Draught Surveying & the

use of Technology

Presented by

Louis Koutelas

Hunter Marine Surveyors

Overview

• 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.”

Science experiment done by Xavier

Principle of a draught survey

• Imagine a block shaped ship

10m x 1m x 1m (depth)

– i.e. 10m3 of fresh water displaced

– Therefore the object weighs 10 tonnes

Length

Depth

Principle of a draught survey

Length

Depth

• 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

Principle of a draught survey

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

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

Principle of a draught survey

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 2.2

2 40 44.4

3 24 26.6

4 20 22.2

5 4 4.4

• Average trimming survey time was around 38

minutes with some taking over 1 ½ hours.

53.2%

required

more

than 2

pours

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.

• Hand held computers come in many forms

• Windows

• Clamshell

• Slate / Tablet

• Windows phone

• Android

• Android tablet

• Android phone

• Apple

• iPad

• iPhone

Calculation of a draught survey

• 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

Reporting

Bulk Terminals

• Bulk export tonnage is increasing

• Time is money

• 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

• 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