Globe valves, gate valves, butterfly valves, check valves and ball valves are all indispensable control components in various pipeline systems. Each valve is different in appearance, structure and even functional use. However, the globe valve and the gate valve have some similarities in appearance, and both have the function of cutting off in the pipeline, so many friends who have little contact with the valve will confuse the two. In fact, if you look closely, the difference between a globe valve and a gate valve is quite big.
When the installation space is limited, attention should be paid to the selection. The gate valve can be tightly closed with the sealing surface by the medium pressure, so as to achieve the effect of no leakage. When opening and closing, the valve core and the valve seat sealing surface are always in contact and rub against each other, so the sealing surface is easy to wear. When the gate valve is close to closing, the pressure difference between the front and rear of the pipeline is large, which makes the sealing surface wear more seriously. The structure of the gate valve will be more complicated than that of the globe valve. From the perspective of appearance, the gate valve is taller than the globe valve and the globe valve is longer than the gate valve under the same diameter. In addition, gate valves are divided into open rods and dark rods. The shut-off valve does not.
When the globe valve is opened and closed, it is a rising valve stem type, that is to say, when the handwheel is turned, the handwheel will rotate and lift together with the valve stem. The gate valve rotates the handwheel to make the valve stem move up and down, and the position of the handwheel itself remains unchanged. Flow rates vary, gate valves require fully open or fully closed, and globe valves do not. Globe valves have specified inlet and outlet directions; gate valves do not have requirements for inlet and outlet directions. In addition, the gate valve has only two states: fully open or fully closed, the gate opening and closing stroke is large, and the opening and closing time is long. The movement stroke of the valve plate of the globe valve is much smaller, and the valve plate of the globe valve can stop at a certain place during the movement for flow regulation. The gate valve can only be used for truncation and has no other functions.
The globe valve can be used for both cut-off and flow regulation. The fluid resistance of the globe valve is relatively large, and it is more laborious to open and close, but because the distance between the valve plate and the sealing surface is short, the opening and closing stroke is short. Because the gate valve can only be fully opened and fully closed, when it is fully opened, the medium flow resistance in the valve body channel is almost 0, so the opening and closing of the gate valve will be very labor-saving, but the gate is far away from the sealing surface, and the opening and closing time is long.
The gate valve has the same effect in both directions. There is no requirement for the direction of the inlet and outlet, and the medium can flow in both directions. The globe valve needs to be installed in strict accordance with the direction marked by the arrow on the valve body, and the flow direction of the globe valve shall be from top to bottom. The shut-off valve is low in and high out, and it is obvious that the pipeline is not on a horizontal line from the outside. The gate valve flow channel is on a horizontal line. The stroke of the gate valve is larger than that of the globe valve.
From the point of view of flow resistance, the flow resistance of the gate valve is small when it is fully opened, and the flow resistance of the globe valve is large. The flow resistance coefficient of ordinary gate valves is about 0.08~0.12, the opening and closing force is small, and the medium can flow in two directions. The flow resistance of ordinary globe valves is 3-5 times that of gate valves. When opening and closing, it needs to be forced to close to achieve sealing. The valve core of the globe valve only contacts the sealing surface when it is completely closed, so the wear of the sealing surface is very small. Due to the large flow resistance, the globe valve that needs an actuator should pay attention to the adjustment of the torque control mechanism.