Short answer
Seal hardness and seal material are not the same information. Different hardnesses and formulations within the same elastomer family can behave differently; the correct seal is selected together with the connection geometry and the manufacturer's compound designation.
Technical explanation
Resistance to the contacting chemical, temperature and the mechanical sealing requirement are considered together. Under conditions such as CIP/SIP, the performance of compounds within the same elastomer family can vary. A hardness value alone does not guarantee chemical compatibility or sealing at all pressures. The size of a used seal may differ from its original size due to swelling or permanent deformation. Color is not a definitive identification of material and hardness either.
Topic-specific checkpoints
| Item | Description |
|---|---|
| Material | Elastomer family and compound |
| Hardness | Separate mechanical property |
| Geometry | Seal and groove dimensions on the drawing |
| Exposure | Process and cleaning conditions |
How is it assessed in practice?
In the spare seal record, keep the product code, material/compound, size and hardness designation (if any) separately. Before placing a new order by measuring a seal removed from the field with a caliper alone, refer to the connection drawing. When the cleaning chemical changes, check the seal's suitability as well. Do not make selecting a harder seal a general method for eliminating a leak problem; damage to the groove and mating face should also be examined. The assembly and lubrication conditions recommended by the manufacturer must be maintained.
Original editorial recommendation; not a clause of a standard.
Frequently asked questions
Can two seals of the same color replace each other?
Color is not an adequate identifier. The product code, material, size and required mechanical properties must be verified.
Source coverage
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S020
Chemical Resistance Chart Gates · accessed 2026-10-19 PDF page 2 / printed page 1: Chemical Resistance Table, notes
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S037
CIP and SIP Trelleborg · accessed 2026-10-19 Aggressive chemicals; CIP facts; research results