SAE 2000-01-3403 Bus Maintenance Ergonomics.docx

SAE TECHNICALPAPER SERIES2000-01-3403Bus Maintenance ErgonomicsKevin QuaidAon Ergonomic Servicesq The Engineering SocietyLand Sea Air and SpaceINTERNATIONALq The Engineering SocietyLand Sea Air and SpaceINTERNATIONALReprinted From: Ergonomics, Work Station, and Driverissues (SP-1570)Truck and Bus Meeting and ExpositionPortland, Oregon December 4-6,2000The appearance of this ISSN code at the bottom of this page indicates SAEs consent that copies of the paper may be made for personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay a $7.00 per article copy fee through the Copyright Clearance Center, Inc. Operations Center, 222 Rosewood Drive, Danvers, MA 01923 for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. 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For permission to publish this paper in full or in part, contact the SAE Publications Group.Persons wishing to submit papers to be considered for presentation or publication through SAE should send the manuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE.Printed in USACopyright 2000 Society of Automotive Engineers, Inc.ABSTRACTThis paper presents the results of achieving compliance with established and proposed Occupational Safety and Health Administration (OSHA) rulemaking, reducing musculoskeletal disorders (MSDs), and improving efficiency for rail and bus transportation providers by implementing an organizational-wide ergonomics program. Specifically, potential hazards affecting bus mechanics are identified, and methods to reduce exposure are detailed.INTRODUCTIONTraditionally, ergonomics has been a reactive approach to manage costs and risks associated with heavy equipment manufacturing, including trucks, buses, and automobiles. More recently, manufacturers have initiated formal, proactive processes to incorporate ergonomic principles in the design of vehicles, addressing both their manufacturability (plant-level) and their eventual use by drivers on the road (operator-level).However, another portion of the vehicle lifecycle has been largely ignored: maintenance. This paper explores various exposures among bus maintenance operations, operations that involve tasks common to all vehicles.The findings reflect observations and further analysis of operations performed by maintenance employees of a regional bus system that provides service to more than 100 million riders annually. This system features garages built in the early 1900*s, as well as modern facilities providing ducts for bus exhaust, bus washes, pits for servicing vehicles, and retractable overhead hoses for fluids and compressed air. Operations include routine maintenance, heavy vehicle overhaul, wheelchair lift maintenance, bodywork (interior and exterior), and seat repair/replacement.Bus Maintenance ErgonomicsKevin QuaidAon Ergonomic ServicesPARTS HANDLINGCART HEIGHT -muscles during parts handling. These forcefulexertionsintensify as the load of the part increases. Height-adjustable carts allow employees to raise or lower materialsasnecessary to achievebrake shoes and other parts from carts below knee heightinvariablyinvolves torso bending, stressing the back muscles and intervertebral discs. Parts stored on carts above shoulder height stress the relatively weak shouldera proper lifting height. These carts often feature a foot pedal for hydraulic movement, although battery-operatedcart platforms are available. In addition, these carts enable properpartsplacement for temporary parts storage, such as drivers* seats during seat suspension maintenance tasks.CART CASTERS - Impacted cart casters increase push/pull forces necessary to move a cart. Providing regular, scheduled preventative maintenance ensurescaster integrity and reduces friction from debris accumulation in the cart axles. Also, larger (6.0 or higher), harder cart casters reduce force requirements when pushing or pulling a cart within a garage. Rubber or plastic casters are preferred over steel casters due to potential for deterioration in the frequently wet shop environment. Ensuring floor integrity (such as filling large cracks or periodically resurfacing a shop floor) further reduces potential force exertions.VIBRATION - Padding tool handles or providing vibration-dampening gloves to employees who are exposed to excessive levels of vibration reduce risk ofresultantneurovascular injuries. Specific tool vibration characteristics can beCART DESIGN - Situating parts close to an employee reduces potential reaching and