Fuel Quality Control on MT ILMA and Cap Felix

8/18/2019 Fuel Quality Control on MT ILMA and Cap Felix

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International Maritime University of Panama

Nautical Science Faculty

Nautical Engineering Degree with Specialization in Naval Machinery.

Marine Fuel Quality Control on M! I"M# an$ %ap Feli&

Presente$ 'y(

%arlos Enri)ue Samu$io Martinez

*+,-+/0-1

March2 34/1


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DEDI%#!I5N

I dedicate this sea project to my mother for encouraging me to achieve my goals

and for giving me all her support to accomplish this important project.

I also dedicate this project to God for giving me the necessary strength that has led

me where I am today.

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#%6N57"ED8MEN!

I am indebted with my Professors, classmates, and fellow seamen that helped and

guided me with their experience and knowledge.

y sincere thanks also goes to !"#$%&' and to all of those who contributed with

willingness in the development and completion of this project by their knowledge

and experiences.

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!#9"E 5F %5N!EN!S

Page

P:ESEN!#!I5N........................................................................................................I

DEDI%#!I5N.............................................................................................................II

#%6N57"ED8MEN!S...........................................................................................III

!#9"E 5F %5N!EN!S...........................................................................................I;

!#9"E 5F I""US!:#!I5NS..................................................................................I<

!#9"E 5F %=#:!S.................................................................................................<

E..........................................................................................PES............................................................................................1

2.2.1 Marine Gas Oil (MGO)...........................................................................7

2.2.2 Marine Distillate Oil (MDO)....................................................................8

2.2.3 Intermediate !el Oil (IO)....................................................................8

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2.2." #eav$ !el Oil (#O)............................................................................8

3.@ :E8U"#!I5NS #ND S!#ND#:S.........................................................................../4

2.3.1 ISO 8217..............................................................................................1%

2.3.2 M&'O..............................................................................................1%

2.3.3 ISM.......................................................................................................1%

3.* FUE" 5I" P:5PE:!IES .....................................................................................//

2.".1 *al+rific val!e......................................................................................11

2.".2 ,isc+sit$...............................................................................................11

2.".3 *etane n!mber....................................................................................12

2."." *alc!lated carb+n ar+maticit$ inde- (**&I)...................................12

2.". *+nrads+n carb+n val!e.....................................................................13

2."./ &s0 c+ntent..........................................................................................13

2.".7 S!lp0!r c+ntent....................................................................................13

2.".8 ater c+ntent.....................................................................................13

2.". *l+!d p+int...........................................................................................13

2.".1% +!r p+int..........................................................................................1"

2.".11 las0 p+int..........................................................................................1"

2.".12 Specific ravit$..................................................................................1"

%=#P!E: @( AU#"I!>..........................................................................................3*

@./ *+&!%G! -!!PI%G & P#$P!# "! /"&I01....................................................31

3.1.1 St+rae pr+blems................................................................................27

3.1.2 ater in t0e f!el...................................................................................27

3.1.3 4!rnabilit$...........................................................................................28 3.1." #i05temperat!re c+rr+si+n................................................................28

3.1. +65temperat!re c+rr+si+n.................................................................28

3.1./ &brasive imp!rities.............................................................................28

@.3 "%-!#I%G........................................................................................................@/

3.2.1 4!ner !alit$ ....................................................................................31

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3.2.2 G++d 4!nerin ractice ....................................................................31

3.2.3 Orderin b!ners ................................................................................31

3.2." Selectin t0e rades +f f!el re9!ired ..................................................31

@.@ "! $I 0!40....................................................................................................@*

3.3.1 Samplin..............................................................................................3"

3.3.1.2 Samplin r+ced!res.................................................................3"

3.3.2 M&'O &nne- ,I samples................................................................3"

3.3.3 Samples f+r &nal$sis...........................................................................3"

3.3." Onb+ard testin...................................................................................3"

@.* 40$#&G! &%5 +&%5I%G.....................................................................................@*

).).6 5ifferent uel 0ypes +andling..............................................................()

).).2 +eating................................................................................................(3

).).( unker 0anks......................................................................................(3

).).) 4ettling tanks........................................................................................(3

).7.3 4ervice tanks........................................................................................(3

).7.8 ayor uel 4torage Problems.............................................................(3

• Sl!de................................................................................................38

• ibres.................................................................................................38

• O-idati+n r+d!cts.............................................................................38

• Micr+bial *+ntaminati+n....................................................................38

• Dirt......................................................................................................38

• inc+mpatibilit$....................................................................................38

).).7 uel Processing..................................................................................3

• !el :ransfer ......................................................................................(9

• Settiln tans t+ service tans...........................................................(9

• .O +verfl+6 and leas.......................................................................(9

@.- F.5 !:E#!MEN!.................................................................................................@-

3..1 Separatin +rces In :0e Settlin :an..............................................38

@.-.3 SU%!I5N S!:#INE:S.......................................................................................*4

3..3 *leanin b$ centrif!e........................................................................"%

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• 0he purifier.........................................................................................)(

• 0he clarifier.........................................................................................)(

• *ombinations.....................................................................................)(

•

*entrifuging high density fuels ..........................................................))

@.-.* Filters..................................................................................................)2

• *old filters .........................................................................................))

• +ot filters ...........................................................................................))

• ine filters ..........................................................................................))

• self cleaning filters .............................................................................))

@.-.- #lternative metho$s...........................................................................)2

• echanical homogenisers ................................................................))

• "ltrasonic 5evices ............................................................................))

• 4tatic filter modules...........................................................................))

• back:flushing filter modules................................................................))

@.-.1 %hemical treatment............................................................................))

• iosides .............................................................................................))

• uel stabilisers..................................................................................))

• uel aditives.......................................................................................))

@.-., !he $aily service tanB........................................................................))

@.-. #fter the service tanB.........................................................................))

%=#P!E: *( FUE" ;IS%5SI!>............................................................................*-

-./ ;IS%5SI!> #ND FUE" AU#"I!>.............................................................................*1

-.3 M#:INE FUE" ;IS%5SI!> UNDE:S!#NDIN8...........................................................*,.2.1 0at is visc+sit$.................................................................................."8

.2.2 #+6 is c+atin visc+sit$ affected........................................................."8

.2.3 #+6 is visc+sit$ meas!red.................................................................."8

.2." :raditi+nal appr+ac0 t+ meas!rin visc+sit$......................................."8

-.@ ;IS%5SI!> #ND I!S EFFE%!S 5N DIESE" EN8INE.................................................*

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.3.1 +6 !el ,isc+sit$..............................................................................."8

.3.1 ;nine +perati+n 6it0 t++ 0i0 visc+sit$............................................."8

-.* M#:INE FUE" ;IS%5SI!> 6EEPIN8.....................................................................*0

5.4.1 Heating of fuel oil .............................................................................../ 3

5.4.2 Viscosity keeping during treatment ................................................./ 3

• 4eparation of heavy fuel....................................................................))

5.4.3 Viscosity keeping of te transfer system......................................./ 3

• uel oil settling tanks..........................................................................))

• uel oil system and service tanks......................................................))

• Pumping.............................................................................................))

-.*.* 6eeping ;iscosity $uring manoevering an$ stan$+still perio$s. ./ 3

• Preparations before starting on heavy fuel........................................))

• $perating and manoeuvring on heavy fuel........................................))

• 4topping the main engine when operating on heavy fuel..................))

• *hange over between heavy fuel and diesel oil................................))

o 4witching from diesel oil to heavy fuel oil...............................))

o 4witching from heavy fuel oil to diesel oil...............................))

-.- ;iscosity %ontrol #rrangement .....................................................................1 @-.-./ ;iscosity %ontrol...............................................................................! 3

-.-.3 Measuring Devices............................................................................! 3

• *apilar 0ube 4ensor .....................................................................))

