A worker at a poultry plant was injured when she got too close to a mechanism for stapling turkey bags. There were no interlocked safety gates or emergency-stop (e-stop) buttons on the machine when the accident happened.

The machine involved in the accident carried up to 16 plastic-bagged turkeys at a time around a central hub while sucking the air out of each bag, stapling the bags closed, and delivering each bag to a conveyor moving it to the next station. Each of the 16 stations had a two-sided clamping mechanism to secure the bag on the suction port. When the clamp halves opened, each nearly touched the clamp half of the adjacent station.

It wasn’t uncommon for the staples feeding the machine to jam, setting off an alarm that called for operator intervention. Operators climbed a step to unjam the stapling mechanism. They also had to reach between the stapler and the clamp apparatus to disable the jammed-stapler alarm.

The accident happened after the worker unjammed the stapler. Her hand caught between the open clamp halves of two adjacent stations as she climbed down from the step. Seconds later, her arm was pulled under the stapler which jammed into her arm, severely injuring her.

Investigators quickly identified several problems with the machine’s design. There was no convenient way to perform lockout/tagout on the machine before unjamming the stapler. Consequently, workers performed this frequent, minor maintenance job with the machine running, placing themselves in a hazardous situation.

Turning off the jammed-stapler alarm meant reaching into a hazardous area between moving parts of the machine when the reset button could easily have been mounted in a safer spot. Another oversight was the lack of e-stop provisions that would let a trapped worker stop the machine.

In addition to these design flaws, safety documentation associated with the machine was scant. A few stickers warned users of pinch points, but there was nothing legible from a safe distance to warn workers of risks from moving parts, pinch points, or maintenance procedures.

Soon after the accident, the processing plant added two important safety upgrades: an e-stop button within reach of the workers’ station and a small interlocked gate that keeps workers away from the stapling mechanism and stops the machine if opened. MD

This month’s safety violation comes from the files of Lanny Berke, a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a safety violation to share? Send your images and explanations to jessica.shapiro@penton.com.

Edited by Jessica Shapiro

© 2011 Penton Media, Inc.

From the safety files of Lanny Berke: A man was injured when part of the hay grinder he was operating broke free and struck him in the chest. The grinder was running without a drivetrain guard at the time of the accident.

The hay grinder developed a worrisome vibration in its drivetrain 14 months after getting a new engine and flywheel cover. The grinder’s operator removed the guard over the drivetrain between the engine and the grinding mechanism and took the machine to the mechanic who had installed the engine to have the vibration diagnosed and repaired.

The mechanic wasn’t able to complete the repair that day, so the operator took the machine back to grind large, round bales of hay at a farmer’s field as scheduled, leaving the guard off. The farmer was working about 50 ft from the grinder when it stuttered and stopped. He subsequently found the operator face down on the ground and called 911.

Investigators determined a bent driveshaft caused the severe vibration. During grinding operations, the hammer mechanism of the grinder hit something hard that sent a shock through the driveline. The shock, combined with the stress from the bent shaft, fractured a universal joint. Without a guard to stop it, a knuckle of the joint flew out of the machine and struck the operator in the chest. At the same time, the engine overloaded and stalled.

The investigation determined that the previous installation of the engine and flywheel cover had nothing to do with the accident. It also found the guard, had it been installed, would have been substantial enough to stop the U-joint knuckle from flying out of the machine. The machine also contained warnings alerting users that parts could fly out of the drivetrain and that a guard was needed for safe operation.

However, the guard was not large enough or extensive enough to fully protect operators who could reasonably be expected to be working around the drivetrain while the machine was running. Because it was not hinged to the machine, it was reasonably foreseeable that the machine could be operated without the guard; there were no interlocks to prevent this.

The hay grinder manual could have discussed the operation of the machine’s components — including the engine, flywheel and housings, clutches, drivetrain, and guards — in greater detail along with their potential hazards. A list of symptoms indicating serious mechanical problems and a toll-free number where users could contact the manufacturer could also have helped the operator avoid the accident. MD

This month’s safety violation comes from the files of Lanny Berke, a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a safety violation to share? Send your images and explanations to jessica.shapiro@penton.com.

Edited by Jessica Shapiro

© 2011 Penton Media, Inc.

A 10th-grade student was badly burned while grinding metal in his school’s metal shop when sparks ignited his clothing. He was unsupervised when the accident happened and was wearing minimal protective equipment.

The student was working on a science project in the shop during his study-hall period. The shop instructor was two rooms away teaching a wood-shop class. He had given the student permission to work with tools in the metal shop and was checking on him occasionally.

