API 17TR9: Subsea Umbilical
Termination (SUT) Selection and
Sizing Recommendations
Contents
API 17TR9: Subsea Umbilical Termination (SUT) Selection and Sizing Recommendations ................. 1
1
Scope ............................................................................................................................................... 3
1.1
Introduction .............................................................................................................................. 3
1.2
Document purpose .................................................................................................................. 3
1.3
Use of the Document ............................................................................................................... 3
1.4
Applicability .............................................................................................................................. 4
2
REFERENCES ................................................................................................................................. 6
3
TERMS, DEFINITIONS AND ABBREVIATIONS ............................................................................. 6
3.1
Terms and Definitions .............................................................................................................. 6
3.1.1 .................................................................................................................................................. 6
bend limiter ..................................................................................................................................... 6
(from the UMF Glossary of Terms)................................................................................................... 6
3.1.2 .................................................................................................................................................. 6
bend stiffener .................................................................................................................................. 6
(from the UMF Glossary of Terms)................................................................................................... 6
3.1.3 .................................................................................................................................................. 6
rigid length ...................................................................................................................................... 6
3.1.4 .................................................................................................................................................. 8
subsea termination interface ........................................................................................................ 8
STI .................................................................................................................................................... 8
3.1.5 .................................................................................................................................................. 8
subsea umbilical termination ........................................................................................................ 8
SUT .................................................................................................................................................. 8
3.1.6 .................................................................................................................................................. 8
umbilical Line.................................................................................................................................. 8
3.1.7 .................................................................................................................................................. 8
umbilical termination assembly .................................................................................................... 8
UTA .................................................................................................................................................. 8
3.1.8 .................................................................................................................................................. 8
UTA Yoke......................................................................................................................................... 8
3.2
Abbreviations ......................................................................................................................... 10
API
American Petroleum Institute........................................................................................... 10
FBC
Free Board Clearance .................................................................................................... 10
FEED
Front-End Engineering Design ..................................................................................... 10
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JIP
Joint Industry Project ....................................................................................................... 10
MBR
Minimum Bend Radius ................................................................................................. 10
MQC
Multiple Quick Connects .............................................................................................. 10
OD
Outer diameter ................................................................................................................. 10
Umbilical Manufacturers’ Federation ........................................................................... 10
UMF
UMSIRE
4
5
Umbilical Termination Size Reduction [name of the JIP that created this document]
10
SDU
Subsea Distribution Unit .................................................................................................. 10
SPS
Subsea Production Systems............................................................................................ 10
STI
Subsea Termination Interface.......................................................................................... 10
SUT
Subsea Umbilical Termination ......................................................................................... 10
TR
Technical Report .............................................................................................................. 10
UTA
Umbilical Termination Assembly ..................................................................................... 10
VLS
Vertical Lay System ......................................................................................................... 10
Drivers for UTA Size ....................................................................................................................... 11
4.1
Consequences ....................................................................................................................... 11
4.2
Forward Planning ................................................................................................................... 12
Installation Systems ....................................................................................................................... 13
5.1
Installation Methods ............................................................................................................... 13
5.2
Handling Restrictions ............................................................................................................. 14
5.3
Vessel Implications and Consequences ................................................................................ 16
6
Guidance for UTA Optimisation ...................................................................................................... 19
7
Workflow for Selection and Sizing of the UTA ............................................................................... 22
7.1
Category functionalities ......................................................................................................... 23
7.2
UTA Categorization Method .................................................................................................. 24
7.3
Selection of packing reel or carousel ..................................................................................... 25
7.4
SUT rigid length ..................................................................................................................... 26
7.5
Optimisation Assessment ...................................................................................................... 35
Appendix A: Packing of a UTA with the confines of a reel .................................................................... 36
Appendix B: Fault tree analysis (FTA) ................................................................................................... 39
Appendix C: STI and SUT length calculations ...................................................................................... 42
Appendix D: Steel tube Umbilical or Thermoplastic Umbilical with spool ............................................. 44
Appendix E: False Barrel Diameter calculations ................................................................................... 46
Appendix F: Responsibility Matrix (informative) .................................................................................... 48
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1
1.1
Scope
Introduction
This document was generated, by means of the UMSIRE (Umbilical Termination Size Reduction) Joint
Industry Project (JIP) in response to the increasing difficulties in installation of high-functionality
Subsea Umbilical Terminations (SUTs), due to their increasing size. The JIP committee comprised a
representative cross section of experienced industry personnel from engineering, installation and
operational organisations.
Whilst there are widely accepted standards for the design of a SUT and its sub-systems, none of these
standards specifically address the subject of the risks of installation, and the measures required to
minimise these risks.
The UMSIRE deliverables are two API documents, 17TR9: Subsea Umbilical Termination (SUT)
Selection and Sizing Recommendations and 17TR10: Subsea Umbilical Termination (SUT) Design
Recommendations.
This document is intended to be used as a reference guide by operators, UTA and umbilical specifiers,
installers and FEED companies. It is also intended to be used as a reference document to enable
reviews to be undertaken to ensure that installation risk has been properly considered as part of SUT
design and operations reviews.
This document assumes that the reader has a good level of understanding of the design, engineering
and installation of UTAs. The 17TR10 can be referred for educational purpose and for additional
technical information on UTAs.
The intent with describing these project stages (see Figure 1) is to clarify when within the umbilical
project timeline each UMSIRE document should be referenced, and the interested parties that should
be involved in discussions during each stage.
1.2
Document purpose
This document aims to:
 Highlight technical and commercial risks associated with high functionality umbilicals and
