Pressure relief valve and pressure-controlled valve

A pressure reducing valve is a valve that reduces the inlet pressure to a desired outlet pressure through regulation, and relies on the energy of the medium itself to maintain the outlet pressure stable automatically. From a fluid dynamics perspective, a pressure reducing valve is a throttling element whose local resistance can be varied; by changing the throttling area, the flow velocity and the kinetic energy of the fluid are altered, resulting in different pressure losses and thus achieving the purpose of pressure reduction. Then, through the regulation of the control and adjustment system, the fluctuations in pressure behind the valve are balanced with the spring force, thereby keeping the pressure behind the valve constant within a certain error range. Self-acting pressure control valves are divided into three series: self-acting pressure, differential pressure, and flow control valves. Self-acting pressure control valves are classified into pre-valve and post-valve types depending on the location of the pressure measurement point; when the pressure measurement point is located before the valve, it is used to maintain a constant pressure before the valve ； When the pressure tapping point is located behind the valve, it is used to maintain a constant pressure behind the valve. When the pressures before and after the valve are applied to both sides of the actuator’s chamber simultaneously, a self-acting differential pressure control valve can maintain a constant pressure across the valve. The differential pressure existing between the orifice plates installed in the pipeline can also be applied to both sides of the diaphragm actuator’s chamber to form a self-acting flow control valve; alternatively, flow can be detected and then regulated using a self-acting differential pressure control valve. A pressure relief valve is a valve used to control the pressure behind a valve in a pipeline; this is its main difference from a self-acting pressure regulator, as it cannot control the pressure before the valve. It also uses the pressure of the medium in the pipeline to drive the valve core up and down, thereby changing the throttling area between the valve core and the valve seat and maintaining stable pressure behind the valve. The main features are: 1. It maintains stable pressure behind the valve, requires no external energy source, and is energy-efficient. 2-piston pressure reducing valves, which can be used for high-temperature and high-pressure steam and gas media. 3 For medium at normal temperatures such as water and air, a diaphragm-type pressure reducing valve can be used. 4 When controlling the pressure behind a control valve, a pressure reducing valve is a preferred choice, as it offers good cost-performance and low costs.