A natural gas pipeline uses pressure from compressors to move the gas through the pipeline. There were 185,744 miles of interstate natural gas pipelines in the US in 1997 Most natural gas pipelines operate using a complex have become so automated that they are capable of operating under command of a computer system that coordinates the operation of valves, prime movers, and conditioning equipment. The computer receives input from each part of the system, including the conditioning and measuring equipment. In case of malfunction at any point in the process, the computer searches its programs for possible corrective actions and simultaneously sounds alarms at the appropriate control points. An interesting aspect of natural gas pipelines is the introduction of odorants into the gas system.
Natural gas is almost odorless as it comes from the well or processing facility.
If the gas is destined for use as a fuel in homes or industry, a chemical called a mercaptan is added to give the gas a distinctive odor so that people can easily smell it when its concentration in air reaches 1 percent. Gas and air mixed in this concentration are not hazardous, but a mixture containing 5 percent gas is explosive. The odorant makes leaks or other unburned discharges of the gas quite evident long before a real hazard exists. Odorants injected into the gas burned in homes or industry do not create odors while burning, nor do they leave troublesome residue. Odorants are usually not introduced into gas sent to petrochemical plants where the gas is used as a feedstock for producing other commodities such as plastics, since the mercaptan will frequently interfere with the chemical process.