umbilical terminations, especially with respect to installation.
 Describe the implications of decisions made early in the umbilical and SUT planning, selection
and design phases
 Provide guidance on specifications and respective sizes of umbilical terminations.
This is intended to aid the making of informed choices during the early design phase.
The primary aim of this document is to be a reference guide during early field development planning
stage to ensure that due considerations are given to the implications of the size of UTAs and possible
consequences during installation.
The guidelines for the design of UTAs are included in API 17TR10.
1.3
Use of the Document
The users of these Design Recommendation TR’s are primarily intended to be operators, SUT
designers and FEED companies.
Umbilical system design and manufacturing roles and
responsibilities are defined in Annex A.
This document should be read in conjunction with API 17TR10 which aims to provide best practice
technical guidance for SUT design, in order to aid in making informed choices during the design
phase.
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This document has an educational purpose and is intended to be descriptive rather than prescriptive. It
is important to note that none of the following sections should be read in isolation.
1.4
Applicability
In recent years, the size and complexity of umbilical terminations have grown considerably, driven by
increasing subsea power, communication and fluid delivery requirements, as well as the need to
integrate functions normally found on manifolds. Due to some of the existing lay spreads and their long
service life, the equipment has been unable to keep pace with these UTA changes. It also appears
that the difficulties and increased risk implications incurred during installation of excessively large
UTAs are not given the due consideration during early planning stages. Historically in some cases the
design has been such that the UTA cannot be easily deployed when connected to the umbilical by
conventional installation methods.
This emerging trend poses severe challenges to installers and appears to be compounded by the
increased functionality and higher expectations of parties in the supply chain (FEED contractors,
termination designers, operators and manufacturers) This trend has led to occurrences where the SUT
either cannot be installed through conventional lay equipment which results in the necessity for higher
specification lay spreads and vessels and proportionately increased risk to personnel, equipment,
schedule and overall project cost impact.
Without full consideration of these collective impacts this trend of higher functionality and
proportionately larger UTAs is expected to continue.
It is acknowledged that having a separate Subsea Distribution Unit (SDU) may have an impact on the
overall cost. However, the costs of the UTA / SDU alone should not be the deciding factor in
increasing the UTA proportions and weight to achieve an all-encompassing single UTA. Further
analysis should be undertaken throughout the lifecycle of the UTA, which may include the following:
 Packing, transporting and increased installation costs of the larger unit in conjunction with a risk
analysis
 Assessment of the aforementioned factors with detailed examination of the increased risks in
offshore handling, deployment and lay-down on the seabed
This final UTA design approval should be made following close scrutiny of these analyses and
assessments in order to balance costs against increased risk.
The applicability of 17TR9 will be during all stages of UTA concept selection, design and installation.
The figure below shows the applicability of both 17TR9 and 17TR10 by all the parties involved.
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Figure 1: Project stage chart
The intent with describing these project stages is to clarify when within the umbilical project timeline
each UMSIRE document should be referenced, and the interested parties that should be involved in
discussions during each stage.
Readers should be aware that integration of distribution leads to a significant increase in size of the
UTA, although it is required in some cases. For the purposes of this document, it is assumed that the
termination does not provide distribution.
The UMSIRE JIP
Following an Umbilical Manufacturers’ Federation initiative, several major umbilical installation
contractors (Acergy, Saipem UK, Subsea 7 and Technip) and OTM Consulting collaborated towards
the launch of a JIP for the development of two API documents.
These documents address the necessity to optimize the shape, dimensions and overall weight of
UTA’s. The UMSIRE JIP objective is to reduce the size of UTA’s through increased understanding of
the key issues associated with their design, manufacturing and installation, resulting in the
development of a recommended guideline.
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2
REFERENCES
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
API 17TR10, Subsea Umbilical Termination (SUT) Design Recommendations
API Specification 17D, Specification for Design and Operation of Subsea Production Systems
API Specification 17E, Specification for Subsea Umbilicals
API Specification 17F, Specification for Subsea Production Control Systems
3
TERMS, DEFINITIONS AND ABBREVIATIONS
3.1 Terms and Definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
bend limiter
(from the UMF Glossary of Terms)
A device for limiting the bend radius of the umbilical, usually by mechanical means, typically
comprising a series of interlocking metal or polymeric collars designed to lock at a pre-defined radius.
NOTE: This is sometimes known as “bend restrictor”.
3.1.2
bend stiffener (BSR)
(from the UMF Glossary of Terms)
A device for controlling bending strain in the umbilical by providing a localised increase in stiffness;
usually a moulded device, sometimes reinforced depending on the required duty, applied over the
umbilical.
NOTE: This is sometimes referred to as a “bend strain reliever”.
3.1.3
rigid length
The rigid length is the sum the combined lengths of the UTA and STI and any other component that
increases the axial rigid length and cannot easily be removed or re-installed offshore. Depending on
the configuration, rigid length can be calculated by three different ways, as outlined below.
 If the UTA is equipped with a bend stiffener, the rigid length will be the sum of length of UTA,
STI and 1/3 of the length of bend stiffener, as shown in Figure 2
o Rigid length = UTA + STI + (BSR/3)
 If the UTA is equipped with a bend restrictor, the rigid length will be the sum of length of UTA,
STI and the length of 1st interface flange (axial rigid length of bend restrictor), as shown in
Figure 3
o Rigid length = UTA + STI + L
 If the UTA is not equipped with a bend stiffener or bend restrictor, the rigid length will be the
sum of length of UTA and STI, as shown in Figure 6. (Note: It is recommended that either a
bend stiffener or bend restrictor is always used)
o Rigid length = UTA + STI
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Figure 2: Rigid length with a bend stiffener
Figure 3: Rigid length with a bend restrictor
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Figure 4: Rigid length without bend restrictor or stiffener
3.1.4
subsea termination interface
STI
Mechanism that forms the transition between the umbilical and the UTA
3.1.5
subsea umbilical termination
SUT
Mechanism for mechanically, electrically, optically and/or hydraulically connecting an umbilical or
jumper bundle to a subsea system and contains the UTA (Umbilical Termination Assembly) and STI
(Subsea Termination Interface) but does not include bend restrictors or stiffeners.
NOTE Figure 2 illustrates the terminology that will be adopted in the context of the UMSIRE JIP which is aligned
with API’s nomenclature.
3.1.6
umbilical Line
Functional component within the umbilical, providing hydraulic/electrical or optical service
NOTE API 17E states that functional components are hoses, tubes, electric/optical fiber cables included within
an umbilical which are required to fulfil the operational service needs
3.1.7
umbilical termination assembly
UTA
A mechanism for mechanically, electrically, optically and hydraulically, as required, connecting an
umbilical or jumper bundle to a subsea system
3.1.8
UTA Yoke
A frame attached to a UTA, typically at its sides, by hinged or swivelling joints and provided with a
central attachment point for lifting rigging. The yoke allows the UTA to rotate during installation, e.g. in
a “stab and hinge over” mode of deployment where it is lowered vertically until its hinged docking
probe engages with a receptacle on the mounting base, then rotates until landed horizontally as the
umbilical is laid away. Figure 5 and Figure 6 shows UTA with and without a docking probe
respectively.
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Figure 5: UTA without a docking probe
Figure 6: UTA with a docking probe
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3.2
Abbreviations
API
American Petroleum Institute
FBC
Free Board Clearance
FEED
Front-End Engineering Design
JIP
Joint Industry Project
MBR
Minimum Bend Radius
MQC
Multiple Quick Connects
OD
Outer diameter
UMF
Umbilical Manufacturers’ Federation
UMSIRE
Umbilical Termination Size Reduction [name of the JIP that created this document]
SDU
Subsea Distribution Unit
SPS
Subsea Production Systems
STI
Subsea Termination Interface
SUT
Subsea Umbilical Termination
TR
Technical Report
UTA
Umbilical Termination Assembly
VLS
Vertical Lay System
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4
Drivers for UTA Size
The trend of increasing functionality of topside, subsea and downhole equipment over the past decade
has created greater requirements for additional fluid, electrical and optical lines to be routed from the
platform to the subsea equipment. This result in a greater number of functionalities required through
control umbilicals and consequently the UTAs.
A further consequence requiring larger umbilicals results from the lack of sufficient platform J-Tubes
for umbilicals. There is competition for space between umbilicals and production risers, for which the
umbilical is often seen as a lower priority on a basis that one large umbilical is more space efficient
than multiple smaller umbilicals, hence larger umbilicals are envisaged to be the best option during
field development planning.
4.1
Consequences
The increasing size of umbilicals and UTAs due to the drivers identified above, has consequences
related to the design, manufacturing and most importantly during installation of UTAs. The figure below
shows the consequence of increasing size of UTAs (from category A to D, as described in section 7.2)
on the overall risk and complexity of the installation operation and availability of installation vessels,
which has a direct impact on the overall cost.
Figure 7: Consequence of increasing size of UTAs
The consequences in terms of cost, schedule and technical risks are listed below.
 Cost

