Progress: Addressed, Not Adequately
High pressure tubing and fittings will be required to fill and vent cylinders and to connect cylinders.
As pressure increases, making the connection of the tubing and fittings becomes more difficult. Connections are often made by plastically yielding portions of the tubing so that the fittings will not leak or fail to hold. As contained pressure increases, the tube walls thicken, making plastic deformation difficult and possibly inducing stress concentrations. This may compromise the integrity of the joint between the tubing and the fittings. If the joint fails, hydrogen can leak and ignite.
Industry is working on new methods of connecting tubing and fittings.
Industry and DOT should monitor field experience with high pressure tubing and fittings to ensure that safe, reliable components are being developed. As experience progresses, standards should be developed for the qualification of high pressure tubing and fittings.