Diesel Engine Backfire

[NeutralPlus]

thread403-160410

One of our engines has backfired violently and dislocated [blew out] part of the exhaust piping. There was no pressure relief designed nor built into the exhaust line behind the silencer. The exhaust line is double-walled insulated stainless piping - 20" inside and 24" outside. The exhaust runs 20' horizontal then turns vertical for 50'. The diesel engine generator is 2000kW. There is no jacket heater nor an aftercooler heater. The block temperature was recorded at 78 deg. at the time. The backfire occurred 10-15 seconds after ignition. It had been 2-3 weeks since the last engine start. It is a brand new genset.
Cammax indicated from the referenced thread above that a backfire is usually caused by some other mechanical failure of some sort. I want to know what those failures might be.

Any insight is appreciated.

 

[DrRTU]

For sound and strength I use sch. 40 pipe. On a few applications, I have used the double wall stainless engineered systems by Van Packer and Metalbestos. In in all stainless engineered system, I have installed the relief valve to makes sure the product did not blowup due to a back fire on the exhaust side of the plant. Its not big $$ - less than 2k for 12"

http://www.selkirkcorp.com/commercial-and-industrial/product.aspx?id=226#

I believe fuel in the exhaust is the common cause of an exhaust backfire when a unit is stopping. Sound power increases with the stainless.

 

[Smokerr]

The only time I have had an issue with a diesel engine back fire was/is exhaust system (this is a fire pump so there are different operational characteristics than a gen set that you can cool down, in this case cool down is not possible and has to be accepted)

In our case the silencer is horizontal, and as near as I can determine, we get a build up of un-burnt fuel and or oil in it. The engines are Detroit Diesel 2 cycles that really need to be run fully loaded, not the 60% we get on tests).

The back fire does not occur until the engine has been run for 30 minutes at full load, then turned off, and then back on (annual certification)

To date its caused no problems other than concern, but it certainly is something to be taken seriously.