First let's understand the structure and function of the conventional pressure transmitter. The pressure transmitter is mainly composed of three parts: a pressure sensor, a measurement conversion circuit and a process connection part. Its function is to convert the physical pressure parameters such as gas and liquid felt by the pressure sensor into standard electrical signals for display, measurement, control and adjustment purposes such as display alarms, DCS systems, recorders, and PLC systems. In these tasks, many different problems may occur, this time you need to pay attention to the maintenance and protection of the pressure transmitter in the work.
Let's analyze the precautions in use of specific pressure transmitters.
1. First check whether there is signal interference around the pressure transmitter. If there is, try to eliminate it, or connect the sensor shielding wire to the metal shell as much as possible to enhance the anti-interference ability.
2. Regularly clean the installation holes to ensure the cleanliness of the installation holes. Prevent the transmitter from contacting with corrosive or overheated media;
3. When wiring, pass the cable through the waterproof joint (accessory) or the flexible tube and tighten the sealing nut to prevent rainwater and other leakage into the transmitter housing through the cable.
4. When measuring gas pressure, the pressure port should be opened at the top of the process pipeline, and the transmitter should also be installed at the top of the process pipeline so that the accumulated liquid can be easily injected into the process pipeline.
5. When measuring the liquid pressure, the pressure port should be opened on the side of the process pipeline to avoid precipitation and slag.
6. The voltage higher than 36V cannot be used on the pressure transmitter, which may cause damage.
7. When freezing occurs in winter, the transmitter installed outdoors must take anti-freezing measures to avoid the expansion of the liquid in the pressure port due to the frozen volume and lead to damage to the sensor.
8. When measuring steam or other high-temperature media, a condenser such as a buffer tube (coil) should be connected, and the working temperature of the transmitter should not exceed the limit. And the buffer tube needs to be filled with an appropriate amount of water to prevent the superheated steam from contacting the transmitter. And the buffer heat pipe can not leak.
Installation example of pressure transmitter for measuring steam pipeline
9. When measuring the liquid pressure, the installation position of the transmitter should avoid the impact of the liquid (water hammer phenomenon) to avoid the sensor from being damaged by overpressure.
10. The pressure guiding pipe should be installed in a place with small temperature fluctuation;
11. Prevent dross from depositing in the conduit;
12. The medium measured by the pressure transmitter cannot be frozen and frozen. Once frozen, it will easily damage the diaphragm, because the diaphragm is generally very thin.