Shop students had learned about handheld angle grinders along with other metalworking equipment earlier in the semester through their textbook and in-class instruction. The instructor taught shop students how and when to operate the grinder, but he didn’t discuss the grinder’s potential hazards like sparks and fragmenting wheels.

The manual for the grinder involved in the accident notes that sparks from the grinding wheel can ignite nearby flammable materials. It also calls for an operator to wear a “face shield or at least safety goggles, dust mask, leather gloves, and shop apron capable of stopping small wheel or workpiece fragments.”

Although hearing protection, face masks, and leather aprons were available, the instructor only insisted on safety glasses. He left decisions about other protective equipment to each student’s discretion. The injured student was wearing a loose-fitting flannel shirt, a cotton T-shirt, jeans, safety glasses, and ear coverings when the accident happened.

Sparks from the metal he was grinding ignited the flannel and quickly spread through the loose weave. The student tried to put out the fire at a nearby sink, but couldn’t work fast enough to stop the flame from spreading. He ran outside and tore off his shirt in the snow where he was found by a janitor. He sustained third-degree burns over 9% of his body. He had to be airlifted to a regional burn center where he received donor skin grafts on his back, side, and arm.

Just like any industrial environment, the school should have had formal safety procedures that met or exceeded OSHA regulations. Students should have learned to put out fires with extinguishers, fire blankets, and “stop, drop, and roll.” And the school should have required close supervision of minor students using powered equipment. Having others nearby in case of an accident is a basic power-tool safety practice, even for adults.

In class, the instructor should have covered the hazards of each piece of metalworking equipment. Because students weren’t told the grinder could generate sparks and ignite a fire, they couldn’t make informed decisions about the use of protective equipment.

Edited by Jessica Shapiro

This month’s safety violation comes from the files of Lanny Berke, a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a safety violation to share? Send your images and explanations to jessica.shapiro@penton.com.

© 2011 Penton Media, Inc.

One of the basic concepts of machine guarding is that a guard must not become a hazard or contribute to hazards. Thorough hazard analyses easily identify hazardous guards. Ideally, preliminary hazard analyses at the equipment manufacturer will identify and resolve guarding problems before they affect users.

I’ve previously discussed the problem of guards that can be left off without disabling machine operations. This often happens on conveyors of all lengths and capacities, especially on those with tracking problems. It would be easy to add an interlock to the conveyor design that would stop the machine from operating if the guard was missing.

Better communication about guards also improves safety. For instance, if maintenance personnel leave a guard off a machine after they’ve finished with it, a new operator starting the machine may not realize the guard is missing. Two simple ways to combat this are to paint the areas under bolted-on guards in eye-catching, contrasting colors and to post warning labels on the guard and on the machine in the spot where the guard should go. The warnings should inform workers not to operate the machine without the guard in place.

Guards that can themselves turn dangerous are less easily handled. One hazardous but commonly used safety measure is the plastic guarding the blade on many miter saws. I’ve investigated three identical accidents where these guards got bumped out of alignment and into the blade path. When the rotating blades hit the guards, the plastic broke up and forcibly threw dangerously sharp plastic shards into the operators’ fingers and hands. Nothing in the saws’ labeling or manufacturer literature alerted users to this danger.

Another type of unsafe guard is one that fails to stop material from being thrown out of a machine with enough energy to cause injury. One example I investigated involved a punch press that punched 1-in.-diameter, 1/8-in.-thick discs from oiled steel in high volumes. A stack of discs tended to build up in a horizontal collector until the next punch knocked over the stack and sent discs flying out of the machine with substantial force.

After a nearby worker was badly bruised by flying discs, the company operating the machine welded a barrier guard on the side of the disc collector where the discs had flown out. A second incident led them to guard a second side of the collector. The third occurrence was fatal; a flying disc hit the operator in the chest at short range.

If engineers at the machine manufacturer had conducted a proper hazard analysis they would have chosen a better initial design. For instance, sloping the bottom of the collector would have prevented discs from stacking up square to the punch and deflected the force with which they went flying. Such an approach would not have required guarding at all.

And if the employer determined guarding was needed, a thorough hazard analysis would have dictated complete guarding of all four sides.

Lanny Berke is a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a question about safety? You can reach Lanny at lannyb@comcast.net.

© 2011 Penton Media, Inc.

A lathe operator was fatally injured when the bar stock he was machining came loose and struck him. The bar was guided and guarded by a pneumatic bar feeder which had not been properly secured.

The CNC turning lathe the worker had been using to machine a 7/8th-in.-diameter metal bar was running at about 2,500 rpm at the time of the incident. Air pressure in the bar feeder was around 25 psi.