• &ttenuation 4ensor .......................................................................))

-.-.@ Propotional %ontrol.........................................................................../ 3

-.-.* PI #n$ PID %ontrol ............................................................................/ 3

%=#P!E: -( FUE" S>S!EM CM! I"M#..............................................................4

1./ M#IN EN8INE.....................................................................................................-,

1.3 8ENE:#!5: EN8INES........................................................................................-0

1.@ #US!EM...................................................1/

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/.3.1 #O S$stem......................................................................................../2

/.3.2 Gas Oil S$stem..................................................................................../"

%=#P!E: 1( 5N 95#:D E...............................................................................................................,@

"IS! 5F :EFE:EN%ES.........................................................................................,,

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!#9"E 5F I""US!:#!I5NS

Page

i!re 1....................................................................................................................7%

i!re 2....................................................................................................................7/

i!re 3....................................................................................................................77

i!re "....................................................................................................................7

i!re ....................................................................................................................88

i!re /....................................................................................................................8

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!#9"E 5F %=#:!S

Page

0able 6 ain 0ypes $f uel $il..................................................................................7

0able 2 I4$ *aracteristics.......................................................................................62

0able ( 0ypical values for standard fuels.................................................................67

0able ) fuel oil specification of an => low speed diesel engine of *ap elix. . .67

0able 3 +eavy uels Problems................................................................................6;

0able 8 Purifier Particle #emoval !fficiency............................................................)7

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E

0his project has been made with the intention of providing insights on the current

and appropriate practices in the handling of fuel oil onboard. 0he objective is to

present the precautions to be taken to keep and appropriate fuel ?uality and

viscosity on board, and the actions to take once one is working with it. 0o get a grip

on fuel handling in general, personal research has been done on the topic.

oreover, a general knowledge recompilation about fuel ?uality and viscositytheory was also done. 0his was followed by a study of the current difficulties

involving it and an approach to each aspect affecting the ?uality and viscosity of

the fuel on board *ap elix and 0 Ilma.

Precaution while handling fuel covering the bunkering, storage, analysis, transfers

and treatment is essential. Preparing the ship and crew beforehand will not only

prove an advantage but also necessary when encountering any unusual

conditions. 0he crew should follow, whenever possible, the recommendations of

the manufacturers, ship builder and company, paying special attentions to the

current regulations.

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0hese days, fuel ?uality and viscosity can be kept in the appropriate levels to fit in

the manufacturer@s re?uirements if good practices are carried out on board.

IN!:5DU%!I5N

uel oil has posed an increasing problem to the ship operators. $ver the

years, any new regulation and processes become a challenge to the current

plants facilities which most of the time have not been designed to comply with

these new operating conditions. !very time more precautions have to be takenwhen handling fuel. 0he engineers have to be aware that they can encounter with

low ?uality fuels, different types and that each type of fuel must re?uire to be

treated and handled in different ways. Inapropiate working conditions for the type

of fuel being handled can led to serious implications in safety of life and machinery.

Poor fuel ?uality will sometimes restrict the normal operation of the purifiers,

affecting its treatment rate and time. *onstant adjustments must be done to cope

with the current operation conditions. 0hese can affect the use of separation

e?uipment by producing fast accumulation of sludge and, subse?uently, changes in

the interface position. >hen it comes to the machinery, poor fuel ?uality produces

wearing on the surface of cylinder liners and pistons. It surely affects the fuel

pumps since they are extremely sensitive by obstruction or seiAure. !ven if

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appropriate treatment is done, special attention to viscosity, temperatures and

pressures must be kept.

ecause of their direct concern with fuel, the engineers must get ac?uainted

with future fuel re?uirements and prepare the systems in advance in the area they

expect to deal with. 0hey should make use of all the information and resources

available and most importantly, always proceed with caution.

uel ?uality keeping calls for special knowledge and precautions even in

new building ships designed for new regulations and standards. uel ?uality

keeping poses several problems of its own. 5ifferent conditions can be

encountered with each bunkered fuel and it can bring about many unusual

problems for seamen having little or no experience on this regard.

urther on, we will discuss how to get prepared for these types of

conditions, different types of fuel and fuel problems that can arise. >e will also

discuss necessary actions to take when encountered with some of these problems.

%=#P!E: /

!=E :ESE#:%= P:59"EM

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In this chapter I will propose the objectives of the project, general and specific and

the delimitations and limitations.

/./ Statement of the Pro'lem

uel ?uality and viscosity keeping can be very harsh. If the engineers of the

vessel are not prepared the outcome could be disastrous. It is important to know

what to expect when encountered with different fuels ?ualities and grades, and to

understand what is needed to be done under these conditions to keep fuel as

re?uired by the machinery.

/.3 ?ustification

uel ?uality keeping is not to be taken lightlyB even the most experienced

engineer can find difficult to deal with problems related to poor fuel ?uality and

viscosity keeping. 0horough preparations need to be made to assure a proper

?uality avoiding by these way greater, dangerous and expensive issues. 0here are

essential tools and information re?uired to conduct effective, safe, fuel treatment

that must be taken in account.

4tarting a purifiers main engines, generator and boilers is something all

engineers are more readily prepared for. +owever, there is a risk of suddenly

meeting systems fail, clogging, and machinery damage if the appropriate fuel

specification is not supply.

4ame as every ship is uni?ue, every fuel type has own variations in their

composition. &lthough, some people can easily get ac?uainted with the conditions

of some ship or fuel, ignoring these factors could lead to plant failure. ig efforts

have been made to give a guidance or a trace of the ?uality fuel you are bunkering

and dealing with. $ne of these efforts is the I4$ 9267. >ith this guidance it is

much easier to follow the treatment re?uired according to the type fuel you are to

deal with. ut this canCt assure you that the same treatment can be followed for a

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same fuel grade. !ngineers must go deeper in order to make sure that proper fuel

?uality is being supplied to the machinery.

Increases in world regulations, particularly on the low sulfur emissions for

4!*&Cs is opening an incredibly difficult challenge for fuel ?uality and viscosity

keeping. 4ome of these fuels are in total opposite corners of treatment and

handling. >hile something is good for one fuel, it is total ?uite the opposite for

other fuels. &ppropriate training and familiariAation must be given to the crew for

dealing with these new regulations. $n the other hand, new and increasingly

sophisticated ships, are being built to cope with the high new standards.

.

/.@ 8eneral 5'ectives

0o provide information of the risks, precautions and procedures to follow before,

during, and after dealing with fuel oil in order to keep and appropriate ?uality

showing at the same time the connection between fuel ?uality and viscosity

keeping. aking use specifically of experiencesB !uronav guidanceCs and

procedures. &s well as classification society and manufactures recommendation

and manuals in *ap elix and 0 Ilma.

/.@./Specific 5'ectives

6. 0o create conscience regarding the risk invoving fuel handling on board.

2. 0o present seamen with guidelines for actions to take and general information

when dealing with fuel ?uality and viscosity keeping .

(. 0o help the engineers with a guidance to perform a safe fuel system treatment

and handling onboard.

). 0o leave a legacy to those cadets interested in understanding the aspects

involving fuel ?uality on board a !uronav tanker.

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/.* Delimitation

6. 0his project is aimed to engine cadets, who need to understand the basics of

fuel ?uality and viscosity keeping, the personal safety precautions necessary to

take when handling fuel weather and measures necessary in 0 Ilma and *ap

elix.

/.- "imitations

6. ost of the research was done with the aid of books and manuals on board due

to limited time for scheduled maintenances on board the vessel.

