4
Introduction The Alpha Lubricator System, Fig. 1, available for all MAN B&W MC/MC-C two-stroke engines, has an algorithm controlling cylinder oil dosage proportio- nal to the sulphur content in the fuel. This algorithm is referred to as Alpha Adaptive Cylinder-oil Control (Alpha ACC). To explore the potential savings with Alpha ACC, a large scale testing programme is in progress on MAN B&W MC/MC-C type engines in service for a number of owners. The aim of the testing programme is to determine the level of savings in cylinder oil consumption when taking advantage of the electronically controlled Alpha Lubricator System. An added benefit is that such savings in cylinder oil consum- ption will reduce the environmental im- pact from operating vessels with the Al- pha Lubricator System. Also more uni- form and optimal cylinder liner wear rates can be expected. The testing programme involves large bore engines for both container vessels (K-MC/MC-C) and for VLCC propulsion (S-MC/MC-C), as well as small and medium bore MC/MC-C engines. In the following, the very promising pre- liminary results from the testing prog- ramme will be described and evaluated. Working Principle The principle of the Alpha ACC appears from Fig. 2. The cylinder oil amount is controlled such that it is proportional to the amount of sulphur entering the cyl- inder with the fuel. The following two criteria determine the control: The cylinder oil dosage shall be pro- portional to the sulphur percentage in the fuel The cylinder oil dosage shall be pro- portional to the engine load (i.e. the amount of fuel entering the cylinders). The implementation of the above two criteria will lead to an optimal cylinder oil dosage, proportional to the amount of sulphur entering the cylinders. The above principle is founded on the observation that the main part of the cylinder liner wear is of a corrosive nature, and the amount of neutralizing alkalinic components needed in the cylinder should therefore be proportional to the amount of sulphur (generating sulphu- rous acids) entering the cylinders. A minimum cylinder oil dosage is set in order to account for other duties of the cylinder oil (securing sufficient oil film, detergency, etc.). Fig. 3 shows control of cylinder oil dos- age proportional to the sulphur percen- tage in the fuel. A minimum dosage 1 Cylinder oil amount Sulphur amount Fig. 2: Cylinder oil amount proportional to sulphur amount entering the cylinders (the basic principle of Alpha ACC) Fig. 1: Alpha Lubricator fitted on a 12K98MC-C main diesel engine Cylinder oil dosage (g/bhph) 1.25 1 0.75 0.5 0.25 0 0 1 2 4 5 6 Sulphur % Fig. 3: Cylinder oil dosage proportional to sulphur percentage in the fuel Alpha Adaptive Cylinder-oil Control Alpha ACC

Alpha Adaptive Cylinder-Oil Control Alpha ACC

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Page 1: Alpha Adaptive Cylinder-Oil Control Alpha ACC

Introduction

The Alpha Lubricator System, Fig. 1,available for all MAN B&W MC/MC-Ctwo-stroke engines, has an algorithmcontrolling cylinder oil dosage proportio-nal to the sulphur content in the fuel. Thisalgorithm is referred to as Alpha AdaptiveCylinder-oil Control (Alpha ACC).

To explore the potential savings withAlpha ACC, a large scale testingprogramme is in progress on MANB&W MC/MC-C type engines in servicefor a number of owners.

The aim of the testing programme is todetermine the level of savings in cylinderoil consumption when taking advantageof the electronically controlled AlphaLubricator System. An added benefit isthat such savings in cylinder oil consum-ption will reduce the environmental im-pact from operating vessels with the Al-pha Lubricator System. Also more uni-form and optimal cylinder liner wear ratescan be expected.

The testing programme involves largebore engines for both container vessels(K-MC/MC-C) and for VLCC propulsion(S-MC/MC-C), as well as small andmedium bore MC/MC-C engines.

In the following, the very promising pre-liminary results from the testing prog-ramme will be described and evaluated.

Working Principle

The principle of the Alpha ACC appearsfrom Fig. 2. The cylinder oil amount iscontrolled such that it is proportional tothe amount of sulphur entering the cyl-inder with the fuel.

The following two criteria determine thecontrol:

• The cylinder oil dosage shall be pro-portional to the sulphur percentagein the fuel

• The cylinder oil dosage shall be pro-portional to the engine load (i.e. theamount of fuel entering the cylinders).

The implementation of the above twocriteria will lead to an optimal cylinderoil dosage, proportional to the amountof sulphur entering the cylinders.

