O-Rings & X-Rings
During operation, the O-ring or X-ring is seated in a specially shaped groove (gland) at the interface between two rigid components. When the components are forced closer together, the seal is compressed against the walls of the gland and creates a plug. If a pressure differential occurs across the gland, then the seal is compressed against the low-pressure side of the gland. If the pressure difference is too great, then the seal will extrude into the narrow gap between the walls of the gland, and the seal will fail.