Tying rebar with pliers or with a manual tying tool can be backbreaking work. Two recent studies document the advantages of rebar tying tools. While these studies focus on battery-powered tools, spring-return manual tying tools could provide workers with some of the same advantages.
NIOSH. The National Institute for Occupational Safety and Health evaluated the risk of workers developing back and wrist disorders from tying rebar both manually and using a battery powered tier (BPT). To accomplish this, investigators measured the posture of workers' wrists and lower back when tying rebar with wire using one of three techniques: 1) pliers, 2) a battery powered tier (BPT), and 3) the battery powered tier with an extension handle (BPT+E).
They found the following:
- Manually tying rebar with pliers involves rapid and repetitive hand and forearm movements associated with increased risk of developing a hand, wrist, or elbow disorder.
- Using the extension handle with the BPT requires the least deep forward bending.
- The risk for developing a hand and wrist musculoskeletal disorder was reduced when the BPT or BPT+E is used.
NIOSH's recommendations from this study are:
- Managers should minimize the frequency and time employees spend manually tying rebar using pliers.
- BPTs should be provided to employees when they tie rebar more than one hour per day, and an extension handle should be provided for ground level tying.
- Managers should also provide employees with information describing the signs and symptoms of low back and hand, wrist and elbow disorders.
- Workers should minimize the time spent in deep forward bending when tying rebar with pliers and should use the BPT and the extension handle when available.
Construction Safety Association of Ontario. This report was the result of a study undertaken to “determine the potential reduction in the risk of musculoskeletal injuries to rodworkers when using an automatic rebar tying machine, and to determine the efficacy of the rebar tying machine as a rehabilitation device for the purpose of assisting injured workers in an early return-to-work program.” These investigators found that tying with the rebar tying machine exposed workers to significantly lower wrist activities than was experienced when tying with pliers, that the rebar-tying machine significantly decreased peak loading in the lower back, and that the cumulative loading on the back was significantly less than during manual tying.
This report concludes with the following recommendations:
- Choose a rebar tying machine that allows tying steel rebar at a comfortable back posture. An adjustable extension arm helps to ensure that rodworkers of different heights can tie rebar in a neutral trunk posture.
- The rebar tying machine should not be limited to rodwork. The machine can be used to tie electrical conduit and radiant heat tubes and decrease the risk of musculoskeletal injuries to electricians and heating tube installers. Furthermore, field experience has shown that the rebar tying machine can significantly decrease the time to tie rebar, which in turn can improve productivity.
- Select a rebar tying machine that can tie a variety of rebar sizes.
- For slab-on-grade rebar, tying rebar with the machine will require the use of a lightweight steel hook to lift rebar off the ground.
- Working with the rebar tying machine is very productive for a crew of four to five workers per site. One worker can use the machine to tie, while two others handle and place rods, and the fourth directs.
- When purchasing a rebar tying machine, select a vendor that will provide on-going support and can provide regular maintenance.
- Use the rebar tying machine to assist workers who have a lower back or hand injury to return to work. The tying machine can accommodate injured workers because the machine can be used with only one hand, and the extension arm is adjustable.