Pipe Flow Calculations Forum

I was needing to calculate pipe sizes for a 35psi natural gas system and was attempting to use a chart in the 2012 International Fuel Gas Code for pressure over 1.5psi that I hadn't ever used before. To check myself I attempted to get it to match a table from an old gas book for 20psi delivery. It wasn't matching, so I started looking online for a calculator and found yours. Your calculator matches that IFGC chart. So now I'm trying to figure out why your calculator and that chart don't match the old table. The old table shows consistently higher capacities per pipe size. I've attached a scan of that old table. Any ideas? Has the calculation for calculating this changed since the 60s, or am I doing something wrong?

As a check I was looking at 20psi, 2psi drop, 400' of pipe, 2" pipe size. The old table shows that will carry 10,610 cfh. From the calculator it carries about 7,600 cfh. That's nearly a 30% difference.

Thanks

Which diameter do you use in calculator? D=52.48 mm for 2" SCH40. Also s=0.8 spec.gravity is in table - do you use the same in calculator?
Calculator is based on the Renouard equation which is approximation of real condition but accurate enough for practical purposes. Which equation is used for table?
One another difference - calculator requires absolute pressures and table is for gauge pressure.