The valve seat of the butterfly valve is a key sealing component inside the butterfly valve. Its main function is to contact the butterfly plate (valve disc) and form a sealing surface when the valve is closed to prevent medium leakage. Specifically, the butterfly valve seat can be installed on the inner wall of the valve body or designed to be integrated with the butterfly plate, relying on its material and structure to achieve a good sealing effect.
1. Introduction of Butterfly valve Seat Classification
1. 1 Classification by material
A. Elastic soft valve seat
Usually refers to materials such as rubber, silicone, polytetrafluoroethylene (PTFE).
Advantages: good sealing performance, fast response, suitable for low temperature, low pressure and low corrosive media (except PTFE).
Disadvantages: poor wear resistance, service life is limited by material aging.
B. Metal valve seat
Made of stainless steel, carbon steel or other metal materials.
Advantages: high temperature resistance, high pressure resistance, strong wear resistance, suitable for harsh working conditions.
Disadvantages: high requirements for metal-to-metal sealing, strict processing accuracy and installation requirements.
C. Composite valve seat
Combines the advantages of metal and soft materials, usually covering the metal structure with elastic materials such as graphite.
It can not only ensure good sealing performance, but also improve wear resistance and service life.
1.2. Classification by structural form
A. Hard back seat
The valve seat and the back are integrally formed, with a simple structure, and the sealing surface fits tightly with the valve body.
The disadvantage of this hard back valve seat is that once the valve seat is worn or aged, the entire butterfly valve needs to be disassembled for replacement.
B. Removable soft seat
The soft valve seat adopts a dovetail design and can be disassembled and replaced separately.
The advantage is that it is easy to maintain and prolong the service life of the butterfly valve as a whole.
1.3. According to special design
A. Double eccentric butterfly valve
The butterfly plate moves along two eccentric axes when closed to reduce contact friction with the valve seat.
The advantages are reduced wear, extended valve seat life, and improved sealing performance.
B. Triple eccentric butterfly valve
Further design based on double eccentricity enables the butterfly plate and metal valve seat to achieve metal-to-metal precision contact.
It can achieve true zero leakage effect and is suitable for high-demand working conditions (such as high temperature and high-pressure media).
Different types of valve seat materials have different physical and chemical properties and are suitable for various working conditions. In this article, we mainly study and compare the main types, performance and applications of elastic valve seats.
Commonly used elastic valve seats on the market are NBR, EPDM, VITON (FKM), natural rubber (NR), silicone (Silicone Rubber), polyurethane (PU), hydrogenated nitrile rubber (HNBR), HYPALON (CSM), PTFE:
2. Comparison of Valve Seat Material Properties
| Material | NBR (Nitrile Rubber) | EPDM (Ethylene Propylene Diene Monomer Rubber) | VITON (FKM/Fluorocarbon Rubber) | NR (Natural Rubber) | Silicone Rubber | PU (Polyurethane) | HNBR (Hydrogenated Nitrile Rubber) | HYPALON (CSM/Chlorosulfonated Polyethylene Rubber) | PTFE (Polytetrafluoroethylene, Teflon) |
|---|---|---|---|---|---|---|---|---|---|
| Oil Resistance | Excellent | Poor | Outstanding (resists fuels and chemicals) | Poor | Poor | Moderate | Excellent (resists oil, fuel, and lubricants) | Moderate | Excellent (best chemical resistance) |
| Chemical Resistance | Moderate, resists mild acids and bases | Excellent (resists acids, bases, and oxidizers) | Excellent (resists acids, bases, organic solvents) | Moderate | Excellent (resists oxidizers, non-toxic) | Moderate | Good (resists mild acids and bases) | Excellent (resists acids, bases, and oxidizers) | Excellent (resists all chemicals) |
