Seal Material Selection Guidance

# Seal Material Selection Guidance

Selecting the correct seal compound begins with disciplined application review. Pressure, temperature profile, media composition, duty cycle, and compliance requirements define the boundaries for acceptable materials. This guide outlines a repeatable process so engineering teams can document assumptions and justify decisions to QA, procurement, and regulatory stakeholders.

## Four-Phase Selection Workflow

1. **Application Discovery** – Capture process parameters, mechanical tolerances, installation method, and maintenance frequency. Record transient events (pressure spikes, thermal cycling) that typically trigger seal failure.
2. **Material Screening** – Evaluate candidate elastomers/thermoplastics against chemical compatibility, thermal capability, and mechanical strength. Shortlist two or three options that meet minimum thresholds while balancing cost and lead time.
3. **Design Validation** – Calculate compression, stretch, and extrusion risk within the chosen hardware. Verify surface finish, gland radii, and assembly tooling. Introduce backup rings or alternative geometries if residual risk is high.
4. **Qualification & Documentation** – Run laboratory or field validation (ASTM D471 immersion, D573 aging, etc.). Package results with lot traceability, certificates, and dual-source contingencies.

Use the worksheets below to apply each phase to your application.

## Material Selection Methodology Overview

Seal performance depends on matching material characteristics to service conditions. Key evaluation factors include:

– **Temperature range** – defines baseline suitability and guides selection of curing system and additives.
– **Chemical compatibility** – drives long-term durability and volume stability.
– **Mechanical stresses** – determine hardness, modulus, and reinforcement needs.
– **Cost/availability** – balances performance with production economics and supply chain resilience.

## Structured Decision Flow

## Comparative Material Matrix

| Material | Temperature Range (°C) | Chemical Stability | Mechanical Strength | Wear Resistance | Cost Tier | Primary Applications |
| — | — | — | — | — | — | — |
| **NBR** | −40 to +120 | Good | Excellent | Good | Low | Hydraulics, automotive |
| **FKM** | −26 to +200 | Excellent | Good | Excellent | Medium-High | Aerospace, chemical |
| **HNBR** | −30 to +150 | Very Good | Excellent | Very Good | Medium | Oil & gas, powertrain |
| **EPDM** | −50 to +150 | Excellent (steam, water) | Good | Good | Low | HVAC, water treatment |
| **FFKM** | −15 to +327 | Outstanding | Excellent | Excellent | Premium | Semiconductor, chemical reactors |
| **PTFE Compounds** | −200 to +260 | Exceptional | Moderate (requires energiser) | Excellent | Medium-High | Aggressive chemicals, cryogenic |

## Engineering Checklist

– **Compression Set** – Target ≤25 % for static seals; adjust material/curing system if exceeded.
– **Volume Swell** – Keep within −10 % to +30 % after media exposure to maintain fit and preload.
– **Hardness Shift** – Limit post-test change to ±10 Shore A to retain sealing force.
– **Mechanical Retention** – Maintain ≥75 % tensile strength after aging/immersion testing.

## Qualification Toolkit

– Chemical immersion (ASTM D471 / ISO 1817)
– Compression set (ASTM D395 Method B)
– Thermal aging (ASTM D573)
– Dynamic exposure / fatigue testing (based on application)
– Regulatory compliance (FDA, USP VI, ATEX, oxygen compatibility, etc.)

## Documentation & Handoff

Prepare a standardised material selection dossier including:

– Application summary and operating envelope
– Material shortlist with test data
– Groove/compression calculations
– QA plan and inspection checkpoints
– Certificates and traceability documentation

Need help finalising material choice or preparing validation tests? Contact our engineering team via the CTA for a bilingual review package.