Natural Gas Piping

[pipingdesigner]

I am installing an emergency generator that runs on Natural Gas.

TWO questions:

1. Generator requires 170 cubic feet of gas at full load, the meter pressure is 5 PSI, and the distance from meter to generator ia about 100 feet -WHAT SIZE PIPE IS NEEDED??

2. Somehow I recall that "black iron" pipe is best for gas, AND that I should NOT use anything with more than 75% copper -- Why can I NOT use COPPER with natural gas?



pipingdesigner

http://www.pipingdesigners.com

 

[CRG]

Natural Gas 1000 BTU/SCFH
SCH 40 Steel
Fitting factor 1.2
100 feet
5 psia upstream
2.5 psia downstream

730 MBH


Copper is a poor choice if H2S is present. Check the relevant building code for your area: IMC, UMC, etc. They will have the information you require. If I recall correctly, there is a cutoff limit such that when H2S is XXX ppm then copper is not allowed. Some engineers will state that copper is not allowed; however, I refer your relevant mechanical code for this determination.

 

[davefitz]

H2S may be available in trace amounts if the gas is odorized, as is normally done as the gas enters the "city gates".

Also, some local building codes still have pipe requirements left over from the old old old days ( 1930's) when the towns would produce their own gas using coal gasification- in those days, the low BTU coal gas would require galvanized piping, but today's natural gas uses "black (ductile) iron" or carbon steel.

 

[katmar]

PipingDesigner,

Is the 2.5 PSI (presumably gage and not absolute) quoted by CRG the required pressure at the generator? Without knowing the required pressure it is not possible to size the pipe.

regards
Katmar

 

[CRG]

Thanks katmar, both pressures I stated in the above post should have been psig. You are correct that there was not enough info, so I assumed some so pipedesigner could get an idea of the pipe size verses flow. Pipedesigner did not give the needed flow of gas either. His requirements of 170 cubic feet at full load is meaningless without a unit of time.

 

[katmar]

CRG, I read what I thought was there and not what was actually there! I was sure the post said 170 cfm, but when I went back and checked I realized my mistake.

Come on PipingDesigner! Give us some info and we will give you some answers ;-)

regards
Katmar

 

[jsummerfield]

Normally in the US, H2S levels are not supposed to exceed 4 ppm. Upsets could briefly permit higher levels before the system is shutdown. All such things are subject to ethics and competency.

John