Globe valves, gate valves, butterfly valves, check valves and ball valves are all indispensable control components in various piping systems today. Every valve is different in appearance, structure and even functional use. However, the globe valve and the gate valve have some similarities in appearance, and at the same time have the function of truncation in the pipeline, so there will be many friends who do not have much contact with the valve to confuse the two. In fact, if you look closely, the difference between the globe valve and the gate valve is still quite large.
- Structure
In the case of limited installation space, it is necessary to pay attention to the selection of:
The gate valve can be tightly closed with the sealing surface by relying on the medium pressure, so as to achieve the effect of no leakage. When opening and closing, the valve spool and the valve seat sealing surface are always in contact with each other and rub against each other, so the sealing surface is easy to wear, and when the gate valve is close to closing, the pressure difference between the front and back of the pipeline is very large, making the sealing surface wear more serious.
The structure of the gate valve will be more complex than the globe valve, from the appearance point of view, in the case of the same caliber, the gate valve is higher than the globe valve, and the globe valve is longer than the gate valve. In addition, the gate valve is divided into bright rod and dark rod. The globe valve is not.
- Work
When the globe valve is opened and closed, it is a rising stem type, that is to say, the hand wheel is rotated, and the hand wheel will do rotation and lifting movements along with the valve stem. The gate valve is to turn the handwheel, so that the stem does a lifting movement, and the position of the handwheel itself remains unchanged.
Flow rates vary, with gate valves requiring full or full closure, while globe valves do not. The globe valve has a specified inlet and outlet direction, and the gate valve has no import and export direction requirements.
In addition, the gate valve is only fully open or fully closed two states, the gate opening and closing of the stroke is very large, the opening and closing time is long. The valve plate movement stroke of the globe valve is much smaller, and the valve plate of the globe valve can stop at a certain place in motion for flow adjustment. The gate valve can only be used for truncation and has no other function.
- Performance
The globe valve can be used for truncation 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 valve plate is short from the sealing surface, the opening and closing stroke is short.
Because the gate valve can only be fully open and fully closed, when it is fully opened, the resistance of the medium flow 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 plate is far from the sealing surface, and the opening and closing time is long.
- Installation and flow direction
The effect of the gate valve flowing in both directions is the same, and there is no requirement for the inlet and outlet direction of the installation, and the medium can flow in both directions. The globe valve needs to be installed in strict accordance with the direction of the valve body arrow identification, and there is a clear provision on the direction of the import and export of the globe valve, and the flow direction of the globe valve “three to” in China is from top to bottom.
The globe valve is low in and high out, and from the outside there are obvious pipes that are not on a phase level. The gate valve runner is on a horizontal line. The stroke of the gate valve is larger than that of the globe valve.
From the perspective of flow resistance, the flow resistance of the gate valve is small when it is fully open, and the flow resistance of the load stop valve is large. The flow resistance coefficient of ordinary gate valve 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 shut-off valves is 3-5 times that of gate valves. When opening and closing, it is necessary to force the closure to achieve the seal, the valve spool of the globe valve is only in contact with the sealing surface when it is completely closed, so the wear of the sealing surface is very small, because the flow of the main force needs to add the actuator Of the globe valve should pay attention to the torque control mechanism adjustment.
The globe valve has two ways of installation, one is that the medium can enter from below the valve spool, the advantage is that when the valve is closed, the packing is not under pressure, the service life of the packing can be extended, and the work of replacing the packing can be carried out under pressure in the pipeline in front of the valve; the disadvantage is that the driving torque of the valve is large, which is about 1 times that of the upper flow, and the axial force of the valve stem is large, and the valve stem is easy to bend.
Therefore, this method is generally only suitable for small-diameter globe valves (DN50 or less), and the globe valves above DN200 are selected for the way of media flowing in from above. (Electric shut-off valves generally use the medium to enter from above.) The disadvantage of the way media enters from above is exactly the opposite of the way in which it enters below.
- Sealing
The sealing surface of the globe valve is a small trapezoidal side of the valve core (specifically look at the shape of the valve core), once the valve core falls off, it is equivalent to the valve closing (if the pressure difference is large, of course, the shutdown is not strict, but the reverse effect is not bad), the gate valve is sealed by the side of the valve core gate plate, the sealing effect is not as good as the globe valve, and the valve core will not fall off like the globe valve.
Post time: Apr-01-2022