Several protective measures for pneumatic control valves

The role of pneumatic control valves in process control is well known. In many control processes, it is required that the control valve should be in a certain position when a failure occurs to protect the process from accidents. This requires the design of the control valve to implement fail-safe three-break protection measures.

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For electric control valves, it is relatively simple. When the signal is cut off, it can stay at any position of fully open, fully closed, and hold according to the setting of the control module. When the power is cut off, it will naturally stay at the fault position, or the electric actuator with reset device can also stop The valve position runs to fully open or fully closed.

For pneumatic control valves with pneumatic components, the situation is more complicated, so we mainly discuss the three-break maintenance method of pneumatic control valves. Generally speaking, when we choose a pneumatic membrane control valve, we must first determine whether to choose air-on or air-off, that is, the protection position when the valve is cut off. If the process requires the valve to be opened when the valve is cut off, the normally open (air-to-close) control valve should be selected, otherwise, the normally-closed (air-to-open) control valve should be selected.

Encoder|Transmitter|Soft starter|Power supply|VFD|Light curtain|Servo products|Human-machine interface|Solenoid valve|Cylinder|Actuator|Flow meter|Transformer|Thyristor|Sensor|Deceleration drive gearbox reducer|Linear guide|Circuit breaker|Refrigeration compressorAll industrial products of okplazas are purchased from the original factory or formal channels of agents to ensure the original authenticity, which perfectly solves the problem of industrial product sample procurement and small-batch procurement for the majority of engineers and purchasing personnel.

This is just a superficial plan. If the process requires gas cutoff, power cutoff, and signal cutoff three-break protection, the regulating valve needs to be equipped with some accessories to form a protection system to meet the control requirements. These accessories mainly include position maintaining valves, solenoid valves and gas tanks. The following are two holding schemes for single-acting pneumatic membrane control valves and double-acting pneumatic control valves.