What You Need to Know about Instrument Valves as An Instrument Engineer?

Failure of any measuring instrument in the chemical plant will cause trouble to the entire production process, and even cause interruption of the production process or cause safety problems. As an important part of the control instrument, the failed instrument valve is also a big problem. So, how to effectively maintain the huge production system to avoid the failure of the instrument control system?

Cable

Do not mix the signal cable and the power supply cable with a multi-core cable. When the cable is laid in the trough, the intrinsically safe cables, power cables, and signal cables should be separated by a partition. The cable should not have an intermediate connector.

Instrument

When designing a flow instrument, it is necessary to select the appropriate flowmeter type according to the measurement medium, temperature, and pressure, and do a good job in flow compensation. When the instrument is designed to enter the slot plate of the control room, in order to prevent rainwater from entering the control room, it must be considered to bend up and down and be sealed.

Before the installation of the instrument, the single-unit debugging must be completed. During the installation, pay attention to various special requirements of the flow meter. After the installation is completed, the circuit debugging must be completed to perform the joint debugging.

The on-site maintenance of the instrument must be contacted with the technical personnel, and the process status must be turned off when the instrument with power supply is disassembled, and then use the multimeter to confirm whether the power is turned off. When repairing the disconnection of the instrument, you must pay attention to wrap the thread to prevent short circuit.

Do not stick oil to the maintenance of oxygen pipeline instrument equipment, and do not mix oil-free transmitters and pressure gauges with ordinary meters. Outdoor instruments should be equipped with instrument protection boxes or wrapped with nylon plastic bags. The protection of the meter should use fireproof asbestos cloth.

Valve

In the process of designing and selecting control valves, designing pipelines, and determining pressure distribution, the occurrence of flash evaporation must be fully considered. From the perspective of the control valve, attention should be paid to increase the hardness of the material, reduce the flow rate of the fluid, and select the appropriate control valve type and flow direction. For valves and butterfly valves, single-seat valves with low pressure recovery can be selected.

There are three measures to eliminate and reduce cavitation. The first is to control the pressure drop so that cavitation does not occur. For example, a multi-stage pressure reduction method is used to divide the pressure drop of the control valve into several levels. The second is to reduce the effect of cavitation, using methods similar to preventing flash evaporation, such as increasing the hardness of the material, reducing the flow rate to reduce the impact of cavitation. The third is to reasonably distribute pipeline pressure and increase downstream pressure.

After the pneumatic control valve is installed, be careful not to reverse the function settings of the air-open and air-closed types on the DCS. When the instrument is introduced from the main pipe, the valve must be above the center of the pipeline, preferably at a 90-degree position above the pipeline, to avoid the dirt in the wind line from entering the instrument valve.

Anti-electric Shock

Do not dismantle and install equipment with electricity. Carry a test pencil with you to prevent the risk of electric shock. We must do anti-static work, do not cause accidents due to static electricity.

Hopefully this passage can help you learn more about instrument valves.