Manufacturing employers must be on the lookout for awkward postures, forceful exertion and repetitive motion among their workforce
Two hundred and fifty manufacturing workers at Durabuilt Windows & Doors start each shift by marching on the spot. Then they do a bit of hopping
followed by arm, hip, knee and wrist rotations. Next is the stretch routine: neck; shoulders and arms; forearms and wrists; chest; calves; thighs; inner thighs; and lower back.
“Since we are starting at 6 a.m., definitely people will be half awake. They will be in sleeping mode. Who knows whether they have gone to bed at the right time or they are getting sufficient seven hours sleep or not; it’s just a wake-up call for them. They are tuning the body to work,” says Zybin Christy, health, safety and environment co-ordinator at Durabuilt Windows & Doors in Edmonton.
This program, called Durabodies, is very important in preventing musculoskeletal injuries (MSIs) and repetitive strain injuries (RSIs) caused by manual material handling at the company. At Durabuilt, 70 per cent of the work is done manually.
Manual material handling — which includes lifting, lowering, pushing, pulling, holding and carrying — is a top concern in manufacturing. It is one of the main contributors to workplace injuries in the industry.
“They’re handling everything from large pieces of equipment to boxes and every manufacturing environment tends to have some shipping, receiving, packaging type department where (manual material handling) tends to be an employee’s main role,” says Marnie Downey, president of ERGO Consulting in Barrie, Ont. “That is probably their number 1 risk.”
Back injury is a top concern for these workers. Three in four Canadians whose job includes manual material handling suffer pain due to back injury at some time. These back injuries account for about one-third of all lost work and more than one-third of all compensation costs, according to the Canadian Centre for Occupational Health and Safety.
Manufacturing workers can also experience shoulder injuries and aggravation to the upper limbs and spine, especially if heavy objects are being lifted. The risk factors of manual material handling can be divided into three categories: Forceful exertion, awkward posture and repetitive motion.
Force is the amount of muscular effort expended to perform work. Overexertion — which occurs when a worker is pushing, pulling, lifting or carrying loads that are beyond his capabilities — has been found to be the main cause of MSIs from manual material handling, says Downey.
The ISO Standard 11228 Part 1: Lifting is commonly used to determine safe lifting limits. For example, when two-handed lifting, it says men should lift a maximum of 25 kg and women should lift a maximum of 15 kg, under ideal conditions. A variety of criteria make up “ideal conditions,” including:
• standing symmetrically
• trunk is upright
• horizontal distance to object is less than 25 cm
• lifting duration of less than one hour per day.
The limit for safe lifting decreases under non-ideal conditions.
More detailed information for lifting, lowering, pushing, pulling and carrying are provided in the widely cited Liberty Mutual Manual Material Handling Tables. The tables provide both the male and female population percentages capable of performing manual material handling tasks without overexertion, rather than maximum acceptable weights and forces.
To address forceful exertion, manufacturing employers should consider the weight, shape and orientation of the object being handled.
“Can they make it in a smaller package? Does the box have to be long in the front and short on the side? Can they re-orient it?” asks Downey.
Employers also need to consider if there are any mechanical aids they can put in place. Durabuilt uses a number of mechanical aids including forklifts, overhead cranes, jip cranes, shelf trolleys, pallet jacks, engine hoists and ball tables with rollers.
One particularly interesting mechanical aid is a side cart used for moving the finished products to the shipping area.
“When the product is finished, it naturally becomes heavy… So the side cart means we can tilt those carts so that the leg will come directly beneath the product and we can tilt the product back into the cart so that no lifting is required,” says Christy.
Any posture that deviates significantly from a neutral joint position when tasks are being performed can be considered awkward.
“The more you become deviated from that, it changes mechanics in the body,” says Jack Callaghan, Canada research chair in spine biomechanics and injury prevention at the University of Waterloo in Ontario.
This means frequent twisting and reaching should be avoided.
“One of the big risk factors for shoulder injury is lifting above your shoulder,” he says. “If you can, get that job re-organized so you’re working at shoulder height or below.”
One way to address awkward postures is to make sure work stations are designed properly. Stations should allow workers to:
• handle materials as close to waist height as possible
• begin and end the handling of objects at the same height
• get closer to their work through toe cutouts in the work benches.