The above principle is founded on theobservation that the main part of thecylinder liner wear is of a corrosive nature,and the amount of neutralizing alkaliniccomponents needed in the cylindershould therefore be proportional to theamount of sulphur (generating sulphu-rous acids) entering the cylinders. Aminimum cylinder oil dosage is set inorder to account for other duties of thecylinder oil (securing sufficient oil film,detergency, etc.).

Fig. 3 shows control of cylinder oil dos-age proportional to the sulphur percen-tage in the fuel. A minimum dosage

1

Cylinder oil amount

Sulphur amount

Fig. 2: Cylinder oil amount proportional tosulphur amount entering the cylinders(the basic principle of Alpha ACC)

Fig. 1: Alpha Lubricator fitted on a 12K98MC-C main diesel engine

Cylinder oil dosage (g/bhph)

1.25

1

0.75

0.5

0.25

0

0 1 2 4 5 6Sulphur %

Fig. 3: Cylinder oil dosage proportional tosulphur percentage in the fuel

Alpha Adaptive Cylinder-oil ControlAlpha ACC

Page 2: Alpha Adaptive Cylinder-Oil Control Alpha ACC

of 0.5 g/bhph is indicated. This mini-mum value is preliminary and, given theefficient lubrication achievable with theAlpha Lubricator System, we expect tobe able to further reduce this minimumvalue in the future.

The control according to Fig. 3 is basedon a standard TBN 70-80 cylinder oil. Foroperation in long periods with fuels with asulphur content below 1%, we recom-mend changing to a cylinder oil with alower TBN (i.e. TBN 40-50 cylinder oils).

The environmental impact is clearlydemonstrated: Owners who wish tooperate on ‘green’ fuel (low-sulphurfuel) will, at the same time, have thepossibility to operate with ‘green’cylinder lubrication.

Fig. 4 describes the control of the cylinderoil dosage proportional to the engineload, together with rpm-proportionaland mep-proportional lubrication. Atpart load, load-proportional cylinder oildosage will provide large cost savingsand also reduce the environmental im-pact from excessive lubrication. Below

25% load, the load-proportional lubrica-tion is stopped, and rpm-proportionallubrication takes over, as seen in Fig. 4.

The above described Alpha ACC is im-plemented with the so-called “ SulphurAlgorithm”, see Fig. 5, in the Alpha Lu-bricator System. In the present versionof the Alpha Lubricator System, thecrew onboard the vessel inputs theso-called “HMI-setting” based on thesulphur percentage of the fuel usedand a conversion table, see Fig. 5.This is done by one input on theHMI-panel of the Alpha LubricatorSystem each time the fuel specifica-tion is changed.

Economic andEnvironmental Advantages

In order to illustrate the advantagesof Alpha ACC, we have chosen, asan example, a vessel from the fleetinvolved in the testing programme.The vessel is a 6,800 teu containership equipped with a 12K90MC engine.The Alpha ACC was implemented onthis vessel in early December 2001.

Since then the vessel has been operatingwith cylinder oil dosage control accordingto Figs. 3 and 4 (the Sulphur Algorithm).

The results from the first five months ofoperation is seen in Fig. 6. The upper-most part of Fig. 6 shows the load varia-tion and the sulphur content in the fuel.

Both the load variation and the variationin sulphur content are typical for this kindof vessel. The middle diagram in Fig. 6shows the total amount of sulphur enter-ing the cylinders with the fuel. On the lowerpart of Fig. 6, four curves are shown forcomparison:

• Typical feed rate (mechanical lubricator),1.2 g/bhph, rpm-proportional control

• Basic feed rate (mechanical lubricator),0.9 g/bhph, rpm-proportional control

• Basic feed rate (Alpha Lubricator System),0.8 g/bhph, mep-proportional control

• Alpha ACC (Sulphur Algorithm),0.25 g/bhph/S%.

