Factors Affecting the Stability of a Pressure Reducing Valve |
1. Working Principle of Domestic Pressure Reducing Valves The operation of the pilot valve in a domestic pressure reducing valve begins by turning the top adjustment bolt clockwise, which compresses the spring and creates an elastic force. This causes the diaphragm of the pilot valve to depress downward, pushing the connecting rod and opening the pilot valve. Once open, steam from the upstream inlet (section a) flows through the α channel (supply steam regulation passage) into the annular steam chamber of the pilot valve via the pilot valve. From there, it is directed through the β channel to the upper chamber of the main piston cylinder. As steam continues to flow, pressure builds up, forcing the piston down and opening the main valve. This allows continuous steam flow from section a to section b. When the downstream pressure in section b reaches the required level, excess steam increases the pressure in the b cavity. This pressure is fed back through the γ channel (pressure sensing channel) to the lower chamber of the pilot diaphragm, causing it to rise and close the pilot valve. This cuts off the steam supply from the a cavity. As the pressure in the upper chamber of the piston decreases, the return spring pushes the main valve closed, reducing the pressure in the b cavity and restarting the cycle. 2. Working Principle of Imported Pressure Reducing Valves In imported pressure reducing valves, the process is similar but with slight differences in design. When the pilot valve opens, steam from the upstream pipe section a enters the internal filter cover and flows through the a channel (supply steam regulation passage) via the pilot valve. Once the a channel is filled, steam is directed to the lower chamber of the main valve diaphragm, while a portion also flows into the b channel (pressure control channel). The continuous steam supply to the lower chamber pushes the main diaphragm upward, generating a force that lifts the main valve rod and opens the main valve. Steam then flows continuously from a to b. When the downstream pressure in b rises beyond the set point, the increased pressure is transmitted through the c channel (pressure sensing channel) to the lower chamber of the pilot valve. This causes the pilot diaphragm to rise, closing the pilot valve and cutting off the steam supply from the a cavity. As the pressure in the lower chamber of the main diaphragm drops, the return spring forces the main valve to close, reducing the pressure in the b cavity and restoring balance. 3. Analysis of Condensate Damage and Regulation Function When condensate enters the working parts of the valve—such as the piston cylinder, annular steam chamber, or main diaphragm—it can severely affect the valve's performance. Due to its incompressibility, condensate prevents the main valve from closing properly. In such cases, even if the pilot valve closes, the main valve remains open because the return spring cannot push it back to the seat. This leads to uncontrolled steam flow into the downstream system, resulting in excessive pressure and loss of regulation. If condensate fills the a and b channels and the lower chamber of the main diaphragm, the steam pressure from the a side pushes the diaphragm upward, keeping the main valve in an open position. This disrupts the proportional control function of the valve. Although pressure reducing valves are designed for proportional regulation, the presence of condensate in critical areas changes their behavior. The movement of internal components becomes affected by friction and timing, leading to hysteresis in the main valve's response. The pilot valve typically reacts first, followed by the main valve. However, when condensate is present, the movement of the piston and diaphragm is restricted, delaying the closure of the main valve. This delay can cause overpressure situations and instability in the system. Proper drainage and maintenance are essential to prevent condensate buildup and ensure stable valve operation. |
Chanel Spring Nuts,Zinc Plated Spring Channel Nuts,Zinc Plated Spring Nuts,Zinc Plated Channel Nuts
Kunshan Liyue Hardware Products Co.,Ltd , https://www.fixlyhardware.com