bending. Also, providing handles reduces stresses to shoulders and backs during cart handling. Handles should measure 35.0-44.0, above the floor and feature 1.5 diameter handles to encourage power grip use.LIFT ASSISTS - Jib cranes and overhead hoists can be effectively used in vehicle overhaul shops to maneuver parts. Using these devices can enhance handling engine heads andassessed for many tools via the Centralized European Hand-ArmVibrationDatabase(http:umetech.niwl.se/Vibration/HAVHome.html), which can then be compared with guidelines established by International Standards Organization (ISO) and American Conference of Governmental Industrial Hygienists (ACGIH).other parts weighing more than 25 lb.TOOLSTOOL SUPPORT - Supporting heavier tools (such as a 36.5 lb. Chicago Pneumatic nutrunner) requires static arm and shoulder muscle exertions, impacting neurovascular flow. Tool balancers successfully reduce the weight of tools to be supported. Torque arms also reduce the effective tool weight, as well as limiting the resultant torque reaction when a fastener is completely threaded. ProvidingTOOL DESIGN - Short, narrow tool handles stress hand tissues and do not effectively take advantage of upper extremity strength. Tools should feature padded handles to reduce contact stress. Also, handles should measureat least 5.0 in length and 1.5 in diameter to encourage a power grip during tool use. Tools specific to an operation should be used, and if no ideal tool exists, a customized version can be created, suchsupport for fuel supply lines reduces the force necessary to lift and handle diesel gas nozzles. Situating these nozzles at approximately waist height in a fixture, rather than hanging them by the fuel line, positions them at a better height for fuel pumping.as an alternator insertion fixture shown here.TOOL WEIGHT - Replacing heavier tools with lighter equivalent, without sacrificing tool integrity or performance, reduces stresses to the shoulders and upper back.SLEDGEHAMMER - Repeated tool impacts result in simultaneous upper extremity (shoulders, arms, hands) tendon reactions. Replacing traditional sledgehammers with tools that feature a dead blow head (filled with sand or small metal pellets), allows some of the impact energy of each blow to be absorbed,thus transmitting less impact energy to the bones, ligaments, and tendons.PARTS STORAGEWORKSTATION DESIGNWORK SURFACES - Working on benches or tables thatare positioned too low results in forward bending, and working on surfaces that are too high results in shoulder elevation. Employees frequently work from the floor due to inadequate workbenches. AnPALLETS - Retrieving parts from pallets located on the floor invariably involves torso bending as the stack lowers. Pallet positioners/levelers maintain parts and other products at a consistent height during receive/unpack tasks,reducingemployees height and the part that is being worked on, in addition to the work surface height, dictate the employees posturing. Sufficient work surfaces should be provided so that employees do not need to work on the floor. Providing height-adjustable worktables would allow employees to access parts without bending or reaching, regardless of thebending associated with accessing products at the bottom of a case or pallet. Positioning the load leveler so product is accessed at approximately 36, corresponding with a 95” males standing wrist height and a 5lh%femalesstanding elbowinherent shape/height of the product or the height of the employee. Fixed height worktables should situate parts at approximately elbow height. Since this height varies according to each employees stature, setting this height for taller employees and providing platforms for shorter employees will ensure all can work at proper heights.height, would reduce bending and reaching. Alternatively, height-adjustable pallet jacks could be used to raise pallet height as boxes/products are accessed - encouraging neutral posturing. Batteries should be stored on platforms rather than pallets or the floor during recharging to facilitate their handling.VEHICLE HEIGHT - Frequent vehicle lift adjustmentswillhelpensureemployees work on a vehicle at appropriate heights, particularly lower portions of a bus, such as wheelchair lifts. Platforms, step stools, and squat seats can be used to enable anhe shoulders or below the waist stresses shoulder and back tissues, respectively. Larger, heavier, and frequently accessed parts should be located in the Strike Zone (between a tall employees standing hand