2. uel ?uality and viscosity keeping system are only bounded to the systems and

ship specific manuals and recommendations for 2


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3./ !he Marine Fuels %hallenge

uel remains one of the highest single cost factors in running a ship and also the

source of the most potent operating problems. 0he reason for this is that new

refining techni?ues, introduced as a result of political developments in the iddle

!ast in 6;7(D7), have meant that fluid catalytic cracking and this breaking have

produced a more concentrated residual fuel of very poor ?uality. 0his residual fuel

is the heavy fuel oil traditionally supplied to ships as bunkers and used in the

majority of motor ships of a reasonable siAe for the main engine. 5espite the high

cost of these poor ?uality residual fuels owners generally have no alternative but to

burn them, though some still prefer to use even more expensive intermediate

grades produced as a result of mixing residual fuel oil with distillate.

0he problems are reflected in the effects on the engine in terms of wear and tear

and corrosion resulting from harmful components in the fuel. It is the duty of the

ship@s engineer to be aware of these harmful constituents, their effect on the

operation of the engines and the solutions available to counter the harmful

properties.

3.3 Marine Fuel !ypes

0here are three major types of marine fuelE distillate fuel, residual fuel, and a

combination of the two to create a fuel type known as Fintermediate fuel oil HI$.

In this section, the various grades of marine fuel are introduced using the collo?uial

industry names to group the different fuel types. 0he purpose of this discussion is

to introduce the reader to marine fuels in general to enable assimilation of more

nuanced discussions that are presented in the chapter number three of this report.

we will make a technical discussion of marine fuel regulations involving the names

and standards.

5istillate and residual fuels are blended into various combinations to derive the

different grades of marine fuel oil. !a'le / lists examples of the major marine fuel

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grades and their collo?uial industry names. In terms of cost, distillates are more

expensive than intermediates, and residual fuels are the least expensive.

!a'le / Main !ypes 5f Fuel 5il

Fuel

!ype

Fuel 8ra$e %ollo)uial In$ustry Name

Distillate DM


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because it can be blended with residual fuel. 5$ is manufactured by blending

5* with 6


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any auxiliary engines have now been designed to operate on residual fuels.

>here the residues of the refining process are unsuitable for fuel purposes then

blending is often carried out to bring the fuel within a recogniAed specification.

3.@ :egulations #n$ Stan$ar$s

!xisting regulations regarding marine bunker fuels provide an important backdrop

for the modeling conducted in this analysis and, thus, are summariAed in this

section.

any shipping companies have additional standards for their vesselsB these take

into account the treatment facilities onboard and past service experience with

different fuels.

0hese company standards often have specifications not included in the I4$ 9267

standard.

0he engine manufacturer@s recommendations will take into account specific

re?uirements for their engines, with particular reference to design limitations andservice experience.

1ou should try and make yourself aware of the content of I4$ 9267, and also any

specific re?uirements that your company or the engine manufacturer has for the

fuel for the machinery on your current vessel.

0his will help you understand the handling and treatment re?uirements and will

also highlight possible problems you may have when using the fuels onboard.

3.@./ M#:P5"

0he International aritime $rganiAation@s HI$ FP$ &nnex 'I sets out a

series of regulations impacting international marine bunker fuels. 0hese new

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regulations center on limits for emissions of nitrous oxides H%$x, sulfur oxides

H4$x, and volatile organic compounds H'$*s. uel ?uality regulations in &nnex

'I have been implemented in the form of the I4$:9267 2


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N Density( which is re?uired to determine purification settings and is used to

calculate the amount of fuel bunkered.

N ;iscosity( which is expressed as a fluid@s resistance to flow. In everyday terms

this is Mthickness@. 'iscous Hthick fuels re?uire preheating to reduce the viscosity

and enable good purification, injection and combustion in the engine cylinder.

N Flashpoint( of the fuel indicates the temperature at which a fuel vapour is

produced and can be ignited. In accordance with 4$&4 re?uirements, the flash

point must be above 8< degrees *elsius. H0his does not apply to fuel that will be

used for emergency purposes such as generators, fire pumps and lifeboat

engines.

N #luminium #n$ Silicon C%atalytic fines( are remnants of the cracking process

at the refinery. 0hey are introduced as a catalyst to assist with the refining in a

catalytic cracking process. 0hese highly abrasive particles can cause rapid wear of

engine components and can be difficult to remove or separate using the ship@s fuel

treatment e?uipment

0he table below iIIustrates a shortened version of the new I4$ 9267E2


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t0e t0ird letter< >< &< 4< e< ... < ?< 60ic0 indicates t0e partic!lar pr+perties int0e pr+d!ct specificati+n (ISO 8217)< +r resid!al f!els< a n!mber 60ic0c+rresp+nds t+ t0e ma-im!m inematic visc+sit$< in mm2@s< at % % c

f+r e-ample a pr+d!ct ma$ be desinated in t0e c+mplete f+rm< e.. ISO55

'MG 18%< +r in abbreviated f+rm< e.. 5'MG 18%

!a'le 3 IS5 %aracteristics

4ourceE I4$ 9267 ourth !dition 2


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any of the procedures that are used to ensure safe, pollution free bunkering and

F!sae +f t0e f!elA will have originated from these anti:pollution regulations.

0he following sections we will look at some typical procedures that are necessary

when receiving, handling and Fusing fuel oil bunkers on board ship.

1ou should always make reference to your own vessels@ specific procedures when

carrying out any bunkering operations on board.

3.* Fuel 5il Properties

0he ?uality of a fuel oil is generally determined by a number of specific parameters

or proportions of metals or impurities in a given sample of the particular fuel. 4uch

parameters includeE viscosityB specific gravityB flash pointB *onradson carbonB

asphaltenes contentB sulphur contentB water contentB vanadium contentB and

sodium content. 0wo parameters of traditional importance have been the calorific

value and viscosity. 'iscosity, once the best pointer to a fuel@s ?uality or degree of

heaviness, is now considered as being only partially a major ?uality criterion

because of the possible effects of constituents of a fuel.

3.*./ %alorific value

0he calorific value or heat of combustion of a fuel oil is a measure of hydrogen thatis, an amount of hydrogen e?ual to one:eighth the weight of the oxygen is nullified.

0he sulphur compounds are assumed to have their combustion heat nullified by

the oxy:nitrogen ones. *alorific value is given in kcalDkg of fuel.

0he calorific value as determined by a bomb calorimeter is the gross or Mhigher@

value which includes the latent heat of water vapour formed by the combustion of

the hydrogen. 0he net or Mlower@ calorific value is that obtained from subtracting this

latent heat. 0he difference between the gross and net values is usually about 8


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3.*.3

;iscosity

0he viscosity of an oil is a measure of its resistance to flow which decreases

rapidly with increase in temperature. +eating is necessary to thin the heavy fuels of

high viscosity in current common use and ease their handling.

3.*.@ %etane num'er

0he cetane number of a fuel is a measure of the ignition ?uality of the oil under the

conditions in a diesel engine. 0he higher the cetane number, the shorter the time

between fuel injection and rapid pressure rise. & more usable pointer of ignition

?uality is the diesel index, expressed asE

where G O specific gravity at 8


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carbon on fuel injection noAAles. 0he #amsbottom method has largely replaced the

*onradson method of carbon residue testing, but it gives roughly the same results.

3.*.1 #sh content

0he ash content is a measure of inorganic impurities in the fuel. 0ypically, these are

sand, nickel, aluminium, silicon, sodium and vanadium. 0he most troublesome are

sodium and vanadium which form a mixture of sodium sulphate and vanadium

pentoxide, which melt and adhere to engine components, particularly exhaust

valves.

3.*., Sulphur content

0his has no influence on combustion but high sulphur levels can be dangerous

because of acid formation, mentioned earlier in this chapter. In recent years there

has been a tendency to e?uate sulphur content with cylinder liner wear, but

opinions differ on this matter. H4ee also chapter on !missions.

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3.*. 7ater content

0his is the amount of water in a given sample of the oil and is usually determined

by centrifuging or distillation.

