1, [2.3.2] and Sec 1, [2.3.3], respectively, as
well as similar tug designs), as relevant for
the considered towing situation, but is in no
case to be taken as less than 0,70 for ASD
tugs towing over the stern and tractor tugs
towing over the bow and 0,50 for ASD tugs
towing over the bow and tractor tugs towing
over the stern, respectively
Δ
: Loading condition displacement, in t
θ
: Angle of heel, in deg
d
: Longitudinal distance, in m, between the towing point (fairlead, staple, towing hook or equivalent fitting) and the vertical centreline of the
propulsion unit(s), as relevant for the considered
towing situation.
3.4.5 The value of the highest anticipated heeling moment
is to be specified by the Designer in the stability calculations. In addition, an arrangement drawing with the location of the towing points and propulsion units is to be
included in the stability booklet. In this drawing the longitudinal and vertical distance, in m, from the towing point to
the relevant centrelines of the propulsion units and the
baseline, respectively, are to be specified.
3.4.6 Preliminary stability calculations on the basis of estimated highest heeling moment and associated heeling arm
values may be submitted for (preliminary) examination. If
after verification of the heeling arm values on the basis of
the results of escort performance trials, model tests or a
computer simulation programme accepted by the Society
(refer to [3.5]) the final values exceed the estimated values,
the stability calculations have to be updated for the final
heeling moment and heeling arm values. It is recommended
to include a reasonable margin in the estimated values (on
the basis of design experience).
3.4.7 An escort tug may be considered as having sufficient
stability to withstand the heeling moment arising from the
towline, if the three following conditions are complied
with:
A ≥ 1,25 B
3.4
Additional stability criteria for service
notation escort tug
C ≥ 1,40 D
θC ≤ 15 deg
3.4.1 All the loading conditions reported in the trim and stability booklet which are intended for escorting operations are
also to be checked in order to investigate the tug’s capability
to withstand the effect of the transverse heeling moment
induced by the combined action of the following forces:
• hydrodynamic forces acting on the hull and appendices
where:
A
: Righting arm curve area, in m.rad, measured
from the heeling angle θC to a heeling angle of
20 deg (see Fig 2)
B
: Heeling arm curve area, in m.rad, measured
from the heeling angle θC to a heeling angle 20
deg (see Fig 2)
C
: Righting arm curve area, in m.rad, measured
from the zero heel (θ = 0) to the heeling angle
θD (see Fig 3)
D
: Heeling arm curve area, in m.rad, measured
from zero heel (θ = 0) to the heeling angle θD
(see Fig 3)
θC
: Heeling angle of equilibrium corresponding to
the first intersection between heeling arm and
righting arm curve, to be obtained when the
highest anticipated heeling moment resulting
from the steady towline force TESC as defined in
Sec 1, Fig 2, is applied to the escort tug.
θD
: Heeling angle, to be taken as the lesser of:
• thrust forces
• steady towline force.
3.4.2 The stability calculations are to be performed on the
basis of the highest anticipated heeling moment for the considered loading condition, which is to be obtained from the
results of full scale tests, model tests, or, alternatively, the
results of a computer simulation programme accepted by
the Society (refer to [3.5]).
3.4.3 For each relevant loading condition the evaluation of
the highest anticipated heeling moment is to be performed for
the applicable range of speeds and towline angles, as defined
in the escort towing arrangement plan (see Sec 3, [2.2]). As a
minimum, the conditions corresponding to the highest rated
steering force, TY,R, and highest rated braking force, TX,R, as
defined in Sec 1, [4.2], are to be included in the evaluation.
3.4.4 The highest anticipated heeling moment is to be
assumed constant for the purpose of the stability calculations.
14
Bureau Veritas
• the angle of down-flooding
• 40 deg
• the heeling angle corresponding to the second intersection between heeling and righting arms heeling and righting arm curves.
July 2014
NI 617, Sec 2
Figure 3 : Definition of areas C and D
Figure 2 : Definition of areas A and B
3.5
Escort performance simulations
3.5.1 Where the highest anticipated heeling moment is
obtained from the results of a computer simulation programme, the basic assumptions and theoretical models
underlying the software are to be presented in detail to the
Society. Items to be addressed include:
• hydrodynamic lift and drag computation (hull and
appendices)
• Rated steering force TY,R or steering force TY corresponding to rated braking force TX,R, as applicable
• Rated braking force TX,R or braking force TX corresponding to rated steering force TY,R, as applicable
• Corresponding towline force TESC
• modelling of thrust forces
• interaction effects between hull, skeg and (steerable)
propulsion units
• All corresponding forces acting in transverse direction
(hydrodynamic, thrust and towline)
• Corresponding heeling angle
• flow separation effects
• Corresponding heeling moment
• water pile-up effects
• Corresponding towline angle relative to the escorted
ship (refer to α in Sec 1, Fig 2);
• effects of waves and/or swell
• dynamic effects before a steady state is reached (e.g.
during initiation and turning manoeuvres) and scaling
effects (if any).
3.5.2 A validation report, containing comparisons between
simulation results and full scale and/or model test results, is
to be presented to the Society.
3.5.3 A clear description of the input and output data is to
be provided, along with explanations on how the output
data are obtained/calculated by the software.
July 2014
3.5.4 As a minimum, for each relevant loading condition
(see [3.4]) the following set of results is to be provided in
tabular form as function of the escort speed for the rated
values of the steering force TY,R and the braking force TX,R:
• Corresponding drift angle of the escort tug (refer to β in
Sec 1, Fig 2).
Note 1: The highest anticipated values of the steering force, braking
force, towline force and heeling moment do not normally all occur
in the same condition (defined by the position of escort tug relative
to the escorted ship and the drift angle), although more than one
parameter may have its highest value in a particular condition.
Hence it is necessary to consider at least two conditions: one for
the highest anticipated steering force and one for the highest anticipated braking force. In case the highest anticipated heeling
moment and/or towline force do not occur in either one of these
two conditions, the relevant conditions are to be added.
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15
NI 617, Sec 2
3.5.5 It is recommended that the results of the escort performance simulations are presented in the form of diagrams
showing the envelope of the (steady state) combinations of
steering and braking forces obtained from the simulations.
Such diagrams should cover the applicable escort speed
range, with a recommended step of 2 kn.
3.6
Escort performance trials
3.6.1 Escort performance trials at full scale or model scale
may be carried out in order to obtain the characteristics of
escort tugs defined in Sec 1, [4.2].
3.6.2 The trials are to cover the applicable range of loading
conditions and escort speeds.
3.6.3 The following documents are to be submitted for
information prior to testing:
• Relevant loading conditions, defined by draught (or displacement) and trim, for which the tug is designed to
perform escort services
• Applicable range of test speeds of the escorted ship: the
speed is defined as the relative speed with respect to the
sea, taking into account current effects
• Main propulsion characteristics, in particular power and
maximum orientation angle of the rudder(s) (propellers);
• Preliminary calculation of the rated steering force TY,R,
rated braking force TX,R and rated steady towline force
TESC,R as defined in Sec 1, [4.2], as well as the corresponding heeling moments and heeling angles, for the
range of test speeds
3.6.6 As a minimum, the following data is to be collected
during testing for post-processing and analysis:
• Towline force (tension) TESC
•
•
•
•
Towline angle α, as defined in Sec 1, Fig 2
Drift angle β, as defined in Sec 1, Fig 2
Heeling angle of the escort tug
Towline length and angle of towline with the horizontal
plane.
3.6.7 It is also recommended to measure the following
data:
• Power setting and orientation angle of rudder(s) (propellers) of the escort tug
• Time needed to perform swing the tug from the equilibrium position to its mirror position (see Sec 1, Fig 2).
3.6.8 For each combination of loading condition and test
speed:
• The rated steering force TY,R and rated braking force TX,R
and are to be calculated on the basis of the corresponding measured steady towline force TESC and the associated measured towline angle, drift angle and the angle
between the towline and the horizontal plane
• The maximum heeling arm is to be calculated on the
basis of the corresponding measured steady towline
force TESC, as defined in Sec 1, [4.2], the associated
measured heeling angle and the GZ curve applicable to
the loading condition considered.
Note 1: The GZ curve is to be based on the escort tug in upright
position before commencing the escort operation
• Calculation of the route deviation of the escorted ship
(for testing purposes the escorted ship is to be selected
so that the route deviation induced by the tug is kept
reasonably small
3.6.9 As a minimum, for each tested loading condition the
following set of results is to be provided in tabular form as
function of the escort speed for the rated values of the steering force TY,R and the braking force TX,R:
• Preliminary stability calculations for the above mentioned conditions
• Rated steering force TY,R or steering force TY corresponding to rated braking force TX,R, as applicable
• Escort towing arrangement plan, including the load cell
and specification of the components
• Rated braking force TX,R or braking force TX corresponding to rated steering force TY,R, as applicable
• Documentation relevant to the Bollard Pull test, see Sec
1, [4.1].
3.6.4 Prior to commencing the escort performance trials
the following data are to be recorded:
• Wind speed and direction
• Sea state, including significant wave height and peak
period
• Current speed and direction
• Water depth
• Loading condition of the escort tug: draught (or displacement) and trim
• Loading condition of the escorted ship.
3.6.5 Testing is to be performed over the applicable range
of towline angles as defined in the escort towing arrangement plan. The length of the towline and the angle of the
towline with the horizontal plane are is to represent a typical operating condition.
16
• Corresponding towline force TESC,R
• Corresponding heeling angle
• Corresponding heeling moment
• Corresponding towline angle relative to the escorted
ship (refer to α in Sec 1, Fig 2)
• Corresponding drift angle of the escort tug (refer to β in
Sec 1, Fig 2).
Note 1: The highest anticipated values of the steering force, braking
force, towline force and heeling moment do not normally all occur
in the same condition (defined by the position of escort tug relative
to the escorted ship and the drift angle), although more than one
parameter may have its highest value in a particular condition.
Hence it is necessary to consider at least two conditions: one for
the highest anticipated steering force and one for the highest anticipated braking force. In case the highest anticipated heeling
moment and/or towline force do not occur in either one of these
two conditions, the relevant conditions are to be added.
3.6.10 For model testing due consideration is to be paid to
scale effects for establishing the escort tug characteristics at
full scale from the model test results.
Bureau Veritas
July 2014
NI 617, Sec 2
3.7
Operating information for service notation escort tug
3.8
3.7.1 Additional operating information is to be provided in
the stability booklet in relation to the design limitations
related to the assignment of the service notation escort tug .
Note 1: Reference is made to Pt B, Ch 3.8 of the International Code
on Intact Stability, 2008.
3.7.2 As a minimum, the following information is to be
included:
• Design operating area and environmental conditions for
performing escort operations (refer to Sec 1, [2.2.3])
• The maximum escort speed VMAX (refer to Sec 1, [4.2])
• A table with permissible values of heeling angle and
steady towline force as function of loading condition
and escort speed (based on the rated steering and braking forces as obtained from [3.5] or [3.6], as applicable)
• Instructions to the master regarding the handling of the
escort tug and the associated towing equipment, demonstrating the implementation of effective means to limiting the steady towline force and heeling angle within
the permissible limits and the use of the emergency
quick-release device.
Note 1: Adjustable audible or visible alarms, providing a warning
to the master when the heeling angle and/or steady towline force
exceeds the permissible value(s) applicable to the relevant loading
condition and escort speed, in combination with appropriate handling instructions are as effective means.
3.7.3 The table with permissible values of heeling angle
and steady towline force as function of loading condition
and escort speed is to be displayed in the wheelhouse next
to the control desk or another appropriate location.
July 2014
Icing considerations
3.8.1 For tugs operating in areas where ice accretion is
expected due consideration is to be given to the stability
affecting effect of added weight due to ice accretion.
To this end relevant loading conditions, including ice accretion are to be included in the stability booklet, together with
detailed calculations of the expected ice accretion.
