Premature Failure of Electro-mechanical Switches due to Inadequate Installation
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Type:  Lessons Learned

Publisher:  Brookhaven National Laboratory, Upton, NY

Date: 

Topics:  Operations, Maintenance, Work Management/Planning, Laboratory

During performance of a Search and Secure procedure for the BNL, NSLS-II storage ring, two adjacent door switches were found in the closed position when they should have been open. The door switches are used to monitor the door position and prevent staff entry to the accelerator enclosure during beam operations. During operations, the doors to the enclosure remain closed and are locked with electrically actuated locks. By the switches remaining in the closed position, the monitoring system "thinks" the door is closed when in fact, it could be open and access could be gained to the accelerator enclosure.

Several weaknesses in the installation of the switches were discovered and have since been corrected. Weaknesses included:

-Inconsistent installation.
-Varying strike angles.
-Interference between the switch body and the face of the door.

Lessons Learned: The Design Review process must ensure that all systems are reviewed by an appropriate team of engineers and/or technical staff. All installations should be reviewed by a mechanical engineer or other qualified person prior to placing them into operation to ensure installation meets manufacturer requirements.

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