| Temperature Range (°C) | -30 ~ 100 | -40 ~ 120 (briefly up to 150) | -20 ~ 200 | -50 ~ 70 | -60 ~ 230 | -30 ~ 80 | -40 ~ 150 | -40 ~ 130 | -200 ~ 260 |
| Wear Resistance | Good | Moderate | Good | Excellent (superior wear resistance) | Moderate | Excellent (best wear resistance) | Excellent | Good | Poor (easily wears down) |
| Water Resistance | Moderate | Excellent (suitable for hot water and steam) | Moderate | Good | Excellent (food-grade) | Moderate | Good | Excellent | Excellent (waterproof) |
| Weather Resistance (UV/Ozone) | Poor (ages easily) | Excellent (high weather resistance) | Good | Moderate | Excellent (extreme weather resistance) | Moderate | Excellent (high weather resistance) | Outstanding (superior weather resistance) | Excellent (UV and aging resistance) |
| Flexibility | Good | Excellent | Moderate | Excellent | Excellent | Good | Excellent | Good | Hard (low friction) |
| Main Applications | Fuel, lubricating oil, hydraulic oil systems, industrial seals | Water supply and drainage systems, chemical pipelines, steam systems, outdoor equipment | High-temperature chemical applications, fuel systems, aerospace, petrochemicals | Mining, wear-resistant equipment, mechanical linings | Food, pharmaceuticals, electronics sealing, high and low-temperature applications | Mechanical sealing, wear-resistant equipment, mining, hydraulic systems | Petrochemicals, automotive industry, high-temperature oil seals | Chemical industry, corrosive environments, outdoor equipment, ozone-resistant sealing | Strong corrosive chemicals, pharmaceuticals, food-grade sealing, high-temperature sealing |
3. Suitable Working Conditions for Valve Seat Materials
| Material | Fuel/Oil Resistance | Acid/Base Resistance | High-Temperature Resistance | Low-Temperature Resistance | Water Resistance | Wear Resistance | Weather Resistance (Outdoor, Ozone) | Food-Grade |
|---|---|---|---|---|---|---|---|---|
| NBR | ✔ | ❌ | ❌ | ❌ | ❌ | ✔ | ❌ | ❌ |
| EPDM | ❌ | ✔ | ✔ | ✔ | ✔ | ❌ | ✔ | ✔ |
| VITON | ✔ | ✔ | ✔ | ❌ | ❌ | ✔ | ✔ | ❌ |
| NR | ❌ | ❌ | ❌ | ✔ | ✔ | ✔ | ❌ | ❌ |
| Silicone | ❌ | ✔ | ✔ | ✔ | ✔ | ❌ | ✔ | ✔ |
| PU | ❌ | ❌ | ❌ | ❌ | ❌ | ✔ | ❌ | ❌ |
| HNBR | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ❌ |
| HYPALON | ❌ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ❌ |
| PTFE | ✔ | ✔ | ✔ | ✔ | ✔ | ❌ | ✔ | ✔ |
4. Material Selection Recommendations
· For fuel, oil, or hydraulic oil applications→ NBR, HNBR, VITON
· For acid/base and chemical resistance→ EPDM, HYPALON, VITON, PTFE
· For high-temperature resistance (>150°C)→ VITON, Silicone, HYPALON, PTFE
· For low-temperature applications (<-40°C)→ NR, Silicone, PTFE
· For high wear and abrasion resistance (mining, machinery)→ NR, PU, HNBR
· For drinking water and food-grade applications→ EPDM, Silicone, PTFE
· For outdoor and ozone resistance→ EPDM, HYPALON, Silicone, PTFE
5. Conclusion
· NBR (Nitrile Rubber): Best for oil-based applications such as fuel, hydraulic oil, but unsuitable for high temperatures and acids/bases.
· EPDM (Ethylene Propylene Rubber): Ideal for water treatment, chemical, and steam systems; highly weather-resistant but not oil-resistant.
· VITON (Fluorocarbon Rubber): Excellent for high temperatures, strong acids/bases, and fuel applications.
· NR (Natural Rubber): Superior abrasion resistance, used in mining and machinery but not resistant to chemicals.
· Silicone Rubber: Excellent for high/low temperatures, food-safe applications, but lacks wear resistance.
· PU (Polyurethane): Best for extreme wear resistance, used in hydraulic seals and mining applications.
· HNBR (Hydrogenated Nitrile Rubber): Better than NBR in high-temperature and wear applications, used in petrochemical industries.
· HYPALON (CSM/Chlorosulfonated Polyethylene Rubber): Best for acid/base resistance and weather exposure, ideal for chemical and ozone-resistant sealing.
· PTFE (Polytetrafluoroethylene): The most chemically resistant, ideal for high temperatures, corrosive environments, and food processing.