Note 1: Reference is made to Pt B, Ch 6 of the International Code
on Intact Stability, 2008.
3.9
Elements reducing stability
3.9.1 Provisions are to be made for a safe margin of stability at all stages of the voyage, regard being given to additions of weight, such as those due to absorption of water
and icing and to losses of weight such as those due to consumption of fuel and stores.
3.10 Alterations
3.10.1 Where any alterations are made to a tug or its towing equipment so as to materially affect the stability information supplied to the master, amended stability
information shall be provided.
Note 1: While in service life it may be considered to carry out
(periodical) lightweight surveys to verify any changes in lightship
displacement and longitudinal centre of gravity. In case significant
deviations are found in comparison with the approved stability
information, it may be necessary to (re-)incline the tug.
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NI 617, Sec 3
SECTION 3
1
1.1
TOWING EQUIPMENT
• Design load of towing hook and towline guiding fittings
Towing equipment for service
notations harbour tug and tug
• Design calculations of the towline guiding fittings and
the supporting structures of towing equipment, including detailed analysis reports in case three dimensional
finite element models have been used.
General
1.1.1 Towing winches, towing hooks and towline guiding
fittings (fairleads, staples, gob-eyes, towing pins, etc.) are
normally to be arranged in way of the tug’s centreline, in
such a position as to minimise heeling moment exerted by
the towline force.
Effective means are to be provided to lead and restrain the
towline within the designed limits of its sweep.
1.1.2 Materials used in towing equipment are to comply
with the applicable class requirements for materials. Class
certificates are required for the materials used for winch
drums, drum shafts, winch brake components, winch supporting frames, towing hooks and towline guiding fittings.
1.2.2 The following documents are to be submitted for
approval:
• Detailed drawings of towing winches, including winch
drums, main shaft, load carrying non-rotating structures
(support frame), winch brakes, gears and clutches
• Hydraulic, electrical and control system diagrams of the
towing winch, as applicable
• Detailed drawings of towing hook and towline guiding
fittings
• Supporting structures of towing equipment.
1.3
Design Load
1.1.3 Reliable emergency quick-release arrangements,
capable of releasing the towline under the maximum anticipated load regardless of the angle of the towline and the
tug’s trim and heel, are to be provided.
1.3.1 The Design Load DL to be considered for the strength
assessment of the towing equipment and the associated
supporting structures is given in Tab 1.
The emergency quick-release devices shall be operable in
case of failure of the main power supply.
Table 1 : Design Loads for harbour tug and tug
1.2
Documents to be submitted
1.2.1 The following documents are to be submitted for
information:
• Towing arrangement plan, showing the location and
general lay-out of the towing equipment, the range of
anticipated lines of action of the towlines with the associated maximum steady towline forces and the corresponding points of application of the towline forces on
the towing equipment
Note 1: The steady towline force is the towline force without
dynamic amplification effects (also called quasi-static towline
force).
• Detail arrangement drawings of towing winches, towing
hooks and towline guiding fittings (fairleads, staples,
gob-eyes, towing pins, stern roller, etc.)
• Design information of towing winches, including maximum rated line pull, winch brake holding force, rendering load and specification of emergency quick-release
arrangements
• Design calculations of towing winches, including winch
drums, main shaft, load carrying non-rotating structures
(support frame) and braking capacity
18
Harbour tug
Tug
TBP [kN]
DL [kN]
T ≤ 200
2T
200 < T < 800
2600 – T
---------------------- T
1200
T ≥ 800
1,5 T
T ≤ 400
2,5 T
400 < T < 1000
3400 – T
---------------------- T
1200
T ≥ 1000
2T
Note 1: The DL takes into consideration dynamic effects
through the application of the Dynamic Amplification Factor
(DAF) (see also Sec 1, [4.4]).
1.4
Design requirements for towing winches
1.4.1 The winch brake shall normally act directly on the
drum and shall be operable in case of failure in the primary
power supply system (either manually or otherwise
arranged).
1.4.2 The towline attachment to the winch drum shall be
provided by means of a weak link or equivalent.
Bureau Veritas
July 2014
NI 617, Sec 3
1.4.3 Towing winches shall be provided with an emergency quick-release device operable from a position on the
bridge with full view and control of the towing operation.
Means of control for the emergency quick-release device
shall be protected against unintentional use.
The time delay between the initiation and actual start of the
emergency quick-release (pay-out of the towline) should be
as short as reasonably practicable.
The speed of paying out shall be such that the tension in the
towline is reduced as fast as reasonably possible, taking into
consideration that paying out is to be done in a controlled
manner. Spinning (free, uncontrolled rotation) of the winch
drum is to be avoided, as this could cause the towline to get
stuck and disable the release function of the winch.
1.4.4 After a quick-release event the winch brakes shall
directly be able to operate normally (automatically), while
the winch motor shall be engaged manually (not automatically).
The applicable procedures for the emergency quick-release
device, including time delays and release speed, shall be
communicated to the crew and vital information shall be
displayed next to the control desk or another appropriate
location.
1.4.5 The dimensioning of the winch drum is to take into
account the rope bending specifications provided by the
towline manufacturer.
Due consideration is to be given to the proper spooling of
the towline on the winch drum, as well as preventing the
towline to slip over the flanges of the drum.
1.4.6 Towing winches (in particular the components which
are exposed to the tension in the towline, such as the winch
drums, drum shafts, brakes, support frame and connection
to the hull structure) shall be able to:
• sustain the DL, as specified in [1.3] without permanent
deformation, and
• sustain the BHL, as defined in Sec 1, [4.5], without
exceeding an equivalent stress level (based on Von
Mises criterion) of 0,80 ReH.
where:
ReH
: Minimum specified yield stress of material,
in N/mm2.
1.4.7 Where deemed necessary by the Society, buckling
and/or fatigue analysis, performed in accordance with a
standard or code of practice recognised by the Society, may
be required to be submitted for information.
1.4.8 Towing winches may be equipped with an active payout and haul-in system automatic adjustment of towline. In
that case the relevant requirements of [2.4] and [2.8] are to
be complied with.
1.4.9 It is recommended that the towing winch should be
fitted with equipment to continuously measure the tension
in the towline.
In case a towline measurement system is installed on board,
the measured data are to be displayed in the wheelhouse
next to the control desk or another appropriate location.
July 2014
1.5
Design requirements for towing hooks
1.5.1 Towing hooks and their load carrying attachments
(connecting the towing hook to the hull structure) shall be
able to sustain the DL, as specified in [1.3], without exceeding an equivalent stress level (based on Von Mises criterion)
of 0,80 ReH.
Towing hooks shall be provided with an emergency quickrelease device operable from a position on the bridge with
full view and control of the towing operation, as well as at a
location near the hook where the device can be safely operated. Identical means of control for the emergency quickrelease devices shall be provided at each control station
and are to be protected against unintentional use.
The force necessary to open the hook under load is to be
not greater than 150 N.
The applicable procedures for the emergency quick-release
device shall be communicated to the crew and vital information shall be displayed next to the control desk or
another appropriate location.
1.6
Design requirements for towlines
1.6.1 The breaking strength of towlines is not to be less
than the DL, as specified in [1.3].
In addition, the breaking strength of towlines used on a towing winch is not to be less than the BHL of the associated
winch (see Sec 1, [4.5]).
The towline shall be protected from being damaged by
chafing and abrasion. To this end cargo rails, bulwarks, and
other elements, supporting the towline should be sufficiently rounded with consideration to the bend radius limit
of the towline in order to ensure that the towline breaking
strength is maintained.
It is recommended that the total length of the towline
applied on a towing winch is to be such that under normal
operation at least half a layer remains on the drum. In no
case less than three turns shall remain on the drum in under
normal operation.
1.7
Design requirements for towline guiding
fittings
1.7.1 Towline guiding fittings, such as fairleads, staples,
gob-eyes, towing pins, stern rollers and equivalent components which guide the towline, shall be able to sustain the
force exerted by the towline loaded under a tension equal
to the DL, as specified in [1.3], in the most unfavourable
anticipated position of the towline without exceeding the
following stress level criteria:
• Normal stress σ ≤ 0,75 Rref
• Shear stress τ ≤ 0,47 Rref
• Equivalent stress σVM ≤ 0,85 Rref
where:
: Reference stress of the material, in N/mm2, norRref
mally to be taken as 235/k, but may be taken as
ReH for fittings not made of welded construction.
k
: Material factor, defined as function of the minimum guaranteed yield stress ReH, see Tab 2.
Bureau Veritas
19
NI 617, Sec 3
1.9
Table 2 : Material factor k
ReH, in N/mm2
k
235
1
315
0,78
355
0,72
390
0,68
1.9.1 A robust and efficient fendering system is to be fitted
in areas intended for pushing. The fendering system purpose is to distribute the pushing force and limit its dynamic
component on the hull structure of both the tug (and the
assisted ship).
1.7.2 Towline guiding fittings used for guiding the towline
when towing on a towing winch shall be able to sustain the
force exerted by the towline loaded under a tension equal
to the BHL of the associated winch, as specified in Sec 1,
[4.5], in the most unfavourable anticipated position of the
towline without exceeding the above mentioned stress level
criteria.
1.7.3 Where a towline guiding fitting (e.g. fairlead or guide
pin) has been designed for a specific Safe Working Load
SWL, defined as the maximum static working load, the fitting shall be able to sustain a force equal to 2 times the SWL
without exceeding the above mentioned the above mentioned stress level criteria.
1.7.4 In case the yielding check of the towline guiding fittings is carried out by means of a three dimensional finite
element model, the permissible stress levels given above
may be increased by 10 per cent (compared to a beam
model).
1.8
Within the context of these guidelines it is considered that
during pushing operations the contact between the tug and
assisted ship is maintained and that no bouncing (e.g. under
wave action) is taking place. Forces resulting from bouncing
loads are not taken into consideration, as it is understood
that pushing operations (in waves) are normally halted
when bouncing starts taking place (due to operational difficulties to keep position within the pushing area of the
assisted ship as well as to control the associated impact type
loads).
1.9.2 The Design Load DL to be considered for the strength
assessment of the fender supporting structure may be taken
as follows:
DL = 1,5 TBP
TBP
1.8.1 The supporting structures of towing equipment shall
be able to sustain the load exerted on the supporting structure under the action of the towline loaded under a tension
equal to the DL, as specified in [1.3], in the most unfavourable anticipated position of the towline, without exceeding
the stress level criteria specified in [1.7].
1.8.2 Supporting structures of towing equipment engaged
when towing on a towing winch shall be able to sustain the
load exerted on the supporting structure under the action of
the towline loaded under a tension equal to the BHL of the
associated winch, as specified in Sec 1, [4.5], in the most
unfavourable anticipated position of the towline without
exceeding the stress level criteria specified in [1.7].
1.8.3 Where a towline guiding fitting has been designed for
a specific Safe Working Load SWL, defined as the maximum static working load, the associated supporting structure shall be able to sustain a force equal to 2 times the
SWL without exceeding the stress level criteria specified in
[1.7].
20
The design of the fendering system, in particular the contact
area and stiffness distribution, is to result in an acceptable
pressure distribution on the supporting structure of the tug
(and the assisted ship) under the maximum anticipated
loads during pushing operations.
where:
Design requirements for towing equipment supporting structures
1.8.4 In case the yielding check of the
supporting structures is carried out by
dimensional finite element model, the
levels given above may be increased by
pared to a beam model).
Fendering
towing equipment
means of a three
permissible stress
10 per cent (com-
: Bollard Pull, as defined in Sec 1, [4.1].
The DL takes into consideration anticipated dynamic effects
through the application of the Dynamic Amplification Factor (DAF) (see also Sec 1, [4.4]), but not bouncing effects
(see above).
The fender supporting structure shall be able to sustain the
DL, as specified above, without exceeding the stress level
criteria specified in [1.7].
