What causes valve stem seizure or thread damage makes the valve difficult to open and close?
A) Excessive force when opening or closing a valve
B) Throttling a valve that is not designed for throttling
C) Failure to clean and lubricate valve stems
D) Improper closing of a valve on a high-pressure line
Answer: C
Explanation: A) Incorrect. Excessive force when opening or closing a valve can cause leakage and make the valve difficult to open or close.
B) Incorrect. Throttling a valve that is not designed for throttling can cause damage to the valve to the point that it will not seat and stop flow when closed.
C) Correct. Failure to clean and lubricate valve stems causes valve stem seizure or thread damage makes the valve difficult to open and close.
D) Incorrect. Improper closing of a valve on a high-pressure line can cause a leak in the environment.
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