Severity
Incident
Leak
Yes
Ignition
No

The sensing diaphragm of a pressure transducer (PT), as supplied on an outdoor hydrogen compressor, unexpectedly ruptured and released approximately 0.1 kilograms hydrogen to atmosphere from the compressor discharge line. At time of incident, personnel nearby were alerted by a loud 'pop' and dust disturbance. Simultaneously, the facility monitoring system detected loss of the PT signal and initiated equipment shutdown. Facility personnel then closed isolation hand valves to stop the leak, locked and tagged out the equipment, and restricted the area. The failed component, a cigar type PT rated to 20,000 psi, originally supplied and installed by the manufacturer as part of the compressor package, was removed and inspected. Inspection revealed severed wires, a separated wire housing, missing electronics and damaged electrical potting.  The PT was on a line protected by a pressure safety valve set to 15,400 psi. 

Facility investigators later discovered that the failed discharge PT was manufactured with a 17-4PH stainless steel diaphragm. This type of stainless steel, while an industry standard for high pressure resistance with other materials, is known in industry to be incompatible with hydrogen. The compressor manufacturer's supplied documentation generally claimed use of materials resistant to effects of H2 embrittlement at expected operating conditions, but did not identify the specific materials of internal components such as PT diaphragms. The facility operator's commissioning procedures included functional test of each PT but did not include review of individual compressor component specifications.  Subsequent communications between facility investigators and compressor representatives revealed that the compressor manufacturer did not intend to supply 17-4PH material in its compressor components; the diaphragm material was overlooked by the compressor manufacturer when sourcing the PT. The compressor was subsequently repaired with a replacement PT using Nitronic 50 material, and a compatible pressure switch hardwired to the facility 'STOP' signal was added.

Incident Date
Jan 15, 2019
Equipment
  • Motive Power Systems
  • Compressor
  • Pressure Relief Devices
  • Pressure Transducer
Contributing Factors
Characteristics
When Incident Discovered
Lessons Learned

Maintain an internal process for verifying component wetted material compatibility for intended use as part of the procurement process for hydrogen system equipment. 

Don’t rely solely on a manufacturer to provide appropriately rated materials and components. Verify H2 compatibility of components and their specifications as early in the design or procurement process as possible.

Manufacturer-provided literature (brochures, instruction manuals, bills of materials, etc.) may not always identify the specific materials for each component, so verification may require Internet research or contacting the manufacturer to obtain the necessary information or certification.