Oversize terminations often require a bespoke solution leading to “re-inventing the wheel”
syndrome and additional design and engineering

Packing and handling the UTA on a reel may be no longer possible

A carousel equipped vessel or individual carousels may require mobilisation with
additional engineering and mobilisation man-hours

Handling and transportation difficulties
 Schedule

Increase in lead time

Longer fabrication and assembly

Complex FAT – Factory Acceptance Tests

Increase in vessel mob/demob and installation time
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
Limited Installation Vessel availability
 Technical Risk

Together with terminations, bend stiffeners and bend restrictors have grown in size and
weight

Lack of clear definition of acceptable level of risk resulting in over-engineering

UTAs are not properly designed for lifting and over-boarding

Onshore handling heavy UTAs connected to weak umbilicals increases the probability of
damage to the umbilical

Offshore installation of heavy UTAs connected to weak umbilicals substantially increases
the probability of damage to the umbilical and substantial project schedule delays.
The consequences due to increased size of umbilicals and UTAs can also be understood by an
analytical method such as FTA (fault tree analysis). The Figure 18 and Figure 6 shows a FTA
methodology used to highlight the main risks, associated parameters and consequences.
4.2
Forward Planning
During field architecture concept definition and the design phase, consideration must be given for
future expansion and limitations of the field.
Consideration should be made for provision of additional future J-Tube slots for controls umbilicals.
This will mitigate the competition for Umbilical J-Tube slots in the future.
Careful consideration of the number of umbilical functions required (including any functions in line with
the projects sparing and possible expansion requirements) and the resultant installation feasibility
should be made at every stage of the SPS design. Reducing the number of umbilical functions will
reduce the size of the umbilical and UTA installation. Reducing the size of the UTA is encouraged
wherever practical.
UTAs can be installed and recovered independently of their support frame or SDU and incur simpler
interface points with which to dock and engage the UTA onto the support/SDU. Multi-bore hubs can
bring all the required functions to the SDU where the full function distribution and outlet ports are
incorporated within. If an additional SDU installation is required, it can:
 Enable a much simpler deployment of SDU and umbilical individually
 Alleviate complex handling
 Mitigate much of the installation/recovery and/or re-installation risks
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5
5.1
Installation Systems
Installation Methods
There are several industry standard umbilical installation methods such as;
1. Horizontal lay tensioner and over-boarding chute for low tension installation.
2. Horizontal lay tensioner with vertical over-boarding system for low/medium tension
installation of umbilicals with ancillary components such as buoyancy modules, clamps, bend
restrictors, etc
3. Closed Vertical Lay System for general installation of umbilicals including those with higher
top tension. These systems have limitations due to UTA having to pass through the closed
tensioner aperture.
4. Open Vertical Lay System for general installation of umbilicals including those with higher
top tension. These systems do not have limitations due to UTA having to pass through the
closed tensioner aperture.
5. Rigid Pipe Lay Systems (open or closed) used for installation of umbilicals, normally as part
of rigid pipelay installation.
More detailed descriptions of the above installation methods are presented in API 17TR10
Chapter 9. Figure 8 and Figure 107 show the typical operational sequence and geometric limitations
of a VLS system.
Figure 8: Vertical Lay Installation, first end (Source: Technip)
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Figure 9: Vertical Lay Installation, second end (Source: Technip)
5.2
Handling Restrictions
The following factors should be considered during SUT design to best comply with handling
constraints and requirements of the SUT and Umbilical Installers:
1
Factor
UTA width and height
2
Handling points on UTA considering installation
through the lay system and sea-fastening
3
Weight and centre of gravity of UTA
4
SUT total rigid length
5
UTA and umbilical structural design
6
Umbilical length & weight
7
Design of UTA bend stiffeners and UTA yokes
9
Installation of mudmats or support structures
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Reasons for Importance
Ability for UTA to pass through tensioners
and deck openings.
Ability to accommodate UTA on reels and
on carousels.
Sea-fastening design, deck handling, lift
planning and lift rigging design.
Overboarding operations.
Deck handling, lift planning and lift rigging
design.
Overboarding and landing operations.
Ability to accommodate UTA on reels and
on carousels.
Ability to lift UTA over arch and into VLS.
UTA design to withstand the loads
imposed during handling and installation.
UTA design to withstand the loads
imposed by the umbilical during handling
and installation.
Ability to accommodate UTA on reels and
on carousels.
Ability to lift UTA over arch and into VLS.
Deck handling, lift planning and lift rigging
design.
Overboarding and landing operations.
Design of UTA docking facilities, latching
arrangements and support structures.
14
9
Factor
Critical installation parameters
 Maximum umbilical tension < allowable
value
 Maximum umbilical compression <
allowable value
 Umbilical MBR > allowable value
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Reasons for Importance
Compliance with product integrity
15
5.3
Vessel Implications and Consequences
The installation-related consequences of increasing UTA size include the following, and more:
Consideration
1
Safety Implications
1a
Danger in handling a large / heavy
load at height.
1b
Danger from vessel motions
caused by the sea state.
2
Cost (associated with vessel
capacity)
2a
Reel/Carousel capacity
2b
Required tensioner length / VLS
capacity
2c
Handling method requirements
3
Schedule
3a
Vessel availability
3b
Safe handling weather window
3c
Geographical location
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Explanation and Potential Consequences
The larger and heavier the UTA the higher the risk
factors with regard to safety of personnel and the
product(s) (UTA and umbilical). This applies onshore as
well as offshore.
If UTA proportions are out-with Installation Vessel crane
and handling equipment capacity it may necessitate a
Port Call to enable quayside crane intervention (first end
lay) or 2nd vessel crane (first or second end lay).
If the sea state is worse than that acceptable for safe
handling of the UTA there may be delays associated
with waiting for improvement or else sailing to port or
sheltered water.
Increasing UTA proportions size leads to increased
handling complexity resulting in the need for higher
specifications for installation systems (and vessels)
along with additional UTA handling and deployment
equipment.
Influenced by UTA functionality, umbilical length, water
depth, weight of umbilical, MBR and rigid length.
Increasing capacity requirements can lead to restricted
choice of vessel, more expensive vessel, or additional
port-calls and re-mobilisations.
Choice of tensioners and laying system is driven by top
tension (SUT dimensions / weight, umbilical weight,
water depth) and installation method. More onerous
demands on VLS / Lay System capability can lead to
restricted choice of vessel specification and charter
costs.
A need to handle a larger / heavier UTA tends to result
in a need for higher rated equipment, more items of
equipment, more complicated equipment - all leading to
greater cost.
Consequences of handling a large / heavy load at height
has been described in item 1a.
Increasing the UTA size tends to increase the risk of
extension to schedule due to complexity in handling,
intervention and installation. It is possible for a small
growth in size to cause a large schedule impact.
A restricted choice of vessel can lead to schedule delay
owing to the reduced availability of suitable vessels.
Such a restricted choice could be caused by the need
for a VLS, an open tensioner VLS or a larger capacity
carousel.
The acceptable weather conditions for UTA and
umbilical installation will be diminished and less frequent
as UTA size increases or umbilical strength decreases,
resulting in project schedule delays.
A large UTA can result a restricted choice of vessel
could result in schedule delay owing to transit time for
suitable vessel to the work locations.
16
Consideration
4
Technical Risk
4a
Technical Risk Reliability
Explanation and Potential Consequences
The technical risks associated with UTAs are likely to
increase with their size, with consequent safety,
reliability, cost and schedule implications.
Increased functionality can have implications on long
term reliability
Water Depth
It is considered that at larger water depths compared to shallow waters will lead to the following:
o
o
o
o
the top tension will increase with a potential consequence to laying spread
the crane / winches involved will have to reach deeper and possibly will require higher
capacity
the structure of the umbilical will potentially have to be more robust, i.e. possibly
heavier and more expensive
The time to deploy and install the umbilical system is likely to increase
Limiting Sea state
A higher limiting seastate (Hs) gives increased flexibility in terms of schedule and planning, as well as
less exposure to reduced weather windows.
A low limiting seastate may give constraints in installation methodology, risk of waiting on weather, risk
to product during installation, etc.
Type of laying system
The optimum scenario is that the umbilical system can be installed with any available system (i.e over
the stern, open / closed VLS, other – ref. API 17TR10 Section 9.4 for description of laying systems). In
a less than optimum scenario, the umbilical system can only be installed by certain systems, e.g. open
VLS if the UTA is very large etc. or for purpose built systems.
The type of laying system still depends on the choice of the installer and the vessel spread availability.
It should also be noted that various geometrical constraints linked with the various laying systems may
influence the optimal choice of system. (Ref. Section 9 of API 17TR10)
Rigid Length
The total rigid length of the UTA assembly is defined section 3.1.3 with examples on figures 2, 3 and 4.
A longer length of UTA is worse for handling and installation through laying systems due to
geometrical constraints when interfacing and passing through these systems. Rigid lengths above a
certain length may not be installable using standard methods. Reference is made to Section 6.11 of
API 17TR10.
A shorter length of UTA is preferable for handling and installation, also may improve the choice of
alternative laying systems available.
Minimum Bending Radius
The limiting minimum bend radius (also referred to as allowable bending radius, varying with various
stages of the operation) is less than optimal when a large radius is required, as this has a direct impact
on vessel layout, lay spreads, installation methods, complexity etc. A smaller limiting radius gives
increased flexibility versus handling and installation.
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SUT Weight
Very heavy SUTs are less practical from handling point of view, versus vessel lay spreads, cranes and
winches, safety of product and personnel. Special installation aids, installation methods and
installation spreads may be required.
Size of foundation structure
The foundation structure (folded / open mud mats, support structure, etc) will increase the total size of
the assembly and is either installed with the umbilical at launch or connected to the umbilical / UTA at
the seabed. A larger UTA will require a larger size of foundation is therefore worse for handling on
deck and for launching through the moon pool and through the water column.
A smaller and more compact foundation structure or pre-installed design (on seabed) is more
favourable in terms of handling and installation and induces less risk on the umbilical and UTA
deployment.
Installation Vessel Time Line
The time taken from UTA definition to offshore installation can influence the choice and availability of
vessels and laying systems availability. A short time to plan and execute the operation may be worse
in terms of vessel availability and choice of laying systems, while a longer time period between design
and UTA completion may give increased flexibility in terms of schedule and planning.
Delivery method
In the best case scenario, all packing systems can be utilized for transport and installation, i.e.
baskets, reels or internal / external carousels etc. In the less than optimal case where the umbilical is
particularly long or UTA is unreasonably large, only particular packing systems can be used e.g. an
external carousel and open tensioner VLS system.
Installation Complexity
In a less than optimal case, the standard available laying systems are not suitable to install very large
and complex UTA / umbilical systems, moon pool may not be large enough, etc. In such a case,
specially engineered installation systems may be need to be designed and fabricated for use onboard
the installation vessel to comply with complex handling and installation requirements – with the
consequence of increased schedule and cost impact.
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6
Guidance for UTA Optimisation
The size of the UTA can have enormous impact on the duration and cost for the installation of
umbilical’s and its UTA’s large/ complex UTA size can cause:





