Liguefied Gas Tanker Operation Notes

8/16/2019 Liguefied Gas Tanker Operation Notes

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GAS TANKER OPERATION

Sequence of Cargo Operation On Board Liquefied Gas Tanker.

1 Drying Tanks.

2 Inerting Cargo Tanks / Cargo Syste.

! Loading Deck Tank

! Gassing "p

# Coo$ing Do%n Cargo Tanks.

& Inerting 'o$d space

( )repairing Tanks for Loading.

* Loading

+ Loaded ,oyage- "n$oading Of Cargo

-.1 "n$oading %it Deep%e$$ )up at Cargo Tep.

-.2 "n$oading %it Deep%e$$ )up t Terina$ required Tep

-.! Booster )up Discarge

10 Ba$$ast ,oyage

11 Canging Of Cargo

12 )reparation for dry Dock.


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1. Lining "pTe Cargo Tanks to e gas freed are connected to te for%ard ent stacks if possi$e.

1.1 Connecting te Inert Gas Line

2. ,enting off ,apour

In port

3n routeto a$ter te course steered if te re$atie %ind direction is unfaoura$e4 at ancor

to eae up te ancor and stea to find ost faoura$e re$atie %ind direction.

!. 5ecircu$ating ir6conditioningTe air6conditioning p$ant sou$d e canged to recircu$ating during te initia$ ours of enting off apour.

#. ,enting aonia using f$e7i$e oses

s a eans to preent dangerous reactions te fo$$o%ing precautions sou$d e osered.

Te Inert Gas Line sa$$ on$y e connected to te Cargo Tanks %en te tanks are ready for inerting and te InertGas )$ant is ready to produce inert gas of te requested qua$ity.

Te tie for connecting and disconnecting te Inert Gas Line to te Cargo Tanks sa$$ e noted in te esse$8sofficia$ $og ook.

Te gas concentration in te cargo tanks is igest during te initia$ ours of enting off and %i$$ gradua$$ydecrease as te atospere in te cargo tanks is di$uted y inert gas 9or air if c$eaning after aonia.:

To ensure tat te apour ented off during te initia$ ours is not drifting to%ards te accoodation and airintakes to te engine roo it ay e necessary;

Terina$ or port regu$ations regarding enting or purging of cargo apour ust e osered. Suc regu$ationsay require tat ented cargo apours sou$d e $ed to a f$are4 or ent stack or for use in te sore p$ant.

If te cargo apour is not $ed asore adance notification sou$d e gien to te port autorities and perissionotained efore starting te operation.

If it is required to reduce te nitrogen pressure of a cargo tank containing cargo suc nitrogen sou$d e regardedas cargo apour and port regu$ations regarding enting cargo apour ust e osered.

If apour in arfu$ concentrations cannot e aoided at te accoodation and engine roo air intakes4 it ay e necessary to postpone te tank c$eaning in %ic case te )rofit Centre sa$$ e adised iediate$y.

)ersonne$ %orking in te engine roo sa$$ e infored %en enting off apour is coenced. s te airintakes to te engine roo cannot e cop$ete$y c$osed during tank c$eaning4 te engineers %i$$ often e te firstto notice any detecta$e gas.

onia %i$$ %en in contact %it %ater generate a intense eat %ic is a$e to e$t te ose and ignite anyreains of preious cargoes c$inging to te inside of te oses. Tis as een e7perienced in a gas carrier %enenting after te carriage of aonia. Te generated eat e$ted te ose connected to te anifo$diediate$y after opening te anifo$d a$e and ignited te po$yerised utadiene residues.


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Before eing used te oses sou$d e cecked for c$ean$iness fro reains of oter cargoes fro preious tankc$eaning operations. It ay e necessary to p$ace te oses on deck and $eae te e7panded for a fe% ours inorder to a$$o% te oses to attain aient teperature and to ensure te oses are dry.

fter eing used te oses sou$d e c$eaned. )rior eing co$$apsed and stored te oses sou$d e $eft on tedeck in e7panded condition for soe tie in order to ena$ing te to e toroug$y dry.


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1. DRYING TANKSTe Tanks of Liquefied Gas Tanker out of Sipyard 9 o$$o%ing Sou$d e done prior c$osing Do%n Tanks.

1 Inspection of Tanks ust e carried out.

2 C$ean tanks. Dry any %et surface in tanks.

! ny Loose o?ect sou$d e reoed and a$$ fitting ust e proper$y secured.

