1.Structural Mechanism:

Hard sealing is a metal-to-metal seal, where both the sealing ball and valve seat are made of metal. The processing accuracy and technology are more difficult, and it is generally used in high-pressure applications, usually above 35 MPa. Soft sealing is a metal-to-non-metal seal, such as nylon or PTFE, and the manufacturing standards are the same.

2.Sealing Materials:

The difference between resilient soft-seated gate valves and hard-seated gate valves lies in the sealing material of the valve seat. Hard sealing uses precisely machined valve seat material to ensure the fit accuracy with the valve core (ball), typically using stainless steel and copper. Soft sealing refers to the sealing material embedded in the valve seat being a non-metallic material. Because soft sealing materials have a certain elasticity, the processing accuracy requirements are relatively lower than those of hard sealing.

3. Manufacturing Process:

Due to the complex working environments in many chemical and mechanical industries, many applications involve high temperature and high pressure, high friction resistance of the medium, and strong corrosiveness. With technological advancements, the use of various materials has improved, and processing capabilities have kept pace, leading to the widespread adoption of hard-seated ball valves. In fact, the principle of hard-seated ball valves is the same as that of soft-seated valves, but because it is a metal-to-metal seal, the hardness relationship between the metals, the working conditions, and the type of medium must be considered. Hardening treatment is usually required, and the ball and valve seat must be continuously ground to achieve a seal. Hard-seated ball valves have a long production cycle and are more complex to manufacture; making a good hard-seated ball valve is not easy. 

4. Regarding Usage Conditions

Soft seals generally achieve very high sealing performance, while hard seals can be designed for varying levels of performance depending on requirements. Soft seals require fire protection because the sealing material can leak at high temperatures, a problem that hard seals do not have. Hard seals can generally handle very high pressures, while soft seals cannot. Due to the nature of the fluid being handled, soft seals are unsuitable in some applications (such as with corrosive media). Finally, hard-sealed valves are generally more expensive than soft-sealed ones. In terms of manufacturing, there is little difference between the two, mainly in the valve seat material: soft seals use non-metallic materials, while hard seals use metallic materials.

5. Regarding Equipment Selection

The selection of soft-sealed and hard-sealed ball valves mainly depends on the process medium, temperature, and pressure. Generally, if the medium contains solid particles, is abrasive, or has a temperature above 200 degrees Celsius, a hard-sealed valve should be used. For valves with a diameter greater than 50 and a large pressure difference, the opening torque should also be considered. If the torque is large, a fixed hard-sealed ball valve should be selected. Both soft and hard seals can achieve a sealing class of 6.

If you would like to find out more about valves or purchase other products, please contact us at fluid@weitengroup.com, wwww.weitengroup.com.