Bespoke, time consuming installation methods and costly onshore trials
Specific requirements on installation vessel and equipment
Reduced installation window due the limited acceptable environmental installation condition
Limited availability of suitable installation vessels
Time consuming and complex packing, transporting, mobilisation and offshore deployment
As the impact of the UTA size can be significant, it is recommended to perform an optimization of the
UTA size during the conceptual definition phase of the system layout. The optimization model provides
the method of optimizing the size of the UTA during the concept stage of the development of a system.
The model provides the opportunity to perform an optimization of the UTA size considering key
aspects of the system layout.
The model is structured in three elements:
 Optimization process
 Key Optimization Aspects
 Optimization Matrix
6.1
Optimization Process
Once the first draft of the system is present the optimization can be started based on the following
process below in combination with the information of the earlier chapters of this document. After each
of the optimization process steps the key system questions should be answered and documented
within the optimization matrix. Once modifications of the UTA and/ or system have been implemented,
the process shall either be continued at the same level or re-started at one of the previous levels.
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System Functional Design Requirements
UTA OPTIMIZATION
“System layout versus UTA size”
Figure 10: UTA optimisation process
6.2
Key Optimization Aspects
During the concept phase for the development project not all details about the proposed equipment
are available. Due to that, the optimization process concentrates on a few key aspects. These aspects
are:
 Field architecture,
o Arrangement of drill centres and system layout
o Umbilical system and umbilical function
o Field environmental conditions, e.g.: seabed load-bearing capacity, tide, sea state,
visibility condition
o Use of SDU in conjunction with UTA
 UTA Functionality
o Termination of the umbilical services
o Distribution (e.g.: teeing of lines, electrical distribution units etc.)
o Isolation, reconfiguration option (gate/ ball valves, logic caps)
 Line Size
o Flow-assurance
o Bending radius
 Spare philosophy
o Number of spare lines/ cables
o Accessibility of spare lines
 Level of technology New technology development
 Qualification (for product and/ or system)
 Foundation arrangement
o Type of foundation structures (e.g. mudmat, suggestion pile, single or combined
foundation
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o
Installation method (combined or separate, permanent attached, disconnectable
subsea)
In early conceptual and front end engineering phases of field layout, strong consideration should be
given to the number of wells to be served by a single umbilical. This directly influences the required
number of functional elements in the umbilical, and ultimately is truly what governs the size of the
UTA. Limiting the number of functional elements to a practical amount is a preferred method of
limiting the size of a UTA, as opposed to limiting or eliminating the ability to utilize spare lines or
compromising on design reliability with respect to materials of construction, minimum bend radii, and
the number of welded fittings.
6.3
Optimization Matrix
The optimization matrix below has been developed:
 to perform the optimization process systematically
 to gain overview and awareness which system design aspects influence the UTA size/
complexity
 to document the decisions/assumptions being made during FEED/ tender stage
This matrix should be used during all the stages of the optimization process. For the different process
steps, the matrix can be extended as needed, as this list is not exhaustive.
Key Aspects
Why is the
UTA large/
complex?
Can the size /
complexity be
reduced? Yes?/No?
Process step:
Consideration of
installation
aspects
Process step:
Evaluation of
packing option
Process step:
: UTA
Categorization
Field architecture
UTA Features
Line Size
Sparing philosophy
Level of technology
Foundation
arrangement
Field architecture
UTA Features
Line Size
Sparing philosophy
Level of technology
Foundation
arrangement
Field architecture
UTA Features
Line Size
Sparing philosophy
Level of technology
Foundation
arrangement
If yes, HOW?
If not: WHY?
Table 1: Optimization matrix
Upon completion of this process, the UTA size should be optimised as much as the system allows.
The matrix also provides an overview of the aspects which influences the system layout aspects, size
and complexity of the UTA.
During project execution, the matrix should be used to develop mitigation plans when the size and
complexity can be optimised no further. This should instigate critical activities such as development
work, qualification, vessel selection to address the challenging installation scenarios.
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7
Workflow for Selection and Sizing of the UTA
The aim of the workflow is to guide the user through a sequence of steps, to understand the
implications of the decisions made during early design phase. The workflow comprises of selection of
UTA category and packing, followed by an optimisation assessment leading to optimised UTA size,
design and installation. Figure 11 below shows the five sub-components of the workflow.
• Category Functionalities
• UTA Categorization Method
• Selection of Packing Reel/ Carousel
• SUT Rigid Length
• Optimisation Assessment
Figure 11: Workflow of the selection and sizing of the UTA
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7.1
Category functionalities
Table 2 below indicates typical maximum functionalities that can be specified for each category of
UTA, with the categories defined as in Figure 9 of section 7.2.
UTA
Functionalities
Category A UTA
To fit Closed
Tensioner Aperture
Ø
Category B UTA
Category C UTA
Category D UTA
1.2 m
1.4 m
1.6 m
>1.6 m (requires an
open tensioner)
MQC Plates
2 MQC plates with 7
lines each (2 up to
3/4''OD and 5 up to 1/2''
OD)
2 MQC plates with 10
lines each (4 up to
3/4''OD and 6 up to
1/2''OD)
4 MQC plates with a total
of 24 lines (maximum of
4 up to 1’’OD, 8 up to
¾’’OD and 12 up to
½’’OD)
>4 MQC
Cables
A total of 6 optical and
electrical umbilical
cables each terminating
to a single connector, of
which a maximum of 2
are fiber optics.
6 electrical umbilical
cables each terminating
at a single connector,
and 2 fiber optic
umbilical cables each
