The difference between soft and hard seals of ball valves

Structural mechanism
The hard seal of the ball valve is a seal between metal and metal, and the sealing ball and the valve seat are both metal. Machining accuracy and technology are relatively difficult, and it is generally used on high pressure, usually above 35MPa. Soft seal is the seal between metal and non-metal, such as nylon tetrafluoroethylene, the manufacturing standard is the same.
sealing material
The soft and hard seal refers to the sealing material of the valve seat. The hard seal is precisely processed with the valve seat material to ensure the matching accuracy with the valve core (ball). Generally, there are stainless steel and copper. Soft seal means that the sealing material inlaid on the valve seat is non-metallic material. Because the soft seal material has certain elasticity, the processing precision requirement is lower than that of the hard seal.
Manufacturing process
Due to the complex working environment of 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 advanced, the use of various materials is better, and processing and other aspects can be compared with On, so hard-sealed ball valves are widely promoted.
In fact, the principle of the hard-sealed ball valve is the same as that of the soft-sealed ball valve, 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 to be used. Generally, hardening treatment is required, and continuous grinding between the ball and the valve seat is required to achieve sealing. Hard-sealed ball valves have a long production cycle and complex processing, and it is not easy to make hard-sealed ball valves.
Conditions of use
Soft seals can generally achieve high sealing, 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, while hard seals do not have this problem; hard seals Generally, high pressure can be achieved, but soft seals cannot; soft seals cannot be used in some occasions due to the problem of the flowing medium (such as some corrosive media); hard-sealed valves are generally more expensive than soft-sealed valves. As for manufacturing, there is not much difference between the two, the main difference is the difference in the valve seat, the soft seal is non-metallic, and the hard seal is metal.
on equipment selection
The selection of soft and hard seal ball 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 better to choose a hard seal. The diameter of the valve is greater than 50. The pressure difference is large and the opening torque of the valve is also considered. When the torque is large, fixed and hard-sealed ball valves should be selected, and the sealing level can reach level 6 regardless of soft or hard seals.