1. Small fluid resistance.

2. The external force required for opening and closing is small.

3. The flow direction of the medium is not restricted.

4. When fully open, the sealing surface is less eroded by the working medium than the globe valve.

5. The shape is relatively simple and the casting process is better.

1. The overall size and opening height are large. Installation requires more space.

2. During the opening and closing process, there is relative friction between the sealing surfaces, which is easy to cause scratches.

3. Brass gate valves generally have two sealing surfaces, adding some difficulties to processing, grinding and maintenance.

1. Brass gate valve can be divided into:

1) Parallel brass gate valve: The sealing surface is parallel to the vertical centerline, that is, the brass gate valve with the two sealing surfaces parallel to each other.

Among the parallel brass gate valves, the structure with a thrust wedge is the most common, that is, there is a double-sided thrust wedge between the two gate plates. This brass gate valve is suitable for DN40-300mm low pressure, medium and small diameter brass gate valves. There are also springs between the two gates, the springs can generate a pre-tightening force, which is beneficial to the sealing of the gates.

2) Wedge-type brass gate valve: the sealing surface is at a certain angle to the vertical centerline, that is, the two sealing surfaces are wedge-shaped brass gate valves.

The inclination angle of the sealing surface is generally 2°52', 3°30', 5°, 8°, 10°, etc. The size of the angle mainly depends on the temperature of the medium. Generally, the higher the working temperature, the larger the angle should be taken to reduce the possibility of wedging when the temperature changes.

In the wedge type brass gate valve, there are single gate brass gate valve, double gate brass gate valve and elastic gate brass gate valve.

The single gate wedge type brass gate valve has a simple structure and reliable use, but it requires high precision of the sealing surface angle, and it is difficult to process and maintain, and the possibility of wedging is very high when the temperature changes.

The double gate wedge brass gate valve is widely used in water and steam medium pipelines. Its advantages are: the accuracy of the angle of the sealing surface is low, the temperature change is not easy to cause the phenomenon of wedging, and the gasket can be added to compensate when the sealing surface is worn. However, there are many structural parts of this kind, which are easy to bond in viscous medium and affect the sealing. More importantly, the long-term use of the upper and lower baffles is prone to rust, and the gates are easy to fall off.

The elastic gate wedge type brass gate valve has the advantages of simple structure and reliable use, and can produce a small amount of elastic deformation to compensate for the deviation generated during the processing of the sealing surface angle and improve the manufacturability. has been widely adopted.

2. According to the structure of the valve stem, the brass gate valve can be divided into:

1) Brass gate valve with rising stem: The stem nut is on the bonnet or bracket. When opening and closing the gate, the stem nut is rotated to realize the lifting and lowering of the stem. This structure is beneficial to the lubrication of the valve stem, and the degree of opening and closing is obvious, so it is widely used.

2) Brass gate valve with dark stem: the stem nut is in the valve body and is in direct contact with the medium. When opening and closing the gate, it is realized by rotating the valve stem. The advantage of this structure is that the height of the brass gate valve remains unchanged, so the installation space is small, and it is suitable for brass gate valves with large diameters or limited installation space. This structure should be equipped with an opening and closing indicator to indicate the degree of opening and closing. The disadvantage of this structure is that the valve stem thread is not only unable to lubricate, but also directly eroded by the medium and easily damaged.

If the diameter of the passage in a valve body is different (often the diameter at the valve seat is smaller than the diameter at the flange connection), it is called diameter contraction.

The diameter shrinkage can reduce the size of the parts, the force required for opening and closing is correspondingly reduced, and at the same time, the application range of the parts can be expanded. But after the diameter shrinks. Fluid resistance loss increases.

Under certain working conditions in certain sectors (such as oil pipelines in the petroleum sector), valves with reduced diameters are not allowed. On the one hand, it is to reduce the resistance loss of the pipeline, and on the other hand, it is to avoid obstacles to the mechanical cleaning pipeline after the diameter shrinkage.