Seal Materials Explained

Importance of Seal Materials in Solenoid Valves

Solenoid valves are available in a wide range of materials, but one of the most critical components to evaluate is the seal material. The seal must be compatible with the intended media and application conditions—resisting chemicals, temperature, and pressure—while maintaining reliable sealing performance.

General Recommendations

Standard brass solenoid valves typically come with NBR (Nitrile) seals, which are ideal for most water and air applications. For more demanding conditions involving aggressive chemicals, higher temperatures, or pressures, alternative seal materials are available and recommended.

Helpful Hint: Do not guess. Always confirm compatibility with your chemical supplier or consult a technical support team. Refer to the chemical compatibility guide for reference.

Elastomer Seal Materials

Aflas® (TFE/P)

Temperature Range: -5°C to +204°C

Key Properties: A Fluoro elastomer offering excellent resistance to steam, petroleum oils, and H₂S.

Ideal for applications involving amine corrosion inhibitors and hydrogen sulphide.

Butyl Rubber (IIR)

Temperature Range: -50°C to +100°C

Key Properties: Very low gas permeability and excellent shock/vibration damping.

Not suitable for mineral or petroleum-based fluids.

Used in diaphragms, gaskets, O-rings, and high-pressure sealing.

Carboxylated Nitrile (XNBR)

Temperature Range: -55°C to +135°C

Key Properties: Excellent abrasion resistance and good compatibility with water and petroleum oils.

Epichlorohydrin Rubber (ECO)

Temperature Range: -35°C to +125°C

Key Properties: Similar to NBR but with improved heat, petrol, and chemical resistance.

Limited sealing use due to poor compression set and potential metal corrosion.

EPDM (Ethylene Propylene Diene Monomer)

Temperature Range: -40°C to +120°C (up to 150°C with steam)

Excellent Resistance To: Hot water, steam, oxidising chemicals, and UV.

Poor Resistance To: Oils, fuels, hydrocarbons, and gamma radiation.

FKM (Fluoroelastomer, Viton®)

Temperature Range: -26°C to +205°C

Excellent Resistance To: Heat, acids, oils, salt solutions, and hydrocarbons.

Poor Resistance To: Ketones and acetone.

FF-KM (Perfluoroelastomer)

Temperature Range: -40°C to +250°C

Outstanding Resistance: To nearly all solvents and chemicals.

Disadvantages: Very high cost and difficult to mold.

Fluorinated Ethylene Propylene (FEP)

Temperature Range: -73°C to +200°C

Properties: Chemically inert and very tough, with excellent chemical resistance.

Poor memory at low temperatures.

Fluorosilicone (FVMQ)

Temperature Range: -5°C to +177°C

Combines the temperature stability of silicone with fuel and solvent resistance.

Ideal for use with petroleum oils and fuels.

HNBR (Hydrogenated Nitrile)

Temperature Range: -40°C to +150°C

Good Resistance To: Oils, amine mixtures, oxidised fuels, ozone, and new bio-oils.

Poor Resistance To: Esters, ethers, halogenated solvents, and flames.

Hypalon (CSM)

Temperature Range: -35°C to +125°C

Excellent Resistance To: UV, ozone, oxidising chemicals, and hot water.

Not Ideal For: Low temperatures and fuel resistance.

NBR (Nitrile, Buna-N)

Temperature Range: -35°C to +100°C

Most Common Seal Material for air, water, fuel, and oils.

Poor Resistance To: Ozone, acetone, and chlorinated solvents.

Neoprene (CR)

Temperature Range: -20°C to +110°C

Known for its resistance to weather, ozone, and abrasion.

Common in O-rings, seals, wetsuits, and insulation.

Polyacrylate (ACM)

Temperature Range: -20°C to +150°C

Used For: High-speed oil applications.

Resistant To: Petroleum oils and Freon refrigerants.

Polyurethane (AU)

Temperature Range: -15°C to +85°C

Properties: High abrasion resistance and tensile strength.

Good for hydraulic and petroleum oil systems.

PTFE (Teflon®)

Temperature Range: -200°C to +230°C

Exceptional Resistance: To almost every chemical and extreme temperatures.

Limitation: Not elastic; limited sealing performance.

Silicone (VMQ)

Temperature Range: -60°C to +230°C

Good Resistance To: Oil (not diesel), UV, and low temperatures.

Poor Resistance To: Steam over 150°C, strong acids/bases, and hot air.

Thermoplastics and Other Materials

ABS (Acrylonitrile Butadiene Styrene)

Temperature Range: -40°F to +180°F

Applications: Drain, waste, and vent systems.

Resistant to sewage, hot water, and household chemicals.

CPVC (Chlorinated PVC)

Temperature Range: Up to 210°F

Applications: Hot corrosive liquids, hot and cold water systems.

Better chemical resistance than standard PVC.

Polypropylene (PP)

Temperature Range: Up to 180°F

Chemical Resistance: Excellent against acids, alkalis, and organic solvents.

Not suited for oxidizing acids and aromatics.

PVC (Polyvinyl Chloride)

Temperature Range: Up to 140°F

Applications: Widely used in chemical processing and water systems.

Avoid with ketones and chlorinated hydrocarbons.

PVDF (Polyvinylidene Fluoride)

Temperature Range: Up to 280°F

Extremely Resistant: To chlorine, bromine, and many solvents.

Excellent for high-temperature chemical applications.

Polychloroprene (CR)

Temperature Range: -20°F to 160°F

Recommended For: Food and beverage, with moderate chemical resistance.

Poor Resistance To: Strong oxidizers and aromatic hydrocarbons.

Graphite

Temperature Range: Up to 2000°F

Outstanding Performance: In fire-rated sealing applications.

Not recommended in oxidising environments.

Metals Used in Valves & Fittings

Copper

Excellent thermal and electrical conductivity, corrosion resistance, and ductility. Common in soldered or brazed connections.

Bronze

A high-strength copper alloy with good corrosion resistance. Standard for pressure-rated valve fittings.

Silicon Bronze

Stronger than copper, with excellent stress corrosion cracking resistance. Used in valve stems.

Aluminium Bronze

As strong as steel, with an aluminium oxide layer for corrosion resistance.
Not suitable for high-pH systems.

Brass

Good general corrosion resistance.
Susceptible to de-zincification in specific environments.

Gray Iron

Good cast ability, machine ability, and dampening properties. Standard for valve bodies and bonnets.

Ductile Iron

Stronger than Gray iron, with higher mechanical properties due to special treatments.

Carbon Steel

Excellent mechanical properties, fatigue resistance, and temperature tolerance. Common in gate, globe, and ball valves.

3% Nickel Iron

Better corrosion resistance than ductile/Gray iron. Ideal in oxidising atmospheres.

Nickel-Plated Ductile Iron

Used in chemical processing due to high tensile strength and abrasion resistance.

400 Series Stainless Steel

Magnetic, heat-treatable stainless steel. Common in stem and back-seat applications.

316 Stainless Steel

Non-magnetic, austenitic stainless steel with excellent corrosion resistance. Used in valve bodies, stems, and balls.

630 Stainless Steel

Martensitic, precipitation-hardened stainless steel with superior strength and corrosion resistance. Used in ball and butterfly valve stems.

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