Structure
Gate valves can be tightly closed depending on the medium pressure, thus achieving non-leakage. When the valve is opened and closed, the sealing surfaces of the disc and the seat always contact and rub against each other, so the sealing surfaces are easy to wear. When
the gate valve is about to close, the difference between the upstream pressure and downstream pressure is very large, which makes the sealing surfaces wear more seriously.
The structure of
the gate valve is more complicated than that of
the globe valve. Judging from their appearances, under the same caliber,
the gate valve is higher than
the stop valve and
the stop valve is longer than
the gate valve. In addition,
gate valves are divided into rising stem
gate valves and non-rising stem
gate valves while
the globe valve has no such difference.
Working Principle
When the globe valve is opened and closed, it is of the rising stem type, that is to say, when the handwheel is rotated, it will be rotated and moved up and down together with the valve stem. The handwheel of the gate valve is rotated to make the stem move up and down, and the position of the handwheel itself remains unchanged. And the flow rate is different. Gate valves are required to be fully opened or closed while stop valves are not required. Globe valves have specified inlet and outlet directions, but gate valves have no such provision.
In addition, the gate valve has only two states of full opening and full closing. The gate has long opening and closing stroke and long opening and closing time. The movement stroke of the disc of the globe valve is much smaller, and the disc of the stop valve can stop at a certain place in the movement for flow regulation. Gate valves are used to shut off the flow of liquids rather than for flow regulation.
Performance
Globe valves can be used for cutting off media flow and regulating flow in the pipeline. The fluid resistance of the globe valve is relatively large and it takes a lot of effort to open and close the valve, but the open-close stroke is short because the disc has a short distance from the sealing surface.
The gate valve can only be fully opened and closed. When it is fully opened, the medium flow resistance in the valve body passage is almost zero, so the opening and closing of the gate valve is very labor-saving, but the gate valve is far away from the sealing surface, and has long on-off time.
Installation and Flow Direction
The effect of the gate valve flowing in both directions is the same. The installation of gate valves is not directional, and the medium can flow in both directions. Globe valves need to be installed in strict accordance with the direction indicated by the arrow on the valve body. There is also an explicit stipulation in the valve industry of our country: the flow direction of stop valves shall be from top to bottom.
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