Draught Surveying & the
use of Technology
Presented by
Louis Koutelas
Hunter Marine Surveyors
Overview
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Who is the draft surveyor
What is a draft survey
The changing role of the surveyor
The use of portable computing
Draught Surveying
Who is the draught surveyor
– Qualifications and Experience
• Generally seagoing background
– Wide variety of vessels
• Having carried a variety of bulk cargoes
– Alumina, Grain, Salt, Sugar, Dolomite, Iron Ore, Coal
Draught Surveying
How does a draught survey work?
Archimedes Principle states that ;
“The weight of water displaced by a floating
body is equal to the weight of the body.”
Principle of a draught survey
Science experiment done by Xavier
Principle of a draught survey
• Imagine a block shaped ship
10m x 1m x 1m (depth)
3
– i.e. 10m of fresh water displaced
– Therefore the object weighs 10 tonnes
Depth
Length
Principle of a draught survey
• The box shaped ship loads some cargo
– The new depth is now 1.5 m
– Therefore the object now weighs 15 tonnes
– Cargo loaded is 5 tonnes
Depth
Length
Principle of a draught survey
• A real ship is not quite box shaped
• Hydrostatic tables
• There are other weights to be accounted for;
• Ballast water
• Fresh water
• Bunkers
• Reading the draft accurately
• Water level tubes
• Wave dampening devices
• Ships float in water that is variable in density
Principle of a draught survey
Principle of a draught survey
The density of the harbour varies:
During periods of heavy rain, the density of the harbour
reaches a value of 1.000: fresh water
We must check the density at various depths and positions
to obtain a weighted average
Calculation of a draught survey
• Back in the “Good old Days”
• After cargo finishes the Chief Officer would go out
for a leisurely stroll to read the drafts
• Cupper time before sitting down to sharpen a pencil
• Calculator and scrap paper ready
• Scribbles, erasing and tapping on the calculator until
the final answer
• Ooops made a mistake looking up the MTC from the
hydrostatic tables
• 45 minutes later we have an answer.
Calculation of a draught survey
2001
• PWCS data for number of trimming pours used
for a sample of 90 vessels
Trim Pours
Ships
%
1
2
3
4
5
2
40
24
20
4
2.2
44.4
26.6
22.2
4.4
53.2%
required
more
than 2
pours
• Average trimming survey time was around 38
minutes with some taking over 1 ½ hours.
Calculation of a draught survey
• Doing the calculation by hand is
• Slow and delays cargo operations
• Prone to errors particularly at 0200 hrs
• Using a laptop
• Quicker but requires going back to the office
• Some offices are on the bridge
• Using a handheld
• Even quicker again and provides instant results
• Much faster error checking
• Fast and accurate surveys increase the efficiency
of vessels cargo operations.
Calculation of a draft survey
• These days the terminal requires that the trimming
survey is done in 20 mins or less and in only 2 pours.
• Using handheld devices the survey time is limited by
how quickly you can read the drafts.
• Our average for the trimming survey is 17 mins
• This is a saving of 21 mins per vessel from the
averages of a decade ago.
• Newcastle loads around 1400 coal vessels annually
• This saving of time results in an extra 20 ½ days or 3
million tonnes loaded.
• Provides more certainty for vessel movements.
Calculation of a draught survey
• Hand held computers come in many forms
• Windows
• Clamshell
• Slate / Tablet
• Windows phone
• Android
• Android tablet
• Android phone
• Apple
• iPad
• iPhone
Reporting
• Clients want their reports yesterday
• Using computers for calculation and transposing
data to a report form cuts down on reporting
errors
• Makes report generation almost instantaneous
• Using VBA in Microsoft Office to customize reports
• Using mobile broadband means that the client can
have the report as soon as the vessel is complete
• USB dongles or WiFi hotspots on your phone
Bulk Terminals
• Bulk export tonnage is increasing
• Time is money
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All delays are accounted for to the nearest minute
Poor performance notices are issued
Poor performers are not accepted in future
Only using good performers increases port throughput
• Places more pressure on every facet of vessel
operations
• Load plans – number of pours
• Surveys – Initial, Trimming & Final
• De-ballasting – Stripping
The modern surveyor
• Reviews load plans during initial survey
• Advises on relevant variables used in the plan
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Stowage factors
Dock water density
Tidal departure criteria
Cargo criteria (Max / Mins)
Recent terminal belt error information
De-ballast issues
Trimming pours
• How to complete the loading to the highest level of
efficiency
Planned to sail
with ballast in
APT & No5
DBT’s.
Ended up loading
to her marks and
deballasted
completely
loading an extra
1455 tonnes
Cargo Distribution
• Poor distribution results in sag
• Sag is a bending of the vessel in the middle
• Midship drafts are greater than the mean of fore & aft
• This means they reach the limiting draft earlier
• A 10 cm sag as per the previous plan is a loss of 258 tonnes
• Historical Deflection Analysis can be used to optimise
distribution and minimise sag.
• Techniques like HDA help gain tonnage by simply
working / planning smarter.
De-Ballasting
• Traditionally vessels stop loading to de-ballast if the
load rate is too high
• Is it necessary to strip all tanks completely ?
• Loading to summer draft
• Do not stop for de-ballasting
• Take less cargo
• Not loading to summer draft
• Take booked tonnage
• Strip tanks enroute
Summation
• Terminal pressure to minimise delays means that;
• Draught Surveys must be conducted quickly and
accurately
• Trimming survey is conducted as quickly as possible
• Use of hand held computers help achieve both
• Load Plans must be optimised such that they result in a
good vessel loading performance (high load rate)
• The latter stages of a loading is monitored and assistance
given by the marine surveyor
• Speed of reporting and sending from the vessel
• Automated reporting from the field results in happy clients
The Modern Surveyor doesn’t loose sight of what
happens when she sails