In short, the adjusted pressure is the pressure value output by the pressure reducing valve after adjustment, which is different from the working pressure of the pressure reducing valve. For example, if the working pressure of a pressure reducing valve is set to 0.8 MPa, its adjustment range is between 0.3 and 0.6 MPa. If, after adjustment, its output pressure reaches 0.4 MPa, then we can say that the adjusted pressure of the pressure reducing valve is 0.4 MPa.
This adjustment method is also applicable to various types of pressure reducing valves, including water pressure reducing valves, gas pressure reducing valves, gas cylinder pressure reducing valves, steam pressure reducing valves, and self-operated pressure reducing valves.
First, close the gate valve in front of the pressure reducing valve and open the gate valve behind the pressure reducing valve to create a low-pressure downstream environment. Next, rotate the adjusting screw counterclockwise to the preset position (usually based on the outlet pressure), and then close the gate valve behind the pressure reducing valve. Afterward, slowly open the gate valve in front of the pressure reducing valve to the fully open state. After ensuring that the gate valve in front of the pressure reducing valve is fully open, slowly rotate the adjusting screw clockwise to gradually adjust the outlet pressure to the desired level (note that the gauge pressure behind the valve should be used as a reference). Finally, tighten the lock nut and open the gate valve after the pressure reducing valve to ensure the adjustment effect.
When the output pressure of the pressure reducing valve is high or the flow diameter is large, directly using the pressure adjusting spring for pressure adjustment may result in excessive spring stiffness, causing large fluctuations in output pressure when the flow rate changes, and also increasing the structural size of the valve.
The adjustment of the pressure reducing valve is based on its working principle. It reduces water pressure by utilizing the local resistance of the water flow in the valve's internal flow channel. This reduction range is automatically adjusted by the pressure difference between the inlet and outlet water on both sides of the diaphragm or piston connected to the valve disc. The constant ratio pressure reduction principle utilizes a floating piston in the valve body to control the water pressure ratio; the pressure reduction ratio at the inlet and outlet ends is inversely proportional to the area of the pistons on both sides. This type of pressure reducing valve has advantages such as stable operation, no vibration, no spring corrosion or metal fatigue failure, and good sealing performance. It can reduce both dynamic and static pressure without affecting the water flow rate during pressure reduction.
Pressure Adjustment Range: The pressure adjustment range of the pressure reducing valve refers to the range within which its output pressure P2 can be adjusted and controlled, and a specific accuracy must be achieved within this range. This range is mainly affected by the stiffness of the pressure adjusting spring. Pressure Characteristics: When the flow rate g remains constant, the pressure characteristics describe how fluctuations in the input pressure cause corresponding fluctuations in the output pressure. A high-quality pressure-reducing valve should have minimal output pressure fluctuations to ensure stable performance. Typically, the output pressure needs to be lower than the input pressure by a certain value to achieve a state of near instability with changes in the input pressure.
Flow Characteristics: The flow characteristics reflect how the output pressure changes with variations in the output flow rate g, while the input pressure remains constant. Ideally, the output pressure should exhibit the smallest possible fluctuations when the flow rate g changes. Furthermore, generally, the lower the output pressure, the smaller its fluctuations with changes in the output flow rate.