3.*.0 %lou$ point

0he cloud point of an oil is the temperature at which crystalliAation of paraffin wax

begins to be observed when the oil is being cooled down.

3.*./4 Pour point

0his is the lowest temperature at which an oil remains fluid and thus is important to

know for onboard handling purposes. &n alternative is the solidifying point or the

highest temperature at which the oil remains solid. It usually lies some ( * below

the pour point. &ccording to one major enginebuilder, the lowest admissible

temperature of the fuel should be about 3Q6< * above the pour point to secure

easy pumping.

3.*.// Flash point

0he flash point is defined as the lowest temperature at which an oil gives off

combustible vapours, or the point at which airDoil vapour mixture can be ignited by

a flame or spark.

components, fuels can have identical densities but widely varying individual

component densities. &part from being an indicator of the Mheaviness@ of a fuel,

when measured by a hydrometer the specific gravity can be used to calculate the

?uantity of fuel by weight in a tank of given dimensions.

3.*./3 Specific gravity

0his is normally expressed in kgDm( or gDcm( at 63 *. &s the density of the fuel

depends upon the density of the individual

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3.- !ypical values for stan$ar$ fuels

!a'le @ !ypical values for stan$ar$ fuels

Ilma manuals 34/*

0he following is the fuel oil specification of an => low speed diesel engine of

*ap elix. 0he properties are considered the worst in each case that can be burnt

in these particular engine.

!a'le * Fuel oil specification of Man 97 low spee$ $iesel engine of %ap Feli&

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%=#P!E: @

AU#"I!> 6EEPIN8

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@./ %hallenge Beeping a Proper fuel Auality

P#$!4 >I0+ +!&'1 "!4

0he problems of present and future heavy residual fuels can be categoriAed asE

6. 4torage and handling.

2. *ombustion ?uality and burnability.

(. *ontaminants, resulting in corrosion andDor damage to engine componentsE

for example, burnt out exhaust valves.

!a'le - =eavy Fuels Pro'lems

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@././ Storage pro'lems0he problems of storage in tanks of bunker fuel result from build:up of sludge

leading to difficulties in handling. 0he reason for the increase in sludge build:up is

because heavy fuels are generally blended from a cracked heavy residual using a

lighter cutter stock resulting in a problem of incompatibility.

0his occurs when the asphaltene or high molecular weight compound suspended

in the fuel is precipitated by the addition of the cutter stock or other dilutents. 0he

sludge which settles in the bunker tanks or finds its way to the fuel lines tends to

overload the fuel separators with a resultant loss of burnable fuel, and perhaps

problems with fuel injectors and wear of the engine through abrasive particles.

0o minimiAe the problems of sludging the ship operator has a number of options.

+e may ask the fuel supplier to perform stability checks on the fuel that he is

providing. unkers of different origins should be kept segregated wherever

possible and water contamination kept to a minimum. Proper operation of the

settling tanks and fuel treatment plant is essential to prevent sludge from entering

the engine itself. & detergent:type chemical additive can be used to reduce the

formation of sludge in the bunker tanks.

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@./.3 7ater in the fuel

>ater has always been a problem because it finds its way into the fuel during

transport and storage on the ship. ree water can seriously damage fuel injection

e?uipment, cause poor combustion and lead to excessive cylinder liner wear. If it

happens to be seawater, it contains sodium which will contribute to corrosion when

combined with vanadium and sulphur during combustion.

>ater can normally be removed from the bunkers by proper operation of

separators and properly designed settling and daily service tanks. +owever, where

the specific gravity of the fuel is the same or greater than the water, removal of the

water is difficult or indeed not possible and for this reason the maximum specific

gravity of fuel supplied for ship@s bunkers has generally been set at


34/113

which employ a reactive combustion catalyst can also be used to reduce the

products of incomplete combustion.

@./.* =igh+temperature corrosion

'anadium is the major fuel constituent influencing high:temperature corrosion. It

cannot be removed in the pre:treatment process and it combines with sodium and

sulphur during the combustion process to form eutectic compounds with melting

points as low as 3(< *. 4uch molten compounds are very corrosive and attack

the protective oxide layers on steel, exposing it to corrosion.

!xhaust valves and piston crowns are very susceptible to high temperature

corrosion. $ne severe form is where mineral ash deposits form on valve seats,

which, with constant pounding, cause dents leading to a small channel through

which the hot gases can pass. 0he compounds become heated and then attack the

metal of the valve seat.

&s well as their capacity for corrosion, vanadium, sulphur and sodium deposit out

during combustion to foul the engine components and, being abrasive, lead to

increased liner and ring wear. 0he main defence against high temperature

corrosion has been to reduce the running temperatures of engine components,

particularly exhaust valves, to levels below that at which the vanadium compounds

are melted. Intensively cooled cylinder covers, liners, and valves, as well as

rotators fitted to valves, have considerably reduced these problems. 4pecial

corrosion resistant coatings such as 4tellite and plasma coatings have been

applied to valves.

@./.- "ow+temperature corrosion

4ulphur is generally the cause of low:temperature corrosion. In the combustion

process the sulphur in the fuel combines with oxygen to form sulphur dioxide

H4$2. 4ome of the sulphur dioxide further combines to form sulphur trioxide

H4$(. 0he sulphur trioxide formed during combustion reacts with moisture to form

26


35/113

sulphuric acid vapours, and where the metal temperatures are below the acid dew

point H68< * the vapours condense as sulphuric acid, resulting in corrosion.

0he obvious method of reducing this problem is to maintain temperatures in the

engine above the acid dew point through good distribution and control of the

cooling water.

0here is always the danger that an increase in temperatures to avoid low

temperature corrosion may lead to increased high temperature corrosion. &ttack on

cylinder liners and piston rings as a result of high sulphur content fuels has been

effectively reduced by controlled temperature of the cylinder liner walls and alkaline

cylinder lubricating oils.

@./.1 #'rasive impurities

0he normal abrasive impurities in fuel are ash and sediment compounds. 4olid

metals such as sodium, nickel, vanadium, calcium and silica can result in

significant wear to fuel injection e?uipment, cylinder liners, piston rings and ring

grooves.

+owever, a comparatively new contaminant is the metallic catalyst fines composed

of very hard and abrasive alumina and silica particles which are a cause for much

concern. 0hese particles carry over in the catalytic cracking refinery process and

remain suspended in the residual bottom fuel for extended periods. It has been

known for brand new fuel pumps to be worn out in a matter of days, to the point

where an engine fails to start through insufficient injection pressure, as a result of

catalyst fines in the fuel. 0he only effective method of combating abrasive particles

is correct fuel pre:treatment. 4eparator manufacturers recommend that the

separators should be operated in series Ha purifier followed by a clarifier at

throughputs as low as 2< per cent of the rated value.

22


36/113

@.3 9unBering

4hips burning +$ in combustion e?uipment will, at some time in the voyage

cycle, have to bunker fuel to replenish what has been consumed.

unkering may take place offshore, at anchor or alongside. It may be pumped

from road tanker, bunker barge or another tanker or ship.

@.3./ 9unBer Auality

0his is probably the most common area for complaint. & typical wording is as

followsE

B:0e c0arterers s0all s!ppl$ b!ners +f a 9!alit$ s!itable f+r b!rnin in t0e s0ip=s

enines and a!-iliaries and 60ic0 c+nf+rm t+ t0e ISO 9267 "t0 ;diti+n.