# Trun )up y and and Ceck Loca$$y for any un%anted sound / noise. Ceck tat )up turns easi$y.

& Ceck a$$ spray no@@$es are free.

( Ceck tat te Sap$ing points are C$ear.

* Drain out a$$ ,ent asts.

+ Operate Bu$kead a$e and ark proper$y for Open / Sut )osition.

-


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To


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Inerting o# Air $ille% &ol% / Tanks / Cargo System 'it( Inert Gas.

Inerting Cargo Tanks.

or Inerting Tanks ; Disp$aceent of ir tospere By Inert Gas. In Series.

1 Inerting tanks.

2 Inerting Deck tank Std.

! Inerting Liquid Line.

# Inerting ,apour Line.

& Inerting Condensate Line.

( Inerting Booster )up Line.

* Inerting 5e$iquification units / Lines in copressor roos.

Te air atospere is canged %it Inert gast to reduce O7ygen. Te Concentration of 2 O7ygen or e$o%

is sufficient in Cargo tanks.

IGG Ca"aity )

De' Point )

S!""ly O*ygen Contant ) +., -

Cecks to e done prior Starting Of Inert gas On Deck.

1 Ca$irate O7ygen i$$ing Side: nd te Out Let fro te Tank is Connected ack to IG Line.

! Ceck $$ sa$ing points are C$ear.

# I.G. O7ygen eter is Ca$irated and recorded.

& Line up for te >or%ard ,ent ast.( Drain out any %ater fro ,ent asts.

* Inspect te ,ent ast >$ae arrestor screen is c$ean.

+ Operate a$$ a$es on te cargo syste. $$ to e %orking satisfactory.

- $$ anifo$ds are B$anked 9Liquid and ,apour: . 5eoe $ank of Cargo anifo$d drain a$es and eep te

dain a$aes sut.

10


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Eo ! Tk Capacity ; 11(!+

Eo 2 Tk Capacity; 1&&!(

Eo 1 Tk Capacity; 11&2+

Deck Tk 9): Capacity ; 1#(

Deck Tk 9S: Capacity ; 2-!

Tota$ Cuic capacity

of tanks for Inerting. !-1#1

!!.& 'rs

2.& 'rs

Inerting to e carried out in series. s so%n in Line "p diagra.

eep cecking O7ygen reading for eac tanks eery our.

In series Inerting4 Eo. ! Tank %i$$ e Inerted >irst. Once te Tank O2 reading at ! different $ee$s is 2 or

e$o%4 Eo ! Tank is Inerted.

5ine 6" Diagram Atta(e%.

Open te IG Line Iso$ation / at Eo! F sut te anua$ ent / at Eo ! tank doe.4 $so sut te Eo !

as slo'ly as "ossi3le so as not to im"e%e t(e "iston e##et / strati#iation in tanks.

5ine 6" Diagram Atta(e%.

On cop$etion of Inerting of Eo 2 tank co8d Inerting Deck tank 1 F 2 in para$$e$ %it Eo 1 cargo tank Te $ine up diagra is attaced. On cop$etion of Inerting of Cargo and deck tanks4 Line up for inerting

Cargo pipe $ine syste.

5ine !" Diagram #or Inerting Pi"elines on argo system is atta(e%.

Inerting 5i7!i% 5ine.

Inerting 8a"o!r 5ines 9 Connet R!33er (ose at 8a"o!r (ea%er / 5i7!i% (ea%er 9At 5i7!i% mani#ol%

Connet 10:;ooster P!m"4 Cargo (eater/8a"oriser.

Inerting Reli7!i#iation Plant.

5ine !" %iagram is atta(e%.

Eote on 'o% to Do

Open "p Liquid Line aster / at Eo ! Tank doe4 Liquid eader Eo 1FEo2 at Eo ! Tk. Open Liquid

anifo$d a$e port 9ot


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See Atta(e% 5ine !" Diagram.

Inerting of 5e$iquefication units and associated cargo )iping.

Eote tat efore starting Inerting of re$iquefication units and associated cargo pipe $ines a$$ tanks are

cop$ete$y Inerted.

See atta(e% %iagram.

Te 5e$iquefication syste can e Inerted y Eitrogen a$so Te Line up diagra is attaced. Tis %ay

inerting of Cargo tks / )ipe $ine and 5e$iquefied syste can e done siu$taneous$y.

