Gas pipelines and piping systems must not be operated at pressures in excess of Maximum Allowable Operation Pressure (MAOP). Various components are used throughout the system to ensure that pressures are kept below MAOP limits. Pressure control on the transmission mainline is provided by transmission pressure limiting stations, control on distribution systems is provided by distribution regulation stations, and pressure into the customer facility is provided by regulators typically located at the customer meter. Redundancy of pressure control is required by code to maintain safe operation in the event of equipment failure.
The pressure regulator is the disk-shaped device at the top left of the meter: