Hydraulic Material Compatibility Chart

Hydraulic systems operate under demanding conditions involving high pressures, varying temperatures, and continuous fluid circulation. While selecting the correct hydraulic fluid is critical, choosing compatible materials for seals, hoses, tubes, valves, pumps, and fittings is equally important. Even the best hydraulic fluid can cause premature component failure if it reacts negatively with system materials.

A hydraulic material compatibility chart is a valuable engineering reference that helps designers, maintenance personnel, and system operators determine whether a particular material can safely operate with a specific hydraulic fluid. These charts provide compatibility ratings that indicate the likelihood of swelling, cracking, corrosion, hardening, softening, or chemical degradation when materials are exposed to different hydraulic fluids.

Material incompatibility is one of the leading causes of hydraulic leaks, seal failures, contamination issues, and unexpected downtime. For example, an elastomer seal that performs perfectly with mineral oil may rapidly deteriorate when exposed to phosphate ester fluid. Similarly, certain metals can corrode when used with water-based hydraulic fluids, reducing equipment reliability and service life.

This guide explains how hydraulic material compatibility charts work, the common materials used in hydraulic systems, and how engineers use compatibility data to select the best materials for long-term performance and safety.

1. What Is a Hydraulic Material Compatibility Chart?

A hydraulic material compatibility chart is a reference table that shows how various materials react when exposed to specific hydraulic fluids. The chart helps engineers and technicians determine whether a material is suitable for use in a hydraulic system based on its resistance to chemical attack, swelling, corrosion, softening, embrittlement, or other forms of degradation.

The primary purpose of a compatibility chart is to prevent failures caused by adverse chemical interactions between hydraulic fluids and system components. Since hydraulic systems contain numerous materials—including metals, elastomers, plastics, and composite materials—it is essential to ensure that every component can withstand long-term exposure to the selected hydraulic fluid.

Compatibility charts typically cover materials such as:

• Nitrile rubber (NBR)
• Viton (FKM)
• EPDM
• PTFE (Teflon)
• Polyurethane
• Carbon steel
• Stainless steel
• Brass
• Aluminum
• Thermoplastics

Likewise, they evaluate compatibility with common hydraulic fluids, including:

• Mineral oil hydraulic fluids
• Synthetic hydraulic fluids
• Water-glycol fluids
• Biodegradable hydraulic fluids
• Phosphate ester fire-resistant fluids
• Polyalphaolefin (PAO) fluids
• Synthetic ester fluids

Most hydraulic compatibility charts use a rating system similar to the following:

Rating	Meaning
Excellent	Material shows little or no degradation after long-term exposure
Good	Minor changes may occur but performance remains acceptable
Fair	Material may experience moderate degradation and should be evaluated carefully
Poor	Significant deterioration is likely; material is generally not recommended
Not Recommended	Severe damage or failure is expected

For example, PTFE is considered one of the most chemically resistant materials and typically receives an “Excellent” rating with nearly all hydraulic fluids. In contrast, EPDM may be highly compatible with water-glycol fluids but unsuitable for petroleum-based hydraulic oils.

Engineers often use hydraulic material compatibility charts during:

• Hydraulic system design
• Component selection
• Seal replacement projects
• Hydraulic fluid conversion programs
• Preventive maintenance planning
• Failure investigations

Because operating temperature, pressure, fluid additives, and exposure duration can influence compatibility, charts should be used as a guideline rather than an absolute guarantee. Whenever possible, compatibility recommendations should be verified with component manufacturers and supported by field testing for critical applications.

A properly used hydraulic material compatibility chart helps reduce maintenance costs, improve system reliability, minimize downtime, and extend the service life of hydraulic equipment.

2. Why Material Compatibility Matters in Hydraulic Systems

Material compatibility plays a critical role in hydraulic system reliability, efficiency, and safety. Hydraulic systems contain numerous components made from different materials, including metal tubing, elastomer seals, hoses, O-rings, pump components, and valve assemblies. When these materials are exposed to incompatible hydraulic fluids, their physical and chemical properties can change, leading to performance problems and premature failures.

