Verifying Throttled Valves

DOE-STD-1036-93

by attempting to turn the valve in the closed direction. The effects of this

are:

C If the valve is closed, attempting to turn the valve in the closed

direction will not effect its position. Closed valves should NOT be

opened for verification to prevent adversely affecting system

integrity, because even a slight opening can pressurize or release

hazardous materials into the downstream piping.

C If the valve is open, the verifier will be able to turn the valve in the

closed direction. Only a slight movement in this direction is needed

to confirm that the valve is open, without affecting the flow or

process. The verifier should then restore the valve to its original

position.

If the valve position is not in accordance with the requirements, the

verifier should NOT operate the valve further, and should notify the

cognizant supervisor.

4.3.2

Verifying Throttled Valves

Some valves are required to be in a throttled position, i.e., intermediate

between fully open and fully closed. Often the procedure for establishing

the throttled position is to close the valve, then count a specific number

of turns in the open direction. If this same action were to be performed

by a verifier, the original positioning would be nullified, constituting no

verification.

If possible, alternate means should be established for verifying throttled

valves. If the position of the valve stem would provide visible indication

of the valve position, the facility may place a label or scribe marks on the