Generator Exhaust Pipe Re-routing

[bozkirkurdu]

We have a generator on the 1st floor of a building under construction and the original design asks for an exhaust pipe going up to the roof of the building (Building has 3 floors) but our project manager is looking for another alternative to re-route the exhaust pipe. He actually wants the xhaust pipe to go down under the slab of 1st floor, leave the building below grade and go up above grade somewhere in the field about 8-10meters away from the building. Penetration through the side wall of the generator room is not allowed by some certain safety requirements..

Is such a thing possible at all? I am an elecrical engineer but it sounded a bit impossible to me. I know that we have to stay in the range of backpressure limits of the generator. Has anybody done such an application before?

Regards,

 

[MikeHalloran]

I've put generator exhaust pipes in places you wouldn't believe in big yachts. So, insofar as the exhaust pipe itself is concerned, yes, it's possible.

Odd piping layouts tend to get expensive. Does the project manager have a substantial budget for his proposed change?

Is there a silencer somewhere in the system? There should be. Silencers usually consume a large part of the backpressure budget, so extra- long pipes have to be extra, extra fat. And extra, extra expensive, etc.

I know nothing of terrestrial site requirements, so there may be obstacles there. Speculating, ... Nobody would be happy with direct burial, so you'd need an underground conduit/ passage/ tunnel with drains and access for eventual replacement of the pipe. You might need to build a tower or structure to carry the distal end of the pipe ~10m up in the air, and limit access to it.

Would the safety requirements that prevent penetrating the wall also have something to say about tunneling under the wall?




Odd piping layouts also invite participation from experts in other fields. Budget some money for answering the phone from time to time over the next 30 years and hearing things like "Why did you do it that way?" and "I've improved your crummy design, now it's broke, and it's your fault."




Mike Halloran
Pembroke Pines, FL, USA

 

[bozkirkurdu]

Thank you very much Mike, for your valuable answer.

Yes, there is a silencer that we received with the generator.

And no, we don't have an additional budget to make all those changes. There is already a design for the exhaust pipe and it is supposed to penetrate the 2nd and 3rd floor slabs and end on top of the roof. We have the holes and everything in the slabs. Not only the new design issues and maybe fat pipes but digging inside the building, finding a way to go out from the building, coordinating with all the underground infrastructure etc. will be very difficult alone.

But to know that it is possible to route an exhaust pipe as you wish (of course keeping the technical requirements like backpressure, diameter of pipe etc. and the economical aspect of it in mind)

Regards,
Aziz Ozmine
Electrical Engineer
USAID Building Construction Site
Accra/GHANA - West AFRICA

 

[pipehead]

I've had to install 100 foot exhaust stacks for air dispersion before. If you are going through a building,I would use the same doubls stainless steel system usde on chimneys.

Going dowm and under will creat a water trap, remember the exhaust is 10% water and it will condense when cooled by the ground and the water will be very corrosive.

I can not imagine the safety issue of pemetrating the wall.

Why not put the generator out 10 meters and run the wires back underground.

 

[MikeHalloran]

Let me expand on Pipehead's point about the water trap. For every kg of fuel you burn, you get about 1.3 kg of water in the exhaust as a combustion product. In a normal short pipe, that water stays in gas form all the way out. In a long pipe with cool walls, that gas is going to condense and run to the low point, in this case the bottom of the underground loop.

To prevent premature corrosion of the exhaust pipe, and possible engine damage from rising backpressure as the water accumulates, you will have to provide drains in the exhaust pipe to get that water out, and you will need to provide extra deep traps in those drains in order to keep the exhaust gas in the exhaust pipe.



Mike Halloran
Pembroke Pines, FL, USA

 

[bozkirkurdu]

Thank you again. Water accumulation is a very strong argument not to route an exhaust pipe underground. I totally forgot this point.

Aziz Ozmine
Electrical Engineer