1. Sealing material and structure
Hard seat valve: uses metal sealing surface (such as stainless steel, carbide), and achieves rigid contact sealing through high-precision grinding. It is commonly used in high-temperature and high-pressure scenarios such as boiler main steam pipelines. Its sealing surface hardness can reach HRC50 or above, and it has strong wear resistance but requires a large clamping force to ensure the sealing effect.
Soft seat valve: uses non-metallic elastic materials (such as PTFE, fluororubber or nylon), relying on the flexible deformation of the material to fill the microscopic gap, suitable for clean media with strict sealing requirements such as liquefied gas and clean water. The friction coefficient of soft sealing materials is low (about 0.1), and only a small operating force is required to achieve zero leakage.
2. Working condition adaptability
Hard seat valve: It has a wide temperature tolerance range (-29°C to 550°C), strong anti-scouring ability, and is suitable for media containing particles or high viscosity (such as boiler feed water, high-temperature steam). However, it is easy to leak due to microscopic unevenness of the sealing surface under low-pressure conditions.
Soft seat valve: limited temperature resistance (PTFE temperature resistance ≤ 150°C, fluororubber ≤ 200°C), and easily scratched by particles, only recommended for clean fluids without solid impurities (such as gas, pure water). The advantage is that the low-pressure sealing performance far exceeds the hard seal, and the leakage rate can be reduced by more than 90%.
3. Maintenance and life
Hard seat valve: The metal sealing surface is wear-resistant and the life can reach more than 100,000 opening and closing cycles, but the valve seat needs to be replaced or ground after the sealing surface is damaged, and the maintenance cost is high.
Soft seat valve: Non-metallic seals are prone to aging (cycle is about 3-5 years), and the valve seat or sealing ring needs to be replaced regularly, but the replacement operation is simple and the cost is low.
4. Typical application scenarios
Hard seat valve: high-temperature steam pipelines in thermal power plants, high-pressure sulfur-containing medium control in petroleum refining;
Soft seat valve: liquefied petroleum gas storage and transportation system, purified water pipelines in the pharmaceutical industry, and sanitary fluid control in food processing.
