What is a generally accepted method for verifying a manual valve is fully closed?

The generally accepted method for verifying that a manual valve is fully closed involves attempting to turn the valve hand wheel. This is effective because it gives the operator a direct mechanical indication of the valve's position. When the valve is fully closed, the resistance encountered when attempting to turn the hand wheel will signify that the valve is no longer allowing fluid to flow through.

This method is widely used because it engages the operator in a physical check that can be easily assessed without additional equipment. While listening for sound changes, looking for visual signs of leakage, or monitoring a pressure gauge can provide useful information about valve operation and system integrity, they do not offer the same direct confirmation of a valve's closed status as physically attempting to turn the valve does. The mechanical feedback of feeling resistance is definitive in assuring the operator that the valve has indeed reached its closed position.