:0e +6ners reserve t0eir ri0t t+ mae a c@aim aainst t0e c0arterers f+r an$

damae t+ t0e main enines +r t0e a!-iliaries ca!sed b$ t0e !se +f !ns!itable

f!els +r f!els n+t c+mpl$in 6it0 t0e ISO 9267 "t0 ;diti+n standards +r 60ic0

+t0er6ise pr+ve !ns!itable f+r b!rnin in t0e s0ip=s enines +r a!-iliaries. :0e+6ners s0all n+t be 0eld resp+nsible f+r an$ red!cti+n in t0e s0ip=s speed

perf+rmance and@+r increased b!ner c+ns!mpti+n< n+r f+r an$ time l+st and +t0er

c+nse9!ences.B

&nother typical clause relates to fuel oil sampling and analysisE

B:0ree samples +f all f!el s0all be taen d!rin deliver$< sealed and sined b$

s!ppliers< *0ief ;nineer and *0arterers= aent< eac0 +f 60+m s0+!ld retain +ne

sample. If an$ c@aim s0+!ld arise in respect +f t0e 9!alit$ +r specificati+n +f t0e

f!el s!pplied< t0e O6ners and *0arterers aree t+ 0ave samples +f t0e f!el

anal$Ced b$ a m!t!all$ areed anal$st.B

2(


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@.3.3 8oo$ 9unBering Practice

etween the refinery and the delivery of the bunkers onboard, via any intermediary

storage that might be re?uired, are many opportunities for the fuel to become

contaminatedE sometimes so badly that it may damage the ship@s machinery and

associated systems. !specially threatening is the presence in the fuel of catfines

resulting from the catalytic cracking stage at the refinery in which the oil is heated

over aluminium silicate catalyst, a substance harder than metal.

Immediate and longer term risks to ship and machinery are associated with poor

fuel ?uality, including fire and explosion, loss of main engine power andDor auxiliary

power black:out, and difficulty in fulfilling charter party clauses with regard to ship

speed, engine power and specific fuel consumption.

ittle legislation exists to govern bunker fuel but the parameters of the international

standard I4$ 9267 have been widened in recent years. 4ince most risk

associated with bunkers impacts on the ship and owner Heven though the fuel is

bought by and belongs to any charterer the best protection is for all parties to

know exactly what fuel is needed for the vessel, and then to test that the delivered

bunkers meet these re?uirements. ost problems and disputes can be traced back

either to the ordering or sampling of the fuel. 0he traditional way of ordering

bunkers has been by ?uoting I$ grades, which only refer to viscosity at 3< *,

but this can be technically inaccurate. It is more important in the first instance to

make sure that the fuel is suitable for the machinery and fuel system in which it will

be used. 0he best starting point is the fuel specification provided by the engine

builder. It makes commercial sense for ship operators to follow a recogniAed

specification such as I4$ 9267. 0his will help to secure a charter party and should

help to secure economically priced bunkers worldwide. 0he charter party clause

should clearly state what fuel is re?uired and may also include other aspects, such

as segregation, testing and the services of a surveyor for ?uantity determination.

0he charter party clause should also be kept as simple as possible, loyd@s

#egister recommending the following wording as an exampleE M*harterer to provide

all fuel oil and diesel re?uired, in accordance with I4$ 9267E6;97, Grades # . . .

2)


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and 5 as updated from time to time@. 4hip operators are encouraged to stipulate

that the bunker supplied is Mfit for its intended use@ on the delivery note.

&mong the key parameters of a fuel specification areE

N & maximum viscosityE this is re?uired to be within the engine builder@s

specified limitB it is also a guide to the storage and handling properties of the fuel.

N & maximum density or specific gravityE dictated by the ship@s fuel treatment

plant.

N & minimum flash pointE dictated by safety regulations for the storage of fuel

at sea.

N & maximum pour pointE this limits the amount of heating re?uired to store

and handle the fuel.

N & maximum water content.

N & maximum sulphur contentE may be necessary to satisfy regional

environmental regulations but is also desirable to limit the corrosive products of

combustion and to ensure that the lubricants used in the engine can cope with

these products.

@.3.@ 5r$ering 'unBers

0o ensure that the correct ?uantity and type of fuel is onboard at any particular time

it is necessary that bunkering operations are planned correctly.

If it is left to the *hief !ngineer onboard to order the bunkers, the bunker plan will

have to be drawn up based on information about the expected trade pattern of the

vessel.

+e will have to take into account various factors when calculating ?uantities and

forming his bunker plan such asE

• voyage length

• vessel speed re?uirements and therefore expected fuel

consumption rate

• re?uired fuel reserve : legislative restrictions

23


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• available storage capacity In addition he may have to take

into account other factors such asE

• charterer@s re?uirements

• cost and availability of fuel at future ports of call $nce the

re?uired ?uantity has been calculated then the fuel can be

ordered.

@.3.* Selecting the gra$es of fuel re)uire$

5ifferent grades of fuel may be re?uired for the various machinery and e?uipment

fitted onboard the vessel. !ven for those vessels using the same fuel for all of the

machinery onboard it will be normal to carry three grades of fuel to meet different

operating conditions. 1ou should be aware that current air pollution regulations

contained in P$ &nnex 'I limit the level of sulphur allowed in marine fuel,

with a reduced level in 4$x !mission *ontrol &reas H4!*&s.

P$ &nnex 'I has timetables for the reduction of the maximum allowable

sulphur content in fuels both inside and outside 4!*&s. %ational legislation, for

example within !uropean "nion countries, may re?uire even lower sulphur levels.

It is therefore important that the vessel@s trading pattern is taken into account

when selecting the grades of fuel to be bunkered.

If the trading pattern of your vessel includes operation within a 4!*& a

?uantity of low sulphur fuel will have to be carried onboard.

0his may also be the case if the future trading pattern of the vessel is

uncertain.0his will normally be in addition to the regular grades of fuel re?uired, as

fuel tends to become more expensive as the sulphur level is reduced.

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@.@ Fuel 5il !est

To be able to check whether the specification indicated and/or the stipulated delivery

conditions have been complied with, we recommend that a minimum of one sample of

each bunker fuel lot be retained. In order to ensure that the sample is representative

for the oil bunkered, a sample should be drawn from the transfer pipe at the start, in

the middle, and at the end of the bunkering period.

The samples received from the bunkering company are frequently not identical with the

heavy fuel oil actually bunkered. It is also appropriate to verify the heavy fuel oil

properties stated in the bunker documents, such as density, viscosity, and pour point. If

these values deviate from those of the heavy fuel oil bunkered, there is a risk that the

heavy fuel oil separator and the preheating temperature are not set correctly for the

given injection viscosity.

@.@./

Sampling

0here is no point in taking a sample of the fuel being delivered unless it is a

representative sample.

0here are accepted procedures for collecting, labelling, distribution and onboard

retention of the sample.

1ou should be aware of the re?uirements for your vessel and follow them carefully.

It is recommended that only the correct containers are used for samples, and that

the sample is obtained by a continuous drip method so that it represents the fuel

delivered throughout the bunkering operation.

@.@./.3 Sampling Proce$ures

>hen bunkering starts, place a container under the sampler, open the sampler

valve fully and flush the sampler with fuel. It is good practice to check this sample

from fuel initially pumped onboard as it may be high in water content from the

bunker barge@s tanks. &fter flushing the sampler, close the valve and attach a

27


41/113

suitable clean container to the valve. &djust the needle valve to give a slow and

steady drip. 0ime the fill rate so that it will provide for sufficient estimated sample

over the expected delivery period.

R P$ sample point showing cubitainer attached

If the sample container fills during the bunkering period, remove it and place an

empty

sample container H*ubitainer on the sampler and continue to draw a sample.

$n completion of bunkering, mix together the samples from both containers to

ensure you

have a good, representative sample from the bunkering operation.

N always ensure that the sampler valve is fully open to allow the sampler to drain

N always close the sampler valve before blowing through the fuel lines on

completion

of bunkering

N close the sampler valve if pumping stops, to prevent the sample being drawn

back,

under vacuum, into the fuel line

4elect three or four clean sample bottles. 0he exact number depends on the final

destination

of the various samples. 0o cover all eventualities, it is recommended that four

representative

samples are obtained from the delivery. 0he list shows the samples that are

re?uired.