>or Inerting copressor Eo !.

,112 666H ,5 !02666H B>2&01 666H 1st Satge 666H Intercoo$er 666H 2nd Stage 666H B>2&0& 666H !rd stage 666H

B>2&0# 666H B>2&11 666H '5!01 666H '5!01 666H 002 666HEO2,5/B>2&0# 666H COED3ESO5 666H 5C,5

B2&12 666H B2&1& 666H B2&1( 666H 3) ,/, 666H C5!01 666H C001 666HL00# 666H 2,5

C5!02 ia C002 666H L(22 666H L(!2 666H L(!1 666HL00# 666H ,3ET


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Instr!tions #or 5oa%ing Coolant

>u$$y refrigerated L)G8s are equipped %it t%o deck tanks for $oading and/or storing purge parce$s.

Tis akes it possi$e to aoid ca$$ing at an additiona$ port for $oading a purge parce$ .

te aonia trade4 te tank ay e used for storing additiona$ L)G for coo$ing purposes.

Pre"arationsBefore purging is coenced a nuer of conditions ae to e taken into consideration4 suc as;

Euer of tanks to e $oaded %it te product in question.

3stiated product $oss.

Do te deck tanks contain sufficient product to accop$is requireents.

P!rging 'it( 5PG

a= P!rge Parel

In order tat tere is sufficient product to perfor a fu$$ conditioning of te cargo tanks4 as uc cargo as

possi$e sou$d e transferred to te deck tank9s: during nora$ operation in te L)G trade 9%en

canging grades etc.:. If possi$e te $arge deck tank sou$d a$%ays contain )ropane.

3= 5oa%ing P!rge Parel

If te deck tank9s: does not contain sufficient product to perfor a fu$$ purging of te cargo tanks4

additiona$ product sa$$ e $oaded eiter in te deck tank9s: or in a cargo tank if a$ready conditioned.

= P!rging

See attaced Line "p Diagra

%= Trans#erring 5i7!i% to t(e 8a"oriser

Deck tank pup sou$d e used to transfer te $iquid if te deck tank pressure is e$o% * ar.

e= 8a"oriser

Starting procedure for te aporiser is descried in te L)G operation anua$.

#= $lo' Diretion o# 8a"o!r

Te cargo tanks sa$$ e purged in para$$e$ as tis %i$$ iniise te f$o% troug eac cargo tank and tus

increase te stai$ity of te stratification. Te additiona$ product used for purging in para$$e$ copared to

purging in series is argina$.

,apour is directed fro te aporiser to te cargo tanks troug te $iquid fi$$ing $ine.

Eitrogen or inert gas is reoed fro te cargo tanks troug te apour $ines %ic sa$$ e connected

to te ent stacks %it e$o%s.

g= Press!re

In order to aintain te est possi$e stratification te cargo tank pressure sa$$ e kept to a iniu.

(= ?onitoring an% Reor%ing

It is essentia$ to onitor te progress c$ose$y during te entire purging operation %it regu$ar

easureents taken to ensure unifor distriution of apour in a$$ tanks.

>ro tese easureents4 graps sa$$ e dra%n. Te graps %i$$ c$ear$y indicate te progress of te

purging4 terey ena$ing ear$y interention4 sou$d te purging not proceed as p$anned. >urterore4

tese graps %i$$ indicate4 at %ic tie te purging can e7pect to e cop$eted.

i= Starting Com"ressors

Before starting te copressors4 it is good practice to continue te purging for 1& inutes after 100 .

reading is reaced

Te $arger deck tank of !00 ! is nora$$y used for storing L)G.

Te sa$$er deck tank of 1&0 ! is nora$$y used for storing aonia4 o%eer4 if esse$ is not $ike$y to e in


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@= >lo' o##

Sou$d te atospere in te cargo tanks not e 100 pure gas4 te inert gas/nitrogen ay e ented off

ia te condensers unti$ te top of te cargo tank is 100 gas.

k= Cooling

On cop$etion of purging4 te $iquid reaining sou$d e transferred to te $iquid $ine. It is ten used to

coo$ te cargo tanks ia te upper spray $ine.

l= Press!re

If te tank pressure fa$$s too quick$y during coo$ing tere ay e insufficient pressure to cop$ete te

operation. )roided tere is sufficient $iquid in te cargo tanks and te pressure is not aoe 0.2& ar4 te

cargo pups sou$d ten e started and $iquid circu$ated troug te upper spray $ine.

m= Tem"erat!re

Te cange in teperature sa$$ a$%ays e %itin te recoended $iits. Tis %i$$ e cop$ied %it y

unifor$y coo$ing te tank troug te upper spray $ine.


