Piping Safeguards
- Supply piping should reduce the number of fittings and connections to limit potential sources of leaks.
- Multiple layers of safety should be provided for critical safeguards such as overpressure protection and isolation. For example, overpressure protection might include a combination of redundant pressure switches, regulators, and relief valves.
- Operational controls should be provided to prevent the vehicle fuel tank from exceeding its density filling limit, and under no conditions should it exceed 125% of service pressure. Mechanical overpressure protection should be provided to prevent the vehicle tank from exceeding 140% of service pressure. Special care must be taken where multiple pressures are dispensed at the same facility.
- The open end of the vent pipe should be protected from weather by utilizing a horizontal discharge or a vertical discharge with a suitable means of weather protection. See Figure 1 below as one example. This figure is from CGA G-5.5, "Hydrogen Vent Systems", Compressed Gas Association, 2004.
- Vent piping should provide a means for periodic removal of condensate (e.g., spring-loaded valve and small section of drain).