Seal configuration to reduce seal extrusion

A seal configuration, comprising:

• a body adapted to contain internal pressure having an opening with inwardly tapered peripheral sidewalls;
• a closure adapted to close the opening, the closure having an attachment portion larger than the opening and an axially projecting stopper portion adapted to fit closely within the opening, the stopper portion having an endless peripheral seal groove extending in spaced relation around the axis in which is positioned a peripheral seal adapted to sealingly engage the tapered peripheral sidewalls of the body in interference fit relation, thereby conforming to the tapered peripheral sidewalls;
• and
• a backing ring of pliable memory retaining material positioned between the peripheral seal groove and the attachment portion of the closure, the backing ring engaging the tapered peripheral sidewalls of the body in interference fit relation and conforming to the tapered peripheral sidewalls while being sufficiently stiff as to resist extrusion flow under pressure, such that when the peripheral seal deforms in response to an increase in internal pressure within the body and extrusion gaps begin to form between the attachment portion of the closure and the body, the peripheral seal is extruded against the backing ring which deforms to prevent the peripheral seal from entering the extrusion gaps.