The cylinder lube oil consumption rep-resents a large expenditure for an en-gine operating with the nominal guidingfeed rate and, especially for the largebore engines, even a 0.1 g/bhph re-duction in the cylinder oil dosage repre-sents a significant yearly saving for theowner. Cylinder lubrication is thereforean important development theme withthe aim of reducing the cylinder lube oildosage while maintaining a satisfactorypiston ring/liner wear rate and main-taining or improving the time betweenoverhauls. Reduced lube oil consump-tion also has a positive impact on theenvironment as emissions will be lower.

The cylinder oil must be injected intothe cylinder at the exact position andtime where the effect is optimal, which

is not always possible with the conven-tional lubricators of today. MAN B&WDiesel A/S therefore initiated the devel-opment of the new electronic system,the so-called “Alpha Lubrication Sys-tem” shown in Fig. 1.

The development work for the newsystem was started in 1997, and theprototype entered service on an MANB&W type 7S35MC engine in 1998.Since then the system has beenfine-tuned on MAN B&W’s 4T50MX re-search engine, and service tests wereextended to cover several K90MC en-gines. The first large bore engine withthe new lubricator fitted as standard, a12K90MC engine, was tested in Koreain September 1999 with very satisfac-tory results, and the system has now

been in service on a number of enginesfor up to 20,000 hours, with good results.

The system is now standard on allMAN B&W two-stroke engines with adiameter bigger than 600 mm and is anoption on the smaller engines. The sys-tem has been ordered for more than100 engines, and 30 sets are in service.

The new lubricating system is based onthe principle of injecting a specific vol-ume of oil into the cylinder, via a num-ber of injectors, for every four (or everyfive, six, etc.) revolutions. Furthermore,the precise timing ensures that all cylin-der oil is delivered directly onto the pis-ton ring pack where it is needed. Thiscan be seen in Fig. 2, which shows thepressure measured in the oil injector

1

To othercylinders

Cylinderliner

Cylinderliner

Accumu-lator

Lubricator Lubricator

Accumu-lator

Lubricator

Cylinder oilservice tank

Pump stationwith

stand-by pumps

Master control unit and backup control unit

HMI panel

Lubricator

To othercylinders

To othercylinders

Solenoidvalve

Solenoidvalve

Solenoidvalve

Solenoidvalve

Feed-backsensor

Feed-backsensor

Feed-backsensor

Tachosignal

Indexsignal

Alarmsystem

Slow-downsystem

Cylinder lub.oil pipes

Electricalconnections

Fig. 1: Principle of Alpha Lubricator System

Lubricator System for Cutting the CylinderOil Bill and Reducing Emissions onMAN B&W Two-Stroke Engines

during a cycle with lube oil injection aswell as during a cycle without lube oilinjection. The passage of the four pis-ton rings is clearly seen in the pressuresignal for the cycle without lube oil in-jection, and the precision of the new lu-bricator is obvious.

The lubricator itself, Fig. 3, has a smallpiston for each lubricator quill in thecylinder liner, and the power for injectingthe oil comes from the system pressure,supplied by a pump station. A commonrail system is used on the driving side,but the injection side has a high-pressurepositive displacement system, thus givingequal amounts to each quill and provi-ding the best possible safety marginagainst clogging of single lubricator quills.

2

903010

0

80200 5040 7060 100 [ms]

10

15

5Oil quill pressure

Lube oilinjection pressure

20[Bar]

Fig. 2: Injection pattern for Alpha Lubricator System

P

A

T A TP

Solenoidvalve

Capacitive feedbacksensor for control of

piston movement

Cylinder lubeoil outlet

Outletsfor cylinder linerlube oil points

Signal for lubricationfrom control unit

Spacerfor basic setting of

pump strokeAdjusting screw Actuator piston

Injection plungers

45 bar cylinderlube oil inlet

Fig. 3: Alpha Lubricator

For the large bore engines, Fig. 4, eachcylinder has two lubricators (each serv-ing five lube oil quills), while the smallbore engines, Fig. 5, (with fewer lubeoil quills per cylinder) are served by onelubricator per cylinder. The pump stationincludes two pumps (one operating,the other on stand-by with automaticstart up).

The computer unit comprises a maincomputer, controlling the normal oper-ation, a switch-over unit and a (simple)back-up unit. The injection function iscontrolled by the computer sendingan on/off signal to a solenoid valve. A

shaft encoder (which can be sharedwith the PMI system, or timing systemon the Intelligent Engine) supplies thenecessary timing signal.

The amount of oil injected can be ad-justed automatically or manually asrequired, e.g. at load changes, start/stop,at reduced engine load (different modesare available), sulphur % in the fuel,temperature level on liner surface, vari-ation in cylinder oil BN, etc. Pre-lubricationbefore start can be made manually or bea sequence in the bridge manoeuvringsystem.

Both for marine engines and for enginesfor power generation purposes, verylow feed rates have been demonstrated,with oil consumption down to 0.5 g/bhph.Further reductions in wear rates as wellas in feed rates can be obtained by uti-lising fuel-oil-sulphur-dependent lubri-cation, a principle for which MAN B&Whas applied for a patent.

3

Fig. 4: 12K98MC-C with Alpha Lubricator

4

Fig. 5: 7S50MC-C with Alpha Lubricator

MAN B&W Diesel A/STeglholmsgade 41

DK-2450 Copenhagen SVTelephone: +45 33 85 11 00Telex: 16592 manbw dkTelefax: +45 33 85 10 30manbw@manbw.dkwww.manbw.dk

Copyright ©MAN B&W Diesel A/S

Reproduction permittedprovided source is given.

MAN B&W Diesel A/SReg. No: 39 66 13 14

August 2001P.384-01.08