Personnel were focused on the AGES system test and results, not the compatibility of the test equipment. The manual valve was needed to successfully test the system, however the fact that this particular valve could not accommodate the full cylinder pressure was overlooked.

The following corrective actions will be implemented:

Evaluate the interfaces between engineering and operations systems and procedures to manage temporary modification work.
Develop and implement a procedure for engineering design of instrument systems.
Evaluate alarms/emergency response procedures for a relevant set of facility systems and revise, if necessary.
Evaluate the relevant facility building access training for appropriateness of the alarm response section and revise, if necessary.

This safety event suggests that temporary modifications, particularly those required for system testing, should be given the same level of attention and review as permanent modifications.