Van An toàn

Safety Valves

Pressure Relief Valves and Back Pressure Valves

   Pressure relief valves and back pressure regulators are designed to provide protection from over-pressure in steam, gas, air and liquid lines. Relief valves and back pressure regulators are the same device, only differing in application. The pressure relief valve "lets off steam" when safe pressures are exceeded, then closes again when pressure drops to a preset level. A back pressure regulator maintains upstream pressure at the desired setting by opening to allow excess upstream pressure to flow downstream.

   A pressure relief valve is a self-operating valve that is installed in a process system to protect against over pressurization of the system.  Relief valves are designed to continuously regulate fluid flow, and to keep pressure from exceeding a preset value. There are a wide variety of valve designs, but most resemble diaphragm valves, globe valves, or swing check valves. With many of these designs, a helical or hydraulic pressure spring is used to maintain a constant force acting on the backside of the valve disk or diaphragm, causing the valve to be normally closed. When the force exerted by the process stream (i.e. fluid pressure) on the valve disk is greater than the constant force exerted by the spring, the valve opens allowing process fluid to exit the valve until the fluid pressure falls below the preset value. These valves can be preset to a specific relief pressure or they may be adjustable