low load operation - sintef · © man diesel a/s . how slow? 25 knots refers to 100% relative...

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Johnny Eilertsen Service Manager MAN Primeserv Norway

Low load Operation

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MAN B&W service letters that deals with low load operation.

SL07-480

SL08-501

SL09-511

SL11-544

Low load Operation

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How slow? 25 knots refers to 100% relative propulsion power

A reduction of 5 knots, can result in 41% propulsion power requirement.

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Low load Operation

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Why? Extremely volatile fuel prices

Reduced fuel consumption

Reduced emissions

Why not? Increased sailing time

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Low load Operation

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Low load Operation

> 40 %

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SL08-501 – Low load update – Down to 40% load Long term low load operation down to 40% engine load is generally feasible without any engine modification.

Low load Operation

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Low load Operation >40% load

MAN Primeserv recommendations are;

Installation of Retrofit slide type fuel valves.

Monitoring the gas ways for fouling. Be aware of soot formation in

exhaust gas receiver, turbocharger/turbocharger grid and exhaust boiler.

Follow turbocharger manufacturer cleaning recommendations.

Consult boiler manufacturer for recommendations during low load

operation.

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Load up?! From an engine point of view, regular load-ups are not necassary when operating at 40% load and above.

However, boiler manufacturers and some turbocharger manufacturers advise regular load-ups during low load operation as a part of the cleaning prosedure. In such cases we recommend this prosedure:

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Auxiliary blowers Generally, auxiliary blowers are switched off automatically well below 40% engine load. In a few cases the engine rating differs from the standard rating, which may cause the blowers to switch off around 40% load.

If the blowers switch off near the desired load level it might lead to an unfortunate condition. To avoid the blowers to switch on and off the load should be shifted 2% up or down so that the blowers are either continueously running or permanently switched off.

The blower switch off setpoint should be in the range of 0,45 - 0,7 BAR.


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Low load Operation


SL09-511 – Low Load Operation – 10% to 40% Engine Load. Long term low load operation down to 10% engine load is generally possible with appropriate precautions and without major modifications.

As a thumb rule 10% MCR equals to 50% rpm.

Low load Operation 10-40% load


MAN Primeserv basic requirements; Installation of Retrofit slide type fuel valves.

Monitoring of exhaust gas ways for fouling. More frequent inspections and apropriate reaction to these must be accepted.

Further more..

MAN’s Alpha Lube adaptive cylinder lubrication is recommended.

By-pass of the exhaust boiler is recommended.

Frequent inspection of the scavenge air space must be performed.



Load-up?! Engine load up must be minimised. Based on experience we know that frequent load-ups could jeopardize the cylinder condition.

When it is necassary to increase load significantly, after an extended period of low-load running, the below prosedure should be followed:

In addition the MAN Diesel recommendations regarding the load-up program under normal running conditions must be followed. (SL09-503 – only for >80MC)




Auxiliary blowers If the engine is to be operated in the start/stop area of the blowers avoid this by activate the blowers in ”Manual on”.

Basically , the auxiliary blowers are not designed for continuous running, but service experience so far shows reliable performance.

As a safety precaution, it is recommended to have a complete spare auxiliary blower on board. A spare electric motor may be sufficient, but the disassembly of the blower wheel and motor could be troublesome and time consuming due to sticking parts.

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Operating at low speed can create issues, such as: Increased soot formation in exhaust gas boiler and turbocharger, requiring more frequent cleaning. Switching in/out of auxiliary blowers Less or no fresh water generation Unsufficiant steam generation.

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Smoke tube boiler inside, after 7 days below 40% load.

Limited soot deposits.

Low load Operation


•Reduced soot deposit in exhaust ways and boiler.

•Reduced soot deposit on piston crown.

•Improved cylinder condition.

•No dripping from fuel nozzle.

•Less smoke formation.

•Lower Nox, HC, and particle emmission.

•Increased TBO.

Slide fuel valve retrofit

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Conventional fuel valve Sac volume 1690 mm3

Mini-sac valve Sac 520 mm3

Slide-type fuel valve Sac volume 0 mm3

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Thank you!

low load operation - sintef · © man diesel a/s . how slow? 25 knots refers to 100% relative...

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