split into 3 connectors
6 electrical umbilical
cables each terminating
at a single connector,
and 2 fiber optic umbilical
cables each split into 3
connectors
More than 6
electrical umbilical
cables each
terminating at a
single connector,
and more than 2
fiber optic umbilical
cables each split
into 3 connectors
Valves
No
No
Not recommended
Possible
Distribution
No
No
Possible
Possible
Max. UTA length
(including the
padeye)
3m
3m
3.5 m
>3.5 m (depending
on handling
limitations)
ROV operable
Yes
Yes
Yes
Yes
Note: The UTA length may exceed theses recommended values while optimizing the all-over length of the SUT or rigid length
with the length of the STI and bend limiter properties.
Table 2: Functionalities of UTA categories A, B C and D
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The table below gives an indication of typical STI dimensions.
UTA Category
Total STI Length
(mm)
Max STI flange diameter (mm)
Minimum interface aperture in UTA
(mm)
X
Y
Recommended
Default
Z
Recommended
Default
A (steel tube)
1175 - 1400
650-710
ASME/ANSI
B16.5
Class 300 – 20”
390 - 432
20” (510mm)
A
(thermoplastic
hose)*
370*
650*
ASME/ANSI
B16.5
Class 300 – 20”
390*
20” (510mm)
B (steel tube)
1250 - 1800
775
ASME/ANSI
B16.5
Class 300 – 20”
480 - 550
20” (510mm)
B
(thermoplastic
hose)*
420*
650*
ASME/ANSI
B16.5
Class 300 – 20”
390*
20” (510mm)
C (steel tube)
1300 - 1900
770 - 838
ASME/ANSI
B16.5
Class 300 – 20”
490 - 550
20” (510mm)
C
(thermoplastic
hose)*
510*
650*
ASME/ANSI
B16.5
Class 300 – 20”
390*
20” (510mm)
* Thermoplastic hose STI dimensions are examples from one umbilical designer only
Table 3: Ranges of STI dimensions advised by umbilical designers
The table gives an indication of typical STI dimensions where it has not been possible to integrate the
STI into the main UTA body. In some cases STI may be integrated in the UTA, thereby the length of
STI will be much shorter than the indicative figures in the table above.
The total STI length may include the first joint in the bend restrictor interface when it is included as a
machined part of the armour body. The total rigid length includes this interface as shown in Figure 3.
7.2
UTA Categorization Method
This section described the methodology for UTA size categorization adopted by the UMSIRE JIP.
UTAs have been classified into four categories depending on the limiting factors of installation
systems. Each category of UTA has been based on the level of functionality that can be incorporated
within each envelope as described in table 2
UTA Categories
Four UTA categories are defined as follows:
 Category A: up to 1.2 m closed tensioner diameter
 Category B: up to 1.4 m closed tensioner diameter
 Category C: up to 1.6 m closed tensioner diameter
 Category D: >1.6 m (requires open tensioner)
The categories are defined by the closed tensioner aperture as shown in the diagram below. The UTA
cross-section must stay within and be free to rotate within the circle enclosed by the aperture. Figure
12 shows a 4-track tensioner, although other designs exist in the industry.
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Category
Tensioner
opening
A
≤ 1.2m
B
≤ 1.4m
C
≤ 1.6m
D
> 1.6m
Figure 12: Closed Tensioner Opening
Clearance must be considered to allow the SUT to pass through the tensioner without issue. Certain
items may be temporarily removed to allow the SUT to pass freely through the tensioner. The
minimum radial clearance to tensioner aperture should typically be 50mm (for category A to C),
depending on geometrical layout and handling constrains (ref. Figure 12).
Certain items, such as protective covers, may be temporarily removed to allow the SUT to pass freely
through the tensioner.
7.3
Selection of packing reel or carousel
Figure 14 below shows the methodology for selection of packing. The selection is based on three main
criteria, if all three criteria meet the specifications, the installation using a reel will be more favourable.
The total system weight refers to weight of umbilical, fluid, terminations, reel (including cradle and the
partitions. The maximum rigid length check and the umbilical length check can be carried out with the
help of calculations such as described in Appendix B.
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UTA Category (Table 1)
Tensioner Type (Figure 7)
A
B
C
CLOSED / OPEN
(350 tonne typical , 350 to 500 tonne special case only
Total
System Weight
Check
< 350 tonne
D
OPEN
No
Yes
No
Max rigid
Length check
Equation 2
Yes
No
Yes
A to D
Umbilical Length
Check
Equation 3
Installation
Reel
Vessel
Carousel
Figure 13: Flow chart for selection of packing reel/ carousel
Equation 2 and equation 3 have been included in Appendix C.
7.4
SUT rigid length
The SUT rigid length is calculated based on the UTA dimensions and the STI length. The UTA
dimensions are obtained from section 7.1 and the following section describes STI length calculations.
Figure 14 shows the rigid length with a bend stiffener connected with the STI. As described in section
3.1.3, the rigid length will differ in other cases depending on if the SUT is connected with either a bend
stiffener or a bend restrictor, or none of them.
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Figure 14: Rigid length
The maximum permissible Rigid Length should be considered for two operational cases; storage and
as installed.
Storage Rigid Length - The total length of the UTA taken from the end of any padeyes or hold down
points plus the STI (if not incorporated into the UTA) with the Bend Restrictor or BSR not attached.
This will allow a longer UTA to be stored on the reel prior to deployment.
As Installed Rigid Length - The total length of the UTA taken from the end of any padeyes or hold
down points plus the STI (if not incorporated into the UTA) plus the Bend Restrictor interface or 1/3 rd
BSR length installed in position. This allows overboarding and deck handling requirements for the
different lay methods to be reviewed with the umbilical in the installed condition. The remaining Bend
Restrictors elements are attached prior to overboarding in a suitable location as determined by the
installer.
Further details on rigid length and STI have been provided in section 6.11.1 of API17TR10.
STI Length Calculation
The formulas for calculating length of STI have been included in Appendix C (STI and SUT length
calculations). The formulas are intended to provide an initial sizing of the STI length based on the reel
diameter, umbilical (MBR & diameter) and UTA size (L & H).
Some of the important assumptions incorporated in the calculation method are as follows:

