THE DIFFERENCE BETWEEN STOP VALVE AND GATE VALVE

The development of economy and science and technology has been inseparable from the work of many equipment. For example, in the process of regulating flow, the role of valves is very prominent. With the use and development of valves, the types and models of valves are gradually increasing, such as ball valves, check valves, forged steel valves, butt weld fittings and so on. Gate valve and stop valve are two of the most representative products. What are the differences between gate valve and stop valve?

 

 

1. Structurally

In case of limited installation space, attention shall be paid to the selection:

The gate valve can be tightly closed with the sealing surface depending on the medium pressure, so as to achieve the effect of no leakage. When the valve core and the sealing surface of the valve seat are always in contact and rub with each other when opening and closing, so the sealing surface is easy to wear. When the gate valve is close to closing, the pressure difference between the front and back of the pipeline is large, which makes the sealing surface wear more seriously.

 

The structure of the gate valve is more complicated than that of the stop valve. From the perspective of the appearance, the gate valve is higher than the stop valve, and the stop valve is longer than the gate valve. In addition, the gate valve is divided into a bright rod and a dark rod, while the stop valve does not.

 

 

2. Working Principle

When opening and closing the stop valve, the valve stem is raised, that is, when the hand wheel is turned, the hand wheel will rotate and lift along with the valve stem. The gate valve rotates the hand wheel to make the valve stem move up and down, and the position of the hand wheel itself does not change.

 

The flow is different, the gate valve requires full open or full close, but the stop valve does not. Stop valves have prescribed inlet and outlet directions, and gate valves do not have inlet and outlet direction requirements.

 

 

3. Performance Difference

The stop valve can be used for both shut-off and flow adjustment.  The flow resistance of the stop valve is relatively large, and it is laborious to open and close. However, the distance between the valve plate and the sealing surface is short, so the opening and closing stroke is short.

 

The gate valve can only be fully opened and closed. And when it is fully opened, the medium flow resistance in the valve channel is almost 0, so it is very labor-saving to open and close the gate valve. However, the distance between the valve plate and the sealing surface is long, and the opening and closing time is long.

 

 

4. Installation and Flow Direction

The flow direction of gate valve has the same effect in both directions. There is no requirement for the installation of inlet and outlet direction, and the medium can flow in two directions. The stop valve should be installed in strict accordance with the direction indicated by the arrow of the valve body. There is a clear regulation on the direction of the inlet and outlet of the stop valve.

 

The stop valve is low-in and high-out. From the appearance, it is obvious that the pipeline is not on the same phase horizontal line. The gate valve flow path is on a horizontal line. The stroke of gate valve is larger than that of stop valve.

 

There are two ways to install the stop valve. One is that the medium can enter from the bottom of the valve core. The advantage is that the packing is not under pressure when the valve is closed, which can extend the service life of the packing. And the packing can be replaced when the pipeline in front of the valve is under pressure. The disadvantage is that the driving torque of the valve is large, which is about 1 times of the upper flow. And the axial force on the valve rod is large, so the valve rod is easy to bend.

 

Therefore, this method is generally only applicable to small caliber stop valves (below DN50). The stop valves above DN200 adopt the way of medium flowing in from above. The electric stop valve generally adopts the way of medium entering from above.

 

 

5. Sealing

The sealing surface of the stop valve is a small trapezoid side of the valve core. Once the valve core falls off, it is equivalent to the valve closing. The gate valve is sealed by the side of the valve core ram. The sealing effect is not as good as the stop valve, and the valve core falling off will not be equivalent to the valve closing as the stop valve.

 

 

Through the analysis of the above content, we can further understand the difference between the two. With the development of economy, the demand of many industries is also increasing. Choosing the right valve may have a very important impact on the work, such as ball valves for steam, butterfly valves and so on.