The question of what is the optimum compression for an elastomer gasket, seal or O-ring is one that we are regularly asked. It is one that we also like to be asked as merely torquing any elastomer seal up as hard as can be is not the answer (this will just break down the cell structure and remove the properties for which it was chosen), and we always advise the use of compression stops, where possible, to limit torque.

Of course there is no one size fits all answer as the optimum interference is dependent upon the application, design and the material.

However we recommend working within the window of 25% min – 50% max, with the general sweet spot being 35% compression of the materials thickness. This applies to both solid and sponge elastomers.

These percentages are confirmed by SGS Baseefa Test House, and are also stated on our IECEx Hazardous Area report for our pre-approved silicone.

Compression set is a parameter that must be taken into account when choosing an elastomer, it’s durometer, and also the overall design of the application.