Gap between two chambers with different pressures. To prevent leakage either the gap must be designed such that no pressure flow can be produced (gap seal) or special elements are used, the seals.
If it is necessary to seal against moving surfaces, the sealing gap requires larger tolerances.
As seen from the seal the size of the sealing gap must be matched to the seal material and the system pressure (Figure D 14). If this matching is not possible, a back ring must used to bridge the gap.
Figure D 14: Sealing gap for various seals and pressures