Abstract: A sealing system for an outlet of a plastic-lined cylinder has a plastic liner outlet extending into a bore of a boss. An insert is engageable with the bore, forming a primary seal between the insert and portion of the liner outlet. Further, a tapered compression surface of the insert engages a tapered bore portion of the liner outlet adjacent the primary seal for compressing the liner outlet and closing any annular assembly clearance at the primary seal for obviating opportunity for seal extrusion under pressure. An axial position in the boss, and dimensional integrity, of the liner outlet is maintained by engaging an annular distal end of the liner outlet in the bore by a stop. The stop can be integral with the boss. Reverse extrusion of the primary seal due to trapped gas and rapid decompression of the cylinder can be defeated by providing a leak path.

Abstract: A multilayer liner for a high-pressure gas cylinder is provided. The liner has an impact-modified polyamide (PA) layer in contact with the high-pressure gas. The impact-modified PA layer reduces travel of the high-pressure gas from the inside of the liner to the outside of the liner. Use of a gas barrier layer such as an EVOH layer in combination with the impact-modified PA layer results in improved permeation resistance not heretofore demonstrated in a Type 4 cylinder. Combination of the EVOH layer and the impact-modified PA layer results in an interior surface which is compatible with gas environment in the cylinder, ductility at high pressures, a range of temperatures, and can survive cryogenic conditions.