Only the high restoring force of O-rings makes it possible for them to maintain their sealing effect over a long period of time and even be used several times.
Note: The restoring force of an O-ring material is specified in data sheets under the item “Compression set – (DVR)” listed.
In this test, an O-ring is clamped between two metal plates and exposed to a higher temperature for a longer period of time. The O-ring is then released again and tested to see to what extent the O-ring returns to its original shape.
If the ring were theoretically to return completely to its origin, the compression set would be 0%. If it is permanently severely deformed, the value could be around 50%, for example.
Tip: If an O-ring material has a compression set greater than 50%, it should not be used.