"The Tire Hanger appears to be a beneficial, low cost alternative to lifting tires in the conventional manner that offers considerable reduction in injury risk as measured by the Michigan SSPP and the NIOSH lifting equation."
"...the reduction in back injury using the Tire Hanger is sizeable and lifting indexes without the Tire Hanger are unacceptably high"
"Lifting from the location of the Tire Hanger allows the workers to stand and assume an upright posture when removing the wheel, which allows the worker to get close to the load and minimize low back compressive forces."
Source: The Tire Hanger NIOSH Report
"designed to allow mechanics to hang wheels off the sides of the lift when working on brakes, hubs, etc. This places the wheels at a better height for lifting, instead of dropping the wheels to the ground. The hanger folds flat against the lift when not in use."
The Tire Hanger is referenced as an example of "Reducing Awkward Lifting/Bending - Avoid Unneccesary Lifting" on page 32 of the
State of Washington - Department of Labor and Industries
"Lifting Hazards and Some Ideas on How to Reduce Your Risk of Lifting Injury" publication.
"Use of the Tire Hanger reduces the LI and the spine compressive forces by more than one half."
"An improvement for workers performing repair activities at a service or car dealer center."
"NIOSH believes that the most effective way to prevent back injury is to implement an ergonomics program that focuses on redesigning the work environment and work tasks to reduce the hazards of lifting."
Source: The Tire Hanger Ergonomics Report
The Tire Hanger Ergonomics Report
Roy B. Starling
Tire Hanger Corporation
10604 Trademark Parkway North Suite 306
Rancho Cucamonga. CA 91730
Dear Mr. Starling:
This final report pertains to the request for Health Hazard Evaluation (HHE) that you submitted to the National Institute for Occupational Safety and Health (NIOSH) on December 19, 2001. In your request you indicated your concern for 15 workers at Honda of Oakland who may be at high risk of injuring their backs when removing wheels from vehicles to perform tire replacement or other repair services. You further requested that NIOSH evaluate the merits of a device intended to reduce manual lifting hazard known as the Tire Hanger. The Tire Hanger is a hook attached to the frame of a vehicle lift onto which the wheel is placed after it is removed from the vehicle. This allows the wheel to remain at a level convenient for the repair technician rather than locating it on the shop floor.
Back injuries account for nearly 20% of all injuries and illnesses in the workplace and cost the nation an estimated 20 to 50 billion dollars per year. NIOSH believes that the most effective way to prevent back injury is to implement an ergonomics program that focuses on redesigning the work environment and work tasks to reduce the hazards of lifting.
Pursuant to your request, I evaluated a report submitted to you by a consultant and compared the report's findings to measurements that I made at your facility on February 6, 2002. In each case the effectiveness of the Tire Hanger was evaluated using the Revised NIOSH Lifting Equation (NLE) and The University of Michigan 3D Static Strength Prediction Program(tm) (SSPP). The NLE uses task variables such as the horizontal and vertical location of an object when it is lifted, the vertical distance of the lift, the lifting frequency, and coupling and twisting factors to compute a recommended lifting weight (RWL) for the task. The ratio of the RWL to the actual weight lifted allows a lifting index (LI) to be determined. An LI of 1 or less is considered safe for most workers and a LI of 3 or more is considered hazardous for most workers. Lifting indexes between 1 and 3 indicate elevated risk of injury for workers, depending on their age, strength and other demographic factors. The Michigan SSPP uses the posture assumed during a lift and the weight of the object to calculate compressive forces on the low back as a measure of back injury risk. It also predicts the percentage of the general population that has the strength at each joint to perform the lift, e.g., elbow, shoulder, torso, hip, knee, ankle.
Referring to the consultant's report, use of the Tire Hanger reduces the LI and the spine compressive forces by more than one half.
