DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
REPORT OF INVESTIGATION
Surface Nonmetal Mine
(Crushed Limestone)
Fatal Powered Haulage Accident
April 24, 2002
1604 Quarry
Vulcan Construction Materials, L.P.
San Antonio, Bexar County, Texas
Mine I.D. No. 41-01241
Accident Investigators
Robert D. Seelke
Mine Safety and Health Inspector
Emilio Perales
Mine Safety and Health Inspector
Elsa A. Roman
Mine Safety and Health Specialist
Ronald Medina
Mechanical Engineer
Originating Office
Mine Safety and Health Administration
South Central District
1100 Commerce, Room 462; Dallas, Texas 75242-0499
Edward Lopez, District Manager
OVERVIEW
On April 24, 2002, Douglas C. Grieve, mechanic, age 22, was fatally injured when the Caterpillar 910 loader he was operating tipped on its side, ejecting him from the cab.
The accident occurred after the loader stopped and rolled backwards on a 16 percent grade. Loss of engine power decreased the ability of the operator to maintain control of the loader.
The failure to wear seat belts contributed to the severity of the injuries.
Grieve had a total of 5 months mining experience as a mechanic, all at this operation. He had received training in accordance with 30 CFR, Part 46.
1604 Quarry, a crushed limestone operation, owned and operated by Vulcan Construction Materials, L.P., was located in San Antonio, Bexar County, Texas. The principal operating official was Mitchell D. Page, Sr., plant manager, southwest division. The mine normally operated two, 10-hour shifts, Monday through Friday, and two eight-hour shifts on Saturday and Sunday. Total employment was 49 persons.
Limestone was drilled, blasted, loaded into trucks and hauled to one of two plants located on site. The limestone was crushed, washed, screened, sized and stockpiled. The finished product was used in the manufacturing of asphalt and for use in the construction industry.
The last regular inspection at this operation was completed on March 28, 2002. A regular inspection was conducted following the investigation.
On the day of the accident, Douglas C. Grieve (victim) reported to work at 6:00 a.m., his normal starting time. As a mechanic assigned to work at the shop, Grieve began his shift by checking the inventory on the fuel tanks, then cleaned around the shop arranging spare parts. At about 2:45 p.m., Keuang Lovan, welder, was operating the 910 Caterpillar loader to move steel from the shop to the batch plant when the park brake began to smoke. Robert Hearn, shop leadman, assigned Grieve to the repairs and discussed the procedures for adjusting the park brake with him. Grieve worked on the park brake until about 3:30 p.m., then drove the loader from the shop to test the park brake on an incline. Grieve was last seen by Hearn as he was driving towards the ramp.
At about 3:37 p.m., Jose Hernandez, asphalt plant operator, was driving by the waste asphalt stockpile when he noticed the 910 loader overturned at the bottom of the inclined road between the asphalt plant and the maintenance shop. After notifying the shop, he observed Grieve lying beside the machine and immediately called for help. Hernandez went to where Grieve was and began CPR. Emergency personnel arrived and Grieve was airlifted to University Hospital where he died at 4:30 p.m. Death was attributed to blunt force trauma to his chest and abdomen.
MSHA was notified at 3:50 p.m., on the day of the accident by a telephone call from Mitchell Page, plant manager, to Ralph Rodriguez, supervisory mine safety and health inspector. An investigation was started the same day. An order was issued under the provisions of Section 103(k) of the Mine Act to ensure the safety of miners. MSHA's accident investigators traveled to the mine; made a physical inspection of the accident scene; interviewed employees; and reviewed conditions, training and work procedures relative to the accident. The investigation was conducted with the assistance of mine management and mine employees.
The accident occurred on an asphalt-paved road located between the maintenance shop and the asphalt plant. The road was approximately 28 feet wide and 196 feet in length with an average grade of about 16 percent.
The front-end loader involved in the accident was a Caterpillar Model 910, serial number 80U996, manufactured in 1973, and weighed approximately 14,210 pounds. The loader was equipped with a quick detach device on the boom to change from a loader bucket to forks.
