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How to determine the switch of dark stem gate valve

Posted by Bundor valve
The stem thread of a dark-stem gate valve is inside the body, so the opening and closing status of a dark-stem gate valve cannot be determined by observing the stem position, as is the case with an open-stem gate valve.
gate valve
The opening and closing of gate valve requires the hand wheel to be rotated, which is normally clockwise to be closed and counterclockwise to be opened. Therefore, for the dark stem gate valve installed in the pipeline, its switching state cannot be directly observed by the naked eye, so we can test by rotating the hand wheel.

Dark stem gate valve operating principle

The gate moves up and down in a straight line with the stem, which has threads on it. When turning the stem, the stem moves up and down in a straight line under the action of the nut on the top of the valve and the guide groove on the body, and the stem drives the gate in the same time.The motion direction of the gate is perpendicular to the flow direction of the medium in the pipe.

Because stem threads are inside the body, dark stem gate valves cannot be opened and closed by observing stem position as open stem gate valves do.Under normal circumstances, the open and close state of the dark stem gate valve to turn the stem so far, but in consideration of special conditions, the valve appears locked, in order to ensure the production safety of the pipeline, dark stem gate valve is generally opened to the stem to turn after turning 1~2 turns.