Draught Survey - A Guide to Good Practice

DRAUGHT
SURVEYS
A GUIDE TO GOOD PRACTICE
by
W J DIBBLE Master Mariner, B.Sc, MllMS, MNI, MRIN
P MlTCHELL Master Mariner, B.Sc, MIIMS, MNI
This guide is designed to help Surveyors and
Masters worldwide ensure that draught
surveys are carried out as accurately as
possible in the prevailing conditions. It
recommends procedures and formulas for
every circumstance likely to be encountered.
The UN/ECE DRAUGHT SURVEY FORMS
have been included in an effort to achieve
standardisation throughout the industry.
rim Dibble and Peter Mitchell,
of MID-C Consultancy, have
produced another publication
on Draught Surveying which
deals fully with the prinCiples
involved and the reasons behind
the various corrections and
methods. This Loss Prevention
Guide makes no pretence at
delving deeply into the subject
It does, however, provide an
outline, showing all the
methods and corrections for. a
Draught Survey to be carried
out to the required accurdCy.
The North of England P&l Club is
a leading international mutual
marine liability insurer with over
11 CXXl CXXl GRT of entered shipping.
The provision of sound, practical
advice 10 ilS Sbi(H>wner Member~
has been part of the service ~iDCC ilS
founding in 1860. The accurate
measurement of dry bulk cargoes
by the vessel can minimize
considerably the risk of shortage
claims and disputes. This practical
guide to carry out a good accurate
draught survey is continuing in the
tradition of The North of England
P&l Club in assisting their Shipowner Members 10 minimi7-C their
risk exposure and is the second in a
series of loss prevention guides.
The first guide covered "Steel
Preshipment Surveys" and other
relevant publications circulated by
the Club include "Signals", Loss
Prevention Quarterly and "The
Master's Role in Collecting
Evidence" published by The
Nautical Institute.
£18
ISBN 0 9521164 1 3
MID-C Consultancy
Published by MlD-C Consultancy
All rights reserved. No part of" this publication. other than the
enclosed UN Forms, may he reproduced, stored in a retrieval
system or transmitted, in any form or by any meallS, electronic,
mechanical, photocopying, recording or 01 herwise, wi thout the
written consent of the Publisher.
Copyright
(c;) ~!nD-C
Consultancy
and the Norrh of England
P&l Association Ltd. 1994
Reprinted 1998
ISBN 095211641 3
Authors: Jim Dibble, Peter Mitchell
and The North of Eng\:J.nd
P&l Association T.td
Printed and bound in the UK
This puhlication i5 intended to provide guidance in conducting a
Draught Survey. While every effort has heen made to ensure
practical and reasonable recommendations, the Authors arc not
liable fi)r the conseqllences of implementing or attempting to
implement these recommendations.
LOSS PREVENTION GUIDE
DRAUGHT SURVEYS
A GUIDE TO GOOD PRACTICE
W J DIBBLE MASTER MARINER H.Se MIIMS MNI MRIN
P MITCHELL MASTER MAlUNER B.Sc MIIMS MNl
and
THE NORTH OF ENGLAND
PROTECTING AND INDEMNITY ASSOCIATION LIMITED
MID-C
CONSULTANCY
Contents
.
Intro d uctlon ...... ".""" .. ,
l1li" l1li.
l1li
l1li" ••••••••••••••• " ••••••••••••••••••• "
.
.IV
Practical Procedure ..... "...................................... ".. 1
Information Required ........... "............................... 8
Data r-.1anual For Dnl\lphl
,., Surveys
. .......................................... H
.
H yd rnslalic Particulars ............................................................. 9
Deadweig'ht or Displacement Scale ........................................ 11
Capacity Plan and Tables ....................................................... 11
Soullding Tahles ..................................................................... J '2
Correction Tables and Diagrams ........................................... 1 ~
Plalls ........................................................................................ 14
Lightship ................................................................................. 14
Assessment of Underwater Volume .................... 16
General Draugh 1 1\1 casu remenl ............................................. 1()
Draught Measuring Erjllipmcnl ............................................. 17
Draught Reading on Outbuard Side ...................................... 18
Draught Gauges ...................................................................... ::!()
,S·quat ....................................................................................... 9('
_)
Currectioll of' Dr;H1ghts to Perpendiculars and Midships ..... '21
COlTenion ror List .................................................................. 26
Hull lk!1ection or Ho!! and Sag ............................................ 26
t_
l)
Correctiuns i(n- 'I'rim .............................................................. 30
Density .................................................................................... :~3
..
11
Assessment Summary ............................................................. :~7
Deductibles ........ ,. ................................................. 38
Soundings and UlIages ........................................................... 38
Salnpling ................................................................................. 39
'i~'
' . .................................................................... J'19
rUlI (',orrectlons
Liquid Slop Tallks .................................................................. ,11
l\1ixt llres .................................................................................. 42
Residue in C()mpartments ...................................................... 4~
Anchors and C:ahles ................................................................ 4~~
Addirional pacto!'s .................................................................. ,1,1
Glossary ................................................................ 45
Appendices .......................................................... 49
Eguipment Check List ............................................................ ,19
Check l.ist of'Reservations ..................................................... '\ ~j
information Check List .......................................................... 50
Correct iOlls CIH:ck I.i::it ........................................................... 51
l'vletric!I m pcrial Conversions ................................................. 32
Index .................................................................... 54
ACKNO\"ILEDG EMENTS:
The authors would like to thank the following I~)r their assistalln;:
'"
Commander T Lillt:y of tht: Intcrnational I nstit1.ltt: of \ilarinc Surveyors,
Captain D C reen for his mcticulous work on the original sui pt.
Captain R Ward.
Captain P Coomhs.
"
.
III
Captain Y A.ysuna.
INTRODUCTION
The purpose of a draught sun'ey is 10 determine the amount of cargo loaded or
discharged for the bendit of all the interested parties, A well·conducted draught
survey of a larg'c vessel should achieve accuracy 10 wit hill O.!jl)(,
The survev must be conducted I1lctint\ously. raking imo accolll1l all the prevailing
circulllsta;1Ces, Thc lillal rcp0!l should illmrporate every aspecL and diHicuity
which has been encou111cred ill order 1.0 cOll\'er all aspects or tlte sun'ey,
\Vhile draught sur\'cys Illay be carried ollL b)' professional surveyors, Ihe ship's
ollicers should also }Jerlorm a draught surn:y t() the sallle deg-rec of accuracy,
Tt is hoped that this ~ui(k will assist in achieving' the required stalldards,
DRAUGHT SURVEY
The draught survey is the "hcfrll'e and after" surH::Y. ",hich determines. hy
meaSllrcmelll. the \Tssd's displacement hefore and alter loadillg ur discharging.
Tlte uifIerence between these tW() displacemems is the weig'ht u('carg'O loaued or
discharg-cd,
DEADWEIGHT SURVEY
L'nder certain rin:ulllst(lnCcs. the sur\'eyor or ship's ulIicer may have no choice
hill ht: restricted to carryillg uut a deau\\'eight survcy, The weights of all
lIIeasurable nOl1-carg'O elemeJ1ls OIl Ihe vessel ;IlT determinecl: blinkers, /i'esh
wall~r, ballast. stures etr. These are IhCIl addt:d tu the light displacemenl
(including any lightship constant). Thi1i total is then dcdw:ted lium the prt:sem
displacement tu procluce Ihe approximate weight of cargo on hoard,
UN/ECE
DRAUGHT SURVEY CODE FORMS
These fill'lIIS ha\'e iJeen included atlhe hack of this hook, They are rllt: work of
the Lnited l'\ations F.nll1()lllic Commission t<J]' Europe, the Coal Working Party
of the Encrgy COlIlmillee. which pmduct:d lhe COr/I' of IIUi/lJl'lIl S/{/l1d(JHI~ fi/lrl
f}I'OCI'dult'sfin Iht' jJI'I/imnall(1' dmllgli.1 SI/Fi't'yS I{ ('/Jul I'rlIg()l's. The Working Part)'
recollllllcnd thc IISC oftlit: liJl'lllS in order to achie\'e IIniforlnil.v aIld consistency
in drallght sur\'eys. su a\'uidin~ Iht: dislTepancies which gin:, rise to cOJlIllIt:rci~1
disputcs,
4
The forms have been /i'eely given, so that all su rwyors and ship's ol1iccrs may
photocopy and Ll1ie tht:lJJ as a standard [ormat throllg'holl! the industry.
1\'
PRACI'ICAL PROC:EDURE
Jr is impossible to cover every coIH:ei\'able problem likely ro be encountered
when carrying- out a draught survey. Ships and ports vary so much rh.It there
will alway~ he rhe unforeseen circumstances ,,'hich will require an oll-the-spOI
decision. These not.es and steps to be taken, gi\'e only a broad approach to the
slIbject There is howe\'er, n() slIbstitutl' for experience.
An inaccurate sun'ey may result in collsiderable expense [0 several partics,
therefore it. shollld be conducted cardully alld aCCllraldy. Bcing- well prepared
alld having su!Iicicllllilllc will all()w the survey to be conduCled correctly, It
may not appear expedient to delay the ship in order to colllplete the drauglll
survey properly, but it could save 1II0lley in Ihe IOllg lerrn, This decision must
lie with t.he \(ast.er, hO\\'cYlT careflll preparation could reduce these delays to
a 111111 IlllllIII,
All parties should work together Il)r a unanilllous rcsult. the
established by illspenioll and lIot by verbal agreemem.
j~lCrs
should be
1. The ship and ship's staff must be prepared for the survey.
Shore surveyors must be ready for the ship's arrival.
Prior to arrival
The ~hip should be asked tu prepare lill' Ihe draught survey,
The iJallast tanks shoulrllw adjusted to a I(,\,et co\'ered IJ\' the sounding
tables,
lL should be remembered thalllllltanks Gill be pressed LLp lllll slill retain
air puckl'lS alld also il call he difficllh 10 estahlish that a r(lnk is completely
t'lIlJlly without visual inspection.
llallast holds, (main earg-o holds used IlJl' ballast) should be ClIIpl}' of
ballasL un arrival al the l()ading porI, if Jlossihle,
Thc vcssel sho1lld aITi\'(:' with a sale lrim. ~lIiLable ii.lr the Ilavigation to
eIller port and wirhin rhe limits of trim covered Iw the trim UJlTeCliolls of
the sounding tables. The vessel shollld alTin~ in all lIJlrig-ht conditioll,
Staff, doclInwntarion and eqllipmenl should be ready on the arrival of
the ship. There shollld he no m(wemell( of ballast. fi-esh water, bunkers
or cargo and hatches, cranes ami moorings until all Il\CaSLIITlIlcnts are
takcn and agreed by surveyurs and ship's ollic('rs, The prudelll surveyor
will han: oiJsCI'\'ed the shore side drallghts hefore iJoarding as these can
be used to indicate any changes. See photograph of the tools of the
draught surveyor Oil page 35 and equipment check list on page 49.
2. Examine the ship's documentation and discuss the ship's
present condition
Documentation and information
Surveyors and ship's officers should discllss doulITlelltation details and
the location and state or all compartments. The instruction pa~es of the
stability information book and calibralion tables should be studied and a
check made or the tank capacities with the capacity plan. [t should be
remembered thal the pOrl and starboard tanks may not be the same and
consequently ha\'e separate calihration lables.
