Performing tasks out in the field that involve awkward postures, significant exertion and repetition can put linemen at risk for musculoskeletal disorders (MSDs) and may force them to take time off of work. MSD cases accounted for 33% of all injury and illness cases in 2011, and the workers most susceptible were between the ages of 45 and 54, according to the U.S. Bureau of Labor Statistics.
At Duke Energy, the company had a three-year average of about 32%, which was close to the national average at that time. About half of the total lost work days were attributed to MSDs in the power delivery division.
For the last decade, Duke Energy has worked to improve the ergonomics of its field workforce and prevent unnecessary sprains, strains and workplace injuries. The utility first focused on the power delivery division, which includes distribution lines, transmission lines, maintenance shops, metal fabrications, automotive garages, warehouses and office administrations and then moved on to vehicle maintenance technicians and vehicle design.
Duke Energy began to identify the ergonomic risks and develop effective mitigation strategies. By researching the cause for the MSDs and then implementing certain preventive measures, the utility aimed to reduce the numbers of MSDs companywide, starting with distribution line technicians (DLTs).
The first step was to create a project team consisting of a project team lead, a craft training supervisor, a distribution line technician, a transmission line technician, an Environmental Health and Safety (EHS) professional and an ergonomist. This team worked closely with the Power Delivery EHS Council and the health and safety manager.
This team received ergonomics training to learn about the five risk factors for ergonomics-related injuries including excessive force, excessive repetition, awkward posture, contact stress and vibration. Next, this committee was tasked with reviewing data, interviewing managers and DLTs, observing the linemen in the field, collecting data and then analyzing the research.
Duke Energy first reviewed the primary risk factors for injury and then listed the basic steps to avoiding an MSD. Also, the team members observed the DLTs for signs and symptoms of MSDs and also asked them about off-the-job activities.
Next, the team studied a four-year history of ergonomic-related employee incidents including the incident description, injury/illness type, and related work task and frequency. They also referred to the Electric Power Research Institute's “Ergonomic Handbook for Overhead Distribution” and also the “Ergonomics Handbook for Underground Distribution.”
Duke Energy also listed the routinely executed work tasks, identified current line construction projects and collected data. For example, the utility looked at the object weights and area dimensions, push/pull forces, lift distances and task frequencies. The data included the videotaped work tasks and work task simulations at the operations center.
The team performed biomechanical stress analyses and relative risk ranking. This was based on the University of Michigan's three-dimensional Static Strength Prediction Program, which is based on more than 25 years of research. It compares the task demands and worker physical capability comparison, and then estimates a percentage of the population that is capable of safely performing the task. The advantage is that it could evaluate a variety of tasks, but the limitation was that it did not consider the effect of task performance over time.
The team also used the Revised Lifting Equation from the National Institute of Occupational Health and Safety, which is based on more than 20 years of research. The advantage was that it considered repetition, fatigue and coupling, but the limitation was that it could evaluate lift and lowering tasks only.
During the relative risk ranking process, the team looked at the Stress Rating, which included the percent capable of doing the task and the lifting index. The team also looked at the Exposure Degree Rating, which was based on supervisor input and field observations.
Improving Ergonomics in the Field
After identifying the top 10 ergonomic risks for its DLTs, the team developed a risk-mitigation strategy. The workers met with the EHS council chair and immediately starting implementing short-term solutions. The utility then assigned all 21 work tasks to the Best Practice Teams to develop safe and cost-effective long-term solutions.
The best practice teams consisted of three distribution line teams as well as management from Duke Energy, who kept the teams on track, ensured feasible solutions and encouraged integration between teams.
Duke implemented the strategies, and apart from a few changes in battery-operated tools, the DLTs are still following these same ergonomic work methods in the field today.
These ergonomic solutions apply to DLTs working both overhead and underground. For example, the study looked at the removal of the manhole cover, which measures 32 inches in diameter and weighs 300 lb. Instead of using a T-handled hook, DLTs were advised to rely on a leveraging tool or relying on a line trunk winch or other mechanical means. In addition, the utility took a close look at how the DLTs were bending cable for underground installations. Rather than using the force of their upper body to shape the cable to the desired angle, the DLTs now must use fabricated cable benders. The team also specified that the DLTs should only lower up to a 5-gal tool bucket into a manhole and require two workers to remove and store a 20-ft ladder on the side of the underground trucks.
For the overhead work, the DLTs used to lay down plywood sheets to protect the terrain in muddy conditions. These sheets could weigh up to 120 lb, so Duke Energy now invests in sheets made from a lighter-weight composite material that include rope handles or cutouts to facilitate handling. Another area of concern for DLTs dealt with extracting anchor rods by grabbing the top of the rod and then forcefully pulling it out of the ground. This lead to stress on the arms and shoulders. Instead, the DLTs are advised to ensure that the rod is detached from the anchor plate before removing it and also using an auger to remove the anchor. The utility also changed the work practice focused on operating boom controls to reduce strain on the hand, wrist and arm.
