A hydrogen monitor leak detector (HMLD) was out of service because of a failed membrane. The HMLD heater circuit and the ion pump and its associated controller were de-energized and red-tagged to ensure the system remained shut down. The ion pump and controller were later found energized. The ion pump circuit is a low-power (120-V, 1 amp) circuit and the pump operates in the micro-amp range. There was no damage to equipment from this inadvertent energization. There was also no personnel safety hazard since the tag out was not for maintenance purposes and since the system was in its normal operating configuration.

The direct cause is listed as personnel error, inattention to detail. This category most closely describes the inadvertent actuation of the controller toggle switch. This incident reinforced the need for refresher training to remind personnel to pay attention to details while performing maintenance and when hanging red tags.

Operations personnel received refresher training on the installation of red tags. Emphasis was placed on not using toggle switches as the isolation device when red-tagging equipment. The objective is to prevent inadvertent actuation/operation of red-tagged equipment. Critical Systems Maintenance (CSM) will discuss this occurrence at a scheduled safety meeting. The importance of maintaining equipment status as required by installed red tags will be emphasized.

Incident Date
Mar 27, 1991
  • Safety Systems
  • Measurement / Sensing Device
Damage and Injuries
Probable Cause
When Incident Discovered
Lessons Learned

Follow-up investigation of this occurrence confirms that it was inadvertent. Attention to detail while performing any task is a must for all personnel. This is to insure the safety of both the individual performing the task and others that may become involved.