Elastomer Seals vs Metal Seals Differences: A Selection Guide

In fluid handling, the seal is the smallest component with the biggest responsibility. A single failure can shut down a refinery or compromise a vacuum chamber.

Engineers eventually face a critical choice: should you use a flexible polymer O-ring or a rigid metallic seal?

Understanding the Elastomer Seals vs Metal Seals Differences is about matching material physics to your environment. At ADYAA, we know that choosing the wrong one is a recipe for leakage.

What Are Elastomer Seals Used For?

Elastomer seals (O-rings, rubber gaskets) are the industry standard for general sealing. Made from polymers like NBR, Viton, or EPDM, they work via “elastic recovery”—pushing back against the flange surfaces to create a seal.

Advantages of Elastomer Seals

• Cost-Effective: Inexpensive to manufacture and replace.
• Forgiving: Seals well even on slightly rough or imperfect surfaces.
• Reusable: Can often be reused after disassembly in non-critical systems.
• Easy Install: Requires low bolt torque to seat effectively.

Limitations

• Temperature: Most fail above 250°C (melt) or below -40°C (brittle).
• Permeation: Gases can slowly diffuse through the rubber over time.

When Should You Use Metal Seals?

Metal seals are the “heavy-duty” option for extreme environments like nuclear reactors, jet engines, and ultra-high vacuum systems. They work by crushing into the flange face (plastic deformation) to block leakage paths.

Advantages of Metal Seals

• Extreme Temperatures: Functional from absolute zero (-273°C) to over 1000°C.
• High Pressure: Handles pressures exceeding 20,000 PSI (1300 bar).
• Zero Permeation: Solid metal prevents gas diffusion completely.
• Chemical Immunity: Compatible alloys (Inconel, Silver) resist aggressive corrosion.

Limitations

• High Cost: More expensive materials and machining.
• Surface Finish: Requires highly polished flanges to seal.
• Single Use: Deforms permanently and cannot be reused.

Key Differences Between Metal and Elastomer Seals

To select the right component, compare these three critical engineering factors.

1. Temperature Capability

This is the main differentiator. Elastomers have a “thermal cliff”—they fail immediately once their temperature rating is exceeded. Metal seals are unaffected by thermal aging, making them the only choice for steam turbines or cryogenics.

2. Required Flange Load

Elastomers are soft and easy to tighten. Metal seals require high bolt loads to “crush” the seal into the flange. This demands stronger bolts and heavier flanges to prevent warping.

3. Leakage Rates

For a hydraulic pump, a drop of oil is acceptable—elastomers work here. For toxic gas or semiconductors, even a single molecule escaping is a failure. Metal seals offer superior “helium leak rate” tightness.

Quick Comparison: Rubber vs Metal Seals

Which Seal Should You Choose?

Before you order, use this quick checklist to confirm your decision.

Select Elastomer Seals If:

• Budget is tight: You need a cost-effective solution for mass production.
• Temperatures are moderate: Your process stays between -40°C to 250°C.
• Surfaces are rough: Your flange finish is standard (32-63 Ra) or slightly pitted.
• Reusability is key: You need to open and close the joint frequently for maintenance.
• Low Torque: Your equipment cannot handle high bolt loads.

Select Metal Seals If:

• Extreme Heat or Cold: You are operating in cryogenics or near furnaces (>300°C).
• Ultra-High Pressure: System pressure exceeds 10,000 PSI (690 bar).
• Zero Leakage is Critical: You are handling toxic gas, radioactive fluid, or high vacuum.
• Chemical Attack: The fluid is too aggressive for any polymer to survive.
• Long-Term Reliability: You need a “fit and forget” solution that won’t degrade over decades.

Frequently Asked Questions

Can I replace an O-ring with a metal seal?

Usually, no. Metal seals require a shallower, wider groove and a much smoother surface finish than a standard O-ring gland.

Why use silver or gold plating on metal seals?

Soft platings act as a micro-sealant. They flow into microscopic scratches on the hard flange face to ensure a gas-tight seal.

Which seal is best for Hydrogen service?

Metal seals are superior. Hydrogen molecules are tiny and can pass through the molecular structure of rubber (permeation), whereas metal blocks them completely.

The Bottom Line

There is no “better” seal, only the correct one for the application.

If you are sealing water at room temperature, metal is overkill. If you are sealing superheated steam, rubber is a safety hazard. Analysing the Elastomer Seals vs Metal Seals Differences ensures safety and budget optimisation.

Need help specifying your seals?

At ADYAA, we supply high-performance sealing solutions for every pressure class.

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