Seal Swelling and Shrinkage

One of the most common compatibility issues involves hydraulic seals and O-rings. Certain hydraulic fluids can cause elastomer materials to absorb fluid and swell beyond their designed dimensions. Excessive swelling may increase friction, create installation problems, or cause seals to extrude under pressure.

Conversely, incompatible fluids can extract plasticizers from elastomers, causing shrinkage and hardening. Shrunken seals may lose contact with sealing surfaces, resulting in leakage and contamination.

Hose and Tube Degradation

Hydraulic hoses rely on inner tube materials that must remain chemically stable when exposed to hydraulic fluid. Incompatible fluids can soften hose liners, weaken reinforcement layers, or cause cracking over time.

The consequences may include:

• Reduced pressure capability
• Internal leakage
• Hose blistering
• Premature hose failure
• Increased maintenance costs

While metal tubing generally offers excellent chemical resistance, certain fluid and material combinations can still promote corrosion or stress cracking under severe operating conditions.

Corrosion of Metallic Components

Hydraulic systems commonly use carbon steel, stainless steel, brass, and aluminum components. Some hydraulic fluids, especially water-based fluids and aggressive synthetic fluids, can accelerate corrosion if incompatible metals are selected.

Corrosion can lead to:

• Reduced component strength
• Flow restrictions
• Contamination generation
• Valve sticking
• Pump wear

The resulting particles often circulate throughout the hydraulic system, damaging sensitive components and reducing overall equipment life.

Contamination and Fluid Degradation

When incompatible materials break down, they release particles and chemical residues into the hydraulic fluid. This contamination may clog filters, damage pumps, restrict valves, and accelerate wear throughout the system.

In severe cases, material degradation can alter the chemical composition of the hydraulic fluid itself, reducing lubrication performance and increasing oxidation rates.

Impact on Reliability and Safety

Material compatibility directly affects system uptime and safety. Failures caused by incompatible seals, hoses, or fittings can lead to:

• Unexpected downtime
• Environmental spills
• Equipment damage
• Fire hazards
• Safety risks for personnel

For this reason, hydraulic engineers carefully evaluate material compatibility during system design and maintenance planning. A properly selected combination of fluid and material helps maximize service life, improve reliability, and reduce total ownership costs.

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3. Hydraulic Fluids and Their Compatibility Characteristics

Different hydraulic fluids possess unique chemical properties that influence their compatibility with seals, metals, plastics, and hose materials. Understanding these characteristics is essential when using a hydraulic material compatibility chart.

Mineral Oil-Based Hydraulic Fluids

Mineral oil hydraulic fluids are the most widely used fluids in industrial and mobile hydraulic systems. They offer excellent lubrication, good thermal stability, and relatively low cost.

Typical compatibility:

• Excellent with NBR (Buna-N)
• Excellent with FKM (Viton)
• Excellent with carbon steel
• Excellent with stainless steel
• Poor with EPDM

Because mineral oil fluids are petroleum-based, they can cause certain elastomers such as EPDM to swell excessively and lose mechanical properties.

Water-Glycol Hydraulic Fluids

Water-glycol fluids are commonly used in applications where fire resistance is required. These fluids contain a mixture of water and glycol that provides both lubrication and flame resistance.

Typical compatibility:

• Excellent with EPDM
• Good with PTFE
• Good with stainless steel
• Fair with NBR
• Poor with some polyurethane materials

Because water is a major component, corrosion protection becomes particularly important when selecting metallic components.

Phosphate Ester Hydraulic Fluids

Phosphate ester fluids are highly fire-resistant and are often used in power generation, aviation, and steel manufacturing applications.

Typical compatibility:

• Excellent with EPDM
• Excellent with PTFE
• Good with FKM
• Poor with NBR
• Poor with polyurethane

These fluids are chemically aggressive and require special attention during material selection. Using standard seals designed for mineral oil systems often results in rapid deterioration.

Synthetic Hydraulic Fluids

Synthetic hydraulic fluids include polyalphaolefin (PAO), synthetic esters, and other specially engineered lubricants designed for extreme operating conditions.

