MRO Today - Get a grip on ergonomics

Get a grip on ergonomics
Ergonomics is a process, not a product

by Dan Anderson

“Ergonomics” is a great word. Four syllables long and obtuse enough to sound important, it refers to the science of physically matching tools and equipment to minimize physical discomfort and improve efficiency of workers who use them.

Combine it with the words “hand tools” and you get six syllables that can impress the heck out of listeners and readers.

Unfortunately, just because a hand or power tool is ergonomically engineered does not mean it is perfect for every user and every application.

“There is no single tool that is ergonomically correct for every application,” says Craig Conner, product design engineer at Fiskars. “The benefits that can be derived from a tool are entirely dependent on how and where it is used. A tool that is ergonomic for one job or application may not be ergonomic for another.”

For example, an air-powered, pistol-grip nutdriver might be ergonomically well-suited for a worker who must install nuts on the vertical side of a large piece of equipment on an assembly line. But give that same pistol-grip nutdriver to a worker who installs nuts in a fixture on a waist-high table, and you may eventually have to deal with lost productivity due to that worker suffering a cumulative trauma disorder (CTD).

CTDs occur when a worker is required to twist, lift, or manipulate a tool, over and over, in an awkward position. The worker forced to use the pistol-grip nut driver on a waist-high horizontal surface must twist the wrist at nearly a 30-degree angle in relation to the forearm to do the job.

Micro-traumas are a big pain
Repeatedly forcing the wrist into an unnatural position
causes “micro-traumas” to soft tissues in wrist, elbow and shoulder joints.

Micro-traumas are microscopic injuries or irritations to tendons, ligaments and muscles that occur when joints and their associated soft tissues are stressed. Over time, micro-traumas can build into a painful, debilitating CTD. Carpel tunnel syndrome, tendinitis and epicondylitis (commonly known as “tennis elbow” or “carpenter’s elbow”) are just a few of the common CTDs that can develop when workers and their tools are not correctly matched.

The accumulated costs of such injuries are staggering. Government statistics indicate that in recent years, American workers have filed 330,000 CTD-related claims annually, at an average medical cost of $12,000 per claim, for a total cost of more than $3.9 million. Add in the cost of lost work due to CTDs and the damage rises to more than $27 billion each year.

Head off CTDs before they start
Taking a proactive attitude toward hand and power tool ergonomics can help decrease CTDs and their associated costs and dramatically improve worker productivity. A hand or power tool appropriately designed for a particular application allows the worker to use it efficiently and comfortably, without wasted motion or unnecessary effort.

“If tools are ergonomically correct for their applications, you will see reduced medical claims as well as increased performance and productivity because the right tools help workers do their jobs more efficiently,” says Conner. “The problem is getting the correct tools into the hands of the workers. Many times, the people who select or procure bulk tools do not actually use the tools themselves and have little or not contact with the workers who do.”

Conner says a tour of worker’s tool chests tells a lot about the ergonomic efficiency of the tools they have been given to use.

“Invariably, when we go into a facility, we see tools that workers have modified,” he says. “They pad the handles, they change handles; they are actually quite creative in making the tools better for how they are using them. Any time the workers start modifying their tools, it’s a good indication that the tools aren’t quite right for the job.”

How to select the right tool
Selecting tools that are ergonomically correct for an application starts with analyzing the relationship of the worker to the work. The worker who installs nuts on a vertical surface in front of him or her, as cited earlier in the story, gets along well with a pistol-grip nutdriver because that work situation keeps the wrist and forearm in a “neutral” position, where the middle two fingers and the bones of the forearm are in a straight line.

The worker installing nuts on the horizontal surface of a waist-high table could achieve that same neutral wrist/forearm position by using a cylindrical, inline nutdriver suspended from overhead. Grasping the cylindrical tool like a hammer handle, with the working end below the butt of his palm, keeps his middle fingers in alignment with his forearm and greatly reduces the chances of CTD.

A neutral wrist/forearm position also allows a worker to apply maximum force.

“Studies show that a worker has maximum strength when the wrist and forearm are in a neutral position,” says Joseph Centano, product research engineer for Snap-On Tools. “Any time you make the user bend his or her wrist, you decrease the amount of force available to operate the tool. If a worker is in a situation where the job requires him or her to constantly bend the wrist but still apply a lot of force, it’s better to bend the handle of the tool and keep the worker’s wrist and arm straight.”

Centano cites the situation where a worker must constantly bend a cotter key as part of an assembly process.

“Depending on the position of the work in relation to the worker, it may be better to give that worker a pair of pliers with bent handles so he or she won’t constantly have to twist at the wrist to do the job," he says.

Vibration shakes out workers
Vibration is another concern when using powered hand tools. Extended exposure to high- frequency vibration can cause hand-arm vibration syndrome, another painful and potentially expensive CTD. Cushioned tool handgrips or gloves can reduce vibrations transferred to workers’ hands; lubrication and maintenance may also reduce tool vibration.

“Tests show that well-maintained and lubricated air tools have less vibration,” says Centano. “Keeping (air-powered) tools lubricated and worn tools repaired can reduce vibration and make things easier for the workers who use them.”

This article appeared in the June/July 1998 issue of MRO Today magazine. Copyright, 1998.