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2. P!rging 'it( ammoniaa= P!rge Parel

If te purge parce$ is $oaded in one of te cargo tanks4 ten te cargo tank sa$$ a$%ays e purged to 100

aonia prior to starting $oading $iquid.

3= P!rging

onia reacts %it arious coponents in te inert gas foring sa$ine products. It is terefore not

a$$o%ed to purge %it aonia in tanks containing inert gas.

Due to aonia8s narro% range of f$aai$ity and ig ignition teperature it does not genera$$y

constitute a fire a@ard. Terefore it is considered safe to purge aonia into tanks containing fres air.

'o%eer4 soe terina$s do require tat te cargo tanks are inerted to a $o% o7ygen $ee$ efore $oading.

Inerting sa$$ in tese circustances e conducted %it nitrogen.

= Trans#erring li7!i% to t(e 8a"oriser.

s te sa$$ deck tank does not ae a transfer pup4 any cargo sto%ed in tis tank sou$d e as %ar as

possi$e. Cargo sou$d ten e transferred to te cargo tank ia te aporiser to preent any fu$$y

refrigerated product entering te tank.

d: ,aporiser.

)$ease refer to section 2.2.2.

e= $lo' Diretion o# 8a"o!r

Te apour is directed fro te aporiser into te cargo tanks ia te apour $ine and te upper spray $ine.

Te anua$ a$e et%een te $iquid $ine and te condensate $ine sa$$ e c$osed and prior to initiating

purging it sa$$ e ensured tat tis a$e is c$osed secure$y.

ir or nitrogen is disp$aced fro te tanks troug te $iquid fi$$ing $ine4 %ic sa$$ e connected to te

ent stacks %it e$o%s.

#= ?onitoring an% Reor%ing

)$ease a$so refer to section 2.2.&.

=en purging %it aonia4 arrett6testers are used to easure te aonia concentration. Tese testers

use fres %ater and do not require te use of any specia$ ceica$s.

g= Stress Corrosion Craks

Tere is a possii$ity on te fu$$y ref. esse$s of stress corrosion cracks %en carrying aonia is present.

ccording to e7perience stress corrosion cracking ay occur in cargo tanks containing aonia4

depending on type and treatent of stee$.

To iniise te risk of stress corrosion cracking4 te fo$$o%ing guide$ines issued y SIGTTO sa$$

e fo$$o%ed;

(= Tem"erat!re

i= ater ontent.

=ater %i$$ act as an iniitor against stress corrosion and it is recoended y sore insta$$ations tat teaonia sou$d contain a iniu 0.2 y %eigt of %ater.

Te carriage teperature sa$$ e kept e$o% 6!0oC.


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@= O*ygen ontent.

onia does not cause stress corrosion cracking un$ess it is containated y o7ygen. =en

anufactured aonia as an e7tree$y $o% o7ygen content4 $ess tan 1 pp y %eigt.

During coo$ do%n an o7ygen content of 0.& y o$ue is genera$$y considered safe.

'o%eer4 te o7ygen content sou$d e $ess tan 0.02& y o$ue prior to introducing $iquid to te cargo

tanks.

k= Starting Com"ressors

s easureents are not a$%ays aso$ute$y accurate4 it is a good practice to continue te purging for 1& to

!0 inutes after 100 aonia concentration in te otto of te cargo tanks as een easured efore

starting te copressors.

l= >lo'o##

During te first fe% days of operation of te re$iquefaction p$ant4 te incondensi$e gases %ic accuu$ate

in te condensers4 i.e. te air reaining in te cargo tanks4 sa$$ e ented off.

m= Cooling)$ease refer to section 2.!.

0. Cal!lation o# t(e Time Re7!ire% #or Preooling

Te stee$ ass of te cargo tanks on a !&4000 J fu$$y ref. gas carrier is estiated to e 24(-+ etric tons.

Te stee$ as to e coo$ed fro 2&KC to 6 #0KC. Te cargo tanks are purged %it (0 t of propane apour

at 2&KC.

