Lesson Learned Briefing


No.LL19-0005

TitleResearcher's Questioning Attitude Mitigates Hazard

EventOther Facility Event

Event Date01/29/2019

CategoryESH-Electrical - Electrical Equipment-Labs/Technical Spaces Use, Breakers

Summary
Lesson ID: 019-BNL-I-1369 (Source: User Submitted)

Originating Organization or Contracting Company: Brookhaven National Laboratory

Date: 1/29/2019

Contact: Wai-Lin Ng, (631) 344-7153

Classifier: N/A Reviewer: Chuck Black

Statement: A questioning attitude led to a system redesign by the Facility and Operations Directorate (FO) with input from Safety and Health Services Division (SHSD) staff. The system redesign will enable circuit breakers within a subpanel to be safely reset.

Discussion: Given the heightened awareness on Electrical Safety, a researcher consulted the local Environment, Safety and Health (ESH) representative to evaluate the proper training needed to reset a circuit breaker inside a subpanel that had tripped while powering a vacuum pump. The vacuum pump is part of the system associated with a Plasma-Enhanced Chemical Vapor Deposition (PECVD) tool used in the cleanroom. The ESH representative arranged a walkdown with an electrical safety field representative along with other staff, who are likely to operate the circuit breaker, to examine the subpanel in question.

At the walkdown, the researcher opened the subpanel's front cover to reveal the tripped circuit breaker. Upon opening the covers, exposed energized circuit parts were discovered. The panel door was immediately closed and tagged to control access to the breakers. There were no injuries. Further investigation and review of the equipment manual indicated that lock out and tag out (LOTO) was required to access the NEMA box to reset the breakers.

Analysis: The 3-phase process chamber roughing pump is connected to the house breaker panel via the Pump Control subpanel. The power cord from the pump motor is connected via twist-lock cord plug to the main contactor inside the subpanel. Just upstream of this contactor is a 15-Amp, 3-pole circuit breaker. The incoming power from the house is wired to the "LINE" side of this breaker.

When service work needs to be performed in the subpanel control box, LOTO must be applied according to the manufacturer's instructions and Laboratory LOTO procedures.

Recommended Actions: Engineering: The NEMA box will be padlocked per the manufacturer's Operator and Maintenance manual. The facility has initiated action with Electrical Safety Group and FO to redesign the system, so the subpanel breaker can be reset without LOTO. Additionally, the system will be re-evaluated and redesigned, as necessary, to adequately handle the in-rush current requirements of the vacuum pumps and other scientific equipment.

Training: Employees who may be operating circuit breakers will be trained to Qualified Electrical Worker Level 1 at a minimum, those applying LOTO shall be trained as LOTO Authorized Workers, with CPR and PPE requirements.

Procedures: Complex LOTO procedures were developed with the LOTO SME to safely shutdown and LOTO the electrical distribution system.

Extent of Condition: The circuit panel was modified, reviewed and approved when first installed, and had been in operation since 2007. The electrical circuit supplies one additional experimental tool. Other lab tools at the facility with similar configuration, with circuit breakers located in a subpanel that occasionally have to be switched during the normal course of operation, shall be evaluated for potential electrical hazards.

It is recommended that facilities with similar configurations evaluate the potential for electrical hazards. Additionally, and as a reminder, manufacturing manuals should always be reviewed to determine the proper system shutdown and LOTO application.


Lessons Learned are part of the ISM Core Function 5, Feedback and Improvement. Applicable Lessons Learned are to be considered during working planning activities and incorporated in work processes, prior to performing work.
 
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