HITACHI MAN-B&W No. ：HZSD-B0602 DIESEL ENGINE SERVICE DATA DATE ：24-8-2006

Cylinder Lubrication Guidelines for Engines with Mechanical Lubricator ENGINE TYPE: L/K-MC/MCC, S-MC/MCC

1. Purpose of cylinder lubrication

Cylinder lubrication has following purposes and each of them necessarily does not require the same feed rate.

1) To create a hydrodynamic oil film separating piston rings from the liner

The oil amount needed to create an oil film is more or less independent of the fuel oil being used. Measurements of the oil film have also revealed that when the feed rate for optimum oil film is reached, no further increase of the oil film is obtained from an increase of the feed rate.

2) To clean the piston rings, ring lands and grooves

Cleaning of piston rings, ring lands and grooves is essential, and relies on the detergency properties of the cylinder oil.

3) To control corrosion, i.e. control the neutralization of sulphuric acid

The combustion process creates highly corrosive sulphuric acids depending on the sulphur in the fuel. It has therefore been of paramount importance to design the combustion chamber and the cylinder lube oil so as to create the optimum balance of corrosion.

2. Cylinder lubrication Guidelines

In 1994, 10 years after the introduction of the MC engine, we adjusted the cylinder lubrication guidelines, as service experience, especially from the superlong stroke “S” engines, had shown benefits of increased oil dosages. The results was differentiated and had been introduced in the M/E instruction book (PLATE 70710); recommending a basic feed rate of 1.0 g/bhph for “L” and “K” engines, and 1.2 g/bhph for the “S” engines.

REMARKS：

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Now, development and experiences after issuing this recommendation together with today’s worldwide lack of lube oil supply and shipowner’s request has brought us in a position where we can correct the guidelines so as to bring even more benefit to the owners. Cylinder lubrication has a direct influence on the operational costs of engines. The cost of the cylinder lube oil itself is one of the biggest contributions to the total operating costs (next to the fuel cost), while the lubrication rate has a major influence on the cylinder condition, i.e. condition of piston, piston ring and cylinder liner and thus, to a certain extent, on the overhauling schedules and overhauling costs. Therefore, feed rate and overhaul predictability and cost are interrelated factors that need to be kept in balance. Recently we have seen, that excessive lubrication may lead to deposit build-up on the pistons, which may disturb the cylinder condition. Therefore, excessive cylinder lubrication should be limited to situations such as the very first breaking-in, where the oil is used to flush away the wear particles formed. Otherwise, increased lubrication should only take place in cases of a very poor cylinder condition, where heavy blow-by or scuffing takes place and constantly destroys the oil film on the liner. Judging from the above background and MAN B&W information, we consider reduction is possible up to approx. 0.9 g/bhph for “L” and “K” engines and 1.1 g/bhph for “S” engines is as shown in the table 1. In any case, reducing the feed rate should always be adjusted so as to keep normal cylinder condition based on careful evaluation of the wear measurement results at piston overhaul and actual cylinder condition with regular scavenge port inspections. The cylinder oil feed rate shown in table 1 is guideline value and converted value to MCR for engines equipped with mechanical cylinder lubricator. This is prescribed by the feed rate at MCR, where feed rate becomes minimum, because feed rate is proportional to M/E rpm, and M/E output is proportional to cubed M/E rpm for fixed pitch propeller.

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In view of the above, cylinder oil feed rate at part load is bigger than the value based on MCR conversion. If main engine load does not exceed CSR or cylinder oil feed rate is checked at every load change, it is no problem to apply the guideline value shown in table 1 to actual main engine output. In this way, this procedure can be one of effective measures against rising cost of cylinder oil.

3. Cylinder lubrication dosages at use of low sulphur fuels

1) Sulphur is one of the chemical components with such large variations, from below 1%, typically in fuels originating from South America and China and up to 4% in fuels originating from the Middle East and Asia. Sulphur contents higher than 4% are very rare, in fact about 3% of all bunkers show sulphur content above 4%. In addition to the geographical variations to the sulphur content in fuels, comes the environmentally based selection, i.e. the special demands for low sulphur fuel operation in restricted areas, (SECA: Regulated not exceeding 1.5% sulphur content) in order to reduce SOx emission.