2

0 100%

Fuel index

Oil pressure

Engine speed

0 100%

0 100%

Oil pressurelow

PUMP 1

LAMPTEST

PUMP 2

ESC ENTER

PRELUB

rpm

%

bar

Index failure

Mark/trigfailureFeedbackfailureCommonalarm

Svovl %Specific

dosage

% g/bhph

1 0.50 77

1.1 0.50 77

1.2 0.50 77

1.3 0.50 77

1.4 0.50 77

1.5 0.50 77

1.6 0.50 77

1.7 0.50 77

1.8 0.50 77

1.9 0.50 77

2 0.50 77

2.1 0.53 81

2.2 0.55 85

2.3 0.58 88

2.4 0.60 92

2.5 0.63 96

2.6 0.65 100

2.7 0.68 104

2.8 0.70 108

2.9 0.73 112

3 0.75 115

3.1 0.78 119

3.2 0.80 123

3.3 0.83 127

3.4 0.85 131

3.5 0.88 135

3.6 0.90 138

3.7 0.93 142

3.8 0.95 146

3.9 0.98 150

4 1.00 154

4.1 1.03 158

4.2 1.05 162

4.3 1.08 165

4.4 1.10 169

4.5 1.13 173

4.6 1.15 177

4.7 1.18 181

4.8 1.20 185

4.9 1.23 188

5 1.25 192

HMI

setting

Sulphur %Specific

dosage

% g/bhph

1 0.50 77

1.1 0.50 77

1.2 0.50 77

1.3 0.50 77

1.4 0.50 77

1.5 0.50 77

1.6 0.50 77

1.7 0.50 77

1.8 0.50 77

1.9 0.50 77

2 0.50 77

2.1 0.53 81

2.2 0.55 85

2.3 0.58 88

2.4 0.60 92

2.5 0.63 96

2.6 0.65 100

2.7 0.68 104

2.8 0.70 108

2.9 0.73 112

3 0.75 115

3.1 0.78 119

3.2 0.80 123

3.3 0.83 127

3.4 0.85 131

3.5 0.88 135

3.6 0.90 138

3.7 0.93 142

3.8 0.95 146

3.9 0.98 150

4 1.00 154

4.1 1.03 158

4.2 1.05 162

4.3 1.08 165

4.4 1.10 169

4.5 1.13 173

4.6 1.15 177

4.7 1.18 181

4.8 1.20 185

4.9 1.23 188

5 1.25 192

HMI

setting

oC

deg

min

Fig. 5: “The Sulphur Algorithm” in the Alpha Lubricator System

0

20

40

60

80

100

0 10 20 30 40 50 60 70 80 90 100

Load (%)

R rpm proportional (%)

Mmep proportional (%)

Load proportional (%)

Typical case: 74,640 bhp x 24h,x 1.2g/bhph x 0.91 = 1956 kg/24h

Alpha ACC: 74,640 bhp x 24hx 0.75g/bhph x 0.75 = 1008 kg/24h

Example,12K90MC:

Load (%): 75

S %: 3.0

Part load dosage (% of full load dosage)

Fig. 4: Load-dependency of cylinder oil dosage. Alpha ACC usesload-proportional cylinder oil dosage

Page 3: Alpha Adaptive Cylinder-Oil Control Alpha ACC

3

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

Yearly cylinder oil expense (USD)

0.9 g/bhph,rpm-control

Basic feed-rate(mechanicallubricator)

Alpha ACC(Alpha lubricator)0.25 g/bhph/S%,

Basic feed-rate(Alpha lubricator)

0.8 g/bhph,mep-control

Typical feed-rate(mechanicallubricator)

1.2 g/bhph,rpm-control

Cylinder oil price: 1 USD/kgYearly operating hours: 7,100

Fig. 7: Yearly cylinder oil expenses with various cylinder lubricationprinciples

0

0.8

0.2

0.4

0.6

1

0 1,000 3,000 5,000 7,000 9,000 11,000

Mechanical lubricator, rpm-proportional controlLiner wear (mm/1000h)

Alpha adaptive control

Running hours

Fig. 9: Cylinder liner wear, comparison between wear with tradi-tional lubrication and Alpha ACC

40

60

80

100

1,5

1,9

2,3

2,7

3,1Load Sulphur

1,000

3,000

5,000

0

500

1,000

1,500

2,000

25/12-01 03/02-02 15/03-02 24/04-02

1- Typical feed-rate (mechanical l2 -

ubricator), 1.2 g/bhph, rpm-controlBasic feed-rate (mechanical lubricator), 0.9 g/bhph, rpm-control

3 - Basic feed-rate (Alpha lubricator system), 0.8 g/bhph, mep-control4 - Alpha ACC: 0.25 g/bhph/S%.

