Practical Ergonomics for Plant People
by Bernie Knill, contributing editor
Practical ranges from no equipment to computerized intelligent assist devices. Economic justification varies accordingly.
The phrase “Now that the OSHA ergo regulation has been shot down ...” doesn’t mean much to a plant manager. He or she will be facing the same choices that were there before: how to balance safety and productivity, while reconciling the needs of business and workers.
Especially at the plant or warehouse, ergonomics and business share strategies and equipment. Says Peter Budnick, president of ErgoWeb Inc., “What we talk about with our clients is that ergonomics should be approached from a business improvement perspective. And there’s a lot of opportunity for business improvement; reducing musculo-skeletal disorders is one of those opportunities.
“We at our company look at ergonomics as much more than a musculoskeletal issue. Injuries are one of the natural outcomes of poor workplace design. But so is lost productivity, loss of efficiency, errors and increased waste in your process. We really look at ergonomics as a broad approach to improving human performance,” says Budnick.
Stover Snook, who retired as assistant vice president of ergonomics and director of the ergonomics laboratory at Liberty Mutual Insurance Company, adds human fatigue, discomfort, human error and environmental stress to the list of ergonomic problems, as well as low levels of illumination, heat stress and vibration.
At Liberty, Dr. Snook did research in the area of practical ergonomics. “There are two aspects of ergonomics,” he says. “One is research and the other is applications.”
How important is research? Says Dr. Snook, “Before you can design a job and fit workers to the capabilities and limitations of the job, you have to know something about what the workers’ capabilities are. My research was dealing with manual handling because that was a problem from the compensation point of view — lifting and lowering, pushing and pulling — trying to reduce the incidents of low back pain. So my results were taken by the loss prevention engineers and applied in the field; I tried to express my results in a way that could be easily applied to our customers.” (You can find Dr. Snook’s research in many textbooks and white papers. Darcor’s white paper on “The Ergonomics of Manual Material Handling,” mentioned in this article, contains charts on push forces that were prepared by Dr. Snook.)
Material handling equipment has always showed an ergonomics side as well as its basic productivity purpose. Members of the Ergonomic Assist Systems and Equipment (EASE) Council of Material Handling Industry of America manufacture material handling equipment that has ergonomics as a primary characteristic — as well as productivity. Says Tom Carbott, the MHI executive for EASE, “There are benefits to an ergonomics program, ranging from the reductions of health-care premiums and workers’ compensation premiums to increased worker productivity, morale in the workplace and safety.” Among these motives, Carbott favors ergonomics as “a means to control your health-care premiums.” He explains: “If you could put an ergonomics program in place and achieve even a one percent or two percent savings in your health-care premiums, that would be worthwhile. A lot of insurance companies are willing to provide that kind of reduction if you have a program in place.”
The full range of equipment manufactured by EASE members can be found in “Application Guidelines for Ergonomic Ease and Safety Equipment,” available from MHI’s literature department, (704) 676-1190.
Practical ergonomics adopts computer control
The intelligent assist device is the leading edge of practical ergonomics. Let’s discuss this development first, then return to basic ergonomics equipment.
Every material handling device can boast of certain ergonomic characteristics, but the intelligent assist device (IAD) does the most for the operator, the product and the application. The device in this case is Gorbel’s G-Force intelligent lifting device, a hybrid computer-controlled hoist guided by a human operator.
You want to lift heavy loads? You want precise handling? You want speed in lifting? You want to spare the operator’s back? G-Force does it all. You just need the right circumstances to justify its high price. And that isn’t too great an obstacle when you’re able to show an economic justification. “We’re focusing on the early adopters of the G-Force, and we’ve seen a lot of different uses, which has surprised us,” says David Butwid, vice president and general manager, Gorbel. “We thought we’d see primarily high-speed applications, and we’re seeing probably just as many precise handling applications.”
Mark Grandusky, G-Force product specialist, speculates that there is a split between customers who want speed of handling and those who want precision and smoothness of motion. Grandusky is no stranger to a customer’s economic justification rules or preferences. “With the G-Force we can justify a purchase based on reduced product damage or an increase in productivity — they’re easier to quantify with the customer,” he says. “When you’re talking about the ergonomic benefits, you have to get into the numbers on the average cost of a worker, etc. With the G-Force you can show test results that illustrate how the customer can move the part from here to there X percent faster than whatever he’s using now.”
If speed isn’t important to the operation, maybe product protection is. “Because of the precision of the G-Force, you’re not dinging a part when you’re trying to assemble something. You’re not damaging the product or creating rework. With the G-Force, you can guarantee that you’ll reduce scrap by at least 30 percent,” Grandusky says.
