I would like to ask the experts about solenoid valves and emergency shut-off valves
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On Pid diagrams, Mov and Xzv appear frequently; experienced engineers say they refer to emergency shut-off valves and solenoid valves. Could someone explain the difference between them? Can’t they all be controlled via a central control switch, with only two states: on and off?
MOV is a valve operated by a motor
And XZV should be a pneumatic shut-off valve; this is the difference between the two
Since it’s a cut-off valve, of course it only has two positions: on and off~
MOV stands for MOTOR OPERATED VALVE – a valve driven by an electric motor; it is also known as an electric valve, and requires an electric actuator to be installed. XZV is generally defined as a cut-off valve; it is not specified whether it is pneumatic or electric, but it usually refers to a pneumatic actuator, as electric valves are generally called MOVs.
MOV stands for MOTOR OPERATED VALVE – a valve driven by an electric motor; it is also known as an electric valve, and requires an electric actuator to be installed. XZV is generally defined as a cut-off valve; it is not specified whether it is pneumatic or electric, but it usually refers to a pneumatic actuator, as electric valves are generally called MOVs.
Emergency shut-off valves are generally designed to be opened by external forces (such as air pressure, electromagnetic force, oil pressure, etc.) during normal operation, and to remain in that open state. In the event of an emergency, they close (or open, depending on the requirements of the interlocking mechanisms) by their own force (usually through spring return). In this way, even if the external power source is lost, the valve can still meet the requirement for emergency shutdown (or opening for venting). The commonly used shut-off valves are generally air supply valves, whose activation and deactivation are controlled by small solenoid valves; that is, a 24V signal from the DCS or ESD is used to control the solenoid valve, which in turn controls the air supply. The air supply then drives the valve element to move through a cylinder or diaphragm. The emergency shut-off valve is designed for safety purposes and is not intended for any other use. Under normal conditions, it ensures that the valve remains fully open, allowing the flow of fluid in the pipeline to continue; in an emergency, however, it can shut off the flow of material, thereby providing a safety mechanism. As such, it has only two states. In some cases, isolation valves are equipped with positioners and used as control valves; however, this causes wear on the valve core during normal use. Once the wear reaches a certain level, the valve can no longer achieve a complete isolation, which is not conducive to ensuring safety. Important chain cut-off valves must not be used for other purposes.
The explanation on emergency shutdown upstairs was very detailed! I learned it!