The difference between soft and hard seal gate valves

Soft seal gate valve and hard seal gate valve are commonly used devices to regulate and intercept flow. Both of them have good sealing performance and a wide range of use. They are one of the products purchased by customers. Some novice buyers may wonder, the same gate valve, what are the specific differences between them?

Soft seal is the seal between metal and non-metal, hard seal is the seal between metal and metal. Soft seal gate valve and hard seal gate valve are sealing materials, hard seal is precision machining with valve seat material, to ensure the accuracy of the valve core (ball), usually stainless steel and copper. Soft seal refers to the sealing material embedded on the seat is non-metallic material, because the soft seal material has a certain elasticity, so the machining accuracy requirements are relatively lower than that of the hard seal. Let's take a look at the differences between soft seal gate valves and hard seal gate valves.

First, sealing materials

1. The sealing materials are different. Soft seal gate valves are usually rubber EPDM and NBR materials. Hard seal gate valves use stainless steel and other metals.

2. Soft seal: one side of the sealing pair is metal material, and the other side is elastic non-metallic material, which is called "soft seal". This kind of gate valve has good sealing effect, but it is not resistant to high temperature, easy to wear, and poor mechanical properties. Such as: ductile iron + rubber, etc.

3. Hard seal: both sides of the hard seal are metal materials, or other hard materials. This type of gate valve has poor sealing, but high temperature resistance, wear resistance and good mechanical properties.

Copper gland gate valve

Two, the construction process

The task environment of the machinery industry is complex, many are ultra-low temperature and low pressure, medium resistance is large, corrosive, and now the technological progress, makes the hard seal gate valve popular.

To CONSIDER THE RELATIONSHIP BETWEEN THE HARDNESS of the metal, in fact hard seal gate valves and soft seal gate valves, the body need to be hardened. Hard seal gate valves have a longer production cycle.

Three, the use of conditions

1, soft seal can achieve zero leakage, hard seal can be adjusted according to requirements;

2, soft seal may leak at high temperature, need to pay attention to fire prevention; Hard seals do not leak at high temperatures. The hard seal of the emergency shut-off valve can be used at high pressure, while the soft seal cannot be used.

3, for some corrosive media, soft seal can not be used, can use hard seal;

4, at very low temperature, soft sealing material will leak, hard sealing has no such problem;

Four, equipment selection

The sealing level of the two can reach six levels, usually according to the process medium, temperature and pressure to choose the appropriate gate valve. General medium containing solid particles or wear, or the temperature exceeds 200 degrees when the best choice of hard seal. If the torque of the cut-off valve is large, the fixed hard seal gate valve should be selected.

Five, the difference in service life

The advantage of soft seal is good sealing, the disadvantage is easy to aging, wear and tear, short life. The service life of hard seal is longer, and the sealing performance is worse than that of soft seal. The two can complement each other.