Gas path solution

It is best to understand it in conjunction with the principles of the manufacturing process; it cannot be summarized merely by this diagram alone. Here is a factor regarding the on/off status of the relay and solenoid valve for reference.

This is: a control valve with two cylinders + a positioner. Function of the locking valve: When the air supply pressure falls below a certain value, such as below the minimum air supply pressure required by the positioner, it switches the air circuit and locks the valve position. This valve also requires FC; the power for closing it comes from the air tank, while the command to close it is issued by the operation of the lock valve or solenoid valve (1002). From the perspective of command priority, since the gas cylinder is filled with gas, its pressure drops last. Once the external air supply is lost, the slide valve switches first (simultaneously the positioner loses its air supply), and the valve closes immediately. You can consult regarding the process: In the absence of a gas cylinder, what is the requirement according to the process after the main air supply is lost – should the valve be closed? Lock the position again? If it’s the former, your judgment is correct ； If it is the latter, this gas path does not meet the requirements.

This is an exam question; it cannot be combined with the manufacturing process. :L

This is an exam question; it’s not possible to take the manufacturing process into account

Hehe, if this is supposed to be an exam question, then I won’t take part. It’s hard to say there are any issues with the rigor of the question-posing itself.

Think beyond that: the gas tank is the power source for the \"final shot\", not a signal source. Moreover, we will not consider the factor of air loss from the gas tank. On this basis, we believe that loss of pressure refers to a drop in pressure at the main pipe, and it serves as the \"signal source\" for subsequent actions; therefore, only one safe position can be chosen: to close the valve or to maintain its current position (the question requires closing the valve). If the process indeed requires holding the position first and then closing the valve, then the air pressure setting for holding the position needs to be considered; the setting value that triggers the valve-closing action is generally the minimum operating air pressure of the positioner. The above settings only make sense if the main wind is falling slowly. But in the case of a normal fault, the main air supply is cut off immediately, so the valve is closed right away; there’s no chance for locking to occur. When designing a gas circuit diagram, it is still necessary to understand the requirements for process safety. (What is the question posed in the exam?)

The questions ask about the function of each attachment, the valve positions in interlock mode, and the valve positions in case of a gas supply failure

Yours seems to have the valve interlock set to downward.