In each case the compression forces are above the NIOSH Action Limit (AL) of 770 pounds without the Tire Hanger and below the AL when the Tire Hanger is used to lift a wheel weighing 64 pounds. In the case of the calculation for the six-foot, two-inch (6'2") individual, the NIOSH Upper Limit for compressive forces of 1430 pounds is exceeded when the Tire Hanger is not used. My calculations using the Michigan SSPP indicate that the compressive forces are reduced by about 25 percent (1033 vs.782) when the Tire Hanger is used, but that both instances are above the NIOSH AL of 770 pounds. My calculations were for a wheel weighing 46 pounds lifted by a male five feet, eight inches tall (5'8"). (The height of the individual affects the height at which the wheel is lifted from and to based on where the individual locates the vehicle vertically.) Despite the differences in weight of the wheel and stature of the worker, my results are consistent with those found by the consultant.
Compressive forces are reduced using the Tire Hanger because the posture of the worker is improved. Without the Tire Hanger, the worker must squat and bend the trunk forward to initiate the lift from the shop floor. Lifting from the location of the Tire Hanger allows the workers to stand and assume an upright posture to remove the wheel. Standing erect while lifting has the added benefit of getting closer to the load and distributing forces evenly on the low back, while bending over to lift increases the distance of the load from the body and results in uneven distribution of forces on the spine, which increases the risk of injury to the spinal discs.
My calculations also indicate that the limiting factor in lifting a wheel off of a vehicle is shoulder strength. Without the Tire Hanger, 18 percent of the general population has the required strength; with the Tire Hanger 52 percent of the population has the necessary strength capability.
Regarding the NLE, my calculations show a reduction in LI from 3.1 to 2.4 (23 percent) using the Tire Hanger and the consultant shows an average decrease of 52 percent. These differences may be due in part to the differences in the weight of the wheel and the fact that my measurements were taken under simulated task conditions from a subject who does not routinely perform the task. The consultant's measurements were made on actual workers performing actual repair activities. Nonetheless, the direction of the respective calculations are the same, and the magnitudes indicate that the Tire Hanger provides a reduction in lifting injury risk.
While the reduction in both the low back compressive forces and the reduction in injury risk as measured by the NLE are impressive, the numbers are still high when the Tire Hanger is used. In my case, a LI of 2.4 is considered high, and in the case of the consultant's calculations on the taller individual, the LI of 3.4 exceeds the hazardous lift limit of 3. Also, recall that my calculated compressive forces exceeded the 770 pound AL when the Tire Hanger was used. Moreover, a lifting task for which 48 percent of the population lacks the shoulder strength to perform cannot be considered an optimal design.
In summary, the Tire Hanger seems to be an improvement for workers performing repair activities at a service or car dealer center. The manual lifting of wheels nonetheless presents an elevated risk of low back injury to workers even when the Tire Hanger is used. As such, the industry should search for more effective ways to remove wheels from vehicles in for service, preferably one that requires no lifting by the worker at all. Such a design may incorporate lift devices that attach to the wheel and are lowered or moved out of the way mechanically.
If you have any questions regarding this report or the calculations that I made, please feel free to call me at (513) 841-4438.
Sincerely,
Daniel J. Habes
PT,CPE Ergonomics Consultant
The Tire Hanger NIOSH Report
DEPARTMENT OF HEALTH & HUMAN SERVICES
Public Health Service
This report pertains to the request for Health Hazard Evaluation (HHE) that you submitted to the National Institute for Occupational Safety and Health (NIOSH) on December 19, 2001.
In your request you indicated your concern for 15 workers at Honda of Oakland who may be at high risk of injuring their backs when removing wheels from vehicles to perform tire replacement or other repair services. You further requested that NIOSH evaluate a device intended to reduce manual lifting hazard know as the Tire Hanger. The Tire Hanger is a hook attached to the frame of a vehicle lift onto which the wheel is placed after it is removed fro the vehicle. This allows the wheel to remain at a level convenient for the repair technician rather than locating it on the shop floor.
Back injuries account for nearly 20% of all injuries and illnesses in the workplace and cost the nation an estimated 20 to 50 billion dollars per year. NIOSH believes that the most effective way to prevent back injury is to implement an ergonomics program that focuses on redesigning the work environment and work tasks to reduce the hazards of lifting.
