DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
Accident Investigation Report
Surface Nonmetal Mine
Fatal Electrical Accident
Burro Chief Copper Company
Bayard, Grant County, New Mexico
Mine ID No. 29-00762
June 7, 1997
Omer H. Sauvageau
Mine Safety & Health Inspector
Daniel R. Lambert
Mine Safety & Health Inspector (Electrical)
Mine Safety and Health Administration
South Central District
1100 Commerce St., Suite 4C50
Dallas, Texas 75242-0499
Doyle D. Fink
Xavier R. McSherry, 28 year old electrical supervisor, died at about 1:10 a.m. on June 8, 1997, from injuries he received the previous day at about 6:45 a.m. while testing a 480 volt electrical circuit breaker. An arc phase fault occurred at the breaker resulting in a flash that injured McSherry and two other miners.
McSherry had a total of 4� years of mining experience, and was employed by Phelps Dodge Chino, Inc. at the open pit copper mine neighboring the SX/EW. He had been an electrical supervisor at the Chino Mines Company - Mine, an open pit mine, for about 7 weeks. He had received annual refresher training in accordance with Part 48 in January 1997.
Walter Gomez and Larry Filkins received injuries to the face, hands and arms from the flash. Both were supervisors at the Burro Chief Copper Co., SX/EW, a copper solvent extraction (SX)- electrowinning (EW) plant. Gomez had 16 years and Filkins 13 years of service at Burro Chief Copper Co.
The SX/EW, owned and operated by Burro Chief Copper Company, was located about 10 miles northeast of Bayard, Grant County, New Mexico. The principal operating official was William S. Brack, President. The plant employed forty two people and normally operated three, 8 hour shifts per day, seven days a week.
D.J. Hays left a message on the Albuquerque New Mexico Field Office answering machine at about 12:57 p.m., June 7, informing MSHA of the accident. He made no other attempt on June 7 to contact the agency.
Hays notified MSHA supervisor Thomas Loyd of the death at about 7:00 a.m. on June 8, 1997.
The Chino Mines Company - Mine, owned and operated by Phelps Dodge Chino, Inc., an open pit copper mine, was located about 2-1/2 miles northeast of Bayard, New Mexico adjacent to the SX/EW. The principal operating official was also William S. Brack, President. The mine employed 571 people and normally operated three, 8 hour shifts per day, seven days per week.
The last regular inspection of the SX/EW was completed on January 23, 1997. Another inspection was completed in conjunction with this investigation.
PHYSICAL FACTORS INVOLVED
Electrical power was supplied by Public Service Company of New Mexico at 115,000 volts Alternating Current (AC), three phase and was transformed to 13,800 volts AC at the main substation. The power was fed to the 750 KVA transformer and reduced to 480 volts AC, three phase, 900 full load amperes.
The equipment involved in this accident, a Westinghouse Seltronic circuit breaker, received the 480 volt power from the transformer. The circuit breaker was mounted in a Siemens motor control center (MCC) and provided protection for the tank house feeder breaker. The circuit breaker measured 16 inches high, 8 1/4 inches wide and 5 1/2 inches deep. It was improperly mounted in the MCC using 4 inch long 1/2 inch outside diameter threaded nuts. The nuts were tightened onto 5/16 by 1 3/4 inch bolts which entered through the back of the breaker. The nuts extended out of the recessed mounting holes by about 1 inch, and were within 1/4 inches of the energized terminals.
The circuit breaker was designed for mounting with .0250-20 x 1.5 inch Fillstar Head Steel Screws, Lockwashers and Flat Washers base mounting hardware. The reverse installation, using bolts inserted through the back of the breaker with extended nuts in the front, negated the recess design of the mounting holes and allowed contact between energized terminals and the extended nut.
The terminal cover, designed to insulate and prevent inadvertent contact with terminals, was not in place at the time of the accident. This determination was based on several factors. It was not at the scene of the accident, employees could not remember seeing it, and the company could not locate it during the investigation.
The transformer feeding the breaker was an RATE Corporation, three phase, 750 KA, connected 13,000 volt delta primary and 480 wye/277 volt secondary. Fuses in the F1 and F3 phases tested good. However, both fuses in the F2 phase tested open. The top fuse holder of the F2 phase showed signs of excessive heating and the outer fuse body was charred. The other fuse showed a darkened spot on the outside of the fuse case. The primary and secondary windings on the transformer did not indicate a ground fault or short circuit when tested.
