A single-stage diaphragm compressor failed during boosting of high-pressure hydrogen ground storage banks. The compressor sources hydrogen from a 44 MPa storage bank as suction and discharges it at a stop set point of 85 MPa. The compressor capacity is 0.71 m3/min (25 scfm).
The original notice of failure was through an inter-diaphragm pressure indication and alarm. There should not be any pressure build-up between the layers of the diaphragm. Upon opening, hydraulic oil was found, leading to the assumption that the hydraulic-side diaphragm was leaking. Although spare diaphragms and seals were available for on-site repair, difficulty was encountered in attempting to remove the compressor nut above the diaphragms. Similar difficulties were encountered when the unit was returned to the manufacturer.
A new compressor nut of a different material was manufactured, plated, assembled to the head and returned for re-installation and operation. However, upon commissioning, it was discovered that the unit was not developing hydraulic pressure. The root cause was determined to be a fractured plunger, likely damaged during earlier repair efforts. The plunger was re-manufactured.
Failure of a diaphragm is not infrequent, but the seizure of the main nut threads is very rare. The manufacturer claimed this had never occurred before with this type of unit. The broken plunger is likely the result of poor instructions/communications between the vendor and the user. The detail and quality of drawings provided by the vendor were poor given the level of investigation and repair needed for this occurrence. It is possible that the proprietary nature of some equipment information may have been a factor.