DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
REPORT OF INVESTIGATION
FATAL HAND TOOL ACCIDENT
Boone No. 1 Mine (I.D. No. 01-02908)
Oak Mountain Energy, LLC.
Maylene, Shelby County, Alabama
May 29, 1997
WALTER W. DEASON
Coal Mine Inspector
Originating Office - Mine Safety and Health Administration
135 Gemini Circle, Suite 213, Birmingham, Alabama 35209-5842
Michael J. Lawless, District Manager
The Boone No. 1 Mine is operated by Oak Mountain Energy, L.L.C., and is located at 8320 Highway 270, Gurnee Mine Junction, Maylene, Jefferson County, Alabama. The mine enters the Gholson coal seam through 12 drift openings and averages 44 inches in height. There are four shifts that produce coal seven days a week. The mine produces an average of 8,000 raw tons of coal daily from three continuous mining machines with a continuous haulage system. The mine employs 186 people, with 181 underground miners.
The immediate roof strata consists of 20 to 30 feet of medium gray shale and the main roof consists of 30 to 100 feet of sandstone. The roof is supported with 36 inch, 5/8 inch diameter, resin grouted rods installed on five foot centers. The main headings are developed on 50 to 80 foot centers. The roof control plan in effect at the mine was approved by the Mine Safety and Health Administration (MSHA) on November 19, 1996.
The mine is ventilated by a 7-foot diameter Joy exhaust fan, which produces 364,000 cubic feet per minute of air.
The last AAA inspection was completed March 28, 1997, and a AAA inspection is presently being conducted.
The principal management officials at the mine are:
Randall Vannatter..............................Director of Safety
DESCRIPTION OF ACCIDENT
On Thursday, May 29, 1997, at about 6:30 a.m., Jay Dempsey, Electrician; David Aldridge, Laborer; James Jackson, Bridgeman; and Daryl Altenhof (victim) Electrician, entered the mine after receiving instructions from 004 Section Superintendent Denver Wolfong to go to the 004 section and complete the installation of the conveyor drive unit. The miners arrived at the work site at approximately 7:30 a.m. and found that the boom section had already been attached to the conveyor drive unit by the previous shift. Altenhof realized that the conveyor belt would not clear the mine roof with the boom mounted in this position. Altenhof told Dempsey, Aldridge, and Jackson that the boom would have to be lowered so the conveyor belt would clear the mine roof. Altenhof left the area to perform electrical work in other areas of the mine while Dempsey, Aldridge, and Jackson lowered the boom on the drive unit.
To secure the boom and to allow the bolts to be taken out of the mounting brackets and be relocated in front and in a lower position on the conveyor drive, a Harrington 1-1/2 ton Cumalong was attached to a roof bolt in the mine roof and around the second circular cross brace from the discharge roller on the boom section. The Cumalong's lower hook and chain were used to form a sling around this cross brace. Also, a safety chain was placed around the circular cross brace and attached around another circular cross brace between the two conveyor drive rollers to prevent forward or backward movement. After the mounting brackets were relocated, slack was given in the safety chain and the boom was raised so the end of the boom could be placed back into the mounting brackets. The boom, however, would not rotate forward enough to allow the end of the boom section to fit into the mounting brackets. About that time, Altenhof returned. He got in between and underneath the boom section and the conveyor drive roller to place a second Harrington 1-1/2 ton Cumalong on the boom section and conveyor drive in order to pull the boom section forward to allow the end of the boom section to fit into the mounting brackets. Before Altenhof could place the second Cumalong, the chain of the Harrington 1- 1/2 ton Cumalong that was securing the boom section broke, allowing the boom section to rotate toward the conveyor drive. Altenhof was caught between the circular cross brace on the boom section and the belt conveyor drive roller.
Aldridge attempted to lift the boom section, then tried to use the Cumalong, but found that the chain was broken. He tried to jack the boom section and still could not free Altenhof. He realized that the safety chain had tightened up and the chain had to be cut. Jackson cut the safety chain and by that time the 001 Section crew, located two crosscuts away, arrived. They lifted the boom section enough so that Altenhof fell free.
An Emergency Medical Technician was present at the accident site and CPR was administered immediately. Altenhof's vital signs were checked, but none were found. Gary W. Bentley, the 001 Section Superintendent, was informed of the accident and he called to the surface and requested an ambulance. CPR was continued until the victim was removed to the surface and turned over to the ambulance paramedics. The victim was pronounced dead on the surface at 3:35 p.m. by Shelby County Coroner Jack Jones.
