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UNITED STATES
DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION

Surface Nonmetal Mine
(Cement)

Fatal Powered Haulage Accident

Date of Accident: March 30, 2002
Date of Death: April 5, 2002

Midlothian Quarry and Plant
Texas Industries
Midlothian, Ellis County, Texas
41-00071

Accident Investigators

Michael C. Sanders
Mine Safety and Health Inspector

Michael A. Hockenberry
Fire Protection Engineer

Judy M. Tate
Mine Safety and Health Specialist

Originating Office
Mine Safety and Health Administration
South Central District
1100 Commerce Street
Room 462
Dallas, Texas.75242
Edward E. Lopez
South Central District Manager

OVERVIEW

On March 30, 2002 Juan R. Hernandez, Sr., process assistant, age 67, was critically injured when he sustained thermal burns over 47 percent of his body. He died of those injuries on April 5, 2002. A rapid steam eruption occurred when hot clinker fell from a drag conveyor into standing water.

The accident occurred because procedures that required accumulated water to be removed from the tunnel floor prior to opening the inspection door of the enclosed drag conveyor were not followed.

Hernandez had 29 years mining experience, all at this operation. He had received training in accordance with 30 CFR, Part 46.

GENERAL INFORMATION


Midlothian Quarry and Plant, a surface quarry and cement plant, owned and operated by Texas Industries, was located in Midlothian, Ellis county, Texas. The principal operating official was James R. Owens, plant manager. The quarry and plant were operated three, eight-hour shifts, seven days a week. Total employment was 275 persons.

Limestone and shale were mined from a single bench quarry by ripping with a dozer and loading with a front-end loader on to haulage trucks for transport to the primary crusher. Crushed material was conveyed to the plant by conveyor for processing into Portland cement. The finish product was sold for use in the construction industry.

The last regular inspection of this operation was completed on May 9, 2001.

DESCRIPTION OF THE ACCIDENT

On March 29, 2002, Juan R. Hernandez, Sr. (victim) reported for work at 8:00 p.m., four hours prior to his normal start time, for voluntary overtime. Hernandez was briefed by the process assistant and started his normal duties.

On March 30, 2002, at about 4:00 a.m., Hernandez and Sylvester Gonzales, Jr., welder/repairman, were called to the 740 tunnel by Jerold Johnson, process supervisor, to unplug clinker material in the 740 enclosed drag chain conveyor. Johnson entered the tunnel by the access ladder at the west end where he noticed a pressure pad sensor outside of the housing. Johnson re-installed the device and several attempts were made to re-start the conveyor with no success.

By this time, Gonzales, Hernandez and Christobal Garcia, kiln oiler, arrived. They began opening top doors on the conveyor housing in an attempt to locate the plugged material. Hernandez opened a top door near the feed chute end of the conveyor and told Johnson, Gonzales and Garcia that he may have found the problem. They decided to open the clean out door from the side of the conveyor enclosure and allow the hot clinker to spill out onto the tunnel floor. Due to an accumulation of water on the floor in this area, a plan of rapid exit was discussed to escape the inevitable steam. Johnson, Garcia and Gonzales would travel up the tunnel incline to the head pulley and Hernandez would travel up a fixed ladder in the pit area by the chute end of the conveyor.

Gonzales and Hernandez removed the door retaining bars and while Gonzales held the door in place, Hernandez started up the ladder. When Hernandez was 2 or 3 rungs up the ladder, Gonzales allowed the door to open. Hot clinker spilled into the standing water producing a rapid steam eruption. Johnson, Garcia and Gonzales were about half way up the tunnel when Hernandez called for help. After several failed attempts, Gonzales managed to reach Hernandez, who was in the corner at the end of the tunnel, and assisted him out of the tunnel. Company emergency medical personal arrived shortly and Hernandez was stabilized. He was transported to Parkland hospital burn unit where he remained in critical condition until his death on April 5, 2002

INVESTIGATION OF THE ACCIDENT

MSHA was notified of the accident at 9:38 p.m., on March 30, 2002, by a phone call from Larry Ratliff, safety manager, to the MSHA National Office. On April 5, 2002, the MSHA South Central district office was notified that Hernandez had died from his injuries. An investigation was started the same day. MSHA's accident investigation team traveled to the mine, made a physical inspection of the accident scene, interviewed employees, reviewed training records and reviewed conditions and work procedures relevant to the accident. MSHA conducted the investigation with the assistance of mine management and miners.

DISCUSSION

  • The accident occurred in the 740 chain conveyor tunnel below the No.4 Kiln. The tunnel was approximately eight feet in width by eight feet in height and about 150 feet in length. The enclosed chain conveyor involved in the accident transported clinker for approximately 135 feet. This chain conveyor was driven by a motor rated at 15 horsepower and was manufactured by General Electric.


  • The enclosed chain conveyor was situated along the centerline of the tunnel. The enclosure for the chain conveyor was approximately 22 inches in width by 31 inches in height. Access doors, located along the top of the enclosure, were used for repairs or visual inspection of the chain and clinker.