The test meter used by McSherry was a Fluke Model 87 true RMS multi meter, serial #3564030. The meter was set to test for AC voltage and the display read Auto, AC, and MV. The test leads were still intact. A continuity test indicated that they were good. The outer insulation showed some heat damage but bare conductors were never exposed. The two fuses in the meter, a BBS 1 amp and a KTK 15 amp, both tested good. The metal probe of the red test lead was intact and was 3/4 inch long. The metal probe of the black test lead was melted so that only 3/16 inch remained.
DESCRIPTION OF THE ACCIDENT
At 6:15 a.m., prior to McSherry's (victim) arrival at work, a power outage occurred at the tank house of the SX/EW plant. William Shannon, plant operator, went to the tank house and asked employees if any of them could have caused a short circuit. None of them had. Shannon then called the electrical shop at the open pit to report the problem.
Shannon and C' shift supervisor Larry Filkins went to the MCC in which the circuit breakers controlling the power to the tank house were located. Shannon opened the feeder breaker and main breaker cabinet door. He noticed that the feeder breaker was tripped and reset it. He tested the main breaker to see if it was engaged and apparently tripped it out. He reset it twice but it wouldn't hold. Shannon left to prepare the SX/EW for shut down while Filkins continued trying to reset the main breaker. Eventually Filkins got the main breaker reset and called Shannon to tell him to put the SX/EW back on line.
About 6:30 a.m. on June 7, 1997, Xavier R. McSherry (victim) reported to work at the Chino Mines Company - Mine electric shop, a few miles from the SX/EW plant. Walter Gomez (injured), A' shift supervisor, reported to work at the SX/EW plant at the same time. When McSherry learned that a power outage had occurred, he proceeded to the SX/EW tank house MCC, checked and tripped the main breaker.
Virgil Giambernardi, electrician, went to the tankhouse to shutdown all 480 volt power and then joined McSherry, Shannon and Filkins at the MCC. McSherry opened the main breaker panel door and tested the breaker. After closing the panel door he tried to reset the breaker unsuccessfully. He then shut off all of the breakers in the MCC with the assistance of Giambernardi, who had returned from the tank house.
McSherry asked Filkins to reset the breaker but he was also unsuccessful. McSherry opened the panel door again to further test the breaker. A' shift supervisor Walter Gomez arrived at the MCC and Filkins began to explain the problems to him. Shannon was leaving the area.
McSherry squatted in front of the panel and began testing the breaker. When his multi tester probe contacted both a grounded extension nut and the energized terminal on the circuit breaker, an arc flash occurred in the main breaker box. McSherry's clothing caught fire, and Gomez and Filkins were burned by the flash.
Shannon, Gomez and Filkins extinguished McSherry's burning clothes. McSherry was placed in an ambulance alone and was transported to a medical center. Doctors diagnosed him with second degree burns over 75 per cent of his body and declared his condition as critical. McSherry was then airlifted to University of New Mexico Burn Center in Albuquerque, New Mexico. He died of his injuries the following day.
The accident was caused by the improper installation of the circuit breaker, in that the line terminal covers were missing and the base mounting hardware used was not comparable to that available from the circuit breaker manufacturer. This allowed the victim's test probe to simultaneously contact the grounded extension nut used for mounting the circuit breaker and an energized terminal. The severity of injuries was increased because the victim was not wearing protective clothing.
Citation Number 7850488
Issued to Burro Chief Copper Company on June 11, 1997 under the provisions of Section 103(j)/104(a) for violation of 30 CFR 50.10.
Citation Number 7850489
Issued to Burro Chief Copper Company on June 11, 1997 under the provisions of Section 103(j)/104(a) for violation of 30 CFR 50.12.
Citation Number 7859009
Issued to Burro Chief Copper Company on June 11, 1997 under the provisions of Section 104(a) for violation of 30 CFR 56.12002.
Citation Number 7859010
Issued to Burro Chief Copper Company on June 11, 1997, under the provisions of Section 104(a) for violation of 30 CFR 56.20011.
Citation Number 7859093
Issued to Burro Chief Copper Company on August 19, 1997, under the provisions of Section 104(a) for violation of 30 CFR 56.12017.
/s/ Omer H. Sauvageau
/s/ Daniel R. Lambert
Approved By: Doyle D. Fink, District Manager
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