Employees on the production floor are vulnerable to a number of injuries. Some of the most debilitating and costly of these are a result of overexertion. Back and shoulder injuries are very common to people who simply pushed or pulled too much weight too many times a day.
People who push carts across the production floor need safe pushing guidelines. Of course, every individual differs in pushing capabilities. However, it isn’t feasible to test every employee’s limits. According to Liberty Mutual Insurance:
“Studies have shown that two-thirds of low back claims from low percentage tasks (tasks capable of being performed by a small percentage of the population) can be prevented if the tasks are designed to accommodate at least 75% of the female work population.”
Therefore, when possible, use parameters that are safe for at least 75% of the female work population.
Liberty Mutual Insurance has material handling guidelines, but they are somewhat complicated. (See here for the full guide.) In this article we will summarize table 7 of the guide, which details initial forces.
The table outlines the Push Force (Draw-bar pull), handle height of pushed object, and how often a production worker can do this task. The table then indicates what percent of females can accomplish the task in the given parameters “working as hard as they [can] without straining themselves, or without becoming unusually tired, weakened, overheated, or out of breath.”
The “Push Force” or Draw-bar pull is the amount of horizontal energy in pounds required to get a cart to move forward or backwards. The Draw-bar pull requirements change with the weight on the cart, the rolling resistance of the wheels, and the floor condition that the cart rolls on.
We will only identify parameters when population numbers are close to 75% or more.
The first time the table indicates a safe push/pull force for about 75% of the female work population is at 58 pounds of Draw-bar pull, so we will start there. The following indicates what is safe. Basically, a production worker can push or pull the most weight fewer times during a shift, or less weight for greater number of times during a shift. The ideal handle height on most carts is 35”-53” from the floor.
58 pounds – handle height 35-53 inches high, one push every 8 hours
55 pounds – handle height 35-53 inches high, one push every 30 minutes
52 pounds – handle height 35-53 inches high, one push every 5 minutes
46 pounds – handle height 35-53 inches high, one push every 1 minute.
At 34 pounds of “Draw-bar pull”, all parameters are safe for 75% or more of the female working population.
If, according to the guidelines above, your job is too strenuous for most of the female working population, the safest thing to do is get mechanical help. The absolute best equipment for pushing and pulling tasks is the Load Mover electric powered tugs.
These walk-behind, battery-operated cart pushers handle the work of several people. They are used to overcome both initial and sustained forces. One person can move production material throughout an entire shift without strain. The equipment is ergonomic, safe, and compact. You are likely to find the productivity also increases by using a power tug.
The team at Load Mover Inc. will help you determine your draw-bar pull to select the right unit for your needs. They can also identify other ways that your unit can save you time, money, and energy. Contact them today to discuss your needs: 952-767-1720 or Info@loadmoverinc.com.