Soft seal gate valves and
hard seal gate valves are two major categories in the
gate valve series. With the continuous development of China's industrial market, it is necessary to understand the difference between those two categories. Use one of the two valves at will may not only affect production efficiency, but also have great impact on economic benefits. The following will describe the
difference between soft seal and hard seal gate valves.
1. Sealing Materials
Soft seal gate valve: the sealing pair has metal material on one side and elastic nonmetal material on the other side, which provides good sealing performance but is not resistant to high temperature, easy to wear, poor in mechanical properties, etc.
Hard seal gate valve: it is called "hard seal" when both sides of the seal pair are made of metal or other hard materials, which has poor sealing performance, but high temperature resistance, antifraying and good mechanical properties.
2. Structure Mechanism
Hard seal gate valve: the seal is produced by metal-to-metal contact between the sealing face. The sealing ball and valve seat are all metal. Machining accuracy and process are relatively difficult and the valve is generally used for high pressure (usually above 35MPa).
Soft seal gate valve: the seal is produced by metal and nonmetal contact (e.g. nylon and Teflon) between the sealing face. And the manufacturing standard is the same.
3. Equipment Selection
The selection of soft and
hard seal gate valves is mainly based on the process medium, temperature and pressure. Generally, it is better to choose hard seal valves if the medium contains solid particles, or causes wear to the pipeline, or its temperature is higher than 200 degrees. The torque of the valve should also be considered when the differential pressure is large. When the torque is large, a hard seal trunnion ball valve should be selected. The sealing grade can reach Grade 6 regardless of the hard seal or soft seal.
4. Conditions of Use
The sealing performance of
soft seal gate valves generally can reach a high level, while the sealing performance of
hard seal gate valves can either be high level or low level according to requirements; the soft seal gate valve needs fire prevention, because under high temperature, the material of the soft seal will leak, while the hard seal one does not have this problem; hard seal can be used under high pressure, but soft seal cannot be used; soft seal is not applicable in some occasions because the flowing medium may cause some problems (e.g. pipe wearing). Finally, hard seal valves are usually more expensive than soft seal ones. As for manufacturing, there is little difference between the two and the main difference is the valve seat. The seat of the soft seal valve is non-metal while the seat of the hard seal one is metal.
Through the above introduction, you'll gain a better understanding about the main
difference between soft seal and hard seal gate valves. If you want to know more details, please contact us in time.
