Compared with the gate valve, the globe valve has the advantages of simple structure, good sealing performance and convenient manufacturing and maintenance; the disadvantage is that the liquid resistance is large, and the opening and closing forces are large.
The difference between the gate valve and globe valve
1. Different structure. The gate valve is more complex than the globe valve and has a large height. The gate valve is shorter and higher than the globe valve. In particular, the rising stem gate valve requires a high space, which should be noted in the case of limited installation space.
2. The sealing surface is different. When the gate valve is opened and closed, the sealing surface of the gate and the valve seat always contact and rub against each other, so the sealing surface is easy to wear, especially when the valve is close to the closed state, the pressure difference between the gate and the front is large, and the sealing surface wears more. When the valve disc of the globe valve is in the open state, its valve seat and the valve sealing surface are no longer in contact, so its sealing surface is mechanically worn less, but if the medium contains solid particles, it is easy to damage the seal surface.
3. The flow resistance is different. When the gate valve is fully open, the entire flow passage is straight through. At this time, the pressure loss of the medium operation is the smallest. Compared with the globe valve, its main advantage is that the fluid flow resistance is small, and the flow resistance coefficient of the ordinary gate valve is about 0.08~0.12. The drag coefficient of the globe valve is approximately 3.5 to 4.5.
4. The flow direction is different. When the globe valve valve is installed, the medium can enter from the bottom of the spool and enter from above. The advantage of the medium entering from below the valve plug is that the packing is not under pressure when the valve is closed, the life of the packing can be extended, and the packing can be replaced with the pressure in front of the valve. The disadvantage of the medium entering from the bottom of the valve core is that the driving torque of the valve is relatively large, about 1.05~1.08 times of the upper entry, the axial force of the valve stem is large, and the valve stem is easy to bend. For this reason, the medium enters from below, generally only for small-diameter globe valves (below DN50), and the cast steel globe valve above DN200 use the medium to flow in from above. Electric globe valve generally uses a medium to enter from above. The disadvantage of the way the medium enters from above is exactly the opposite of the way it enters below. The flow direction of the gate valve is the same from both sides.
5. The itinerary is different. The stroke of the gate valve is larger than that of the globe valve.
6. The maintenance process is different. The maintenance of the gate valve is not suitable for on-site pipelines, and the valve seat and disc of most of the globe valve valves can be replaced on the line without removing the entire valve from the pipeline. This is where the valve and pipeline are welded together. It is very suitable.