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Discs in gate valves can be classified into several categories:

 

1. Wedge single disc

Compared with elastic gate valves, wedge single disc gate valves have simple structure;

Under high temperature, the sealing is poorer than that in elastic gate valves or double discs gate valves;

The valves are suitable for media which coking easily.

 

2. Elastic disc 

Elastic disc is a kind of particular types of wedge single disc. Compared with wedge gate valves, elastic gate valves have good sealing under high temperature. And the disc is not stuck easily after being heated. Elastic disc gate valves are suitable for steam, high temperature oil and oil gas. The valves are also suitable for position requiring frequent on-off. However, elastic disc gate valves are not suitable for media which coking easily. 

 

3. Double discs 

Double discs gate valves have better sealing than wedge gate valves. If rake angle of sealing does not coordinate with seat exactly, the valves can still maintain good sealing.

When sealing face of disc is wear, just change metallic gasket at the top of centering of ball to one having high thickness. In general, bead welding and grinding sealing face are unnecessary. 

Double discs gate valves have more parts than other types of gate valves.

Besides steam, oil and other media, double discs gate valves are also suitable for media which can cause wearing to sealing face. The valves cannot be used for media which coking easily. 

 

4. Parallel disc

Parallel disc gate valves have worse sealing than other types of gate valves.

The valves are fit for media having low temperature and pressure.

Processing and maintenance of sealing face on disc and seat are easier than other types of gate valves.