The base lor measurement of vertical heiRhts, the rcferenCl: point 101'
longitudintll measurements, the units and the sign com'clltions used in
the tables must all be verified. The units used in the correction tables
should also be carefully noted bccausc there is sometimes a mixture 01
units and sign convcntions contained within the samc documentation.
The whole survcy should be conducted using the units of the ship and
the final result changed 1.0 a suitablc unit, if necessary. \Vhell feel and
inches are the standard unit. convert to feel and decimals or a loot 101' the
ml1\'cll ienn: or a calculator.
The hill sounding deplhs of" I.anks, lhe summer draught and freeboard
ancl the record of recent tank sOllndinl!s should be noted.
If a bunker survey is not to be carried out, the chief engineer's bunker
fi!:,I'lues (fuel oil, diesel oil and lubrication oil) are required, also the daily
port consumption quantities. Should any bunker or stores be delivered
during the stay then the delivery notes must be sighted for the
additional quantities to he included in the final survey. The draught
survey is only interested in changes in the bunkers on board, that is
consumption and deliveries.
The position of the anchors shoulcJ be checked, should any all.erations be
proposed dllring the Slay then {he weight of the anchors and cables
should be determined.
The ship's stair and slIrvcyors should work toRether 1hroughollt.
See inlormat.ion chcck list. on page 50.
2
3. Take accurate overboard water samples and draughts
Density
Using a sample bucket take samples from half draught depths from at
least two positions on the ofI-;hore and the onshore sioe, a\"oiding the
oischarges, stagna m waler between ship andjeuy and outfall areas. Take
samples of ahout one litre and do 1\(11. mix the sampl('s.
Rinse out lhe hucket alld the sample jar with the first sample of water.
Take the density readings promptly, protecting I he sample jar from the
wind and direct sunlight. Hold the hydrometer wrtically by the lOp of
the stem and gently lower inlo the sample until it !loals freely. Take the
hydrometer reading where the overall level liquid surflce meets the
graduated stem, not the top or the meniscus, A\'oid parallax by filling to
near the top of the sample jar and placing the eye ill line with the liquid
level. See photograph of a hydrometer reading 1.01 G5 Oil page 34. The
bottom of the sample jar should have ~5 mm dearance below the hase of
the hvuromeler
and ha\'e a minimulII internal diameter of 50 111111 .
..
If densities obtained show no major variation then calculate the average
value, however if there are suspicious variations in the readings th~n
additional samples should be taken and this f:lctor included in the report.
Measure the apparent demity with a Zeal glass draught survey hydrometer
and be aware of any tidal changes which may affect the sample density.
Sec density section on pages 33 and 36.
Draughts
The draughts and densities should be obLained at nearly the same time
if possible. Draughts and densities taken at slack water are the most
accurate but this may lIot be practicable.
All the draughts should be read with great care and every e!lort made LO
read nirectly h'om ship's side llsing a boat, laducr or other available
means. Th(~ tigures should he written down as they are obtained to avoid
mistakes of mcmory.
If rClJuired, the midships draughts Gill be obtained by measuring the
freeboard from the watnlinc 10 the top ohhe neckline or to a convenient
point above the deckline. when a correction must be applied. A tape with
a /loal plate at the zero mark can be vcry usefully employed to achie\'e
this measurement. Sce draught measurement section on pages I (i to 20.
4. Calculate the ship's underwater volume and displacement
a)
Correct the observed draughts to the centreline, i.e. the mean of
the port and starboard draughts.
b)
Correct the centreline draughts to their value at the correct position
of the perpendiculars.
c)
Allow ten' hog or sag and obtain the correct draught Illidships,
d)
Enter the hvdrostatic tahles with this corrected draught to obtaill
the uncorrected displacement.
e)
Correct this \'alue of displacement for:
first trim correction
second tri m correl'1ion
list (ir necessary)
density
s(x the appropriate section fc))O details of these calculations on pages IG
to :-17.
5. Determine the quantity of deductibles
Ballast and fresh water soundings
Every compartment capahle of carrying water should he carefully inspected
alld sounded, allowing suffic:i(~lIf lime it))' lIuctllariolls in levels due to the
rCll1m·al or the sounding caps. When at all exposed berth the movement
of the vessel may create errors,
To oyercomc t his problem several
soundings should be taken alld t.he average value assumed to be the
corn:cI. olle.
The sounding tape IIlllst be checked to ensure that it reaches the bottom
of the tank, If the tape is marked at the ship's full depth it can an as a
useful guide and the consistency or the depth of the different tanks can
be checked. It should be remembered tliat the vertical (allk height and
the length of soundil1)?; pipe may be ditferent. Sce phutograph of
sOllnding tape on page ;~!).
Full tanks may have air pockets l'spec:iillly whell the ship is trimmed.
Topside tanks Gill he o\'erllowed frOln fi.)I'ward and ali air pipes until a
steady lIow through both is ulllllistakable, the sounding pipe extellsiolJ
may prove usetill for this operation. HoweHT care should be taken to
ensure that lhc ovcrllowing ballast water causes no othcr problems e.g.
wetting of cargo waiting to be loaded, soaking the electric power boxes 011
the (luapide or wa~hillg debris or uther pollutants over the side.
Fm a stern trim the position of the forward air pipe relative to the
forward tank bulkhead should be checked to determiuc any possible
remaining void spaces and where ueCl.:ssary Ihis factor should still be
allowed. Other lid' /al/lis should h(' sounded and the trim corrections
allowed.
The ballast discharged !i'um tanks lIIay kil\'c rcsiclllalliquid in pipes and
in areas of poor draina~e. This water is difficult TO detect and time
should IX' allowed for drainage purposes before taking MHHldings.
Empty tanks will prubably have residual water even at zero soulHIings,
these indeterminable quamities Gm he ignored af both before and after
surH:YS, provided Ihat all parties are satisfied that no changes have t;lken
place during the imerval between surveys. In other cirullllslann:s itlllay
be necessary (0 assume a slllall pen:eulage (I (;i; or ~(}~,) of r1w tanks total
capacity as addit ioual weight to (over all remaining drainings.
Tfthe ballast soundings are out~idc the maximum range ofthc calibr;l1ioll
tahle~ then ballast should be run uul ulIlil lhe level is suitable.
The duel ked, pipe tunnels, peak tanks and swimming pool should nor
be t()J)~otten and soundings taken as u~ual. The bilges should be checked
and an}' pumped out during the ship's stay must be recorded. Wben a
\'essel loads a dry bulk cargo which has been welled, a record of hilges
pumped during the whok voyage could prove very useful as evidence. to
explain any apparent loss of cargo between successive surveys.
Ballast holds often cause problcrn~ duc to poor lank calibratiuns and hull
deformation. These should be empty or hallast prior to arrival at the
loading port and vislJally inspected if' possible.
Bunker tanks need not be inspected and sounded during a draught
SUITe)', unless a bunker survey is also required.
Sec soundings and ullages section on pages
:~8
to -13.
Ballast samples
The water within the sounding pipe may not be properly mixed and
lherefore not he representative of'the liquid in the whole tank, irill dOllht
llll: sampk shollld he laken al the bouolII or the pipe lIsing a suitable
sampling can which can be opened at the appropriate depth.
Sutlicient sample densities can be obtained from the tan ks dowlI onc side
the ship only. unless IIl<\jor variations occur. Variations could he
caused by the ballasling raking place at diHcn:nL limes and locations.
The ballast tank dipper or hand pump down the sounding pipe may be
lIsed to ohtain a sample where the water is well mixed, as showlI in the
photograph on page 3,1. The sample .iar should he rillsed out with the
first sample and then the Zeal hydrometer IIsed to obtain the apparent
density o/" the waler, as with the sea water density, a remperat\ll"e
corn':clion is not necessary. A ballast hold should be sampled al diUerent
levels with the water sample bucket and checked for any major variations.
or
The measurement of dellsity, the hydnlmeter lo use and the reading
obtained can cause problems, th(, density sectiolls on pages :);1, :16 and 53
sholtld he read care11tll)" t.o avoid these problems.
6. After completion of loading or discharging, repeat sections :l, 4
and 5 above, for the final survey
Final survey
Adequate prcparatioll is n':ljuired again for the final survey. The intcIHbl
quantities of carg-o. blinkers, fi'csh water and s[Qres and t.ht: proposed
finishing draught should ue determined ill advance or completion of
carg-o. If therc is to be a final trim by the head then an intcrmedial.e
sur\'ey of the ballast relnaillillg" on board, should be carried out while the
I.rim is still bv the stern. Accurate deterrnillal.ioll or the ballast on board
n'lllains a lIIajor issue and ensuring lhat the empty tanks are actually
dear of ballast is a 1ll;~j()J" cause of errors in the final calculations.
In\'oice iigures for the weights of all blinkers, spares and S[Qres taken on
board dllring the stay should be \'erified and a check lIIade I.hat Ilothing
has been landed. Changes in the bilges, swimming pool. and other
regions not directly associated with the working of the "esse! should be
delennined.
Notes
All calculations cotllained in this guide should be carefully exeCllt.ed and agreed
belwt:en parries. The same SUr\Ty methods should he used at the loading and
the discharging ports in order to achieve consistency or results.
The calculations shoukl deal only with the acquired facts ami nOl. introduce any
unsubstantiated cons/an/s. Tht: constant often referred 10 with draught surveys
is dealt with in the /.ighfslnjJ C01lSfanl se(:lion Oil pag-es 14 and 15 and its
significam:e should be understood.
All circumslances that may inlluellCl! the accuracy of the surveys should be
recorded on the slIr\'ey report.
Conclusion
Shortage claims on bulk cargoes an: a rnajor concern lo the shipowner and their
P&l clubs. The), result in claims invol\'ing significant sums of nHlIlC),. Well
maintained records when used as e\'idence, including aCUJrat.e and comprehensi\'e1y
documented draught sur\'eys from both the load and discharge ports, may
enable these claims to be slIccesslillly defended.
7
INFORMATION REQUIRED
It is the I\fasrer's respomibility to ellsure that Ihe drallght lIIarks arc dearly
visible at a minimulII 01' six positions on the hull, that is at:the t<H'ward end, Ihe all end, mid ships, on both sides.
It is also the responsibility of the ship's 'faster to provide the surveyor wilh IIpto-date and accurate infiJrmatioll which has been cenified by the ship's flag state.
This informatioll shollld mlllain details
Ihe ship alld it's present condition.
or
For details of what should be included refer to the inj'ol1l1fllion (h('rk list
50.
Oil
pag-e
The information may be in metric or imperial units.
The presemation and precision or the informarion will vary widely from ship to
ship and the langllage IlIay nol be Ihat of the surveyor.
Take great care when using this data. Read the stability infi)1'mation book
imroducrion pages TO deTermine The C01lTems of each of rlw rabies, and how they
should he applied. :\ol aI/ the inhmnalioll will be required tor every draught
sun'c\,.
DATA MANUAL FOR DRAUGHT SURVEYS
The t:nited Nations recoHllnencls thal ('very ship carrying blllk cargoes
should be provided wiLh a data Illanual for draught suncys, which
should bl' n:rtilied by the ship's home administration or its classilication
SOCII.:I V.
,
Thc language of the lllanual should be English or have English translations,
The metric system of units should be used throughout.
Longitudinal lIleaSIIITlllell1.s should he hased
UpOIl
midships.