Load (%)

Daily consumption (litre/24h)

Sulphur (kg/24h)

Sulphur %

05/12-01 14/01-02 23/02-02 04/04-02

2,500

1

2

34

Fig. 6: Typical operating profile for a large container vesselequipped with 12K90MC

Oil

film in

0.6

0.8

0.2

0.4

1

0

0.4

1.2

0

0.8

1.6

0.48

0.21

0.13

0.48

0.00 mm/1000h0.000.060.04

Liner wear (mm)

Liner wear (mm/1000h)*

0 1,000 3,000 5,000 7,000 9,000 11,000

From detailed wear-study of 12K90MCengine equipped with mechanical lubricator

*: Judgement made based on Fe-content in drain oil samples

Running hours

Running hours

1,000 3,000 5,000 7,000 9,000 11,000

0

Fig. 8: Detailed wear study on a 12K90MC equipped withmechanical lubricators

Page 4: Alpha Adaptive Cylinder-Oil Control Alpha ACC

As can be seen, very significant savings onthe daily consumption of cylinder oil wereachieved with the Alpha ACC during thefive-month period. These savings willhave very significant economic impli-cations, see Fig. 7, with annual savingsof 340,000 USD on cylinder oil.

In addition, environmental impact inthis case goes hand in hand with theeconomic advantages.

Naturally, the above savings on cylinderoil must be obtained while maintainingacceptable cylinder liner wear figures.

Previous studies into the nature of cyl-inder liner wear on a similar 12K90MCengine have shown that the major partof liner wear takes place during shortintervals where a low cylinder oil feedrate (due to high load) and a high sulphurpercentage are combined.

Fig. 8 shows the results registered on a12K90MC engine with mechanicallubricator (0.65 g/bhph) with rpm-propor-tional control. These results were re-vealed through very frequent cylinderliner wear measurements and evenmore frequent drain oil sample analyses.Naturally, the wear- peaks can beavoided by increasing the cylinder oildosage. However, such a simple in-crease will increase the expenses on

cylinder oil dramatically and, furthermore,it will increase the risk of scuffing duringperiods of operating at part load and/orwith low-sulphur fuel (’bore polish’).

With Alpha ACC, such risks are elimi-nated, and it is expected that cylinderliner wear will become stable and pre-dictable over time and low on average,Fig. 9.

The first cylinder wear measurementstaken on the 12K90MC equipped withAlpha ACC indicate that liner wear isvery low, even with the very low cylin-der oil consumption, Fig. 10.

Conclusion

Alpha ACC is currently being tested ina large-scale in-service test on a widerange of different MC/MC-C engines.The preliminary test results are verypromising with respect to savings oncylinder oil, impact on, in particular,particle emissions and combustionchamber wear figures.

Alpha ACC can be implemented for allMC/MC-C engines equipped with theAlpha Lubricator System.

As a retrofit on vessels in service, theAlpha Lubricator System with AlphaACC will have a payback period of lessthan two years on most types ofMC/MC-C engines. An example isgiven in Fig.11.

4

Oil film in the

high

pressure areas of the

6,800 TEU, 12K90MC, Alpha ACC, cylinder liner wear

0.000.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0 1,000 5,000 7,000 9,000 11,000

Running hours

Cyl 1Cyl 2Cyl 3Cyl 10Cyl 11Cyl 12

Alpha ACCintroduced

0.05 mm/1000h

Absolute max wear (mm)

3,000

Fig. 10: Cylinder liner wear before and after introduction of Alpha ACC

MAN B&W Diesel A/STeglholmsgade 41DK-2450 Copenhagen SV, DenmarkTelephone: +45 33 85 11 00Telex: 16592 manbw dkTelefax: +45 33 85 10 30

[email protected]

Engine type : 6S70MC

Saving in USD 84,333 USD

Total price for Alpha lubricator system 113,960 USDPay backtime 1.35 Years

Layout point: SMCR 22,920 bhpLoad point NCR = 90,0% of SMCR 20,628 bhpFuel oil sulphur content 3 %Cylinder lubricating oil consumptionwith mechanical lubricators 1.20g/bhphCylinder lubricating oil consumptionwith Alpha lubricators 0.75 g/bhphRunning hours per year 7,000 hoursLubricating oil price 100 Cent/litreLub. oil consumption with lubricators 186 tonLub. oil consumption with Alpha lubricators 108 tonSaving in cylinder lub. oil consumption 78 tonSaving in cylinder lub. oil consumption 84,333 litres

Exchange rate 7.55 DKK/USDPrice for Alpha lubricator system 641,400 DKKPrice for supervision during installation 89,000 DKKPrice for fitter’s assistance 130,000 DKKTotal price for Alpha lubricator system 860,400 DKK

mechanical

Fig. 11: Retrofit of Alpha Lubricator System with Alpha ACCon 6S70MC

Copyright ©MAN B&W Diesel A/SReproduction permittedprovided source is given.

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

September 2002P.395-02.09