  • At the lower end of the 740 chain conveyor tunnel, clinker fed into the conveyor through a chute. The chute measured 22 inches and was equipped with a pressure pad sensor located on the west end side panel. The sensor was approximately six inches from the top of the chain conveyor enclosure. The sensor had a visual alarm that was monitored in the control room and was interlocked with the chain conveyor motors on the 740 tunnel chain conveyor and the chain conveyor from the clinker cooler, which fed the 740 chain conveyor.


  • In the event the pressure sensor tripped as a result of a plugged chute, the control room operator would immediately slow down the kiln rotations and the amount of raw feed on the inlet side of the kiln. The operator would continue to run the kiln for approximately 20 minutes before it reached its maximum capacity and had to be shut down.


    • It was routine for the chute to plug several times per week. When this occurred, it was the practice to remove a small access door located on the side of the conveyor enclosure directly under the inlet chute. This door measured 10 inches wide by 12 inches in height and was 55 inches above the floor.

  • There were two means of egress from the 740 tunnel. Both exits had vertical ladders, one located at the west end of the tunnel near the drive motor, and the other located on the east end of the tunnel near the inlet chute to the enclosed conveyor. The east end ladder, which Hernandez had attempted to ascend, had a vertical height of 13 feet.


  • The amount of water that accumulated on the floor covered an area of approximately 72 square feet and was reported to be from 2 to 8 inches in depth. This would be an approximate volume of between 45 and 180 gallons of water. When the door was removed the hot clinker exited the enclosure and fell into the water resulting in a rapid generation of steam in the lower end of the 740 tunnel. The victim had been standing on the east end ladder when the steam was generated. The other three workers that were present at the time of the accident exited the immediate area towards the west end ladder.


  • The clinker exits the kiln at around 2200 degrees Fahrenheit before entering the clinker cooler. Temperature readings of the clinker in the enclosed conveyor system at the site of the accident averaged 275 degrees Fahrenheit with some hot clinker reaching temperatures upward of 550 degrees Fahrenheit. Clinker at temperatures greater than 212 degrees Fahrenheit would generate 212 degree steam when contacting water. The exact amount of hot clinker that exited the door opening was unknown. There were reports that ranged from one to two wheelbarrows full.


  • The location of the transfer point, in the 740 tunnel where the accident occurred was at the lowest elevation in the tunnel. This area measured 8 feet wide by 8 feet high by 9 feet in length. This Apit@ had a total volume of 576 cubic feet. The expansion ratio of water to steam is approximately 1700:1; therefore the amount of available water needed to fill this Apit@ with steam would be approximately 2.5 gallons. The lowest amount of water that was reported in the Apit@ was 45 gallons, which is 18 times the minimum amount of water needed to fill the pit with steam.


    • CONCLUSION

    The root cause of the accident was the failure to install an effective means to promptly remove the accumulated water from the 740 tunnel. The accident occurred because the hazards associated with the task had not been properly evaluated prior to opening the access door, allowing hot clinker to spill into the standing water causing a rapid steam eruption.

    ENFORCEMENT ACTION

    Citation No. 6217849 was issued on April 5, 2002, under provisions of Section 104(a) of the Mine Act for violation of 30 CFR 56.20003b:

    A serious accident occurred on March 30, 2002, when an employee sustained thermal burns over 47 percent of his body. He later died of those injuries on April 5, 2002. A rapid steam eruption occurred when hot clinker was dumped from the 740 drag conveyor enclosure into six inches of water that had accumulated on the floor.

    This citation was terminated on 6/21/2002, when a sump pump was permanently installed in the tail pulley area of the 740 Drag Conveyor. Additional training had been given to employees assigned to work in the tunnels regarding steam hazards.

    Related Fatal Alert Bulletin:
    Fatal Alert Bulletin Icon FAB02M12



    APPENDIX A

    Texas Industries
    James R. Owens .............. plant manager
    Brian L. Bottelberghe .............. production manager
    Gerold L. Kuykendall .............. assistant plant manager
    Daniel W. Paine .............. safety coordinator
    Larry L. Ratliff .............. safety manager
    Brian L. Bottelberghe .............. production manager
    Michael C. Stripe .............. corporate safety & health
    Todd A. Camp .............. quality control supervisor
    Gregory S. Boston .............. maintenance supervisor
    Marla S. Christenson .............. administrative supervisor
    Ronda L. Barker .............. senior administrator assistant
    Mickey B. Blankship .............. pyro process supervisor
    Mine Safety and Health Administration
    Michael C. Sanders .............. mine safety and health inspector
    Michael A Hockenberry .............. fire protection engineer
    Judy M. Tate .............. mine safety and health specialist

    APPENDIX B

    Persons Interviewed

    Texas Industries
    Sylvester R. Gonzales .............. welder, repairman
    Gerrell L. Leonard .............. welder, repairman
    Michael P. Dickerson .............. kiln oiler
    Christobal Garcia .............. kiln oiler
    Rickey R. Poff .............. process supervisor
    John M. McCutchem .............. process supervisor
    Jerald R. Johnson .............. process supervisor
    Kelley J. Pitner .............. process supervisor
    David E. McGraw .............. process supervisor
    Silas W. Simmoms .............. process supervisor
    Michael L. Conner .............. process assistance
    Douglas R. Jeffers .............. protective service
    Vernon J. Miller .............. protective service