Product flow is important for the application of any IAD. Let’s say that a workcell is designed around a critical assembly operation. If you increase that workcell’s productivity — output per person per amount of time — you’re better able to justify the purchase of an IAD.
Weight of the product is important. If a part weighing 500 pounds is moving through production, the operators have to use some kind of lifting device — they can’t do it manually. But if the part weighs only 50 pounds, an operator may get impatient with the slowness of a lifting device and decide to move it manually, even if the part is expensive. Since a G-Force enhances the operator’s movements, he or she gets precise handling without delay.
Jeff McNeil, product manager for Gorbel, explains: “From an operator’s standpoint it feels very natural. He moves his arm and hand, and this lifting device follows him around without delay. It senses load and change in speed or direction about 100 times a second; it’s so fast the operator can’t tell. The operator needs no training; he grabs the handle and moves as fast or as slow as he likes.”
Practical ergonomics: start with casters
“All casters that roll are ergonomic to some degree, but we look at material and construction of the caster, the way it’s put together to improve the mobility, to make it easier for personnel to push, pull or maneuver the cart,” says Cyril Muhic, international sales manager, Darcor Casters. “Take two eight-inch-diameter wheels, for example. You could look at two eight-inch wheels and they would appear to be identical. But when you put a load on each caster, one type of wheel material will permit the caster to move easier than the other type that doesn’t have the same properties,” says Muhic.
Selection of the proper caster depends on application, as well as construction, Muhic points out. He cites the example of a tug bringing a number of carts to a workstation. A worker then has to unhitch the carts and maneuver them into position for unloading. “You might want a heavier caster because the carts are being towed by a tug; since the operator isn’t necessarily concerned about speed, the casters should be more robust,” Muhic says. The right casters make it easier on the operator, on the tug, on the cart and on the floor.
Darcor, in cooperation with ErgoWeb, has published a 24-page white paper that discusses topics such as rolling resistance, factors that affect a person’s ability to push or pull, and a guide to designing a push/pull task. There are sections on caster or equipment design and caster and wheel selection, as well as an appendix of charts on initial and sustained push forces.
“The Ergonomics of Manual Material Handling” is available in hard copy from Darcor Casters, 7 Staffordshire Place, Toronto, ON M8W I2I or on Darcor’s Web site, www.darcor.com.
Practical ergonomics: selecting a tilter
A lift table (sometimes called a scissors lift) may be used “to position material so operators do not have to lift excessive loads, lift repetitively or bend to do their jobs,” according to documents from the Ergonomic Assist Systems and Equipment (EASE) Product Council of Material Handling Industry of America. EASE goes on to say that “tilting devices can be added so loads can be positioned both vertically and angularly.”
Matching a tilting device to a load and a container is the subject of a new program on the Internet from Southworth Products. “We’re trying to match the application to the equipment — and, consequently, match the economics,” says Brian McNamara, Southworth president. “The vast majority of wire baskets or containers are three or four feet high; a few of them are fixed height, but most have a drop gate. So what we tried to do was simplify containers by saying that you have tall, fixed walls; tall drop gates; and short ones.
“Then we went over to the other side and tried to break down loads into a common denominator. For example, there are only two ways to put tall parts into containers. Small parts like tennis balls are either put in containers at random, or stacked neatly like light bulbs. Then you have things like small pipes or flat bars, and those become what we call short vertical. And when you think about it, there’s not much else out there,” McNamara says.
The load and the container relate to tilt selection. “If I have tall parts in a tall container, the charts will tell me that I should be using a fixed-height tilter. I will be picking those tall parts from the top of the basket. I don’t need anything that’s going to lift. The parts are there right in front of me,” McNamara says. In this case, the lift table is a waste of money.
“That’s why we’re doing this,” McNamara says. “We see people buying lift and tilt, and when we see the equipment in operation, they don’t use the lift.
“We figure that if more people realized how inexpensively they could solve their problems, not all but 90 percent of them, they would invest in more equipment,” he concludes.
You can find the tilt selector guide at www.southworthproducts.com.
Practical ergonomics: vacuum is versatile
“I would say that there’s greater use and acceptance of vacuum than a few years ago,” says Franck Vernooy, president, Anver Corporation. “Anver is a specialist in vacuum technology. We supply from the rail down: the lifting tube, the pump, motor, etc. You can see it on our Web site.” Vernooy could have added components, complete systems, and custom equipment — which is the full range of equipment for lifting by vacuum.
Vacuum is expanding its versatility, says Vernooy. “Now you can pick up more porous loads, like bags and boxes, with the same equipment. It used to be that if you bought a vacuum lifter for porous material, you couldn’t use it on non-porous — the pumps would burn out. Now there’s new technology that allows you to handle both, making the equipment more versatile.
