Answer Posted / bhargav purohit

Hi,
I think your question has it self an answer. Your valve is Air fail to close. Means if there is no Control Air/signal, your valve will be closed .

In running plant condition, Position of valve could be anything according to process.( Fail to open or close depends on process requirement)

Suppose you want maintain a Tank level and safe condition is full tank, then..
1> if you are maintaining level by inlet water flow to tank, your valve should be Fail to open. Means in case of signal failure your valve will open and fill the tank (Safe condition)

2>If you are maintaining level by output flow, then you should select fail to close vale. So in case of failure of control signal, output flow will be closed and tank will be full.

Regards,
Bhargav Purohit

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