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Factors affecting the stability of the pressure reducing valve
1. Working principle of domestic pressure reducing valve The opening of the pilot valve is to use the top adjusting bolt to turn clockwise to make the elastic force generated by the spring contraction, so that the diaphragm of the pilot valve is recessed downward and acts on the connecting rod of the pilot valve. Force to displace it to open the pilot valve. When the pilot valve is opened, the steam in the upstream inlet pipe section a passes through the α channel (supply steam regulating passage), passes through the pilot valve into the pilot valve annular steam chamber, and is directly sent to the lower piston cylinder upper chamber by the β channel. Under the continuous supply of a cavity steam, the pressure continues to rise, pushing the piston down to open the main valve, at which time the steam source continuously flows from the cavity a to the cavity b. When the downstream outlet pipe section b cavity load is satisfied, the excess steam causes the pressure in the b cavity to continuously increase. The increasing pressure is fed back to the lower chamber of the pilot diaphragm through the gamma channel (pressure sensing channel), causing the diaphragm of the pilot valve to protrude upward, overcoming the pressure of the upper adjusting spring, and the pilot valve is closed or closed. Thus, the source of steam from the upstream alpha channel is turned off or turned off. When the pressure in the upper chamber of the piston cylinder drops, the main valve is closed or closed under the action of the lower return spring. At this time, the pressure in the b chamber begins to decrease, so that the pressure regulation is repeated.
2. Working principle of the imported pressure reducing valve When the pilot valve is opened, the steam in the upstream pipe section a quickly enters the internal filter cover, and reaches the a channel (supply steam regulating passage) through the pilot valve. When the a channel is filled with steam, it is directly sent to The main valve diaphragm is in the lower chamber while a portion of the steam is split into the b chamber through the b channel (pressure control channel). The lower cavity of the main valve diaphragm is continuously supplied under the a-channel steam, and the main cutting diaphragm is pressed upwards, and the generated thrust pushes the main valve rod upward to open the main valve, and the same steam continuously flows from the a cavity to the b cavity. . When the load of the downstream outlet pipe section is satisfied, the excess steam also causes the pressure in the b-cavity to continuously rise, and the increasing pressure is transmitted to the lower steam chamber of the pilot valve diaphragm through the c-channel (pressure sensing channel). When the diaphragm of the pilot valve protrudes upward, against the pressure of the upper adjusting spring, the pilot valve is closed or closed to reduce and cut off the steam from the cavity a. When the pressure in the lower chamber of the main valve diaphragm is gradually reduced, the upper main valve spring acts to make the main cutting spool descend to the seat, and the main valve is closed or closed (the excess steam is simultaneously released into the b chamber through the b channel, and the main valve is Quickly shut down), so that the pressure of the b cavity is continuously decreasing, so as to achieve adjustment. (The principle of opening the pilot valve, the same as the domestic valve)
3. Analysis of the mechanism of condensed water damage regulation and regulation function When the downstream pressure rises (b cavity), pressure is required to be adjusted downward. Under normal circumstances, the super-high pressure of the b-cavity is transmitted to the pilot valve through the pressure-sensing passage (γ), so that the pilot valve is closed or closed, thereby closing and cutting off the steam source from the a-cavity. When the condensed water invades into the cylinder and the annular steam chamber, due to the incompressible nature of the water, at this time, the main valve return spring completely loses its function, the piston cannot move up, the main valve cannot be closed, and the steam of the inlet (a cavity) is still continuously flowing. , through the main valve in the normally open state into the b cavity. Make the pressure too high and get out of control. When the system condensate fills the a, b channel and the main diaphragm lower chamber. Under the thrust from a cavity steam, the main valve diaphragm is in an upwardly bulged state. Similarly, the water is incompressible, so that the upper return spring cannot be returned to the seat, and the main valve is also in the normally open state, and the stable adjustment function is destroyed.
Although the pressure reducing valve is a proportional regulating valve, when the condensed water is filled with these core working parts in the valve, the proportional adjustment property is completely changed. The key problem is the action of the frictional resistance of the moving parts and the sequence of actions. The time difference determines the hysteresis of the main valve motion. (The pilot valve moves first, the main valve trails behind.) After accepting the overpressure message from γ and c channels, first, close or close the pilot valve. In this way, the retreat of the condensed water in the valve is cut off, and it is obvious that the piston and the main valve diaphragm cannot move. 
Factors affecting the stability of the pressure reducing valve