Brad Johnson, service technician, age 35, was critically injured at about 1:30
p.m., on February 17, 1999, when a tire exploded after heat had been applied to
the rim. He died on March 1, 1999. Johnson had 10 years experience as a service
technician, 5 years with this employer. He had not received training in
accordance with 30 CFR part 48.
MSHA was notified at 2:00 p.m. on the day of the accident by a telephone call
from the safety director for the mining company. An investigation was started
the same day.
The Waco Pit, a surface sand and gravel operation, owned and operated by Trinity
Industries, Inc., was located near Waco, McLennan County, Texas. The principal
official was Walter Poston, manager. The plant and pit were normally operated
one, 10?hour and one, 12?hour shift a day, five days a week. A total of 23
persons was employed.
Sand and gravel was extracted by dragline and hauled to the plant where it was
washed, sized and stockpiled. The finished products were sold for use in the
construction industry.
The victim was employed by RDO Equipment Company, an independent contractor in
Hewitt, McLennan County, Texas. The contractor was enlisted by the mine operator
to repair the brakes on a haulage unit. The principal operating official was
Bradley Campbell, general manager.
The last regular inspection at this operation was completed on September 9,
1998. Another inspection was conducted at the conclusion of this investigation.
The accident occurred in the main shop building at the plant. The equipment
involved was a 1975 Euclid B-30 tractor and bottom dump trailer rated at 60,000
pounds capacity. The trailer had been removed from service to repair the left
rear brakes.
The tire was a Firestone tubeless type Super Rock Grip WB size 29.5 X 25 with
28-ply rating. It weighed approximately 1500 pounds. The diameter was 67 inches
and tread width was 26 inches. The tire was mounted on a 25-inch diameter rim
secured with a five-piece lock-ring assembly. The tire and rim assembly was
secured to the wheel with 20 wheel clamps, tensioning washers and nuts. Normal
cold operating pressure was 60 PSI.
The oxygen/acetylene cutting torch used to heat the rim was mounted on a
two-wheel cart. The compressed gas cylinders had been secured to the cart with a
chain and provided with protective valve covers. The heating tip was a multiple
flame heating nozzle (rosebud).
Laboratory tests indicated that the application of heat caused the tire material
to produce combustible gases inside the tire. The heated rim and tire provided
an ignition source for the combustible gases, which resulted in the explosion.
The victim was using a fork lift truck to remove the tire. The fork lift was a
Hyster model H80C, rated at 8,000 pounds load capacity.
On the day of the accident, Brad Johnson (victim) reported to the mine shop at
9:00 a.m. and received his work assignment from Robert Farmer, purchasing agent
for Trinity Materials. Johnson was assigned to repair the brakes on the Euclid
B-30 trailer. Johnson and Terry Heard, mechanic for Trinity Materials, backed
the trailer into the maintenance shop. Johnson then drove Heard to the pit to
pick up the fork lift. Heard drove the fork lift back and parked it in the shop
near the trailer.
Heard went about other duties in the shop while Johnson jacked up the trailer
and supported the left rear with a jack stand. He removed the wheel clamps,
tensioning washers and nuts then positioned the fork lift with the forks under
the tire. He wrapped a chain around the back of the tire/rim assembly and
attached it to the load carrier guard on the fork lift.
Johnson attempted several times to loosen the tire/rim assembly from the wheel
by hammering on the back of the rim and tugging on it with the fork lift. He
also used compressed air to remove any sand and gravel lodged between the rim
and wheel that might be binding the assembly.
At about 12:30 p.m. Johnson, Heard and Farmer stopped for lunch. Johnson and
Heard discussed the problem of the rim being stuck to the wheel. After lunch,
Heard suggested that they let the air out of the tire. Johnson removed the valve
cap and depressed the valve core for 10 to 15 minutes. Johnson attempted several
more times without success to remove the tire and rim assembly by tugging on it
with the fork lift.
The jack stand had begun to slip out of place so Johnson repositioned it and
then asked Heard about using heat. Heard replied that it was up to Johnson.
Johnson positioned the oxygen/acetylene cart behind the left rear of the trailer
and began to heat the rim. After 45 minutes to an hour, Johnson called out for
Heard to come to the trailer. As Heard approached the right side rear of the
trailer the tire exploded throwing him backward. Heard recovered momentarily and
found Johnson lying unconscious against the inside of the right side rear tire.
