Pipeline quality gas is natural gas that has been processed to remove contaminants and to establish a heating vale that meets specific pipeline quality standards. Pipeline quality gas consists primarily of methane with some additional natural gas liquids (NGLs). Here is a typical composition of pipeline quality gas:
The specific requirements for pipeline quality gas are set forth in each pipeline’s tariffs. These requirements are necessary for safe and economic operation, prevention of maintenance issues, and consistency with the design of customer equipment. The tariff containing the pipeline specifications can usually be obtained on the pipeline’s website. Here is an example of a typical gas quality specification:
- Energy content (heating value) no lower than 995 Btu/cf
- Commercially free from sand, dust, gums, and crude oil
- Hydrogen sulfide no greater than ¼ grain per 100 cf
- Total sulfur no greater than 2 grains per 100 cf
- Carbon dioxide no greater than 2% by volume
- Water vapor no more than 4 pounds per one million cf
- Temperature shall not exceed 120 degrees Fahrenheit
- Oxygen no greater than 0.4% by volume
- Hydrocarbon dew point no greater than 15 degrees Fahrenheit at pressure of 800 pounds per square inch gauge (psig)
Gas quality is monitored by gas transmission pipelines and local distribution companies (LDCs). If gas entering a transmission or distribution system does not meet the specified gas quality standards then the pipeline or LDC can shut off the source of the supply until the issue is rectified.