Backs and basics18 September 2019
Aching backs and pains in the joints are no longer acceptable as inevitable sideeffects of working life. Julian Champkin looks at how advances in ergonomic design and practice are helping to eliminating them.
Hit middle-age and you will know why ergonomics are important: they help to avoid the bad back or aching joints you get from lifting, carrying, bending, twisting, or otherwise putting your body through movements and actions that it objects to. Technically, and more precisely, ergonomics is the science of avoiding such outcomes: “the study of people’s efficiency in their working environments” (Oxford English Dictionary) or “an applied science concerned with designing and arranging things people use so that the people and things interact most efficiently and safely” (Merriam-Webster). Hoists and lifting apparatus are, or should be, a prime example of the practical application of ergonomics in the workplace.
It can be argued that simply the existence or provision of hoists, cranes, manipulators and the like are in themselves ergonomically beneficial: since the machines do the heavy lifting they reduce, perhaps to zero, the loads that human beings have to lift.
But musculo-skeletal disorders, to give them their proper name, do not arise just from lifting heavy weights. According to the US Department of Labor, bending, reaching overhead, pushing and pulling heavy loads, working in awkward body postures and performing the same or similar tasks repetitively all increase the risk.
A push-button control for a lifting mechanism is clearly an advance; but if reaching the button involves stretching too far, or leaning over the workbench in an awkward position, then it too can result in back-ache and injury. Sometimes small and simple changes, such as repositioning a control or reducing the springpressure needed to operate it, can have disproportionately beneficial effects.
Design of lifting apparatus is therefore of huge importance. Mark Grandusky is product sales manager for Gorbel, makers of cranes, ergonomic lifting, and fallprotection systems, and is their specialist in ergonomics.
“We make basic solution electric chain hoists and also advanced, higher-end intelligent lifting devices, which we call Float Load,” he says. “At a work-station the grabber of such a device grasps the load at a slight grip of the operator; it senses the up-down motion of the operator on the handle and lifts or lowers the load accordingly. Sensors in the handle electronically work out his intent and translate that to the matching speed. Once the load is suspended, then with just fingertip pressure the operator can guide it anywhere he wants. The load could weigh 300kg, you apply less than 1kg force to it, and the device does the moving. That has to be good for your body, and it is a very precise way of moving the load as well.
“We originally licenced the technology from a professor at Berkley California, who was describing it as a ‘human power extender’,” says Grandusky. “It brings obvious ergonomic benefits; and it also increases productivity. The Float Load lifter can go all round the factory, wherever the overhead track is laid; the goods are moved faster and more efficiently. Damage to products is reduced. It can set down the load gently—it cannot drop it; and, most important of all, health and safety of the operators are not imperilled.”
Perhaps surprisingly, neither in the US nor in Europe are absolute limits laid down for the maximum weights that a worker can be required to lift as part of his or her employment. This might seem strange, but many factors beside weight affect the health effects of lifting.
The frequency, and the amount of repetition, are particularly relevant. Lifting a load, say, onto the back of a truck once a month may be less damaging than performing the same operation for hours at a time five days a week. Loads may be lifted from a work-top, or, potentially more damaging, from ground level. The grip provided is important: the load may have no easy hand-holds in which case a tight grasp on it may strain muscles in the hand. Carrying and delivering to a perhaps difficult-to-reach setting-down place imposes other stresses on the body.
Meeting the standards
“Guidelines in the UK suggest that the maximum weight men should lift at work is 25kg. These are guidelines, not legal limits,” say Beckett and Co, solicitors who specialise in the area. “But this relates to loads held close to the body at around waist height. The recommended maximum weight is reduced to 5kg for loads being held at arm’s length or above shoulder height. The suggested maximum weight for women is 16kg for loads held at waist height. Lifting a weight below the maximum limit does not always make the load ‘safe’.”
OSHA, in on-line guidance, expresses it thus: “The difficulty with assessing risks associated with lifting is that weight alone does not determine the risk for back injury. Other factors include how often you are lifting something, whether you bend or twist while lifting, how high an object is lifted, where the origin of the lift occurs (specifically, whether it is below knuckle height), whether you hold the object away from you while lifting, and how long you lift or hold the object. Depending on these factors, an object that is safe to lift at one time can cause back problems another time.”