Advantages include:

• Wider temperature range
• Improved oxidation resistance
• Longer service life
• Better low-temperature performance

Compatibility varies significantly depending on the specific synthetic chemistry, making manufacturer recommendations particularly important.

Biodegradable Hydraulic Fluids

Biodegradable fluids are increasingly used in environmentally sensitive applications such as forestry, marine equipment, agriculture, and construction.

Common types include:

• Vegetable oil-based fluids
• Synthetic ester fluids
• Biodegradable synthetic blends

These fluids may provide excellent environmental benefits but can sometimes present compatibility challenges with conventional seal materials.

Fire-Resistant Hydraulic Fluids

Fire-resistant fluids are designed to reduce ignition risks in hazardous operating environments. Major categories include:

• Water-glycol fluids
• Phosphate ester fluids
• Water-in-oil emulsions
• Synthetic fire-resistant fluids

While these fluids improve safety, they often require specialized seals, hoses, coatings, and metallic materials to achieve long-term reliability.

Understanding the chemical behavior of each hydraulic fluid is the foundation of proper material selection. Before choosing seals, hoses, fittings, or valves, engineers should always consult a hydraulic material compatibility chart to verify long-term compatibility with the intended fluid.

4. Common Materials Used in Hydraulic Systems

Hydraulic systems contain a wide variety of materials designed to withstand pressure, temperature fluctuations, fluid exposure, and environmental conditions. Each material offers unique advantages and compatibility characteristics. Selecting the correct material is essential for achieving maximum system reliability and service life.

Carbon Steel

Carbon steel is one of the most commonly used materials in hydraulic systems due to its strength, durability, and affordability.

Applications include:

• Hydraulic tubing
• Pipe fittings
• Pump housings
• Valve bodies
• Hydraulic cylinders

Advantages:

• High strength
• Excellent pressure resistance
• Cost-effective

Limitations:

• Susceptible to corrosion in water-containing fluids
• Requires protective coatings in harsh environments

Carbon steel generally exhibits excellent compatibility with mineral oil-based hydraulic fluids.

Stainless Steel

Stainless steel provides superior corrosion resistance and is widely used in demanding industrial, offshore, marine, and food-processing applications.

Advantages:

• Excellent corrosion resistance
• High temperature capability
• Long service life
• Compatible with most hydraulic fluids

Common grades include:

• 304 Stainless Steel
• 316 Stainless Steel
• 316L Stainless Steel

Because of its chemical resistance, stainless steel is often the preferred material for systems using water-glycol, synthetic, or phosphate ester fluids.

Brass

Brass is frequently used in low-pressure hydraulic applications and instrumentation systems.

Advantages:

• Corrosion resistant
• Easy to machine
• Good thermal conductivity

Typical applications:

• Instrument fittings
• Pressure gauges
• Low-pressure valves

Brass performs well with many hydraulic fluids but may not be suitable for highly aggressive chemical environments.

Aluminum

Aluminum is valued for its lightweight characteristics and excellent machinability.

Common applications:

• Hydraulic manifolds
• Reservoirs
• Mobile equipment components

Advantages:

• Lightweight
• Good corrosion resistance
• Easy fabrication

However, some hydraulic fluids and additives may accelerate aluminum corrosion under certain conditions.

PTFE (Teflon)

PTFE is considered one of the most chemically resistant materials used in hydraulic systems.

Advantages:

• Outstanding chemical resistance
• Wide temperature range
• Low friction coefficient
• Excellent compatibility with most hydraulic fluids

Applications:

• Seal backup rings
• Hose liners
• Valve seats
• Gaskets

PTFE is often the safest choice when compatibility concerns exist.

Polyurethane

Polyurethane is commonly used in hydraulic seals due to its excellent wear resistance and mechanical strength.

Advantages:

• High abrasion resistance
• Excellent pressure capability
• Good tear resistance

Applications:

• Rod seals
• Piston seals
• Wipers

Compatibility should be verified when using water-based or phosphate ester fluids.

Nylon

Nylon is widely used in hydraulic fittings, tubing, and certain plastic components.

