Solution Summary: Quieter Motor Graders
Quieter motor graders are designed to limit noise exposure from loud equipment engines by enclosing the operator or the engine or both.
Description:
Quieter motor graders use engineering controls to limit noise exposure. Motor graders use diesel engines to level or flatten earth and gravel and remove snow and these quieter machines are designed to reduce the amount of noise from the engine that reaches the operator. The sound level at the operator’s ear is reduced by insulating engine compartments and cabins and relocating noisy components of the machine.
Through the use of specially designed engine and cabin enclosures, the noise produced by the engine is mitigated and exposures are reduced. Sound pressure levels on the construction site, however, may still result in exposures above the OSHA permissible exposure limit, depending upon duration of exposure. Workers should wear hearing protection for more than intermittent visits.
Case Construction Motor Graders
| Model | Engine (horsepower) | Vehicle Weight (pounds) | Vehicle Height | Blade Width (feet) | Operator Sound Pressure Level (dBA) |
| 845B DHP | 150 | 31,812 | 10 feet, 11 inches | 12 | 75 |
| 885B DHP | 220 | 39,771 | 10 feet, 11 inches | 14 | 77 |
- Fuel: diesel
- Sound Pressure Level Prior to Re-design: 105-109 dBA
- OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA
- Noise Control Methods: re-designed engine enclosure
John Deere Motor Graders
| Model | Engine (horsepower) | Vehicle Weight (pounds) | Blade Width (feet) |
| 670G | 195 | 42,340-46,800 | 12 |
| 872G | 283 | 46,710 | 14 |
- Vehicle Height: 11 feet 2 inches
- Fuel: diesel
- Operator Sound Pressure Level: 72 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA)
- Noise Control Methods: insulated engine compartment, added isolation cabin
Caterpillar Motor Graders
| Model | Engine (horsepower) | Vehicle Weight (pounds) | Vehicle Height | Blade Width (feet) | Operator Sound Pressure Level (dBA) |
| 12M2 | 173-246 | 37,145-42,383 | 10 feet, 9.4 inches | 12 | 73 |
| 160M2 | 213-283 | 45,283-54,869 | 10 feet, 9.4 inches | 14 | 71 |
- Fuel: diesel
- Sound Pressure Level Prior to Re-design: 107-108 dBA
- OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA
- Noise Control Methods: re-designed cabin enclosure, added cabin isolation mounts, relocated hydraulic pump
Risks Addressed:
Over time, exposure to noise levels at or above 85 decibels will lead to permanent hearing loss. The NIOSH recommended exposure limit (REL) for occupational noise is 85 decibels on an A-weighted scale as an 8-hour time weighted average (U.S. Department of Health and Human Services, 1998). OSHA limits noise exposure to 90 decibels, also on an A-weighted scale and as an 8-hour time weighted average (U.S. Department of Labor). A-weighting is an adjustment that gives lower frequencies less weight or significance than higher frequencies. An A-weighted sound level more closely resembles the human ear’s response to noise.
The American Conference of Governmental Industrial Hygienists (ACGIH) assigned noise a Threshold Limit Value (TLV) of 85 dBA as an 8-hour time weighted average. Exposure to 88 dBA is limited to 4 hour, exposure to 91 dBA is limited to 2 hours, exposure to 94 dBA is limited to 1 hour and so on (ACGIH, 2012).
|
ACGIH TLVs for Noise |
||
|
|
Duration per Day |
Sound Level (dBA) |
|
Hours |
24 |
80 |
|
16 |
82 |
|
|
8 |
85 |
|
|
4 |
88 |
|
|
2 |
91 |
|
|
1 |
94 |
|
|
Minutes |
30 |
97 |
|
15 |
100 |
|
|
7.50 |
103 |
|
|
3.75 |
106 |
|
|
1.88 |
109 |
|
|
0.94 |
112 |
|
Noise exposure has also been associated with temporary hearing loss, decreased perception of noisiness and masking, increased stress, increased fatigue, disturbance of sleep and decreased concentration and mental performance (Osada, 1988). Noise-induced hearing loss starts in the higher frequencies (3,000 to 6,000 Hz) and slowly develops from chronic exposure to excessive sound. Sound must exert a shearing force on the hair cells lining the inner ear to be perceived, and if the force is too strong, cell damage and cell death can occur (Berger et al., 2003).
In a 2004 report from the University of Washington, full-shift noise dosimetry measurements indicated an average exposure of 86.4 dBA for motor grader operators (Seixas, 2004).
In a study to determine construction noise from a jobsite, different machines were monitored during normal operation. Several motor graders were tested at a distance of 25 feet (7.5 meters) while constructing a roadway. The loudest grader produced 81 dBA while the quietest grader produced 76 to 78 dBA (Minina, 2008).
Manufacturers, Case and Caterpillar, have reported sounds level of 105-109 dBA outside of their motor graders prior to redesigning them.
How Risks are Reduced:
Motor graders use diesel engines to level or flatten earth and gravel and remove snow. These quieter machines are designed to prevent noise from the engine from reaching the operator. Through the use of insulated engine compartments and cabins and placement of noisy components on the machine, the operator’s sound exposure is reduced.
While there are no published sampling data on these specific machines, safety and health experts believe and manufacturers have shown thatexposure to noise can be significantly reduced through the use of noise control techniques. The extent of the reduction is dependent on the type of work being performed, the size of the engine, the amount of noise in the environment, the level of effort required by the machine, and the operator’s proximity to the engine.
Industrial hygienists use sound level meters or noise dosimeters to determine noise levels and recommend the use of quieter techniques to prevent hearing loss and reduce the risk of accidents. Proper maintenance and retrofitting existing equipment can decrease excess sound as well (Suter, 2002).
One manufacturer, Case, states that its graders’ enclosures reduce sound levels to 75-77 dBA.
Another firm, John Deere, claims that "with a quieter cab, you can listen to tunes while working all day long."
Effects on Productivity:
Lower noise levels are expected to reduce stress and fatigue, and increase the concentration and mental performance of workers. Improved worker health, comfort and concentration may lead to greater productivity. Reduced sound levels can also lower the risk of accidents as communication among workers is easier and more effective.
Additional Considerations:
The use of diesel-powered equipment poses the risk of carbon monoxide exposure, especially in areas where airflow is reduced. Steps to control exposure are important because the gas is invisible, odorless and tasteless. Poisoning by carbon monoxide can occur quickly indoors, but working outdoors does not ensure operators won’t be overcome. Small, inexpensive personal monitors should be worn by the operator to warn of unacceptable exposures. Equipment should not be left idling to cut down on carbon monoxide and to conserve fuel.
As is the case with any construction equipment, users should follow manufacturer scheduled maintenance safety recommendations and comply with any applicable local, state or federal regulations.
Contributors:
Andrew Kingston, Michael R. Cooper and Bruce Lippy - The Lippy Group, LLC
Availability
Caterpillar 12M2 & 160M2 Motor Graders
To obtain information, visit http://www.cat.com
or contact 1-309-675-1000
John Deere 670G & 872G Motor Graders
To obtain information, visit http://www.deere.com
or contact 1-800-537-8233
Case 885B DHP & 845B DHP Motor Graders
To obtain information, visit http://www.casece.com/en_us/Pages/home.aspx
or contact 1-866-542-2736
