A Cross Tie Processor Working at an East Texas Sawmill Died When Struck by a Guard Thrown from a Wood Chipper Machine as He Stood at His Work Station
Texas FACE 98TX074
A 34-year-old cross tie processor died when he was struck in the back of the head by a steel hood thrown from a wood chipper machine. The victim was at his assigned location waiting for cross ties to arrive so he could cut them to the desired length. The wood chipper was located approximately 30 feet away from him. The victim was facing away from the wood chipper when the hood suddenly separated and was thrown 30 feet through the air, striking the victim in the back of the head.
The local emergency medical services (EMS) responded within five minutes of notification. Attempts were made to revive the victim. He was transported to the local hospital where he was pronounced dead by the justice of the peace.
The TX FACE Investigator concluded that to reduce the likelihood of similar occurrences, employers should:
- Install guards according to manufacturers' instructions.
- Install a metal detecting device in the conveyor systems of process machines to protect against mechanical damage.
- Obtain the operators manual for the machine and incorporate manufacturer's recommendations into written safe operating procedures.
- Develop maintenance and inspection procedures to ensure that machines and equipment are properly maintained according to manufacturers' specifications and that employees follow safe work practices.
On January 21, 1998, a 34-year-old male cross tie processor (the victim) died when he was struck in the back of the head by a guard from a wood chipper machine. The TX FACE program officer was notified of the fatality by an OSHCON field consultant on January 23, 1998. On February 10, 1998, the TX FACE program officer visited the job site. The employer and witnesses were interviewed and the location was photographed. The OSHA representative who was assigned to conduct OSHA's investigation was contacted. The sheriff's report, EMS report and the autopsy report were also obtained.
The employer is a hardwood sawmill producing cross ties, lumber used for wooden pallets, wood chips, saw dust and fine grade hardwood used to make furniture. The employer had been engaged in this business for five years. There were 21 employees in the company, 13 of whom were working in the sawmill at the time of the incident. The deceased and worked irregularly for the employer over the previous 36 months for a total of 24 months. The sawmill runs continuously throughout the year.
The designated safety director was also the owner of the company. A written safety program, which included a written safety policy and written safe work procedures for the specific task the deceased was doing at the time of the fatal injury, was available. However, written instructions addressing the operation and maintenance of the wood chipper were not available. The owner stated that safety meetings were conducted on a monthly basis, but were not documented. Since the incident, procedures have been developed to document safety meeting.
New hire training is task specific and is conducted on the job (OJT). The victim had experience with the cross tie processor he was operating and was trained through OJT to operate it.
The company buys hardwood logs from various timber contractors and runs them through its sawmill before shipping the different products to regional customers. This involved using a radial arm saw to cut cross ties to the desired length. For this process, eye protection was available and used.
The equipment involved in this incident was a wood chipper. The wood chipper contains a disc which weighs approximately 2,000 lbs., and turns at a speed of about 700 rpm. The wheel has blades attached to the face of the wheel. Scrap lumber is fed into the machine via a trough containing a conveyor belt. The trough feeds scrap lumber into the machine at approximately a 45-degree angle. The wheel on the machine is guarded with a steel hood. Three quarters of the hood is fixed and has a vertical exhaust chute attached to it. One quarter of the hood has a hinge which allows it to be opened like a clamshell to partially expose the wheel. The moveable side of the hood is secured in place with pins inserted through vertical sleeves. The sleeves are attached to both the fixed and moveable sections of the hood. The sleeve holes align once the moveable section is put back in place and pins are then inserted through both sets of sleeves.
Prior to the event, the victim and coworkers reported for work at 7:00 a.m. At 11:00 a.m. the wood chipper was shut down so the blades could be replaced. The machine was then restarted at 11:15 a.m. and ran until lunch break at 12:00 noon. At 12:30 p.m. the machine was started back up. At approximately 12:45 p.m. one of the blades struck the side of the moveable hood, tore the hood from its hinge and threw it approximately 30 feet. It struck the victim in the back of the head.
The local fire department dispatched an ambulance to the scene at 12:47 p.m. They arrived at 12:52 p.m. The victim was lying face down and bleeding from the right side of his head and right ear. No carotid pulse could be felt. The victim was rolled over and a faint pulse could be detected but no breathing. Resuscitation efforts were initiated. The victim was transported to the local Hospital emergency room. The ambulance arrived at 1:05 p.m. The victim was pronounced dead at 1:57 p.m. by the justice of the peace.