0he distribution of the samples beingE

N supplier@s sample Hfrom their P$ connection

N ship@s sample for retention on board

N onboard analysis sample

N sample for independent analysis

29


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0he full *ontainer should be placed in the pourer box and thoroughly shaken to

ensure that the contents are well mixed. &ttach the pourer spout and gradually

transfer the

contents into the sample bottles, filling each a little at a time. If more than one

*ubitainer

was used during bunkering, then transfer a portion into each of the bottles.

*omplete

the document labels and attach one to each sample bottle.

&lways have the barge operator to witness the removal and sealing of the sample

bottleHs

Hshown below. If this re?uest is refused, or if no witness is provided, then note this

in the

delivery log.

@.@.@

M#:P5" #nne& ;I samples

It is now a re?uirement that a sample is taken for P$ &nnex 'I purposes.

0he sample has to be specifically for the purpose of meeting the P$

regulations.

It must be stored securely and retained onboard for at least twelve months.

0he sample should be taken at the ship@s inlet manifold and the sample bottle must

be properly sealed on completion.

5etails of the sample bottle serial number must be added to the bunker delivery

note and entered into the oil record book or log book.

0here should be documentation onboard your ship giving the full re?uirements of

these regulations.

@.@.* Samples for #nalysis

any ship operators make use of a specialist fuel analysis service to get

detailed information on the ?uality of the fuel delivered.

2;


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0he major classification societies offer this service and usually supply the

containers, labels and instructions for taking and forwarding the samples. 0he

analysis report covers the fuel properties and contaminant content. It also gives

advice on storage and handling and predictions on the effect of using the fuel.

It is also good practice to carry out onboard testing of the fuel as a check on

the accuracy of the shoreside analysis report.

@[email protected] 5n'oar$ testing

$nboard testing is not meant to give accurate results but should give a rough

indication for the main parameter values of the fuel. 0ypically, onboard testing is

carried out using simple test e?uipment.0he parameters that are usually tested are

shown in the list.

0he results from these tests will give an early indication if using the fuel is likely to

cause any operational problems. 0ake the opportunity to do these tests using the

fuel onboard your vessel so that you become more familiar with them.

5ensityE using hydrometer

'iscosityE using simple viscosimeter

&brasive contentE using a pair of glases slides

*ompatibilityE using spot test

>ater contentE using water detector paste.

Figure / Density Measurement Instrumentation

(


44/113

5ensity measurement Hseagull 2hen heavy fuel oil is bunkered it is stored in the shipSs bunker tanks. 0hese

tanks are of varying shapes, siAes and capacities depending on the ship siAe,

construction and trade.

uel oil is transferred from storage tanks to settling tanks via a fuel oil

transfer pump and its associated suction strainer. rom the settling tanks it is

transferred to service tanks by way of the purification system. 0wo fuel oil

centrifugal separators are installed with appropriate supply pumps, heaters and

controls. 0he system and e?uipment is configured to permit operation of the

separators in parallel or in series, either in a purifierDpurifier, clarifierDclarifier or

purifierDclarifier se?uence. *entrifuge heater crossover capability is also illustrated.

uel oil is discharged from the centrifugal separators to the service tanks either

directly, or via an additional duplex filter if it is suspected that the separators have

not removed all contaminants. 0he fuel oil is retained in the service tanks until it is

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drawn to the main engine via the fuel oil service system. 0race heating of the fuel

oil piping, if fitted, should be activated during these transfer operations.

@.*./ Different Fuel !ypes =an$ling

0he different grade re?uirements will dictate the storage arrangements onboard the

vessel. It is recommended that fuels from different sources, particularly residual

fuels, should not be mixed in storage. In other words, new bunkers should not be

loaded into a tank containing any of the previous bunkers. 0he purpose of this

recommendation is to minimise the risk of fuel compatibility problems which may

result in the formation of sludge and heavy deposits either in storage tanks or in

treatment e?uipment.

ixtures of residual fuels can become unstable even if the original fuels were

stable, so mixing should be avoided whenever possible, as was stated in an earlier

chapter.

In practice, this is not usually possible, since fuel tanks are not normally completely

empty unless they have been manually cleaned. 0hey should, however, only

contain the minimum ?uantity of old bunkers before filling with the new batch.

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@.*.3 =eating

&II fuel oil bunker tanks and waste oil tanks must have some form of tank heating.

%ormally the heating is by way of steam produced by an oil:fired boiler and passed

through coils inside the oil tank. $ther ways to heat the fuel tanks are by using

thermal oil. 0his also utilises an oil fired boiler that heats the thermal oil which is

then circulated through coils inside the tank by a pump. 0emperature regulation

and monitoring can be automatic and self:adjusting but is commonly effected by

checking the tank temperature and manually adjusting the heating accordingly.

+eating coil integrity in the case of using steam as the heating should be monitored

by checking the steam condensate returns in the engine room observation tank. If

oil is observed, the source must be traced. &n increase in steam consumption

should be checked out as this may indicate a steam coil failure. In the case of

thermal oil heating, oil analysis should be regularly taken and results checked for

any +$ contamination. onitoring of the thermal oil header tank leve I should

also be strictly monitored. $nboard viscosity checks may be useful in determining

any thermal oil viscosity change caused by +$ contamination.

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@.*.@ 9unBer !anBs

0he bunkering capacity of ships varies from ship to ship. In fact not even sister

ships may have the same bunker tank capacity as a result of small design changes

and tank fabrication discrepancies during building.

0he maximum allowable filling capacity of a bunker tank varies from one company

to another and should be documented in the companySs safety management

system. %ormally, the maximum is in the range of 93 to ;


48/113

rom a safety standpoint, fuel oils must never be heated in shipsS bunker tanks at

or above the fuelSs flash:point. 0he tanks should be insulated where possible to

reduce heat loss. It is important to shut off the settling tank heat source once its

contents are up to temperature, because continuous heating will produce thermal

currents within the tank which interfere with the settling process. 4hips have high

tank temperature alarms and may also have automatic regulators.

ecause of constant heat loss from a settling tank, it may be necessary to

reactivate the tank heating system periodically to maintain its contents at 8ater and sludge should be removed on a regular basis by mean s of these drains

as part of a normal watchkeeping routine. 5uring periods of heavy weather it is

necessary to drain fuel storage tanks more regularly than usual. 4hipsS engines

have stopped when this has not been carried out in rough weather.

@.*.- Service tanBs

4ervice tanks, or day tanks, have a very important function in the overall treatment

of heavy fuel oil for diesel engines. 0hey provide a final settling function for water

and solids, a heating function and a thermal stabilising function. 0he settling

function is primarily a backup in the event of a failure of the separators andDor

during a by:pass of the filtration system, should this emergency be necessary. It

should be noted that damage to engine fuel injection e?uipment and the engine

may occur if this is carried out. $n some ships, one +$ service tank is fitted. 0his

obviously makes the changeover to low sulphur fuel oil a much more time

consuming procedure, as the service tank high sulphur fuel has to be consumed

before low sulphur fuel is introduced. $n most modern ships, however, two service

tanks are provided. 0his follows 4$&4 re?uirements for redundancy of fuel oil

service tanks, which apply to ships built on or after 6 Uuly 6;;9. H4ee 4$&4 2


49/113

operation for engines andDor boilers. uel changeover procedures are discussed

below. 0he service tanks normally have high and low suction lines with downturned

suction diffuser elbows. 0he cleanest fuel oil is available from the upper Hhigh

suction. 0herefore it should be used whenever possible. 0he service tanks should

have bottom drain connections for water and sludge stripping. 0he water and

sludge from this bottom drain should be removed at regular intervals as part of the

engine room watchkeeping procedures. & typical heavy fuel oil service tank system

is shown below.

