I have a question regarding the on-air and off-air modes
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1. I have a question for everyone: does the accident condition indicated by the red line in the diagram refer to a situation where the signal or air supply to the control valve is interrupted? Or are other accident scenarios also taken into consideration? 2. I asked someone a question today, and they told me how to consider whether the system should be in the open or closed state during a fire accident; is the operating condition during a fire also taken into account when deciding between an open or closed state? How should it be considered?
In short, in the event of a failure or other accidents such as fires, it is sufficient to decide whether the valve should be in an open or closed position to protect the safety of equipment and personnel. In most cases, it is relatively easy to make a choice between the two options; decide whether to use a gas-actuated or gas-shut-off mechanism based on the actual circumstances
In fact, both questions were answered upstairs; it’s not the paragraph that talks about a disruption in the air supply and so on. For all types of faults, what leads to valve failure is indeed a disruption in the air supply, including situations such as shutdown mode. In other words, after considering everything, it needs to be determined what state the valve should be in when a fault occurs~~
Taking process safety and equipment protection into comprehensive consideration,
\"Gas open\" means ventilation is enabled, while \"gas closed\" means it is disabled; \"gas closed\" is the exact opposite. It depends on your process requirements – whether it should be turned on or off in an emergency situation. If you need to turn it on during a fire, then choose the gas shut-off valve.
The fault condition of the control valve refers to the state when there is a problem with the air supply.
The fault position of a control valve refers to the position it is in when there is a problem with the air supply; generally, a valve that closes in case of a fault is actually an air-operated valve, and a signal fault also results in the valve being in the closed position. But there are exceptions as well, though they are rare; I heard an instrument design expert say that he had encountered one designed by a foreign design institute.
It depends on the medium in question. In the event of a fire, if that medium enters the area and serves to dilute the flames, isolate them, or reduce their temperature, then an air shut-off should be used; if the medium itself is flammable or acts as a fuel, then an air supply should be enabled
An accident condition may occur when a key device or a process parameter in this section experiences a significant fault or abnormality. In such cases, regarding this valve, it is necessary to determine whether the internal medium should continue to be delivered to this section or device, or if it should be stopped. If delivery is to continue, then air-operated shutdown should be used; according to the requirements, the valve can either be opened fully or kept in its current position. The opposite applies in the other case.
All accidents and special situations should be taken into consideration to ensure the safety of equipment and personnel.
It refers to whether you want the control valve to be closed or open in the event that the signal or air supply to the control valve is interrupted In the absence of air supply, the air-on valve will close immediately, while the air-off valve will open immediately.