i am chief engineer on board DP2 AHST which equipped with 2 YANMAR 8N280M-EV main engine.Sb side engine exhaust gases bellows creaked many times.i checked the aliment, bellows instillation direction, exhaust gases temperature and bellows fastening. every thing is OK. This fault happened 3 times in one year although the port side engine running normally without any problems in it's exhaust bellows working condition and engine parameters nearly the same for both engine.
any advise will be highly appreciated.
best regards

check the distance between flange to flange at the manifold and make sure the bellows are the right size (length) . If the flex joints are made to stretch too much after torquing up you may run into bellow failure. Are they after market bellows?. Also after warm up the bolts have to be re-torqued to get the proper tightness. I have seen bellow joints nicked while being torqued down and eventually those bellow are the one that fail prematurely. Rule of thumb - if you stretch the flex joint more than 1/4" after torquing the you are putting more strain on the joints.

very grateful for your concern Mr/ Rodrigger. each time i changed the faulty bellows i used original spare parts which supplied by the engine maker. in the first time this problem happened the maker advised me to use 5mm longer bellows but it failed also.the big question is why the problem only happened in the SB side engine ?
i have great suspension about the engine room ventilation air distribution. is there any standards guide me through this problem.
best regards for all.

Oh, exhaust bellows, they are such a pain in the ass.

Is this a new problem, or right from shipyard? Maybe you just have too much motion, and worn isolator in the exhaust trunking - these are checked by measuring them, they don't last forever. I remember having many problems on one ship, but can't remember what was done to fix it. On some bellows too, there is a particular way to install for proper gas flow, I'm sure you are aware. I will think of it some more, and maybe something will jar loose, in the mean time good luck.

How long is it lasting, where is the bellows cracking?

What state is the insulation in? After changing the bellows a few times it must be in poor condition, unless you have replaced it. Lack of support from the insulation could be leading to fatigue failure of the bellows.

Any alignment changes between hot and cold?

is the engineroom supply fan blowing down this side of the engine, especially if ship in colder areas? Or even the exhaust fan I suppose, it could be causing uneven heating and cooling of the exhaust on that side.

I had a problem once where there was an additional component that was like a "top hat" that went internal in the exhaust bellows to control the tubulence of the gas flow. It was only attached at the hot end, and smoothed the flow of exhaust gas out... It was left out by the previous crew, and it proved to be a vital part.

Also I would check all the uptakes securing arrangement to ensure that there is not undue strain on the exhaust side, and possibly some fractured components such as sliding bolts etc that look fine but are actually flawed and all weight is being landed on the bellows.

Good luck.

Reading this I am suspecting that the exhaust pipe work is not properly supported and the weight is coming onto the bellows, or possible the engine is moving about!
I agre with the bit about the liner. It is very important the the corrugations of the bellows are not directly exposed to the hot exhaust. 1) the exhaust cann burn away the metal, 2) Carbon can be deposited in the creases of the bellows while hot and stop them contracting, leading to failure. Some bellows have a liner welded in, the welded end must be the inlet, the liner being free to expand at the outlet of the bellows, others have a seperate inset, which must be arrangesd the same way.
Install them the wrong wat round and you will trap carbon between the liner and the corrugations.
BP