In urban water supply, as the number of downstream water users increases or decreases, the pressure in the pipeline will change greatly, thus affecting normal use. Pressure reducing valves can adjust the higher pressure in the upstream to the appropriate pressure according to the downstream usage, thus ensuring the downstream water supply pressure to fight and stabilize.
Pressure reducing valve is a kind of hydraulic control valve that regulates the high pressure in pipeline to the low pressure downstream, which is widely used in urban water supply network.
Pressure reducing valves are one-way valves, and when installing them, you need to pay attention to the flow arrows on the valve body and install them according to the instructions of the flow arrows.
There are two pressure gauges installed on the valve body, the inlet pressure gauge shows the pressure of the inlet of the pressure reducing valve, which refers to the original pressure of the pipeline, generally we say that the PN value of the pressure reducing valve refers to the pressure of the inlet. The pressure gauge at the outlet shows the pressure at the outlet, i.e. the pressure after it has been reduced by the pressure reducing valve.
The needle valve (fig. 21) is able to regulate the flow rate. First we open the needle valve and close the guide valve (fig. 20), the fluid is injected from the inlet into the control chamber (as below blue part), the fluid pushes down the valve disc (fig. 8) and the pressure reducing valve closes.
Pressure Reducing Valve Diagram
If we open the guide valve (diagram 20), the water in the control chamber (blue part as above diagram) is flowing down the guide valve into the outlet. Once the water in control chamber (blue part as above diagram) flow out, then there is no water pressure in the control chamber , and the disc of the pressure reducing valve is closed only if it is under the pressure of the water pressure in the control chamber, once the water pressure in the control chamber is no longer available, the valve disc of the pressure reducing valve will be opened, the upstream water of the valve body will flow into the downstream at this time.
The guide valve is the key for whole pressure reducing valve, play the role of guide.
According to the pressure needed downstream of the pressure reducing valve, we adjust the adjusting screw on the pressure reducing valve guide valve, the adjusting screw is to adjust the guide valve to open or close tightness. After adjusting the tightness of the adjusting screw according to the required downstream pressure, the position of the adjusting bolt is fixed with the fixing nut on the top of the guide valve.
Guide Valve of Pressure Reducing Valve
When we adjust the adjusting screw(fig.2 as above) on the guide valve downward, the adjusting screw will press the Spring (fig.6 as above) adjacent to it, then the spring presses the diaphragm(fig 11 as above) adjacent to it, the diaphragm presses the Disc(fig.14) adjacent to it, and after the disc is pressed downward, the water inside the guide valve conduit will flow downstream of the pressure reducing valve, resulting in a decrease in the pressure of the water in the control chamber, and the pressure reducing valve disc opens, then the water flows from the upstream to the downstream of the main valve. The downstream pressure increases.
When the downstream pressure reaches the value we need, the downstream water will enter the valve chamber of the guide valve, the water pressure will go up with the disc to top the spring, resulting in the closing of the guide valve, the water pressure inside the control chamber of the pressure reducing valve rises, and the water pressure leads to the closing of the valve disc of the pressure reducing valve, resulting in the water flowing downstream from the upstream of the valve to be reduced or closed, and the downstream water pressure decreases.
And as the downstream water flows out, the downstream pressure decreases, after the downstream pressure decreases, the water pressure in the guide valve decreases or disappears, under the action of the spring, the guide valve reopens, resulting in the flow of water out of the control chamber, the water pressure in the control chamber of pressure reducing valve decreases, resulting in the opening of the main valve, the upstream water flows into the downstream, the downstream pressure increases, and as the downstream pressure increases, it will again lead to the closing of the guide valve. The closing of the guide valve causes the water pressure in the control chamber to increase, which leads to the closing of the main valve. After the main valve closes, the downstream water pressure will decrease again, and the guide valve and main valve will open again.
So when the pressure reducing valve is installed on the water supply pipeline, if the downstream water users increase, the downstream water pressure will decrease faster, according to the above working principle, when the downstream pressure is small, the guide valve will open, which will make the main valve disc of the pressure reducing valve open, the downstream flow rate and water pressure will become bigger, so as to maintain the stability of the downstream water pressure.
If the downstream water users are less or the downstream pipeline is closed, the downstream water pressure will increase, according to the above working principle, when the downstream water pressure increases, the guide valve will be closed, which will lead to the main valve disc of the pressure reducing valve down, reduce or close the downstream water flow from the upstream of the pressure reducing valve, which will lead to a reduction in the downstream water pressure, so as to maintain the stability of the downstream water pressure.
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