Starting-up after Out of Service Periods

08028-0D/H5250/94.08.12

The following enumerate checks are to be made immediately after starting, during load increase, and during normal running.

In the following it is assumed that the engine has been out of service for some time, for instance due to repairs and that checks during out of service periods have been carried out as described in the previous chapter.

When starting after such an out-of-service period, the following checks must be made in the stated order in addition to normal surveillance and recording.

1.To be Checked immediately after Starting:

1.1. Check that the turbocharger is running.

1.2. Check that the lubricating oil pressure is in order.

1.3. Check that all cylinders are firing (see exhaust temperatures).

1.4. Check that everyting is normal for the engine speed, fuel oil, cooling water and system oil.

1.5. Check by simulation of the overspeed shutdown device that the engine stops. The overspeed setting should be according to " Set Points and Operation Data " section 500.

2. To be Checked during Starting-up, but only if Required after Repairs or Alterations:

2.1. If the condition of the machinery is not wellknown, especially after repairs or alterations, the "feel-over sequence" should always be followed, i.e.:

After 5-15 and 30 minutes' idle running, open the crankcase and the camshaft housing and perform feel-over on the surfaces of all moving parts where friction may arise and cause undue heating.

Feel: Main, crankpin, (alternator), and camshaft bearings, piston pins, cylinder liners, roller guides and gear wheels.

After the last feel-over, repeat check 4 page 501.05, see also Ignition in Crankcase page 503.04 in section 503.

After repair or renewal of cylinder liners, piston rings or bearings, allowance must be made for a runningin period, i.e. the engine load should be increased gradually as indicated in the tables below. The engine output is determined on the basis of the fuel index and the load on the electric switchboard. The turbocharger speed gives some indication of the engine output, but is not directly proportional to the output throughout the service period.

Begin the starting-up sequence at a reduced engine speed, e.g. 400 rpm, until it can be known for certain that there are no hot spots in the engine. Then, increase the speed to the normal rpm and connect to the switchboard and put on load.

The load increase during the starting-up sequence may, for instance, be:

25 % load for 2 hours

50 % load for 2 hours

75 % load for 2 hours

100 % load may be put on.

The pump index indicated in the tables has been given as a percentage of the index at full load. To enable the index to be read directly off the fuel pumps, the following formula can be employed:

Following the alteration of the pump index of the one or two cylinders concerned it must be checked that when in STOP position the governor is able to move all the fuel pumps to an average pump index not exceeding 2 or 3.

After completing the starting-up sequence, make sure that all fuel pumps are set at the same index and that the governor can cause all fuel pumps to move to "0" index.

Part load/low load operation

In certain ship operation situations the diesel-gen- erator sets are sometimes exposed to part load/low load operation.

During manoeuvring all diesel-generator sets are often started up for safety reasons, resulting in low load conditions for all sets.

During harbour stay even one diesel-generator running could be lowloaded when hotel purposes are the only electricity consumers.

At part load/low load it is important to maintain constant media temperatures, i.e. for cooling water, lubricating oil and fuel oil, in order to ensure adequate combustion chamber temperature and thus complete combustion.

At loads lower than 20% MCR there is risk of timedependant retardation of the engine performance condition due to fouling of gasand air channels, combustion chambers and the turbocharger.

General

HFO-operation at loads lower than 20% MCR should therefore only take place within certain time limitations according to the curves.

After a certain period of HFO-operation at a load lower than 20% MCR, a change to MDO should take place in order to prevent further retardation of the engine performance condition, or the engine load should over a period of 15 minutes be raised to 70% MCR and maintained here for a certain period of time in order to burn off the carbon deposits, thus reestablishing adequate performance condition. After such "cleanburning period" low-load operation on HFO can be continued.

However the operator must be aware of the fact that fouwling in the air inlet channels, if any, will not be cleaned with high load running. Extensive low-load running can therefore result in necessity off manual cleaning of the inlet channels.

If special application conditions demand continuous HFO-operation at loads lower than 20% MCR. and occasionally performed "clean-burning" periods are inconvenient or impossible, special equipment and arrangements must be established.

08028-0D\H5250\94.08.12

Description

At land-based power stations the diesel generator is often connected to a common eletrical grid with more than one power producer.

Further the diesel engine is often small compared to the rest of the grid. Under these circumstances the diesel engine cannot control the frequency of the grid, because the other producers are dominating.

If the diesel engine is delivering full 100% power at lower speed (lower frequency), this is equal to overload on the engine. Thus, if the engine is designed for 50 Hz at 750 rpm and the actual running conditions are 100%, 45 Hz (675 rpm), this corresponds to 10% overload.

Running the diesel engine at overload condition for a long period is not recommendable, it will damage the engine and is therefore not acceptable. Such operating will immediately interrupt all guarantee obligations on the engine from MAN B&W, Holeby.

General

Therefore it is advisable to reduce the allowable max output of the diesel generator, in case of lower frequency/speed.

Maximum output should be lowered with the same percentage as the frequency/speed drop.

If the engine is controlled by an automatic power management system, the program of the system should take care of this output reduction.

In case of no automatic power management, the output reduction must be performed manually by the operator.

Furthermore, it is not advisable to operate the alternator at frequency lower than 6% under nominel frequency.

The alternator over/under frequency protection is normally:

fN ± 6%, 5 sec delay

Below is illustrated a power curve for 50/60 Hz engines.