Sign cOII\'cntion:
measurements forward are negative (-), measuremeI1£S af£ are positi\'e( +).
Vert.irallIIeasuremenLs are
lO
be Laken from the bOLLolll of"thc ked plale.
:-\
It is recommended Lhat vessels longer than 200 metres Length Over All
(LOA) shoulrl be marked at five points on faelt side: forward, midships
and aft as usual awl also at the mid points between these positions, This
allows a more ao.:lll'alc assessmelll of an)' hogg'ing or sagging- effects.
'I'he positions of the draught marks n:lativc (0 the appropriate perpendicular
should be included in the dala manual.
li nlortunatelv (his daLa ll1illlllal is ofi.en not a vailablc.
HYDROSTATIC PARTICULARS
Illfonnation is calibrated agaillsl draught. uS\lally illr Ihe cyen keel condition.
The displacement is the weight of the ship. derived from
volume of water displaced by the ship x apparent density.
In the lllctric system, this displacement is ofLen given in tOIll\(' of'salt water at
apparelll density (weighl ill air) uf 1.025 tonne/m:'.
It is imponant to establish the exan weight
lO
volume relatiollship.
DRAUCHT AND FREEROARD
Forward draught
The distance from lhe bottolll of' the keel to the \\'ateriine
perpendicular when the ship is IIpright.
Oil
i1w li)rward
Aft draught
The distancc /i'om the bO\JOJll ol'the keclt() ill(' waterlint' on rhe all perpcndicular
whell Ill(' ship is upright.
Freeboard
The distance fi"()11l the waterline to the deck line. normally measllred midships
Depth of ship
The disLance from the
IJOUol1l
Depth = draughL
or the keel to rhe deck line.
+ freeboard
9
That is:
Arithmetic mean draught (AMD)
The arit.hmetical mean of the iorwanl draught and the air draught will equal the
draught midships if there is no hog- or sag, this is called the arithmetic mean
draught.
Hut a ship trims about the longitudinal centre of flotation (LCF).
True mean draught (TMD)
When a ship trims due to shifting a weight, i.e. no change of displacement., the
only draught which does 1/01 change is the draught at the longitudinal centre of
flotation. It is this draught which will give the appropriate displacement on the
hydrostatic tahles, and it is called the trlle mean draugln. The position of the
LCF is there!ore critical to a draught sUl"\'ey.
The diUerellce hetween the trill' mean draught and the arithmetic mean draught
is known as the layer correction.
Trim factors
Some stahility iniormatioll hooks tabulate trim factors, /i"Jrward and alt, bur no
posit.ion ior the longitudinal centre oftlot<lt.ioll (LCF) forward of the all perpendicular
(AP).
The LeF can be found from the trim faCfors by the following ii.mnula:
LCF from AP =
length between pcr:pendiculars x aft trim factor
forward trim factor + aft trim factor
Trimmed hydrostatics
Some ships are supplied with 'trimmed h),drost;nics'. These normally consist or
'icvcral set.s or hydrostatic data each onc calntlated It)r a panicular trim. They
may be in 20 cm steps covering the range of trims over which the vessel is
expect.ed to operate. Each set. or hydrostatic data consists of di'iplacelllellls
t.abulated against draught for a particular density. The densities may be in
increments of 0.005 iium 1.000 to 1.025 and the draught.s ill :> Clll steps. Such
tables avoid the need for hot.h t.he 1st and 2nd trim corrections and abo thc
density correction which are described within I.he chaplcr Assessmmt of underwater
volume on pages 16 10 3i.
Trimmed hydrostatic tables need to be interpolated for draught. densil.y and
trim in order to find the correct dispiacelllclIl. This interpolation is fairly
diflicult and needs care!i.ll thought in order la achieve an accurate result.
Check the use of trimmed hydrostatics in the introduction to the stability
information book.
10
DEADWEIGHT OR DISPLACEMENT SCALE
The displan~mcnt, dcadweight, tonnes per centimetre immersion (TPC) and
moment to change trim per centimetre (MeTC) for salt water are shown against
the true mean draught (TMD) in the dea(h\'(~ight or displacemelll scale. It may
also show the same {(H' fresh wateL
If only salt water values are g'iveIl then the scale shollld be elllered with the
TMD in actual observed density. Calclllations should Le carried Ollt with these
figllres as the density correnion will take care of the alUustmcnts at a later stage.
The scale will also show sUlluner load draught alld the lightship draught. It will
relate the final 'I'M I) to the linal displacement. Study it careliJIly lO make certain
or t.he weight. to vollllJle relationship.
CAPACITY PLAN AND TABLES
The capacity plan shows all the cargo compartments, ballasl spaces ,Ind blinker
tanks Oil the ship.
Capacity tables list every space in the ship which Illay be used f(ll' cargo, ballast.,
stores, fuel, lubricating oil and fresh water.
The position or each space is indicated hy the number of the ship's ii'ames at
each extremity or the space.
The volume of each space. in cubic metTes, is lisLed for:
Grain space -
the gross volume measured to the ship's side plating.
Bale space
Lhe neU volume measured to the inside ol'thc frames
or spar ceiling (cargo battens).
Spaces {(1I' liquid only are tabulated in either CIIbic 'l1l~tres or the numher 01'
tonnes of the liquid which the Lank Ilormally holds. specifying the density IIsed
t.o calculate those tonnes. If the tables give cuhic metres then these must be
mult.iplied hy the oh served density to flnd tonnes. If t.he t.ables giH' tonnes then
they must be divided by the density or t.he t<lhle and multiplied by the observed
density.
11
SOUNDING TABLES
Suunding t.ables are separate mhlcs, olten found in the care of the chief oilicer
amI/or the chief engineer.
The tables may be calibrated wit.h either soundings or ullages.
The calibrations may use cubic metres (i.e. tonnes offresh water) or the average
density of the liquid which is normally carried in the lank and give tonnes ol'that
liquid.
For accurate assessment of the quantity ofliquid in any tank, the actual density
of t.he liquid should be determined and the quantity rc-calculated.
CORRECTION TABLES AND DIAGRAMS
Sounding correction tables
The sounding rabies will have been calculated 10r the ship
Oil ;\11
e\'en keel.
Correct.ion tables should accompany any suunding t.able of a tank le)r which the
sOllllding pipe is not at the longitudinal cent.re or t.he tank.
The table should gi\'e the correction for any sounding and !ill' each metre of
trim oft.he ship over the normal operaling range oftrirns and require interpolation
fill' t.he actual trim. In the absence of SIKh t.ables, calculations will have to be
made from t.he uriginal plans.
Trim correction
The stability information book may include a table to apply the corrections for
trim. Investigale carefully whelher this includes bot.h the 1st. and ~nd. t.rim
corrections. Scc pages 30 lu 3:1.
Position of marks
The stability inlormation hook may provide a correction t.o apply to the appropriat.e
drallght readings t.o correct the reading, to the value it would have had, al the
correcl position. See pages 21 to 26.
Hull deflection
The stabilit.y inforrnat.ioll book may provide a special means of calculating the
vessel's hull liislO1'lioll correction when calculating an accurat.e underwater
volume. See pages ~6 to :~O.
12
Hydrometer certificate
British Standards Insrilule (BST). Tntel'llalional Slalldards Organisatioll (ISO)
or rhe Zeal certificate of conformity. pro\'idcs Ih(' appropriare correcllon to
apply to rhe hydrometcr
. . ',
. ;
". ' j "
'.
..' . '
,;, ,0:11
~'I\'"
. ~~ .
' I> "
By killd permissioll of ( ; ) I Zeal I,td,
Hydrometer and certificates
PLANS
General arrangement plan
The general arrangement plan shows the layout of the ship and indicates all the
spaces within il. It gives the position of all the spaces, t.heir lIse and capacity.
Other plans
More detailed plans of ballast tanks and bunker t<lllks may be necessary.
Ifthe vessel is t.rimmed it may be imporl.ant to know the horizontal surface area
of liquid in t.he tank and the relative position of the sounding pipe in order to
assess the quantity of liquid in the t.ank accurately.
LIGHTSHIP
The lightship weight is t.hat which has been determined during an inclining
experiment..
It includes:
the ship and its full equipment, engine room spares. ,·valer in t.he boilers
to working level and lubricating oil in the engines.
It does not include:
personnel, cargo, fuel. stores and water.
Growth of lightship
The inclining experiment may have been performed a considerable t.ime ago,
but, over a period of years, the lightship weight will increase. This is due to t.he
changes in the equipment., t.he build up or paint over the ship, the storage of old
equipment, mud in the hallast t.anks, the aeculllulat.ion of dunnage ele. This
phenomenon is known as the growth of lightship and is t.hought [0 amount to
ahout 0.2% of the light displacement pc!' annum. This b'Towth is accounted fin'
in the lightship constant.
Lightship Constant
Vessels which regularly assess their lightship weight find t.hat the wei~ht from
their calculations differs li'om the tabulated value in the stahility inlormation
14
book. This difference is named the lightship constant at that particular draught
survey.
A record should be kept of the Iight~hip constant at each draug'ht survey. It may
not be a constant. value since it is the result of inaccuracies of calibrations,
accumulations of sludge, unsymmetrical hull distortion and many ot.her fact.ors.
It can only be used for a guide to the consistency of results and the variations
experienced on previous surveys.
When carrying out a dcadweight survey the value oUhe lightship constant ma)'
become more significant and a record of previolls values is then important.
15
ASSESSMENT OF
UNDERWATER VOLUME
The underwater volume of the ship, and ult.imatel)· its displacement, is normally
f(>und by carefully reading and analysing the drallght marks and by careflllly
est.ablishing the density of water in which the vessel is floating.
The corrected mean draught is used LO enter the hydrostatic tables in the
stahility int(JrI11ation book and t.o find the appropriate displacement equivalent
to this draught and density. This ,·alue must then be corrected to determine the
precise weight
the ship in its present circumstances.
0"
GENERAL DRAUGHT MEASUREMENT
The draughl. survey is based upon the accurate reading of the draught marks,
therefore no effort should be spared to achieve accuracy. Draughts should be
measured to two decimal places, that is to the nearest centimetre.
Bciore cargo operations commence, the water densit.y and all six draught marks
should he read, recorded and comments made on the prevailing conditions.
During the time Ihat the readings are being made, uo lransfer or discharge of
liquid of any sort, or movement of any weight wirhin the ship, should be allowed.
Tht, draughts and density should be wken again
loading or discharging operation.
011
the mmplerioIl of the
Measuring the draughts in a swell
I n turbulent conditions there may be waves, swell, pilching and rolling' to take
into account. III these conditions, the wave pattern should he ~tudied to
establish the wave cycle. During a series of average waves the mean
lhe
highest and lowesl drau~hl readings should be recorded.
0"
A lotal of J 2 mean readings should he obtained. The highest and lowest means
should be rejected and then tbe average of the n:maining t.en will give the most
accurate reading possible IInder the circumstances.
The forward, an and midships drallghlmcasurements shollld all be found in a
similar £Ishion.
16
QUESTION 1:
The following are mean draught reading~ (in rnctres) over an observed cycle
of waves. Calculate the appropriate draughl.
11.25
9.RO
J J AO
9.70
11.35
9.75
I I.;W
9.60
11.00 9.90
J 1.25
9.70
ANSWER:
Reject 11.40 and 9.(i() m. Add remainder = IOf).
Estimated drallg'hl reading = 105/1 0
= 10.50
Ill.
