This article explores solutions and best practices for addressing strain/sprain injury hazards associated with heavy lifting and material handling in manufacturing.
Heavy lifting is a common problem in many industries. Ergonomists aim to ensure that tasks are safe for at least 75% of the population. Ergonomics assessment tools indicate that almost all lifts greater than 23 kg (or about 50 lbs) exceed the safe capacity for workers. However, the limits can be much less than 23 kg if the lift is repetitive, over shoulder height, low to the ground, far away from the body, and if the item is difficult or awkward to grip. You might not think of a 10 kg item as “heavy”, but if it is long and awkward, and lifted all day long, even this weight can be too much.
Many potential solutions address heavy lifting, but no “silver bullet” fixes every problem. Cost, workstation layout, the product being handled, the industry and worker buy-in all play a role in determining the most effective solution. Below, we’ve reviewed a few of the most common interventions for heavy lifting. In this article, I’ve added links to examples of the various types of equipment for illustration purposes. These are not endorsements – I selected the items based on the clarity of the photos on the vendor’s website, more than the features of the items themselves.
Hoist/lift-assist (example)
One effective way to reduce lifting hazards is to use dedicated lifting equipment. Overhead vacuum and hydraulic lifts, tool balancers, and semi-automated assistive devices can minimize, or practically eliminate, manual lifting. The worker still performs the work, but by operating a hoist instead of manually lifting the objects. Manufacturers of heavy equipment such as road graders or steam generators routinely use cranes to transport heavy equipment, because the material is obviously too heavy for humans to handle. But for lighter items, it can be a tougher sell.
Hoists often seem like the most obvious solution to a “heavy lifting” problem, but some challenges include:
- The cost of designing and installing this equipment can seem prohibitive. Awkward loads may require specialized end effectors to grab onto the load, and these may need custom designs.
- Hoists require space above and around the work area, and compressed air and/or electricity.
- Implementing a hoist may slow down the job, occasionally requiring more time for the same work; if the hoist is perceived as a barrier to keeping up, workers may not use the equipment. In most cases, this decrease in speed can be offset by other changes. It may be slightly slower to lift one 20 kg bag of flour with a bag hoist than to carry it on your shoulder, but if the hoist can transport heavier bags, it could have a net positive effect. And while a worker might manually handle concrete bags faster than the hoist in the morning, the hoist may win out by the end of the shift.
Pallet lifts (example)
A spring-loaded or self-levelling pallet lift (or table, or positioner) is a common intervention that reduces bending when retrieving items from a pallet. The springs compress as weight is added to the pallet, lowering the top layer of items. Conversely, as a pallet is unloaded, the pallet rises. Many models also provide the opportunity for the worker to rotate the pallet on the lift, which prevents the worker from reaching across the pallet to retrieve or place items.
The most common challenges with pallet lifts:
- Their compressed height of 6-10 inches (15-25 cm) combined with an additional 6 inches of pallet (15 cm) raises the items at the top of a full pallet.
- Spring-loaded pallet lifts require the pallets to be placed when the table is raised, which typically requires a forklift. A hydraulic lift table can be lowered with controls, but these are usually more expensive, also have a minimum collapsed height of several inches. They also require a source of power.
Adjusting workstation, conveyor, or platform height (example)
Optimizing work height is an excellent way to improve lifting conditions. This is ideally done during the design phase and can be expensive to change for an existing line.
Including an ergonomist in the design of new lines and equipment is the best way to get out in front of this kind of issue but designing adjustable workstations or platforms can also allow workers of different sizes to achieve more ideal working postures.
Reducing box size or pallet size: Likely the simplest-yet-most-difficult solution we can suggest is to look for ways to reduce the individual lift weight. If you order materials from suppliers, you may be able to order bags and boxes in smaller units; we’ve found that this often-mentioned suggestion is rarely well-received by the suppliers.
Occasionally, workers can lift smaller loads at a time, such as when transferring items from a case to a shelf. Lifting two 12 kg bags is often less risky than lifting a single 25 kg bag!
Increasing box/container size to make use of forklifts or other machinery (example)
Along the same lines, sometimes increasing the weight of the item can make a mechanical assist more practical. People might be tempted to manually lift a 24 kg item, but at 48 kg, they’ll likely prefer the hoist.
Emptying waste bins into industrial waste collection bins is another common concern; consider addressing the issue by increasing the size of the bin. Instead of using an 80-gallon garbage bag, we could use a larger bin mounted on a pump cart, or a bin that can be removed and replaced by a forklift. This would reduce how often the bins need to be emptied, and eliminate manual lifting. This type of change requires consideration of how the waste is placed into the containers, the amount of space required, and other characteristics of the waste.
Two-person lifts: Assigning two people to a heavy task ought to reduce the risk of injury. In the long run, however, this practice is less than ideal; the second person is often busy or absent, and workers may feel obliged to lift the item without help.
A two-person lift can be very awkward if the load doesn’t have handles, the ends are obstructed, or the load is unbalanced.
Mandating two-person lifts might be an acceptable interim solution, or a solution for a very occasional task, but think twice when considering it as a solution for frequent tasks, or lifts performed in isolated environments. Choosing a solution that addresses the root cause of the hazard is preferrable to a two-person lift.
Roll lifters for industrial packaging (example)
Loading rolls of packaging onto equipment is a heavy task that is common at our client facilities. Rolls can weigh 6-22 kg (or even MUCH more) and are often loaded above shoulder height.
Fortunately, this common problem has a tidy solution: dedicated roll lifting equipment. The worker slides 1-2 rolls from the pallet onto the roll handler, pushes the loaded machine to the wrapping equipment, uses the controls to raise the roll, and then pushes the roll onto the machine and affixes it properly. Some push forces are still required, but the roll lifter eliminates manual lifting. Bonus: in some cases, the roll lifter allows the worker to prepare a fresh roll before the existing roll is empty, reducing downtime by speeding up the roll change process.
Many solutions are available to address manual handling issues. Each sector has unique needs, and suppliers might cater to one more than another. Food processing and pharmaceutical industries require special consideration for sanitation, for example. The vendors vary from sector to sector, but an ergonomist can help to navigate the client to the appropriate solution.
Reminders:
- Solutions that improve comfort and ergonomics will often also improve productivity and employee engagement. Look for interventions that check all the boxes.
- Expensive equipment will almost always require cost-justification. If you need help with cost-benefit analysis for “ergo” equipment, there are a few tools available, including this new one from Ontario, and this one from Washington. If you want more help with testing your solutions and calculating project-specific estimates, join us for our fall Cost-Justification workshop.
- A workstation that is designed, from the start, to meet ergonomics design guidelines, should not cause injuries. Learn how to apply ergo design guidelines at our fall workshop.