What seal material for power steering fluid?

Choosing the appropriate seal material for power steering fluid is crucial to ensure the longevity and proper functioning of the system. According to various sources, the most commonly used seal materials for power steering fluids include Nitrile (Buna-N), Polyacrylate (ACM), and Fluorocarbon (FKM).

Your Guide to O-Ring Materials

As we've discussed in past entries on this blog, O-Rings can come in numerous sizes and have a wide range of uses. More information can be found on our web, so please take a look.

They can also be made from different substances. Here’s a guide to the kinds of O-Ring materials we use, how they are used, and when to avoid using them.

Nitrile (Buna, NBR)

• Temperature: -55 to 250 degrees Fahrenheit
• Applications: Petroleum-based oils and fuels, dynamic applications
• Avoid: Brake fluids and ozone

Hydrogenated Nitrile (HNBR)

• Temperature: -50 to 300 degrees Fahrenheit
• Applications: Water and steam up to 300 degrees Fahrenheit, fuel systems, oil resistant and high abrasion applications
• Avoid: Strong acids and polar solvents such as ethers and ketones

Polyacrylate (ACM)

• Temperature: -15 to 350 degrees Fahrenheit
• Applications: Mineral oil, engines, gear boxes, power steering, transmissions
• Avoid: Cold temperatures, hot water, steam

Ethylene-Propylene (EPDM)

• Temperature: -55 to 275 degrees Fahrenheit, 300 degrees Fahrenheit when used with peroxide curing agents
• Applications: Brake systems, glycol-based fluids, H20 steam
• Avoid: Mineral oil products and hydrocarbon fluids

Chloroprene (Neoprene, CR)

• Temperature: -40 to 250 degrees Fahrenheit
• Applications: Refrigeration, due to its excellent ozone resistance, low-temp H20
• Avoid: Esters, ketones and aromatic and chlorinated hydrocarbons.

Butyl

• Temperature: -70 to 400 degrees Fahrenheit
• Applications: Life science and medical devices, FDA applications, numerous specialized compounds for specific material certifications
• Avoid: Highly abrasive applications and water and steam over 250 degrees Fahrenheit

Fluorosilicone (FVMQ)

• Temperature: -75 to 400 degrees Fahrenheit
• Applications: Aerospace, fuel and mineral oil
• Avoid: High temperature air, dynamic applications

Fluorocarbon (Viton, FKM)

• Temperature: -15 to 400 degrees Fahrenheit
• Applications: Broad chemical resistance, transmission and blended gasoline
• Avoid: Low temperatures, ketones and amines

Tetrafluoroethylene-Propylene (AFLAS)

• Temperature: 15 to 450 degrees Fahrenheit
• Applications: Aerospace, steam, hot water, oil fields
• Avoid: Chlorinated hydrocarbons, ketones, acetic acid

Perfluoelastomer (FFKM)

• Temperature: -15 to 600 degrees Fahrenheit
• Applications: Semiconductors, chemical processing, vacuum applications
• Avoid: Fluorinated solvents and perfluorinated lubricants

If you have questions about O-Ring materials, contact Gallagher Fluid Seals, Inc. Our experts can answer any questions you might have about these small, yet crucial, sealing products.

You can also learn more about O-Rings by downloading this guide, which discusses their technical performance characteristics, materials, chemical and temperature compatibility, hardware considerations and failure modes.

How to Choose O-Ring Material for Your Fluid Sealing

O-rings are one of the most commonly used fluid power seals. These seals have a simple donut-shaped design (technically called a toroid) and are made using pliable materials such as elastomers like silicone, Buna-N, and Ethylene-Propylene. O-rings are installed to seal connections between connectors, pipes, etc., via mechanical deformation. Once installed, O-rings ensure no liquid or air passes through the designated area.

Since O-rings need to perform effectively, selecting the right material is crucial. The crash of the space shuttle Challenger in 1986 is a well-documented case of what failure of O-rings can do. Today, O-rings are manufactured using thousands of different materials that perform differently under various conditions. Below are some common materials used for O-rings, their operating temperatures, hardness scores, standard colors, and limitations. Complete O-ring material compatibility for various applications can be found here.