To load the machine, the worker slid the workpiece into the steel feeder tube of the bar feeder. A locking system and a support held the tube in place. The locking system consisted of two C-shaped sections that secured with four bolts to apply clamping friction to the tube. The friction kept the tube in place axially with respect to the lathe so workers weren’t exposed to the rotating workpiece. The support had a slot which let the tube slide between loading and machining positions. Technicians could activate a locking lever to hold the tube in machining position radially with respect to the lathe.

To load a new workpiece, the worker had to unbolt all four bolts on the locking clamp, release the locking lever on the support, slide back the tube, load the bar, then rebolt and properly tighten the locking-clamp bolts and reposition the locking lever. This happened multiple times during a single shift.

In this accident, improperly tightened lockingclamp bolts let the tube slide back as the machine vibrated, and the unsupported section of the rotating workpiece bent at an angle to the machine tool. The bent rod hit the worker on the head, cutting his scalp to the bone and fracturing his skull. He died 12 hours later at a local hospital.

Because the feeder system was both guiding and guarding the workpiece, the locking mechanism should not have relied on friction alone to hold the tube in place. Workers should have been able to more easily lock and unlock it to prevent errors and negligence. And it should have included interlocks that prevented the lathe from operating if the bar feeder was not secured. The bar feeder also needed warnings or instructions posted on it and in its manual.

This month’s safety violation comes from the files of Lanny Berke, a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a safety violation to share? Send your images and explanations to jessica.shapiro@penton.com.

© 2011 Penton Media, Inc.

When accidents result in serious injury, amputations are not uncommon. My columns usually focus on factors that lead to injuries with little mention of an injured person’s recovery. However, when there’s an amputation, either at the time of the accident or as part of the injured person’s treatment, prosthetic limbs often bring full or partial function to the injured body part.

I recently spoke with a woman whose leg was amputated many years ago as a result of a bicycling accident. It happened that she had been injured again in an accident that I was investigating, but her amputation was only a peripheral factor in the more-recent accident.

We discussed her artificial leg in great detail because it intrigued me from an engineering standpoint. Her leg used hydraulic and mechanical mechanisms, motion-control devices, and computer control. And it accounts for human factors as well or better than most machines I see in my line of work.

In general, those with prostheses do not appear to be more prone to later accidents. Of course, some amputees using artificial limbs are not able to engage in their previous work or leisure activities or they perform them in a modified way. And, in at least one instance, a long-distance runner’s prosthetic limb improved his speed.

The technologies used in prosthetic limbs continue to evolve into moreuseful and more-reliable devices. Prosthetic-device manufacturers are at the leading edge of a long history of artificial limbs.

Ancient literature and archeological finds show the Greeks, Romans, Egyptians, and ancient Indian societies all fashioned artificial body parts from wood or metal. Prosthetics were either minimally functional decorations meant to hide a missing limb or functional attachments that barely resembled natural body parts.

The technology for replacement limbs advanced little until the 16th century, when doctors developed hinged designs and better ways to attach artificial limbs to natural tissues. Starting in the 1800s, better surgery techniques, including anesthesia and antiseptic practices, let surgeons better prepare limb stumps to accept prostheses and cut amputation-related mortality rates.

Other advances have helped amputees control their artificial limbs. Engineers in the 1800s developed prosthetic arms controlled by the movement of the opposite shoulders via straps or cables. This has evolved to the conversion of nerve signals and voluntary muscle movements into electrical signals that control artificial joints.

Finally, the materials used in making prosthetics have evolved from metals — which were of limited use due to their weight — to wood and on to lightweight engineered plastics and carbon-fiber composites. Computer imaging and modeling also aid in designing and fitting modern artificial limbs.

I’ll discuss the state of the art of prosthetics and its implications for safety and product liability in upcoming columns.

Lanny Berke is a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a question about safety? You can reach Lanny at lannyb@comcast.net.

© 2011 Penton Media, Inc.

A worker from an outside company was severely burned after he stepped into molten zinc while installing an exhaust duct. Inadequate instruction about the hazards of the equipment and a lack of safety warnings and devices contributed to the accident.

The worker was tasked with installing a duct to exhaust high-temperature gases from equipment that held a zinc-plating bath. A maintenance foreman showed the worker where to install the duct, then left him to complete his task.

The worker needed to use a forklift to reach part of the installation. To get closer to his work, he stepped off the forklift and climbed on the base of the equipment.

He stepped onto the seemingly solid platform where he had previously placed a tool without a problem. It was actually a thin crust of zinc oxide that had formed over the bath of molten zinc. His right foot immediately broke through the crust. Then, as he attempted to free himself, his left foot and buttocks also touched the molten zinc, sustaining serious burns.

