Natural Gas Flow Rate Increase

[Thriggen]

Im a EE with a generator that consumes 987 scfh of natural gas with a minimum operating pressure of 7"WC and a max operating pressure of 13.6"WC. The regulator feeding the gas line is set at 7"WC and the equivalent run to the gen is roughly 170 ft. By looking at the tables with standard assumptions; pressure less that 1.5 psig, .5"WC pressure loss, .6 specific gravity for nat gas, sched 40 steel pipe, it says that I can get 971 scfh. If I increase the pressure to 11"WC, which happens to the be next seeting of the reg, will that be enough to provide the flow I need. The mechanic on the job insist that it will work. What formula(s) should I use to figure this out. I dont want to just assume it will work. Thanks.

 

[MechEngNCPE]

What is the diameter of the supply pipe?

 

[MechEngNCPE]

A 2" line is right on the edge, you can get 854 at 175' with less than 2psi. A 2-1/2" pipe will provide 1360scfm at 175' less than 2psi.

 

[Thriggen]

I forgot to mention that piece of information. Sorry about that. The chart that I referenced listed I could get 971 scfh from a 2" pipe.

 

[Thriggen]

I also forgot to mention the monetary factor. I have 2" pipe ready to go. 2.5" pipe will cost me additional time and money. That's why I was hoping the pressure boost would help me out.

 

[zdas04]

I did something similar for an on-demand water heater. Going from 7" to 11" changed the device from grossly inadequate to outstanding. I don't have the tables to do the calcs for your line, but it sounds like you do and I would go with them.

David

 

[dcasto]

You can use weymouth formula. In any case, your genset could be using anywhere from 400 to 1100 scfh, it depends on load and the gas composition.

Is your lenght actual or does it include equivalent lenght with fittings?.

I get .56 inches H2O drop for 2in sch 40, .24 inches for a 2.5 inch sch 40 and a 1.9 inch drop for a 1.5 inch sch 40 line.

that means you need 2 inches H2O of water extra to use a 2" line versus a 2.5 inch line.