1.10 Testing requirements
1.10.1 Towing winches, including the associated emergency quick-release devices are normally to be load tested
at the DL, as defined in [1.3], or the BHL, as defined in Sec
1, [4.5], whichever is the greatest. Generally, load testing is
to be conducted at a special facility equipped to generate
the required line tension (e.g. maker’s premises) and to be
witnessed by the Society.
In case a towing winch is of conventional, proven design,
for which load testing has been previously performed in a
deemed acceptable by the Society, it is sufficient to perform
on board function testing in accordance with the requirements specified below.
Note 1: The Society may request the winch manufacturer to supply
records of the load tests performed.
Bureau Veritas
July 2014
NI 617, Sec 3
1.10.2 Towing hooks, including the associated emergency
quick-release devices, are normally to be load tested at the
DL, as defined in [1.3]. Generally, load testing is to be conducted at a special facility equipped to generate the
required line tension (e.g. maker’s premises) and to be witnessed by the Society.
For novel or particular designs the emergency quick-release
devices is also to be load tested with the towline at an
upward angle of 45 degrees with the horizontal plane at a
towline force of not less than 50 per cent of the Bollard Pull,
as defined Sec 1, [4.1].
In case a towing hook is of conventional, proven design, for
which load testing has been previously performed in a
deemed acceptable by the Society, it is sufficient to perform
on board function testing in accordance with the requirements specified below.
Note 1: The Society may request the winch manufacturer to supply
records of the load tests performed.
1.10.3 In general, the proper functioning of the towing
equipment is to be verified by on board testing and to be
witnessed by the Society. Function testing is to be performed both for normal operating conditions and in accordance with the towing arrangement plan, see [1.2], as well as
in emergency conditions (emergency quick-release, failure
of main power supply). The safe operation of the towing
winch from all control stations is to be demonstrated.
1.10.4 Towing winches are to be function tested on board.
The correct functioning of the winch brake, the load carrying winch components and the associated supporting structure is to be demonstrated at a towline force equal to the
Bollard Pull, as defined in Sec 1, [4.1]. The emergency
quick-release is to be function tested under normal power
supply with a towline force corresponding to the minimum
thrust (engine(s) clutched in and running at idle speed), as
well as in dead-ship condition (without strain in the towline).
Winch operating modes to be function tested include hauling in and paying out of the towline, as well as braking.
Hydraulic and electrical systems shall be function tested on
board in accordance with the Society’s requirements for
machinery and electrical systems.
1.10.5 Towing hooks are to be function tested on board.
The correct functioning of the hook and the associated supporting structure is to be demonstrated at a towline force
equal to the Bollard Pull, as defined in Sec 1, [4.1]. The
emergency quick-release is to be function tested under normal power supply with a towline force corresponding to the
minimum thrust (engine(s) clutched in and running at idle
speed), as well as in dead-ship condition (without strain in
the towline).
1.10.6 Where deemed necessary by the Society towline
guiding fittings may be required to be function tested under
specified conditions.
July 2014
1.10.7 Operational tests are to be performed by the crew in
order to ensure the satisfactory operation of the towing
equipment, in particular the emergency quick-release systems, as requested by the operating manual.
Records of operational tests are to be kept on board and
made available to the Society upon request.
2
2.1
Towing equipment for service
notation escort tug
General
2.1.1 The requirements of [1] are to be complied with in
relation to normal towing services.
Note 1: Normal towing services are to be understood to include
towing and pushing operations other than escorting as defined in
Sec 1, [2.2.3].
2.1.2 Towing winches and towline guiding fittings (fairleads, staples, etc.) used for escort services are normally to
be arranged in way of the tug’s centreline, in such a position
as to minimise heeling moment.
2.1.3 Materials used in towing equipment are to comply
with the applicable class requirements for materials. Class
certificates are required for the materials used for winch
drums, drum shafts, winch brake components, winch supporting frames and towline guiding fittings.
2.1.4 Reliable emergency quick-release arrangements,
capable of releasing the towline under the maximum anticipated load regardless of the angle of the towline and the
tug’s trim and heel, are to be provided.
The emergency quick-release devices shall be operable in
case of failure of the main power supply.
2.2
Documents to be submitted
2.2.1 The following documents are to be submitted for
information:
• Escort towing arrangement plan, showing the location
and general lay-out of the towing equipment used for
escorting, the range of anticipated lines of action of the
towlines with the associated maximum steady towline
forces and the corresponding points of application of
the towline forces on the towing equipment
Note 1: The steady towline force is the towline force without
dynamic amplification effects (also called quasi-static towline
force).
• Summary tables of maximum steering force TY, in kN,
and maximum braking force TX, in kN, for the intended
range of speeds VY, in kn, as obtained from the results of
full scale tests or model tests, or alternatively, the results
of a computer simulation program accepted by the Society, refer to Sec 2, [3.5]
Note 2: In case the final values are not yet available, estimated values may be submitted as preliminary information for the purpose drawing review. In case the final values are significantly
higher than the preliminary values, the drawings are to be
reviewed against the final values.
Bureau Veritas
21
NI 617, Sec 3
• Detail arrangement drawings of the escort winch and
towline guiding fittings used for escorting (fairlead, staple)
• Design information of escort winch, including maximum rated line pull, winch brake holding force, rendering and recovering loads and specification of
emergency quick-release arrangement
This system is to automatically and reliably pay-out the towline in a controlled manner when the towline force exceeds
a pre-set (adjustable) level equal to 110 per cent of the rated
towline force TESC,R and, as the towline force is reduced,
actively haul-in the towline to prevent slack-line events and
maintain a pre-set or adjustable towline force consistent
with the rated towline force.
• Design calculations of escort winch, including winch
drums, main shaft, load carrying non-rotating structures
(support frame) and braking capacity
Pay-out and haul-in speeds and pull capability shall be chosen taking into account the anticipated escort services and
the dynamic characteristics of the escort tug.
• Design load of towline guiding fittings used for escorting
Escort operations in conditions where dynamic oscillations
of the towline are likely to occur may not be based on the
use of the brakes of the winch drum.
• Design calculations of the towline guiding fittings and
the supporting structures of towing equipment used for
escorting, including detailed analysis reports in case
three dimensional finite element models have been
used.
2.2.2 The following documents are to be submitted for
approval:
• Detailed drawings of the escort winch, including winch
drums, main shaft, load carrying non-rotating structures
(support frame), winch brakes, gears and clutches
• Hydraulic, electrical and control system diagrams of the
escort winch, as applicable
• Detailed drawings of the towline guiding fittings used
for escorting
• Supporting structures of towing equipment used for
escorting.
2.3
Design Load
Table 3 : Design Loads for escort tug
TESC,MAX [kN]
DL [kN]
TESC,MAX ≤ 500
3T
The measured data are to be displayed in the wheelhouse
next to the control desk or another appropriate location.
2.4.4 The escort towing system is to be designed so as to
enable the proper spooling of the towline on the winch
drum when hauling in. Generally this can be achieved by a
suitable design of the fairlead or staple guiding the towline
between the escort winch and the assisted ship.
500 < TESC,MAX < 1000
2000 – T
---------------------- T
500
TESC,MAX ≥ 1000
2T
2.4.5 Winches shall be provided with an emergency quickrelease device operable from a position on the bridge with
full view and control of the towing operation. Means of
control for the emergency quick-release device shall be
protected against unintentional use.
The time delay between the initiation and actual start of the
emergency quick-release (pay-out of the towline) should be
as short as reasonably practicable.
The speed of paying out shall be such that the tension in the
towline is reduced as fast as reasonably possible, taking into
consideration that paying out is to be done in a controlled
manner. To that end effective means to prevent spinning
(free, uncontrolled rotation) of the winch drum are to be
provided.
Note 1: The DL takes into consideration dynamic effects
through the application of the Dynamic Amplification Factor
(DAF) (see also Sec 1, [4.4]).
Design requirements for escort winches
2.4.1 The winch brake shall normally act directly on the
drum and shall be operable in case of failure in the primary
power supply system (either manually or otherwise
arranged).
Escort winches intended to be used in conditions where
dynamic oscillations of the towline are likely to occur, such
as in open sea areas or other areas exposed to waves, are to
be equipped with an active pay-out and haul-in system.
22
2.4.3 Escort winches are to be fitted with equipment to
continuously measure the tension in the towline.
Where a spooling device is fitted, this device should be
designed for the same Design Load and stress criteria as the
towline guiding fittings, see [2.6].
2.3.1 The Design Load DL to be considered for the strength
assessment of the towing equipment used for escort services
and the associated supporting structures is given in Tab 3.
2.4
2.4.2 Escort operations in calm water conditions, such as in
ports and sheltered (confined) waters, may be based on the
use of the brakes of the winch drum. As a minimum, the
winch brake holding load BHL is to be equal to or greater
than two times the maximum steady towline force TESC,MAX.
After a quick-release event the winch brakes shall directly
be able to operate normally (automatically), while the
winch motor shall be engaged manually (not automatically).
Note 1: Spinning of the winch drum could cause the towline to get
stuck and disable the release function of the winch
The applicable procedures for the emergency quick-release
device, including time delays and release speed, shall be
communicated to the crew and vital information shall be
displayed next to the control desk or another appropriate
location.
Bureau Veritas
July 2014
NI 617, Sec 3
The dimensioning of the winch drum is to take into account
the rope bending specifications provided by the towline
manufacturer.
Due consideration is to be given to preventing the towline
to slip over the flanges of the drum.
2.4.6 Escort winches (in particular the components which
are exposed to the tension in the towline, such as the winch
drums, drum shafts, brakes, support frame and connection
to the hull structure) shall be able to:
• sustain the DL, as specified in [2.3] without permanent
deformation, and
• sustain the BHL, as defined in Sec 1, [4.5], without
exceeding an equivalent stress level (based on Von
Mises criterion) of 0,80 ReH
where:
ReH
: Minimum specified yield stress of material,
in N/mm2.
2.4.7 Where deemed necessary by the Society, buckling
and/or fatigue analysis, performed in accordance with a
standard or code of practice recognised by the Society, may
be required to be submitted for information.
2.5
Design requirements for towlines
2.5.1 The breaking strength of towlines used for escort services is not to be less than the DL, as specified in [2.3].
In addition, the breaking strength for towlines used for
escort services on an escort winch is not to be less than the
BHL of the associated escort winch (see Sec 1, [4.5]).
2.6.3 Where a towline guiding fitting has been designed for
a specific Safe Working Load SWL, defined as the maximum static working load, the fitting shall be able to sustain
a force equal to 2 times the SWL without exceeding the
stress level criteria specified in [1.7].
2.6.4 In case the yielding check of the towline guiding fittings is carried out by means of a three dimensional finite
element model, the permissible stress levels given above
may be increased by 10 per cent (compared to a beam
model).
2.7
Design requirements for towing equipment supporting structures
2.7.1 The supporting structures of towing equipment used
for escort services shall be able to sustain the load exerted
on the supporting structure under the action of the towline
loaded under a tension equal to the DL, as specified in
[2.3], in the most unfavourable anticipated position of the
towline, without exceeding the stress level criteria specified
in [1.7].
2.7.2 In addition, supporting structures of towing equipment used for escort services shall be able to sustain the
load exerted on the supporting structure under the action of
the towline loaded under a tension equal to the BHL of the
associated winch, as specified in Sec 1, [4.5], in the most
unfavourable anticipated position of the towline without
exceeding the stress level criteria specified in [1.7].
2.5.2 The towline shall be protected from being damaged
by chafing and abrasion. To this end cargo rails, bulwarks,
and other elements, supporting the towline should be adequately rounded.
2.7.3 Where a towline guiding fitting has been designed for
a specific Safe Working Load SWL, defined as the maximum static working load, the associated supporting structure shall be able to sustain a force equal to 2 times the
SWL without exceeding the stress level criteria specified in
[1.7].
