Designing an effective seal is important for many applications like environmental seals that need to keep out water in outdoor weather conditions that might see a variety of wetness and temperature conditions.
There are 3 key considerations for designing a good seal:
- Cross sectional “squeeze”
- Gland fill
- Material selection for seal and gland
Squeeze is defined as the amount of compression the gasket experiences. If there is no compression, the seal is not energized and liquid, air, or dust can flow right past the seal. On the other hand, a seal that is over-compressed can lead to failure of the seal – including protrusion, nibbling, taking a compression set or catastrophically failing. General guidelines: for a static application and a solid rubber, the seal should be compressed 20-25%. Whereas to achieve a good seal with a sponge or foam elastomer in a static application, compression should be 50-60%. Squeeze can be calculated by:
Gland fill is the measure of total seal volume in the gland when the seal is compressed. It is measured as a percentage of the total volume of the gland. Ideally, for a static application the gland fill should be 85-90% filled where as a dynamic application should be lower at an 80-85% fill. Gland fill can be calculated as follows:
There are many different materials to choose from when designing a seal. Silicone materials have some key properties that make it an excellent selection for seals, including:
- Excellent weathering and resistance to ozone attack
- Very good compression set properties
- Working temperature -60°C (-76°F) to 200°C (392°F)
- Maintains physical properties at high temperatures
Fluorosilicone has many of the advantages listed above, but is also highly resilient in extreme environments with potential exposure to fuel, solvents and other chemicals.
Another material consideration is the adhesive. Stockwell Elastomerics also offers many peel and stick adhesives with various material properties allowing a gasket to stick to many surfaces.
Seal Design Assistance and Request a Quote for Seals
To design, prototype, and produce a seal for a specific application, contact a Stockwell Elastomerics Application Engineer for custom guidance and to request a quote.