Mỗi loại van, dù là về ngoại hình, kết cấu, hoặc chức năng, thể hiện sự khác biệt. Tuy nhiên, there are some similarities in the appearance of globe valves and gate valves, both serving the function of interrupting the flow in pipelines. This often leads to confusion among those less familiar with valve types.
This article aims to elucidate the distinctions between van cầu Và van cổng.
I. Structural Differences
Considerations for limited installation space:
Globe valves achieve tight closure by tightly sealing with the pressure of the medium, preventing leakage.
As the gate valve’s core and seat sealing surfaces constantly make contact and friction during opening and closing, these surfaces are prone to wear. Van cổng, especially when nearing closure, experience a significant pressure differential between the pipeline’s upstream and downstream, exacerbating wear on the sealing surfaces.
Gate valves have a more complex structure. Visually, for the same diameter, gate valves are taller than globe valves, and globe valves are longer than gate valves.
Gate valves can be categorized into rising stem and non-rising stem types, whereas globe valves do not have this distinction.
II. Operating Principles
Globe valves employ a rising stem mechanism for opening and closing. This means that turning the handwheel causes both the handwheel and stem to rotate and move up and down together.
Van cổng, Mặt khác, involve turning the handwheel to make the stem move up and down, while the position of the handwheel itself remains unchanged.
Flow rates differ; gate valves require either fully open or fully closed positions, whereas globe valves do not.
III. Performance Differences
Globe valves can be used for both interruption and flow regulation. They exhibit significant fluid resistance, making opening and closing more labor-intensive. Tuy nhiên, due to the short distance between the valve disk and sealing surface, their travel distance is shorter.
Van cổng, limited to fully open or fully closed positions, offer almost zero fluid flow resistance when fully open. Kết quả là, opening and closing gate valves require less effort. Tuy nhiên, the distance between the gate and sealing surface is greater, leading to longer opening and closing times.
IV. Installation and Flow Direction
The effectiveness of gate valves is the same in both flow directions, and there are no specific requirements for the installation of inlet and outlet directions. The medium can flow in both directions.
Globe valves must be installed strictly according to the direction indicated by the arrow on the valve body. In China, there is a clear stipulation in the valve “three deliveries” regulation that the flow direction of globe valves must be from top to bottom.
Globe valves are installed with the inlet at the bottom and the outlet at the top, creating a noticeable deviation from a horizontal line in appearance.
Gate valves have a flow path on a horizontal line, and the travel of gate valves is greater than that of globe valves.
V. Sealing Aspects
Globe valves seal on the small trapezoidal side of the valve core (depending on the shape of the valve core). If the valve core falls off, it is equivalent to closing the valve (though it may not be tightly closed under high pressure, the check valve effect is still good).
Gate valves rely on the side of the valve core gate for sealing, with sealing effects not as good as globe valves. If the valve core falls off, it will not close the valve as effectively as in the case of globe valves.