Johnson's pants leg was on fire and while Heard was extinguishing the flame,
Robert Villa, plant manager, arrived. They pulled Johnson from under the
trailer. He did not have a pulse and was not breathing. Heard administered five
or six chest compressions and Johnson's pulse was restored and he began
breathing on his own. Villa administered first aid to control bleeding and
Farmer called the local 911 emergency assistance number. The sheriff's deputies
and an ambulance arrived a short time later. Johnson was transported to a local
hospital, where he died on March 1, 1999.
The accident was caused by the application of heat to the tire rim, which caused
a buildup and subsequent ignition of combustible gases inside the tire.
RDO Equipment Company
Citation No. 7874001 was issued on February 17, 1999, under the
provisions of section 104(a) of the Mine Act for violation of 30 CFR 56.4500:
A fatal accident occurred at this operation on February 17, 1999, when a tire exploded while a contractor employee was attempting to remove the tire/rim assembly from the rear of a Euclid B-30 trailer. After several attempts to remove the assembly failed, heat was applied to the rim with a torch. The heat generated combustible gases inside the tire which resulted in an explosion.
This citation was terminated on February 26, 1999
after the contractor issued a hazard alert to all employees and provided
training nationwide in safe work practices for removing wheels from mobile
equipment and prohibited the use of heat from any source.
Trinity Materials, Inc.
Citation No. 7874002 was issued on April 5, 1999, under the provisions of
section 104(a) of the Mine Act for violation of 30 CFR 56.4500:
A fatal accident occurred at this operation on February 17, 1999, when a tire exploded while a contractor employee was attempting to remove the tire/rim assembly from the rear of a Euclid B-30 trailer. After several attempts to remove the assembly failed, heat was applied to the rim with a torch. The heat generated combustible gases inside the tire which resulted in an explosion.
This citation was terminated on April 8, 1999,
after the mine operator provided training at all company operations in safe work
practices for removing wheels from mobile equipment and prohibited the use of
heat from any source.
Related Fatal Alert Bulletin:
FAB99M10
List of Participants in the Investigation
RDO Equipment Company
Timothy Lowe ............... service manager,
hewitt shop
William Cody Brown ............... warranty/safety manager
Bradley Campbell ............... general manager, product support
Trinity Materials, Inc.
Steven Andrews ............... safety director
Arturo Munoz ............... safety manager
Robert Villa ............... plant manager
Terry Heard ............... mechanic
Mine Safety and Health Administration
Michael C. Sanders ............... mine safety
and health inspector
Donald Peiffer ............... physical scientist
Richard Dunst ............... chemical engineer
Executive Summary of Laboratory Analysis
Trinity Materials, Inc.
Mine ID #41-03492, MSRS 049921
A laboratory investigation was conducted at the Approval & Certification Center
(A&CC) as part of the accident investigation for MSHA, Metal and Nonmetal Mine
Safety & Health, South Central District on the tire explosion accident that
occurred at Trinity Materials, a surface sand and gravel aggregate facility. The
laboratory investigation included literature review, visual and microscopic
examination, and ignition and heating tests on the damaged and undamaged liner
materials.
After completion of the laboratory testing and analysis, it was concluded that
the most likely event that caused the accident was the heating of the rim and
brake drum assemblies with an acetylene cutting torch. The heat from the
acetylene torch was conducted through the rim and into the tire material. The
tire material decomposed and produced hot embers and a combustible gas mixture
within the tire. The heated tire material provided an ignition source for the
combustible gases which subsequently ignited, causing the tire to explode.
Given that the tire before the explosion was at least at an initial pressure of
about 36 psig, a maximum explosion pressure of approximately 325 psig could have
developed. This explosion pressure would be over 3 times greater than would
develop from a combustion explosion at normal atmospheric pressure and over 3
times greater than the pressure at which the tire would be expected to fail if
over pressurized with air. The rate of explosion pressure rise could have been
about 7500 psi/sec and would be several times greater than would have developed
from a combustion explosion at normal atmospheric pressure. This magnitude of
maximum pressure and rate of pressure rise from an explosion in the tire is
consistent with the degree of physical damage observed at the accident site.
Comprehensive test results can be obtained from the Chief of the A&CC, RR 1, Box
251, Industrial Park Road, Triadelphia, West Virginia 26059.