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 Technical    Seal Material Explained 

Connexion Solenoid Valve Seal Basic Guide

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

The next sections describe the most common seal materials available for solenoid valves. Usually more than one seal material is available for each valve type.

Connexion Developments Ltd cannot be held responsible for any information provided below. If you need more detailed information on chemical compatibility please contact us or your chemical supplier directly.  Click Here for Connexion chemical resistance chart.

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 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:

  • Water
  • Air
  • Different Fuels, Oils, and Gases

NBR has a good resistance to:

  • Aliphatic hydrocarbons
  • Petroleum
  • Fuels
  • Mineral Oil
  • Vegetable Oil
  • Hydraulic fluids
  • Alcohol
  • Many Acids
  • Abrasion

NBR has a poor resistance to:

  • Ozone
  • Acetone
  • 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 Rubber
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 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
  • Freon
  • Air

EPDM has a good resistance to:

  • Heat
  • Ozone
  • Oxidizing Chemicals
  • Up to Medium Concentration Acids
  • Alkalis
  • Fireproof hydraulic fluids
  • Many Ketones and Alcohols
  • Sunlight
  • Abrasion and Tearing

EPDM has a poor resistance to:

  • Most Oils and Fuels
  • Hydrocarbons
  • Aromatic and Aliphatic Hydrocarbons
  • Halogenated Solvents
  • Concentrated Acids

Viton® (FKM)
Viton® (FKM) is a brand name for the Fluoroelastomer manufactured by DuPont. It is well know for its excellent heat resistance, making service temperatures nearing 150 degrees Celsius possible.

FKM seals are most commonly used with the following media:

  • Hot Water
  • Acid
  • Alkali
  • Oils
  • Hydrocarbon
  • Salts Solutions

Viton® (FKM) has a good resistance to:

  • Hydrocarbons
  • Many Aggressive Chemicals
  • Diluted Acids
  • Weak Alkalis
  • Mineral Oils
  • Aliphatic and Aromatic Hydrocarbons
  • Chlorinated Hydrocarbons
  • Sunlight
  • Ozone

Viton® (FKM) has a poor resistance to:

  • Ketones
  • Acetone

PTFE - Polytetrafluoroethylene
PTFE is a Polytetrafluoroethylene. The most well known 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 230 degrees Celsius. 
 
Connexion Developments Ltd have access to many other types of seal material including metal/metal and metal/Resin and FFKM amongst others for more aggressive and demanding applications. 
 
Please also keep in mind that apart from the dry armature valves in the Connexion Range most valves will have varying grades of stainless steel in contact with the media. i.e. 303 or 302 stainless steel springs, 304 stainless core tube and stainless steel 430F Armature. Please consult us its a free service we provide to help.
 
Elastomer
Temperature range F.
Temperature range C.
Flurocarbon (Viton ®)
-15 to 400
-25 to 205
Ethyle propylene
-70 to 300
-55 to 150
Chemraz
-20 to 450
-30 to 230
Kalrez ®
0 to 500
-20 to 260
Neoprene
-45 to 300
-45 to 150
Buna N
-65 to 225
-55 to 105
Buna S
-75 to 250
-60 to 120
 
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