The difference between the use of soft and hard seals of ball valves

The use of soft and hard seals for ball valves is different, mainly in terms of construction, and the manufacturing standards of valves are not the same.
Structural mechanism
The hard seal of a ball valve is a seal between metal and metal, and the sealing ball and seat are all metal. Processing accuracy and process are difficult, generally used in high pressure, usually more than 35MPa. A soft seal is a seal between metal and non-metal, such as nylon\tetrafluoroethylene, which is manufactured to the same standard.
Sealing material
The soft and hard seal is for the sealing material of the valve seat. The hard seal is precision machined with the seat material to ensure the precision with the valve core (sphere), generally stainless steel and copper. The soft seal means that the sealing material embedded on the valve seat is a non-metallic material. Because the soft sealing material has a certain elasticity, the processing precision requires a relatively hard seal to be low.
Manufacturing process
Due to a lot of chemical industry, the working environment of the machinery industry is more complicated. Many of them are high temperature and high pressure. The frictional resistance of the medium is large and the corrosion is strong. Now the technology has improved, the use of various materials is better, and the processing can be followed. Up, the hard-sealed ball valve has been widely promoted.
In fact, the principle of the hard-sealed ball valve is the same as that of the soft seal. It is only because of the seal between the metals, taking into account the hardness relationship between the metals, as well as the working conditions and what medium to go. Hardening is generally required, and the ball and the seat are continuously ground to make it seal. Hard seal ball valves have a long production cycle and are complicated to process. Hard seal ball valves are not easy to do.
Condition of use
Soft seals can generally achieve high seals, while hard seals can be high or low according to requirements; soft seals require fire protection, because at high temperatures, soft seal materials can leak, while hard seals do not have this problem; hard seals Generally, high pressure can be done, soft seals can't; soft seals can't be used in some cases due to the problem of the medium being flowed (such as some corrosive media); finally, hard-sealed valves are generally more expensive than soft seals. As far as manufacturing is concerned, the difference between the two is small, mainly due to the difference of the valve seat, the soft seal is non-metal, and the hard seal is metal.
On the device selection
Soft and hard sealing ball valve is mainly based on process medium, temperature and pressure. Generally, the medium contains solid particles or has wear or temperature is higher than 200 degrees. It is best to use hard seal. The diameter is larger than 50. The valve pressure difference is larger. When the torque is large, a fixed hard-sealed ball valve should be used, and the sealing level of the soft and hard seal can reach 6 levels.