Advantages:

• Lightweight
• Strong
• Cost-effective

Limitations:

• Can absorb moisture
• May be affected by some synthetic fluids

Nitrile Rubber (NBR)

NBR, also known as Buna-N, is the most widely used hydraulic seal material.

Advantages:

• Excellent compatibility with petroleum-based fluids
• Low cost
• Good wear resistance

Limitations:

• Poor compatibility with phosphate ester fluids
• Limited ozone resistance

Viton (FKM)

FKM elastomers provide excellent chemical and temperature resistance.

Advantages:

• High-temperature capability
• Excellent chemical resistance
• Long service life

Applications:

• High-performance hydraulic systems
• Aerospace equipment
• Chemical processing systems

EPDM

EPDM performs exceptionally well with water-based hydraulic fluids.

Advantages:

• Excellent resistance to water and steam
• Good weather resistance

Limitations:

• Poor compatibility with mineral oil-based hydraulic fluids

Selecting the proper material requires evaluating both mechanical requirements and fluid compatibility characteristics.

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5. Hydraulic Seal Material Compatibility Chart

Hydraulic seals are among the most critical components in any hydraulic system. They prevent fluid leakage, maintain pressure, and protect components from contamination. Since seals remain in constant contact with hydraulic fluid, compatibility between the seal material and fluid is essential.

Improper material selection can cause:

• Swelling
• Hardening
• Cracking
• Shrinkage
• Extrusion
• Premature seal failure

The following compatibility chart provides general guidance for common hydraulic seal materials.

Hydraulic Seal Compatibility Chart

Hydraulic Fluid	NBR (Buna-N)	FKM (Viton)	EPDM	PTFE	Polyurethane
Mineral Oil	Excellent	Excellent	Poor	Excellent	Excellent
Water-Glycol	Good	Fair	Excellent	Excellent	Good
Phosphate Ester	Poor	Good	Excellent	Excellent	Poor
Synthetic Ester	Good	Excellent	Fair	Excellent	Good
Biodegradable Fluids	Good	Good	Fair	Excellent	Good
Fire-Resistant Fluids	Fair	Good	Excellent	Excellent	Fair

NBR (Buna-N)

NBR is the industry standard seal material for petroleum-based hydraulic fluids.

Advantages:

• Economical
• Widely available
• Excellent performance with mineral oils

Typical operating temperature:

-40°F to 250°F (-40°C to 121°C)

FKM (Viton)

FKM offers superior chemical and temperature resistance compared with NBR.

Advantages:

• Excellent resistance to synthetic fluids
• High-temperature capability
• Long service life

Typical operating temperature:

-15°F to 400°F (-26°C to 204°C)

EPDM

EPDM is the preferred choice for water-based hydraulic fluids.

Advantages:

• Outstanding water resistance
• Excellent compatibility with phosphate esters

Limitations:

• Not suitable for petroleum oils

PTFE

PTFE is often considered the universal hydraulic sealing material.

Advantages:

• Exceptional chemical resistance
• Wide operating temperature range
• Low friction

PTFE maintains excellent compatibility with nearly all hydraulic fluids.

Polyurethane

Polyurethane seals are popular in high-pressure hydraulic applications.

Advantages:

• Superior wear resistance
• Excellent extrusion resistance
• High load-carrying capability

However, compatibility should be carefully verified when fire-resistant or phosphate ester fluids are used.

Although compatibility charts provide an excellent starting point, engineers should always consult seal manufacturers for application-specific recommendations, particularly in high-temperature, high-pressure, or safety-critical hydraulic systems.

6. Hydraulic Hose and Tube Material Compatibility Chart

Hydraulic hoses and tubing serve as the arteries of a hydraulic system, transporting pressurized fluid between pumps, valves, actuators, and reservoirs. Because they remain in direct contact with hydraulic fluid throughout their service life, material compatibility is essential for ensuring long-term reliability and safety.

An incompatible hose or tube material may experience softening, cracking, blistering, corrosion, or internal degradation, leading to leaks, pressure loss, and system failure.