Seal Material: Alfas®

• Hardness (Shore A): 60-90
• Standard Color: Black
• Working Temperature: -14° to +446°F (Standard Compound)
• Key Uses: Seals for aerospace, oil-related seals, industrial environment
• Features: High temperature and chemical resistance
• Limitations: Not recommended for seals involving toluene, ether, ketone, and acetic acid

Seal Material: Fluorocarbons

• Hardness (Shore A): 55-90
• Standard Color: Black
• Working Temperature: -13° to +446°F (Standard Compound)
• Key Uses: Aircraft engines, automotive fuel handling systems, low compression or high temperature seals
• Features: High fluorine grade offers better performance in methanol/ethanol blended gasoline
• Limitations: Avoid exposure to amines, low molecular weight esters and ethers, Skydrol® fluids, hot hydrofluoric acids

Seal Material: Buna-N

• Hardness (Shore A): 40-90
• Standard Color: Black
• Working Temperature: -40° to +257°F (Standard Compound)
• Key Uses: Oil resistance, aerospace, off-road equipment, FDA applications
• Features: Can work as low as -85°F, more abrasion resistant
• Limitations: Prone to ozone reaction, may seep out causing issues with certain plastics

Seal Material: Butyl

• Hardness (Shore A): 30-90
• Standard Color: Black
• Working Temperature: 50° to +250°F (Standard Compound)
• Key Uses: Hydraulic systems, vacuum sealing
• Features: Low permeability to gases, inert to ozone and sunlight, good shock absorbing abilities
• Limitations: Reactive to hydrocarbon solvents and oils

Seal Material: Perfluoroelastomer

• Hardness (Shore A): 65-90
• Standard Color: Black
• Working Temperature: -13°F to +600°F (Standard Compound)
• Key Uses: Chemical and petroleum industries, high temperatures, paint and coating operations
• Features: Combines toughness of elastomeric material with chemical inertness of Teflon®
• Limitations: Can swell significantly when exposed to some fluorinated solvents

Seal Material: Fluorosilicone

• Hardness (Shore A): 40-80
• Standard Color: Blue
• Working Temperature: 75°F to +400°F (Standard Compound)
• Key Uses: Static sealing, air fuel emission control system, aerospace fuel system
• Features: Good compression set, resilience properties
• Limitations: Not recommended for dynamic sealing due to limited physical strength, high friction

Seal Material: Silicone

• Hardness (Shore A): 20-80
• Standard Color: Red
• Working Temperature: -85° to 400°F
• Key Uses: High temperature seals
• Features: Phenyl-based silicones function down to -148°F
• Limitations: Low abrasion and tear resistance, not suitable for dynamic seals

Seal Material: Natural Rubber

• Hardness (Shore A): 40-90
• Standard Color: Black, Brown/Beige
• Working Temperature: -58°F to +158°F (Standard Compound)
• Key Uses: Food and beverage seals, non-hydraulic sealing applications, dampeners
• Features: High tensile strength, resilience, abrasion and tear resistance
• Limitations: Poor compression set performance, lack of fluid flow resistance

Seal Material: Polyacrylate

• Hardness (Shore A): 40-90
• Standard Color: Black
• Working Temperature: -25°F to +300°F, Standard Compound
• Key Uses: Automatic transmissions, automotive power steering systems, petroleum oils
• Features: Resistant to sunlight, ozone degradation, flex cracking
• Limitations: Poor performance at low temperatures, bad water resistance

Seal Material: Teflon® (Polytetrafluoroethylene)

• Hardness (Shore A): 98
• Standard Color: White
• Working Temperature: -300°F to +450°F (Standard Compound)
• Key Uses: Static and slow intermittent dynamic seals
• Features: Almost inert to all industry chemicals, high endurance, ozone resistant
• Limitations: Poor elastic memory, poor tear resistance, high installation cost

Seal Material: Polyurethane, Cast

• Hardness (Shore A): 70-90
• Standard Color: Amber
• Working Temperature: -30°F to +175°F (Standard Compound)
• Key Uses: High hydraulic pressure seals, dynamic seals
• Features: High tensile strength, abrasion resistance, compatibility with weak acids, bases
• Limitations: Poor performance with esters, ketones, concentrated bases and acids

Seal Material: Polyurethane, Millable

• Hardness (Shore A): 40-90
• Standard Color: Black
• Working Temperature: -30°F to +175°F (Standard Condition)
• Key Uses: Static seals, hydraulic situations, medical devices
• Features: Good tear resistance, performs well at high pressure, shock loads
• Limitations: Loses shape at high temperatures, not suitable for high-temperature locations