The umbilical MBR should be equal or greater than the reel barrel radius

The UTA is box shape (side view) and does not have large extending brackets or component’s on
the top, base or front

The free board clearance (FBC) is the same for both the umbilical and UTA

Packing configuration as per Error! Reference source not found.
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The rigid length in Error! Reference source not found. is indicated as the sum of the length of UTA
and STI, without a bend stiffener or a bend restrictor. If a bend stiffener or a bend restrictor is used, the
rigid length will be different, as described in section 3.1.3.
Note: It is recommended that a bend stiffener or a bend restrictor is always used.
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Figure 15: UTA packed within reel flanges (to allow 2nd end lay)
The maximum STI length can be obtained from figure 11 or can be calculated by using the equations
mentioned in Appendix B.
In some cases the barrel radius can be increased by adding a suitable packing structure to increase
the barrel radius. This may also be extended into both bay A and bay B, (as shown in figure 14 and in
Appendix E).
Figure 16: Illustration to show increased barrel radius by using packing structure (size view)
Equation 4 in Appendix E contains the details of false barrel diameter calculations and the symbols
used.
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Figure 17: Illustration to show increased barrel radius by using packing structure (front view)
Table 4 shows the maximum STI lengths based on UTA categories, umbilical MBR and reel size. The
table provides guidance for STI lengths based on MBR range between 1-4 metres. For specific project
requirements the user can refer to the length equations in Appendix C.
The main purpose of the table is to act as a quick reference guide for checking whether the results of
preliminary evaluation of umbilical length and the UTA dimensions will fit on the desired packing (reel/
carousel). The range of MBR, reel diameter and barrel diameter in the table has been chosen on the
basis of project experience, with an aim to provide an example of how such an exercise could be
conducted. The recommendation to the reader of the document is that an equivalent table must be
constructed for field specific requirements and range of possible umbilical and UTA dimensions.
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The table can prove to be a useful and flexible tool which can be adjusted depending on project
specific conditions, drivers and requirements.
The aim of the table is not to act as a comprehensive guide, but to be used as an approach for making
a systematic methodology which can be effectively used on projects. The table can be expanded or
modified to suit individual project requirements.
Table 4 refers to technical terms such as reel, false barrel. A reel used for umbilical storage,
transportation or installation has a cylindrical barrel fitted with larger diameter flanges at each end. An
intermediate circular partition may be provided to divide the usable space on the reel into two
compartments: one of which may be used for storing the main quantity of umbilical and the other used
for containing a UTA. The partition is provided with a cross-over gate (aperture) to allow the umbilical
to pass between one compartment and the other. A false barrel may be fitted to increase the effective
central diameter of the reel when its use is dictated by the minimum bend radius of the umbilical being
carried. The edges of the flanges are reinforced to allow the reel to rest on deck or underrollers. The
barrel usually projects slightly outboard of the flanges to allow slings to be passed round it for lifting
purposes.
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Rigid length (Lrigid)
UTA Size Category
Reel (m)
Ø Rim Ø Barrel
6
2.0
3.0
7
3
4
8.6
4
5
6
9.2
4
5
6
9.8
4
5
6
11.2
4
5
6
8
11.4
5
6
8
(…..)
(…..)
A
B
C
Umbilical MBR range (m)
Umbilical MBR range (m)
Umbilical MBR range (m)
1.0
3.37
3.37
4.4
3.37
4.4
4.4
3.37
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
2.5
(4.4)
3.37
3.37
(4.4)
4.4
4.4
(4.4)
4.4
4.4
(4.4)
4.4
4.4
4.4
4.4
4.4
4.4
4.0
(4.4)
(4.4)
3.37
(4.4)
(4.4)
3.37
1.0
3.42
3.42
3.42
4.8
4.8
3.42
4.8
4.8
3.42
4.8
4.8
4.8
4.8
4.8
4.8
4.8
4.8
4.8
4.8
2.5
4.0
1.0
2.5
4.0
4.01
(3.42)
3.42
5.4
4.01
(4.01)
4.01
(4.8)
4.8
3.42
(4.8)
4.8
4.8
(4.8)
4.8
4.8
4.8
4.8
4.8
4.8
5.4
5.4
4.01
5.4
5.4
5.4
5.4
5.4
5.4
4.01
5.4
5.4
5.4
(4.01)
4.01
(3.42)
(4.8)
(4.8)
3.42
(4.8)
(4.8)
3.42
(5.4)
5.4
4.01
(5.4)
5.4
5.4
4.01
(5.4)
5.4
4.01
(5.4)
(4.01)
(4.01)
(5.4)
(5.4)
4.01
Steel tube or thermoplastic STI
Steel tube or thermoplastic STI, umbilical requires false barrel
Thermoplastic STI only
Thermoplastic STI only, umbilical requires false barrel
Insufficient space for STI & UTA or MBR
Table 4: Variation of rigid length with varying reel diameter and UTA size category
Note: Rigid length is calculated from the combined maximum values for STI length from table 3 & UTA
length from table 2.
The dimensions given in Table 4 are the maximum rigid lengths that can be used for either steel or
thermoplastic umbilicals for a given UTA category and MBR.
The two examples below show how the above approach can be used. The Table 4 can be used in two
ways:
Example 1
If the available option has restricted the maximum reel diameter to 9.2m and have a 2.5m MBR steel
tube umbilical fitted with category “C” UTA:. It can be seen from the table the only option available is a
thermoplastic umbilical due to the maximum rigid length of 4.01m.
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Notes:
1. A steel tube option maybe possible, however it will need to be designed within the 4.01m rigid
length
2. If the barrel diameter is less than 5m, then a false barrel will be required
3. A larger diameter reel may be required to accommodate the actual umbilical length.
Example 2
If the available option is to have a 2.5m MBR steel tube umbilical fitted with category “C” UTA: the first
available reel diameter is 9.8m with a 5m barrel.
Notes:
1) A 4m barrel could be used with a false barrel.
2) A larger diameter reel may be required to accommodate the actual umbilical length.
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7.5
Optimisation Assessment
The optimisation assessment aims to guide the user through the process for optimising the process of
installation of umbilical and UTA. The methodology takes into account several factors such as the
environmental conditions (water depth, sea state), installation system, size and weight of the structure.
The aim of this table is to provide guidance to the user for being aware of the consequences of UTA
size relating to optimisation and installation operation. The table should be used to assess the
implications in terms of cost, schedule and risk.
Table 5: Optimisation assessment
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Appendix A: Packing of a UTA with the confines of a reel
Design considerations:
Packing Design
When considering the packing of a UTA within the confines of a transport / installation reel, the design
engineer shall assess the methods required for packing onshore and un-packing offshore with
consideration to the following:

Safe access to ALL rigging when onshore and offshore with zero or minimum at height working

The project offshore lifting standard and certification requirements

UTA, 1st and 2nd end lay, note 1st lay could be position outboard of the reel

Reel Hub Drive system or under roller

Working clearance between UTA and reel compartment sides

Load rating / testing of the reels UTA support structure and rigging attachment points

Routing and anchorage of the umbilical

Positioning of bend stiffeners or limiters and anchorage, with particular attention to long term
bending of bend stiffeners

Design of rigging considering dynamic and rotational acceleration

Clearance of the umbilical and UTA from reel rim and driving system

2nd end hold back anchorage of the UTA and umbilical or cable, with particular attention of both
tension and compression of the umbilical or cable at the point of partition cross over

Environmental protection of partially dis-assembled equipment

Accessibility to install and use pressure & electrical monitoring equipment

Reel weight distribution

Radial offset weight balance of the reel for lifting and rotation

Reel lifting beam / rigging offset loading

Packaging of removed equipment i.e. ROV grab bars, dummy connectors etc

Drawings and procedures
Reel and Drive System
Reels shall be sized for the total weight of the umbilical, UTA (s) and all ancillary equipment, the
designer should also consider the following:
Load distribution of product on the reel and lifting equipment, to ensure compliance with the reel
load / test certification

Un-even balance

Drive system, where under rollers may extend beyond the inner edge of the reel rim

Low support structures, where access may be limited due to reel support cradles

Structural strength of the rigging points

Not welding rigging points to critical structural members of the reel
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UTA Support Structure
The UTA support structure should be designed with consideration to the following and the prevailing
offshore lifting standard and certification requirements:
The structure should be easy to install and ideally adaptable to allow for a UTA loading tolerance