For that reason OSHA does not have a specific standard for the hazards related to heavy manual lifting. The National Institute for Occupational Health and Safety (NIOSH) however has developed a so-called lifting equation for calculating a recommended weight limit for one person under different conditions. The lifting equation establishes a maximum load of 51lbs (23kg) for lifting with two hands under ideal conditions, for both men and women. That figure is then adjusted to account for how often you are lifting, for twisting of your back during lifting, for the vertical distance the load is lifted, the distance of the load from your body, the distance you move while lifting the load, and how easy it is to hold onto the load.
The NIOSH mathematical model and lifting equation are however fairly technical. In practice, rather than attempt to interpret them unaided, employers might be better advised to call in expert help. In America, OSHA has programmes for small and medium-sized businesses to help prevent ergonomic-related injuries. An on-site consultation programme offers free and confidential advice in all states, with priority given to high-hazard workstations. Consultants from state agencies or universities work with employers to identify ergonomic and other workplace hazards, provide advice on compliance with OSHA standards and assist in establishing safety and health management systems.
“Litigation is not the only issue,” says Grandusky. “There are insurance claims and premiums, lost time at work, and medical expenses. And there may be a fine by OSHA for a violation on top of all that. So there are multiple reasons to ensure that you company is doing things ergonomically.”
And not all of the reasons are deterrent. There are positive incentives as well. Intelligent lifting devices do not require strong men to operate them. They can be used just as easily by the average man or by the average woman. “That at once widens the pool of available labour for your company to employ,” says Grandusky; “and in many countries sex discrimination legislation now requires you to employ men and women equally and to pay them the same rate. Intelligent lifiting devices mean that you can do exactly that. It levels the playing field: you do not have to reserve heavy-lifting jobs just for men. You can take on older workers as well as younger ones, and staff with a much wider range of physical capabilities. Any worker, regardless of age, gender or physical ability, can perform the same task at the same level of productivity. That is a gain all round,” he says.
In designing ergonomically certain considerations can help. “There are, for example, standards for handle grips,” he says. “The orientation of the grip should not require twisting of the body. The grips themselves should not chafe, so they should be of a soft, rubberised material. 90% of workers should be able to grip them comfortably. And the material it is made of should not be a heat sink, such as metal, or else the hand will get cold, so again that calls for a rubberised grip. You do not want pressure points on a handle, so we make ours to be smooth and rounded, to fit in the palm of the hand.
“It comes down to keeping your design human-centred,” he says. “We look to seek input from our customers on how they use the equipment. It is about every aspect of human interaction with the product. We focus on that.”
One aspect of human-centred design is that staff must want to use it. “If a lifting solution is perceived to slow them down, or to be more difficult to use, they will tend instead to lift the load manually. So you have to design your device to work seamlessly with the operator. At its best it is a melding of man (or woman) and machine. I get passionate about this because it directly improves the lives of the workers who use them, and it directly improves the bottom lines of their companies as well.”
Columbus McKinnon (CM) take a similar approach to their designs: “Just recently a global team of Columbus McKinnon engineers and application specialists worked with the Institute for Product Innovation at the University of Wuppertal, Germany to perform an in-depth ergonomic study,” says Sam Lotz, content marketing specialist. “We also partnered with experts in workplace ergonomics at the Ohio State University Biodynamics Group and The Spine Research Institute. When it comes to ergonomic demands of our end users, Columbus McKinnon typically looks for solutions that will improve body position and how often certain motions are repeated when using our products. We want our end users to be as comfortable as possible and are continuously innovating to do just that.”
An example of ‘human-centred design’ is CM’s Tornado 360 degree manual hoist, featured in a recent edition of this magazine. Studies of how customers actually used lever hoists showed that, unexpectedly, many used them horizontally, for pulling, rather than vertically for lifting. The Tornado was engineered accordingly, with a new ‘Sidewinder’ lever handle, which gives a safer and more ergonomic operator position and which reduces the repetitive wrist action typically experienced with traditional hoists. Double reduction gearing and high-quality bearings reduce the required pull for by up to 30%, again resulting in less operator strain.
