From experience, finding a simple method to size natural gas lines can be a challenge. Years back I found this chart in the Cleaver Brooks Boiler Company product and reference manual which has a great chart (see related PDF below) to size natural gas lines. It is data that I have used for many years to size gas lines for jobs we have done and the data is very accurate and spot on.

The basis of the information provides data for schedule 40 pipe and in a typical range of initial gas pressures and at a pressure drop of 5% of the initial gas pressure which is conservative basis for selection. Flows are for 100 ft of pipe run and correction factors provide for other pipe lengths.

A quick example will illustrate how simple this chart is to use to size a gas line for your application. Let us assume you added some additional gas equipment to your plant and need run a new gas line. Total up the gas consumption of each piece of equipment. Name plates on the equipment burner should provide the information you require. If the data is in cubic feet per hour you are home free. If the data is in some other form then you will need to make a conversion.

If the data is in cubic feet per minute (CFM), divide by 60 to convert it to cubic feet per hour (CFH). If the data is in BTU/HR, then use the conversion that 1000 BTU/HR is equal to 1 cubic feet per hour. Say you have a burner rate for 100,000 BTU/HR. Divide 100,000 by 1000 and the gas flow in CFH would be 1000 cubic feet per hour. If you have a rating in Therms, one Therm is 100,000 BTU/HR and on Dekatherm is 1,000,000 BTU/HR.

Let us say you have done your conversions and total your new equipment load to be 10,000 cubic feet per hour and you require a piping run of 175 feet. Since the correction for 175 ft is not published play safe and use the correction for 200 ft which is .707. Divide your 10,000 CFH by .707 to correct your data to a rate per 100 ft of pipe which works out to 14,144 CFH. Say your gas pressure is 5 psig. Your pipe size selection would be a 3 inch schedule 40 line which when corrected for a .707 correction factor would flow 10,000 CFH.

Make sure you follow on local piping codes on your gas pipe, valves, gas pressure reducing valve and fittings. Many areas require that gas lines be installed by a licensed contractor-typically a licensed plumbing contractor-so check local codes.

Need help with sizing a natural gas line, selection of a gas pressure reducing valve, gas flow meters, gas cocks and other items for natural gas service-give us call.