Due to some similarities in appearance between globe valves and gate valves, as well as their ability to cut off in pipelines, many circle members who do not have much contact with valves may confuse the two. In fact, if carefully observed, the difference between globe valves and gate valves is quite significant.
Firstly, in terms of valve structure, the gate valve can rely on medium pressure to tightly close the sealing surface, thereby achieving the effect of no leakage. When opening and closing, the sealing surface of the valve core and valve seat always contacts and rubs against each other, so the sealing surface is prone to wear. When the gate valve is close to closing, the pressure difference between the front and rear of the pipeline will significantly increase, causing more severe erosion of the sealing surface.
The structure of a gate valve is more complex than that of a globe valve. From the appearance, under the same caliber, the gate valve is taller than the globe valve, and the length of the globe valve structure is longer than the gate valve. In addition, there are two types of gate valves: open stem and non rising stem.
The sealing surface of the shut-off valve is a small trapezoidal side of the valve core (depending on the shape of the valve core); The gate valve is sealed by the outer edge of the gate plate.
In terms of specific functions, the shut-off valve can be used for both cut-off and rough flow regulation. The shut-off valve is an S-shaped flow channel, so the fluid resistance is relatively high, and the opening and closing stroke is short, about 1/4 of the valve seat diameter. When the gate valve is fully opened, the medium flow resistance in the valve body channel is almost zero. The travel of the gate valve is slightly larger than the diameter of the valve and pipeline, so the opening and closing time is long.
Finally, there is a difference in the installation of the globe valve and the gate valve. The effect of the gate valve flow direction is the same in both directions, and there is no requirement for the inlet and outlet direction during installation. The medium can flow in both directions.
Globe valves need to be installed strictly in accordance with the direction indicated by the arrow on the valve body. There is also a clear regulation regarding the inlet and outlet directions of globe valves. According to the "Three Chemicals" regulations for valves in China, the flow direction of globe valves is always from bottom to top.