Economical Engine Operation

8/3/2019 Economical Engine Operation

1/611 Wrtsil 3.12.2010 WPP-000R09CFM401A001L_01en / Turku Training Centre


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It is necessary to maintain effective control over fuel consumption and to ensurethat the amount of fuel oil received is correct and the quality acceptable.

14 Wrtsil 3.12.2010 WPP-000R09CFM401A001L_01en / Turku Training Centre

apply prudent economic principles in the management of this resource.

Normally this means that a minimum amount of fuel should be stored on the

location.

This method requires a continuous and reliable source of fuel.

To avoid stability and incompatibility problems (precipitation of heavy componentsin the fuel), avoid, if possible, blending of fuels from different bunker stations,

unless the fuels are known to be compatible.

Local management shall decide the minimum amount of fuel to have in storage at

any given time for the safe operation of the plant and guidelines shall be set up to

let the operators know exactly when to reorder fuel.


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It is important that the quantity of the shipment is according to the consumptionand the quality of the fuel meets the specifications.


have it analysed before use.

Also check the tanks of the truck for possible water contamination.

This could be done using a water finding paste on a sounding tape, orbetter, by draining off a sample from the bottom of the tanks.

This is particularly important in the case of LFO as the water settles out faster inthis fuel.

Water in HFO may stay suspended longer and may not settle out duringtransportation.


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The importance of the fuel in a engine must never be underestimated and propercare must always be taken when handling it.


maximum viscosity of 55 cSt/100 C (~730 cSt/50 C, ~7200 sec. RI/100 F) and

will operate satisfactorily on blended (intermediate) fuels of lower viscosity as wellas on distillate fuel.

Avoid the use of fuels having a lower viscosity than 2.8 cSt/40 C as such fuelsmay cause a seizure of the fuel injection pump plunger or the fuel nozzle needle.

Blended fuels (residuals and distillate) with a viscosity 47 cSt/100 C (1230cSt/50 C, 65200 sec. RI/100 F) containing 3060 % distillate should,however, be avoided due to the risk of precipitation of heavy components in the

blend with filter clogging and a large amount of centrifuge sludge as aconsequence.

When difficulties with filter clogging are experienced fuel incompatibility canbe tested by the ASTM D 2781 method or similar.


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Fuel characteristics

The plant is designed for operation on fuel with characteristics up to the following


.

HFO 1 stands for heavy fuel oil of normal quality and HFO 2 for heavy fueloil below normal standard quality.

If any of specified fuel properties exceed HFO 1 maximum value, the fuelshould be classified as HFO 2.

If the values are exceeded during the guarantee period, the engineguarantee is not valid.


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Water content

If the water is sweet and very well emulated in the fuel, the effective energy


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in fuel consumption. The combustion will not be affected negatively by even a

substantial amount of water.

If the fuel is contaminated with sea water, the chlorine in the salt will cause

corrosion of the fuel handling system including the injection equipment.

Asphaltene content

High asphaltene content may contribute to deposit formation in the combustion

chamber and in the exhaust system, especially at low loads. A high asphaltenecontent indicates that the fuel may be difficult to ignite and it burns slowly.

If the fuel is unstable, the asphaltenes may precipitate from the fuel and block

filters and/or cause deposits in the fuel system, as well as excessive centrifuge

sludge.

Flash point

A low flash point will not influence the combustion but the fuel can be dangerousto handle and store.

This is especially the case if the pour point is high, and the fuel has to be

heated due to this.

A high vapour pressure (low flash point) can also give cavitation and gas pockets

in the fuel pipes.

Total sediment potential (TSP)

If TSP is high the danger of sediment and sludge formation in the tanks and fuel

handling system increase as well as the probability for filter clogging.

TSP can also be used as a check for compatibility of two different fuels.

If the TSP of the mixture of two different fuels remains low, the fuels arecompatible.


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Sulphur content

The sulphur in the fuel may cause cold corrosion and corrosive wear, especially at


.

Sulphur also contributes to deposit formation in the exhaust system,normally together with vanadium and/or sodium in the form of sulphates.

The deposits can also cause high temperature corrosion.

Ash content

Oxides of vanadium and sodium, mainly sodium vanadyl vanadates, are formedduring combustion, and mix or react with oxides and vanadates of other ashcomponents.