DRAUGHT MEASURING EQUIPMENT
A measuring device may be llsed to improve the accuracy of the draught
measu rem en t.
..~
--
"....
""
....
"
-.--
'.-
-.-
-
'"
- . ..
"
'
Such devices arc hased on the principle that the turhulence on the surface o{'
the W<lter does not eXlend dowll \0 <lily gre<l( tkplh. They use a long, flexible.
open ended, weighted hose pn~jeclillg downwards to below the turbu\cnre,
17
The device is held directly in h'ont of the draught marks and, after allowing a
few seconds for the tubes (0 fill with water, the mean water level is indicated by
the float.
The float may have a small rise and tall, hut this will be minimal compared with
the wave motion.
~Airhole
r-'~
8
6
Float
4
2
r.
Weight
The device is diHicult to me al the bow and the stern. It should be held close
enough to the draught marks under the overhang of the bow and the stern to
avoid parallax. The device may be attached to the hull by a strong magnet.
A statement describing the prevailing sea conditions should he included in the
survey report to avoid a dispute later.
DRAUGHT READING ON OUTBOARD SIDE
Every attempt should be made to read the draughts on the ()ff.~hore side of the
vessel although, in some situations, this may prove to be impractical or even
dangerous. In such an event, the onshore marks should be read and the other
side calculated wit.h t.he help of a manometer.
18
•
,
1
11~-11 I = 2d
-
,.'
. '
"
"
•
,
,
•
i
i
Deckline
I
cl,:
-
The manometer should comprisc of a short. length of clear. rigid, plastic tube
filted to each end of a hose, to facilitate the measuring of thc water levels. If
possible the hose should stretch the 1tl1l beam of the vessel and the measurement.s
should be taken at the exl.rcmc breadth. The ollthoard reading is found by
adding or subtracting the manometer reading (2d) to the inboard draught..
When this proves impossible, then the mean draught at the celllreline, may be
calculated using similar t.riangles.
\
=
The levels must be measured Ii-om the same base line, and t.aken at equal
dist.ances from the centreline on both sides of t.he vcssel.
All air must be excluded {i'om the hose and the water levels in both tubes kept
at a height which is higher than the deck at the c:cnLrcline.
The heighL~ of water levels, on both sides of the ship, are measured above the
deckJine (h) or some other fixed level. The difference between the two heights
19
is then halved and the result (d) is added to, or subtracted from,
draught reading to obtain the mean draught at the centreline.
the one
QUESTION 2:
The port draught midships = 8.00
111.
The starhoard side is to be found by manometer, where the readings are
taken at 8.50 m on either side of the centre line.
The vessel's ii.lll beam = 20.85 m.
Calculate the midships mean draught (ie. centre line draught) if there is a
dillerence of" 25 cm between the two readings of rhe manometer and the
starboard reading is the higher.
ANSWER:
x 2_
Effective bealll
= ou, ••:")()
By sirnilar triangles
0.25 / 17
I'"'I. 00
-
cl = 20.85 x 0.25/ 17
Half beam diHcrencc
Cenudinc draught
III .
d / 20.85
0.307
= O.:~07 I ~
= 0.153 + S.O()
IIJ
full beam difference.
0.153 m.
-
8.15:~
m.
Not.e: It may be more practical ill some situations to measure the midships
freeboard and fj'om this calculate the midships draught.
DRAUGHT GAUGES
Draught gauges lIIay he very helpful as a check, but should never replace the
reading of" draughts using the fixed drallght. marks Oil the ship's hull.
SQUAT
While measuring the draught, when there is a strong current running and
there is waler depths 01 less than twice the draught of the vessel, the draught
readings may be misleading, due to the eilects of squat.
The survey report shollld include referelln: to l)()ssibll~ sqwll eJJl!us, even if a
suitable correction to the draught readings canllot be determined.
20
CORRECTION OF DRAUGHTS TO PERPENDICULARS
AND MIDSHIPS
Firstly, correct observed draughts, iorward, aft and midships, for the effect of
any list or heel by calculating the mean of port and starboard in each case.
Note; see notes on page 26. as there may also be a list correction (in tonnes) to
apply to the displacement.
Secondly, when the vessel is Irirn.rnRd and the vessel's draught marks are not sited
at the correct position on the perpendiculars; corrections to the observed
draughts must be applied. This incorrect positioning of the draught marks may
be termed misjJIIlt:emlml of marh. it is shown in the photohTJ-aphs on pages 22 and
23.
w:
----1-
AP
1"'--- \
I
I
AP
ait perpendicular
FP
forward perpendicular
LBP
length between perpendiculars
1
D AP draught at aft perpendicular
Da
draught at aft draught marks
D M. draught at midships
Dm
draught at midships draught marks
D FP draught at forward perpendicular
Df
FP
LBP
draught at forward draught marks
21
I
:
Misplacement of marks mlCiShlps
Paul Coombs
Misplacement of marks aft
Paul Coombs
Misplacement of marks forward
Forward correction
apparent trim x distance D FP to Df
distance Da to Df
M1 correction
apparent trim x distance D AP to Da
distance Da to Df
Midships correction
apparent trim x distance D M to Dm
distance Da to Df
Where:
apparent trim
the difference between Da and Df
Sign convention:
If the direction of misplacement of the draught mark ii'om the perpendicular
(or midships position) is the same as the direction of the trim, then the correction
is negalirH! (-) when applied to the observed draught.
Note; even keel would not require the above corrections to be applied.
QUESTION 3:
With reference to t.he following paniculars, calculate the correct draughts,
forward, aft, and midships, if the observed draughts are:
torward
6.~~5
m aft 7.88 m midships 7.12 m
Position of draught. marks:
0.11) III aft. of line of stem at slimmer load line (SLL).
Forward:
Rake of stern = 22°. summer load draught = 10.471 m.
Aft:
6.00
111
forward of AI'.
LBP = 170 m.
ANSWER:
Apparent trim
= 7.88 - 6.35
Arithmetical mean draught
= 7.115 m
Midships draught
= 7.12
1.!l3
III
Vessd nul sullerillg trom hog or sag
24
Distance from SLL
10.471 - 6.350
By simple trigonometry
Tan 22° x 4.121
4.121 m
-
1.665 m
- 1.815 m
Length between marks
+ O.lS
= 170 - (6.0 + 1.815)
Correction forward
= 1.53 x 1.815 / 162.185
Draught forward
= 6.350 - 0.017
Correction aft.
=
Draught aft.
= 7.88 + 0.057
= -0.017 m
= 6.333 m
= +0.057 m
= 7.937 m
Distancc from FP
1.665
162.185 m
1.53 x 6.00 / 162.185
CORRECTIONS WITH HULL DEFLECTION
The corrections to rhe perpendiCIIlars and rnidships assume lhallhe keel or the
vessel is straight. When the vessel is hogged or sagged, these corrections may no
longer be correcL. Thc tabulated corrections in the st.ability information book, or
the formulae on the previous page, must be colTt."Cted to the particular circumstances.
The easiest method to finclt.hcse corrections would be to use t.he t.rim between
the midships mark and the particular end draught t.hen calculate using this half
lengt.h trim, the half length and the distance of the misplacement.
Repeat this procedure al.lhe other end draught mark with the similarly modified
trim, the half length and the distance
misplaccmenl.
or
EXAMPLE:
Obscrved draughts forward 6.00 m midships 6.40
III
an 7.40 m.
Dist.ancc of forward mark from FP = 2.0 m aft
Distance of aft mark from AP = 5.0 m forward.
LBP = lOOm
Total trim = 1.40 m AMD = 6.70 m. Thcrefore the vessel is lwgged.
Trim fi.Jrward to midships = 0.40 m
Forward correction
= 2 x 0.1 1(50 - 2) - - 0.017 m
Forward draught
= 5.983
III
25
= 1.0 m
Trim aft to tnidships
Aft correction
Ait draught
-
5.0 x 1.0 I (50 - 5)
-
·HUII m
7.511 m
CORRECTION FOR LIST
\-\'hen a vessel lists, it often rises in the water. This means that the mean of the
side draughts is a cemreline draught which is less than the actual draught that
would have been observed, had the vessel been upright. This Illay be ignored
for small angles of list, however, if the draught survey is 10 be carried out on a
vessel which has sullcred a cargo shifi or is lying at a large angle of list, then it
should he calculated.
111e correction, in tonnes, to be applied to the displacement, is by the iormula:
Correction for list = 6 (TPC 2 - TPC 1)
X
(d 2 - d) tonnes
\'v'here:
d~
midship draughts on each side.
and d l
TPC ,
-
the TPC equivalent to the draught d I
TPC 2
-
the TPC equivalent to the draught
d~
Sign convemion: Always positive (+).
QUESTION 4:
Vessel is listed 5°. The draughts midships arc:
Port
G.OO
III
(equivalent TPe 32)
Starboard
8.00
111
(equivalent TPC :\4)
ANSWER:
Correction = 6(34 - 32)(8.00 - fi.OO)
=
24 tonnes positive
(+ ).
Note; it. will normally be a slllall correction.
HULL DEFLECTION OR HOG AND SAG
When the observed draughts have been corrected for list and displacement. of
marks, an arithmetical mean ofrhe forward and ail draughts must be calculated,
ie. the arithmetical mean draught (AM D).
26
Compare the AMD with the corrected midships draught to establish whether
the hull is distorted. The AMD should cYllal the draught mid ships if the ship
is neither hogged or sagged.
Actual freeboard
•
.---
I
,
Anllal clraug-ht ~ ,AMD
-------
HOG
SAG
Actual
fr~_ehoard,
---
•'---r-
Actual draught ~
AM D
If the actual draught is less than AMD then the vessel is hogged.
If the actual draught is bJTl!fllm- than AMD then the vessel is
~agged_
METHODS USED TO CALCULATE THE EFFECTS OF HULL
DEFLECTION
Every effort should be made, taking into account the information available, to
determine the appropriat.e correction for hull deflection. The ultimate accuracy
or the survcy rcslllt~ are normally dependant on this correction.
It is difficult to establish the ship's distorted shape precisely but the {allowing
factors should be t.akell into account:
Residual deformation
Cargo distributioll
Bunkerslballast distribution
Daily variation.
Larger
vessels can be liable to daily. variations in the amount of hull deflection.
.
By day, the sun heats the upper parts of the vessel, resulting in a hogged
condition. The same vessel may sufler sagging when the upper portion loses its
heat at night.
')""
_I
The assessment of the vessel's shape will eSlablish the appropriate draught to
enrer the hydrostat.ic dam, in the stability information book. This will determine
the displacement for that particular insGll1l.
METHODS
There are several methods ofca\culating the correction for hog or sag. Agreement
on the use of one of these alternatives must be made before the proposed voyage
begins and adhered to until the voyage ends. These methods only t.ake into
alcount. hull deformation or deflection.
Method 1.
Some ship's stability information books have a table of corrections to apply to
the extracted displacement. When this table or graph is used, then this faCL
should be stated on the repon so that it can be used throughout.
Method 2. (The most common and simplest method)
Assume that the deformed shape of the vessel follows a regular mathematical
curve.
This correction is dependant on the block coefficient.
(i) For finer lined vessels:
Mean Adjusted Draught _ (6 x D M)
+ D FP + D AP
8
This is oft.en referred to as "the mean of mean of means".
