Hard sealing valve seat

The function of hard sealing valve seat

1. Seal medium to prevent leakage.
   • The hard sealing valve seat is closely attached to the valve core (such as ball, butterfly plate, gate, etc.) to form a sealing surface to prevent the medium (liquid, gas, powder, etc.) in the pipeline from leaking when the valve is closed.
   • Its sealing performance depends on the hardness and machining accuracy of the material, and it can maintain a stable seal in high pressure, high temperature or corrosive media. For example, metal valve seats (such as stainless steel and alloy) can withstand strong medium erosion and pressure impact.
2. Bear the impact of medium pressure and temperature
   • Under high pressure conditions (such as oil pipeline and natural gas transportation), the hard sealing valve seat should resist the static pressure and dynamic pressure brought by the medium to avoid sealing failure caused by pressure deformation.
   • In high temperature environment (such as thermal system and chemical reaction device), the high temperature resistance of hard sealing materials (such as cemented carbide and ceramics) can prevent the valve seat from softening and wearing due to temperature rise, and maintain the stability of sealing structure.
3. Ensure the switching function and service life of the valve.
   • The matching accuracy of valve seat and valve core directly affects the smoothness of valve opening and closing. Wear-resistant materials of hard sealing seat (such as tungsten carbide and surfacing cobalt-based alloy) can reduce the friction loss during switching and prolong the service life of the valve.
   • For valves that frequently open and close (such as control valves in industrial pipelines), hard sealing structure can reduce the wear speed of sealing surface and maintain long-term reliable sealing performance.
4. Adapt to corrosion and wear of special media.
   • For highly corrosive media (such as acid, alkali and salt solution), corrosion-resistant materials (such as Hastelloy and titanium alloy) can be selected for hard sealing valve seat to prevent chemical corrosion of the valve seat by media.
   • When conveying media (such as pulp and sewage) containing solid particles and sediment, the high hardness materials (such as ceramics and wear-resistant cast iron) of hard sealing valve seat can resist particle erosion and avoid rapid damage of sealing surface.

Application environment of hard sealing valve seat

1. Industrial piping system

• Oil and gas industry
  • Application scenarios: oil pipelines, long-distance natural gas pipelines, wellhead devices, etc.
  • Working conditions: high pressure (up to more than 10MPa), medium containing sulfur (hydrogen sulfide corrosion resistance) and wide temperature range (-40℃~120℃).
  • Hard sealing seat material: Inconel alloy and cobalt-based alloy are commonly used to ensure sulfur corrosion resistance and high pressure sealing.
• chemical lines
  • Application scenario: inlet and outlet of reaction kettle, corrosive medium conveying pipeline (such as sulfuric acid and caustic soda).
  • Working conditions: the medium is corrosive, the temperature is high (up to 300℃ or above), and it may be accompanied by crystallization or particles.
  • Hard sealing seat material: Hastelloy (such as C-276), titanium alloy or ceramics are selected to resist corrosion by strong acid and alkali and crystal wear.

2. Energy and thermal system

• thermal power generation
  • Application scenario: main steam pipeline, high temperature and high pressure water supply system (temperature over 500℃, pressure over 15MPa).
  • Hard sealing seat material: Martensite stainless steel (such as 1Cr13) is used for surfacing hard alloy, or nickel-based alloy is used to meet the sealing and strength requirements under high temperature and high pressure.
• central heating
  • Application scenario: steam pipe network and high-temperature hot water pipeline (temperature 150℃~250℃).
  • Hard sealing seat material: nodular cast iron surfacing stainless steel or copper alloy, giving consideration to wear resistance and high temperature oxidation resistance.

3. Mining and Metallurgical Industry

• Mining and pulp transportation
  • Application scenario: the inlet and outlet of tailings pipeline and pulp pump (the medium contains sediment and ore particles, which is seriously worn).
  • Hard sealing valve seat material: Wear-resistant cast iron, ceramics or tungsten carbide are used to resist particle erosion. For example, ceramic valve seat can significantly prolong the service life in pulp valve.
• Metallurgical steelmaking
  • Application scenario: blast furnace gas pipeline and slag treatment system (medium contains dust and high-temperature flue gas at 200℃~400℃).
  • Hard sealing seat material: wear-resistant stainless steel (such as 316L) or hardfacing alloy shall be selected to prevent dust abrasion and high temperature oxidation.

4. Special working conditions and harsh environment

• cryogenic engineering

  • Application scenarios: liquefied natural gas (LNG) pipeline (temperature-162℃), liquid nitrogen storage tank valve.

  • Hard sealing seat material: adopt low-temperature resistant stainless steel (such as 304L and 316L) to ensure that the material is not brittle at low temperature and the sealing surface is closely attached.

• nuclear industry

  • Application scenario: nuclear power plant main loop, radioactive medium pipeline (high safety and radiation resistance).

  • Hard sealing seat material: high-purity stainless steel or nickel-based alloy is used, and cobalt-based alloy is surfacing on the surface to meet the nuclear sealing requirements and radiation resistance.

Comparison between hard sealing seat and soft sealing seat (to help understand the application scenario)