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Machine Guards and Amputation Hazards

By Graphic Products Editorial Staff

The risk involved with operating or maintaining industrial machinery is so great that it was one of the first facets of workplace safety to be regulated by OSHA back in 1971. It has always been considered a high risk activity and OSHA even did a nationwide emphasis program on amputations as they pertain to machine use back in 2006. Accidents resulting from machinery are all too common and often result in death or amputation. Each year approximately 700 workers are killed from coming in contact with objects and equipment and approximately 5,000 workers sustain an injury that results in amputation. Machine guarding accidents carry a distinct sting with them. This sting is the knowledge that a workers life was needlessly taken or will be irreversibly changed by the absence of a simple lock or piece of metal or plastic. Take the recent story of Kim Duong. Kim had worked for the steel fabricating company John Crowley Inc. off and on for six years. He was well known around the company, revered for his work ethic and safe practices. Earlier this year Kim was crushed by two six-hundred pound machine guards. Kim was operating a shot blaster, a machine used clean, peen or polish metal, when he climbed underneath the guards and bumped them causing the guards to fall. This story leaves questions unanswered, such as, were the guards properly installed if a ‘bump’ from an operator could cause the two six hundred pound guards to fall? Questions will be answered, as OSHA is conducting a full investigation; but that doesn’t change the fact that what amounts to a simple mistake needlessly took a good man’s life in an instant.

But death is only one of the undesirable outcomes of machine guarding accidents. Amputation is one of the most severe and crippling types of injuries a person can sustain and it often results in permanent disability or mental trauma. They occur most often when workers operate unguarded or inadequately safeguarded machinery. Kina Repp is a woman who sustained an injury on her first day at a new job that resulted in the amputation of her left arm. Her life was never the same and she had to adapt, relearn basic skills and now helps promote worker safety, empowering employees to take responsibility themselves. Her message is one of awareness and education, urging those who work in dangerous conditions to stay safe and assuring workers who have sustained amputations that their lives can be full and rich. Kina Repp examplifies that you are only as limited in life as you believe yourself to be.

Pit Bull or Pomeranian?

I like to think of heavy machinery like dogs, they come in all shapes and sizes and some are naturally more dangerous than others. Fortunately with proper training and protective measures there’s always a way to effectively use any machine; just as there is always a way to give any dog a good home. Identifying amputation hazards at your facility can be tricky if you aren’t sure what to look for. OSHA defines an amputation hazard as any moving machine parts that have the potential to cause severe workplace injuries, such as crushed fingers or hands, amputations, burns, or blindness. Amputation hazards fall under the arena of safety known as machine guarding because the best way to prevent these injuries are adding safeguards to hazards. As a general rule of thumb: whenever a machine uses reciprocating, rotating and transverse moving parts,there’s high likelihood it’s a hazard. Here are some more specific mechanical components that when exposed often create amputation hazards:

  • Flywheels
  • Pulleys
  • Belts
  • ChainsCouplings
  • Spindles
  • Cams
  • Gears
  • Power Transmission Apparatuses

Some machines are immediately labeled as dangerous, I refer to these at the pit bulls. Here is a short list of some of the most prevalent machines that create high-risk amputation hazards:

  • Power Presses
  • Power Press Brakes
  • Powered and Non-powered Conveyors
  • Printing Presses
  • Roll-forming and Roll-bending Machines
  • Food Slicers
  • Meat Grinders
  • Meat-cutting Band Saws
  • Drill Presses
  • Milling Machines
  • Shears
  • Grinders
  • Slitters

These machines don’t have to be operating to create a hazard. Often workers sustain injuries from improper cleaning or maintenance procedures. Lockout / Tagout is the best way to assure worker safety during maintenance and should always be present when machines, like these, create such serious hazards. It should also be noted that amputation hazards can also be present, even when large machinery isn’t used. There is a connection between amputations and material handling activities such as when forklifts are present or when heavy doors and trash compactors are used, as well as the use of handheld power tools.

En Garde

User Built vs. Producer Built Guard

The most efficient way to reduce and eliminate amputation hazards is though machine guarding.

Guards designed and installed by the machine producer are always preferred because they fit to the exact design and function of the machine. User-built guards are sometimes necessary but can have some advantages. Often, with older machinery, user-built guards are the only practical solution. They might be the only choice for mechanical power transmission apparatuses in older plants. User-built guards can be designed and built to fit unique and changing situations and can be installed to eliminate specific hazards presenting issues. Also, when workers are aware of the design and how the guard is installed machine guards, they gain a better knowledge of those guards and how they work. There are some disadvantages. User-built guards might not conform well to the machine, might not be effective and might be poorly designed or built. Always consult the manufacturer, even when building a machine guard yourself to assure that you aren’t overlooking any potential hazard, or creating a new one.

