MINE SAFETY AND HEALTH ADMINISTRATION
Metal and Nonmetal Mine Safety and Health
Surface Nonmetal Mine
Fatal Electrical Accident
I.D. No. 2VP
Logandale, Clark County, Nevada
Royal Cement Company
Logandale, Clark County, Nevada
ID No. 26-01977
July 1, 1999
Supervisory Mine Safety and Health Inspector
Dennis D. Harsh
Supervisory Mine Safety and Health Inspector
Dean F. Skorski
Supervisory Electrical Engineer
Originating Office - Mine Safety and Health Administration
2060 Peabody Rd., Suite 610
Vacaville, CA 95687
James M. Salois, District Manager
On July 1, 1999, Robert A. Dotts, contractor electrician, age 60, was fatally injured while he was working on a 4160/480 volt electrical transformer. Power to the transformer had been tripped out at a load interrupter switch located two feet from the transformer. The contacts in the box opened but the contacts, flicker-knife blade switches, were stuck and did not open. With the switches still engaged, the 4160 volt cables to the transformer remained energized. Dotts contacted the energized end of one of the 4160 volt cables inside the transformer.
The accident occurred because the flicker-knife blade switches did not open when the load interrupter switch was tripped. Contributing to the accident was the failure to verify that the circuit being worked on was de-energized.
Dotts had a total of 31 years electrical experience, including approximately three years as a contractor and five to seven years prior experience at this mine as the plant electrician. He had not received training in accordance with 30 CFR Part 48.
Royal Cement Company, a surface quarry and cement plant, owned and operated by Royal Cement Company, was located at Logandale, Clark County, Nevada. The principal operating official was Aldo R. DiNardo, president. Limestone was drilled and blasted from a single bench and transported to a crusher by front-end loaders. Crushed material was transported by a conveyor belt to the mill for further sizing and processing into Portland cement. The finished product was stored in silos for bulk shipment. The plant was undergoing a major renovation project and had not operated continuously for several years. The mine normally operated one eight-hour shift, five days a week. Total employment during this construction phase was ten persons at the plant and eight independent contractor employees.
The last regular inspection of this operation was completed on February 11, 1998. Due to inactivity at the plant after this inspection, MSHA changed the status of the operation to permanently abandoned on July 20, 1998. The operator had not notified MSHA of commencement of construction activities at the mill several weeks prior to the accident. A citation was issued to the operator on a separate inspection for their failure to notify MSHA of these startup activities. Another inspection was conducted at the conclusion of this investigation.
DESCRIPTION OF ACCIDENT
On the day of the accident, Robert A. Dotts came to work at 6:30 a.m., approximately 30 minutes prior to his 7:00 a.m. normal starting time. The 4160/480 volt transformer serving the Crusher Finish Grinding Circuits was scheduled to be replaced with a new one which had arrived at the plant the day prior to the accident. The victim unlocked the transformer doors and began inspecting the high-voltage, plug-type connections, apparently unaware that they were energized. While examining the connections he contacted the energized plug tip and fell to the ground.
At approximately 6:55 a.m., Jerry Hollis and Jeffery Garner, welders, found Dotts lying motionless on the ground in front of the open transformer box. They pulled him away from the box, started first aid, and called local rescue crews for assistance. Other crew members arrived and Cardio Pulmonary Resuscitation was started. A Life Flight helicopter soon arrived and Dotts was transported to a local hospital where he was pronounced dead at 8:11 a.m. that morning. Death was attributed to electrocution.
INVESTIGATION OF THE ACCIDENT
MSHA was notified at 7:15 a.m., on the day of the accident by a telephone call from A. John Patrick, general manager, to William Wilson, assistant district manager, Western District office in Vacaville, California. An investigation was started the same day. An order was issued pursuant to Section 103(k) of the Mine Act to ensure the safety of miners. An MSHA team conducted a physical inspection of the accident site with the assistance of mine management, miners, and the State of Nevada's Department of Business and Industry. The miners did not request nor have representation during the investigation.
1. Electric power was delivered to the plant by the Overton, Nevada Power Company at 69,000 volts, phase-to-phase. The voltage was reduced to 4160 volts, alternating current, through a delta-wye connected transformer located within the plant's substation. The 4160 volt power was brought into a main electrical building through an underground feed. In the main building, the power was fed through several General Electric Blast circuit breakers to the various 4160/480 volt step-down transformers located throughout the plant.
2. Power coming from one of the circuit breakers, labeled crusher finish grinding transformer, fed into a Square D Power Zone load interrupter which fed into the 4160/480 volt transformer where the accident occurred.
3. The transformer was a step-down, oil-immersed, self-cooled, 4160/480 volt, 1000KVA transformer, serial number 7891759, manufactured by U.S. Transformer. A new transformer had been ordered to replace this one because it had been determined to be defective. The new transformer had arrived the day before the accident. It was slightly different in size and had crimp-type connectors while the old one had plug-type connectors.