Te fo$$o%ing quantity of eat ust e sustracted;

>ro te stee$ ass;

24(-+4000 kg 7 0.12 7 92& #0: 2140##4#00 ca$ 9%ere 0.12 is te specific eat of te stee$:.

>ro te propane apour; 1004000 7 91-&.- 6 1*+.-: 14*004000 ca$ 1-&.- and 1*+.- are te enta$py of te

propane apour at 2&KC and 6 #0KC.

Tota$ capacity of re$iquefaction p$ant; 140!&4000 ca$.

Tie required; aout 22 ours.

Te aoe ca$cu$ation does not take into consideration te eat f$o% troug te tanks and sou$d e

regarded as guidance


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>e#ore 5oa%ing or Dis(arging

>e#ore loa%ing or %is(arging is ommene% t(e #ollo'ing ations s(all 3e taken)

2. 3ergency to% off %ires sa$$ e rigged and e ready for use on ot te poop and te forecast$e.

!. >ire figting equipent sa$$ e in order and e ready for use.

-. ny notices fro sore aout safety requireents sa$$ e posted.

12. Te a$es on deck sa$$ e set according to te pre6p$anned $oading or discarging procedure.

If te cargo eat e7canger is to e used during $oading or discarging4 it sou$d e pressure tested %e$$ inadance of arria$.

Te pressure test is conducted y fi$$ing te eat e7canger8s sea %ater section %it fres%ater and tence

pressurising it y eans of a and pup to aout & ars oerpressure.If te eat e7canger is capa$e of aintaining tis oer pressure for aout t%o ours %itout a noticea$e dropregistered on te pressure gauge4 it can e considered tigt.

If tis is not te case4 it ust e opened up and te $eaking pipes identified and sea$ed off. ne% pressure testust ten e perfored.

1. Te MSip/Sore Ceck ListM sa$$ a$%ays e cop$eted in co6operation %it a representatie fro te soreinsta$$ation. If te sore does not present a ceck $ist for cop$etion4 te . ).


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D!ring 5oa%ing an% Dis(arging)Trougout $oading and discarging te fo$$o%ing instructions sa$$ app$y;

!. To ensure free operation of te u$kead a$es a$$ a$es sa$$ e oed prior to $oading.

Te a$es sa$$ a$so e oed frequent$y during $oading.

fter cop$etion of $oading te u$kead a$es sa$$ e c$osed4 and reain c$osed during te oyage.

If any a$es do not oe free$y tis is to e reported iediate$y.

Detai$s of te oeent of te a$es sa$$ e recorded in te Deck Logook.

Te cargo and$ing p$an sou$d inc$ude ut not $iited to te fo$$o%ing inforation;

. . Ba$$ast inforation.

G. ccess to te sip and soking restrictions.

'. diagra so%ing te $ining up of te cargo $ines in use.

1!. 5e$ief a$es for te cargo tanks sa$$ e ad?usted to te correct $ifting pressure efore $oading iscoenced. Te pneuatic a$es at te anifo$ds ust not e operated fro te cargo contro$ roo efore teoses are connected and te $oading or discarging are to coence.

1#. =en oses are connected and notice of readiness is gien to or receied fro sore4 $oading or discargingay coence. Loading sa$$ egin at a $o% rate4 and te $oading rate ay on$y e increased %en it is positie$y erified tat $iquid is entering te cargo tanks as p$anned4 and te cargo pipes are not $eaking.Discarging sa$$ egin %it a s$o% puping rate and te pup pressure gauges sa$$ e constant$y onitored.

1&. )acking g$ands at te discarge a$e sa$$ a$%ays e kept tigt and te doe sa$$ not e $eft unattendedunti$ g$ands are ensured tigt %itout any $eakage to te atospere.

1. Te %atckeeping officer8s station is on deck or in te deck6office4 and it is is duty to ensure tat te pups

and ose coup$ings are kept under oseration.

2. Soundings4 tank pressures and teperatures4 and anifo$d pressure and teperatures4 sa$$ e cecked atfrequent intera$s.

#. Te sip8s oorings sa$$ e cecked at regu$ar intera$s to ensure tat tey do not ecoe too tigt or toos$ack.

&. )ersons not assigned duties regarding cargo operation4 %atc keeping4 or oter tasks on deck sa$$ e refusedaccess to te tank deck.