The sticking temperature of the mixture may be such, that a deposit is

formed on a valve, in the exhaust gas system or in the turbo charger. Thedeposit is highly corrosive in the molten state, destroying the protective oxidelayer on exhaust valve and leading to hot corrosion and burned valve.

Deposits and hot corrosion will cause decreased turbo charger efficiency.

Aluminium and silicon oxides can cause severe abrasive wear mainly of the

injection pumps and nozzles, but also of cylinder liners and piston rings.

CCAI-index

The ignition quality of HFO can be roughly determined by calculating the CCAI

(Calculated Carbon Aromaticity Index) from the viscosity and density of a fuel. An increased CCAI value indicates decreased ignition quality.


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Oil changes

An oil sample shall be taken for analysis, and if the result is positive, and the


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changes may be increased in steps of 500 hours.

Oil consumption

Compensate the normal lube oil consumption by adding a maximum of 10 % newoil at a time.

If larger quantities of lube oil are added this may disturb the balance of the

circulating oil and cause a precipitation of insolubles.

Oil top-up for daily consumption should be made at least every 2nd day.

Oil supply Oil should only be purchased from reliable and responsible suppliers.

Lubricating oil is costly and prudent economical principles must guide themanagement of this resource.

Local management must decide which supplier to use and when to re-order.

The time from reordering to delivery must be established and will be the

main factor when calculating the re-ordering point.

The rule of thumb should be that there should never be less oil in stockthan is required for one weeks normal operation plus oil sufficient for one

complete oil change of one operational unit.


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If the oil is delivered in tanker trucks always demand an invoice or other certificatestating the type of oil supplied.


to have it analysed if any doubt about the quality of the oil arises.

However, to find out if the oil also contains an unacceptable amount of water, you

may try to test it by taking a tablespoon full of oil and heat it using a lighter.

In case of heavy water contamination this water will soon start to boil off in anoticeable way.

Compare the new oil with the one already in stock, and if any difference can be

noted it is a good reason for having the oil investigated further before using it inthe engines.


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The list of approved lubricating oils can be found from the Engine instructionmanual.



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Quality control

One of the most important maintenance actions to carry out is the control andurification of the lubricatin oil.


The cost for this is negligible in comparison with the cost for repair and

replacement which may be caused by poor lubricating oil quality.

Oil sample

Take an oil sample in connection of every oil change. In a new installation or afterchange to use of a new lubricating oil brand the oil sample should be taken alsoafter initial 500 hours.

The samples shall be sent to the oil supplier for analysis and based on the resultof the analysis the correct oil change interval can be established.

The oil sample sent to the oil supplier for analysis should contain the followinginformation:

From which plant the sample originates.

Engine identification/number.

Total hours in operation (engine).

Total hours in use (oil).

From where the sample was taken.

Type of fuel oil.

Other information of interest would be:

Separating frequency.

Filter replacement interval.

LO consumption.

Other remarks.


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To evaluate the condition of the tested oil, the following test results should beobserved.


the same type.

Viscosity

The viscosity should not rise more than 25 % above the guidance value at100 C.

Maximum permissible viscosity for an SAE 30 grade oil is 15 cSt at 100 C(140 cSt at 40 C).

Maximum permissible viscosity for an SAE 40 grade oil is 19 cSt at 100 C(212 cSt at 40 C).

Minimum permissible viscosity for an SAE 30 grade oil is 9 cSt at 100 C (70cSt at 40 C).

Minimum permissible viscosity for an SAE 40 grade oil is 11 cSt at 100 C(110 cSt at 40 C).

Flash point

Flash point should not fall more than 50 C below the guidance value. The

lowest permitted flash point (open cup) is 170 C.

Water content

Water content should not exceed 0,3 %. At 0,5 % measures must be taken;either centrifuging or oil change.


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Insolubles

The quantity allowed depends on various factors, and the oil suppliers


.

However n-Pentane insoluble value above 1,5 % calls for attention.

A value above 2 % cannot be accepted for longer periods.


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Analysis of test results

Oil samples, taken at regular intervals and with the test result plotted as a function


,

change interval.

Generally it can be said that changes in the test result gives a better

indication about the condition of the engine than does the actual value itself.