- The average mining height was 44 inches.
- Additional mining height was taken up to 8 feet to allow the installation of the 004 Section belt conveyor drive unit.
- There was a three foot abrupt change in the mine roof at the inby end of the conveyor drive unit.
- The conveyor drive boom section came from the manufacturer mounted on top of the belt conveyor drive frame assembly. The boom section mounting brackets had to be relocated to the front side of the belt conveyor drive frame assembly so that the conveyor belt would clear the mine roof.
- The pivotal adjustable screw jacks (2) that elevate the boom section were attached to the boom section and to the conveyor drive section while the miners were relocating the boom section mounting brackets.
- The Harrington cumalong S/N 315877 supporting the boom section during the relocation of the mounting brackets on the conveyor drive unit was rated at 1-1/2 tons (3,000 lbs).
- It was revealed during the interviews that the two cumalongs at the site were new.
- The boom section weight was 4,589 pounds (as per the manufacturer).
- The conveyor boom was raised slightly upward so that the bolts could be removed from the boom mounting bracket then lowered and shifted slightly back to allow more area while relocating the mounting brackets.
- A chain was placed around the 5- inch diameter cross brace on the conveyor boom section and around a brace located between the conveyor drive rollers to prevent forward and backward movement during the relocation of the mounting brackets.
- The chain that was placed around the cross brace on the boom section and around the brace located between the conveyor drive rollers was loosened after the mounting brackets were welded on and the boom section was hoisted upward to align the end of the boom section and the mounting brackets.
- The victim was positioned beneath the raised boom section attempting to reposition a second cumalong to pull the conveyor boom section forward and down to align the end of the conveyor boom section with the relocated mounting brackets.
- The chain on the Harrington cumalong S/N 315877 supporting the boom section broke, allowing the boom section to fall toward the conveyor drive rollers, catching the victim between a cross brace on the boom section and the front conveyor drive roller.
- The chain broke at the twenty first link. There was a twenty link segment of chain attached to the lower hook on the Harrington cumalong S/N 315877.
- The link of chain that broke on the cumalong that was used to support the boom section that failed was never located. (The chain link indicated on the drawings is the link cut by the crew when removing the boom section from the victim).
- MSHA's Technical Support conducted three load tests on the Cumalongs:
A good indicator of the load that has been applied to a Cumalong chain is the pitch or the inside dimension of the links. Harrington's inspection procedure specifies a 4.173" nominal dimension for the sum of the pitches of five adjacent links. If the pitches of five links elongates to 4.276" or greater, Harrington specifies the chain should be discarded. The average of the sum of five pitches for the chain in the S/N 315810 Cumalong (Cumalong that did not fail during the accident), over segments of the chain not likely to have been subjected to heavy loading (measurements of 7 different segments of 5 links each) was 4.1709" or slightly less than the nominal dimension. This indicated the Cumalong had not been previously subjected to heavy loads.
In the first test, a segment of 9 links was removed from the end of the chain opposite from the hook of the S/N 315810 Cumalong. This end of the chain is equipped with a stopper link which prevents the chain from being fed completely through the Cumalong. Because of this stopper link, it is unlikely these last links of chain would have been subjected to a load. This is important since previous heavy loading of the chain could affect the test results. This segment of chain was loaded to 19,000 lbs. at which point the connectors used in the load test machine broke. Although the failure load of the chain was not determined in the test, the chain did elongate from its baseline of 4.1709" to 4.5628". This is an elongation of 9.4%.
In the second test, the last 9 link segment (segment with stopper link) of chain was removed from the S/N 315877 Cumalong. The previous test was duplicated on an unloaded segment of the chain that failed during the accident. Stronger connectors were also used. One link in this segment of chain failed at 21,000 lbs. This chain elongated from its baseline of 4.1680" to 4.8335" or 16.0%. The link which broke was recovered and examined. The link broke at one of the rounded corners and not at the weld. A break at the weld could have indicated a manufacturing or material defect.
The final test attempted to duplicate the arrangement of the S/N 315877 Cumalong when it failed during the accident. The intact Cumalong, S/N 315810, was arranged with its lower hook and chain used as a sling around a 5" diameter, schedule 40 pipe. This pipe is the same size as the cross brace of the conveyor boom. Many unknown factors could vary the test results from what actually occurred. This arrangement does, however, represent the best estimate of the accident scene. The Cumalong's chain failed at 22,000 lbs. The chain failed at the 20th link from the hook, duplicating the location of the failure of the S/N 315877 Cumalong's chain at the time of the accident. The sum of the pitches of the five links, immediately connected to the link which broke on the segment of the chain still in the hoist, measured 4.8150" for an elongation of 15.4%. As in the second test, the link broke at one of its rounded corners and not at the weld.
