Valve malfunctions and valve leaks are the largest contributors to hydrogen incidents at NASA, accounting for 20% of the incidents. Leaking connections are the second largest, accounting for 16% of the incidents.
Inspection activities for hydrogen systems include
- leak testing
- checking for continuous flow from vent systems
- operational checks for valves, especially relief and check valves
- functional checks and calibration of instruments
Leak testing using soap bubble solution or a hand-held hydrogen detector should be performed on a regular basis, and every time joints are re-assembled. Connections should be regularly inspected for any sign of corrosion, erosion, cracking, bulging, blistering, or other deterioration.
Maintenance and recalibration of leak and flame detectors should be performed periodically, typically every 3-6 months or as recommended by the manufacturer.
There should be planned inspections for all equipment (see Note below). Maintenance staff should review the inspection list and make sure the entire inspection plan is completed and documented as scheduled.
Just as with any maintenance procedure, the inspection procedure should be planned using a Job Safety Analysis and documented accordingly to ensure that employees use a consistent process and that risks of hazards are minimized (note that inspection may mean being in close proximity to operating equipment).
Any system deficiencies found during an inspection should be identified (tracked and stewarded), corrected, and reviewed by a trained second party before future tests are conducted.
Chronic maintenance issues (repeated problems with the same component) may be the result of design flaws that should be corrected.
Note: As used in this section, “equipment” is an all-inclusive term that includes piping, instruments, and controls as well as those hydrogen system components commonly known as equipment.