4. The Power Zone model 162-52 load interrupter switch was manufactured by Square D Electrical Company and was rated at 4.16KV at 60,000 amperes. It was supplied with E50-1, 150E fuses. The mechanical switching mechanism contained main and arcing contacts, both of which were controlled by a single lever. The main contacts were ball and socket; the arcing contacts were flicker-knife blades. To operate the switch box, the lever was pulled downward through a 90 rotation. As it rotated, the main contacts disengage and the flicker-knife blade contacts "flick" out (disengage), interrupting the arc.
> During the investigation, the lever was rotated on and off several times but the blades would not disengage. The blades were cleaned with an aerosol electrical cleaner spray, tested again, and functioned properly. The blades had been defective for an undetermined amount of time prior to the accident. An accumulation of dust and dirt on the flicker-knife blade contacts prevented them from properly opening.
5. The load interrupter had a view window which allowed the person operating the switch to visually observe all the contacts within the box. The window was in good condition and had a slight layer of dust on the glass. A person could clearly see through the window and observe the position of the main and the flicker-knife blade contacts.
6. Several weeks prior to the accident, the victim had started preparations to replace the transformer with a new one. Dotts tripped the 4160 circuit breaker for the transformer, but did not lock or tag it out. He also opened the load interrupter switch feeding the transformer, locked it out, but did not tag it. Since the flicker-knife blade switches did not open, power could still flow given the right conditions, through the interrupter switch to the transformer. However, the 4160 circuit breaker feeding this switch was open and prevented the transformer from being energized. The victim then disconnected all cable leads in the transformer to prepare it for the new transformer's arrival several weeks in the future.
7. On June 23, 1999, one week prior to the accident, the Overton Power District No. 5 utility company conducted a planned power outage for the Logandale area, including all power to the cement plant. This outage caused all the 4160 volt circuit breakers at the plant to open. When electrical power was restored later that day, Dotts went through the plant and closed all the breakers including the one supplying power to the partially disassembled transformer which he had opened several weeks earlier. Once the breaker was closed and turned on, power was re-supplied to the disconnected high voltage cable leads in the transformer.
8. The plug-type end connecters on the high-voltage cables in the transformer had 2-inch porcelain tips. The porcelain tips prevented contact with the metal enclosure of the transformer even though the cables were energized.
The accident was caused by the defective flicker-knife blade switches not opening (tripping out) when the load interrupter switch was turned off . Contributing causes were the inadequate electrical lock out and tag out procedures and the failure to verify that the switch was opened through the provided view window.
Order No. 7966562 was issued on July 1, 1999, under provisions of Section 103(k) of the Mine Act.
An accident occurred at this operation on July 1, 1999, at approximately 0700 hours. A contract electrician was found unconscious near a 4160 to 480 transformer. The electrician was transported by helicopter to a local hospital where he was pronounced deceased at 0811 hours. This order is issued to assure the safety of persons at this operation until the mine or affected areas can be returned to normal operations as determined by an authorized representative of the secretary. The mine operator shall obtain approval from an authorized representative for all actions to recover persons, equipment, and/or return affected areas of the mine to normal. The order was verbally issued to John Patrick, general manager, on July 1, 1999, at 0715 hours and written and issued at 1820 hours on the same day.Royal Cement Company
Citation No. 4394965 was issued on October 18, 1999, under the provisions of Section 104(a) of the Mine Act for violation of 30 CFR 56.14100(b).
A fatal accident occurred at this mill on July 1, 1999, when a contractor electrician was electrocuted when he contacted an energized 4160 volt cable inside the crusher and finish grinding transformer. The flicker switches (knife blades) in the interrupter switch for the transformer were defective in that they did not open when the switch was tripped due to an accumulation of dust and dirt. With the switches stuck in the closed position, power was inadvertently supplied to the 4160 volt transformer.Dotts Electric
Citation No. 4394964 was written on October 18, 1999, under the provisions of Section 104(d)(1) of the Mine Act for violation of 30 CFR 56.12017.
A fatal electrical accident occurred on July 1, 1999, when a contractor electrician contacted an energized 4160 volt cable inside the crusher and finish grinding transformer. The main circuit breaker supplying power to the transformer was not locked out nor did it have suitable warning signs posted by the person who was working on it. The contractor engaged in aggravated conduct constituting more than ordinary negligence by not locking out the circuit breaker and posting suitable warning signs. This is an unwarrantable failure to comply with a mandatory standard.
Persons participating in the investigation:
Royal Cement Co.
A. John Patrick, general managerGrove Madsen Industries
James F. Lupton, electrician
John P. Feller, engineering & instrumentationState of Nevada, Department of Business & Industry
Kenneth E. Curtis, mine inspectorMine Safety and Health Administration
John R. Widows, supervisory mine safety and health inspectorAPPENDIX B
Dean F. Skorski, supervisory electrical engineer
Dennis D. Harsh, supervisory mine safety and health inspector
Darrell B. Turner, mine safety and health inspector
Royal Cement Co.
Aldo R. DiNardo, presidentMechanical Industries, Inc.
A. John Patrick, general manager
James F. Lupton, electrician
Jerry D. Hollis, welder
Jeffery S. Gardner, welder
Paul P. Doty, welder