During operational testing, the engine stalled a number of times when the throttle pedal was released. The air cleaner and fuel filters were visually examined and did not appear to be sufficiently dirty to cause flow restriction. During the post accident interviews, employees that had operated this loader prior to the accident stated the engine had a tendency to stall when the throttle pedal was released.
The loader was provided with hydraulically actuated, caliper-disc brakes on the front axle only. One service brake caliper was installed at each wheel. The right front wheel was correctly equipped with a four piston brake caliper designed for machines with a two wheel brake system. The left front wheel was incorrectly equipped with a two-piston brake caliper designed for machines with the four-wheel braking system option. The incorrect caliper reduced the total braking capacity of the machine by about 25 percent. The front left rotor was 0.41 inches thick whereas the minimum permissible rotor thickness was 0.45 inches as referenced in the operations manual.
The service brake could be applied using either of two pedals. The brake/neutralizer pedal on the left side of the steering column applied the service brakes and neutralized the transmission. The brake pedal on the right side of the steering column applied the brake without neutralizing the transmission. The brake/neutralizer pedal was mechanically connected to a transmission neutralizer valve.
A power cylinder/master cylinder provided the pressure to the calipers. The power cylinder was bolted directly to the master cylinder and provided power assisted braking. The mechanical force physically applied by the operator to the pedal increased the force on the master cylinder piston. The combined force was designed to increase the pressure in the calipers to 1,400 psig or more according to the service manual.
The brake fluid in the master cylinder and the brake lines were separate from the hydraulic system of the power cylinder by design. The service brake was designed to operate without the engine running, but more force was required from the operator on the brake pedal since power assist was not available with the engine off.
The pressure measured at the calipers was approximately equal regardless of which pedal was pushed. When the engine was running, the caliper pressure was 1,500 psig. This met the pressure specifications of 1,400 psig or more in the service manual. When the engine was stopped (no power assist) the caliper pressure measured 800 psig. In both cases it was necessary for the operator to forcefully apply the brake pedal to achieve these pressures.
The service brake was tested with the machine systems at operating temperature. The forks were empty and the machine was tested in both directions of travel. The service brake stopped and held the machine on a 15 percent grade both when the engine was running and when the engine was off.
The park brake system consisted of a manually applied drum brake on the driveline. The park brake mechanism worked as designed. The inside surface of the brake drum was coated with a grease dirt mixture. The parking brake was tested, and when fully applied, the parking brake failed to hold the empty machine on an 8 percent grade.
The loader was found laying on its right side with the starter key in the "on" position. The transmission was in second gear forward and the park brake was in the released or "off" position. The brake, brake/neutralizer and throttle pedals and linkage moved freely. The transmission fill cap was found laying on the ground adjacent to the loader. The right rear tire was flat. After the machine was righted, the tire was evaluated and no damage was found. The tire and rim were cleaned, and the tire was inflated. It was concluded the tire deflated as a result of the accident.
During operational test of the machine, transmission fluid overflowed from the dipstick on one occasion. The overflow stopped when the transmission fill cap was loosened. The overflow occurred despite the transmission fluid level being in the normal operating range. According to information provided by Caterpillar, a vented cap was specified for the transmission installed in the 910-wheel loader. Discussions with previous operators showed this to have been an ongoing condition; and they would reach down to the cab floor from the operator's position to unscrew the cap to relieve pressure. The cap installed on the machine was not vented to relieve pressure buildup.
The seat was mounted to a hinged battery access cowling that would swing toward the rear of the loader when opened. The seat was found in the full forward position. There was no visible damage to the seat belt. The belt was 3 inches wide and would latch and unlatch when tested. There was no physical evidence that the seat belt had been worn at the time of the accident.
The power assisted steering system was inspected and no defects were found. However, when the engine was off the ability to steer the loader was lost.