The work stations at Durabuilt are ergonomically designed and adjustable to the hip level of employees.
“If a person is short and the table is high, they will have shoulder injuries very frequently. If the table is short and the person is tall and the table is below hip level, there are chances that individual will come across a back injury because he has to bend,” says Christy.
When a worker performs the same motion over and over again, he can be at risk of injury. Workers should use different muscle groups and vary their posture as often as possible.
“The more frequent they have to lift, the more repetitive exposure on the spine and the higher the risk,” says Downey.
One good administrative control for this is job rotation.
At Durabuilt, for example, workers on the glass line have to manually separate and stack the glass after it is cut and tack it into the glass rack for custom windows and doors. Four employees work on this process: three of them do the stacking and one person does data entry, inputting the exact specifications for the window or door.
Data needs to be entered into the machine separately for every batch of glass sheets, so the workers rotate after each batch. They work from 7 a.m. to 3:30 p.m. and rotate their jobs throughout day.
It’s also important to make sure workers get rest in between tasks.
“If you are putting screws into frames, once you’re done that one frame, just do a slight stretching or simply massage your hand with the other hand, so you’re giving a little bit of rest and relaxing the muscles,” says Christy.
This approach is how Durabuilt has almost completely eliminated repetitive strain injuries, he says. The company has not had a single repetitive strain injury reported in the past three years.
Are your workers at risk?
There are a variety of tools available to determine what manual material handling risks your employees face. WorkSafeBC has two calculators for reference. The lift/lower calculator allows the user to input information about the task and it determines if there is a low, moderate or high risk and if controls are necessary. A push/pull/carry calculator estimates the suggested maximum force and weight based on the job and whether the operator is male or female.
Occupational health and safety professionals should conduct a risk hazard identification so they can learn where the injuries are and where they are most likely to occur. Once they know the hazards, they can identify the cause and then find a way to eliminate it.
In general, a combination of both engineering controls, such as implementing a lift assist, and administrative controls, such as training employees on how to lift better, is the most effective approach, says Downey.
No matter what solution they choose, it’s important health and safety professionals work with management and employees to come up with a suitable solution, says Callaghan.
“If you come up with a solution without looking at the workers and getting feedback on how the work is done, then the chance of your solution being successful has been shown to be pretty low,” he says. “It’s getting everybody participating in the decision, so you get buy-in.”
Internal vs. external
When it comes to manual material handling, it’s important to consider internal versus external risk factors, says Callaghan.
External factors include those that an organization can control such as the weight of the object and how the job is designed, while internal factors are how employees differ when doing a task. For example, one employee might get injured when completing a task while another worker does not, says Callaghan.
“This is where individuals need to know how to control their body,” he says. “You can have the exact same external position of loads with two people, but their internal response to how they do it, how they turn muscles on, how they control their joints can put them at very different risks.”
One of the challenges with manual material handling is training employees. It is very hard to break bad habits and when people have been lifting a certain way their entire lives, getting them to adopt a new technique is not easy. Rather than showing employees how they have to lift, a participatory training approach is more effective, says Callaghan.
“It’s almost like coaching and saying ‘How would you lift this? Why would you do it that way? What do you think the repercussions of that are?’ And getting people to buy-in,” he says. “(It’s about) raising awareness and getting people to think about how they’re doing things.”
And employees need to be properly trained on how to use the mechanical aids, otherwise they will not use them, says Downey.
Training needs to occur at a variety of levels. Supervisors need training so they can make sure they are not exposing their employees to hazards, and the joint health and safety committee should be trained on how to look for ergonomic hazards relating to manual material handling so they can spot them during their inspections, says Downey.
All employees at Durabuilt receive manual material handling training during their health and safety orientation when they are first hired.
They also receive departmental orientation that trains workers on “each and every work instruction they have on the line,” says Christy. During the first three months, employees are rotated through each section of their respective line every two weeks to get a better understanding of their tasks.
“That is considered on-the-job training,” says Christy. “There will be an assessment at the completion of the three months to assess if the individual is competent enough to perform all duties — including manually handling materials — safely.”
© Copyright Canadian Occupational Safety, HAB Press. All rights reserved.
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