Let's talk about some obvious features of hard-sealed cast steel gate valve and several obvious differences with elastic soft-sealed gate valve:
The first point is from the sealing materials of the two valves:

The elastic soft sealing gate valve and the hard sealing gate valve are for the sealing material of the valve seat. The hard sealing is precision machined with the valve seat material to ensure the matching accuracy with the valve core (ball), generally stainless steel and copper. 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 accuracy requirements are lower than that of the hard seal;

The second aspect differs from the structural mechanism of the two:

The hard seal is the seal between metal and metal, and the sealing ball and valve seat are all metal. The machining accuracy and process are more difficult, and it is generally used in 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;
The third depends on the manufacturing process of both of them:
Due to the complex working environment of many chemical and mechanical industries, many of which are high temperature and high pressure, the friction resistance of the medium is large, and the corrosiveness is strong. On, the hard-sealed ball valve has been widely promoted;
In fact, the principle of the hard-sealed gate valve is the same as that of the soft-sealed gate valve, but because it is a seal between metals, the hardness relationship between the metals, as well as the working conditions and the medium used, must be considered. Hardening treatment is generally required, and continuous grinding between the ball and the valve seat is required to achieve sealing. Hard-sealed gate valves have a long production cycle and complex processing, and hard-sealed ball valves are not easy to do well;
Article 4 There are also many differences in the equipment selection of these two valves:

The selection of soft and hard sealing 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 use hard sealing. , When the torque is large, a fixed hard-sealed gate valve should be selected, and its sealing level can reach six levels regardless of the soft and hard seal;

The last aspect is the conditional difference for field 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, but hard seals do not have this problem; hard seals Generally, very high pressures can be used, 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);
In fact, the most easily overlooked point is that the hard seal valve is generally more expensive than the soft seal. Although there is little difference between the two in terms of processing and manufacturing, the most important thing is the difference between the valve seats, because the soft seal is non-metallic, while the hard seal It is made of metal, and the cost of raw materials is much higher, so these are also several decisive factors that affect the price and use when purchasing. I warmly remind all purchasers to pay attention to these details.