How to determine pipe sizes for high pressure gas using IFGC? trying to add new appliance at plant

[USAeng]

Hello all,

We have 10PSI gas to our plant at a meter. We have .75 MMBTU appliance after 800' of 1-1/4" piping. About 2' after the meter there is a 1-1/4" Tee with a plug. We would like to add another 1-1/4" pipe 475' long to a 2 MMBTU appliance. Both appliances require 14"WC for max fire. I was trying to use the IFGC tables which I am not very familiar.

They have 5PSI table which is the closest. If I use longest leg method we have 2410CFH possible though the pipe. This is no good as we need combined 2750CFH. However this method is conservative from what I read online - also the table is only 5PSI - our pressure is 10PSI

Am I off base in saying we will be fine using the tee and 1-1/4" piping to our new appliance? Thanks for any help

 

[USAeng]

It is schedule 40 metallic pipe

 

[USAeng]

Also it is natural gas sorry

 

[USAeng]

Anyone? Am I way off trying to use the charts provided by IFGC? Any help appreciated

 

[alchemon]

You can use the Spitzglass equation in the code for "high pressure" applications or applications which have no printed sheets. The sheets themselves are calculated from the equations.

Most people use the "longest length" method described in the code. Draw a riser diagram of your system with pipe lengths and loads. Add up the total length of pipe to the farthest appliance. Take this and multiply by 1.5-1.75 for fittings (or calculate the equivalent pipe lengths, if known, from the code). This value is referred to as the total developed length, and will be used as L in the equations. Apply the equations to each branch of piping with the required loads.

You can either assume a pressure drop or assume a pipe size. In your case, I would use the existing pipe sizes and solve for pressure drop. If the existing system is adequate and does not have too large of a pressure drop, you should be fine. Otherwise, you will need to upsize some of the piping.

Once you know the inlet pressure at the application (you are basically using the equations to determine the pressure loss in your piping), you can select a regulator for the gas train.

 

[alchemon]

It is important to remember that at 10 psig your system will deliver significantly more than the 5 psig tables. If your total developed length is 800' and total demand is 2750 CFH, I think that you will be fine - make sure you choose a correct regulator - but you should verify with the equations. You will need to do this anyway to determine the pressure at your appliance for regulator sizing.