2.5.3 It is recommended that the total length of the towline
applied on a towing winch is to be such that under normal
operation at least half a layer remains on the drum. In no
case less than three turns shall remain on the drum in under
normal operation.
2.7.4 In case the yielding check of the
supporting structures is carried out by
dimensional finite element model, the
levels given above may be increased by
pared to a beam model).
2.6
2.8
Design requirements for towline guiding
fittings
2.6.1 Towline guiding fittings used for escort services, such
as fairleads, staples and equivalent components which
guide the towline, shall be able to sustain the force exerted
by the towline loaded under a tension equal to the DL, as
specified in [2.3], in the most unfavourable anticipated
position of the towline without exceeding the stress level
criteria specified in [1.7].
2.6.2 In addition, towline guiding fittings shall be able to
sustain the force exerted by the towline loaded under a tension equal to the BHL of the associated winch, as specified
in Sec 1, [4.5], in the most unfavourable anticipated position of the towline without exceeding the stress level criteria
specified in [1.7].
July 2014
towing equipment
means of a three
permissible stress
10 per cent (com-
Testing requirements
2.8.1 Escort winches, including the associated emergency
quick-release device are normally to be load tested at the
DL, as defined in [2.3], or the BHL, as defined in Sec 1,
[4.5], whichever is the greatest. Generally, load testing is to
be conducted at a special facility equipped to generate the
required line tension (e.g. maker’s premises) and to be witnessed by the Society.
In case an escort winch is of conventional, proven design,
for which load testing has been previously performed in a
deemed acceptable by the Society, it is sufficient to perform
on board function testing in accordance with the requirements specified below.
Note 1: The Society may request the winch manufacturer to supply
records of the load tests performed.
Bureau Veritas
23
NI 617, Sec 3
2.8.2 In general, the proper functioning of the towing
equipment used for escort services is to be verified by on
board testing and to be witnessed by the Society. Function
testing is to be performed both for normal operating conditions and in accordance with the escort towing arrangement
plan, see [2.2], as well as in emergency conditions (emergency quick-release, failure of main power supply). The safe
operation of the escort winch from all control stations is to
be demonstrated.
Escort winches are to be function tested on board. The correct functioning of the winch brake, the load carrying winch
components and the associated supporting structure is to be
demonstrated at a towline force equal to the Bollard Pull, as
defined in Sec 1, [4.1]. The emergency quick-release is to
be function tested under normal power with a towline force
corresponding to the minimum thrust (engine(s) clutched in
and running at idle speed), as well as in dead-ship condition (without strain in the towline).
Winch operating modes to be function tested include hauling in and paying out of the towline, braking and the active
pay-out and haul-in system when fitted (see [2.4]).
24
Hydraulic and electrical systems shall be function tested on
board in accordance with the Society’s requirements for
machinery and electrical systems.
2.8.3 Where deemed necessary by the Society towline
guiding fittings used for escort services may be required to
be function tested under specified conditions.
2.8.4 Operational tests are to be performed by the crew in
order to ensure the satisfactory operation of the towing
equipment used for escort services, in particular the emergency quick-release systems, as requested by the operating
manual.
Records of operational tests are to be kept on board and
made available to the Society upon request.
2.9
Inclinometer
2.9.1 Escort tugs are to be equipped with a calibrated heeling angle measurement system (inclinometer).
The measured heeling angle is to be displayed in the wheelhouse next to the control desk or another appropriate location.
Bureau Veritas
July 2014
NI 617, Sec 4
SECTION 4
1
FIRE SAFETY FOR TUGS OF LESS THAN 500 GT
• Fixed fire extinguishing systems should be installed, as
applicable, having due regard to the fire growth potential of the protected spaces; and
General
1.1
Scope of application
1.1.1 This section applies to tugs of less than 500 GT.
• Fire extinguishing appliances should be readily available.
1.2
2.2
Fire safety objectives
Capacity
2.2.1 The total capacity Q, in m3/hour, of the main fire
pump(s) is not to be less than:
1.2.1 The fire safety objectives of this section are to:
• Prevent the occurrence of fire and explosion
Q = ( 0,145 L ( B + D ) + 2,170 )
• Reduce the risk to life caused by fire
• Reduce the risk of damage caused by fire to the tug and
the environment
• Contain, control and suppress fire and explosion in the
compartment of origin; and
• Provide adequate and readily accessible means of
escape for crew.
1.2.2 The fire safety objectives set out above could be
achieved by ensuring compliance with [2] to [7], or by
alternative design and arrangements which comply with [7].
A tug could be considered to achieve the fire safety objectives set out in first paragraph when either:
• The tug's designs and arrangements, as a whole, comply
with [2] to [6], as applicable
• The tug's designs and arrangements, as a whole, have
been reviewed and approved in accordance with [7]; or
• Part(s) of the tug's designs and arrangements have been
reviewed and approved in accordance with [7] and the
remaining parts of the tug comply with the relevant Recommendations in [2] to [6].
1.3
Requirements for fire safety equipment
1.3.1 Requirements for fire safety equipment are defined in
Tab 1.
2
Fire pumps and fire main systems
2.1
Purpose
2.1.1 The purpose of this requirement is to suppress and
swiftly extinguish a fire in the space of origin. For this purpose, the following functional requirements should be met:
July 2014
2
but need not exceed 25 m3/hour,
where:
L
: Freeboard Length, in m
B
: Greatest moulded breadth of tug, in m
D
: Moulded depth to bulkhead deck, in m.
2.3
Fire pumps
2.3.1 Generally one main power pump and one portable
fire pump should be provided as specified below:
a) Sanitary, ballast, bilge or general service pumps may be
accepted as fire pumps, provided that they are not normally used for pumping oil, and that, if they are subject
to occasional duty for the transfer or pumping of fuel
oil, suitable changeover arrangements are fitted
b) A power pump is a fixed pump driven by a power
source other than by hand. An independently driven
power pump is independent from the main engine(s)
c) Provisions are to be made for clearing sea inlet gratings
of fire pump sea inlet valves. Special attention is to be
paid to ice clearing arrangements for tugs intended for
navigation in ice (e.g. air blowing, heating)
d) Relief valves should be provided in conjunction with
any fire pump if the pump is capable of developing a
pressure exceeding the design pressure of the water
service pipes, hydrants and hoses. These valves should
be so placed and adjusted as to prevent excessive pressure in any part of the fire main system
e) Where a centrifugal pump is provided in order to comply with this sub-section, a non-return valve should be
fitted in the pipe connecting the pump to the fire main.
Bureau Veritas
25
NI 617, Sec 4
Table 1 : Fire safety requirements
tug / escort tug
harbour tug
(unrestricted)
sailing time ≤ 4h from a
safe sheltered anchorage
(in port)
1
1
1
power pumps
1
1
1
hand pumps
−
−
−
−
−
−
power pumps
1
1
1
hand pumps
1
1
−
1 (1) (2)
1 (1) (2)
−
≥ 150 gt Sufficient number and so located that at least
the number of powerful water jets can reach any
normally accessible part of tug
2
2
2
< 150 gt Sufficient number and so located that at least
the number of powerful water jets can reach any
normally accessible part of tug
1
1
1
fire pumps
≥ 150 gt independently driven power pumps
< 150 gt independently driven power pumps
portable or fixed emergency fire pump
fire hydrants
fire hoses (length)
number of hydrants
+ 1 spare hose
(3)
with coupling and nozzles
number of hydrants
+ 1 spare hose
number of hydrants
+ 1 spare hose
X
X
X
X
X
X
≥2
≤6
≥2
≤6
≥2
≤6
X
X
−
X
X
X
≥1
≥1
−
fireman’s axe
1
1
1
≥ 150 gt fire control plan
1
1
1
accommodation and service spaces
2
2
2
machinery spaces (5)
2
2
2
hose nozzles
dual purpose (spray/jet) with 12 mm jet and integral shutoff; jet may be reduced to 10 mm and shut-off omitted for
hand pump hoses
portable fire extinguishers
machinery spaces (one extinguisher per 375 kW of internal
combustion engine power (4) (capacity 45 l fluid or equivalent)
fixed fire extinguishing systems
≥ 150 gt Category ‘A’ machinery spaces
fixed fire detection system (Category ‘A’ spaces)
fireman’s outfit
complete outfit
means of escape
(1)
(2)
(3)
(4)
(5)
26
For tugs of less than 150 GT fitted with an approved fixed fire-fighting system in the engine room, portable pumps may be omitted.
When a portable / emergency firepump is fitted, (independent) power pump may be omitted.
Sufficient in length to project a jet of water to any of the spaces in which they may be required to be used.
Alternatives may be proposed taking into consideration the size of the tug and the installed power.
Unless when the small size of the machinery space makes it unpractical.
Bureau Veritas
July 2014
NI 617, Sec 4
2.4
Portable fire pumps
2.4.1 Portable fire pumps should comply with the following:
a) The pump should be self-priming
b) The total suction head and the net positive suction head
of the pump should be determined taking account of
actual operation, i.e. pump location when used
d) Pump is required to supply water for a fixed fire-extinguishing system in the space there the main fire pump is
situated, it should be capable of simultaneously supplying water to this system and the fire main at the required
rates
e) The pump may also be used for other suitable purposes,
subject to the approval in each case
f)
Note 1: Net positive suction head of the pump is to be realised
from the deck where the pump is fitted (in practical cases on
tugs this is typically the maindeck).
c) The portable fire pump, when fitted with its length of
discharge hose and nozzle, should be capable of maintaining a pressure sufficient to produce a jet throw of at
least 12 m, or that required to enable a jet of water to be
directed on any part of the engine room or the exterior
boundary of the engine room and casing, whichever is
the greater
d) Except for electric pumps, the pump set should have its
own fuel tank of sufficient capacity to operate the pump
for three hours. For electric pumps, their batteries
should have sufficient capacity for three hours
e) Except for electric pumps, details of the fuel type and
storage location should be carefully considered. If the
fuel type has a flashpoint below 60°C, further consideration to the fire safety aspects should be given
f)
The pump set should be stored in a secure, safe and
enclosed space, accessible from open deck and clear of
the Category ‘A’ machinery space
g) The pump set should be easily moved and operated by
two persons and be readily available for immediate use
h) Arrangements should be provided to secure the pump at
its anticipated operating position(s)
i)
j)
The overboard suction hose should be non-collapsible
and of sufficient length, to ensure suction under all
operating conditions. A suitable strainer should be fitted
at the inlet end of the hose
Any diesel-driven power source for the pump should be
capable of being readily started in its cold condition by
hand (manual) cranking. If this is impracticable, consideration should be given to the provision and maintenance of heating arrangements, so that readily starting
can be ensured.
2.4.2 Alternatively to the requirements of [2.4.1], a fixed
fire pump may be fitted, which should comply with the following:
a) The pump, its source of power and sea connection
should be located in accessible positions, outside the
compartment housing the main fire pump
b) The sea valve should be capable of being operated from
a position near the pump
2.4.3 For tugs of less than 150 GT fitted with an approved
fixed fire-fighting system in the engine room, portable
pumps may be omitted.
2.4.4 Means to illuminate the stowage area of the portable
pump and its necessary areas of operation should be provided from the emergency source of electrical power.
2.5
Fire main
2.5.1 The diameter of the fire main should be based on the
required capacity of the fixed main fire pump(s) and the
diameter of the water service pipes should be sufficient to
ensure an adequate supply of water for the operation of at
least one fire hose.
2.5.2 The wash deck line may be used as a fire main provided that the requirements of this sub-section are satisfied.
2.5.3 All exposed water pipes for fire-extinguishing should
be provided with drain valves for use in frosty weather. The
valves should be located where they will not be damaged
by tug operations.
2.6
Pressure in the fire main
2.6.1 When the main fire pump is delivering the quantity of
water required by [2.2], or the fire pump described in
[2.4.2], through the fire main, fire hoses and nozzles, the
pressure maintained at any hydrant should be sufficient to
produce a jet throw at any nozzle of not less than 12 m in
length. (For tugs of less than 150 GT, the jet of water may be
specially considered).