The machine had run for five years with only one observed problem: the pins that were inserted through the sleeves would vibrate upward allowing the hood to open. Also, according to an employee, some time prior to the incident (date could not be confirmed) the hinge on the hood had been welded. In addition to securing the hood with pins, a chain had been placed and tightened over the hood. This had been done to create a better vacuum within the machine. Prior to this incident, pins and the chain were in place. The pins apparently were still in place because all four sleeves and been split apart when the hood was ejected from the machine.
Maintenance records on the wood chipper were not being maintained by the employer. A manual for this machine was not available at the time of the incident.
The exact cause of the malfunction that resulted in the blade striking the hood could not be determined. One possibility is that tramp metal from the processed timber or other metal objects fell into the conveyor. The conveyor channels scrap to the inlet of the wood chipper. Tramp metal or other metal objects could cause serious mechanical failure, although no metal objects were found at the scene that could have caused this problem. There were no metal detecting devices installed at the time of the incident to prevent tramp metal or objects from being fed into the machine.
Subsequent to the event, a new guard was purchased and installed. The owner was told by the distributor that the appropriate method of attachment was to use bolts to secure the guard. The operating manual for the wood chipper does have a warning that states " . . . the disc should never be restarted until the hood and doors have been properly bolted and pinned . . . "
CAUSE OF DEATH
The medical examiner determined the cause of death to be basilar skull fractures, transection of the medulla and traumatic subarachnoid hemorrhage.
Recommendation #1 - Employers should install the guards according to manufacturers' specifications.
Discussion: The correct procedure for guarding the wood chipper should include securing the hood with bolts. Bolting the hood down lessens the chance of the hood being ejected from the machine should a similar incident occur. The machine vibrates when large pieces of scrap are cut. The vibration may have caused the welds on the hinge to crack. Bolting the hood in place reduces the force being exerted on the hinge.
This method of securing the hood is described in the owner's manual. At the time of the incident, however, the employer was not using the method of securing the hood recommended by the manufacturer. The method that was being used, that is, pins inserted through sleeves on the hood plus a tightly secured chain, is not strong enough to prevent the hood from being thrown from the machine.
Recommendation #2 - Employers should install a metal detecting device in conveyor systems of process machines to protect against mechanical damage.
Discussion: Since the conveyor travels below other machines and employee work stations, foreign objects such as tools could fall onto the conveyor belt. It is not uncommon to find metal embedded in the trees remaining throughout processing. A metal detector could provide the safeguards necessary to keep metal objects from entering the wood chipper and causing serious mechanical failure. Although no pieces of metal were found at the scene that could have caused the machine to malfunction, detectors can detect the metal and automatically stop the conveyor or send a signal to the operator so the machine can be manually stopped.
Recommendation #3 - Employers should obtain the operators manual for the machine and incorporate manufacturer's recommendations into written operating procedures.
Discussion: The wood chipper was purchased used and put into operation. An owner's manual was not included with the purchase nor did the employer make an attempt to acquire a manual. In addition, the wood chipper was not addressed in the employer's safety manual. In order to know if the machine is being properly operated and maintained, an owner's manual is required. The manual will serve as the standard from which to make decisions on installation, operations and repair. Guidelines on safety, maintenance, and other key information that are commonly provided in manufacturers' specifications are key to developing appropriate safety and maintenance protocols for these machines.
The manual for the wood chipper contained the following warning: "Never loosen or open the hood or any of its doors until the disc has come to a complete stop. Also, the disc should never be restarted until the hood or doors have been properly bolted and pinned with all the bolts and pins provided. To operate this machine in any way without the hood or doors being properly secured could cause considerable damage and personal injury."
Recommendation #4 - Employers should develop maintenance and inspection procedures to ensure that machines and equipment are properly maintained according to manufacturers' specifications and ensure employees follow safe work practices.
Discussion: Inspecting the work environment can be a valuable aid in detecting potential causes of injury and unsafe work practices. The inspection, however, should by no means constitute the only activity for isolating and defining hazards, because, regardless of its value, it is not always possible to see all potential hazards at all times. Inspections are most useful as an integrated part of a comprehensive safety program for identifying risk factors in the following areas: equipment, environment, people and management. The employer should institute spot inspection tours at least once each day. Inspecting and checking equipment by operating personnel should also be integrated into their working procedures. In order to make certain that the inspection is carried out and performed thoroughly, the employer should develop an inspection checklist.
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