Common Hydraulic Hose and Tube Materials

The most frequently used materials include:

• Carbon steel tubing
• Stainless steel tubing
• Rubber hydraulic hose
• Thermoplastic hose
• PTFE hose
• Nylon tubing

Each material exhibits different levels of compatibility with various hydraulic fluids.

Hydraulic Hose and Tube Compatibility Chart

Material	Mineral Oil	Water-Glycol	Phosphate Ester	Synthetic Fluid	Biodegradable Fluid
Carbon Steel	Excellent	Good	Fair	Good	Good
Stainless Steel	Excellent	Excellent	Excellent	Excellent	Excellent
Rubber Hose	Excellent	Good	Fair	Good	Good
Thermoplastic Hose	Good	Good	Fair	Good	Good
PTFE Hose	Excellent	Excellent	Excellent	Excellent	Excellent
Nylon Tubing	Good	Fair	Poor	Good	Fair

Steel Tubing Compatibility

Carbon steel tubing remains the industry standard for many hydraulic applications.

Advantages:

• High pressure capability
• Excellent mechanical strength
• Cost-effective

Limitations:

• Susceptible to corrosion in water-based systems
• May require coatings in harsh environments

Carbon steel performs exceptionally well with petroleum-based hydraulic fluids but requires additional attention when water-glycol fluids are used.

Stainless Steel Tubing Compatibility

Stainless steel provides superior corrosion resistance and broad fluid compatibility.

Advantages:

• Excellent chemical resistance
• Long service life
• Suitable for offshore environments
• Ideal for aggressive hydraulic fluids

Applications:

• Marine systems
• Offshore platforms
• Food processing equipment
• Chemical plants
• Semiconductor manufacturing

For demanding environments, stainless steel is often considered the safest material choice.

Rubber Hydraulic Hose Compatibility

Rubber hydraulic hoses are widely used due to their flexibility and vibration resistance.

Advantages:

• Flexible routing
• Shock absorption
• Cost-effective

Common inner tube materials include:

• NBR
• Synthetic rubber blends
• Specialized elastomers

Compatibility depends heavily on the specific rubber compound used by the manufacturer.

Thermoplastic Hose Compatibility

Thermoplastic hoses are becoming increasingly popular in mobile and industrial hydraulic systems.

Advantages:

• Lightweight
• Corrosion resistant
• Flexible
• Compact design

These hoses often perform well with synthetic and biodegradable fluids, although compatibility should always be verified.

PTFE Hose Compatibility

PTFE-lined hose offers the broadest chemical resistance among hydraulic hose materials.

Advantages:

• Compatible with nearly all hydraulic fluids
• Excellent temperature resistance
• Low friction
• Long service life

Applications:

• Aerospace systems
• High-temperature hydraulics
• Chemical processing equipment

When fluid compatibility is uncertain, PTFE hose is frequently the preferred solution.

Factors Affecting Hose and Tube Compatibility

Compatibility ratings can change based on:

• Operating temperature
• Fluid additives
• Pressure cycling
• Exposure duration
• Environmental conditions

For critical applications, hose manufacturers should always be consulted before final material selection.

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7. Hydraulic Material Compatibility Chart by Component

Different hydraulic components operate under unique conditions and therefore require specific material selections. While a seal may prioritize chemical resistance, a pump housing may prioritize strength and corrosion resistance.

This section examines compatibility considerations for major hydraulic components.

Hydraulic Pumps

Hydraulic pumps contain multiple materials including:

• Cast iron housings
• Steel shafts
• Bronze bearings
• Elastomer seals

Recommended materials:

Component	Preferred Material
Housing	Cast Iron or Steel
Shaft	Hardened Steel
Seals	NBR, FKM, PTFE
Bearings	Bronze or Stainless Steel

For phosphate ester fluids, FKM and PTFE seals are generally preferred over NBR.

Hydraulic Valves

Hydraulic valves require materials capable of handling high-pressure fluid flow and repeated cycling.

Recommended materials:

Component	Preferred Material
Valve Body	Carbon Steel or Stainless Steel
Internal Components	Hardened Steel
Seals	NBR, FKM, PTFE

Stainless steel valve bodies are often selected for corrosive or water-based hydraulic systems.

Hydraulic Cylinders

Hydraulic cylinders combine metallic structures with dynamic sealing elements.

Typical materials:

• Steel cylinder barrel
• Chrome-plated rod
• Polyurethane seals
• PTFE wear rings

Compatibility concerns primarily involve seal materials and corrosion protection.

Hydraulic Accumulators

Accumulators store hydraulic energy using compressed gas and hydraulic fluid separation.

Common bladder materials:

• NBR
• FKM
• EPDM

Fluid compatibility is critical because bladder failure can render the accumulator unusable.

Hydraulic Fittings

Hydraulic fittings must resist pressure, vibration, and fluid exposure.

Common materials:

• Carbon steel
• Stainless steel
• Brass

Material selection depends on:

• Fluid chemistry
• Operating pressure
• Corrosion risk
• Environmental exposure

Hydraulic Filters

Filters contain various materials that must remain chemically stable.

Typical materials:

• Steel housings
• Synthetic filter media
• Nitrile seals
• Stainless steel support mesh

Aggressive fluids may require upgraded seal and media materials.

Hydraulic Reservoirs

Reservoirs store hydraulic fluid and provide cooling, deaeration, and contamination control.

Common materials:

• Carbon steel
• Stainless steel
• Aluminum

Selection considerations include:

• Fluid compatibility
• Corrosion resistance
• Cost
• Weight requirements

Component Selection Best Practices

When selecting materials for hydraulic components:

1. Identify the hydraulic fluid type.
2. Review compatibility charts.
3. Verify temperature limits.
4. Check pressure requirements.
5. Consult manufacturer recommendations.
6. Consider future fluid conversions.

Using a hydraulic material compatibility chart during component selection helps prevent premature failures, reduce maintenance costs, and improve overall hydraulic system performance.

8. How to Use a Hydraulic Material Compatibility Chart

A hydraulic material compatibility chart is only valuable when used correctly. Engineers and maintenance personnel should evaluate compatibility as part of the overall system design process rather than relying solely on a simple rating table.

Step 1: Identify the Hydraulic Fluid

Begin by determining the exact hydraulic fluid being used.

Examples include:

• Mineral oil hydraulic fluid
• Water-glycol fluid
• Phosphate ester fluid
• Synthetic ester fluid
• PAO synthetic fluid
• Biodegradable hydraulic fluid

Even fluids within the same category may contain additives that influence compatibility.

Step 2: Identify All Wetted Materials

Review every component that comes into contact with the fluid, including:

• Seals
• O-rings
• Hoses
• Tubes
• Fittings
• Pumps
• Valves
• Reservoirs

A system is only as reliable as its least compatible component.

Step 3: Check Compatibility Ratings

Locate the fluid and material combination within the chart and review its rating.

General interpretation:

• Excellent = Preferred choice
• Good = Suitable for most applications
• Fair = Evaluate carefully
• Poor = Avoid if possible
• Not Recommended = Do not use

Step 4: Consider Temperature Effects

Many compatibility ratings are based on standard laboratory conditions.

Higher temperatures can:

• Accelerate chemical reactions
• Increase seal swelling
• Promote oxidation
• Reduce material life

Always verify compatibility at actual operating temperatures.

Step 5: Evaluate Pressure and Duty Cycle

Pressure cycling can accelerate material fatigue even when chemical compatibility appears acceptable.

Consider:

• Continuous operation
• Shock loading
• Pressure spikes
• Start-stop cycles

Step 6: Verify Manufacturer Recommendations

Component manufacturers often provide more specific compatibility information than general charts.

Always consult:

• Seal manufacturers
• Hose manufacturers
• Pump manufacturers
• Valve manufacturers

This is especially important for critical applications.

Step 7: Perform Field Testing When Necessary

For highly specialized systems, laboratory testing or pilot installations may be justified before full deployment.

Testing can reveal compatibility issues that are not immediately apparent from published charts.

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9. Best Practices for Material Selection in Hydraulic Systems

Choosing compatible materials is one of the most effective ways to improve hydraulic system performance and reliability.

Match Materials to Fluid Chemistry

Always begin material selection by understanding the chemical properties of the hydraulic fluid.

Questions to ask:

• Is the fluid petroleum-based?
• Is it water-based?
• Is it synthetic?
• Is it fire-resistant?

The answers will significantly influence material selection.

Consider Future Fluid Changes

Many systems eventually switch fluids because of:

• Environmental regulations
• Fire safety requirements
• Cost reductions
• Performance improvements

Selecting materials with broad compatibility can reduce future upgrade costs.

Use Stainless Steel in Corrosive Environments

Although stainless steel is more expensive than carbon steel, it often delivers lower lifecycle costs in:

• Offshore facilities
• Chemical plants
• Marine applications
• Food processing systems

Standardize Seal Materials

Using a limited number of approved seal materials simplifies:

• Maintenance
• Inventory management
• Procurement
• Training

Many facilities standardize around NBR, FKM, and PTFE.

Prioritize PTFE for Maximum Compatibility

PTFE offers one of the broadest compatibility ranges available.

Advantages include:

• Chemical resistance
• Temperature resistance
• Low friction
• Long service life

While more expensive, PTFE often reduces long-term maintenance costs.

Follow Industry Standards

Material selection should align with recognized standards such as:

• ISO 4413
• ISO 11158
• SAE J514
• SAE J517
• NFPA T2 standards

These standards help ensure safety and reliability.

Maintain Fluid Cleanliness

Even compatible materials can fail prematurely if contamination levels become excessive.

Best practices include:

• Routine oil analysis
• Filter monitoring
• Clean fluid handling
• Scheduled maintenance

Material compatibility and contamination control work together to maximize equipment life.

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10. Frequently Asked Questions (FAQs)

What materials are most compatible with hydraulic oil?

For mineral oil-based hydraulic fluids, the most compatible materials generally include:

• NBR (Buna-N)
• FKM (Viton)
• PTFE
• Carbon steel
• Stainless steel

These materials are widely used throughout the hydraulic industry.

Is Viton better than NBR for hydraulic systems?

Not necessarily.

NBR is often the preferred choice for conventional petroleum-based hydraulic fluids because it is economical and highly effective.

Viton offers:

• Better chemical resistance
• Higher temperature capability
• Longer service life

However, it is typically more expensive.

Can stainless steel be used with all hydraulic fluids?

Stainless steel provides excellent compatibility with nearly all common hydraulic fluids.

It is particularly valuable for:

• Water-glycol systems
• Synthetic fluids
• Corrosive environments
• Offshore applications

However, compatibility should still be verified for highly specialized chemicals.

What seal material works best with phosphate ester fluids?

EPDM and PTFE are generally considered the best choices for phosphate ester fluids.

NBR is usually not recommended because phosphate esters can cause rapid degradation.

Does operating temperature affect compatibility?

Yes.

Temperature can significantly impact:

• Seal swelling
• Chemical attack rates
• Oxidation
• Material aging

A material rated “Good” at room temperature may perform poorly at elevated temperatures.

How often should compatibility be reviewed?

Compatibility should be reviewed whenever:

• A hydraulic fluid is changed
• New equipment is installed
• Operating temperatures increase
• Persistent seal failures occur
• New maintenance standards are adopted

Regular reviews help prevent costly reliability issues.

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Conclusion

A hydraulic material compatibility chart is one of the most valuable tools available for hydraulic system design, maintenance, and troubleshooting. By understanding how hydraulic fluids interact with seals, hoses, tubes, fittings, pumps, valves, and other components, engineers can make informed decisions that improve system reliability and reduce maintenance costs.

Proper material selection helps prevent leaks, corrosion, contamination, seal degradation, and premature equipment failure. Whether a system uses conventional mineral oil, water-glycol fluid, phosphate ester fluid, or biodegradable hydraulic fluid, compatibility should always be evaluated before installation or fluid conversion.

Although compatibility charts provide an excellent starting point, they should be used alongside manufacturer recommendations, industry standards, operating temperature considerations, and real-world application requirements. A proactive approach to material compatibility not only extends equipment life but also improves safety, efficiency, and overall hydraulic system performance.

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