(. Leakage8s fro f$anges4 g$ands and coup$ings sa$$ e stopped iediate$y. If $eakage8s are too $arge to eand$ed iediate$y4 te cargo operation sa$$ e stopped and te syste de6pressurised.

Te Cief Officer sa$$ not $eae te deck/deck6office unti$ e as anded oer %ritten instructions aout tecargo operation arrangeents inc$uding a$$ast to te Officer of te =atc 9OO=:4 and as satisfied ise$f tatte OO= as understood te instructions.

I. ny oter inforation %ic sou$d e aai$a2$e to te OO= in order to ensure a soot and safe cargooperation.

If on$y a part cargo as een $oaded or discarged4 soundings4 pressures and teperatures sa$$ again eeasured under te superision of te cief officer and te receier8s representatie in a$$ te sip8s tanks4

inc$uding te tanks fro %ic no cargo as een $oaded or discarged in te


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1. 8a"orising li7!i% (eelCopressors %it apour $o%ers are used to eat up te reaining $iquid 9%ic ten eaporates:4 te

aonia apours4 and tank stee$. It is ery iportant to distriute eat een$y trougout te tank

a$toug te pup sup sou$d e eated coparatie$y ore. Te pup sup sou$d genera$$y e

eated for an additiona$ 1 to 2 ours4 after a$$ $iquid as een aporised4 in order to preent recondensing

of apour against co$d stee$.

2. S!3oolingIt is an inaria$e ru$e tat tanks 6 inc$uding tank stee$ 6 are eated to a teperature aoe de%point of te

air used for enti$ating. Teoretica$$y4 it sou$d e sufficient to eat to a teperature of e.g. 62&KC %en

enti$ating %it te IG6$o%er4 as tis supp$ies air %it a de%point of aout 6#&KC.

'o%eer4 tis does not app$y in practise as oter conditions ae to e considered.

It sou$d e a genera$ ru$e to eat te tanks to not $ess tan 20KC4 and specia$ care sou$d e taken to

ensure tat te pup sup is eated toroug$y.

. Remoal o# oer"ress!re

0. 8entilating

,. 8enting o## ammonia 'it( IG3lo'er

It ay a$so e necessary to ad?ust te course so tat apour c$ears te accoodation.

If %arer and especia$$y ore uid air is added to te tanks8 atospere4 tis air %i$$ asor te aoniaapour aking te aonia $iquid4 try to fi$$ te tank space %it apour y eaporation. Te eat required fortis process is taken fro te nearest surroundings4 e.g. te tank stee$4 and a drastic drop in teperature can e

osered. Teperatures far e$o% te stee$8s design teperature and a rate of decrease u$tip$e e7ceeding tat%ic te tanks are designed for can e osered and terey possi$y daage te tanks. Te uidity in te air%i$$ a$so re$iquify against te stee$4 te %ater %i$$ disso$e te aonia and sustantia$ pro$ongation of teduration of te tank c$eaning ust e faced4 as tis aonia and %ater so$ution is ery difficu$t to reoe.

In order to e a$e to eat up te tanks to required teperatures4 te esse$s ae een furnised %it 2 DeckB$o%er units %it a tota$ of 2 7 22000 ! capacity4 %it stea eating of te air. "sing tese $o%ers it is possi$e to eat up te tanks to at $east #0KC. t tis teperature it is not difficu$t to $o%er te aoniaconcentration.

Oerpressure is reoed gradua$$y fro te tanks troug te ent asts in te usua$ %ay c$ose$y onitoring teteroeters.

=it aonia it is a specia$ requireent not to use inert gas for di$uting te gas as certain coponents in teinert gas react %it aonia to for sa$ine products %ic $ock up a$es4 pipes etc.

s aonia8s e7p$osion $iits are fro 1( to 2& percent and it is difficu$t to ignite and a$so %it a $o% ca$orifica$ue4 it can under nora$ circustances e regarded as non f$aa$e. Tus4 tanks can e enti$ated %itoutfirst eing inerted.

Te porta$e $o%ers are not a$e to %ork against ack pressure of any significant si@e. It is terefore necessaryto enti$ate aonia y using te inert gas $o%er %i$e te concentration is sti$$ too ig for it to e ented offtroug open tank atces4 i.e. %i$e te concentration of aonia is too ig for personne$ contact. ir frote inert gas $o%er is supp$ied to te tanks troug $iquid $ines oer te anifo$d to te tanks8 $iquid fi$$ing$ines. By reason of aonia8s apour density copared to tat of air4 tanks sou$d e connected in para$$e$.Tanks are ented off at te top4 and te ented off apour is $ed to te for%ard gas ast in order to iniiseinconeniences fro te aonia.

