What is the difference between globe valve and gate valve?

The valve is a control component in the fluid delivery system, with the functions of cut-off, regulation, diversion, prevention of backflow, pressure stabilization, diversion or overflow pressure relief. Valves for fluid control systems, from simple cut-off valves to extremely complex automatic control systems used in a variety of valves, its varieties and specifications are quite numerous.

Globe valves, gate valves, butterfly valves, check valves and ball valves, etc. These valves are now indispensable control components in various piping systems. Each valve is different in appearance, structure and even functional use. However, there are some similarities between the cut-off valve and the gate valve in appearance, and both have the function of cutting off in the pipeline. Therefore, there will be many friends who have little 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 quite large.

1. Structure

In the case of limited installation space selection should pay attention. The gate valve can rely on the medium pressure tightly and the sealing surface closed, so as to achieve the effect of no leakage. When the opening and closing of the valve core and valve seat sealing surface always contact and friction, so the sealing surface is easy to wear, the gate valve is close to close, the pipeline before and after the pressure difference is very large, so that the sealing surface wear is more serious.

2. Working principle

When the cut-off valve is opened and closed, it is a rising stem type, that is to say, when the handwheel is turned, the handwheel will rotate and lift together with the stem. The gate valve is to rotate the hand wheel, so that the valve stem to do the lifting movement, the hand wheel itself position unchanged. The flow rate is different, the gate valve is required to be fully open or fully closed, and the stop valve is not required. Globe valves have specified import and export directions; gate valves have 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, opening and closing time is long. The movement of the valve plate of the cut-off valve is much smaller, and the valve plate of the cut-off valve can be stopped in a certain place during the movement and used for flow regulation. And the gate valve is only do cut off use, no other function.

The structure of the gate valve will be more complex than the globe valve, from the appearance point of view, the same caliber, the gate valve is higher than the globe valve, the globe valve is longer than the gate valve. In addition, the gate valve has bright and dark rod. The shutoff valve does not.

3. Performance difference

The cut-off valve can be used as a cut-off valve and can be used as a flow regulator. The fluid resistance of the cut-off valve is relatively large, and it is more laborious when opening and closing, 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 opened and fully closed, when it is fully opened, the flow resistance of the medium 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.

4. Installation and flow direction

The effect of the gate valve flowing in both directions is the same. There is no requirement for the installation of the import and export direction, and the medium can flow in both directions. The cut-off valve needs to be installed in strict accordance with the direction marked by the arrow of the valve body. There is also a clear stipulation on the import and export direction of the cut-off valve. The flow direction of the cut-off valve in our country is from top to bottom.

The cut-off valve is low and high, and it is obvious from the appearance that the pipeline is not on the horizontal line of the first phase. The flow path of the gate valve is on a horizontal line. The stroke of the gate valve is larger than that of the stop 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 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 stop valve is 3-5 times that of gate valve (public number: pump housekeeper). When opening and closing, forced closing is required to achieve sealing. The valve core of the globe valve is completely closed before contacting the sealing surface, so the wear of the sealing surface is very small. Due to the large flow force, the globe valve of the actuator should pay attention to the adjustment of the torque control mechanism.

There are two ways to install the stop valve. One is that the medium can enter from below the valve core. The advantage is that the packing is not under pressure when the valve is closed, which can prolong the service life of the packing and replace the packing when the pipeline in front of the valve is under pressure. The disadvantage is that the driving torque of the valve is relatively large, which is about twice that of the upper flow. The axial force of the valve stem is large and the valve stem is easy to bend. Therefore, this method is generally only applicable to small diameter valve (DN50 below),DN200 above the valve are selected from the top of the flow of media. (Electric globe valve is generally the use of media from above to enter the way.) The disadvantage of the medium entering from above is exactly the opposite of the entering from below.

5. On the seal

The sealing surface of the stop valve is a small trapezoidal side of the valve core (depending on the shape of the valve core). Once the valve core falls off, it is equivalent to closing the valve (if the pressure difference is large, of course it is not tightly closed, but the anti-reverse effect is good). The gate valve is sealed by the side of the valve core gate plate. The sealing effect is not as good as that of the stop valve.