@.*.1 Mayor Fuel Storage Pro'lems

0o have a deeper understanding of the mayor problems we can have onboard in

this section we are going to make a little explanation about them so we can advise

then and avoid any problem with the system or the engines.

)ludge,

4ludge is a contaminant that results from the handling, mixing, blending,

and pumping of heavy fuel while stored at, and after it leaves, the refinery.

4torage tanks, heavy fuel pipe lines, and barging can all contribute to the

build:up of sludge. >ater contamination of a high asphaltene fuel oil canproduce an emulsion during fuel handling which can contain more than 3hereas cleaning strainers is not a difficult task, the

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50/113

fre?uency of cleaning and the need for round:the:clock attention generally

create problems with the allocation of manpower. & centrifuge normally is

ineffective in removing oil soaked fibres because they have the same

density as the oil being purified. +ence, downstream manual or auto:

strainers and fine filters can be expected to clog ?uickly, and continue to

clog fre?uently until the entire amount of a fibre contaminated fuel has been

consumed or removed.

#idation products

0his form of contamination is the result of the marine residual fuel ageing,

either before or after it is bunkered. #esidual fuels are not stable for long

periods at elevated storage temperatures. 0he time from the refinery to use

onboard ideally should be less than three months. It is anticipated that future

residual fuels resulting from more intense secondary processing will be even

less stable. +eated heavy fuels, stored in uncoated steel tanks and exposed

to air Hoxygen will oxidise and polymerise with time. 0he resultant sludges,

gums and resins will initially form in solution and then collect and settle or

adhere to the tankSs surfaces. &lso, as heavy fuels age, their shipboard

conditioning and treatment become more difficult. In the extreme, the dieselengineSs combustion process can deteriorate, causing increased fouling

deposits and corrosion, as a result of burning such partially oxidised older

fuel oils. Generally, residual fuel oils should not be bunkered or utilised as

ballast, trim, or held in reserve for extended periods. 0he oldest on spec fuel

on the ship should be burned first to prevent any heavy fuel oil from ageing

beyond three months from its bunkering date.

Micro0ial contamination,

icrobial contamination usually occurs with jacket water systems, diesel

fuels and lubricating oils onboard ship. +owever, there have been instances

where +$ and I$ have been contaminated.

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icrobial contamination of diesel fuel oil has unfortunately become a

common occurrence.

icrobes are microscopic, living organisms, and include bacteria, fungi and

yeast, all of which can cause problems in the fuel system.

acteria, normally the main source of problems, can be either aerobic types,

which need oxygen to survive, or anaerobic types, which do not need

oxygen.

>hen bacteria are present in water contaminated diesel fuel, colonies can

form as slimy masses at the interface between the settled water and the

fuel.

&s the colonies break up they can be carried through the fuel system

causing severe filter blockages.

&erobic bacteria usually initiate the problem but, as the oxygen supply

reduces, anaerobic bacteria can appear with the colonies growing rapidly.

In many cases the fuel delivered to the vessel will consist of a number of

different components from the refinery process which have been mixed

together in order to meet the specification given in the fuel standard.

+eavy fuel oil, with either viscosity or density values outside of the limits of

the fuel standard, may have distillate fuel mixed with it to try and improve its

condition.

If the mixture is not stable then the two components will separate out during

storage leaving the heavy fuel component in the lower part of the tank and

the distillate above it.

$bviously the high values of density and viscosity may cause problems

when transferring or pre:treating the fuel before final use.

1ou can reduce the risk of this occurring by ensuring that the fuel storage

temperature is not excessive as this may accelerate any separation.

Dirt(

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uel oil can be contaminated from a number of sources, these include the

raw crude oil, the refining process and the transportation and storage stages

of supply. 4ome of the contaminants are solid material including sand, soil,

rust and other debris. >ater, either salt or fresh, is also often present in the

fuel.

5uring storage some of the water and dirt will settle out and collect in the

bottom of the tank. 0his has to be removed, either by draining or manual

cleaning, so that it doesn@t carry over into the fuel systems. It also means

that there has to be suitable filters and pre:treatment facilities onboard to

remove any remaining water and dirt which has not settled.

Incompati'ility(

Incompatibility is the term used to describe a situation when two different

batches of fuel, each of which is normally stable, react when mixed together,

resulting in heavy sludge deposits in either the storage tanks or in the pre:

treatment e?uipment.

0he result of this condition can be that the fuel becomes unusable and the

vessels operation is seriously affected.4evere sludge accumulation in the fuel treatment e?uipment, resulting in

more fre?uent cleaning, can mean that the treatment rate cannot keep up

with consumption re?uirements.

It should be standard practice when bunkering a new batch of fuel that it is

only loaded into empty or nearly empty tanks.

ixing with previous bunkers should be avoided whenever possible.

*.*., Fuel Processing

0he shipownerSs first point of active fuel control and handling begins at the shipSs

bunkering connection. 0he movement, storage, inventory and final processing of

the fuel is the responsibility of the shipSs operating personnel. Pre:planned and

careful execution of fuel oil management within the shipSs transfer and processing

(;


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systems will minimise the potential for creating fuel compatibility and combustion

problems.

• Fuel transfer

uel oil is transferred from storage tanks to settling tanks via a fuel oil

transfer pump and its associated suction strainer. & transfer pump normally

is installed to move fuel oil from storage tanks to settling tanks. $ne positive

displacement transfer pump, protected by suction strainers and a pressure

relief valve, and a pump bypass line, is normally fitted. 0he transfer pump

flow rate depends on engine fuel consumption rate and service and settling

tank siAe.

Proper arrangement of system valves adds distribution flexibility to the

transfer system. 0hese valves normally permit fuel oil from any storage tank

to be pumped to either settling tank, to either service tank, to the remainder

of the fuel oil storage tanks or, in some systems, overboard to a barge or

other storage facility via the bunkering manifold.

Internal fuel oil transfers must always be recorded in the $#. 0he internal

transfer of fuel oil onboard ship must be treated with the same precautions

as during bunkering.

Settling tanBs to service tanBs(

0he transfer of fuel oil from the settling tank to the service tank is normally

carried out by using the onboard +$ purifiers. 4ome ships have the facility

to use oil in the engines and boilers directly from the settling tank, thus by:

passing the fuel oil purifiers. 0his by:pass system is for emergency use only

and should be strictly avoided, where practicable, at all other times. 4erious

engine damage may occur if this by:pass system is used for any length

oftime.

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F.5 5verflow an$ "eaBs

&s we know most of ships fuel arrangement is provided with a overflow tank

were is coming the overflow from all .$ tanks doesnCt matter the type of

fuel containing. if good transfer procedures for topping up tanks are

followed usually is not filled by means of overflowing. ost of the time is

filled slowly from the .$ leak lines, from main engines and auxiliary engines

also is fill by the back flush filter or any auto filtration system to avoid lost of

fuel so as we can see these fuel is reach in impurities and mixtures of fuels

of different types. >hen re?uired these fuel most be transfer and apropiate

handling of it must be done usually is recommended to be send back to the

settling tanks but experiences dealing with these type of fuel have shownthis can led to heavy sludgeCs so as recommendation big ?uantities

transfers from these tank must be avoided at the same time.

@.-. F.5 !reatment

In the previous chapters we have concentrated on the storage of fuel onboard and

the procedures and systems in place to achieve this safely with a minimum risk.

0he condition of the fuel is, however, unfit for use without further cleaning and pre:

treatment. In this chapter we will look at the way in which we can prepare the fuel

ready for use in a diesel engine fuel system.

0he extent of the treatment really depends on the grade of fuel that we are

operating withB distillate fuels re?uire far less treatment than residual fuels.

