The sealing gap is the distance between two surfaces that are sealed by means of an O-ring.
After an O-ring has been pressed, there is still a small gap between the two surfaces to be sealed. This gap is called the sealing gap.
The aim of a seal is to seal this sealing gap securely and for the long term so that no medium can make it from one side of the sealing gap to the other.
In principle, it is important that the sealing gap is kept as small as possible. This is because the O-ring can be pressed into the sealing gap and damaged, especially under pressure. This damage is called “extrusion” or “gap extrusion” and means nothing other than that parts of the O-ring are sheared off.
The O-ring may have been damaged to such an extent that it is leaking and needs to be replaced.