“Also, the payback has accelerated, and quite often you’re looking at a six-month to a year payback,” Vernooy says. “Previously the payback could be two years.” One of the reasons is that the price of the equipment has come down.
“Also, the vacuum lifting industry has benefited from the development of overhead light track systems. Improvements in enclosed light track have made vacuum handling equipment easier to move around,” says Vernooy. It used to be that the overhead structure was too heavy for the operator to move around easily. “Anver makes all the lifting devices but not the track, which is made by companies like Demag, Gorbel and Spanco. Typically, it’s sold by an ergonomics dealer that carries lift tables, overhead cranes, vacuum lifters, enclosed track and workstation cranes,” Vernooy says. The dealer would have installation capabilities. He supplies the overhead crane, the vacuum lifter and the installation — it’s sold as a system.
“We sell only the vacuum portion,” Vernooy says, “but, in a way, the vacuum portion of the system is the tail that wags the dog, because it’s the customer’s end effectors that make or break the system. We supply what we call a standard system, which is a standard with a custom end effector.
“Almost everybody’s load is different. So custom is standard for us,” says Vernooy.
In metropolitan areas, dealers tend to specialize. Some might not sell systems that handle more that 1,000 pounds.
Vernooy points out that the dealer has to make all the measurements. “The dealer has to determine, for example, if there’s enough headroom for the crane. You can’t do that over the phone. Where is the load to be picked up? How high does it have to go? How many items per minute?
“The best dealers act as consultants,” Vernooy concludes. MHM
Does Practical Ergonomics Need Equipment
Hardware isn’t always the first thing that Karl Siegfried thinks about as director of ergo-nomics for the Maine Employers Mutual Insurance Company (MEMIC). His understanding of a client’s needs and financial constraints is taken into consideration and often points to administrative controls such as worker rotation, work enlargement, stretching exercises, training and education.
“We recommend equipment, up to a point. If a com-pany asks for help, I will help it or refer it to a material handling specialist,” says Siegfried.
“We try to give a company two or three solutions. The best scenario is greenfield — complete automation — and then we step it down from there. As long as clients take action to reduce their losses, everyone wins.”
Reducing client injuries is MEMIC’s chief goal. “When MEMIC was created in 1992, the workers’ comp system in the state of Maine was horrific — businesses were leaving the state left and right. The governor put together a Blue Ribbon Commission, which decided that the best solution would be to institute a workers’ comp system that was basically owned by its stakeholders. MEMIC has led the way by insisting on workplace safety standards that are not only effective, but practical,” Siegfried recalls.
Ergonomics is an important strategy for MEMIC. “Most policyholders accept the idea that ergonomics has a place in their place of work,” Siegfried says. “They understand that good ergonomics is good economics.”
MEMIC is a private mutual company that serves as the guaranteed market for workers’ compensation in Maine. Since its inception, workplace injuries in the state have been reduced by more than 20 percent.
In recent years, the company has expanded into New Hampshire as MEMIC Indemnity Company. That company is also licensed in Vermont and Massachusetts.
Siegfried and ergonomics staff members handle all types of industries, ranging from wood and paper mills, fish processing plants, to hospitals and restaurants.
“We provide expertise and give them programs to implement that will help reduce their losses,” Siegfried says.
The ergonomics approach
Siegfried explains that the approach he or a staff member takes is to first meet with the CEO or CFO of a company to assure their commitment to the safety process.
“We then assess their risks, perform a detailed quantitative ergonomics analysis and issue a report, which, we’re told, is among the most detailed reports in the insurance industry,” he says. “Then we go through the findings with the customer and develop a service action plan they can follow to implement the changes and recommendations we have suggested. Finally, we follow up with them to make sure that they do the required work.”
How does economic justification fit into this approach? First, it’s up to the company to perform a total cost benefit analysis, should they need it, says Siegfried.
“Most companies in Maine understand that ergonomics pays off in the long run. It’s an attitude and a culture. I’m not saying that we don’t have to go in and sell some of the companies on the solution.
“I’ve found that the more detailed an ergonomist or safety consultant can be when he makes recommendations, the easier it is to sell the point.”
Clients know that ergonomics makes sense, and good ergonomic practices result in reduction of losses and increases in productivity. Administrative controls are often among the “good ergonomic practices” employed.
Says Siegfried: “We’ve had pretty good success with stretching programs. We recommend stretches three times a day: in the morning before employees start work, at the end of the first break, and at the end of lunch.”
Each stretch break lasts from six to 12 minutes, and should be mandatory.
A newer ergonomics tool is worker rotation that targets muscle groups.
