Industrial seal selection guide: material, hardness, environment, size
The right seal selection directly determines the reliability of the system. Choosing the wrong material or hardness leads to leakage, premature ageing and downtime. In this guide we explain step by step how to select a seal by four main criteria — material, hardness, environment and size.
1. Material selection by working environment
Material selection is the most critical step, because the wrong material makes all other parameters irrelevant. Options suited to the environment:
- Outdoor, water, steam — EPDM, due to its excellent resistance to UV and ozone. The reasons are explained in the article UV and ozone resistance.
- Oil, fuel, greases — NBR (oil-resistant rubber).
- High temperature and aggressive chemicals — Viton (FKM).
- Very wide temperature range, food/medical — silicone.
To compare the materials side by side, see the article comparison of EPDM, NBR and silicone.
2. Hardness (Shore) selection
Hardness determines the balance between the seal's sealing capability and its resistance to deformation. A soft seal (e.g. Shore A 50–60) seats well on uneven surfaces; a hard seal (Shore A 70–80) retains its shape under high pressure. More about the scale in the article what is Shore hardness.
3. Working condition parameters
Temperature
Each material has its own temperature range. For example, EPDM works from approximately -40 °C to +120 °C, while Viton works at higher temperatures. Always take the maximum and minimum working temperature into account.
Pressure and movement
Static (fixed) sealing and dynamic (moving) applications require different hardness and profile. In a dynamic environment, friction and wear must also be taken into account.
4. Size and tolerance
If the wrong cross-section and diameter are chosen, even the best material will not seat tightly. The groove size, compression percentage and tolerances must be determined in accordance with the project. At this stage, the quality of vulcanisation also affects dimensional stability.
Short checklist for selection
- What is the working environment (oil, water, chemical, outdoor)?
- What is the minimum and maximum temperature?
- Is it a static or a dynamic application?
- Required hardness (Shore) and dimensional tolerance?
A correctly selected seal that has passed laboratory control means long-lasting sealing. To determine the seal material suited to your application together, look at our product range and get in touch with us.