【Daily Question】Deep Processing 20161108 Quiz: Briefly describe the working principle of pressure reduction in a pressure relief valve.

A pressure reducing valve uses sensitive components such as diaphragms, springs, and pistons to adjust the gap between the valve disc and the valve seat, thereby reducing the inlet pressure to the desired outlet pressure; it relies on the energy of the medium itself to keep the outlet pressure constant automatically.

I’m not sure if you’re referring to a self-acting type or a pressure-regulating pressure relief valve

A pressure reducing valve is an essential component of pneumatic control valves; its main function is to reduce the pressure of the air supply and stabilize it at a constant level, so that the control valve can receive a stable supply of air power for regulation and control purposes. Based on their structural design, they can be classified into membrane type, spring-membrane type, piston type, lever type, and bellows type ； Based on the number of valve seats, they can be manually classified as single-seat or double-seat types ； Based on the position of the valve disc, they can be divided into direct-acting and reverse-acting types.

A pressure reducing valve regulates the flow rate of a medium by controlling the opening degree of the closing element inside the valve body, thereby reducing the pressure of the medium. Meanwhile, the opening degree of the closing element is adjusted based on the pressure behind the valve, so as to keep the pressure there within a certain range. Cooling water is injected either inside the valve body or behind the valve to lower the temperature of the medium; such a valve is known as a pressure reducing and temperature reducing valve. The automated selection for pressure relief valves is included in Kuaiyiyou. The feature of this valve is that it maintains the outlet pressure and temperature within a certain range, even when the inlet pressure keeps changing.

A pressure reducing valve uses sensitive components such as diaphragms, springs, and pistons to adjust the gap between the valve disc and the valve seat, thereby reducing the inlet pressure to the desired outlet pressure; it relies on the energy of the medium itself to keep the outlet pressure constant automatically.

By adjusting the opening degree of the opening and closing element inside the valve, the throttling area is changed, which in turn alters the flow velocity and results in a loss of kinetic energy.

The kinetic energy of the gas is adjusted by changing the throttle area, including pilot-type and direct-acting types, etc

The schematic diagram of the working principle of the pressure reducing valve is as follows: When P1 changes, the outlet pressure of the pressure reducing valve first becomes P2 ± △P2. This value is transmitted through the outlet pipe of the feedback system to the control valve, resulting in Pt = Pk ± △P2 ； As a result, L changes accordingly, leading to changes in ±△P e; these changes, through the pressure conduit, cause corresponding changes in P k. Pt and P k reach a new equilibrium, and the flow area H of the main valve changes as well. Therefore, P1 changes, while the flow rate through H remains unchanged. P 2 is always the originally set low voltage value. When the flow rate changes, the self-regulating principle of the pressure reducing valve works in the same way. 　1. The QPF-F50 pneumatic balance valve, also known as the main pressure reducing valve, is used in pneumatic circuits to regulate the pressure of compressed air, keeping the set pressure value nearly constant. 　　2. This valve is a pressure-regulating and relief combined valve. When the outlet pressure is below the set pressure, it acts as a pressure regulator to raise the pressure to the set level. When the outlet pressure is higher than the set pressure, it acts as a relief valve to reduce the outlet pressure to the set level. Thus ensuring that the outlet pressure remains consistently at the desired set pressure. 　　3. Since this valve possesses the characteristics of both a pressure regulator and a relief valve, it can function as a substitute for both of them. This results in a simplified system with a more compact design compared to using a pressure regulator and a relief valve separately in the gas circuit system. It also eliminates the set pressure difference between the pressure regulating valve and the relief valve, ensuring that the air pressure in the system can be adjusted more accurately and maintained at the desired set value. 　　4. This valve is a pneumatically controlled pressure-regulating and relief combination valve equipped with pressure feedback from the mineral processing equipment manufacturer; it remains in a closed state when no pilot signal is applied. When the compressed air from the pilot air circuit enters chamber B, this valve begins to operate. The level of the output pressure is controlled by the air pressure entering the pilot port CP; by adjusting this pressure, the output pressure can be set. The compressed air entering control chamber B through the CP port pushes the piston together with the valve element on it to move upward axially, overcoming the force of spring 7 and compressing it. When the overflow port (i.e., the upper surface) of the spool 6 makes full contact with the bottom surface of the valve cover 3, the channel for overflow is blocked. As the piston continues to move upward, the valve core pushes the valve cover upward along the axial direction, causing the spring on the valve cover to compress. This opens the pressure regulating valve, allowing the input chamber to communicate with the output chamber. The compressed air in the input chamber enters the output chamber through the pressure regulating port and is then discharged through the OUT port. The compressed air from the output chamber enters chambers A and C through 2 air paths on the valve body. The pressure of the gas in the 3 chambers is the same. 　　5. When the output pressure is below the set value, the force on the lower side of the piston is greater than that on the upper side; as a result, the piston moves upward, pushing the valve cover 3 upward and increasing the size of the pressure regulating valve opening. This leads to an increase in the flow rate of compressed air entering the output chamber through this opening, and consequently, the pressure in the output chamber rises. When the pressure in the output chamber reaches the set value, the forces acting on the upper and lower sides of the piston are in balance; the piston stops moving upward, and the opening degree of the pressure regulating valve remains unchanged. The pressure and flow rate of the compressed air output from the outlet remain stable. 　　6. When the output pressure is higher than the set pressure, the force acting on the upper side of the piston is greater than that on the lower side; as a result, the valve cover and the piston move downward, which reduces the opening degree of the pressure regulating valve. This leads to a decrease in the flow rate of gas entering the output chamber through the pressure regulating valve, and consequently, the pressure of the gas in the output chamber drops. If the pressure in the output chamber remains above the set value at this point, the piston continues to move downward toward the manufacturer of the magnetic separator until the pressure control valve is completely closed. At this point, the force of spring 1 on the valve cover no longer acts on the piston via the valve spool; instead, it causes the rubber gasket on the bottom surface of the valve cover to press tightly against the pressure regulating valve opening, thereby blocking the passage between the input chamber and the output chamber. At this point, if the output pressure equals the set pressure value, the piston stops moving. The set pressure at this point is the outlet pressure when both the pressure regulating valve and the relief valve are closed, and the valve is in a state of static equilibrium. 　　7. If the output pressure remains above the set value, the piston continues to move downward, causing the upper surface of the spool in the relief valve to separate from the bottom surface of the valve cover 3. This allows the output chamber to communicate with the relief chamber, and the gas in the output chamber is discharged through the EX port via the relief valve opening. As the pressure in the output chamber decreases, the pressure in chamber C also drops. The pressure on the lower side of the piston is higher than that on the upper side, causing piston B to move upward along the axis together with the valve core, thereby gradually reducing the opening degree of the relief valve. When the output pressure reaches the set value, the relief valve port fits tightly against the bottom surface of the valve cover, blocking the passage between the output chamber and the relief chamber, and the leakage stops. At this point, both the relief valve port and the pressure regulating valve port close simultaneously, and the valve reaches a static equilibrium state with no gas flow. Since the air pressures on the upper and lower sides of the valve cover are in a state of mutual equilibrium, any fluctuations in the pressure at the inlet (IN) do not affect the pressure balance within the valve. As a result, the outlet pressure can be maintained stably at the desired set value, ensuring that the valve exhibits good pressure characteristics

A valve that, through adjustment, reduces the inlet pressure to a desired outlet pressure and relies on the energy of the medium itself to maintain the outlet pressure stable automatically.