(ii) For fuller fonn vessels, and box-shaped vessels:
Mean Adjusted Draught = (4 x D M) +6 D FP
+ DAP
Where;
Mean Adjusted drall!;ht
Draught midships corrected for hog
and sa!;.
DM
o FP
Draught midships.
OAP
Draught at aft perpendicular.
Draught at forward perpendicular.
28
QUESTION 5:
The "esse! has a sleek (urm lor a last f.Mssage ,
deflect.ion.
bUI
The drallghts ar the perpelldiculars arc /clrward 5.64
The draug'hl midships is G.ll
is slIffering from hllll
III
aft. 6.42
III
Ill.
\Vhat is the true mean draught. taking illto
an:OIIllI
Ihe dis\orlion olthe hull.
ANSWER:
\fean adjusted draught
_ (G x G,ll)
+ 5.G4 + (JA2
H
-
(i.()~) III
Method 3.
' I'his correction is dependem 011 the cuelIirie III of fineness (wa Icrpla lie coefficient),
The codlicicnl is lIScd 10 enler the graph (inclllded in some stability infi.Jl'IIJalioJ\
books) to obtain a "[leLor".
F
0.8
I"---
A
C
0,7
~ r---......
.......
T
0
R
~ -.........
0.6
O.(i
0.7
O.R
0.9
\VATERPLANE COEFfICIENT
Then:
Mean adjusted draught
= AMD + factor(D M - AMD)
QUESTION 6:
A vessel is lIoating at the (ollowing draughts:
forward 5.80
III
ah 6.20 m midships 6.) 8
III
Note: These draughts have been corrected to rhe perpendiculars, and midships
marks.
29
Calculate the true mean draught raking illlo account the distortion ofthe hull
using the waterplane coellicient table. The watcrplane coefficient. tabulated
in the stability intt')\'mation book = 0.60
ANSWER:
Extracted factor
-
A.M.D.
- (5.80
Mean a<ljustcd draught
0.76
6.00
+ 6.20) / 2
+ 0.76(6.18
= 6.00 m
- 6.00)
=
G.t:n
m
Method 3 alternative 1.
The extracted tactor can be used directly to determine a correction in tonnes to
apply to the final displacement.
Correction (tonne)
\\,'here:
hog/sag' (cm)
= factor x TPC x hog/sag (cm)
- (D M - AMD) x J on
Method 3 alternative 2.
The g-raph or table iL~elf may be adapted t.o give a correction table dircctly in
t.onnes (i.e. tactor x TPC) tC)!' each ccntimetre or hog or sag. This would giye
a correction to apply to the final displacement by entering the table with the
AMD and the hog/sag in ems.
Other alternative methods
These require addit.ional draughl/freeboard measurements at points other than
perpendiculars and mid ships, along the vessels length. This is very diHicuh. to
est.ablish. See Data manual Jor draught sW've)'s, pages 8 and 9.
CORRECTIONS FOR TRIM
There may be a total trim correction table included in the stability infi)rmation
book. This will normally combine the following J st. and 2nd, conn:lions. Find
oUl what it includes, and examine the ships st~lhilit}' data carefully before
conduct.ing a survey.
FIRST TRIM CORRECTION (CORRECTION FOR LAYER)
The displacement scale is normally calculaled on the assumption that the vessel
is lying on an even keel. The first trim correction is to correct. the draught
midships to the true mean draught., at. the centre of flotation.
30
This correction is known as the correction lor layCJ" (or layer correction).
AP
Wl -
FP
,
I
I
,I
if
I
i
[ er
\,\1
.
I
"-.
TMD
I'
Layer CorrectionL ~ Trim
,
AMD
I
./,
-
L
- --
' -"-
.,
,
1- -- - -
LB]>
-,
I
FP
AP
air perpendicular
TMD
true mean draught
AMD
arithmetical mean draught corrected filr hog' or sag
LCF
longitudinal centre of flotation
LBP
\en glh bet.ween pCl'pcmliculars
lorward perpendicular
Layer correction(metres) = (distance LCF to midships) x trim I LBP
thcn
TMD
= AMD ±
layer correction
1st trim correction (tonnes) = layer correction x TPC x 100
Metric:
1st trim correction(tonnes) _ (distance LCF to midships) x TPC x trim(cm)
LBP
Imperial:
1st trim correction(tons) _ (distance LCF to midships) x TPI x trim (inches)
LBP
Actual displacement = tabulated displacement ± 1st trim correction
Sign convention:
Trim
LCF aft ()f mitMij)s
LCF for..vGrd of miashlj)s
AJt
negative (-)
positive (+)
FOl1l1flrd
positive (+)
negative (-)
31
QUESTION 7:
A vessel of LHP 1.10 m has the {(JlIowing draug-hts: forward 6.85 m aft 7.25 m.
The LCF is situated at a position iO m forward of' tilL AP.
TPC = 40.
Calculate the first trim cOlTeujon in tonnes.
ANSWER:
_ 5 x 40 x 0.40 x 100
I st. trim corn:ct.ioll
- + !);~ tonnes
150
SECOND TRIM CORRECTION
This is a correction {(Jl' the shift. of t he centre of flotation (LCf) which occurs as
the vessel changes its trim. The position of the L<:I-', as specified in the
hydrostatic paniClliars, is normally lor the e\'en ked condit.ion.
The draught at the final positioll of I.CF is required.
Metric
2nd trim correction (in metres)
=
trim(m) x (MCTC~_. MCTC,l
2 x TPC x LBP
Where:
~vIC'J'C~
I\·lCTC for the draught at the AP
and
~-1Cn~l
I'vlCTC for the draught at the FP
or
vice versa when trimllled by the head.
Howcyer the 2nd trim correction is normally, calculated in tonnes as follows:
2nd trim correction (in tonnes)
=
•
2
50 x trim (m) x (MCTC 2 • MCTC,}
LBP
Where:
MeTc" -
MeTe for mean adjusted draught
and
MCTC 1
~ICTC
+ 50 cm
for mean adjusted draught. -
!)()
cm
Imperial
2nd trim correction (in tons)
=
6 x trim(ft)2 x (MCT1"2 - MCT1'\2
LBP
Where:
MCTI"2
~ICTI"
for mean adjusted draug'ht
and
MCTI"I -
I\ICTI"
{(Jl'
Sign convention:
+ () in
mean adjusted draught - () in
Always positive (+)
'1 ')
.l_
QUESTION 8:
A vessel is floating in salt water with an AMD of 6.10 m corrected for
deflection and a trim of 1.4 m by the stern.
Extracted values from hydrostatics:
,",{('T('
1"
-"
-" t'01. 6 . 60 -
MCTC lor 5.60 = 310.0
'!<)')
l'
:1
__ .,.'
LRP = 170 m
Calculate the second trim correction in t.onnes for the vessel in this conditiun.
ANSWER:
Trim = 1.40
III
2nd trim correction
-
"(")
:J
<~ X"r)2')
x 1.or
.J _..(J
- .~ll())
'
170
- + 7.4 tonnes
DENSITY
Determine the water density at the time of taking the draughts using a gloss
hydrometer, designed f(Jr draught surveys, and marked:
1. M edium surface tension
2. Apparent density in kg/lscale range between 0.990 to 1.040
Note: 1.000 kg/l = 1.000 t/m J
;). Instrumental standard 15° C.
The instrument sholJld he provided with a cenilicate or conlimnit)' with a
maximum error nol exceeding "x" kg/l tested against a natiomll standard. Sce
photograph on page 13.
If the hydrometer used is graduated with a dinerent scale to that quoted above
r.hcn it is not t.he standard type so additional corrections may be required, see
conversion details tor Altemotive H.'Vdromdl!n on page 53.
CORRECTION FOR DENSITY
Actual displacement ==
tabulated displacement x density 1
density 2
\\!here:
density 1 = average density of water sampled.
density ~ = density specifieu in the hydrostaLic information.
33
Taking a ballast sample
Hydrometer showing meniscus using a mirror for the rear view
34
The sounding tape
Paul Coombs
The tools of the draught surveyor
35
Note:
1:
Do apply the hydrometer index error, if any. Tt is quoted on the
certificate.
2:
Do
j:
Do nol cHljust the draught for the density, but do COITeC[ the
1101
apply any correction for temperature.
displacement instead .
4:
Do enter the hydrostatic tables with the actual TMD, irrespective
of' density, clllci then convert t.he extracted value to the correct
density at the final calculation. See check list page!) 1. It. is wrollg
to convert the TMD to a salt wmer Tl\.fD and then cntcr the
hydrostatks.
5:
Do extract \ICTC, LCf ete. {or the actual TMl) and use these
extracted values to calculate the 1st and 2nd trim corrections.
6:
The stability int(mnation book should quote some form of relationship
between weight and VOIUlllC:1 cubic metre of tj·esh water
-
1.000 tonnes
I c1lbic metre of sail water
-
1.025 tonnes
or similar figures.
This /'xlulI/,lp. giilP..\ flfJj](Jl"ent ljrusily in the same
units used by Ih" Zeal dmllghl SlIJ1J(,' h)'rlrll1l/1d(~1".
QUESTION 9:
.rile extracted hydrographic displacement equivalent to rJw observed draught
of 5.30 m = 15250 tonne for salt. water where I m:i of salt water = 1.025
tonnes.
Find:
true displacement if the
ANSWER:
Actual displacelllcllL
a\'erag(~
ohserved apparent densit.y -
- 15250 x 1.015 / 1.025 -
3G
1.015
15)01.2 Tonnes
t/lII:l.
ASSESSMENT SUMMARY
The corrections in this chapter rnay he applied to the observed draughts to
convert them to a draught that can be used to elller the ship's hydrostatic
particulars in order to determine the correct uisplacement.
Some of the cor~ecti()ns Illay be calculated in tonnes or in metres. Experienu:
anu speed of calculation has shown that the latter corrections should be calculated
in tonnes (instead or metres). and used to correct a value of displacement
extraeted fi'ol11 the hydrostatic pal'liculars in the stability information book.
The observed draughts are corrected to the perpendiculars and midships. the
hull deilcction found and the hydrost;ltics entered with the cOlTecled arithmetical
mean draughl (Ai\-ID). The displacement extracted is then adjusted with the 1st
and 2nd trim corrections and the correction fiJr density. all in tonnes.
See (orrer:liom
du~d( li.\l
on page 51.
DEDUCTIBLES
The deduclibles arc l.he components of the ship's total weighl, which must be
rleducted from the calculated displacement in order to determine the wcight of
cargo on board.
The lotal weight of the ship will be made up of:Light displan:lIlclll, (remember; components may be missing c.g ..
anchors our).
Cargo
Ballast
Fuel and fresh water
Swimming pool water and oLllcl' casily lorg'onen weights on hoard
Slores and Pro\'isiol15
Crew and
efTccL~
Slorcs. provisions. crew and their effects arc likely la be constant during a
draught survey. and could tIC added on lo the light displacemem.
Preparations
Examine the releyam basic ship's plans showing the layout of pipes and lall ks.
indlldin~ Ihe locatioll of'l.hcir sounding' pipes.
l\'lake a note or the tank dimensions. referellce heights and obtainlhe aulilOrised
calibration tables for these t.anks.
Remember that aUl.omatic gauge readings (if lined), should he nOled fin' comparison
against the manu(11 readings.
SOUNDINGS AND ULLAGES
The li(IUici 'IlIantities or ballasl, (tiel and li'esh water, musr be very carefully
measured as soon as possible alter the draughls have lJel.:lI read .