height - 36”, andemployee to access portions of a bus without bending or reaching. Also, during garage renovation or new construction, vehicle pits should be considered to facilitate accessing the higher portions of a bus for such tasks as window replacement and roof painting.a short employees shoulder height - 48”)to achieve proper posturing. Only lighter and low- use products should be placed outside this height range. Training employees to crouch, rather than bend at the waist, when accessing products on lowershelves, would reduce low back muscle exertions and spinal disc pressures. Limiting rack depth and refacing parts will help ensure items are located close to an aisle, reducing reaching and bending to access them deep within a rack.TASK DESIGNWORK PRACTICES - Organizing maintenance functions in a logical order to minimize parts handling effectively reduces stresses while enhancing efficiency.TRAINING - Employees should be trained to use properbody mechanics when lifting parts or other materials.Thesetechniques include keeping a load close to the torso, keeping the spinal curve intact throughout a lift, and avoiding twisting postures. Employees should also be trained and monitored to ensure that supplied tools, such as mechanical lift assists, are used whenever possible. Finally, new hires and recently transferred employees should receive on-the-job training from other mechanics or machinists to ensure that best practices are effectively passed on.ENVIRONMENTALFLOOR SURFACES - Accumulation of oil and other fluid spills can create slip hazards. Regular, scheduled cleaning via detergents, high-pressure water, or steam help reduce accumulation of these slippery surfaces. Impregnating floor surfaces with sand or other frictional grit further reduces slip potential. Finally, providing shoes that incorporate a slip-resistant sole would further reduce the likelihood of these types of incidents.FOOT SUPPORT - Standing for prolonged periods on hard surfaces stresses leg and back tissues. Informing employees about proper foot care, stretching leg and back muscles before and after work activities, and the value of footwear with proper arch support, would reduce stresses from standing. Neoprene or visco-elastic shoe inserts are also an option to reduce static leg and low back exertions.Alternatively, shockabsorbent matting can be used to reduce leg and back stress. However, anti-fatigue matting often collects oil and other debris, hampering housekeeping activities. Portable sit/stand stools may be an option for some stationary tasks to reduce static leg and back muscle exertions.PPEFIT - PPE may interfere with ergonomics when protecting against cuts, abrasions, heat, or other hazards. Also, braces that limit a motion (e.g. wrist extension) may actually create a risk if the underlying root causes of the motion are not addressed.Supplied PPE should fit all employees, with provision for both small and large employees. Wrist splints, back belts, and other braces should only be worn with a prescription by a physical therapist or other health care provider. Kneepads or kneeling pads should be provided for mechanics and employees performing bodywork that may involve kneeling.CONCLUSIONInjuries and inefficiencies associated with bus maintenance tasks are anticipated to be greatly reduced by implementing ergonomics, as detailed in this paper.ACKNOWLEDGMENTSThe author appreciates the support of the Office of Risk Management at the Washington Metropolitan Area Transit Authority as well as the Office of Safety at King County/METRO for assistance in this project.CONTACTKevin Quaid has spent over seven years providing ergonomics, safety, and project management services for companies within a wide array of industries since receiving his M.S. in Industrial and Operations Engineering from the University of Michigan and B.S. in Industrial Engineering from the University of Illinois.Mr. Quaid is a board-Certified Professional Ergonomist (CPE) and board-Certified Safety Professional (CSP), and has been active in the Human Factors & Ergonomics Society and American Society of Safety Engineers. He can be reached via email (kevin_quaid) or phone (206-749-4934).REFERENCESAmerican Conference of Governmental Industrial Hygienists: 2000 Threshold Limit Values for Chemical Substances and Physical Agents, 2000.1. American National Standards Institute: ANSI B11 TR 1-1993 Ergonomic Guidelines for the Design, Installation and Use of Machine Tools, 1993.2. American National Standards Institute: ANSI S3.34- 