Process Engineering Division – Instrumentation and Automation Section – Daily Question – Question dated 2020-09-18

1. When connecting the flow sensor to the process pipeline, a \"three-valve assembly\" should be used. Its functions are as follows: (1) When a medium is introduced into the pipeline from its initial state (empty), the pressure on both sides of the sensor changes suddenly, resulting in an increased pressure difference. To avoid this situation, valves A and B on both sides of the sensor should be closed first, while bypass valve C should be opened； (2) After the medium fills the pipeline and reaches a stable state, gradually open A and B to apply uniform pressure on both sides of the sensor ； (3) Finally, close valve C, and the sensor begins to function properly ； (4) The shutdown sequence is the opposite of the above case. 2. The function of the “balance valve” installed on the differential pressure transmitter is to prevent one chamber from being under pressure when the transmitter is put into operation, thus avoiding damage to the transmitter due to high pressures; the balance valve remains closed during normal operation. 3. In addition, the 3-valve assembly has other functions as well, such as cleaning the pipes after operation for a certain period of time, without affecting the sensor section (the pipeline is bypassed)

1. When connecting the flow sensor to the process pipeline, a \"three-valve assembly\" should be used. Its functions are as follows: (1) When a medium is introduced into the pipeline from its initial state (empty), the pressure on both sides of the sensor changes suddenly, resulting in an increased pressure difference. To avoid this situation, valves A and B on both sides of the sensor should be closed first, while bypass valve C should be opened； (2) After the medium fills the pipeline and reaches a stable state, gradually open A and B to apply uniform pressure on both sides of the sensor ； (3) Finally, close valve C, and the sensor begins to function properly ； (4) The shutdown sequence is the opposite of the above case. 2. The function of the “balance valve” installed on the differential pressure transmitter is to prevent one chamber from being under pressure when the transmitter is put into operation, thus avoiding damage to the transmitter due to high pressures; the balance valve remains closed during normal operation. 3. In addition, the 3-valve assembly has other functions as well, such as cleaning the pipes after operation for a certain period of time, without affecting the sensor section (the pipeline is bypassed)

1. When connecting the flow sensor to the process pipeline, a \"three-valve assembly\" should be used. Its functions are as follows: (1) When a medium is introduced into the pipeline from its initial state (empty), the pressure on both sides of the sensor changes suddenly, resulting in an increased pressure difference. To avoid this situation, valves A and B on both sides of the sensor should be closed first, while bypass valve C should be opened； (2) After the medium fills the pipeline and reaches a stable state, gradually open A and B to apply uniform pressure on both sides of the sensor ； (3) Finally, close valve C, and the sensor begins to function properly ； (4) The shutdown sequence is the opposite of the above case. 2. The function of the “balance valve” installed on the differential pressure transmitter is to prevent one chamber from being under pressure when the transmitter is put into operation, thus avoiding damage to the transmitter due to high pressures; the balance valve remains closed during normal operation. 3. In addition, the 3-valve assembly has other functions as well, such as cleaning the pipes after operation for a certain period of time, without affecting the sensor section (the pipeline is bypassed)

1. When connecting the flow sensor to the process pipeline, a \"three-valve assembly\" should be used. Its functions are as follows: (1) When a medium is introduced into the pipeline from its initial state (empty), the pressure on both sides of the sensor changes suddenly, resulting in an increased pressure difference. To avoid this situation, valves A and B on both sides of the sensor should be closed first, while bypass valve C should be opened； (2) After the medium fills the pipeline and reaches a stable state, gradually open A and B to apply uniform pressure on both sides of the sensor ； (3) Finally, close valve C, and the sensor begins to function properly ； (4) The shutdown sequence is the opposite of the above case. 2. The function of the “balance valve” installed on the differential pressure transmitter is to prevent one chamber from being under pressure when the transmitter is put into operation, thus avoiding damage to the transmitter due to high pressures; the balance valve remains closed during normal operation. 3. In addition, the 3-valve assembly has other functions as well, such as cleaning the pipes after operation for a certain period of time, without affecting the sensor section (the pipeline is bypassed)

Function of the three-valve assembly: 1) When both the high-pressure and low-pressure valves are closed, it can cut off the connection between the pressure lead and the transmitter, allowing for the inspection and removal of the transmitter. 2) When both the high-pressure and low-pressure valves are closed and the balance valve is opened, the positive and negative pressure chambers of the transmitter become connected, resulting in equal pressures and a zero pressure difference; the instrument will then indicate zero, allowing for zero-point checking and adjustment. When installing, it is important to note that the three-valve assembly must not be installed in the wrong direction; otherwise, the balance valve will lose its function, and the instruments may be damaged due to being subjected to pressure in one direction when put into use.

