|The three valve group is to connect or cut off the positive and negative pressure chambers of the differential pressure transmitter with the pressure pipe, or to cut off or conduct the positive and negative pressure chambers. In order to equalize the pressure, the positive and negative pressure chambers are protected from too much pressure. The three valve group consists of valve body, two stop valves and one balance valve. In fact, the three valve group is widely used as a common valve.
The opening sequence of the three valve group is: opening the positive pressure valve, closing the balance valve and opening the negative pressure valve. The sequence of shutdown is as follows: close negative pressure valve, open balance valve and close positive pressure valve
|When the flow or differential pressure sensor instrument is connected to the process pipeline, the "three valve group" shall be used to:
1. When the medium is added into the pipeline from the initial state (empty), the pressure on both sides of the sensor will change suddenly. If the pressure difference is too large, the sensor of the transmitter may be damaged. To avoid this problem, close the valves a and B on both sides of the sensor and open the bypass valve C;
2. After the medium fills the pipe and approaches to stability and balance, open one of a or B to apply pressure evenly on both sides of the sensor;
3. Close valve C and open another valve in a or B, and the sensor starts to work normally;
4. The closing sequence is the reverse of the above.
The 3-valve manifold has other functions, such as cleaning the pipeline after running for a period of time, and the sensor part is not affected (the pipeline is bypassed).