1. In terms of structural mechanism

The hard seal of a ball valve is a seal between metals, and the sealing ball and valve seat are both made of metal. The machining accuracy and process are relatively difficult, generally used at high temperatures or high pressures, suitable for media with particles. Soft seal is a seal between metal and non-metal, such as nylon/tetrafluoroethylene, with the same manufacturing standards.

2. On the sealing material

Soft and hard sealing refers to the sealing material of the valve seat. Hard sealing is made by precision machining of the valve seat material to ensure the accuracy of the fit with the valve core (ball), generally including stainless steel alloy steel and hard alloy. Soft seal refers to the non-metallic sealing material embedded on the valve seat. Due to the elasticity of the soft sealing material, the requirements for machining accuracy are relatively low compared to hard seals.

3. In terms of manufacturing process

Due to the complex working environment of many chemical and mechanical industries, which are characterized by high temperature and pressure, high friction resistance of the medium, and strong corrosiveness, with the advancement of technology, the use of various materials has become better, and processing and other aspects can keep up, making hard sealed ball valves widely promoted. In fact, the principle of hard sealed ball valves is the same as that of soft sealed valves, except that due to the sealing between metals, the hardness relationship between metals, as well as the working conditions and the medium used, need to be considered. Generally, hardening treatment is required, and the ball and valve seat need to be continuously ground to achieve sealing. Hard sealed ball valves have a long production cycle and complex processing, so the price of hard sealed ball valves is much higher

4. In terms of usage conditions

Soft seals can generally achieve high sealing, while hard seals can vary in height according to requirements; Soft seals need to be fire-resistant because at high temperatures, the material of the soft seal may leak, while hard seals do not have this problem; Hard seals can generally achieve high pressure, while soft seals cannot; Soft seals cannot be used in some situations due to the problem of the flowing medium (such as some corrosive media). As for manufacturing, there is not much difference between the two, mainly the difference in valve seat. Soft seals are non-metallic, while hard seals are metallic.

5. In terms of equipment selection

The selection of soft and hard sealed ball valves is mainly based on the process medium, temperature, and pressure. Generally, if the medium contains solid particles or has wear or temperature higher than 200 degrees, a hard seal is selected. If the diameter is greater than 50 and the valve pressure difference is large, the opening torque of the valve should also be considered. When the torque is large, a fixed hard sealed ball valve should be selected. Regardless of whether it is a soft or hard seal, its sealing level can reach level 6.