Solution Summary: Lift-assist Equipment for Masonry Unit
A lift-assist equipment for masonry unit, such as the MULE Smart Lifting, is an engineering control designed and built to handle and place heavy material on construction sites. The ground setup of this equipment can mount on mast scaffolds, a stationary ground base, or a wheel cart for portability. It also uses interchangeable grippers to secure different types of material for lifting.
Figure 1. A worker using a lift-assist equipment to lift and place a masonry block. (Photo courtesy of Construction Robotics)
The MULE Smart Lifting is a portable equipment that provides lift assist of material weighing up to 150 pounds. It is able to lift standard CMU, insulated block, veneer stone panels, retaining wall block, or any other masonry unit. Depending on material specifications, figure 2 shows a variety of interchangeable grippers that correspond to table 1 below. This equipment is also customizable for additional height. For more information, please visit the manufacturer website.
Figure 2. Grippers for the MULE. (Photo courtesy of Construction Robotics)
Table 1. Variety of grippers and specifications corresponding to figure 2. (Photo courtesy of Construction Robotics)
The dimensions and weight of the MULE will depend on its configuration. Figure 3 provides an example of the MULE in its standard configuration.
Figure 3. Classic MULE setup specifications. (Photo courtesy of Construction Robotics)
Heavy and frequent lifting and carrying during manual material handling can cause low back disorders, such as muscle strain or a disc herniation (“slipped disc”), which is bulging of disc material possibly pressing on the spinal cord or nerves that go into the leg.
Stressful upper extremity activities can also cause musculoskeletal disorders (MSDs) to the shoulders, elbows and wrists. These include muscle strains, ligament sprains, tears to the shoulder rotator cuff muscles, tendonitis, which is inflammation of the elbow and wrist tendons' and carpal tunnel syndrome, which is compression of a wrist nerve, resulting in finger numbness and loss of hand strength.
How Risks are Reduced:
A masonry unit lift-assist equipment can help reduce manual material handling by reducing the effort needed to manually handle bricks or blocks during laying operations.
A masonry unit lift-assist equipment can help reduce stressful shoulder, elbow, wrist and hand activities eliminating the need to handle bricks as it can be mechanically gripped and positioned by the robot.
While there have not been independent published studies measuring the effect of lift-assist equipment for masonry units on reducing musculoskeletal disorders, there is research evidence that spinal loads increased after the first 2 hours of lifting exposure regardless of the lift frequency (Marras et al., 2006). Regardless, safety and health experts believe that masons will be less likely to develop musculoskeletal disorders if they use ergonomic equipment to reduce heavy repetitive lifting.
The use of the MULE Smart Lifting still requires a skilled mason to butter and place brick and block but, risk is reduced by eliminating the need for the mason to repeatedly lift heavy materials.
As is the case with any construction tool and equipment, users should follow manufacturer safety recommendations and comply with any applicable local, state or federal regulations.
The robot needs a stable platform to operate. Workers should verify that the platform is rigid and meets the specification of the MULE. A collapse could be fatal if masons (loading the bricks and mortar) are working alongside the MULE.
Workers should be aware of the distance between them and the robotic systems to avoid catching and dragging-related risks.
Workers should wear appropriate clothing and PPE when working with these robots
Another possible consideration is ensuring the superintendent (or vendors - depending on who has the responsibility to set up and manage the robots) provide adequate boundaries between workers and the system.
System malfunction could lead to serious accidents. While it does not happen often, users should ensure that the system is checked regularly (based on the manufacturer's guide) by a skilled technologist/technician authorized to maintain these robots.
Jean Christophe Le, MPH - CPWR The Center for Construction Research and Training
Chuma Nnaji, Ph.D., MBA - The University of Alabama Construction Innovation Integration Lab (CII-Lab)
Jennifer Hess, Ph.D., Associate Research Professor at the Labor Education and Research Center