What is a generally accepted method to verify that a manual valve is fully closed on a static piping system in a depressurized condition?

To verify that a manual valve is fully closed in a static piping system under depressurized conditions, attempting to turn the handwheel in the closed direction and observing that there is no movement is a widely accepted practice. This method is effective because it directly assesses the mechanical operation of the valve. If the handwheel does not turn when pressure is applied in the direction of closure, it indicates that the valve is indeed seated and fully closed, preventing any potential leakage.

This method is practical and reliable, especially in a situation where pressure gauges are not providing fluid pressure readings due to the system being depressurized. Listening for hissing sounds, while potentially revealing in specific scenarios (like when a valve is supposed to be closed but is leaking), is not a definitive method of closure verification. Likewise, checking gauge pressure is ineffective if the system is depressurized since there would be no pressure reading to inspect. Visually inspecting the valve position can provide a good initial assessment, but it may not be as conclusive as physically engaging with the valve mechanism to confirm its closed state. Thus, the tactile feedback of using the handwheel method is the most reliable approach in this context.