A variety of materials are used to manufacture industrial seals. This article introduces the hydraulic seal materials that are suitable for petroleum-based hydraulic oil applications. The main types of seals used with oil-based systems include rubber seals, polyurethane seals, and PTFE seals.
Common Materials for Petroleum-Based Hydraulic Oil Seals
Below are commonly used materials that are compatible with petroleum-based hydraulic oil:
NBR (Nitrile Rubber) Seals
Nitrile rubber is compatible with media such as petroleum-based hydraulic oil, glycol-based hydraulic fluids, diester-based lubricants, gasoline, water, grease, and other oils. It is currently the most widely used and cost-effective rubber sealing material. However, it is not suitable for polar solvents like ketones, ethers, nitro compounds, MEK (methyl ethyl ketone), or chloroform. Typical operating temperature range: -40°C to 120°C.
HNBR (Hydrogenated Nitrile Rubber) Seals
Hydrogenated nitrile rubber offers excellent resistance to corrosion, tearing, and compression set. It also provides good resistance to ozone, UV light, and weathering. Compared to standard nitrile rubber, it offers superior wear resistance. Common applications include washing machines, automotive engine systems, and refrigeration systems using environmentally friendly refrigerant R134a. Not recommended for use in alcohols, coolants, or aromatic solutions. Typical operating temperature range: -40°C to 150°C.
Viton® (FKM/Fluorocarbon Rubber) Seals
Fluorocarbon rubber has better high-temperature resistance than silicone rubber and excels in resistance to weathering, ozone, and chemicals. However, it has poor low-temperature performance. It is resistant to most oils and solvents, especially acids, aliphatic and aromatic hydrocarbons, and animal or vegetable oils. Suitable for diesel engines, fuel systems, and chemical processing environments. Not recommended for use with ketones, low molecular weight esters, or nitric acid mixtures. Typical operating temperature range: -20°C to 250°C.
PU (Polyurethane) Seals
Polyurethane exhibits excellent mechanical properties, with wear and high-pressure resistance significantly superior to other rubber materials. It also has good resistance to aging, ozone, and oil, though it can hydrolyze at elevated temperatures. Commonly used in high-pressure, high-wear applications such as hydraulic cylinders. Typical operating temperature range: -45°C to 90°C.
PTFE (Polytetrafluoroethylene) Seals
PTFE is highly resistant to various hydraulic oils and chemicals, offering outstanding media compatibility and stability in high-temperature and corrosive environments. This makes it an ideal material for both sealing and lubrication. Hydraulic oil typically consists of base oil (often mineral or synthetic) and performance-enhancing additives. PTFE also features an extremely low coefficient of friction, excellent wear resistance, and high thermal tolerance. Modified PTFE variants can further enhance performance and extend service life. Typical operating temperature range: -200°C to +260°C.
Important Considerations
When selecting hydraulic seals for use with petroleum-based hydraulic oil, keep the following in mind:
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Choose the right material for the medium. Incompatible materials may lead to seal failure.
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Match the seal’s size and hardness to working conditions, including temperature and pressure.
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Install seals properly with correct lubrication to ensure reliable performance and extended lifespan.
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Regular inspection and maintenance of seals should be performed to identify wear or aging early and replace seals before leaks occur.
This article provides an overview of seal materials suitable for petroleum-based hydraulic oil and highlights key considerations for selection and use. I hope it offers useful guidance for your sealing applications.
