Valve Handle Orientation for Flare Header

What did the HazOp Study report say on this subject?

Cause & Effect and HAZOP are required.

I am an engineer in an oil refinery.

We have the requirement that gate valves related to safety relief lines be mounted with the stem horizontal.

This is so that if the disc would become detached from the stem it would not fall and block the flow path.

You did not give us some of the important information with which we would use to give a proper answer. So I will make the following assumption.

The valves are Gate Valves. Right?

The orientation you are talking about is the orientation of the "Stem" of the Gate valve not the hand wheel itself.

If so then my answer is:

"All Flare system Gate valves SHALL be installed so the Stem is in the horizontal position (never vertical)."

The reason for this is an age old fear that when in the vertical position the disc (of the gate valve) might come free from the stem and fall down to the closed position. If that happened then sure enough there would be a huge relief event and the flare would be blocked.

We all know that Gate valves are designed somewhat different today than they were 75 to 100 years ago and few if any would have this problem but the horizontal only practice persists.

This "Rule" does not effect the stem orientation of any other type of valve (i.e.: Ball, Plug, Orbit, etc.).