“Worker rotation works very well when you rotate people into jobs that require the use of different muscle groups to perform work tasks,” says Siegfried. “We started from scratch and designed our own method to evaluate the exposures. We had to identify what muscle groups were used for what tasks, then quantify the effort being used. The information was then put into a matrix-type schedule. Supervisors rotate their people every two hours through jobs that require different muscle groups.”
It’s a different kind of practical ergonomics. But it works well for Karl Siegfried and MEMIC in reducing injuries and keeping down workers’ compensation costs in Maine..
Software from EASE
The Ergonomics Toolbox developed by the EASE Council evaluates manual material handling tasks and applies ergonomic solutions, including ergonomic assist devices and traditional material handling equipment. The program consists of four key components:
• Introduction to ergonomics. An overview of ergonomics and material handling that defines the various types of ergonomic intervention and explains analysis of the work system/task.
• Ergonomic hazards. An educational section that defines primary task characteristics with AVI video and text.
• Task evaluation. A task analysis tool with drop-down menus that is accurate based on the most widely used analysis tools. The program allows users to input job criteria and then receive material handling parameters based on the job.
• Equipment recommendation. Based on the criteria generated in the task evaluation section, users can review a selection of ergonomic assist devices that can provide solutions to their specific problems.
The Ergonomics Toolbox is available on CD-ROM, and costs $75 per copy plus $5 handling and shipping from MHI’s literature department. Phone (704) 676-1190; fax (704) 676-1199.
Best Material Handling Begins at Home
Best Diversified Products designs, builds and installs top-quality, custom-expandable conveyor systems for loading and unloading trucks at distribution centers and retail stores throughout the country. Its customers include some of the biggest, and most demanding, names in retailing — Wal-Mart, Sears, Lowe’s, Circuit City and many more.
When Stephen Watkins was hired last year as manufacturing coach at Best’s busy plant in Jonesboro, Arkansas, the production rate, as measured daily in person-hours per foot of conveyor section assembled, was averaging .250 or slightly higher (slower). His job, he was told, was to “hold the line” at .250.
Early on, Watkins noticed bottlenecks at the first assembly stations on two production lines for gravity-feed conveyors. Here, standing at tables, workers bolt small brackets to steel bars called roller angles. Farther down the line, where the conveyor sections begin to take shape, Watkins sometimes saw other workers with nothing to do, waiting for more roller-angle assemblies before they could add axles, wheels and other parts.
Watkins also grew concerned about back strain at the first assembly stations. About an inch wide, roller angles vary in length from 18 to 30 inches, depending on the type of conveyor being built. Although boxes of brackets were on the tables within reach, the much heavier roller angles were kept in large metal bins that had been set down on the floor several steps away. The lift truck that brought full bins to the work area could not be maneuvered between fans and other bins to get any closer to the worktable. Repeatedly throughout a shift, employees would each walk to a bin, which is only three feet high, and bend over to scoop up as many of the bars as he or she could carry back to the table in both hands. As the level of parts in the bin dropped, he or she would have to bend lower.
Watkins called in Tencarva, a Memphis-based distributor for Southworth Products. After discussing the particulars of his assembly lines with a Tencarva sales representative, Watkins decided to purchase two Southworth E-Z Reach Portable Tilters, Model PTU-4.
Model PTU-4 is specifically designed to provide safe, easy access to parts in wire baskets or other large containers. The unit rides on front rollers and rear swivel casters, and can be wheeled easily under any container with fork clearance. Once the container is wheeled into position at the work area, the operator uses a pushbutton wired remote to activate the tilter’s powerful hydraulic system. The E-Z Reach tilts to the most convenient angle up to 85°, so that the contents of a container, even at the bottom, can be kept at least waist-high — accessible without bending or stretching. Capacity is 4,000 pounds, mast height is 31 inches, overall width is 34 inches and overall length is 58 inches.
On a Best production line these days, a loaded tilter is rolled right up to the first table, delivering a fresh supply of roller angles to the six workers who draw from the tilted container. The second tilter serves another six workers at the other assembly station. Because the tilters dramatically reduce walking and bending at the critical starting points of the two production lines, they speed the entire assembly process.
In the months since the tilters were added, the previous average of .250 has improved to about .235 person hours per conveyor foot assembled. What sounds at first like a small difference adds up to big savings for Best. With both production lines running for eight hours, 40 employees working at the new rate can assemble approximately 100 additional feet — an average retail value of $5,000 more per shift.
For more information, contact Brian E. McNamara, president, Southworth Products Corp., P.O. Box 1380, Portland, ME 04104-1380. Phone (207) 878-0700; fax (207) 797-4734; e-mail: [email protected]