Another worker was able to free the injured man. The two tried to wash off the molten zinc, but there was only a small amount of water available nearby. The delay in flushing the metal from the skin exacerbated the worker’s injuries.

The worker had not been told what was in the tank or that the molten zinc forms an apparently solid crust that does not bear weight. There were no warnings on the equipment to alert him to the tank’s contents or hazards. Nor were there any guards around the equipment.

The incident resulted in several OSHA citations: The worker should not have been allowed to use the forklift without training; he should not have been allowed to work alone without being trained in the hazards of the work area; a guardrail or cover should have guarded the tank whether it was filled or not; and there should have been functioning safety showers near the zinc bath.

This month’s safety violation comes from the files of Lanny Berke, a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a safety violation to share? Send your images and explanations to jessica.shapiro@penton.com.

© 2011 Penton Media, Inc.

To design assembly press controls that perform safely worldwide, OEMs must understand key safety standards.

Editor: Jessica Shapiro

A worker was reaching into the operating area of a press brake to clean the die when he depressed the foot pedal that cycled the machine. The ram descended, crushing four of his fingers.

The machine carried one prominent placard warning against reaching into the die area. The dual-foot-pedal control also had a warning at floor level.

The worker’s supervisor had taught him to use a hook at the end of the ram to turn the die out of the operating area for cleaning without reaching into the operating area. However, he was cleaning the die in its operational position when the accident happened.

Company officials knew safety features on the machine, which was used for bending sheet metal, were not up to date. A voluntary OSHA walkthrough about a year before the accident had noted the press brake lacked safety devices or guards.

Clear plastic guards for the press brake would have interfered with some of the sheet-metal parts. And two-hand palm buttons wouldn’t have worked for 25% of workpieces which needed operators to support them during bending.

Eight months after the OSHA visit, the company chose a light curtain that could be programmed to work with the variety of parts. The equipment took two months to arrive on site. Shortly thereafter, the safety coordinator alerted OSHA that the light curtain was in use and avoided having to request a sixth correction-date extension.

In reality, maintenance personnel tried intermittently for another month to install the light curtain without success. Nor could a third-party company hired for the task set up the device so it wouldn’t shut down the machine each cycle.

During this year, workers were still operating the press brake without modifications. Safety staff had shown workers a video about the dangers of reaching into energized equipment and occasionally reminded them during staff meetings. A formal training process where workers signed off on what they were taught was still in development.

After the accident, the third-party lightcurtain installers took a full week of work to get the device running properly, but the effort came too late to save the injured worker from going through two surgeries and losing movement in his hand.

This month’s safety violation comes from the files of Lanny Berke, a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a safety violation to share? Send your images and explanations to jessica.shapiro@penton.com.

© 2011 Penton Media, Inc.

Edited by Jessica Shapiro

A bakery worker’s hand was injured in the piston of a dough cutter. The worker was cleaning stray dough from the walls of the machine’s hopper at the end of a batch. To do this, he had to reach over the rim of the hopper with a small scraper.

A portable three-step riser permitted access to the hopper from the back of the machine. However it was prone to being bumped by passing forklifts and didn’t provide a good angle for cleaning the hopper. From the top step, workers often climbed onto a flat portion on top of the machine and reached into the hopper.

The rim of the hopper was 14.5 in. above the platform. The moving piston of the cutter created a suction which pulled dough in to form loaves. The moving parts, located about 2 ft below the hopper rim, ran at 30 to 50 rpm.

The worker was standing on the platform, leaning in to scrape dough from the hopper, when his hand was pulled into the piston. He was able to free his hand and run for help, but not before he sustained an injury that kept him from returning to his job.

Investigators learned that machinery operators received on-the-job training from other operators for their assignments. And although workers said “everyone knew” to turn off machines before cleaning them out, there was no record of the injured employee or anyone else having been instructed in safe maintenance practices.

In addition, the machine lacked clear warning labels indicating pinch points and other hazardous conditions. Investigators also couldn’t find a user manual and had to obtain one from the machine’s manufacturer for their report.

Finally, workers had altered the wiring to bypass some of the machine’s safety provisions. For example, an interlocked control-panel door kept falling off, so the interlock was defeated to let the machine continue running. This bypass also defeated the emergency-stop measure. Someone nearby ran to turn off the machine’s power supply after his coworker was injured.

Investigators recommended a more formal safety program including proper use of lockout/tagout and interlocks. They also suggested a taller hopper or longer scraper as ways to prevent future accidents.

This month’s safety violation comes from the files of Lanny Berke, a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a safety violation to share? Send your images and explanations to jessica.shapiro@penton.com.

© 2011 Penton Media, Inc.