*.-./ Separating forces in the settling tanB>e have already said that the settling tank relies on a difference in density for

separation to occur due to the effect of gravity. +owever, this is not the whole story.

&ll matter is affected by gravity. &n object will fall to the earth due to gravitational

force acting on it which is determined by the object@s mass and the acceleration

due to gravity.

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0he air resistance results in a drag force which acts to slow down the rate of fall.

0he difference between the two forces determines the speed at which the object

will fall.

4imilarly, in the settling tank, and ignoring buoyancy forces, the water droplets and

dirt particles are subject to a Mfalling@ force and the fuel oil provides the drag force.

0he siAe of the drag force is determined by the viscosity and density of the fuel and

the surface area of the particle.

&t increased temperature, the density and viscosity of the fuel oil decreases, and

therefore, the drag force reduces.

*.-.3 Suction strainers

0he settling tank low suction connection will be used for normal operation

If there is a build up of dirt in the bottom of the tank, or, if vessel movement in

rough weather is likely to disturb the settled dirt and water, then the high suction

can be used.

0his will reduce the amount of dirt and water drawn from the tank by the pump.

& suction strainer is fitted between the tank outlet valves and the pump inlet to

protect the pump from damage by the larger particles of dirt.

0he suction strainer usually has a coarse mesh to help ensure an acceptable flow

to the pumpB only relatively large particles of dirt are removed at this stage.

urther cleaning of the fuel is necessary before it can be transferred to the service

tank for use in a diesel engine fuel system.

0his can be achieved dynamically using centrifuges or by using a static filter

module.

oth of these devices are usually self cleaning.

1ou will probably have one or other of these fitted on your current vessel.

*.-.@ %leaning 'y centrifuge

>e have seen that a settling tank relies on a difference in density to separate

different li?uids and solids.

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0his is a slow process due to the fact that there is not much difference in the

densities of fuel and water, and so the separating forces are relatively small.

0o speed up the process the separating forces need to be increased and this is the

purpose of the centrifuge.

0he centrifuge usually consists of a gear driven bowl contained within a casing

provided with suitable inlet and outlet passages.

0he high speed rotation of the centrifuge bowl generates forces many times

greater than gravitational force due to the centrifugal effect.

0his increases the separating force between the different components of the

mixture passing through the bowl.

0he heavy components of the dirty fuel mixture, usually solids and water, move to

the outer part of the centrifuge bowl.

& compact stack of conical discs are used to assist the separating process.

0he centrifuge can be set up to allow discharge of water and dirt or to collect dirt in

the outer part of the bowl.

ost centrifuges are designed as self cleaning units and have an automatic, timed,

sludging facility.

&ll ships designed to operate on heavy fuel oils will have centrifugal separators

Hpurifiers as part of the engine room e?uipment. It should always be remembered

that purifiers have their limitations and we cannot expect a ship@s fuel oil treatment

processing plant to render every fuel oil fit for use. +owever effective design and

maintenance will almost certainly provide ade?uate protection against the

potentially harmful effects of the vast majority of fuel oils delivered. >ater and

sediment levels in the fuel can be effectively controlled in well maintained and

correctly operated purifiers. $n the flip side, poorly maintained and operated

purifiers will fail to improve fuel oils to an acceptable ?uality and result in undue

wear or damage to the engine

)(


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0he centrifugal separator is the foundation of the total shipboard fuel treatment

system.

Its operation must be thoroughly understood by the shipboard engineers so that

they can immediately troubleshoot heavy fuel oil problems as they occur. &

treatment problem cannot wait until the next port. ajor main engine damage can

rapidly result from lack of effective fuel oil purification.

0he following actions are necessary to ensure a proper cleaning of the +$E

N 4election and operation of the fuel oil centrifuges

N according to suppliers recommendation

N *orrect +$ temperature at inlet to the centrifuges

N *orrect throughput of fuel through the centrifuges

N Proper density of +$ in conformance with the centrifuge specification

N Proper maintenance of the centrifuges. If properly operated, a centrifuge

has a removing efficiency of close to 6


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0he importance of adjusting the throughput if the temperature is changed is

illustrated in ig. 6, which shows an example of the relationship between

temperature and

throughput. or example, a centrifuge operating with an inlet temperature of ;


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• !he purifier(

>hen a centrifuge is set up to continuously discharge water it is referred to as a

purifier.5irty oil enters the bowl through a central tube and passes down to the

distribution plate at the bottom and then upwards through the disc stack.

0he forces, generated by the high speed of rotation, cause the water and dirt,

which are heavier than the oil, to move to the outer part of the disc stack and bowl.

0he water and dirt gather in a region between the wall of the bowl and just inside

the edge of the disc stack.

0he clean oil gathers in the region from the centre of the bowl to just inside the

edge of the disc stack.

0he point where the separated oil and water meet is referred to as the interface

0he position of the interface is controlled by using gravity discs with different siAe

central holes or gravity plugs of different length.

0hese determine the effective position of the water outlet.

0he clean oil passes up the outside of the central tube to the outlet to the service

tank.

0he water flows over the disc stack cover plate to the edge of the gravity disc, or

plug, and out through the water outlet.

!he clarifier(>hen a centrifuge is set up without a continuous water discharge it is referred to

as a clarifier.

0he general operating principles are the same as for a purifier except that the

water outlet is blanked off by the top cover of the disc stack.

Instead of separating water and solids from the dirty oil, a clarifier separates solids

from a li?uid mixture

0he solids build up on the inner wall of the bowl and have to be removed regularly.

&s already stated this is achieved through an automatic sludging cycle

%om'inations(

0he factors which affect the performance of the centrifuge are the density

difference, the speed of rotation and the time that the mixture is in the bowl.

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>e usually operate with temperatures as high as possible, but below the boiling

point of water, to maximise the density difference.

>here the capacity of the centrifuges is much greater than the consumption rate of

the machinery then a low flow rate can be used to increase time in the bowl.

0his also allows us to use two centrifuges in series, one as a purifier and one as a

clarifier, which increases the cleaning effect.

0his is the preferred arrangement where possible.

>here capacities of the centrifuges are not much greater than the consumption

rate of the machinery it is possible to use them as purifiers operating in parallel.

0his allows us to have a reduced flow rate through each centrifuge but still

maintain an overall throughput greater than the consumption rate.

Purifier particle removal is important for the removal of catalytic fines from +$.

Purifier manufacturers have performed various tests on particle siAe and purifier

throughput to determine the effects this has on particle removal. elow is a table

showing some interesting results.

!a'le , Purifier Particle :emoval Efficiency

4iAe range of particles

Hmicrons 3:8 8:9 9:6<

Particles in feed oil to

Purifier. 6,8


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the purifierDclarifier in series method when the machines use the gravity disc

method. 0he purifier removes water and some particles and the clarifier removes

even more particles, therefore lowering the fuel oil@s particle count. >ith modern

systems only one machine is re?uired.

4ome basic situations which can cause separators to operate below maximum

efficiency, or not work at all, areE

a. incorrect fuel handling before the centrifuge

'. unstable flow

c. incorrect flow, usually too high a flow

$. unstable temperature

e. incorrect temperature

f. incorrect positioning of the waterDoil interface, inhibiting the correct

flow of oil through all discs, usually caused by incorrect gravity data

andDor choice of an incorrect gravity disc.

g. overfilling of sludge space caused by extended intervals between de:

sludging, or incompatible heavy fuel oils with higher than normal

sludge deposits.

#eferring to the diagram below, the following observations show inefficient or

incorrect separator operation which may be caused by changes in the fuel oil

characteristics.

a separator which breaks the water seal after experiencing

balanced operation may be the result of increased fuel density,

increased viscosity, increased flow rate, or a decrease in

temperature

if the oi'water interface moves towards the axis of the bowl to

give poor fuel separation or water carry over into

Fuel Quality Control on MT ILMA and Cap Felix

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