Guards are constructed from metal, plastic and wood. In many circumstances, because of the strength, durability and longevity, metal is the best material for guards. Plastic guards are primarily used when higher machine visibility is required. Guards made of wood are not compliant for most cases because of wood’s flammability, lack of strength and often flimsy nature. Wood guards are only preferred in industries that utilize chemicals, gases or vapors where manufacturing conditions would quickly deteriorate metal guards. Wood guards also may be used in construction work and in outdoor locations where extreme cold make metal guards undesirable.

A Guard is not a Guard is not a Guard

Once amputation hazards have been identified, the next step in protecting workers is determining the best type of guard for the application. Different machines require varies types of guards. The type of operation, the size and shape of machine, the method of handling, the physical layout of the work area, and the type stock being worked on, as well as the production requirements or limitations all come into play when determining the best method for safeguarding. Safeguards can be grouped under four general classifications:

  • Fixed guards- permanent parts of a machine, these guards are preferable because they're simple and permanent.
  • Interlocking Barrier Guards- Automatically shuts off or disengages a machine through a tripping mechanism or power when the guard is opened or removed.
  • Adjustable guards- Useful because they accommodate various sizes of stock.
  • Self-adjusting guards- Allows the opening of the barrier to be determined by the stock. As the operator moves the stock into the danger area, the guard is pushed away, allowing entrance

Here is a table for quick reference when deciding what type of guard to use at your facility:

Type Safeguarding Method Advantages Limitations
Fixed Barrier that allows for stock feeding but does not permit operator to reach the danger area.
  • Can be constructed to suit many applications.
  • Permanently encloses the point of operation or hazard area
  • Provides protection against machine repeat
  • Allows simple, in-plant construction, with minimal maintenance
  • Sometimes not practical for changing production runs involving different size stock or feeding methods
  • Machine adjustments and repair often require guard removal
  • Other means of protecting maintenance
Adjustable Barrier that adjusts for a variety of production operations.
  • Can be constructed to suit many applications
  • Can be adjusted to admit varying stock sizes
  • May require frequent maintenance or adjustment
  • Operator may make guard in-effective
Self-Adjusting Barrier that moves according to the size of the stock entering point of operation. Guard is in place when machine is at rest and pushes away when stock enters the point of operation.
  • Off-the-shelf guards are often commercially available.
  • Does not provide maximum protection
  • May require frequent maintenance and adjustment

Interlocking Barrier Guards

Shuts off or disengages power and prevents machine start-up when guard is open. Should allow for inching of the machine.
  • Allows access for some minor serving work, in accordance with the lockout/tagout exception, without time-consuming removal of fixed guards.
  • May require periodic maintenance or adjustments
  • Movable sections cannot be used for manual feeding
  • Some designs may be easy to defeat
  • Interlock control circuitry may not be used for all maintenance and servicing work

Doors number 2 & 3

There are other modifications that can do be done to machinery to eliminate amputation hazards. These options typically are costly, but are nothing less than lifesaving. One option is an array of devices that use sensors to automatically shut the machine down if something has gone wrong or if the machine is being incorrectly operated. There are three types of these devices: Presence-sensing, Electomechanical sensing and pullback devices. Presence sensing devices use either photoelectrical light sources or radiofrequencies to detect when there is a disruption to an otherwise vacant space. Say rotating gears create a pinch point, sensors are set up to detect if anything enters the vicinity of that hazard and when the sensors detect movement, the machine automatically shuts down. Electromechanical sensing devices have a probe or contact bar that descends to the hazardous point before the operator can start the machine. This could prevent injuries caused by improper lockout tag out and maintenance procedures. The third type of device is called a pullback device and they are cables attached to the operator’s hands, wrists or arms. This may sound restrictive, but they are primarily used on machines with striking-action hazards and when the striking mechanism is engaged the operator’s hands simply cannot be in the way of danger. Other mechanisms can be installed such as trip controls, pressure sensitive body bars, safety tripods and tripwire cables which all quickly deactivate a machine in a time of danger.

All of these options are designed to stop machines during times of immediate danger, but never forget that workers need to be as familiar with the dangerous machinery they are operating as the manufacturer who made it. Never skim or go light with operator training and always make sure employees know what to do in case of an emergency. The more prepared we are; the less predisposed our brains are to kicking into fight or flight and making rash decisions in a time of crisis.

Further Reading

More information on Kina Repp and her story:
on YouTube

OSHA Quick Fact Sheet on Amputation Hazards:

OSHA Machine Guarding E-Tool:

Latest Information on the Kim Duong Investigation:

Related Resources