Ideally the structure should be designed and positioned to remove the need for disassembly
offshore

If removal is required offshore, adequate lifting points should be provided and component weights
marked

If the structure has to be welded in position after the UTA is positioned, adequate protection
should be used to prevent damage to the UTA and umbilical
Rigging Equipment
All rigging equipment should be designed to prevailing offshore lifting standard and certification
requirements and consideration of the following:
Dynamic loading of the rigging and pad eyes

Generally chain falls (chain block hoists) are the preferred lifting / lowering system offshore, this
allows the deck crew to work at deck level and clear of the descending UTA

Ratchet lever hoists are generally used to rig fore and aft of the UTA

Once installed chain falls and ratchet lever hoists should have chain lockers attached to secure

Long term effect of high grade steel rigging in an offshore environmental
Umbilical Routing
The routing of the umbilical should consider the following:

Maintaining the MBR

Preventing damage to the outer sheath or roving from chafing, axial moment or over tightening of
the securing system

Stored energy in umbilical or cable when released

Future intervention, removal and decommissioning should be considered when considering the
routing of the umbilical
Bend Stiffeners
Consideration shall be given to the amount of bending the bend stiffener is subjected to and the
duration; typically to prevent a permanent set a bend stiffener should not be bent for more than the
maximum period specified by the manufacturer.
As a rule thumb the bend stiffener should not be bent more than a 1/3 of its length for packing
purposes, in all cases the bend stiffener manufacturer must advise the amount of bend vs. duration.
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Monitoring Systems
Monitoring systems used for shipping and or installation lay should have good access for installation of
the equipment and monitoring. When used for shipping the monitoring part of the system should be
positioned at ground / deck level to provide easy access on route.
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Appendix B: Fault tree analysis (FTA)
FTA is one of the most widely used methods in system reliability, maintainability and safety analysis.
The main drivers for using FTA are to be able to conduct a thorough examination the factors which
may lead to a system failure or accident. The process identifies the causes of a failure, to identify the
weakness in a system, to prioritize contributors to failure, to identify effective upgrades to a system, to
quantify the failure probability and contributors, and to optimize tests and maintenances.
FTA is a deductive technique where users start with a specified system failure or an accident, known
as the top event of the fault tree. The immediate causal events A1, A2, … that, either alone or in
combination, may lead to the top event are identified and connected to the top even through a logic
gate. Next, all potential causal events Ai,1, Ai,2, … that may lead to event Ai for i = 1, 2, 3, … are
identified. These events are connected to event Ai through a logic gate. This procedure is continued
deductively until a suitable level of detail is reached. The events on the lowest level are called the
basic events of the fault tree.
The 1st FTA (Figure 18) demonstrates that “sea state” event and the undeveloped “SUT size”
contribute to increase project costs. The 2nd FTA (Figure 19) develops the “SUT size” and mentions a
number of contributory factors to the size of the SUT.
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FTA - project costs
Operator point of view
Increased project
realization time
Increased
installation time
Limited installation
window
Sea state
Heavy / large
vessels
Large reels / caroussels /
lifting equipment
Decreased vessel
availability
Heavy / large
vessels
Increased material
handling time
Decreased vessel
availability
Manufacturing /
Equipment
Large reels /
caroussels /
lifting
equipment
Health &
safety
issues
Personnel
safety
Large / long umbilicals
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2013
SUT
40
Repair of
complex
equipment
damaged
Supply:
vessel,
cranes,
etc
Excessive
# of hours
Technical
risks
Components
costs
Sea state
Large reels /
caroussels /
lifting
equipment
Sea state
Large /
long
umbilicals
& SUT
Increased
material
handling time
Engineering
Large / long
umbilicals &
SUT
Large reels /
caroussels /
lifting
equipment
Large / long
umbilicals &
SUT
Time to
soucre,
specify
Large / long
umbilicals & SUT
Quantity /
complexity of
components
Large / long
umbilicals & SUT
Large / long
umbilicals &
SUT
Figure 18: FTA step one
Large / long umbilicals &
SUT
Excessive # of
functions / interfaces
Over
engineering
Personnel
experience /
training
Specifications
lacking or not
followed or
excessive
Lack of industry
standardisation
Missing field
return
reliability data
Maximum # of
functions / interface
per umbilical / SUT not
defined
Figure 19: FTA step two
The FTA methodology has been chosen to give an indication of an analytical approach that could be
used to gain a better understanding of the risks and consequences of excessive size of UTAs. The
choice of using FTA was driven by the following factors.

FTA is specified in a number of reliability related manuals, such as US ARMY
HEADQUARTERS Design for Reliability Guide (1976), each investigative method (FMEA,
FTA, RBD, etc) will identify measures to be taken into account to enhance reliability,
safety or other probabilistic features. FMEA analysis, for example, is well adapted to
“evaluate individual component failures”.

Our choice to use Fault Tree Analysis (FTA) method was motivated by the fact that “FTA
is thus the appropriate analysis to carry out if a given undesired event is defined and the
goal is to determine its basic causes”, NASA Fault Tree Handbook with Aerospace
Applications, 2002. Hence, FTA is fit to analyze multiple causes and effects.
Some important considerations for using the FTA method have been outlined below.

Our approach was to remain superficial and not to dive into design and/or engineering
considerations potentially overlapping with project requirements, specifications, supplier
experience, design intent, etc. The FTA presented aims at demonstrating that SUT size
and minimal design considerations can influence significantly project costs and timespan.
Publishing the complete FTA seemed irrelevant as it would generate interest away from
the objectives set forth.

Serious considerations have to be taken during the design and/or engineering phases as
typically 5% of the life cycle costs have been spent at those stages, but typically 85% of
the life cycle costs are determined then, Reliability and Maintainability Guideline for
Manufacturing Machinery and Equipment, (1999).
o Life cycle costs (LCC) refer to the total cost to the customer, both sunk and
anticipated, of acquisition and ownership of an item over its useful life, as defined by
IAQG. It includes the cost of research, development, test & evaluation; procurement
(to include production testing, deployment, support to operational test & evaluation);
operations & support (to include training); customer facilities; and disposal. Life Cycle

