Failure in Monocrystalline Silicon Differential Pressure Sensor

During the measurement process, there are often some failure to monocrystalline silicon differential pressure sensors for some reason. Timely analysis and processing for the failure is critical to ongoing production. Monocrystalline silicon differential pressure sensors have high stability, low temperature drift and high accuracy. However, industrial site conditions are often complex and harsh. The strong corrosiveness and strong electromagnetic interference of the application environment is a severe test for the normal operation of the differential pressure sensor. Therefore, based on practical experience, this paper summarizes the failure and the corresponding treatment methods for monocrystalline silicon differential pressure sensors.

• Circuit failure of monocrystalline silicon differential pressure sensor

When the value displayed on DCS is not normal, firstly open the junction box of the monocrystalline silicon differential pressure sensor. Check if the circuit is virtual connected, shorted or disconnected. Users can check whether the working power of the differential pressure sensor is normal by using a multimeter, whose methods including power supply measurement, quantity resistance measurement and shaking insulation, etc. At the same time, measure whether the output current value of the monocrystalline silicon differential pressure sensor is within the range of 4-20 mA, confirming whether the output value is normal. If there is no output value, it can be confirmed that the monocrystalline silicon differential pressure sensor is damaged and a new sensor is needed. If the field measurement is match the actual experience value after conversion, there is no problem with the instrument and measurement points on site. At this point, the module has been damaged and the module needs to be replaced. If the field measurement is match the computer display after conversion, there is a problem with the pressure tube or the monocrystalline silicon differential pressure sensor.

• Pressure pipe failure of the monocrystalline differential pressure sensor

In general, the pressure pipe failure is manifested by the clogging in the pressure pipe. In the actual production and maintenance, there is a high possibility that the discharge is not timely or the medium is not clean and the alkali powder remains. After a long period of time, the undischarged medium will solidify, which will cause the pressure tube to become clogged, making the measurement impossible. In order to ensure the normal operation for the differential pressure sensor, the pressure pipe should be dredged regularly. In addition, the leakage in the pressure tube is also one of the causes of the failure. Due to the large number of accessories (such as three valve groups) to be connected to the monocrystalline silicon differential pressure sensor, the number of leaks increases and the maintenance workload increases. When constructing and piping, it is necessary to do some work to prevent string gas for the pressure pipe and avoid the occurrence of trachoma in the pressure pipe. The screws at the interface should be tightened to prevent loosening.

• Electromagnetic field interference around the installation position of monocrystalline pressure sensor

During field installation and wiring, various signal lines (especially power cables) are tied together and the signal is subject to interference, especially strong magnetic fields. Under such circumstances, monocrystalline silicon differential pressure sensors occasionally appear to be unable to communicate or even misdirect.

• High voltage pipe and low voltage pipe connection for monocrystalline silicon differential pressure sensor is reversed

Take the orifice plate as an example. When put the system into operation, the output of the monocrystalline silicon differential pressure sensor does not rise, but drops to zero. The reason is as follows.

1. The root valve of the orifice plate or the positive and negative pressure valve at the top of the sensor are not opened. Check the pressure line and open the valve of the positive and negative pressure line.
2. The balancing valve is not closed. The balancing valve should be closed at this time.
3. A leak occurs at the joint of the positive pressure line.

• The output of the monocrystalline silicon differential pressure sensor is abnormal

I. The monocrystalline silicon differential pressure sensor has no output
There are roughly several reasons for this.

1. No power or poor power contact. Check the power circuit and power supply.
2. Poor contact or disconnection in the signal line. Check the output line to resolve the problem.

II. The output of monocrystalline silicon differential pressure sensor is low
The reason and treatment are as follows.

1. The balancing valve is not closed. Close the balancing valve.
2. There are leaks on the positive pressure side pipelines, valves, etc. Check the leak point on the positive pressure side and do the leak prevention work.
3. The valve on the positive pressure side is not open. Open the valve on the positive pressure side.
4. When there is a liquid column in the pressure line, there is gas in the positive pressure tube or the positive pressure chamber of the monocrystalline silicon differential pressure sensor, or the liquid column is lower than the liquid column in the negative pressure tube. Drain the pressure sensor or treat the liquid columns in the positive and negative pressure tubes to maintain the same height.

III. Output of the monocrystalline silicon differential pressure sensor output is unstable
The reason is that the flow in the process line is unstable. Identify the specific cause and eliminate unstable flow.

V. The output of the monocrystalline silicon differential pressure sensor exceeds the maximum value
The reason is that the flow maximum exceeds the range of the flowmeter. Stop the flowmeter to understand production load and material balance.

VI. The output of monocrystalline silicon differential pressure sensor is high

1. There are leakage in pipelines, valves, etc. on the negative pressure side. Check and handle leaks.
2. When there is a liquid column in the pressure line, there is gas in the negative pressure tube or the negative pressure chamber of the monocrystalline silicon differential pressure sensor, or the liquid column is lower than the liquid column in the positive pressure tube. Drain the sensor or treat the liquid columns in the positive and negative pressure tubes to maintain the same height. It is also possible to open a large negative pressure side valve, handle blowdown, and the like.