Check the difference between flexible soft and hard sealed gate valves

The hard seal is a seal between metal and metal, and the sealing ball and valve seat are both metal. Processing accuracy and process are relatively difficult, generally used in high pressure, usually more than 35MPa. Soft seal is a seal between metal and non-metal, such as nylon \ tetrafluoroethylene, the manufacturing standard is the same.

1. Sealing material

Elastic soft-seal gate valve and hard-seal gate valve are for the sealing material of the valve seat. The hard seal is precision-processed with the seat material to ensure the precision of matching with the valve core (ball), generally stainless steel and copper. Soft sealing means that the sealing material embedded in the valve seat is a non-metallic material. Because the soft sealing material has a certain elasticity, the processing accuracy requirements are relatively low compared to the hard sealing.

Second, the manufacturing process

Due to the complicated working environment in many chemical and mechanical industries, many of them are high temperature and high pressure, the friction resistance of the medium is large, and the corrosion is strong. Now that the technology has improved, the use of various materials is better, and processing can be followed Now, the hard-sealed ball valve has been widely promoted.

Actually, the principle of the hard seal gate valve is the same as that of the soft seal, but because it is a seal between metals, it is necessary to consider the hardness relationship between the metals, as well as the working conditions and the medium used. It is generally required to be hardened, and the ball and the seat must be continuously ground to achieve a seal. The hard seal gate valve has a long production cycle and relatively complicated processing. It is not easy to make a hard seal ball valve.

3. Conditions of use

Soft seals can generally achieve very high seals, while hard seals can be high or low according to requirements; soft seals need to be fireproof, because at high temperatures, the material of soft seals will leak, but hard seals do not have this problem; hard seals Generally, the high pressure can be done, but the soft seal does not work; the soft seal cannot be used in some occasions (such as some corrosive media) due to the problem of the flowing medium; finally, the hard seal valve is generally more expensive than the soft seal. As far as manufacturing is concerned, there is not much difference between the two, mainly because of the difference between the valve seats. The soft seal is non-metallic and the hard seal is metallic.

Fourth, on the equipment selection

The selection of soft and hard seal gate valves is mainly based on the process medium, temperature and pressure. Generally, the medium contains solid particles or has wear or the temperature is higher than 200 degrees. It is best to choose a hard seal. The diameter of the valve is greater than 50. The pressure difference of the valve is large. When the torque is large, the fixed hard seal gate valve should be selected, and the seal level can reach level 6 regardless of the soft and hard seals.