Cost is also called Total Ownership Cost (TOC).
Our purpose here was to evaluate scenarios probability values but to identify major
contributions to increased installation costs.
Appendix C: STI and SUT length calculations
Equation 1
Case A: Maximum permissible STI length = LSTI
(For a UTA with a front pad eye length that equals ½ the UTA height)
𝐿𝑆𝑇𝐼 ∶= (√(𝑅𝑅 − 𝑀𝐵𝑅 − 𝐹𝐵𝐶 +
(
𝐷𝑝𝑟𝑜𝑑 2
) − (𝐻1 − 𝑀𝐵𝑅)2 ) + (√(𝑅𝑅 − 𝐹𝐵𝐶)2 − 𝐻1 2 ) − 𝐿𝑈𝑇𝐴
2
)
Case B: Maximum permissible STI length = LSTI
(For a UTA with no front pad eye or a pad eye length less than ½ the UTA height)
𝐿𝑆𝑇𝐼 ∶= (√(𝑅𝑅 − 𝑀𝐵𝑅 − 𝐹𝐵𝐶 +
(
𝐷𝑝𝑟𝑜𝑑 2
𝐻𝑈𝑇𝐴
) − (𝐻1 − 𝑀𝐵𝑅)2 ) + (√(𝑅𝑅 − 𝐹𝐵𝐶)2 − 𝐻1 2 ) − (𝐿𝑈𝑇𝐴 +
)
2
2
)
Where:
RR = reel rim radius (m)
RB = reel barrel radius (m)
FBC = free board clearance (m)
LUTA = length of UTA including pad eye (m)
HUTA = overall height of UTA (m)
Dprod = diameter of product (umbilical or cable) (m)
MBR = minimum bend radius of product (umbilical or cable) (m)
Hrig = height of support rigging between barrel & UTA (m)
H1 =distance between reel centre to UTA centreline (m)
H1 ∶= R B + Hrig + (
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Umbilical or cable length calculator
Total storage capacity (m) of umbilical or cable to be placed in bay (B), see figure 12
Equation 3
𝐿𝑝𝑟𝑜𝑑 ∶= (𝑘1 ∗ 𝑘2 ∗ 𝜋 ∗ (𝐷𝑏 + 𝑘2 ∗ 𝐷𝑝𝑟𝑜𝑑 )) ∗ 𝑘3
Where:
Lprod = total length of product (umbilical or cable (m)
Dprod = diameter of product (umbilical or cable) (m)
FBC = free board clearance (m)
Df = reel flange diameter (m)
Db = barrel diameter (m)
Wt = reel traverse width
Wp = partition width (m)
WUTA = maximum width of UTA (m)
Wc = UTA to reel clearance (each side) (m)
k1 = width fill factor (unit less)
𝑘1 ∶= 𝑟𝑜𝑢𝑛𝑑 (
(𝑊𝑡 −(𝑊𝑈𝑇𝐴 +𝑊𝑃 +𝑊𝑐 ∗2))
𝐷𝑝𝑟𝑜𝑑
, 0)
k2 = height fill factor (unit less)
(
𝑘2 ∶= 𝑟𝑜𝑢𝑛𝑑 (
(𝐷𝑓−2∗𝐹𝐵𝐶)−𝐷 )
𝑏 )
2
𝐷𝑝𝑟𝑜𝑑
, 0)
k3 = product fill factor (%) (Typically 80%)
Figure 23 shows an illustration of storage of umbilical or cable placed in a bay.
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Appendix D: Steel tube Umbilical or Thermoplastic Umbilical with spool
The details of design and installation of different types of umbilical have been described in API17E and
API17I. Figure 20 and Figure 21 shows the Steel tube and the Thermoplastic Umbilical.
Figure 20: Steel tube Umbilical or Thermoplastic Umbilical with spool
Figure 21: Thermoplastic Umbilical
The calculation of rigid length depends if a bend stiffener or a bend restrictor is connected with the
STI. Figure 22 shows the rigid length when a bend stiffener is used. As described in section 3.1.3, the
rigid length will differ in other cases depending on if the SUT is connected with either a bend stiffener
or a bend restrictor, or none of them.
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Figure 22: Calculation of rigid length (handling)
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Appendix E: False Barrel Diameter calculations
The false barrel build up diameter required (see Figure 14 & Figure 20) to maintain the umbilical
manufacturer’s stated MBR
(Equation 4)
𝐷𝐵 ∶= (𝑀𝐵𝑅 ∗ 2 − 𝐻1 ) ∗ 2 + 𝐷𝑝𝑟𝑜𝑑
DB = false barrel diameter
RB = reel barrel radius (m)
HUTA = overall height of UTA (m)
Dprod = diameter of product (umbilical or cable) (m)
MBR = minimum bend radius of product (umbilical or cable) (m)
Hrig = height of support rigging between barrel & UTA (m)
H1 =distance between reel centre to UTA centreline (m)
H1 ∶= R B + Hrig + (
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Figure 23: Storage of umbilical or cable placed in a bay
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Appendix F: Responsibility Matrix (informative)
The responsibility matrix on next page includes the typical roles and responsibilities of multiple parties
involved in the design, development, manufacture and installation of UTAs. The matrix is for
informative purpose and can be used through the field planning and development phase.
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Typical Umbilical System Design, Manufacturing and Installation Roles
Activity
Operator
Umbilical
UTA
Manufacturer
Manufacturer
Umbilical
Establishes and
The Umbilical
The UTA
System
monitors
Manufacturer is
Manufacturer
Requirements
communication
presented with
is presented
between the umbilical
the Umbilical
with the
and UTA
System
Umbilical
manufacturers.
configuration.
System
Transmits Umbilical
configuration.
System configuration,
functional and
operational
requirements.
Umbilical
Establishes and
Design Umbilical The UTA
System
monitors
Bundle,
Manufacturer
Configuration
communication
Structural and
is provided the
between the umbilical
Mechanical
Umbilical
and UTA
Interfaces to the
configuration.
manufacturers.
UTA to meet
Approve the design
project
solution and
requirements.
manufacturing
process.
UTA Design
Establishes and
monitors
communication
between the umbilical
and UTA
manufacturers.
Approve the design
solution and
manufacturing
process.
Takes ownership of
the equipment
designed and
manufactured in
compliance with the
project technical
requirements.
Review the UTA
design and
provide feedback
to operator and
UTA
Manufacturer.
Design UTA to
accommodate
interfaces to
the Umbilical
Bundle and
meet project
requirements
transmitted.
Coordinates with
the operator the
acceptance
activities of the
equipment
manufactured.
Coordinates
with the
operator the
acceptance
activities of the
equipment
manufactured.
Umbilical
Bundle & UTA
Assembly
Process & FAT
N/A
N/A
Umbilical
Bundle & UTA
SIT
Establishes the Site
Integration test
requirements, issues
the Test Specification
and is responsible for
coordinating all
Assemble the
Umbilical bundle
to the UTA in
accordance with
the project
requirements.
Supports the SIT
activities and can
provide labour
and resources.
Umbilical
Bundle & UTA
Components
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Supports the
SIT activities
and can
provide labour
and resources.
UTA Installer
N/A
The Installer is
presented with the
Umbilical System
configuration and
properties for
review and
comments from
Installation
Perspective to
ensure
configuration is
installable.
The Installer is to
be informed about
design parameters
and layout/
interfaces of the
UTA.
The Installer
witnesses the
acceptance
activities where
practicable and is
made aware of any
technical issues
associated with the
components to
assess installation
implications.
N/A
The Installer
witnesses the
acceptance
activities where
practicable and is
made aware of any
49
activities.
Umbilical
System
Assembly
Post Load Out
Takes ownership of
the equipment
designed and
manufactured in
compliance with the
project technical
requirements.
Coordinates with
the Oil Field
Developer and
acceptance
activities of the
equipment
manufactured.
N/A
Installation
Takes ownership of
the equipment
designed and
manufactured in
compliance with the
project technical
requirements and free
issues where
appropriate to Installer
and monitors where
appropriate via
manufacturers
installation activities in
accordance with class
design requirements.
Will also include post
installation tests.
Takes ownership of
the post installation
activity and verification
of functionality prior to
systems start up.
Coordinates with
the Installer the
acceptance
activities of the
equipment
manufactured in
accordance with
Oil Field /
Company
requirements.
Coordinates
with the
Installer the
acceptance
activities of the
equipment
manufactured
in accordance
with Oil Field /
Company
requirements.
Supports the
commissioning
activity and can
provide labour
and resources.
Supports the
commissioning
activity and
can provide
labour and
resources.
System
Commissioning
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technical issues
arisen during SIT to
assess installation
implications and for
warranty.
Takes custody of
the designed,
manufactured and
tested equipment in
compliance with the
Oil Field Operators
project technical
requirements and
installs items in line
with installation
design criteria.
Takes custody of
the designed,
manufactured and
tested equipment in
compliance with the
Oil Field Operators
project technical
requirements and
installs items in line
with installation
design criteria.
Supports the
commissioning
activity.
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