2) Although fuel sulphur levels above 4% are rather rare,

running on high sulphur fuels counted for a major part of cylinder wear in the past. Therefore, countermeasures in way of increasing the cylinder oil dosages are necessary and highly economical attractive, to prevent excessive wear associated with such fuels. However, on sulphur fuels below 1.5% sulphur with use of high BN cylinder oil (of BN 70), the engine will be overdosed with base additives according to the above countermeasure. This may lead to cylinder condition problems and scuffing is caused at worst case. Such overdosing of alkali additives should be limited, preferably to 1-2 week, and preferably limited to temporarily running on low sulphur fuels in restricted areas.

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3) In order to avoid excessive accumulation of Ca content due

to alkali additives, it is possible to change to use lower BN cylinder oil such as 40BN or 50BN oil. However, please pay attention to the following in this case:

(1) It can be difficult to take necessary action depending

on bunker location in case sulphur amount is changed.

(2) Cylinder oil tank has to be double tank system.

(3) Low BN oil could be lack of detergency

(4) It is necessary to increase cylinder oil feed rate in comparison with BN 70 oil.

4) Judging from the above at use of low sulphur fuels with

less than 1.5% for a long period, we recommend to reduce cylinder oil feed rate with use of the presently used BN 70 cylinder oil by paying attention to cylinder condition by stepwise reducing (Reduction/time should be less than 0.05 g/bhph). It varies based on cylinder condition, but we consider reduction is possible up to approx. 0.7-0.6 g/bhph in actual (MCR conversion).

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Table 1 Guiding Cylinder Oil Feed Rates

Basic setting (ref. To MCR load) :

L/K-MC/MC-C : 0.9 g/bhph S-MC/MC-C : 1.1 g/bhph

Minimum feed rate (ref. To MCR load) :

L/K-MC/MC-C : 0.6 g/bhph S-MC/MC-C : 0.7 g/bhph

Maximum recommendable feed rate during normal operation (ref. To MCR load) :

L/K-MC/MC-C : 1.35 g/bhph S-MC/MC-C : 1.65 g/bhph

Feed rate : Basic feed rate +100%

Duration : +100% for 15 hours (Fig. 1)

Breaking-in new or reconditioned liners and rings (Initial running-in)

Load : Stepwise increase to max. load over 15 hours (Fig. 2)

Running-in feed rate, new liners and rings:

Basic setting +50%, to be reduced in two step of 25% each after an interval of 250 hours. (Fig. 1)

Breaking-in new rings in already run-in liners:

Stepwise load increase to max. load over 5 hours. Lube oil service feed rate +50% for 24 hrs.

Service feed rate:

The “Service feed rate”, i.e. the feed rate between the “Basic setting” and the “Minimum feed rate”, is to be based on observations of the actual condition (scavenge port inspections and overhauling reports). Lowering the feed rate may be done in steps of maximum 0.05 g/bhph. (Fig. 1)

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ランニングイン時の注油率

シリ

ンダ

注油

量（

基準

値比

率）

基準値

最小注油率

一般的な注油率 推奨最大注油率

運転時間

(L/K-MC/MC-C／S-MC/MC-C)g/bhph

(1.8 / 2.2) g/bhph

ブレーキングイン時（15 時間）の注油率：新品または整備ライナ，新品リング Breaking-in (15 hours) : New or reconditioned liners and new piston rings

(1.35 / 1.65)

(0.9 / 1.1)

(0.6 / 0.7)

図２ ブレーキングイン時の負荷上昇（新品ライナまたは整備ライナ及び新品リングの初期なじみ運転）

Fig. 2 Breaking-in load programme new or reconditioned liners and new piston rings

回転

数（

船速

）

時 間

図１ なじみ運転時のシリンダ注油率

Fig. 1 Cylinder oil feed rate during running-in

基準値 Basic setting