Release from a burst disc

A burst disc opened prematurely at a research facility, during a hydrogen tube trailer filling operation.
The disc failed at 87% (5200 psig, approximately 36 MPa) of the final pressure (6000 psig, approximately 41 MPa). A vent line attached to the burst disc was not sufficiently anchored and bent outward violently from the thrust of the release over an approximate 102 mm (4-inch) moment arm, causing considerable damage to the adjacent vent system components.
To continue the operation of filling of the trailer, the damaged portion of the tube bank, consisting of 6 tubes, was isolated by means of valves, and the operation was resumed with the unaffected portion of the tube bank which had another 18 tubes, until a second burst disc failed.
The incident investigation revealed that the burs discs were made of pure nickel and affected by extensive hydrogen embrittlement.

The INITIATING CAUSE was the premature failure of a burst disc.
The ROOT CAUSE is related to the management shortcoming, allowing the re-installation of a non-hydrogen system for hydrogen purposes, without considering new related risks and the needs for a careful re-assessment of the system for its new uses.
DETAILED CAUSE ANALYSIS
Metallurgical examination of the two failed burst discs indicated the occurrence of hydrogen embrittlement; they were found to be fabricated from pure nickel with evidence of extensive fracture. An inspection of all vent circuits found that each of the 24 discs in service was made from nickel, were affected by surface fractures which extended around the entire periphery of the rupture disc. Such defects are indicative of hydrogen embrittlement. An inspection of all vent circuits found that each of the 24 discs in service was made from nickel.
The storage bank had been employed before for the storage of helium. The pressure vessel documentation accompanying the system indicated that the burst discs were made of stainless steel and rated to 10,000 psig.
The overal damage was caused by the vent line which was not well fixed and moved with the hydrogen thrust.

burst disc

The storage bank had been employed before for the storage of helium. The pressure vessel documentation accompanying the system indicated that the burst discs were made of stainless steel and rated to 10,000 psig.

DESCRIPTION of the FACILITY
The storage bank consisted of 24 tubes. Each of the 24 tubes in the system is protected by a burst disc.

Considerable damage to the adjacent vent system components, due to the hydrogen ejection thrust and the vent pipe not correctly fixed. .

The burst discs were made of nickel, a material not recommended for hydrogen service in general, and for rupture discs in presence of hydrogen in particular (see for example standard ISO 15916).
This case highlights the importance of accurate physical inspection of all components, if a system designed for other uses has to be converted to hydrogen service. An inspection performed before putting in use the system as hydrogen storage could have identified that burst discs were made of the wrong material and they needed for their replacement. Caution should be exercised to insure that all hardware is adequate for its designed purpose, even when procured from a commercial source.
It is also important to keep record of any modification brought to a technical system, so that the technical documentation is up to date, and enable management of changes.

Relief of hydrogen gas should not lead to movement of the vent line sufficient to cause system damage. Corrective actions included increasing the line diameter and adding bracing between the lines and the system bulkhead to strengthen the components should other releases occur.