A gas regulation station is a facility that includes multiple regulators that reduce gas pressure to the operating pressure appropriate for a downstream section of the delivery system. Regulation stations are located where transmission systems interconnect with distribution systems (often called the citygate) and where distribution feeder mains connect with distribution mains. Because it is critically important that maximum allowable operating pressure (MAOP) of pipeline segments is never exceeded, most regulation stations include duplicative regulator components so that failure of one component will not result in excess pressures. In rural areas regulation stations are commonly located above ground. In more urban areas the regulators are often located in underground vaults.
The diagram below shows a gas regulation station with parallel regulator runs. High-pressure gas enters from the left. A valve allows the whole station to be set off if needed for maintenance or an emergency. Valves on each parallel run allow one run to be shut off while the gas flows through the alternate parallel path. Prior to entering the regulators, the gas flows through a filter to remove any material that might clog the regulators. Each regulator run includes two regulators, a primary mainline regulator that normally controls pressure and a monitor regulator that takes over pressure control if the mainline regulator fails to operate properly.