Te process of di$ution can e onitored c$ose$y using Barrett testers. ery c$ear stratification can e e7pected."sua$$y one cange of atospere can e e7pected to e sufficient to ring te concentration e$o% easura$e$iits using Barrett6testers.

,enti$ating using te inert gas $o%er ust e continued for appro7iate$y anoter 1& ours as te porta$e $o%ers cannot %ork against ack pressure.


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B. 6sing (ot air 3lo'ers

t a concentration of aout *00 pp4 2 ot air $o%ers can e put to %ork.

. $inal entilation

12. Drying tanks

During tis pase4 Drger test tues can e used to indicate4 %en te porta$e ot air $o%ers sou$d e rougtinto use. t a reading of &006*00 pp4 te concentration %i$$ no $onger dec$ine gradua$$y ut instead rise andfa$$. Tis is an indication tat te tank stee$ is eginning to free trapped aonia.

It is necessary to open te tank atces to ake it possi$e for te ot air $o%ers to supp$y air at a ratesustantia$$y iger tan tat of te Inert gas $o%er.

To iniise te ack pressure4 it is necessary to open te atces y reoing a$$ ut 2 o$ts4 %ic are on$y$oosened. By squee@ing one o$t under te atc coers4 sufficient c$earance is otained to aoid too ig a ack pressure. t a concentration of aout *00 pp4 %ork can e carried out on te atces %itout any inconenienceand %itout using gas asks.

Te $o%ers are started and stea eating app$ied. arked increase in efficiency can e seen after initiating teot air $o%ers. fter appro7iate$y & ours4 te concentration %i$$ ae een reduced enoug to ake it possi$e to reoe te atces and rig oses in te tanks.

noter 2062# ours8 enti$ation %i$$ e required. fter tis4 concentration can e e7pected to e %e$$ e$o% & pp.

Tus4 an aonia concentration %ic is detecta$e ut uneasura$e4 can e acieed y enti$ating %it otair.

=en ot air enti$ation as een cop$eted4 te tanks ust ten e dried toroug$y %ic is done y using teinert gas $o%er. ,enti$ation is continued unti$ te required de%point as een reaced. It is not anticipated tatte aonia concentration %i$$ increase again.


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5oa%ing O# Coolant in No 1 Tank

1 P!rging No 1 Cargo Tank.

2 5oa% In Cargo Tank No 1

Loading 2&0o$$o%ing is to e prepared prior )urging / Loading of Coo$ant.

1 Ceck O7ygen reading for Eo 1 Tank. It sou$d e 2 o7ygen or e$o%.

2 )ressuri@e te Tank %it IG and ceck no $eaks on tank doe.

! 5e$ease te IG pressure troug ,ent ast Eo 1.

# Cargo sea%ater pup to e running sea%ater f$o%ing troug cargo eater / aporiser.

& Ca$irate fi7ed gas detectot syste.

( Ca$irate Gas easuring porta$e equipent.

* 'ydrau$ic p/p 4 anti$ation fan for copressor r 4 3$ otor r air $ock antia$tion fans running.

+ /C on partia$ recircu$ation. ire figting equipant stand y at anifo$d4 in ready to use state.10 Te


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,112 /,111 666H ,5101/,5102 666H B>2&01 666H 1ST STG3 666H IET35COOL35S 666H2ED STG3

!rd stage 666H B>2&0# 666H B>2&11 666H'5102 666H '5102666H'5101666H'00!666H ,00& 9 ,apour return:

Pls see 5ine 6" Diagram

Cooling %o'n 'it( a"o!r ret!rn to s(ore.

=en te gassing up procedure is cop$eted4 coo$ do%n of Eo 1 Cargo tank c$d e started prior to Loading

cargo into te tank.

Coence $oading $iquid $ine at a s$o% rate into Eo 1 cargo tk. Initia$$y to $oad troug condensate return

$ine into te top spray no@@$es. On coenceent of te coo$ing do%n operation te tank pressure s$d e

as $o% as possi$e.

s $ong as te teperature of te tank atospere is igter ten te saturated tep of te propane In?ect

troug te spray no@@$es4 Te tank atospere teperature and cosequent$y te stee$ teperature %i$$

decrease.