Pursuant to your request, I evaluated a report submitted by ergonomics consultant Ira Janowitz, PT, CPE, an expert who I know and whose work I am familiar with. Mr. Janowitz evaluated the effectiveness of the Tire Hanger using the revised NIOSH lifting equation (NLE) and the University of Michigan 3D static strength prediction program. (SSPP). These are evaluation methods which I routinely use in my field evaluations and which are accepted as valid by other practitioners in the ergonomics field. The NLE, first adopted in 1981, uses task variables such as the horizontal and vertical location of an object when it is lifted, the vertical distance to the lift, the lifting frequency, and coupling and twisting factors to compute a recommended weight limit (RWL) for the task. The ratio of the RWL to the actual weight lifted allows a lifting index (L1) to be determined. An L1 of 1 or less is considered safe for most workers and a LI of 3 or more is considered hazardous for most workers. Lifting indexes between 1 and 3 indicate elevated risk of injury for workers, depending on their age, strength, and other demographic factors. The Michigan SSPP uses the posture assumed during a lift and the weight of the object to calculate compressive forces on the low back as a measure of back injury risk. It can also be used to predict the lift, e.g., elbow, shoulder, torso, hip, knee and ankle.
I spoke with Mr. Janowitz before reviewing his report and confirmed that he correctly made the measurements needed to use the NLE and the SSPP. I concur with the results he found. that use of the Tire Hanger reduces the L1 and spine compressive forces by more than half. In each case the compressive forces are above the NIOSH Action Limit (AL) of 770 pounds. Without the Tire Hanger and below the AL when the Tire Hanger is used to lift a wheel weighing 64 pounds. Moreover, as regards the case of the calculations for the six-foot, two-inch (6'2") individual, and the NIOSH upper limit for compressive forces of 1430 pounds id exceeded when the Tire Hanger is not used. Compressive forces are reduced using the Tire Hanger because the posture of the worker is improved. Without the Tire Hanger the worker must squat and bend the trunk forward to initiate the lift from the shop floor. Lifting from the location of the Tire Hanger allows the workers to stand and assume an upright posture when removing the wheel, which allows the worker to get close to the load and minimize low back compressive forces. Standing erect while lifting has the added benefit of distributing forces evenly on the low back. Bending over to lift increases the distance of the load from the body and results in uneven distribution of forces on the spine, which increases the risk of injury to the spinal disks.
Regarding the NLE, Mr. Janowitz's calculations show a reduction in lifting index from 6.3 to 2.5 for the 5'2" worker and from 6.15 to 3.4 for the 6'2" worker when the Tire Hanger is used. While the reduction in back injury using the Tire Hanger is sizeable and lifting indexes without the Tire Hanger are unacceptably high, these lifts continue to present a greater risk of injury to the worker than what NIOSH would generally recommend for an unassisted lifting task.
In summary, the Tire Hanger appears to be a beneficial, low cost alternative to lifting tires in the conventional manner that offers considerable reduction in injury risk as measured by the Michigan SSPP and the NIOSH lifting equation.
Long term injury rates of workers in this job will be the ultimate proof of the effectiveness of the Tire Hanger. However since NIOSH continues to recommend that unassisted lifting jobs have a lifting index of 1 or near 1 to insure the safety of nearly all workers, both the Tire Hanger Corporation and the industry at large should continue to look for even more effective ways to remove wheels from vehicles in service so that a method might be employed wherein the worker is required to do no lifting at all. Such a design might incorporate lift devices that attach to the wheel and are lowered or moved out of the way mechanically.
Good luck with your endeavors to reduce the risk of injury for workers performing this important service task. If you have any questions regarding this report or the conclusion that I made please feel free to call me at (513) 841-4438
This letter constitutes the final report for this HHE. To comply with NIOSH regulations regarding informing employees (CFT title42, Part 85.11) this letter should be posted in a prominent place accessible to all employees for a period of 30 calendar days.
Sincerely Yours,
Daniel J. Habes
Industrial Engineer
Industrial Hygiene Section
Hazards Evaluation and Technical Assistance Branch
Division of Surveillance, Hazard Evaluations and Field Studies