Seal / Diaphragm Material Selection
Selecting the correct sealing material for your solenoid valve requires an understanding of available sealing materials. Seals are usually the most limiting factor of a solenoid valve. The seal selection should take the following items into consideration:
- Chemical properties of the media
- Temperature of the media
- Pressure to be used
Nitrile Rubber (NBR / Buna-N)
The chemical name for Nitrile rubber is Butadiene Acrylonitrile. However, most commonly it is referred to as NBR or Buna-N. NBR is probably the most common solenoid valve seal material and it is considered the standard material for neutral fluids by many. NBR is also the standard material for O-rings.
NBR can stand media temperatures to approximately 190 degrees Fahrenheit (90 degrees Celsius) on continuous basis, and higher temperatures intermittently. NBR resists aging caused by heat very well. However, NBR's resistance to sunlight is very poor. Abrasion and tear resistance of NBR is very good.
NBR seals are most commonly used with the following media:
- Different Fuels, Oils, and Gases
NBR has a good resistance to:
- Aliphatic hydrocarbons
- Mineral Oil
- Vegetable Oil
- Hydraulic fluids
- Many Acids
NBR has a poor resistance to:
- Methyl Ethyl Ketone
- Chlorinated Hydrocarbons
- Ethers and Esters
In addition to solenoid valve seals, NBR rubber is often used for water pump, carburetor, transmission, hydraulic pump, and hydraulic actuator seals.
EPDM stands for Ethylene Propylene Diene Monomer rubber. EPDM solenoid valve seals are well suited for use with hot water due to EPDM's excellent resistance to heat. The maximum service temperature of EPDM is approximately 250 degrees Fahrenheit (120 degrees Celsius). EPDM is unsuitable for use with most oils and fuels.
EPDM seals are most commonly used with the following media:
- Hot /Cold Water, Steam
EPDM has a good resistance to:
- Oxidizing Chemicals
- Up to Medium Concentration Acids
- Fireproof hydraulic fluids
- Many Ketones and Alcohols
- Abrasion and Tearing
EPDM has a poor resistance to:
- Most Oils and Fuels
- Aromatic and Aliphatic Hydrocarbons
- Halogenated Solvents
- Concentrated Acids
Viton® is a brand name for the fluoroelastomer manufactured by DuPont. It is well know for its excellent heat resistance, making service temperatures nearing 300 degrees Fahrenheit (150 degrees Celsius) possible.
Viton® seals are most commonly used with the following media:
- Hot Water
- Salts Solutions
Viton® has a good resistance to:
- Many Aggressive Chemicals
- Diluted Acids
- Weak Alkalis
- Mineral Oils
- Aliphatic and Aromatic Hydrocarbons
- Chlorinated Hydrocarbons
Viton® has a poor resistance to:
PTFE - Polytetrafluoroethylene
PTFE is a polytetrafluoroethylene. The most well know trademark of PTFE is DuPont's Teflon. PTFE is practically resistant to all fluids. PTFE is non-elastic, limiting its use in certain applications. PTFE can be used with media reaching very high temperatures (up to 450 degrees Fahrenheit / 230 degrees Celsius). PTFE is well suited for ball valve applications.