With the seat in the full forward position, the distance from the intersection of the seat back and the seat bottom surfaces to the service brake pedal was 36 inches. While the machine was shut down an MSHA investigator, who was 5 feet 2 inches tall, sat in the operator's seat and applied the service brake. When applied, the distance to the brake pedal increased to 38 inches indicating a pedal movement of 2 inches. To apply the brake it was necessary for the operator to extend the ankle and reach the pedal with the ball of the foot. Operators able to reach the pedal without flexing the ankle were able to push the pedal 2 � inches. This additional pedal movement resulted in higher brake pressure at the caliper and more grade holding capability. If Grieve had to extend his ankle to reach the pedal, the available force on the brake pedal may have been reduced.
The root cause of the accident was the failure to identify and correct the engine stalling condition through prompt and corrective maintenance procedures. The accident occurred because once the engine stalled, the mechanic could not maintain control of the equipment.
Failure to wear the provided seat belt contributed to the severity of the injuries.
Note: Some or all of these violations were affected based on a decision by the Federal Mine Safety and Health Review Commision. See More InformationOrder No. 6220615 was issued on April 24, 2002, under the provisions of Section 103(k) of the Mine Act:
A fatal accident occurred at this operation on April 24, 2002, when a mechanic was ejected from the Caterpillar 910 loader when it rolled over. The accident occurred on the road between the asphalt plant and the mechanic shop. This order is issued to assure the safety of all persons at this operation. It prohibits any activity in the affected area until MSHA determines that it is safe to resume normal mining operations in the area. The mine operator shall obtain prior approval from an authorized representative for all actions to recover and/or restore operations to the affected area.This order was terminated on August 22, 2002.
The conditions that contributed to the accident have been addressed.
Citation No. 6220429 was issued on August 12, 2002, under the provisions of Section 104(a) of the Mine Act for violation of 30 CFR 56.14130(g):
A fatal accident occurred at this mine on April 24, 2002 while the mechanic was performing a park brake test on the Caterpillar 910 wheeled loader, on a 16 percent grade. The loader tipped on its side ejecting the operator who was not wearing the provided seatbelt.This citation was terminated on September 3, 2002.
All equipment operators have been re-instructed in the mandatory use of seat belts.
Citation No. 6220436 was issued on August 12,2002, 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 mine, on April 24, 2002, when a mechanic lost control of the Caterpillar 910 loader he was operating while conducting a park brake test on a 16 percent grade. The engine stalled during the test resulting in a loss of hydraulic support power to the steering and brake systems. Once the steering and braking capacities were diminished, the mechanic no longer had the ability to control the equipment. The engine had a history of stalling which presented a hazard to persons. This defect had not been corrected in a timely manner.This citation was terminated on September 3, 2002.
The company submitted a letter on September 3, 2002, stating the 910 Caterpillar wheel loader would be removed from mine property.
Related Fatal Alert Bulletin:
FAB02M14
APPENDIX A
Vulcan Construction Materials, LP
James Thomas Hill ......... vice president- texas southwest divisionMine Safety and Health Administration
Frederick W. Orth ......... operations manager, south texas
Mitchell D. Page Sr. ......... plant manager southwest division
Richard L. Seago ......... manager, safety administration corporate
Darlene M. Braymanager ......... safety and health, southwest division
Robert A. Hearn ......... shop leadman
Robert D. Seelke ......... mine safety and health inspector
Emilio Perales ......... mine safety and health inspector
Ronald Medina ......... mechanical engineer
Elsa M. Roman ......... mine safety and health specialist
Vulcan Construction Materials, LP
Rodrigo C. Rangel ......... groundman
Manual M. Herrarra ......... plant operator
Jesus L. Parral ......... plant operator
Aaron Villareal ......... plant operator
Richard H. Baur ......... welder
Frank F. Bluemel ......... foreman
Jose R. Hernandez ......... plant operator
Keuang Lovan ......... welder
Robert A. Hearn ......... shop leadman