A sounding is the measurement from Ihe slriker plate on the base of the tank
IJdow the sounding pipe Lu Lhe top ofthe liquid. See photograph on page ;):1.
or
When laking a sounding, always check thc tape is aL lhl.: bOLlum
the tank, by
checking the fullmeasul'emenr from the slriker plate to the top of the sounding
pIpe.
An ullage is the measuremenr from the surfacl.: of the liquid to a fIxed datum
pOilll, usually rhe rop of the soullding pipe.
Measure and record soundings (or ulJages) for cvery lank in the ship.
Check the bilges filr any liquid.
Some tanks may have two sounding pipes, check both. paniCIIlarly if the ~hip is
trimmed.
The sounding tables should be part oflhe ship'~ approved documentation, they
arc produced when the \'essel is built and therefore may have become less
accurate, with the passage of time.
SAMPLING
By sounding a tank and using the sounding tables. the \'olume of liquid is
found. \Nith the appan:nt density of the liquid,
Mass
it~
mass can be determined.
= volume x apparent density
Tt is most imporrant that each tank should be sampled for density as well as
being sounded for volume. Sce photograph on page ~H.
Apply the temperature correction to the dellsity readillg- hd()H~ using it to
calculate Ihe quantilY ofhllnkers in Ihe tank, when doing a bunker tank survey.
It is not normal to apply a temperature correction when determining ballast
quantities.
TRIM CORRECTIONS
The sounding pipe should be positioned at a point within the tank when: it will
always provide the correct sounding applicable to the sOIJll<lillg-lahlcs, regardless
of Ihe ship's Irim. However, this position is not always possible lo achieve and
correction tables for trim should then he available t.o use with the sounding
tables. These corrections should be calibrated 101' every haIr melre of Irim, by
Ihe head and hy I.he slern, over the operational range 01" trims. Alternatively.
sounding tables for differem trims may he pw\'idcd.
Sounding pipe
~-
d-~
~+.~------~----------~
1
,","""""",,,,,,,,,,,,,,,, "
. " ..... ,"'" . " . " ... ,... """"" ..... """.,.,,.,., ...... ,.,, .. ".,.,.,."".
Tallk Centre
,,,.,.,,,,,,
lfno corrections are available, it may be necessary to calculate them. Appropriate
measurements can be taken from the plans of lhe tank.
Correction to sounding (x) = d xL~;
where d is the distance from lhe sounding pipe to the tank centre.
Sign convention:
Sounding fini/)ard of lank an/re
TRiM
SOU1uling aft of centre
Forward
Negalive (-)
PoSili ve (+)
Aft
Positive (+)
Negative (-)
Note: the accuracy of this formula is acceptable, provided the hottom of the
t.ank is covered with liquid, and the tank is approximately rectangular.
QUESTION 10:
A ship, LB P 120 m, has a trim of' 2.0 m hy the st.ern. A sounding was taken
in a reclangular double bottom tank, and found to be 1.05 m. If the t.ank
measured length 24.0 rn, breadth 8.2 111, and the sounding pipe was 3.0 III
forward of the afL bulkhead, find the volume of liquid in the tank.
,
8.~
24.0
3.0
1.05
ANSWER.
d x trim
Correction to sOllnding
LBP
0.15
III
Observed sounding
-
1.05 m
Even keel suunding
-
U.gO m
-
24.0 x 8.2 x 0.90
Volume
or liquid
9.0 x 2.0
120
40
-
177.1
111 3
\Vhen a vessel is trimmed a tank may appear full hut have a large void space
immediately forward 0(" the sounding or ullage poim.
Alternatively, a tank may have no soundin~s and appear empty, but still have a
considerable quantity of liquid remaining in it.
LIQUID SLOP TANKS
Where small quantities of ballast water remain in a hallast hold, on a trimmed
ship, this quantity must be included in the assessment.
is possible to calculate the volullIe oi'this wedge ofliquid, b'om one sounding,
using the wedge formula.
[t.
The wedge iormula was developed in order to detennine small volumes of
cargo "remaining on hoard".
The formula assumes a {i'ce nowin~ liquid on an upri~ht, but trimmed vessel,
and also it assumes a recL1ngular L1nk where the sounding is not constrained by
a sounding pipe.
The wedge f(H'll1ula is:
Wedge volume = LBP x breaddt of tank x (corrected sounding)2
2 x vessel's trim
y
'\
I
-
J
,
~
P'"
,l-
"1
J
PI
4
The corrected sounding can be calculated by the following approximate formula:
41
Corrected sounding (P) == observed sounding (PI)
+ distance
(y) x
tB~
Where the distance "y" is the distance £i'olll the suunding position to the end
bulkhead.
QUESTION 11:
From the following information, lind (he volume of oil remaining' in a lank
where the sounding was 0.2 m.
LBP ISO
Irim 2.0 m by (be stern, breadth of tank 12.5 m,
position 5.0 m forward of af! bulkhead.
Ill,
sounding-
ANSWER:
Corrected sounding
sounding + distance x trim/LBP
0.2 + 6 x 2/150 == n.2 + 0.08 == O.2Hm
\Veclge volume
LB» x breadth x corrected sounding~
trim x 2
1~-0
X
1')!:
_.~.I
X 0,)0"
._0"
2.0 x 2
MIXTURES
\Vhen conduclinp; a blinker survey and the vessel loads hunkers, this could he
mixed with bunkers already on hoard. The relative deIlsity (RD), or density, of
the mixture must be used to calculate the total quantity of the oil in the tank.
The final RD
or the mixture can be found by the lollowing formula:
RD of mixture
(ori~inal
volume x original RD) + (loaded volume x loaded RD)
original volume + loaded volume
RESIDUE IN COMPARTMENTS
or
Tanks for liquids. particularly hallast tanks, are subject to the build up
residues and scale. The quantity of sediment is ditlicult la assess without
entering the tank.
42
The ellec!. on !.he ballast calculations can be minimized hy leaving a measurable
quantity of water in the tank instead of pumping it completely dry. The
calculations then use a known amount or water which can be deducled from the
displaccmcnt. The error due to the unknO\vn weight or sedimem is reduced to
the diilcrence between the dens it\!, of water and the density, of the sediment.
This accumulation of sediment will reduce the deadweight capacity of the vessel
and t.herefore should not be allowed to accrue indefinitely.
,
I nspcct ballast tan ks if in any doubt abollt the qualllity or sediments, There are
patent chemicals available to put the mud imo suspension, so that it may he
disposed of with the water in an appropriate and safe manner, when a suitable
opporLunity allows. However, these may not always he elIective; when a hard
crust has developed Oil I.he top of the mud, it. can sometimes only be rellloved
by hand.
ANCHORS AND CABLES
The anchors may be in the housed posit.ion, where they contrib1lte 1.0 the
lightship, or t.hey may have been used in the mooring of the ship. Then the
anchors will be on the sea hed along with a !,riven length of cable. The loss of
weight due to its removal is weight t.aken from the light displacemenl., this
amO~1l11 should therefore be added 1.0 t.he quantity of cargo. 'fhere should he
infiH"lnal.ion available on hoard to enable the SIl["VC}'O[" lo establish or calculate
the weight of the missing anchor and cable.
In the case of the chain cable, it. can be calculated with reasonable accuracy, bv,
I.he (ollowing formula:
Weight per shackle (tonne) = 15 x (link diameter in cm)2 x 3.87
1000
The link diameter is the diamet.er or the steel rod which makes up each
individual link. ] 11 t.he case or the anchor iL~dr, this will vary from ship to ship,
but.this informat.ioll should be available on board. This anchor weight should
be rounded to the nearesl. hall" tonne.
43
ADDITIONAL FACTORS
1.
It should be appreciated that the cargo may (hange it1; characteristics
o\'er a period oftime. The moisture content varies with the atmo1;pheric
conditions, and liquid drains into the hilges. The reIIloval or bilge
water between the two surveys should be noted. This is also important
during a voyage when a welted cargo may lose its moisture cont.enl and
later cause a dispute OVCI' cargo quantities.
2.
The changes in the condit.ion of the n:ssel such as the accumulat.ion of
rain water, ice or snow, could he sig'niiicant and should be accounted
for in the calculations.
:\.
The swimming pool call hold considerable quantities of water, which
could cause a discrepancy if the pool is emptied, or filled, Juring the
period between the be/ore and after draught surveys. In this GiSt: a
correction must b{~ applied to t.he resulls.
4.
All spaces should be inspected to ensure they are the same at both the
initial and filial surveys, not iorgening spaces such as the duct keel,
peaks, cofferdams, ere.
REMEMBER:
The accuracy of the survey depends on diligence!
44
GLOSSARY
BI.oCK COEFFICIENT The ratio of the unrlerwatcr volume of the vessel to
(Cb):
the volume ofa rectangular block ofthe same overall
dimensions.
BREADTH (BEAM):
l\faxirnurn width of the ship.
l'vloulded Breadth:
\Vidth of the ship amidships, measured inside the
shell plating.
CENTRE OF
FLOTATION (CF):
The cenrroid of the waterplane area. It is the point
about which the ship trims, heels and lists.
LOlIg'iluciinal Centre of
Flotation (LCF):
The distance of the centre of flotatioll from midships
or the aft perpendicular.
DEAl)\\'EIGHT:
The dilIerence between the light displacement amI
t.he loaded displacement. It is the carrying capacity
of" the ship and indudes the weight of cargo, ballast,
fuel, water, stores, crew and effects.
DENSITY:
The mass per ullil volume.
Apparent Density:
'l'he weight in air or a unit. volullle.
True Densit\':
,
The weight in
Relative Density (RD):
The ratio of the weight of a substance to the weight
of an equal volume of fi'esh water,
RD of n'esh waLer: 1.000 at. 4°(;
RD of salt water: 1.025 at 4"C
The term speci/lc gravity, previously used in place of
RD, is no longer IIsed wit.h SI units.
DEPTH:
Distance h'om the top of the deck plating at the side
of the ship to the hottOlIl of the keel.
Moulded Depth:
Distance h'om the keel to the deck at the ship's side.
measured imide of the shell plating.
a \'aCUUIll
of a unit volume.
DISPLACEMENT:
The mass of water displaced by the ship. It represent~
the lOlal weight of t.he ship and is calculated by:
volume of displacement x density of water.
Light Displacement:
The displacement of the ship and superstructure
wit.h all fixed equipmcm pills engine room spares
and with water in the boilers to working level. Also
referred to as LiKhtship or Lightweight.
SUlIllller Load
The displacement of the ship when loaded to her
SUIIIIIler load lillc.
Displacement:
DRAUGHT:
The distance !i'om the bottom of the ked to the
waterlinc. S(Jmelimc,~ spelled dmft,
Aft Drallg-ht:
Thc disLancc fi'olll the bot.tom
the ked to the
waterline on the
perpendicular when the ship is
upright.
Midships Draught:
The distance {i'om the bOllom of the ked to the
waterline at a position midway between the
perpendiculars.
Forward Draught:
The distance from the bottom of the keel to the
waterline Oil the forward perpendicular when the
ship is upright.
Arithmetical Mean
Draught (AM D):
The arithmetical mean of the forward draught and
t.he ali draught.
True Mean Draught
(TMD):
The draught at the celllre oi' flotation.
