A warehouse manual on manual handling
Tuesday, May 05, 2015
For thousands of years, humans have handled cargo manually. Visitors who see ancient structures in places like Egypt and Peru are mystified by our ancestors' apparent ability to lift and move heavy materials with no mechanical aids.
In our current era of robotics and other high-tech solutions, it is easy to overlook the necessity and the importance of manual handling. Let's consider the when and the why of manual handling. Then we will look at how it is done, and finally we will look at some of the equipment options.
When and why?
When an order calls for only one or two cases, handling is manual. Broken case order selection or picking of small items is usually accomplished manually.
Some warehouse operators also offer "final mile" delivery of home appliances, furniture and other bulky items. The major challenge is not the final mile, but rather the final 100 feet. Delivery of appliances to residences, stores or offices may involve moving product up and down stairways, through narrow doors, and in and out of delivery vehicles.
In a crowded warehouse or retail stockroom, there may not be sufficient space to allow mechanical handling. Sometimes the product itself is either unpackaged or poorly packaged, and therefore it would be readily damaged with conventional forklift handling.
Sometimes a two-wheel truck is adequate, but frequently a multiwheeled conveyance is necessary. A three-position hand truck can be used either in a two-wheel position or as a four-wheel platform vehicle. Specialized dollies are used to go up and down staircases. Some hand trucks are equipped with brakes.
Good ergonomics is the business of helping people work smarter, not harder. It requires arrangement of the work so people will minimize the possibility of excess fatigue or personal injury. Ergonomics is of particular importance in manual handling, simply because the process offers a major risk of injury.
While prevention of injuries is an important motivator for good ergonomics, another important benefit is a gain in productivity. When the work is easier to perform, people are more productive. When management arranges the workplace to reduce fatigue, workers get the job done with less physical effort and therefore are able to move more pounds of cargo every day.
One way to improve ergonomics is to avoid any condition that causes a strain in manual handling. The worst strain is caused by twisting, which is particularly dangerous if it is done while lifting or handling cargo.
Minimize the situations that cause the worker to stoop to the floor or reach overhead while handling cargo. Avoid walking by positioning merchandise so that the amount of travel is minimized. Repetitive motions can cause injury, commonly called cumulative trauma disorder (CTD).
Common sense can reduce walking. If order picking is done in a "Z" pattern, the picker selects from one side of the aisle and then immediately select merchandise directly across the aisle.
Magline, Inc., a manufacturer of manual handling equipment, describes the ergonomic challenges this way: What is the difference between a weightlifter and a route driver?
- The average driver will lift at least 24,000 pounds per day.
- Weightlifters stretch before and after they lift weights, most drivers do not.
- Weightlifters give their muscles a minimum one day break to recuperate.
- Route drivers continue to use muscles, creating repetitive strain.
Within the warehouse, rotating jobs every few hours has distinct advantages. Job rotation allows workers to do different tasks and minimizes the possibility that a repetitive lifting situation could cause injury. It also allows workers to cross-train and develop new skills, and to avoid job boredom.
Jobs should be designed for microbreaks, and workers should be trained to use these breaks to plan ahead as well as to avoid fatigue.
Proper slotting is essential to improve ergonomics. Fast movers or tough-to-handle items should always be placed in the "golden zone," between the belt and shoulder height of the average worker. This eliminates stretching or bending. Control of inbound put-away is necessary to maintain the golden zone.
How it is done
Manual handling is enhanced by using equipment that makes the job easier:
- Casters may be used to make cargo easier to push or pull.
- Well-maintained bearings are an essential ingredient when wheels are used to move product.
- Hydraulics for lifting may be employed in manual pallet movers.
- Well-designed dock boards are essential to move product in and out of delivery trucks.
- Other hardware is designed to facilitate product movement on a staircase or over curbs.
Specifications for truck ramps are critical when deliveries are made at locations that do not have truck docks. Some mechanized systems still involve manual handling at the end of the operation.
For example, a carousel will bring the parts bin directly to the order selector, but manual handling is involved in retrieving the parts and placing them in another container. Broken case order picking may use mechanized systems up to a point, but manual handling is involved in pulling the individual units from the case. Bin shelving and modular storage drawers are primarily designed for manual handling. A typical gravity flow rack picking operation requires manual handling as the final step in the process.
Options in manual handling equipment
Several factors are considered in selecting hand-powered warehouse trucks:
- Weight of cargo
- Size and shape of products handled
- Condition of the floor
The quality of bearings, casters or dolly wheels is critically important when moving heavy products. A newer technology called air casters or air bearings uses compressed air as a substitute for wheeled casters. The unit load floats on a cushion of air, and the system can be used to move loads with weights up to 140,000 pounds. Vendors claim that it is ideal for manual movement of heavy, awkward or delicate products.
Manual cargo handling has always been with us and is likely to be an essential part of warehousing throughout the future. Following good ergonomic principles is absolutely critical, both for safety and productivity. While the need for manual power continues, there is a selection of hardware designed to make the process easier.
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