2.7
2.7.1
Fire Hydrants
Number and position of hydrants
• For tugs of less than 150 GT the number and position of
the hydrants should be such that at least one jet of water
may reach any part normally accessible to the crew,
while the tug is being navigated and any part of any
deck space when empty.
c) The room where the fire pump prime mover is located
should be illuminated from the emergency source of
electrical power, and should be well ventilated
July 2014
Pressure and quantity of water delivered by the pump
being sufficient to produce a jet of water, at any nozzle,
of not less than 12 m in length. For tugs of less than 150
GT, the jet of water may be specially considered.
Bureau Veritas
Furthermore, such hydrants should be positioned near
the accesses to the protected spaces. At least one
hydrant should be provided in each Category ‘A’
machinery space.
27
NI 617, Sec 4
• For tug equal to or greater than 150 GT the number and
position of hydrants should be such that at least two jets
of water not emanating from the same hydrant, one of
which should be from a single length of hose, may reach
any part of the tug normally accessible to the crew
while the tug is being navigated and any part of any
cargo spaces when empty.
Furthermore, such hydrants should be positioned near
the accesses to the protected spaces. Other Requirements specified by the Administration may be considered.
2.7.2
2.9.2 For accommodation and service spaces, the nozzle
size need not exceed 12 mm.
2.9.3 The size of nozzles used in conjunction with a portable fire pump need not exceed 12 mm.
2.9.4 All nozzles should be of an approved dual purpose
type (i.e. spray/jet type) incorporating a shut-off.
3
Fire safety measures
3.1
Pipes and hydrants
a) Materials readily rendered ineffective by heat should not
be used for fire mains. Where steel pipes are used, they
should be galvanized internally and externally. Cast iron
pipes are not acceptable. The pipes and hydrants should
be so placed that the fire-hoses may be easily coupled
to them. The arrangement of pipes and hydrants should
be such as to avoid the possibility of freezing. In tugs
where deck cargo may be carried, the positions of the
hydrants should be such that they are always readily
accessible and the pipes should be arranged, as far as
practicable, to avoid risk of damage by such cargo.
There should be complete interchange ability of hose
couplings and nozzles
b) A valve should be fitted at each fire hydrant so that any
fire-hose may be removed while the fire pump is at work
c) Where a fixed fire pump is fitted outside the engine
room, in accordance with [2.4.2]:
1) an isolating valve should be fitted in the fire main so
that all the hydrants in the tug, except those in the
Category ‘A’ machinery space, can be supplied with
water. The isolating valve should be located in an
easily accessible and tenable position outside the
Category ‘A’ machinery space; and
Purpose
3.1.1 The purpose of this regulation should contain a fire in
the space of origin. For this purpose, the following functional requirements should be met:
• The tug should be subdivided by thermal and structural
boundaries;
• Thermal insulation of boundaries should have due
regard to the fire risk of the space and adjacent spaces;
• The fire integrity of the divisions should be maintained
at openings and penetrations.
3.2
Structural fire protection
3.2.1 The minimum fire integrity of bulkheads and decks
should be as prescribed in Tab 2.
Table 2 : Minimum fire integrity of bulkheads and
decks
Item
Space
Separation by
From space
1
Machinery Space
Class A
A-60
Accommodation
Control stations
Corridors
Staircases
Service spaces of
high fire risk
2
Machinery Space
Class A
A-0
Other than above
(Item 1)
3
Galley
A-0
Unless specified
otherwise
4
Service space of
high fire risk
other than galley
B-15
Unless specified
above (Item 1)
5
Corridor
Staircase / escape
route
A-0
Unless specified
above (Item 1)
2) the fire main should not re-enter the machinery
space downstream of the isolating valve.
2.8
Fire-hoses
2.8.1 Fire-hoses should be of approved non-perishable
material. The hoses should be sufficient in length to project
a jet of water to any of the spaces in which they may be
required to be used. Their length, in general, is not to
exceed 18 m. Each hose should be provided with a nozzle
and the necessary couplings. Fire-hoses, together with any
necessary fittings and tools, should be kept ready for use in
conspicuous positions near the water service hydrants or
connections.
2.8.2 One hose should be provided for each hydrant. In
addition one spare hose should be provided on board.
2.9
Nozzles
2.9.1 For the purpose of this section, standard nozzle sizes
are 12 mm, 16 mm or 19 mm, or as near thereto as possible, so as to make full use of the maximum discharge
capacity of the fire pump(s).
28
Note 1: The divisions used to separate spaces not mentioned
above should be of non-combustible material.
3.2.2 The hull, superstructure, structural bulkheads, decks
and deckhouses should be constructed of steel or other
equivalent material. For the purpose of applying the definition of steel or other equivalent material, as given in SOLAS,
the ‘applicable fire exposure’ should be one hour. Tugs built
of materials other than steel should be specially considered.
Bureau Veritas
July 2014
NI 617, Sec 4
3.2.3 Stairways should be enclosed, at least at one level, by
divisions and doors or hatches, in order to restrict the free
flow of smoke to other decks in the tug and the supply of air
to the fire. Doors forming such enclosures should be selfclosing.
3.2.4 Openings in ‘A’ Class divisions should be provided
with permanently attached means of closing which should
be at least as effective for resisting fires as the divisions in
which they are fitted.
3.2.5 Interior stairways serving machinery spaces, accommodation spaces, service spaces or control stations should
be of steel or other equivalent material.
3.2.6 Doors should be self-closing in way of Category ‘A’
machinery spaces and galleys, except where they are normally kept closed.
3.2.7 Where ‘A’ Class divisions are penetrated for the passage of electric cables, pipes, trunks, ducts, etc., or for girders, beams or other structural members, arrangements
should be made to ensure that the fire resistance is not
impaired. Arrangements should also prevent the transmission of heat to un-insulated boundaries at the intersections
and terminal points of the divisions and penetrations by
insulating the horizontal and vertical boundaries or penetrations for a distance of 450 mm.
3.3
Materials
3.3.1 Paints, varnishes and other finishes used on exposed
interior surfaces should not be capable of producing excessive quantities of smoke, toxic gases or vapours and should
be of the low flame spread type in accordance with the
IMO FTP Code, Annex 1, Parts 2 and 5.
3.3.2 Except in cargo spaces or refrigerated compartments
of service spaces, insulating materials should be non-combustible.
3.3.3 Where pipes penetrate ‘A’ or ‘B’ Class divisions, the
pipes or their penetration pieces should be of steel or other
approved materials having regard to the temperature and
integrity Recommendations such divisions are required to
withstand.
3.3.4 Pipes conveying oil or combustible liquids through
accommodation and service spaces should be of steel or
other approved materials having regard to the fire risk.
3.3.5 Materials readily rendered ineffective by heat should
not be used for overboard scuppers, sanitary discharges and
other outlets which are close to the waterline, and where
the failure of the material in the event of fire would give rise
to the danger of flooding.
3.3.6 Primary deck coverings within accommodation
spaces, service spaces and control stations should be of a
type which will not readily ignite, or give rise to toxic or
explosive hazards at elevated temperatures in accordance
with the IMO FTP Code, Annex 1, Parts 2 and 6.
July 2014
3.3.7 Materials used for insulating pipes, etc., in machinery
spaces and other compartments containing high fire risks
should be non-combustible. Vapour barriers and adhesives
used in conjunction with insulation, as well as the insulation of pipe fittings, for cold service systems need not be of
non-combustible materials, but they should be kept to the
minimum quantity practicable and their exposed surfaces
should have low flame spread characteristics.
3.4
Surface of insulation
3.4.1 In spaces where penetration of oil products is possible, the surface of the insulation should be impervious to oil
or oil vapours. Insulation boundaries should be arranged to
avoid immersion in oil spillage.
3.5
Ventilation systems
3.5.1 Ventilation fans should be capable of being stopped
and main inlets and outlets of ventilation systems closed
from outside the spaces being served.
3.5.2 Ventilation ducts for Category ‘A’ machinery spaces
should not pass through accommodation spaces, galleys,
service spaces or control stations, unless the ducts are constructed of steel and arranged to preserve the integrity of the
division.
3.5.3 Ventilation ducts for accommodation spaces, service
spaces or control stations should not pass through Category
‘A’ machinery spaces or galleys unless the ducts are constructed of steel and arranged to preserve the integrity of the
division.
3.5.4 Ventilation arrangement for store rooms containing
highly flammable products should be specially considered.
3.5.5 Ventilation systems serving Category ‘A’ machinery
spaces and galley exhaust ducts should be independent of
systems serving other spaces.
3.5.6 Ventilation should be provided to prevent the accumulation of gases that may be emitted from batteries.
3.5.7 Ventilation openings may be fitted in and under the
lower parts of cabin, mess and dayroom doors in corridor
bulkheads. The total net area of any such openings is not to
exceed 0.05 m2. Balancing ducts should not be permitted in
fire divisions.
3.6
Oil fuel arrangements
3.6.1 In a tug in which oil fuel is used, the arrangements for
the storage, distribution and utilization of the oil fuel should
be such as to ensure the safety of the tug and persons on
board.
3.6.2 Oil fuel tanks situated within the boundaries of Category ‘A’ machinery spaces should not contain oil fuel having a flashpoint of less than 60°C.
3.6.3 Oil fuel, lubricating oil and other flammable oils
should not be carried in a forepeak tank or a tank forward of
the collision bulkhead.
Bureau Veritas
29
NI 617, Sec 4
3.6.4 As far as practicable:
a) oil fuel lines shall be arranged far apart from hot surfaces, electrical installations or other sources of ignition
and shall be screened or otherwise suitably protected to
avoid oil spray or oil leakage onto the sources of ignition. The number of joints in such piping systems shall
be kept to a minimum.
b) surfaces with temperatures above 220°C which may be
impinged as a result of a fuel and/or hydraulic oil system
failure shall be properly insulated. Precautions shall be
taken to prevent any oil that may escape under pressure
from any pump, filter or heater from coming into contact with heated surfaces.
c) external high-pressure fuel delivery lines between the
high pressure fuel pumps and fuel injectors shall be protected with a jacketed piping system capable of containing fuel from a high-pressure line failure. A suitable
enclosure on engines having an output of 375 kW or
less having fuel injection pumps serving more than one
injector may be used as an alternative to the jacketed
piping system.
3.7.5 The controls required in [3.7.4] should be located
outside the space concerned, where they will not be cut off
in the event of fire in the space they serve. Such controls
and the controls for any required fire-extinguishing system
should be situated at one control position or grouped in as
few positions as possible. Such positions should have a safe
access from the open deck.
3.8
Arrangements for gaseous fuel for
domestic purposes
3.8.1 Where gaseous fuel is used for domestic purposes,
the arrangements for the storage, distribution and utilization
of the fuel should be specially considered.
3.9
Space heating
3.9.1 Space heaters, if used, should be fixed in position
and so constructed as to reduce fire risks to a minimum. The
design and location of these units should be such that clothing, curtains or other similar materials cannot be scorched
or set on fire by heat from the unit.
3.10 Means of escape
3.7
Special arrangements in Category A
machinery spaces and where necessary
other machinery spaces
3.7.1 The number of skylights, doors, ventilators, openings
in funnels to permit exhaust ventilation and other openings
to machinery spaces should be reduced to a minimum consistent with the needs of ventilation and the proper and safe
working of the tug.
3.7.2 Skylights should be constructed with steel frames and
are not to contain glass panels, unless fire-retardant glass
equivalent to steel is applied. Suitable arrangements should
be made to permit the release of smoke, in the event of fire,
from the space to be protected.
3.7.3 Windows should not be fitted in machinery space
boundaries. This does not preclude the use of glass in control rooms within the machinery spaces.