EVEN KEEL:
Whcn the liJnvanl and aft draughts arc the Sall1(~,
the ship is said to be on an even keel. The ship's
hydrostatic data is calculated 101' this condition.
FREEBOARD:
The distance from t.he waterline to the upper surface
of the h'eeboard deck al the ship's side.
an
46
or
Assigned Summer
Freeboard:
The disLance from the upper edge of the summer
load line to the upper edge of the deck line.
FRESII \-VATER
ALLOWANCE (F\:VA):
The amount Iw which the summer load line mav be
submerged in fresh water.
llEEL:
The ship is heeled when inclined by an external
force.
HOG:
The condition of a ship when it is delonned so that
the forward and aft draughts are deeper than Lhe
midships draught.. It is referred to as a hull d('jlectioll.
I.ENGTH BET\'VEEN
PERPENDICULARS
(LBP):
UisGlIlce from the lorward perpendicular to the aft
perpendicular.
Aft Perpendicular
J
J
(AP): A perpendicular drawn to the w;lterline at the point
where t.he aft side of the rudder post meets the
summer load line. Where no rudder post is filled it
is taken as the centre line of the rudder stock.
Forward Perpendicular
(FP):
A perpendicular drawn to the waterIine at the point
where the fiJreside or the stern meets the summer
load line (or load wawr line LWL).
LENGTH OVERALL
(L or LOA):
1\1aximuIll length or the ship.
LIST:
The ship is listed when inclined by weights within
the ship.
The mass of an object is the quantity of matter it
mnlains and is calculated by:
volullle x density
l\HDSIIIPS:
The point midway between the forward and all
perpendiculars. The centre of rhe load line circle
should indicate Lhis position.
47
MOMENT TO
CHANGE TRIM PER
CENTIMETRE
(MCTC or MCT 1 cm):
The moment of the weight (i.e. weight x distance)
required to change the trim of t.he ship by 1 cm.
SAG:
The condition of a ship when it is deformed so that
the midships draught is deeper than the forward
and aft draughts. It is referred t.o as a hull dejleclio'l!.
SOUNDING:
The distance from the bottom ora tank t.o t.he top of
the liquid wit.hin it.
TONNES PER
The weight which must. be loaded or discharged to
change the ship's mean draughl. hy I cm.
CENTIMETRE
IMMERSION (TPC):
TRIM:
The diilerence between the filrward and ait draughL<;.
Apparent Trim:
The difference between the draughts observed at
the forward and afl. drallght marks.
True Trim:
The difference between the drallght:; at the forward
and afi. perpendiculars.
ULLO\GE:
The distance above a li(lIlid, within a tank,
measuring point at the top of the t.ank.
VOLUME OF
The volume of water displaced by the ship and is
calculated by:
lengt.h x breadth x draught x Cb.
DISPLACEMEN'I':
WATERPLANE
COEffICIENT (Cw):
WEIGHT:
lo
the
The ratio of t.he area of t.he ship's waterplane to a
rectangle of the same ext.reme dimensions. Also
known as the co~fricient oIJiulfIless.
The weight of an ol~ject is the force it exerts on
anything which freely support.s it.
48
ApPENDICES
E;QUIPMENT C HECK L 1ST
Sample j<lr and water sample bucket with line
Ballast tank dipper with line
Small hand pump with hose 10r taking samples
Draug-hl survey hydrometer with certiiicate
Steel sounding tape with gradual ions in metres and feet
Water finding paste
Draughlffrceboard measuring clevice
1\..fanometer if some draughts an: impossible to read, plus a long
measuring tape
-
Plastic tube with plug, to act as sounding pipe extension
Boat available to read inaccessible draughts
Pilot ladder on board ready for obtaining draughts
Docu mentaLion
Pocket computer with draught survey program or calculator
CHECK LIST OF RESERVATIONS
(Not all exhaustive list)
Height of waves / swell
Clarity of draught marks
State or tide - underkcd clearance
Squal effects
Variations in density
Daytime I night-time
Anchors moved, in or out
lee /
Quantity of bilges pumped
Residue in l<lIlks
SuspecL calibrations
Ship movemellls
49
SIlUW UIl
deck
INFORMATION CHECK LIST
GENERAL INFORMATION
Ship's name
Call letters
l'ort. of registry
Flag
Year built
Master
Owners
Owner's address
Owm:r's agel1\.
Managcr/operator
Charterer
Chanerer's
Shipper
Chief OUicer
Chief Engineer
SlII'veyor/s
P&l correspondent
Ship's lo(:at ion
Survey requested by:
Sllney, on account or:
Typl: of Cirgo
Weather conditions
Date and time of arrival
a~ellt
THE STABILITY INFORMATION nOOK
Length between perpelldieulars
Extrellw alld moulded hreadth
Overall and moulded depth
Summer draught and fj"ecboard
Summer displaccllwllI and deadweight
Misplacemcnt of draught marks fi"o!H perpendiculars and midships
Lightship displacement with lightship constant
Hydrostatic particulars:
Displacement, TI'C, MCTe, Len, LCF
(:apacity plans and tables
Correction tables:
Trim
Position of marks
List
Hull deflection
PLANS
General arrangemcllt plan
Profile plan indicalin~ each space in t.he ship
OTHER SOURCES
Sounding tables and corrections ti.lr trim
Qualllil), of bUllkers
50
CORRECTIONS CHECK LIST
OBSERVED [)RAlJGIITS:
aft ... P & S
Forward ... P & S
Mean values, ie.
draughL~
midships ... P & S
at. centrclinc, {(Jrwanl, alt and mid ships.
Correct {i'om marks lo perpendicular and midships positions.
Misplacement opposite to trim, then positi'ue (+)
Misj)/arement same as
Iri'lII,
fhen negative (-)
IIog/sag' correction (mean of mean of means, or similar).
negative (-) for hog
j)osititJf (+) for sag;
CORRECTED MEAN DRAUGHT ... t.o cnt.er hydrost.at.ic t.ables.
Displacement from displacement rabic.
First trim correction or Correction for layer (in tonnes).
LCF same as Irim, Ihen positive (+)
LCF ojJposite to Irilll, Ihen negative (-)
Second trim corrcction (in tonnes).
Alwa)ls j)(},lilive (+)
List correction (in tonnes).
Always
1)(}.\'iliv(~
(+)
Correction for density• .
Less than salt waif!r densil)l, then negative (-)
CORRECTED DISPLACEMENT.
51
METRIC/ IMPERIAL CONVERSIONS
I Foot ................................
-
0.3048
Metres
1 Foot ............................... - 30.48
Centimetres
1 Incll .......................... ,
2.54
Centimetres
-
39.37
Inches
I Metre ............................... '"
-
3.28
Feet
1 Centimetre ....................
-
0.3937
Inches
0.028317
Cu.Metres
I Metre ................
lOt.
t .............
I Cll.Foot. ........................ -
1 Cll.Foot ......................... - 7.4805
U.S.Gallons
I Cll.Foot ......................... - 6.2324
Imp. Gallons
1 Cu.Metre ......................
- 35.3148
Cu.Feel
I Cu.Metre ......................
-
U .S.Gallons
1 Cu.Metre .......................
- 6.2898
U .S.Barrels
1 Cu.Metre .... ,t ••••••••••••••••
-
220.0
Imp. Gallons
1.016047
Metric Tonnes
0.9842064
Long Tons
1 Long Ton ......................
1 Metric Tonne ...............
-
264.167
1 Metric Tonne ............... - 2204.6223
Pounds
1 Metric Tonne ...............
U.S.Barrels
6.2898
1 U.S.Gallon .................... - 0.13368
Cu.Fcet
I U .S.Gallon .................... -
ell.Inches
I U.S.Gallon ....................
231
= 8.33
1 U.S.Gallon ....... ............. = 0.833
52
Pounds of fresh water
Imp. Gallons
1 Imp.Gallon .................... = 277.3
1 Imp.Gallon ....................
=
0.16045
1 Imp.Gallon .................... = 10.0
Cu.Inches
eu.Feet
Pounds of fresh water
WATER
I Long Ton fresh water ... -
35.9
Cubic Feet
1 Long Ton salt water ...... = 35.0
Cubic Feet
FUEL OIL (RD 0.944)
1 I...ollg Ton .......................
1 U.S.Gallon .....................
=
=
6.77
U.S.BaJTds
7.88
Pounds
DIESEL OIL (RD 0.85)
1 wng Ton ... ..... .... ............ = 319
U.S.Gallons
1 Metric Tonne ................ = 311
U .S.Gallons
1 U .S.Gallon ..................... = 7.09
Pounds
LUB. OIL (RD 0.90)
1 Long Ton .. ....... ....... .......
1 Metric Tonne ................
=
=
298
U.s.Gallons
294
U .S.Gallons
1 U.S.Gallon ..................... = 7.51
Pounds
ALTERNATIVE HYDROMETERS
To correct to Apparent Density (density in air) from a hydrometer calibrated
1n:-
True Density (density in vacuo)
minus (-) 0.0011 glml
Relative Density (15OC/4"C)
minus (-) 0.0011
Relative Density (15CC/15'C)
minus (-) 0.002
Refer to pages 6, 33 and 36.
Note: glmt = kgll = tlm 3
53
INDEX
Deadweight or Displacement
Scale 11
Deadweightsurvey IV
Density ~, 33
Depth ofship 9
Displacement 9
Diurnal variation 27
DrXllment,ltion and iniormation ~
Draughtg"':lllges 20
Draught measurement 16
Draugh t mcao;uring eyuipment 17
1)raught reading' on outboard side 1H
Draught survey iv, 16
Draughts 3
Aft draught 9
Air pockets 1
Anchors and cables 2, 43
Apparentdensity 3, 6, 9, 36, 39
Apparentlrim ~4
Atithmetic mean draught. 10
Automatic gauges 38
Bale space 11
Ballast ·1
Hallast.holds 1, 5
Ballast samples 5
Ballasttanks 1
Bilge waleI' 44
Bil):?;es 39
Box-shaped vessels 28
Bunkcrsurvey ~, 5
Final survey 6
Finer lined vessels 28
First trim correction 30
Forv.·ard draught 9
Frccboanl 3, 9
Fuller form vessels 28
Calibration lclbles ~
Capacity plan and tahles 11
Centre offlot.ation 32
Chemicals 43
Code of unifclllTl standards and
procedures iv
Coellicient of fineness 29
Constant ]5
Conu:t.ed sounding 41
COlTection tor density 33
Conection ie)r layer 30
COIH.x:tion fi ,,"lisL 26
COITections 10r tlim 30
Corrections with hull deflection 25
Data Manual For Draught Surveys
(rl.'ncral arr,mgeJllent plan
Grainspace II
Growth oflightship 14
Hog 26
IIulldeflection 12, 26
Hydrometer :~, 6, 33
H ,vdrostatic Particulars 9
Ice or snow 44
1ndining experiment
~
54
14
14
L1yerCOn"ection 10, 3]
Lighto;hip 14
Lighto;hip draught. 11
Jjst 96
~
l.ongitudinal centre offlotation 10
Longitudinal measurement 2, 8
Manometer 18
Master's responsibiJjt)' 8
Mean of mean of means 28
MeasllIingdevice 17
M icio;hips 21
Misplacemenr of marks 21
Mixmres 42
Moisturccontent 44
Sounding tables 12
Squat 20
Slahility inicmnar.ion book ~
Stores, provisions, crew 38
Striker plate 38
Smllmer load draught 11
Swell 16
Swinuningpool 44
Telll perature cOl1"ection ~39
Trim 21, 30
Trimcon-ection 12, 39
Trim mctors 10
Trimmed hvdrostatioi 10
True Density !13
'I 'rue mean draught J ()
.