After implementing these solutions for the DLTs, the utility focused on fleet maintenance mechanics and partnered with the Electric Power Research Institute for a study on vehicle design. As in the DLT study, Duke Energy identified risk factors and then developed mitigation strategies.
By pinpointing ergonomic risks and coming up with a variety of solutions, Duke Energy discovered a way to minimize the MSDs for its DLTs, improve their productivity and cut down on lost time due to injuries in the field.
Jon Evans ([email protected]) is the learning services manager for Duke Energy in Charlotte, North Carolina. He is responsible for compliance training and all training needs of transmission and distribution craft employees, engineers, fleet employees, grid modernization and metering employees in the Carolinas West Region.
Top 10 Ergonomic Risks and Ergonomic Solutions
Duke Energy's ergonomics team first identified the top risks for the distribution line technicians and then came up with ways for the workers to minimize musculoskeletal disorders in the field.
Risk 1: Making conductor connections with a manual crimping tool.
Recommended solution: Replace a manual crimping tool with battery- and/or hydraulic-powered crimping tools from Huskie Tools.
Risk 2: Lifting/handling wooden crossarms that weighed 65 lb to 110 lb.
Recommended solution: Avoid unnecessary use of heavy-duty crossarms. Also, re-evaluate design standards, add a 10-ft regular crossarm for use in 10-ft applications when a heavy arm is not necessary. In addition, conduct a more detailed comparison of fir versus pine crossarms, and look at unit cost, life span, strength and availability during storm emergencies. Finally, evaluate the sling method for lifting the crossarms from ground to either bucket or pole position.
Risk 3: Cutting guy wire with ratchet guy-wire cutters.
Recommended solution: Replace ratchet cutters with battery-operated cutting tools from Huskie Tools and other vendors.
Risk 4: Cutting less than 4/0 wire with ratchet cutters.
Recommended solution: Invest in battery-operated tools.
Risk 5: Jacking, lifting and pulling conductors.
Recommended solution: Retrain linemen on ways to increase leverage. Extend the jack strap as much as possible to gain better torque. Also, change from 18-inch to 28-inch handle to improve leverage and lessen effort. Also, the DLTs were advised to pull, rather than push, the handle. They were also told to use a double strap for anything more than 80 ft of 1/0 conductor. For lifting conductors, Duke Energy installed swivel heads on all material handler bucket booms. As far as pulling conductors, Duke Energy implemented the general rule of assistance for projects greater than 50 ft of 4/0, 85 ft of 2/0, 100 ft of 2/3 and 100 ft of 6/3. The company also put winches back on one-person buckets.
Risk 6: Lifting/handling spider reels onto tension rigs/poles and guy wire bundles. Prepackaged guy wire bundles can weigh 130 lb, and spider reels weigh 180 lb.
Recommended solution: Use only mechanical means to load or unload reels onto tension rigs or poles. For loading prepackaged bundles of guy wire on trucks, workers should use only mechanical means such as a line truck, material handler, jib or forklift. Duke Energy also equipped its trucks with a mounted guy wire reel.
Risk 7: Loading and unloading the Service-Saver, which is used to provide temporary electric power to customers following a loss of service.
Recommended solution: Implement a new Service-Saver prototype across the service area. The former model weighed 225 lb, and DLTs or contractors had to roll it to the truck and then load it onto a trailer to transport it back and forth to the work site. Also, prohibit the physical lift of the machine and try to come up with a lighter-weight alternative to providing temporary electrical power to customers. In addition, the DLTs must ensure that all trucks for transporting the Service-Saver can attach a trailer with a ramp. Another ergonomic solution is to modify the transport trailer or truck to ease the loading and unloading process.
Risk 8: Installing a splicing kit and elbows.
Recommended solution: Implement a new modular elbow installer.
Risk 9: Removing/replacing manhole covers.
Recommended solution: Phase out the T-handle or J-hook tool. Instead, use a line truck wench or other mechanical means as the first choice for removing manhole covers. Also, phase in the Fulcrum bar tool where the mechanical means are not available.
Risk 10: Stepping up to the rear end of the truck and putting supplies in the crossarm storage compartment, which can be about 70 inches off the ground.
Recommended solution: Extend the crossarm storage area on the bucket trucks. Also, change the truck design for future bucket trucks to include a new crossarm storage option. Also add on an adjustable rear step to avoid the ergonomic issues related to stepping up onto the rear step of the truck. Finally, ensure that the storage compartment does not have a metal lip.
Duke Energy | www.duke-energy.com
Electric Power Research Institute | www.epri.com
Huskie Tools | www.huskietools.com