3.7.4 Means of control should be provided for:
a)
opening and closure of skylights, closure of openings in
funnels which normally allow exhaust ventilation, and
closure of ventilator dampers;
permitting the release of smoke;
b) closing power-operated doors or actuating release
mechanism on doors other than power-operated watertight doors;
3.10.1 The purpose of this requirement is to provide means
of escape so that persons on board can safely and swiftly
escape to the lifeboat and liferaft embarkation deck. For this
purpose, the following functional requirements should be
met:
• Safe escape routes should be provided;
• Escape routes should be maintained in a safe condition,
clear of obstacles; and
• Additional aids for escape should be provided as necessary to ensure accessibility, clear marking, and adequate
design for emergency situations.
3.10.2 Stairways, ladders and corridors serving crew
spaces and other spaces to which the crew normally have
access should be arranged so as to provide ready means of
escape to a deck from which embarkation into survival craft
may be effected.
3.10.3 There should be at least two means of escape, as
widely separated as possible, from each section of accommodation and service spaces and control stations.
a) The normal means of access to the accommodation and
service spaces below the open deck should be arranged
so that it is possible to reach the open deck without
passing through spaces containing a possible source of
fire (e.g. machinery spaces, storage spaces of flammable
liquids).
b) The second means of escape may be through portholes
or hatches of adequate size and preferably leading
directly to the open deck.
c) stopping ventilating fans; and
c) Dead-end corridors having a length of more than 7 m
should not be accepted.
d) stopping forced and induced draught fans, oil fuel transfer pumps, oil fuel unit pumps and other similar fuel
pumps.
Note 1: The escapes should be positioned either both at centerline,
at centreline and at port side, at centreline and at starboard side or
at starboard side and at port side. Having both escapes on one side
of the tug should be avoided.
30
Bureau Veritas
July 2014
NI 617, Sec 4
3.10.4 At least two means of escape should be provided from
machinery spaces, except where the small size of a machinery
space makes it impracticable. Escape should be by steel ladders that should be as widely separated as possible.
4
Fixed fire detection and fire-alarm
systems
4.1
General
Purpose
5.1.1 The purpose of this requirement should suppress and
swiftly extinguish a fire in the space of origin. For this purpose, the following functional requirements should be met:
• Fixed fire-extinguishing systems should be installed, as
applicable, having due regard to the fire growth potential of the protected spaces; and
• Fire-extinguishing appliances should be readily available.
≥1
≥2
≤6
Approved types
All fire-extinguishers should be of approved types and
designs.
5.6.3
Extinguishing medium
a) The extinguishing media employed should be suitable
for extinguishing fires in the compartments in which
they are intended to be used.
5.6.4
Capacity
a) The capacity of required portable fluid extinguishers
should not exceed more than 13,5 litres but not less
than 9 litres. Other extinguishers should be at least as
portable as the 13,5 litre fluid extinguishers, and should
have a fire-extinguishing capability at least equivalent to
a 9 litre fluid extinguisher.
b) The following capacities may be taken as equivalents:
• 9 litre fluid extinguisher (water or foam);
• 5 kg dry powder;
Fixed fire-extinguishing systems
5.3.1 Fixed fire-fighting systems where required, should be
in accordance with the requirements of the IMO FSS Code.
5.4
≥3
tugs of less than 150 GT (see [5.6.7])
Fixed fire-extinguishing arrangements
in Category A machinery spaces
5.2.1 Machinery spaces of Category A on tugs with GT
greater than or equal to 150 except for harbour tugs, should
be provided with an approved fixed fire extinguishing system, as specified in [5.2].
5.3
tugs greater than or equal to 150 GT
•
b) The extinguishers required for use in the machinery
spaces of tugs using oil as fuel should be of a type discharging foam, carbon dioxide gas, dry powder or other
approved media suitable for extinguishing oil fires.
Fire-extinguishing arrangements
5.2
•
5.6.2
Note 1: Upon special consideration, taking into account the size
and arrangement (general layout and number of deckhouse tiers) of
the tug, approved fire detectors may be connected to a group alarm
system.
5.1
Accommodation and service spaces
Machinery spaces (one extinguisher per every 375 kW
of internal combustion engine power)
4.1.1 An approved and fixed fire detection system should be
installed in all Category ‘A’ machinery spaces. Manual activating units should be positioned near each emergency exit.
5
Table 3 : Portable Fire-extinguishers
Protection of paint lockers and flammable liquid lockers
• 5 kg carbon dioxide.
5.6.5
Spare charges
A spare charge should be provided for each required portable fire-extinguisher that can be readily recharged on board.
If this cannot be done, duplicate extinguishers should be
provided.
5.6.6
Location
a) The extinguishers should be stowed in readily accessible positions and should be spread as widely as possible
and not be grouped.
5.4.1 The Recommendations for the protection of paint
lockers and flammable liquids lockers should be specially
considered.
b) One of the portable fire-extinguishers intended for use
in any space should be stowed near the entrance to that
space.
5.5
5.6.7
Fixed fire-extinguishing systems not
required by this section
5.5.1 If such a system is installed, it should be of an
approved type.
5.6
Portable Fire-extinguishers
5.6.1 Number of portable fire-extinguishers
The number of portable fire-extinguisher is defined in Tab 3.
July 2014
Portable fire-extinguishers in accommodation
spaces, service spaces and control stations
Accommodation spaces, service spaces and control stations
should be provided with a sufficient number of portable fireextinguishers to ensure that at least one extinguisher will be
readily available for use in every compartment of the crew
spaces. In any case, their number should be not less than
three, except where this is impractical for very small tugs, in
which case one extinguisher should be available at each deck
having accommodation or service spaces, or control stations.
Bureau Veritas
31
NI 617, Sec 4
6
Fire-fighting equipment
Table 4 : Language in fire control plan
Service notations
6.1
General
6.1.1 The fire-fighting equipment should comply with the
minimum requirements as specified below:
6.2
Fire-fighter’s outfit (which includes an
axe)
tug, escort tug (unrestricted)
English
harbour tug
tug, escort tug with additional service feature sailing
time ≤ 4 h from safe sheltered anchorage
Official language(s) of the
Administration(s) concerned
with the tug’s service, or language(s) recognized by such
Administration(s) (possibly
English).
However, description in such
plans and booklets for tugs
engaged in domestic service
only may be in the official
language of the Flag State
only.
6.2.1 Except for harbour tugs, at least one fire-fighter’s outfit complying with the Requirements of the IMO FSS Code,
should be provided on board.
6.3
Description of fire control plans
6.3.1 In all tugs, general arrangement plans should be permanently exhibited for the guidance of the tug's officers,
using graphical symbols that are in accordance with IMO
Resolution A.952(23), which show clearly for each deck the
control stations, the various fire sections enclosed by steel
or ‘A’ Class divisions, together with particulars of:
6.3.4 In general, on all tugs greater than or equal to 150
GT, a duplicate set of fire-control plans or a booklet containing such plans should be permanently stored in a prominently marked weather tight enclosure outside the
deckhouse for the assistance of shoreside fire fighting personnel.
6.3.5 For service notation harbour tug a duplicate set of the
fire-control plan may be stored at a shore side facility.
7
• The fire detection and fire-alarm systems
• Fixed fire-fighting system
• The fire-extinguishing appliances
7.1
• The means of access to different compartments, decks,
etc.
• The position of the fireman's outfits
• The ventilating system, including particulars of the fan
control positions, the position of dampers and identification numbers of the ventilating fans serving each section, and
• The location and arrangement of the emergency stop for
the oil fuel unit pumps and for closing the valves on the
pipes from oil fuel tanks.
6.3.2 Alternatively, the details required by [6.3.1] may be
set out in a booklet, a copy of which should be supplied to
each officer, and one copy is at all times to be available on
board in an accessible position.
6.3.3 The plans and booklets should be kept up to date,
any alterations being recorded thereon as soon as practicable. Description in such plans and booklets should be in the
official language of the Flag State and in the language as
shown in the following Tab 4. In addition, instructions concerning the maintenance and operation of all the equipment and installations on board for the fighting and
containment of fire should be kept under one cover, readily
available in an accessible position.
32
Language
Alternative design and arrangements
for fire safety
Purpose
7.1.1 The purpose of this recommendation should provide
a methodology for alternative design and arrangements for
fire safety.
7.2
General
7.2.1 Fire safety design and arrangements may deviate from
[2] to [7] of this section, provided that the design and
arrangements meet the fire safety objectives and the functional Recommendations.
7.2.2 When fire safety design or arrangements deviate from
the requirements of this section, engineering analysis, evaluation and approval of the alternative design and arrangements should be carried out in accordance with this
regulation.
Note 1: Reference can be made to MSC/Circ.1002 "Guidelines on
alternative design and arrangements for fire safety".
7.3
Engineering analysis
7.3.1 The engineering analysis should be prepared and
submitted to the Society, based on the guidelines developed
by the International Maritime Organization and should
include, as a minimum, the following elements:
a) determination of the tug type and space(s) concerned
b) identification of recommendation(s) with which the tug
or the space(s) will not comply
Bureau Veritas
July 2014
NI 617, Sec 4
c) identification of the fire and explosion hazards of the
tug or the space(s) concerned:
• identification of the possible ignition sources
• identification of the fire growth potential of each
space concerned
• identification of the smoke and toxic effluent generation potential for each space concerned
• identification of the potential for the spread of fire,
smoke or of toxic effluents from the space(s) concerned to other spaces
d) determination of the required fire safety performance
criteria for the tug or the space(s) concerned:
• performance criteria should be based on the fire
safety objectives and on the functional Recommendations of this section
• performance criteria should provide a degree of
safety not less than that achieved the recommendation in [2] to [7], and
• performance criteria should be quantifiable and
measurable
e) detailed description of the alternative design and
arrangements, including a list of the assumptions used
in the design and any proposed operational restrictions
or conditions, and
July 2014
f)
technical justification demonstrating that the alternative
design and arrangements meet the required fire safety
performance criteria.
7.4
Evaluation of the alternative design and
arrangements
7.4.1 The engineering analysis required in [7.3] should be
evaluated and approved by the Society taking into account
the guidelines developed by the International Maritime
Organization.
7.4.2 A copy of the documentation, as approved by the
Society, indicating that the alternative design and arrangements comply with this regulation should be carried on
board the tug.
7.5
Re-evaluation due to change of conditions
7.5.1 If the assumptions, and operational restrictions that
were stipulated in the alternative design and arrangements
are changed, the engineering analysis should be carried out
under the changed condition and should be approved by
the Society.
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33
NI 617, Sec 5
SECTION 5
1
1.1
LIFE SAVING APPLIANCES FOR TUGS OF LESS
THAN 500 GT
General
1.2
Requirements for life saving appliances
1.2.1 Requirements for life saving appliances are defined in
Tab 1.
Scope of application
1.1.1 This section applies to tugs of less than 500 GT.
1.2.2 The equipment specified in Tab 1 should comply
with the IMO Life Saving Appliances Code or specified otherwise by the Administration.
Table 1 : Life saving appliances
tug / escort tug
harbour tug
(unrestricted)
sailing time ≤ 4h from a
safe sheltered anchorage
(in port)
X
X
(1)
life rafts
100% capacity on each side / easy side to side transfer,
or
150% capacity on each side
hydrostatic releases
X
X
(1)
Illumination and operating instructions
X
X
(1)
X (2)
X (2)
−
Jason’s cradle
X
X
X
search light
X
X
X
with smoke/light
2
1
1
with light
1
1
1
with lifeline
1
1
1
X
X
X
X (3)
X (3)
−
rocket parachute flares
12
6
−
red hand flares
6
2
2
smoke signals
MOB arrangement
rescue boat
Lifebuoys
lifejackets with lights
each person on board
immersion suit
each person on board
other equipment
(1)
(2)
(3)
(4)
34
2 buoyant
2
2
line throwing apparatus
1
1
−
general alarm
X
X
X
A float free buoyant apparatus is to be provided.