Pell)endiculars ~ 1
Position of marks 12
Prior to arrival ]
Ullage ,38
UN/EeE dr,mght survey code
forms iv
Relative Density 5:~
Remaining on board 41
Residual defimnation ~7
Residuesandsc.'ale 42
Veltical measurement
Volume 16
R
Walerplane coefficient 30
'\I\Taves 16
VVcdgclorIllUla 41
Weight of the ship 38
_
Sag 96
Sample bucket 3
Sampling 3!J
Second trim correction 32
Sediment 42
Slop L,U1ks 41
Sounding ;18
Sounding cOJ,.ection lables 12
Zeal draught. survey
hydrometer 3, 36
55
DRAUGHT SURVEYING
A MANUAL FOR MARINE SURVEYORS
AND SHIP'S OFFICERS
This book colllains the mathcmatical proofs and derivation of all the
formula likely to be requircd in any draught survey. It deals more
hIlly with all the aspects mentioncd in nil' Guidt' To Good Practice.
The book ranges fwmthe basic physics to the most complex corrections,
in simple lallg"uagc and with examples and illustrations. for casy
understandillg". It is suitable [or the new and the experienced
surveyor who seeks a mastery of the subject, or the ~laster rvJariner
who needs 10 knmv the principles invoh'ed.
DRAUGHT SURVEYING
A DISTANCE LEARNING COURSE
The distallce leamillg course is designed [or the beginncr who
wishes to learn about draught surveying [rom the basic principles of
hydrostatics and ship stability. It is [or those \'"ho wish to study the
subject in dept h and follow a properly structured course together
wilh full tUlorial guidance and support. The work is divided into
seC! inns, each
which has examples to study and questions to
anSlver. Each section is completed with an exercise which is to be
retllrned 10 the Il1lOr {or assessment.
or
For further
MID-C
CONSULTANCY
detail~
conta(\":
MID-C Consultancy,
39, Cleadon Lea,
Cleadon,
Tyne &. Wear. SR67rQ UK.
Fa..,,: +44 (0)191536 OR91
Email: peter~Vmid-c.demon.co.uk
UN·
ECE • DRAUGHT SURVEY CODE
"
DRAUGHT SURVEY REPORT OF CARGO IN BULK
FORM "A"'
RLOADED
UNLOADED
Corporate idenlilicahon:
Olficc ol lh€ surveyor al:
Telephone no:
Fax no:
Telex no:
Vessel M:V:
Call1cttors:
Survey no:
Vessel previous nameis:
Aegis1rv:
Buil! year:
By :
Flag:
Survey requested by:
On the account of:
Attend ed a Iso by:
as: njOint surveyor
DumPire nmonitoring
This is to certify that the undersigned did, in Bona Fide, attend on board the subject vessel as she lay afioat
at the port of:
for the purpose of determ ining by draught computations the
amount of
l and having followed the rules as set by the
loaded, unloaded (holds no.
U.N.I ECE Uniform Code of Standards and Procedures for the Performance of Draught Surveys have the
following to repo rt:
STARTING SURVEY
Attending the surveys: date:
hours: from:
Name of surveyorls
Master
Chief Officer
Chief Eng ineer
Witness draughls
Witness tank sounding
Ship's location
Weather temperature
Sea condition
Heading of ship
Direction wind
Stream speed Km Ih
Tide
tce
Car!)o h'Hldhng cqtipmenl T. tlfQugh!
Miss ing
Sh~)'S
cquil)m.!nt :
.~n
bo:ud:
FINISHING SURVEY
date:
to:
hours: tram:
to:
UN· ECE • DRAUGHT SURVEY CODE
R~OADED
DRAUGHT SURVEY REPORT OF CARGO IN BULK
FORM "B"
UNLOADED
Corpcfale idc,." ihcalion:
Vessel r..iN'
Survey!lO:
General remarks by the surveyorls
-
Correchon for stem and stern obtained by:
Correction for trim (1) obtained by:
Correction for trim (2) obtained by:
Correction due to trim tor liquid applied at:
-
Correction due to trim tor liquid obtained by:
_
calculation
calculation
r-
r-
tables
soundings
tables
r- tables
r- volumes
calculation
' - - tables
calculation
r-
Ship'S approved hydrostatic tables and lightship information issued by and dated:
Degree of tank calibration complies with code:
DYes
ONO
Ra nge or Him cOHcclion lables available :
Hull no.:
Shipyard 00 .:
Daledal :
Surveyor remarks on ship's documents:
metres
metric tonnes
Length overall
Constant declared
Length between p.p.
Constant calculated
Extreme breadth
Light displacem ent
Moulded breadth
Light shipweight (plan)
Depth overall incl. keel plate
Summer displacement
Moulded depth
Summer deadweight
Summer draught
Net register Ions
Summer freeboard
Gross register Tons
STARTING SURVEY
FINISHING SURVEY
Tonnes per Centimetre Immersion
Longitudinal Centre of Flotation
Distance marks forward pp. (forward - aft<-)
Distance marl<s after pp. (forward - aft+)
Distance marks mid ship pp. (forward - all+1
Moment 10 Trim One Centimetre +50
Moment to Trim One Cenlimetre ·50
Vessel list
Accessibility of sounding pipes
Working order of gauges
Legibility of draught marks
This torm should be fllted with pertinent shipyard-registry data by the Master in advance of survey start to
reduce time/inconvenience.
UN·
0 ECE • DRAUGHT SURVEY CODE
R~OADED
DRAUGHT SURVEY REPORT OF CARGO IN BULK
FORM "C"
UNLOADED
Corporate idenlilicatlOn:
VessclMN :
SUfVey r.c '
DRAUGHT STATEMENT
DRAUGHT READI NGS HOURS :
STARTING SURVEY
FINISHING SURVEY
FROM:
FROM :
TO:
TO:
metres
metres
K!l!m3
K9/ m3
Draught forward port
Draught forward starboard
Draught forward mean
Stem correction
Draught forward (corrected to fore .pp.)
Draught after port
Draught after starboard
Draught after mean
SI em correction
Draught after (corrected to after pp.)
Draught fore & after mean
Draught midship
port
Draught midship starboard
Draught midship mean
MidShip correction
Draught midship (corrected to midship pp.)
Sag (+) Hog
H
Mean of means
Draught extreme corrected for hog/sag
Correctio n (0) for keel tickness if applicable
Draught mo ulded corrected for hog/sag
(Note: Utilize line 152 or line 154)
fwd (-)
Trim:
aft (+)
Observed density
)
(Ship's tables density Kglm3
(Hydrometer no.
)
I
I
Metric tonnes
Displacement (al
I
Metric tonnes
Kg/m3 density)
First trim co rrectio n
Second trim correction
Tatal trim correction
Displacement corrected for trim
Correct ion fo r density ave rage
Displace men1 corrected for density
Total deduclibles
Displacement corrected for deduclibJes
Draughts, densities, fresh water and ballast soundings witnessed and agreed to by the Chief OHicer. Fuel oil
soundings witnessed and ag reed to by the Chief Engineer unless olherwise stated in form "A"
I
.
UN·
. ECE • DRAUGHT SURVEY CODE
R~OADED
DRAUGHT SURVEY REPORT OF CARGO IN BULK
FORM "01"
UNLOADED
Corporate identification:
V(!ssOIMN:
STARTING SOUNDING :
Compar1menl Title:
• Tank no.
• Bilges
• Duct keel
SUIVay no:
From Hours:
To Hours:
Date:
Trim:
Maximum
Sounding
Sounding
Volume
height
I ullage
I ullage
corrected
water
for trim 1 list
in air
Melric
m3
Kg/m3
tonnes
measured (-)
metres
corrected for
metres
trim II1S1
metres
A - BALLAST
Total A
B - FRESH WATER
Total B
n Stalemenl of obstructions in sounding tube/s:
Density of
Total
weight
UN·
ECE • DRAUGHT SURVEY CODE
"
R~OADED
DRAUGHT SURVEY REPORT OF CARGO IN BULK
FORM "02"
UNLOADED
Corporate identification:
Vessel MN:
FINISHING SOUNDING:
Compartment Title:
• Tank no.
" Bilges
"Duct keel
Survey no:
Fran Hours:
Dale:
To Hours:
Trim:
Maximum
Sounding
Sounding
Volume
height
I ullage
I ullage
corrected
measured (")
metres
correc1ed for
metres
trim I list
metres
A - BALLAST
Total A
B - FRESH WATER
Total B
(') Statement 01 obstructions in s~nding tube/s:
Density of
Total
water
weight
lor trim I list
in air
Metric
m3
Kglm3
tonnes
..
UN· ECE • DRAUGHT SURVEY CODE
R~OADED
DRAUGHT SURVEY REPORT OF CARGO IN BULK
FORM "03"
UNLOADED
Corporato identification:
Survey no:
Vessel MN:
SOUNDINGS
STARTING SURVEY
FINISHING SURVEY
Compartment
Title:
Total
Sounding
Actual
Actual
Weighl
Sounding
Actual
Actual
Tank no.
sounded
Ullage
Density
Volume
Metric
Ullage
Density
Volume
Metric
Slop 1.
depth m.
metres
Kg /m3
m3
Tonnes
metres
Kglm3
m3
Tonnes
C - FUEL OIL
Total C
D - DIESEL OIL
Total D
SUMMARY OF DEDUCTIBLES
STARTING SURVEY
FINISHING SURVEY
metric tonnes
metric tonnes
Baliast water
Fresh water
Fuel oil
Diesel oil
Slops
Lubrificaling oil
Swimming pool water
Anchor & Chain
Others
Total Deductiblesl
I I
I
Weight
UN· ECE • DRAUGHT SURVEY CODE
·
R~OADED
DRAUGHT SURVEY REPORT OF CARGO IN BULK
FORM "E"
UNLOADED
Cor,l::orale idenlification:
Vessel MN :
Survey no:
CARGO STATEMENT
Metric Tonnes
Starting Displacement Corrected
Finishing Displacement Corrected
Difference in Displacement; TOTAL CARGO IN BULK IS:
OBSERVATIONS: Shore scale quantity (if available) M.T.
I
I
Note on any unusual situation/s, exception/s from required Uniform Code standard , specific identification
(source, drawing no., date, title , certifying authority) of each ship's document used in translating recorded
measurements Into weights and, when applicable, reasons for surveyor's refusal or Impossibility to perform
the survey:
Metric Tonnes
Corrected light disptacement ;
DeductablesLightship;
Constant-
Mean of previous constants=
I certify that the constant calculated from this draught survey has been entered into the ship's ·Constant Certificate·
In my judgement the weather conditions, the sea condillons , and the conditions of the ship at the times the
draught surveys were conducted, were within acceptable limits and did not adversely affect the accuracy of
__ pages, including this page, all duty inltlalied or signed
this survey. This Bona Fide report consisting of
is issued without prejudice and is for the benefit of whom it may concem.
(corporate identification)
Name of surveying firm
By:
(Signature ot Surveyor's)
Name(s in print
I have participated in all stages of this draught survey, and agree with the results obtained. I acknowledge receipt at the ship's copy.
Signed :
Rank:
Name In print