Cut-off valve fault condition
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Are the consequences of an air supply failure and a power supply failure for a shut-off valve the same?
Not necessarily; it depends mainly on how it’s designed
First of all, it is necessary to clarify what the meaning of a \"gas cut-off valve\" is. These types of valves are characterized by being either air-operated for opening or air-operated for closing; they may be referred to by different names. The driving force that controls the pneumatic valve is the instrument air supply, and the solenoid valve is what controls the air supply to the valve. Air source failures can be determined directly from the pressure gauge. The energization and de-energization of the solenoid valve can be tested by manually switching the valve body, or it can also be tested using the energized/de-energized method.
This is not necessarily the case. In the case of a gas supply failure, opening the valve results in either an open or closed state, while in the case of a power supply failure, it depends on the condition of the solenoid valve; as a result, the outcomes may differ from those in the case of a gas supply failure.
It’s different; the location where power is cut off depends on the type of actuator
These are two types of faults. Different causes lead to different ways of handling faults.
The common type of fault is a gas supply issue, which requires the valve to be opened, closed, or kept in its current position
It’s different; in the case of a single-cylinder valve, the valve position in the event of a gas supply failure is determined by the spring. The location of the power failure valve depends on the piping of the solenoid valve. Also, in the case of a two-cylinder valve: if there is a problem with the air supply, the valve position remains unchanged; whereas in the event of a power supply issue, the valve position still needs to be determined based on the piping connected to the solenoid valve.
Fault conditions such as power loss and gas supply interruption can be addressed through the use of gas circuit components, in accordance with the design of the process conditions.
Consider the safety requirements of the process, whether the valve should be in the open or closed position in case of an accident; determine what state the value set in the SIS corresponds to; and also decide on the type of valve to use – air-operated, pressure-operated, or double-acting