The tug’s operational working area, manoeuvrability, size, freeboard and propulsion arrangement may be taken into consideration for the evaluation of the applicability of the requirement for a rescue boat.
If the tug is constantly engaged in warm climates (refer to MSC Circ.1046) where, in the opinion of the Administration thermal
protection is unnecessary, immersion suits need not be carried on board.
An illustrated table describing the life saving signals shall be readily available to the officer of the watch of every tug to all tugs
on all voyages. The signals shall be used by tugs or persons in distress when communicating with life-saving stations, maritime
rescue units and aircraft engaged in search and rescue operations.
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July 2014
NI 617, Sec 5
tug / escort tug
harbour tug
(unrestricted)
sailing time ≤ 4h from a
safe sheltered anchorage
(in port)
X
X
X
X
X
X
communication system
to engine room / accommodation / deck
documentation on board
fire and safety plan
(1)
(2)
(3)
(4)
training and instruction manual
X
X
X
SOLAS life saving table (4)
X
X
X
muster list and emergency instructions
X
X
X
A float free buoyant apparatus is to be provided.
The tug’s operational working area, manoeuvrability, size, freeboard and propulsion arrangement may be taken into consideration for the evaluation of the applicability of the requirement for a rescue boat.
If the tug is constantly engaged in warm climates (refer to MSC Circ.1046) where, in the opinion of the Administration thermal
protection is unnecessary, immersion suits need not be carried on board.
An illustrated table describing the life saving signals shall be readily available to the officer of the watch of every tug to all tugs
on all voyages. The signals shall be used by tugs or persons in distress when communicating with life-saving stations, maritime
rescue units and aircraft engaged in search and rescue operations.
July 2014
Bureau Veritas
35
NI 617, Sec 6
SECTION 6
1
1.1
RADIO INSTALLATIONS FOR TUGS OF LESS THAN
300 GT
General
1.2
Requirements for radio installations
1.2.1 Requirements for radio installations are defined in
Tab 1.
Scope of application
1.1.1 This section applies to tugs of less than 300 GT.
Table 1 : Radio installations
tug / escort tug
harbour tug
(unrestricted)
sailing time ≤ 4h from a
safe sheltered anchorage
(in port)
general requirements
≥ 300 gt
SOLAS (A1+A2+A3+A4, as applicable)
X
X
X
< 300 gt
no duplication of equipment required
X
X
X
VHF / DSC
1
1
1
SART (1)
1
1
1
EPIRB / satellite
1
1 (A2+A3)
−
EPIRB / VHF
−
1 (A1)
−
NAVTEX
1
1
−
MF / DSC
1
(2)
−
INMARSAT C
1
(2)
−
GMDSS porto
1
1
−
electrical power supply
1
1
1
specific requirements
(1)
(2)
36
SART is not required if the 406 MHZ EPIRB provided has a 121.5 MHz frequency transmitting capability and is of the non-float
free type for placing in a life raft.
MF / DSC or INMARSAT C depending on region.
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July 2014
NI 617, Sec 7
SECTION 7
1
NAVIGATION EQUIPMENT FOR TUGS OF LESS
THAN 500 GT
General
1.1
1.2
Requirements for navigation equipment
1.2.1 Requirements for navigation equipment are defined
in Tab 1.
Scope of application
1.1.1 This section applies to tugs of less than 500 GT.
Table 1 : Navigation equipment
tug / escort tug
harbour tug
(unrestricted)
sailing time ≤ 4h from a
safe sheltered anchorage
(in port)
X
X
X
general requirements
SOLAS Ch V is to be taken into account for all tugs on all voyages
The administration shall determine to what extent the provisions of
SOLAS Ch V do not apply to the following tugs:
• tugs below 150 gt on any voyage
• tugs below 150 gt not engaged on international voyages (1)
specific requirements
1
1
−
1 (2)
1 (2)
1
gyro compass
1 (2)
1 (2)
−
GPS compass
1 (2)
1 (2)
−
GPS
2
1
1
AIS
1
1
1
radar
magnetic compass
(1)
(2)
nautical charts / ECDIS
1
1
1
daylight signalling lamp
1
1
1
echo sounding
1
1
1
IAMSAR
1
1
1
code of signals
1
1
1
International voyage: voyage from a country to which the SOLAS Convention applies to a port outside such country, or conversely.
Optional 2 out of 3
July 2014
Bureau Veritas
37
NI 617, Sec 8
SECTION 8
1
1.1
HULL OUTFITTING
where:
Anchoring equipment
a
: Distance, in m, from the summer
load waterline amidships to the
upper deck
hi
: Height, in m, on the centreline of
each tier of houses having a breadth
greater than B/4.
Equipment number
1.1.1 The Equipment Number EN is to be obtained from
the following formula:
EN = Δ
2⁄3
+ 2, 0 hB + A ⁄ 10
where:
Δ
: Moulded displacement of the tug, in t, to the
summer load waterline
B
: Moulded breadth, in m
A
: Area, in m2, in profile view, of the hull, superstructures and houses above the summer load
waterline which are within the equipment
length of the tug and also have a breadth greater
than B/4
h
: Effective height, in m, from the summer load
waterline to the top of the uppermost house; for
the lowest tier “h” is to be measured at centreline from the upper deck or from a notional
deck line where there is local discontinuity in
the upper deck.
h = a + Σh i
1.1.2 The equipment length, in m, is the length between
perpendiculars but is not to be less than 96% nor greater
than 97% of the extreme length on the summer load waterline (measured from the forward end of the waterline).
1.1.3 All tugs are to be provided with equipment in
anchors and chain cables, or wire ropes according to [1.2],
to be obtained from Tab 1 and Tab 2, as applicable, based
on their Equipment Number EN. For tugs with restricted
navigation the equipment in anchors and chain cables may
be reduced. For tugs with navigation notation coastal area
the reduction comprises of entering in Tab 1 and Tab 2, as
applicable, one line higher, while for tugs with navigation
notation sheltered area the reduction comprises of entering
in Tab 1and Tab 2, as applicable, two lines higher, as based
on their calculated Equipment Number EN
Table 1 : Equipment for EN ≥ 205
Stockless bower anchors
E.N
38
Stud link chain cable for bower anchors
No
Mass per anchor (kg)
Total length (m)
(1)
205-240
3
660
240-280
3
780
Minimum diameter
Mild steel
Gr. 1 (mm)
Special quality
Gr. 2 (mm)
Extra special quality
Gr. 3 (mm)
302,5
26
22
20,5
330
28
24
22
280-320
3
900
357,5
30
26
24
320-360
3
1020
357,5
32
28
24
360-400
3
1140
385
34
30
26
400-450
3
1290
385
36
32
28
450-500
3
1440
412,5
38
34
30
500-550
3
1590
412,5
40
34
30
550-600
3
1740
440
42
36
32
600-660
3
1920
440
44
38
34
660-720
3
2100
440
46
40
36
720-780
3
2280
467,5
48
42
36
780-840
3
2460
467,5
50
44
38
840-910
3
2640
467,5
52
46
40
910-980
3
2850
495
54
48
42
980-1060
3
3060
495
56
50
44
1060-1140
3
3300
495
58
50
46
1140-1220
3
3540
522,5
60
52
46
Bureau Veritas
July 2014
NI 617, Sec 8
Stockless bower anchors
E.N
Stud link chain cable for bower anchors
No
Mass per anchor (kg)
Total length (m)
(1)
1220-1300
3
3780
1300-1390
3
1390-1480
3
1480-1570
3
Minimum diameter
Mild steel
Gr. 1 (mm)
Special quality
Gr. 2 (mm)
Extra special quality
Gr. 3 (mm)
522,5
62
54
48
4050
522,5
64
56
50
4320
550
66
58
50
4590
550
68
60
52
1570-1670
3
4890
550
70
62
54
1670-1790
3
5250
577,5
73
64
56
1790-1930
3
5610
577,5
76
66
58
1930-2080
3
6000
577,5
78
68
60
2080-2230
3
6450
605
81
70
62
2230-2380
3
6900
605
84
73
64
2380-2530
3
7350
605
87
76
66
2530-2700
3
7800
632,5
90
78
68
2700-2870
3
8300
632,5
92
81
70
2870-3040
3
8700
632,5
95
84
73
3040-3210
3
9300
660
97
84
76
3210-3400
3
9900
660
100
87
78
3400-3600
3
10500
660
102
90
78
3600-3800
3
11100
687,5
105
92
81
3800-4000
3
11700
687,5
107
95
84
4000-4200
3
12300
687,5
111
97
87
4200-4400
3
12900
715
114
100
87
4400-4600
3
13500
715
117
102
90
4600-4800
3
14100
715
120
105
92
4800-5000
3
14700
742,5
122
107
95
5000-5200
3
15400
742,5
124
111
97
5200-5500
3
16100
742,5
127
111
97
5500-5800
3
16900
742,5
130
114
100
132
5800-6100
3
17800
742,5
117
102
6100-6500
3
18800
742,5
120
107
6500-6900
3
20000
770
124
111
6900-7400
3
21500
770
127
114
7400-7900
3
23000
770
132
117
7900-8400
3
24500
770
137
122
8400-8900
3
26000
770
142
127
8900-9400
3
27500
770
147
132
152
9400-10000
3
29000
770
10000-10700
3
31000
770
137
132
10700-11500
3
33000
770
142
11500-12400
3
35500
770
147
12400-13400
3
38500
770
152
13400-14600
3
42000
770
157
14600-16000
3
46000
770
162
(1) The total length of chain is to be divided in approximately equal parts between the two bower anchors.
Note 1: Two bower anchors of the three bower anchors under col. 2 of Tab 1 are to be connected to their cables and positioned on
board ready for use while the third anchor is intended as a spare bower anchor. Installation of the spare bower anchor on board is not
compulsorily required.
July 2014
Bureau Veritas
39
NI 617, Sec 8
Table 2 : Equipment for EN < 205
Stockless bower anchors
E.N
Stud link chain cable for bower anchors
No
Mass per anchor
(kg)
Stock-less stream
anchor (kg)
Total length
(m) (1)
50-70
2
180
60
70-90
2
240
90-110
2
110-130
Minimum diameter
Length
(m)
Breaking
strength (kN)
12,5
80
65
16,0
14,0
85
75
247,5
17,5
16,0
85
80
120
247,5
19,0
17,5
90
90
420
140
275
20,5
17,5
90
100
2
480
165
275
22,0
19,0
90
110
2
570
190
302,5
24,0
20,5
90
120
Mild steel
Gr. 1 (mm)
Special quality
Gr. 2 or 3 (mm)
220
14,0
80
220
300
100
2
360
130-150
2
150-175
175-205
(1)
The total length of chain is to be divided in approximately equal parts between the two bower anchors.
1.2
K
Wire ropes
: Coefficient depending on the service notation
and optional additional service feature, as
shown in Tab 3.
1.2.1 Wire ropes may be used as an alternative two chain
cables as follows:
Table 3 : Equipment coefficient K
• Where L < 30 m, may be replaced with wire ropes of
equal minimum breaking strength, which should:
• Have a length 1.5 times that for chain cable required
by Tab 1, and
• Have a short length of Grade 2/1 chain cable is to be
fitted between the wire rope and the anchor, having
a length equal to 12.5 m or the distance from the
anchor in the stowed position to the winch, whichever is the lesser
• Where 30 m ≤ L ≤ 40 m one chain cable may be
replaced with wire rope meeting the requirements of L >
40 m, while the other chain cable may be replaced with
wire rope meeting the requirements of L < 30 m
• Where 40 m < L ≤ 90 m, both chain cables may be
replaced with wire rope of equal minimum breaking
strength which should:
• Have a length 1.5 times that for chain cable required
by Tab 1, and
• Have a minimum mass per unit length of 30% that
of Grade 2 chain cable required by Tab 1, and
• Have a short length of chain cable is to be fitted
between the wire rope and the anchor, having a
length equal to 12,5 m or the distance from the
anchor in the stowed position to the winch, whichever is the lesser.