Function of the three-valve assembly for instruments: 1. When connecting a flow sensor instrument to the process pipeline, a \"three-valve assembly\" is used. Its functions are as follows: (1) When a medium is introduced into the pipeline from its initial state (empty), the pressure on both sides of the sensor changes suddenly, resulting in an increased pressure difference. To avoid this situation, valves A and B on both sides of the sensor should be closed first, with valve C being opened； (2) After the medium fills the pipeline and reaches a stable state, gradually open A and B to apply uniform pressure on both sides of the sensor ； (3) Finally, close valve C, and the sensor begins to function properly ； (4) The shutdown sequence is the opposite of the above case. 2. The function of the “balance valve” installed on the differential pressure transmitter is to prevent one chamber from being under pressure when the transmitter is put into operation, thus avoiding damage to the transmitter due to high pressures; the balance valve remains closed during normal operation. 3. In addition, the 3-valve assembly has other functions, such as cleaning the pipes after operation for a certain period of time, without affecting the sensor section (the pipeline is bypassed). Points to note during installation: 1. Check whether the valves, pressure guide tubes, union joints, etc. of each instrument’s three-valve assembly are firmly connected ； 2. Check whether the secondary valve and the drain valve are closed, and whether the balance valve is closed (for the three-valve set) ； 3. Open the valve slightly (the root valve), then check the pressure guide tube, valve, union, etc.; if there is no leakage, open the valve fully ； 4. Open the drain valves separately, discharge the waste fluid, and then close the drain valves ； 5. Loosen the screw plug in the differential pressure chamber to remove the air from it ； 6. The differential pressure transmitter can be started only after the pressure guiding pipe is filled with condensed water ； 7. Start the differential pressure transmitter, open the three-valve block for positive pressure instruments, close the balance valve, and open the negative pressure valve.

1. When connecting the flow sensor to the process pipeline, a \"three-valve assembly\" should be used. Its functions are as follows: (1) When a medium is introduced into the pipeline from its initial state (empty), the pressure on both sides of the sensor changes suddenly, resulting in an increased pressure difference. To avoid this situation, valves A and B on both sides of the sensor should be closed first, while bypass valve C should be opened； (2) After the medium fills the pipeline and reaches a stable state, gradually open A and B to apply uniform pressure on both sides of the sensor ； (3) Finally, close valve C, and the sensor begins to function properly ； (4) The shutdown sequence is the opposite of the above case. 2. The function of the “balance valve” installed on the differential pressure transmitter is to prevent one chamber from being under pressure when the transmitter is put into operation, thus avoiding damage to the transmitter due to high pressures; the balance valve remains closed during normal operation. 3. In addition, the 3-valve assembly has other functions as well, such as cleaning the pipes after operation for a certain period of time, without affecting the sensor section (the pipeline is bypassed)

1. When connecting the flow sensor to the process pipeline, a \"three-valve assembly\" should be used. Its functions are as follows: (1) When a medium is introduced into the pipeline from its initial state (empty), the pressure on both sides of the sensor changes suddenly, resulting in an increased pressure difference. To avoid this situation, valves A and B on both sides of the sensor should be closed first, while bypass valve C should be opened； (2) After the medium fills the pipeline and reaches a stable state, gradually open A and B to apply uniform pressure on both sides of the sensor ； (3) Finally, close valve C, and the sensor begins to function properly ； (4) The shutdown sequence is the opposite of the above case. 2. The function of the “balance valve” installed on the differential pressure transmitter is to prevent one chamber from being under pressure when the transmitter is put into operation, thus avoiding damage to the transmitter due to high pressures; the balance valve remains closed during normal operation. 3. In addition, the 3-valve assembly has other functions as well, such as cleaning the pipes after operation for a certain period of time, without affecting the sensor section (the pipeline is bypassed)

1. When connecting the flow sensor to the process pipeline, a \"three-valve assembly\" should be used. Its functions are as follows: (1) When a medium is introduced into the pipeline from its initial state (empty), the pressure on both sides of the sensor changes suddenly, resulting in an increased pressure difference. To avoid this situation, valves A and B on both sides of the sensor should be closed first, while bypass valve C should be opened； (2) After the medium fills the pipeline and reaches a stable state, gradually open A and B to apply uniform pressure on both sides of the sensor ； (3) Finally, close valve C, and the sensor begins to function properly ； (4) The shutdown sequence is the opposite of the above case. 2. The function of the “balance valve” installed on the differential pressure transmitter is to prevent one chamber from being under pressure when the transmitter is put into operation, thus avoiding damage to the transmitter due to high pressures; the balance valve remains closed during normal operation. 3. In addition, the 3-valve assembly has other functions as well, such as cleaning the pipes after operation for a certain period of time, without affecting the sensor section (the pipeline is bypassed)

1. When connecting the flow sensor to the process pipeline, a \"three-valve assembly\" should be used. Its functions are as follows: (1) When a medium is introduced into the pipeline from its initial state (empty), the pressure on both sides of the sensor changes suddenly, resulting in an increased pressure difference. To avoid this situation, valves A and B on both sides of the sensor should be closed first, while bypass valve C should be opened； (2) After the medium fills the pipeline and reaches a stable state, gradually open A and B to apply uniform pressure on both sides of the sensor ； (3) Finally, close valve C, and the sensor begins to function properly ； (4) The shutdown sequence is the opposite of the above case. 2. The function of the “balance valve” installed on the differential pressure transmitter is to prevent one chamber from being under pressure when the transmitter is put into operation, thus avoiding damage to the transmitter due to high pressures; the balance valve remains closed during normal operation. 3. In addition, the 3-valve assembly has other functions as well, such as cleaning the pipes after operation for a certain period of time, without affecting the sensor section (the pipeline is bypassed)