Similarly, CM’s Unified Industries (UII) brand overhead material handling systems are designed, they say, specifically with worker safety and ergonomics in mind. “UII’s rail systems and hardware provide less than one percent rolling resistance when manually moving a load from one workstation to another. That allows, for example, a 1,000lb load (45kg) to be moved with only 10lbs (4.5kg) of force, which results in much less strain on the operator’s shoulders and back.” Pneumatic balancers, servo systems, articulating arms, and custom ergonomic assists are all included in the system.
It is not only heavy loads that need good ergonomic design. Even keyboards, push-buttons and hand and finger movements call for it. An obvious fact about the workings of the human body that is overlooked far too often, according to lefthanders at least, is that around ten percent of the world’s population is left-handed. Left-handers frequently complain, with some justification, that they are ignored in the design of both everyday and specialist tools. Scissors and can-openers are overwhelmingly for right-hand-use only. It is just as true in the work-place.
Columbus McKinnon however have taken steps for left-handers. “One trend our research has shown is in ergonomic wireless control, which has resulted in a pistol grip style transmitter design, our Magnetek brand PGT radio remote control,” says Lotz. “With this design the operator’s thumb works in a natural position to use the rotational devices on the transmitter face. These radio remote controls have been designed to be ‘hand independent’, meaning an operator will be comfortable no matter which is their dominant hand.”
“Ergonomic design to reduce strain for operators has been an interest for Kito, and one that we are much aware of in our daily R&D activities,” says Kito’s Tsuyoshi Oshita. “For manual hoists, a very good example of how that translates to our products is our new 1t CX hoist. The key concept of this product is to be compact and lightweight: the hoist is designed to be pocket-sized—the size of a beer coaster— and light enough to be carried by the fitter whenever repair work is needed and he has to carry the unit with him. So we made efforts to downsize the load-chain and related parts—efforts that resulted in successfully downsizing the diameter of hand-chain as well. That makes the chain easier to grasp, reducing the likelihood of hand discomfort or pain; and the lighter components helps the operator use less force to lift the load.
“For electric chain hoists, we have developed our ED series. It is mainly used in handling technology. It has a cylindrical handgrip that allows onehanded operation. If you watch an operator working with it, you see that the movement of the operator’s body parallels the movement of the load. This we believe makes the operator feel most natural while he or she controls the lifting or lowering process, and is an important point of difference from other products. An adjustable dual-speed function allows the operator to adjust the lifting speed in accordance with the feel of the hand-grip, which helps give maximum control of the hoist and load with a minimum of effort. While one hand operated the control, the other steadies the load. For ergonomic reasons, its lifting height is limited to 1.8m. That is the greatest height that most people can easily reach.
“The ED series is particularly convenient for repetitive transport procedures.”
HBC-Radiomatic, makers of control systems, are equally concerned. “Even in a digitalised work environment, we assume that human beings are essential for handling complex control tasks,” says their head of marketing Oliver Meister. “The purpose of ergonomic and intuitive operating concepts is to optimise the radio control as a work tool so the operator is able to control the machine for a long time without getting tired or risking their health.
“When developing new products, we have always placed great importance on ergonomic design; as part of that we consider the weight of our controls.
“For example, we were able to unburden the operator even more by redesigning our joysticks, and this pays off when they are used for hours every day. The same applies to new ergonomic carrying options and bags which facilitate handling of the control considerably and thus make the operator’s life a whole lot easier.
“We place great importance on allowing the customer to select the assistance functions which best suit him or her and the application and work scenario. For example, if the operators frequently work in unfavourable lighting conditions or in darkness we are happy to recommend a radio system with an integrated flashlight and illuminated operating elements.”
Ergonomics encompassed every aspect of work, from the chairs and desks and lighting conditions of keyboard operators to the ladders and levers and of hoist and crane operators. It is an essential part of overall health and safety; so it is a subject to be taken seriously.