Self-acting back pressure regulators are simple control valves offering accurate control while being easy to install and maintain. They control the pressure upstream of the valve without requiring pneumatic or electrical control elements.
The RP 824 and RP 825 overflow valves are pilot-controlled control valves of tubular design consisting of a main valve, a pilot valve connected with the main valve via pipes and a restrictor assembly with built-in strainer. The valve cone is fitted with a metallic seal.
When the pipeline is depressurised the main valve is kept closed by a preloaded spring. To open the valve a pressure difference (p1 – p2) of at least 2 bar is required.
When the inlet pressure is above the set pressure the pilot valve is kept open by its control mechanism. Restrictor D1 produces a pressure drop causing the outlet pressure to be almost equal to the pilot pressure in the main valve. The inlet pressure overcomes the pilot pressure and closing force of the spring and opens the main valve.
When the inlet pressure has reached the set pressure, the pilot valve restricts the flow. This causes the pilot pressure to rise and push the main valve piston into a controlling position in which opening and closing forces are in balance.
The restrictors are used to optimise the control characteristics. The bypass line around D2 which is fitted with a non-return valve, ensures quick closing.
The valve is piped internally. The pulse lines must be installed on-site.
These valves are no shut-off elements ensuring a tight closing of the valve. In accordance with DIN EN 60534-4 and/or ANSI FCI 70-2 they may feature a leakage rate in closed position in compliance with the leakage classes III (metal sealing cone - 0.1 % Kvs value).