1986 Guide for the Measurement and Evaluation of Human Exposure to Vibration Transmitted to the Hand, 1997.3. Hilderbrandt, V., P. Bongers, J. Dul, F. van Dijk,and H. Kemper: Identification of High-Risk Groups among Maintenance Workers in a Steel Company, Ergonomics 39:2, 232-243, 1996.4. Lewis, D.: Help Workers Choose the Right Tools for the Job, Safety & Health 157:5, 40-44,1998.5. Peebles, L. and B. Norris: Adultdata - The Handbook of Adult Anthropometric and Strength Measurements, 1995.6. Ray, P.S., R.G. Batson, W.H.Weamf, Q. Wan, G.S. Sorock, J. Matz, and J. Cotnam: Impact of Maintenance Function on Plant Safety, Professional Safety 45:8, 45-52, 2000.DEFINITIONS, ACRONYMS, ABBREVIATIONSAdministrative Control: Changes in the way that work in a job is assigned or scheduled that reduce the magnitude, frequency or duration of exposure to MSD risk factors. Examples of administrative controls for MSD risk factors include job rotation, break scheduling and approved changes in work pace.Engineering Control: Physical changes that eliminate or materially reduce the presence of MSD risk factors. Examples of engineering controls for MSD risk factors include changing, modifying or redesigning workstations, tools, equipment, materials or work processes.Ergonomics: Approach of fitting jobs to people. Ergonomics encompasses the body of knowledge about physical abilities and limitations, as well as other human characteristics that are relevant to job design. Ergonomic design is the application of this body of knowledge to the design of the workplace for safe and efficient use by employees.MSDs: Work-related musculoskeletal disorders (MSDs) are injuries and disorders of the muscles, nerves, tendons, ligaments, joints, cartilage and spinal discs. MSDs are also called Repetitive Motion Injuries (RMIs) or Cumulative Trauma Disorders (CTDs). Exposure to physical work activities and conditions that involve risk factors may cause or contribute to MSDs. MSDs do not include injuries caused by slips, trips, falls, or other similarly acute incidents. Possible MSDs include carpal tunnel syndrome, epicondylitis, tendonitis and spinal disc herniation.MSD Risk Factors: Elements of work tasks that must be considered in causing or contributing to an MSD. Jobs that have multiple risk factors have a greater likelihood of causing or contributing to MSDs, depending on the duration, frequency and magnitude of employee exposure to each risk factor, or to a combination of them. MSD risk factors are also called risk factors and stressors. Research has demonstrated force, posture, static exertion, contact stress and vibration as potential MSD risk factors. Duration and repetition exacerbate the effects of exposure to these risk factors. Additional nonwork related risk factors may contribute to the onset of MSD signs and symptoms including such personal factors as gender, age, obesity, weight, smoking status, pregnancy and diabetes, as well as hobbies and other activities unrelated to Authority-approved job duties.MSD Signs: Objective physical findings that an employee may be developing an MSD. Examples of possible MSD signs include decreased joint range of motion, physical deformity, decreased grip strength and loss of muscle or nerve function.MSD Symptoms: Physical indications that an employee may be developing a MSD. Symptoms can vary in severity, depending on the amount of exposure to MSD risk factors. Symptoms often appear gradually, as muscle fatigue or pain at work that disappears during rest. Symptoms usually become more severe as exposure continues (e.g., tingling continues after work ends, numbness makes it difficult to perform the job, and finally pain is so severe the employee cannot perform the job). Examples of possible MSD symptoms include numbness, burning, pain, tingling, cramping and stiffness.PPE: Personal Protective Equipment (PPE) provides an effective protective barrier between an employee and MSD risk factors. Examples of PPE are vibrationreduction gloves and kneepads. Braces and back belts are not considered PPE and should only be used by prescription from a doctor, physical therapist or other health care professional.Work Practice Controls: Changes in the way an employee performs the physical work activities of a job that reduce exposure to MSD risk factors. Work practice controls involve procedures and methods for safe work. Examples of work practice controls for MSD risk factors include training in proper work postures, training in the use of a supplied tool and approved micro breaks.