Thursday, December 5, 2013
What Are Acceptable Ergonomic Torques for DC Electric Right Angle Tools
Even a clean and orderly workplace can produce health challenges for the employees. Repetitive motions, a lack of lumbar support and physically demanding work with poor tools are three examples of the ways environments can lead to back, shoulder or other body issues. Ergonomic awareness plays a key role in preventing possible issues. In the specific case of torque application, an informed tool selection can lead to both less body stress and an overall heightened productivity.
Torque Tool Overview
Torque tools apply a rotational motion to threaded fasteners. The tools are typical choices for tightening or removing lug nuts on automobiles or bolts during the manufacturing process. Sensors built into the tools can provide real-time measurements for the applied torque and rotation. However, use of these tools can apply forces apart from those directed toward the fasteners they are designed to tighten. When bolts are secured, the tools can jerk on user wrists or limbs before coming to a full stop. These stresses are the subject for ergonomics. Understanding the limits of both the tools and the human bodies using them will result in an informed selection of the best possible tool for the job.
Acceptable Limits
Human bodies come in a single shape with room for subtle variations. The mass of the human arm is one of the determining factors for the amount of force it can resist. Fitness is a determinant in how much force a body can tolerate. Limits still apply to all cases. Too great a level of force will result in tissue, bone or joint damage, no matter how fit the tools user. An acceptable ergonomic torque tool is determined to be those devices which cause the least amount of force to the wielder once the threaded fastener has been tightened to its limit.
Qualitatively Defining Discomfort
Through use of a tool test rig, a University of Ohio researcher investigated several styles of torque tools. He devised a method to understand the effects different tools have on the users, known as a response torque. According to his literature survey and observations, high levels of discomfort corresponded to high response torques. The research study tested specific effects by creating spring and pressure systems to represent variables such as arm stiffness, joint hardness and arm mass. With these, the study could judge how much torque different tools applied to their users. Tools demonstrated acceptable response torque ranges between 8.8 to 44.3 foot-pounds (12 to 60 Newton-meters). He tested pneumatic and electric tools with various configurations. In the end, he rated each tool with a discomfort level, which can be used to qualitatively compare each tools efficacy as an ergonomic device.
Research Study Results
DC electric-powered right angle tools received low to medium discomfort ratings. These tools operate on DC power and are constructed with a long handle, allowing easy access to hard-to-reach bolts, nuts or other joint connectors. This handle also acts like the simple tool known as a lever, using its distance component to aid the user. As with other models of torque tightening tool, such as the drill-shaped torque wrench, the right angle design produces twists or jerks to the users wrists, arms and shoulders after the fastener is tightened to the limit. However, instead of relying on a humans ability to release a trigger in a timely fashion, many right angle tools come with a computer-aided, real-time torque monitor, which can respond much more quickly.
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