Regulating relief valves were originally developed in response to the need for accurate regulation of high pressure at low flow without the “chatter” often encountered with valves this size. They are a differential area poppet design with a high ratio between seal and seat area for smooth control, repeatability and low deadband between crack and reseat pressure. The configuration also makes the control settings virtually unaffected by downstream outlet pressure. This enables the valves to be also used for back pressure control (upstream pressure controller) or a sequence (priority pressure valve). Materials of construction options seen in the chart of model numbers provide selections for most liquids including plain water plus most industrial gases including pure oxygen. Note that the nylon insert seat models are recommended for all gas applications below 10,000 psi. The 15700 series valves for service up to 60,000 psi are normally used as safety valves at these pressures. Although not rated as bubble tight, they do an excellent job holding high pressure gas due to their precision poppet and hardened stainless steel seat with heavy silver plating.