A busy warehouse filled with thousands of items, buzzing with equipment and lift trucks can pose many safety risks for the employees responsible for fulfilling the orders. Keeping workers safer while maintaining a competitive operation is no easy task.
According to the Bureau of Labor Statistics:
• Musculoskeletal disorders account for 34% of the days away from work (DAFW) cases in manufacturing, with sprains, strains and tears the leading types of injuries that occur.
• Overexertion and bodily reaction rose 1,350 cases to 8310 in 2017 in warehousing and storage operations.
• Slips, trips and falls in warehousing rose 480 cases to 3030.
• Four minor level occupation groups accounted for 67% of DAFW cases in 2017, including other production workers (30,210 cases); metal and plastic workers (19,610 cases); and material moving workers (15,260 cases). The fourth group among these—assemblers and fabricators—was the only one with a decrease, down 900 DAFW cases in 2017 to 12,140.
A more recent study by Liberty Mutual reveals that workplace injuries cost U.S. companies over $1 billion per week. According to the Liberty Mutual 2019 Safety Index, the most costly causes of workplace injuries and illnesses are:
• Overexertion costs $13.11 billion
• Falls on the same level cost $10.38 billion
• Struck by object or equipment costs $5.22 billion
• Slip or trip costs $2.18 billion
• Repetitive motion injuries cost $1.59 billion.
The total cost of the most disabling workplace injuries is $55.43 billion annually.
When it comes to material handling, back injuries are one of the most common issues. Lifting and moving equipment, pallets and boxes in the warehouse can lead to fatigue and injury, primarily when the worker performs the task repeatedly for long periods.
AN ERGONOMIC STRATEGY FOR ORDER PICKING
The “golden zone” represents the pick window that corresponds to the waist level of a material handler. Typically, the range of the window begins at knee height and closes just below shoulder elevation. The belief is that this window minimizes lifting, reaching and bending motions, especially away from the recommended carry position, with the item close to the body, at waist level. This reduction in movement minimizes strain, which helps reduce the potential for injury.
While the golden zone helps workers pick items safely, it primarily is designed around improving efficiency, helping workers pick the fastest-moving items more quickly and with less effort. To optimize the benefit of the golden zone, analyze SKUs in your operation, and set the fastest moving items on shelves or carton flow lanes that reside within that window.
A typical analysis might look like the following:
Pallets: Items with a throughput of 40 cubic feet or more would stay on a pallet. The amount of handling needed negates the benefit of depalletizing to load into another system.
Shelving: Store items with a throughput of less than four cubic feet on shelves or wire decks. These are very slow-moving products that don’t require many inventory requirements but are necessary for customer satisfaction.
Dynamic Storage: These items fall between the fast movers and the slow movers and typically represent about 20% of a facility’s throughput but perhaps 80% of the effort. Store these items in a medium that increases retrieval efficiency. Examples of solutions include automated storage & retrieval systems ($$), carousels ($) and carton flow ($).
These throughputs are just a starting point and will vary by facility depending on things such as employee count, average replenishment time, overall throughput, etc.
After assigning all the items to a bucket, it’s time to begin slotting them into locations. Here’s where we start to see the power of the golden zone. By assigning the fastest moving items to locations within the golden zone, we ensure that the items that see the most action are the items that are the most optimized. There are some exceptions to the golden zone that we’ll need to address on a case by case basis, namely large items and heavy items.
Reserve the bottom levels of shelves and carton flow systems for heavy items. Heavier items need to be lifted correctly using the worker’s legs, not their back or shoulders, so the back is not strained or injured. Test the weight of the item before lifting. If you are raising a box or tote, make sure that the items inside are stable and don’t shift suddenly, throwing the worker off guard, which could lead to an injury. The recommended weight limit for safely lifting items is:
• Standing straight up, workers can lift 50 lbs. keeping it right in front of their stomach area or power zone, at about 40” above ground.
• If the worker reaches out 10 inches, the worker can safely lift between 41 and 47 lbs. before straining their backs.
• If the worker reaches out 15 inches, he/she can safely lift 35 lbs.; if they reach out 20 inches, the worker can safely lift 26 lbs., If they reach out 25”, they can safely lift 20 lbs.
It’s clear from the above guidelines that the bottom level is the best location for heavyweight items.
Large (but not heavy) items pose their challenges. Consider storing bulky items outside of a system, but if it’s necessary to include it, the top-level is usually the best spot for it. The reason is that the top-level has the most clearance. Placing a tall item on the bottom level of a storage system might require the levels above to be higher, reducing the effectiveness of the golden zone. Putting light but bulky up top is a best practice.
Brian C. Neuwirth is president of UNEX Manufacturing Inc. (www.unex.com), a provider of order picking solutions designed to maximize space usage, increase pick rates and improve ergonomics.