Patent ID: 8608014

Claim:
A cylindrical pressure vessel comprising an internal body defining an interior chamber of the pressure vessel, an external body enclosing the internal body and separate from the internal body in order to avoid a transfer of shear forces, first and second end caps closing respective adjacent axial ends of the internal and external bodies, wherein the first end cap is fixedly attached to the external body and has an overlap section intruding into the internal body, the overlap section being free to shift axially relative to the internal body when pressure in the pressure vessel causes axial expansion of the external body, a seal arranged in the overlap section of the first end cap that contacts the interior circumferential surface of the internal body, the seal being retained in the overlap section for movement with the overlap section when pressure in the pressure vessel causes axial expansion of the external body and axial outward movement of the overlap section relative to the internal body, and at least one recess in an interior surface of the internal body that encloses the overlap section of the first end cap, the recess being located on a side of the seal that faces away from the interior chamber of the pressure vessel so that upon axial expansion of the external body, axial movement of the overlap section relative to the internal body causes the seal to move past an inner axial end of the recess to define a leakage path for fluid contained within the interior chamber of the pressure vessel.