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Governing Code or Standard for Diesel Generator Exhaust Piping?

jehake12 (Mechanical) (OP)
2 Jun 11 18:20
What is the governing code or standard for diesel generator exhaust piping?

The application would be central utility plants (hospitals) with 2.5MW output.
Tmoose (Mechanical)
3 Jun 11 7:53
I saw one long ago for an auxialliary power unit in the basement of a fancy old apartment building. I recall info about materials, expansion joints, orientation relative to adjacent roof, doors and windows. it will take a while for the memory to float to the surface.

I'm starting to think there is some design info in the ASHRAE handbooks, and they often reference codes.

The local fire authorities almost certainly will have to be satisfied
TheBlacksmith (Mechanical)
3 Jun 11 9:25
Do not forget the OEM requirements regarding backpressure etc.  I cannot count how many installations may have met fire and safety code, while creating pounds per square inch (that's right PSI) of back pressure and severely limiting the output of the genset.  100+ feet of pipe to direct the noise and smoke over the top of a building requires a much larger diameter than many people assume.
ivymike (Mechanical)
3 Jun 11 10:46
here's some good general info about designing exhaust systems for gensets:

MikeHalloran (Mechanical)
3 Jun 11 14:10
There isn't _A_ code of which I am aware.  

The AHJ may have some preferences.

The CAT info provided by IvyMike is pretty decent.  Pay particular attention to the need for supports and flex joints, and to sizing the system to stay within the engine's backpressure budget.  ... which is not much, and is smaller for newer high tech engines and for larger engines.

A good silencer may consume half or more of the backpressure budget, so don't ignore it when sizing the pipe; ask a silencer manufacturer for performance numbers for use with the specific engine.

If the customer gets sticker shocked and says they can do without a silencer, size the pipes for one anyway; the customer's neighbors will change his mind.

Rule of Thumb:  Very quiet, "Hospital Grade" silencers are available, and preferred, and will occupy about as much volume as the engine itself does.  Not the cubic inch displacement; the L/W/H volume of the engine's exterior.

The silencer and the pipes get very hot when the engine is running at full song.  Beware of radiation to nearby flammable surfaces.  Thermal insulation blankets are available at some cost; they will greatly reduce heat transfer to the surrounding spaces.


Mike Halloran
Pembroke Pines, FL, USA

jehake12 (Mechanical) (OP)
3 Jun 11 16:13
Thanks very much for all the feedback. The CAT info is a great read!
berkshire (Aeronautics)
4 Jun 11 2:31
Another thing to take into consideration, very often these gensets are placed in basements or pits. Make sure that the hot air created by the unit can get out.
 I have made a lot of money retrofitting ventilation units, where this did not happen.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them.  Old professor

TheBlacksmith (Mechanical)
5 Jun 11 17:59
And that combustion air if needed. can get in.  We had a cobbled up installation that drew air from the space and had doors that opened out.  At load, you couldn't pull those doors open with a truck!

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