Project Hanford Lessons Learned
Project Hanford Lessons Learned |
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Title: Lockout Device Causes Breaker Failure
Date: April 1, 2002
Identifier: 2002-RL-HNF-0017
Lessons Learned Statement:
Some locking devices for circuit
breakers can damage the breaker with repeated use. Such damage may not be
obvious and can present hazards to workers who rely on those breakers for energy
isolation.
Discussion of Activities:
Facility stationary operating engineers
(SOE) at the 222-S Laboratory noticed that equipment powered from a three-pole
breaker was not operating even though the breaker appeared to be in the closed
(on) position. The SOE moved the breaker handle to the open (off) position and
then back to the closed position. While doing so, he noticed that the breaker
tie bar linkage between the three poles was loose. He did not feel that the
breaker was operating correctly but the breaker did close and the equipment was
restored to operation. A work request was generated to replace the breaker.
Analysis:
While replacing the breaker, workers discovered that the
center pole operating handle had been broken off from repeated or excessive
tightening of locking devices. The setscrew in the locking device apparently
crushed the hollow part of the breaker operating lever between the arrows in
figure 1 below. Note the damage to the operating tie bar as well.
They also noted that when the breaker was placed in the open position, the center pole remained in the closed position. That condition would place workers relying on the breaker for isolation of equipment at risk for electrical shock.
Numerous after market locking devices for circuit breakers are in use on the Hanford site. Until recently, none have been suitable for multi-pole branch circuit breakers that use a factory installed tie-bar. A PanduitÔ PSL-CB lockout device attached with a set screw has historically been used for locking out this type of breaker. It is shown installed on a breaker in figure 2. Repeated tightening of the set screw over many lockout evolutions apparently led to this failure.
Recommended actions:
To avoid future recurrences, the facility
electrical engineer researched available multi-pole lockout devices for circuit
breakers with a tie-bar. BRADY offers a Universal multi-pole lockout device
(item #5579) available through PRO-AM Safety, Inc. (724-776-1818). It will fit
circuit breakers manufactured by GE, ITE, Sylvania, Challenger, Westinghouse,
and General Switch Co. That device was obtained and tested at 222-S and found to
securely lock out the breaker without damaging the circuit breaker during
installation, use, or removal. Figure 3 shows the new thumbscrew operated device
installed on a new breaker.
Estimated Savings/Cost Avoidance: N/A
Priority Descriptor: YELLOW/Caution based on the potential injury to workers who might have relied on the damaged breaker for energy isolation.
Work / Function: Conduct of Operations - Lockout/Tagout; Maintenance - Electrical
Hanford-Defined Category: N/A
Hazard(s): Electrical
ISM Core Function(s): Feedback and Improvement
Originator: Fluor Hanford, Inc. Submitted by Gary Mickle
Contact: Project Hanford Lessons Learned Coordinator; (509) 373-7664; FAX 372-0008; e-mail: mailto:PHMC_Lessons_Learned@rl.gov?subject=2002-RL-HNF-0017
Authorized Derivative Classifier: Not required
Reviewing Official: John Bickford
Keywords: breaker, lockout device
References: http://www.pro-am.com/Catalog/Exec/product.asp?product_id=1291
PanduitÔ is a registered trademark of Panduit Corporation.
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