Fuel Change-over
Changing fuel from DO to
HFO
A fuel change-over from DO to HFO can be performed when the engine
has been put on load and the normal operating temperatures have been reached.
1. Start up the HFO supply
system, if not already in operation.
1.1 Check that the tank
heating and the trace heating are activated.
1.2 Open the inlet and
outlet valves of the HFO tanks as required.
1.3 Start the fuel
separation and transfer system.
1.4 Check the level in the
HFO day tank. Also check that the fuel temperature in the tank is correct.
1.5 Start the HFO feeder.
2. Check that the trace
heating in the fuel circulation system is activated.
3. Check that all valves in the fuel circulation system are in the
correct positions. Make sure that the fuel heater is not bypassed.
4. Push the HFO selection button on the control panel or give a
fuel change-over. The fuel selection valve turns to the HFO position.
5. If
no engines are running on DO, the DO feeder may be stopped.
Fuel change over valve |
Fuel change over valve |
Changing fuel from HFO to
DO
A fuel change-over from HFO to DO is normally performed when the
engine is to be shut down and the fuel system should be flushed with DO.
1. Start the LFO supply
system, if not already in operation.
1.1 Check the level in the DO
tanks.
1.2 Check that all valves
are in the correct positions. The outlet valves of the tanks must be open.
1.3 Start the DO transfer
pump.
1.4 Start the DO feeder.
2. Push the DO selection button on the control panel or give a
fuel change-over order. The fuel selection valve turns to the DO position.
3. Check that the valves by the return fuel cooler are in the
correct positions. Also make sure that the cooling water circuit of the heat
exchanger is properly filled and vented. During prolonged operation on DO, the
fuel cooler must be in operation to prevent overheating.
4. If no engines are running on HFO, the HFO feeder may be
stopped. The fuel separators may be kept in operation as required, in order to
fill the HFO day tank with treated fuel. Make sure that the trace heating if
activated if the circulation is stopped in a system filled with HFO.
Piston rings are to be diagnosed at regular intervals on the basis of the wear pattern. Piston rings have to be replaced after they have been use for time periods given in the maintenance schedule. Replacement will also be necessary if interim checking reveals damage to running surface or excessive clearances.
Different Piston Rings:
The rings being in use are compression rings with chromium-plated, Plasma-coated or (the most recent solution) chromium/ceramic-coated running surfaces, and chromium-plated oil scraper rings.
Different Piston Rings:
The rings being in use are compression rings with chromium-plated, Plasma-coated or (the most recent solution) chromium/ceramic-coated running surfaces, and chromium-plated oil scraper rings.
Piston
rings for MAN B&W 9L 58/64
|
||
Compressor Ring
|
Running Surface
|
|
Groove 1
|
Packing ring
|
Plasma-coated
|
Groove 2
|
Tapper ring
|
Chromium-coated
|
Groove 3
|
Tapper ring
|
chromium-coated
|
Oil scraper ring
|
||
Groove 4
|
Oil scraper ring
|
chromium-coated
|
Wear appearance of
plasma-coated, chrome-plated or chromium/ceramic-coated piston rings
Due to its shape, the running face of new compression rings
does not have contact across its full width but only the width of the actual
contact surface A. With the progress of wear, the actual contact surface width
will increase.
Figure 1. Running face of plasma-coated and
chrome-plated piston rings (time in use > 1000 hrs)
Figure 2. System of cracks on chromium/ceramic-coated piston rings
(time in use approx. > 8000 hrs)
At the end of the useful life, the actual contact surface
extends up to the chamfers or radii of the ring sides, please see Figure 3.
Figure 3. Piston ring of good running pattern at the end of the useful
life.
The chamfers or radii are still distinctly visible on the
piston ring shown in Figure 3. Coated compression rings have to be replaced
when the actual contact surface extends over the entire piston ring width, i.e.
when the chamfers or radii are hardly visible any more. In this condition, the
residual thickness of the coating will not safely endure the subsequent
maintenance interval.
Burns (C) produce local discoloration of the piston ring
face. Such rings have to be replaced. (See Figure 4).
Figure 4. Piston ring with burns on the face
Coated compression rings and oil scraper rings have also to
be replaced if the coating has worn through at one spot.
Figure 5 shows a chrome-plated compression ring. Turn
chromium layer has completely worn spot wise at (D).
Broken-off particles or cracks in the coating of a piston
ring also call for its replace.
Figure 6. Piston ring with broken-off particles in the face
Figure 6 shows a plasma-coated compression ring. Parts of
the coating have broken off at (E).
Chromium/ceramic-coated compression rings have to be
replaced when the continuous, micro-cracked surface has decayed to a crazed crack
appearance. The cracks will then have extended down to the base material, which
involves the danger of particles breaking away.
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