Large and rapid changes indicate abnormal operational conditions in theengine and/or the lubrication system.

A frequent contaminant is engine coolant. This shows up in the analysis as water,

sodium, boron or sludge.

The sodium and boron elements are components of water treatments and

antifreezes.

Lubricating oil analysis indicates the presence in the oil of the various metals usedin the engine.

These metals and their sources are shown in the table.

On a new engine or one that has just been overhauled, higher values maybe expected until the engine has been run in.


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Deposit formations (fouling) are caused by solid contaminants in suspension.

This matter may settle in the system regions where the water flow velocity is


, .

The clean circulating water should be treated with chemicals to keep thefoulants in suspension preventing them from settling out.

Deposits already formed in the system can be removed by treating the water withchemicals to dissolve and disperse the foulant.

The dissolved deposits can then be flushed out of the system and cleantreated water be added.

Fine solids in suspension may be treated with chemicals to form larger, non-adhering particles.

These larger particles can then be flushed out from the system.

Mechanical cleaning of the heat exchanger, etc. can be done by injecting abrasiverubber balls that are caught by screens after having passed through the heatexchanger.


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Scale formations occur when the concentration of salt (normally calciumcarbonate, calcium sulphate, calcium phosphate and magnesium silicate)

becomes too hi h.


The salt may then settle out (precipitate) and form a deposit on the surface

area in contact with the water.

Such scale has a poor heat transfer capacity that may lead to insufficient

cooling of the engines vital parts.

Scale formation can be prevented by removing the scaling mineral from the water,

by keeping the scale forming mineral in solution and by allowing the scale formingmineral to settle out, but chemically altering the scale (using crystal modifiers) toform a removable sludge.

Common methods used to remove scaling minerals are:

Using filters (sand filters).

Softening the water in an ion exchange facility.

Complete demineralisation of the water.

To keep the scale forming minerals in solution or to chemically alter the scale toform sludge, require chemical treatment.

Location and water quality are important factors when using this type oftreatment and an economic comparison is necessary to select the bestsolution.


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Biofouling is the growth and propagation of a living organism that leaves depositson surfaces.


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accelerate corrosion.

Biofouling is normally divided into:

Macro biological fouling:

This type of fouling can be found in low temperature water systems,and is normally caused by mussels, clams, etc., entering the system viathe raw water intake.

Micro biological fouling:

This type of fouling is mainly found in low temperature water systems,

but may also be found in systems with elevated temperature. It iscaused by bacteria, algae and fungi, and normally enters the system viathe make-up water or a cooling tower air intake.

Common methods for protection against biofouling are mechanical treatment,

thermal treatment or chemical treatment.

The mechanical treatment of the make-up water supply normally consists of a

two-stage screening.

The first stage is a rather coarse intake strainer and the second stage a finersuction strainer. The use of thermal treatment is based on the fact that some

organisms are killed by an elevated temperature.

Such thermal back-wash must be performed frequently and is usually not asolution in open recirculation systems.

Chemical treatment is often very effective against biofouling, but a negative factoris the toxic effect it has on the environment.


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In order to prevent corrosion scale deposits or other deposits in closed circulatingwater systems the water must be treated with additives.


possible (max 10 dH), a chloride content of less than 80 mg/l and a pH value

above 7.

The best result will be achieved by using totally desalinated water for

instance from fresh water generator, and additives.

Also note that a sulphate concentration below 150 mg/l is recommended.

A calcium hardness exceeding 2 dH tends to prevent corrosion by forming a

thin layer on the metal surface.

Evaporated water should be compensated by untreated water due to the fact that

if treated water is used as compensation the content of additives will gradually

become too high.

Treated water should be added when compensating leaks or losses.

The chemical treatment of the water in the circulation system should be

performed with caution.

The manufacturers instructions regarding treatment, dosing and control of

the concentration must be followed. When another brand of chemical is

used, or when treatment starts on a previously untreated system, it isnecessary to chemically clean the system.

Follow the instructions for the chemical used as cleaning agent regardingconcentration, temperature and time for treatment. After the cleaning process it

may also be necessary to neutralise the system using an alkaline solution.

After treatment, flush the system with fresh water before adding treated water.

It is recommended to use the Nitrite based chemicals on internal cooling watersystem.


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Economical Engine Operation