- The elongation of the chain which failed at the time of the accident is substantially less than the elongation of the other chains. There are two causes that are considered most likely to have resulted in this difference.
First, failure of the chain might have occurred at a lower load due to a defect in the chain's material or its manufacture. From the inspections and tests there are no apparent material or manufacturing defects in the chain that could explain the failure of the link. A defect or damage caused by improper use could also reduce the strength of the chain. Specifically, repeated use of the Cumalong's chain as a sling, could be expected to result in damage to the chain.
- The second likely cause of the smaller elongation of the S/N 315877 Cumalong is that the chain may have been subjected to impact loading. This is the type of loading the chain would have experienced if the boom was supported by something such as cribbing with the Cumalong only loosely attached and the boom then fell and its full weight was caught by the Cumalong. While impact loading can result in less elongation, materials under impact loading generally fail at slightly greater loads than when they are gradually loaded as was done during the load tests.
Impact loading is supported as a likely cause of the chain failure when the handle forces to lift various loads are analyzed. Harrington Operator's Manual specifies that to lift the Cumalong's rated capacity of 3,000 lbs. requires that the operator manually apply a lever force of 58 lbs. From this, other lever forces can be calculated:
15,188 lb. lift @ 294 lb. lever force - weight of entire conveyor 21,000 lb. lift @ 406 lb. lever force
breaking load of S/N 315877
22,000 lb. lift @ 425 lb. lever force
breaking load of S/N 315810
It is unlikely that any of these lever forces could be manually applied to the Cumalong's handle to reach the chain's failure load, without the use of an extension pipe. No marks, however, were found on the handle of the S/N 315877 Cumalong that indicated an extension pipe was used. Note that it would take an extension approximately 6' long to reduce the manual lever force to 100 lbs. while lifting a load of 22,000 lbs.
- Harrington's operator's manual specifies two requirements that could be related to the failure of the chain at the time of the accident:
"The load chain shall not be wrapped around the load."
Although using the Cumalong's chain to form a sling was not demonstrated to decrease the capacity of the chain in the load tests, in general, the chain can be damaged by wrapping it around loads.
"The rated load shall not be exceeded." The weight of the conveyor's boom, alone, exceeds the 3,000 lb. rated load capacity of the Cumalong by over 1,500 lbs. Also, Harrington Hoists specifies that when two Cumalongs are used to lift a load, each Cumalong must have a rated capacity equal to or more than the load. "This will provide adequate protection in the event that a sudden load shift or failure of one hoist occurs."
- Finally, MSHA conducted inspections of the two Cumalongs, Serial No. 315877 (Cumalong that failed), and Serial No. 315810. Both were located at the accident site, although only one was used. The Cumalongs were inspected per the §4.3 Regular Inspection Procedure contained in Harrington Hoists' "Owners (Operator's) Manual and Safety Instructions for the Harrington Cumalongs Lever Puller" dated 5/15/96. The inspection of the Cumalongs did not reveal any design, material, or manufacturing defects that would have decreased their load carrying capacity.
The fatal accident occurred when a link of chain from a Harrington Cumalong failed, allowing a conveyor drive boom section to fall onto an electrician who was positioned beneath the boom section. The failure to securely block the boom prior to the electrician going beneath the boom section allowed the boom to fall. The initial failure to properly plan and develop the conveyor drive installation location by establishing sufficient entry height began a series of events that led to the fatal accident. The failure to use a sling in conjunction with the Harrington Cumalong and the failure to use cumalongs or other devices with an appropriate weight carrying capacity also contributed to the accident.
A 103 (k) Order No. 3015261 was issued to assure the safety of any persons in the area until the accident investigation was completed.
A 104 (a) Citation No. 3015214 was issued for a violation of 30 CFR 75.1726(b), stating that the boom section on the 004 Section belt conveyor drive unit was not securely blocked in position prior to work being performed beneath the boom section and conveyor drive unit.
Respectfully submitted by:
Judy A. McCormick for
Walter W. Deason
Coal Mine Safety and Health Inspector
Michael J. Lawless
Related Fatal Alert Bulletin: