The 106-RPS and 206-RPS pressure relief valves are based on the 106-PG and 206-PG main valves.
The 81-RP pilot senses the upstream pressure through a connection to the valve inlet. The valve and pilot remain closed until the inlet pressure exceeds the pilot setting. The valve opens rapidly to relieve damaging overpressure and closes smoothly at an adjustable speed, when the pressure returns below the set-point. The upstream pressure is limited to the pilot set-point.
For more information on the 106 / 206-RPS pressure relief valve: