When selecting seals for industrial applications, it’s easy to focus on size, pressure ratings, or temperature limits. But one of the most common - and costly - causes of seal failure is often overlooked: chemical compatibility.

Choosing the wrong seal material for the chemicals it will encounter can lead to premature failure, equipment damage, unplanned downtime, and safety risks. Understanding chemical compatibility is essential to selecting seals that perform reliably and last as long as intended.

What Is Chemical Compatibility?

Chemical compatibility refers to how well a seal material withstands exposure to specific chemicals without degrading. When a seal is incompatible with the media it contacts, it may experience:

• Swelling or shrinkage
• Hardening or softening
• Loss of elasticity
• Cracking, blistering, or chemical attack
• Leaching of additives

Any of these changes can compromise sealing performance, leading to leaks or total system failure.

Why Chemical Compatibility Matters in Seal Performance

Seals are designed to maintain a tight barrier under dynamic or static conditions. When chemical incompatibility occurs, even a perfectly sized seal can fail quickly.

Key impacts of poor compatibility include:

• Reduced seal life - Materials degrade faster when exposed to incompatible fluids.
• Increased maintenance costs - Frequent seal replacement leads to higher labor and downtime expenses.
• Equipment damage - Leaks can damage bearings, pumps, housings, or adjacent components.
• Safety and environmental risks - Chemical leaks may pose hazards to operators or violate environmental regulations.

In many cases, the seal itself isn’t defective - it was simply made from the wrong material.

Common Chemicals That Cause Seal Issues

Many industrial environments expose seals to aggressive media, including:

• Oils and fuels
• Solvents and cleaning agents
• Acids and bases
• Coolants and hydraulic fluids
• Disinfectants and sterilization chemicals
• Agricultural chemicals and fertilizers

Even chemicals that seem benign can become problematic at higher temperatures, pressures, or concentrations.

How Seal Materials React to Chemicals

Different elastomers and polymers respond very differently to chemical exposure. For example:

• Nitrile (NBR) performs well with petroleum-based oils but degrades in ozone, sunlight, and certain solvents.
• EPDM is excellent for water, steam, and many chemicals but is not compatible with oils and fuels.
• FKM (Viton®) offers broad chemical resistance but may not perform well with certain amines or hot water/steam.
• PTFE provides outstanding chemical resistance but lacks elasticity and may require special design considerations.
• FFKM offers near-universal chemical compatibility but comes at a significantly higher cost.

Selecting the right material requires understanding both the chemical environment and the mechanical demands of the application.

Factors That Influence Chemical Compatibility

Chemical resistance isn’t determined by the fluid alone. Several factors influence how a seal material will perform:

• Temperature - Higher temperatures accelerate chemical reactions and material degradation.
• Pressure - Increased pressure can force chemicals deeper into the material.
• Concentration - Higher chemical concentrations are often more aggressive.
• Exposure time - Continuous exposure is more damaging than intermittent contact.
• Dynamic vs. static sealing – Moving seals are more vulnerable to material changes.

This is why compatibility charts should be used as a guide - not a guarantee.

The Limitations of Chemical Compatibility Charts

Chemical compatibility charts are valuable tools, but they have limitations:

• They are typically based on laboratory conditions.
• They may not account for temperature extremes or mixed chemicals.
• They don’t reflect real-world variables like cycling, abrasion, or contamination.

Relying solely on a chart without application context can lead to incorrect material selection.

The Role of Engineering Support in Seal Selection

This is where engineering expertise adds real value. An experienced seal supplier will:

• Ask detailed questions about the application environment
• Consider temperature, pressure, motion, and exposure duration
• Evaluate alternative materials or compounds
• Recommend testing or validation when necessary
• Help balance performance requirements with cost considerations

Engineering support helps ensure the seal material is compatible not just on paper - but in the real world.

Real-World Example: When Compatibility Is Overlooked

A common scenario involves replacing a seal with a “similar” material to reduce cost or improve availability. Without verifying chemical compatibility, the new seal may swell or harden within weeks, causing leaks and downtime.

In many cases, the cost of proper material selection upfront is far lower than the cost of failure later.

Final Thoughts: Compatibility Is Not Optional

Chemical compatibility is not a secondary consideration - it’s a critical factor in seal performance and reliability. Choosing the right seal material protects equipment, improves uptime, and reduces long-term operating costs.

If you’re unsure whether a seal material is compatible with your application, consult with a seal expert early in the design or replacement process. The right guidance can prevent costly failures and ensure your seals perform as intended - long after installation.