3aporation of te Liquid to $o%er tep %i$$ cange te cargo apour ,o$ F )ressure. t te eginning of

spraying4 te apour o$ue %i$$ decrease due to reduced tep and te pressure in te tank %i$$ reduce.

fter a %i$e te added spray quantity %i$$ e doinant and te tanks pressure %i$$ start to increase.

Due to te eaiour of te process4 te tanks pressure s$d e onitored carefu$$y.Once te tank tep as reaced to 62& Deg C coence introducing $iquid into te otto sup tru te

codensate otto $ine.

=en te sup is fu$$ of $iquid coence $oading y te ain Liquid $ine into te tank. Loading rate to e

Increased gradua$$y.


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P!rging / Gassing 6"

>o$$o%ing to e cecked

1 Ceck 'C reading for eac tank / at eac sap$ing point.

2 Connect f$e7i$e oses on tank doe to ent to respectie tank ent ast Line.

!


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COO5ING TANKS

Once te reading so%s 100 'C. Continue gassing up for at $east 10 !tane )T%o Stage copression %itout Intercoo$er.

!antity o# &eat to 3e remoe% #rom tanks

Te stee$ ass of te cargo tanks on a !&4000 J fu$$y ref. gas carrier is estiated to e 24(-+ etric tons.

Te stee$ as to e coo$ed fro 2&KC to 6 #0KC. Te cargo tanks are purged %it (0 t of propane apour

at 2&KC.

Te fo$$o%ing quantity of eat ust e sustracted;

>ro te stee$ ass;

24(-+4000 kg 7 0.12 7 92& #0: 2140##4#00 ca$ 9%ere 0.12 is te specific eat of te stee$:.

>ro te propane apour; 1004000 7 91-&.- 6 1*+.-: 14*004000 ca$ 1-&.- and 1*+.- are te enta$py of te

propane apour at 2&KC and 6 #0KC.

Tota$ capacity of re$iquefaction p$ant; 140!&4000 ca$. < Q 9 1610:

Tie required; aout 22 ours.

Te aoe ca$cu$ation does not take into consideration te eat f$o% troug te tanks and sou$d e

regarded as guidance

T(e Cargo (an%ling man!al gies gra"( #rom '(ere t(e Time taken #or ooling an 3e al!late% straig(t

$or N&

T%o stage copression %it Intercoo$ing 9 S= Tep R 20 O C :

Tree stage copression %it Intercoo$ing 9 S= Tep H 20 O C :


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C(anging Cargo #rom Pro"ane to >!tane

If ne7t cargo is Butane after )ropane4 ten te cargo tank conditioning is to e done.

1 t te Discarge port as far as possi$e strip out a7iu cargo.

2 Te tank is to ade $iquid free.

Start copressors on ot gas ode and start putting ot gas in Sup of te tanks. It Liquid in sup %i$$

get eaporated and If %e ae tie One copressor can e run to take apour fro te tank and re6$iquify

and dup te $iquid into te Deck tank %it )ropane. =ic can e used in future for coo$ing tanks for

prepairing for )ropane fro Butane.

If deck tank is fu$$ or tie is $iited. Te propane apour is to e re$ised to atospere.

Te Tank is ot gassed and te ,apour fored due to eaporation od Liquid %i$$ pressurise te tanks.

Te pressure can e re$ised to atospere fro ent asts.

=en te pressure is re$ised te Tank %i$$ coo$ do%n. It is good practice to re$ease tank pressure in contro$

%ay. $%ays ake sure tat te Tank pressure is igt ten te tosperic pressure. So no ack f$o% of

air can take p$ace in any case.

! Once te Sup teperature is aout 6+ to 610 Deg C te 'ot gassing can e stopped. nd tank isConditioned to Load Butane.

3nta$py of )ropane at 6#0 dec C #00 /g

3nta$py of )ropane at 610 Deg C +00 /g

Cange in 3nta$py #00 /g

)ropane in Tank !0


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Density of Gas at 20 deg C and Atm Pressure

Air 1.024

Ammonia 0.714

Butane 2.484

Propane 1.866

Loer !"p#osi$e Limit

Butane 1.%0&

Propane 2.00&

Ammonia 1%&

Documents

Liguefied Gas Tanker Operation Notes