主機掃氣箱著火的案例

During inspection of scavenge manifold on a MAN B&W12K98MC engine (20XX): Normal condition was found on 9 units: 

下面是主機9缸掃氣箱檢查的照片：

 Un-burnt was fuel found in one unit: the reason was a faulty fuel injector.

主機一個缸不發(fā)火：原因是主機噴油器故障。

A simple “check” across the scavenge air manifold is enough to judge if you have major fuel injection problem in any unit.

我們一次普通的掃氣箱檢查，能發(fā)現(xiàn)主機任意缸的噴油器問題，例如滴漏。

In this case, investigation revealed the following problem:

發(fā)生上面的情況，與噴油器的固定銷有關(guān)：

1. The spindle-guide and atomizer are handledas one assembly (slide type fuel valves).

2. The direction of fuel spray is fixed bythe position of atomizer and spindle-guide assembly.

3. This position is decided by a small pinwelded inside the atomizer casing.

4. While assembling, if the spindle-guide isdropped inside the casing too fast, it might break this pin.

5. Engineer must always check that theatomizer is fitted correctly (it should not be able to rotate).

In this case, the pin was broken, the fuel injector was assembled wrongly, and fitted on the engine. It was spraying fuel on the liner!

In such condition, cylinder liner can crack withina few days.

Ifa locating pin is found broken, please replace it using the followingprocedure:

Grindingabout 1-2mm deep will show the exact location of pin

Mark the location, then use a pin-punch of 4mmdiameter to drive out the broken pin

Old damaged pin after removal   

Newpin ready to fit

If required, dress the hole with a round needlefile   

                 Tapthe new pin in place

Verify if the spindle-guide and atomizer can beassembled correctly.

 Then, weld around the pin (use a Mild Steel weldingrod 2.5mm). The welding will keep the pin in place, and prevent fuel leakage.

Finally, grind the surface smooth. (This can bedone manually or on a lathe)

                                                            Remember

1. Fuel injector is the most important part of   the engine.

2. Its removal, overhaul, assembly, and mounting     must be supervised by engineer who is familiar with the equipment, and has     studied the maintenance procedure.

3. During overhaul/assembly, do not drop the     spindle guide vertically inside the casing – this will break the locating     pin soon. Slide it inside slowly, holding the casing horizontal, causing     minimum impact.

4. Responsible engineer must do these final     checks at assembly:

a)    Injection holes point towards the center of cylinder.

b)    Injector landing surface is clean and lapped smooth.

c)    Spring packs are compressed correctly, not over-tightened.

要點：1.大家裝配主機噴油器時，一定要檢查噴油器內(nèi)的固定銷的狀況。

            2.對于MAN B&W的主機噴油器，油嘴的方向是固定的（油嘴噴油不能噴向氣缸套，易引起掃氣箱著火）。

            3.主機掃氣箱檢查時，注意檢查掃氣箱的放殘是否通暢。

            4.主機掃氣箱，應(yīng)定期清潔。如果主機低速（SSS）時間長，應(yīng)縮短清潔的間隔。

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