1.3
Tugs of less than 500 GT
1.3.1 For tugs of less than 500 GT, the EN may be obtained
from the following simplified formula:
EN = K ( LBD )
2⁄3
service notation
40
: Moulded depth, in m
additional service feature
K
harbour tug
-
1.20
tug
sailing time ≤ 4 h from safe
sheltered anchorage
1.20
tug
-
1.30
escort tug
sailing time ≤ 4 h from safe
sheltered anchorage
1.20
escort tug
-
1.30
1.4
Number of anchors
1.4.1 Tugs are to be provided with equipment in stockless
anchors, chain cables and/or wire ropes. This equipment is
to be obtained as a function of the Equipment Number EN.
The number of anchors, as obtained from the equipment
table depends on the service notation and optional additional service feature, the propulsion arrangement and the
application of a fixed fire fighting installation. In general,
the recommended number of anchors and chain cables is
shown in Tab 4.
Table 4 : Number of anchors and chain cables
service notation
additional service feature
Nr
harbour tug
-
1
tug
sailing time ≤ 4 h from safe
sheltered anchorage
2
tug
-
2
escort tug
sailing time ≤ 4 h from safe
sheltered anchorage
2
escort tug
-
2
where:
D
Stream wire or chain
Bureau Veritas
July 2014
NI 617, Sec 8
1.4.2 A reduction of the number of anchors and chain
cables can be accepted as depicted in Tab 5 if the following
conditions, based on redundancy principles, are complied
with:
1.5.4 The mass of the head, including pins and fittings, of
an ordinary stockless anchor is to be not less than 60 per
cent of the total mass of the anchor.
• The tug is equipped with at least twin propulsion, of
which each main engine can maintain sufficient propulsion power to safely return to berth. For this purpose,
the main engines should be able to run self-supporting,
i.e. independent of generator sets intended for auxiliary
power, unless these are able to run parallel and, in case
of black-out, have automatic starting and connecting to
switchboard within 45 seconds
1.5.5 When stocked bower or stream anchors are to be
used, the mass ‘ex-stock’ is to be not less than 80 per cent
of the mass given in Tab 1 and Tab 2, as applicable, for ordinary stockless bower anchors. The mass of the stock is to be
25 per cent of the total mass of the anchor, including the
shackle, etc., but excluding the stock.
• A single failure, except fire, should not cause total propulsion failure
• A fixed fire fighting installation is provided.
1.4.3 It may be considered by the tug builder and operator
to apply a spare anchor as an alternative to a second bower
anchor. In such case special provisions, such as a crane and
suitable storage space for the spare anchor, are to be
present on board and the weight and dimensions of the
anchor are to be such that it can be handled swiftly. For tugs
with the additional service features sailing time ≤ 4 h from a
safe sheltered anchorage, effectively operating in a fixed
and limited area, the spare anchor may be stored ashore.
additional service feature
-
0
tug
sailing time ≤ 4 h from safe sheltered anchorage
1
tug
(unrestricted)
2
escort tug
sailing time ≤ 4 h from safe sheltered anchorage
1
escort tug
(unrestricted)
2
1.6.2 If approval is sought for a range of sizes, then at least
two sizes are to be tested. The smaller of the two anchors is
to have a mass not less than one-tenth of that of the larger
anchor, and the larger of the two anchors tested is to have a
mass not less than one tenth of that of the largest anchor for
which approval is sought.
1.6.4 The test should normally be carried out from a tug,
and the pull measured by dynamometer or derived from
recently verified curves of tug rev/min against bollard pull.
A scope of 10 is recommended for the anchor cable, which
may be wire rope for this test, but in no case should a scope
of less than 6 be used. The same scope is to be used for the
anchor for which approval is sought and the anchor that is
being used for comparison purposes.
Anchors
1.5.1 Anchors are to be of an approved design. The design
of all anchor heads is to be such as to minimize stress concentrations, and in particular, the radii on all parts of cast
anchor heads are to be as large as possible, especially
where there is considerable change of section.
1.5.2 Anchors which must be specially laid the right way
up, or which require the fluke angle or profile to be
adjusted for varying types of sea bed, will not generally be
approved for normal ship use, but may be accepted for offshore units, floating cranes, etc. In such cases suitable tests
may be required.
1.5.3 The mass of each bower anchor given in Tab 1 and
Tab 2, as applicable, is for anchors of equal mass. The
masses of individual anchors may vary by ± 7 per cent of
the masses given in the Table, provided that the total mass
of the anchors is not less than would have been required for
anchors of equal mass.
July 2014
1.6.1 Anchors of designs for which approval is sought as
high holding power anchors are to be tested at sea to show
that they have holding powers of at least twice those of
approved standard stockless anchors of the same mass.
Nr
harbour tug
1.5
High holding power anchors
1.6.3 The tests are to be conducted on not less than three
different types of bottom, which should normally be soft
mud or silt, sand or gravel, and hard clay or similarly compacted material.
Table 5 : Reduced number of anchors and chain
cables based on redundancy principles
service notation
1.6
1.6.5 High holding power anchors are to be of a design
that will ensure that the anchors will take effective hold of
the sea bed without undue delay and will remain stable, for
holding forces up to those required in this section, irrespective of the angle or position at which they first settle on the
sea bed when dropped from a normal type of hawse pipe.
In case of doubt, a demonstration of these abilities may be
required.
1.6.6 When high holding power anchors are used as bower
anchors, the mass of each such anchor may be 75 per cent
of the mass given in the Tab 1 and Tab 2, as applicable, for
ordinary stockless bower anchors.
1.7
Chain cables
1.7.1 Chain cables may be of mild steel, special quality
steel or extra quality steel in accordance with the requirements of Rules for Materials and are to be graded in accordance with Tab 6.
Bureau Veritas
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NI 617, Sec 8
ing power anchors. Grade 3 material is to be used only for
chain 20,5 mm or more in diameter.
Table 6 : Grades of chain cables
Material
Grade
Range of UTS
(N/mm2)
Mild steel
1
300 to 490
Special quality steel
2
460 to 690
Extra special quality steel
3
> 690
1.7.4 Where stream anchors are used in association with
chain cable, this cable may be either stud link or short link.
1.7.5 The form and proportion of links and shackles are to
be in accordance with the Rules for Materials.
1.7.2 The designation “Grade 1” may be replaced, at discretion of the Society, by “Grade 1a” where UTS is greater
than but not exceeding 400 N/mm2 or by “Grade 1b” where
UTS is greater than 400 but not exceeding 490 N/mm2.
1.7.3 Grade 1” material having a tensile stress of less than
400 N/mm2 is not to be used in association with high hold-
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1.8
Water depths greater than 82,5 m
1.8.1 Where Owners require equipment for anchoring at
depths greater than 82,5 m, it is their responsibility to specify the appropriate total length of the chain cable required
for this purpose. In such cases, consideration can be given
to dividing the chain cable into two unequal lengths.
Bureau Veritas
July 2014
NI 617, Sec 9
SECTION 9
1
ASSISTED SHIP
1.1.7 Given the scope of application of IACS UR A2, careful consideration is to be given to towing fittings to be used
for offshore towage and escorting operations.
Towing fittings
1.1
General
1.1.1 The assisted ship towing equipment is regulated by
the following documents:
• SOLAS Regulation II-1/3-8 Towing and mooring equipment
• IACS UR A2 Requirement concerning mooring, anchoring and towing
• Classification Society Rules
• OCIMF Mooring Equipment Guidelines (can be used for
design purposes).
1.1.2 For emergency towing arrangements, ships subjected
to SOLAS Regulation II-1/3-4 are to comply with that regulation and resolution MSC.35(63).
1.1.3 Reference is made to IACS UR A2 "Shipboard fittings
and supporting hull structures associated with towing and
mooring on conventional vessels".
Note 1: In accordance with IACS UR A1, A1.1.1, the anchoring
equipment required herewith is intended for temporary mooring of
a vessel within a harbour or sheltered area when the vessel is
awaiting berth, tide, etc. In accordance with A1.1.2, the equipment
is therefore not designed to hold a ship off fully exposed coasts in
rough weather or to stop a ship which is moving or drifting. In this
condition the loads on the anchoring equipment increase to such a
degree that its components may be damaged or lost owing to the
high energy forces generated, particularly in large ships
For towing operations in waves, due to dynamic effects, the
maximum towline force may be expected to exceed the
maximum (static) bollard pull by more than 25 per cent (as
considered in the UR A2), in which case a higher SWL of
the towing fittings on the assisted ship would be required.
For offshore escort operations similar considerations apply
with respect to dynamic effects.
In case offshore towing and escort operations are envisaged, it is recommended to apply the Design Load (DL)
specified in Sec 3, Tab 1 and Sec 3, Tab 3, as applicable, for
the towing fittings on the assisted ship.
2
1.1.4 For towage and manoeuvring in port the Design Load
(DL) for towing fittings on the assisted ship is the load
exerted on the considered fitting under the action of the
towline loaded under a tension equal to 1.25 times the
maximum Bollard Pull (BP), as defined in Sec 1, [4.1], in
the most unfavourable anticipated position of the towline.
Note 1: Reference is made to IACS UR A2, Sec A.2.1.3.
1.1.5 The associated Safe Working Load (SWL) is not to
exceed 80 per cent of the Design Load (DL).
Note 1: Reference is made to IACS UR A2, Sec A.2.1.6.
1.1.6 For escort towage the Design Load (DL) for towing fittings on the assisted ship is the load exerted on the considered fitting under the action of the towline loaded under a
tension equal to towline breaking strength according to the
IACS Recommendation No 10 "Equipment" for the ship’s
corresponding EN is to be applied, in the most unfavourable
anticipated position of the towline.
Note 1: Reference is made to IACS UR A2, Sec A.2.1.3.
July 2014
General
2.1.1 To ensure the integrity of the assisted ship side structure during pushing operations, it is recommended that the
pushing forces exerted by the tug are applied on a locally
reinforced side structure of the assisted ship (towing push
point or area).
The maximum applied load (in terms of force and pressure)
by the tug on the assisted ship side structure is to be less
than the design load for that part of the structure.
The strength and size of the reinforced areas of the assisted
ship’s side structure should be designed to take in account
tug motions.
It is recommended to consider the Design Load (DL) specified in Sec 3, [1.9] for the design of the push points/area of
the assisted ship (in combination with a suitable contact
area).
2.1.2 Tug push points/areas should be clearly marked.
The associated Safe Working Load (SWL) is not to exceed
the Design Load (DL).
Note 2: Reference is made to IACS UR A2, Sec A.2.1.6.
2.1
Side structure
2.1.3 The strength characteristics of the assisted ship side
structure (maximum pushing force and pressure) should be
communicated between the tug and the assisted ship.
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43
NI 617, Sec 9
3
3.1
no (or limited) reserve power, which reduces the tug’s ability to escape from a critical situation.
Making fast
General
3.1.1 It is recognised that large and fast ships, in particular
container ships, with high main engine power enter ports at
relatively high minimum speeds of 6 up to 11 kn through
the water and, consequently, that making fast by tugs would
have to be performed at speeds close to the tug’s maximum
speed (typically 11 to 12 kn).
It is also recognised that making fast at high speed incorporates risk for the tug and its crew. Increased ships speed
leads to stronger water flows between and around the ships
and hence increases the risk of collision. In addition, at
speeds close to the tug’s maximum speed the engines have
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It is recommended to explicitly address during the design
stage (of the assisted ship) the minimum speed through the
water (propulsion configuration) as well as the proper location and strength of the towing fittings (bollards, fairleads,
etc.) in relation to connecting to a tug.
Tug owners/operators and port authorities are recommended to specify an appropriate maximum speed for merchant ships in relation to making fast of tugs.
3.1.2 The maximum speed and procedure for making fast
should be communicated between the tug(s) and assisted
ship.
Bureau Veritas
July 2014