Solution Summary: Quieter Dump Trucks
Quieter dump trucks are designed to limit noise exposure from loud equipment engines by enclosing the operator.
Description:
Quieter dump trucks use engineering controls to limit noise exposure. Dump trucks use powerful diesel engines to move large amounts of earth and other materials during construction or demolition. These quieter machines are designed to reduce the amount of noise from the engine that reaches the operator. The sound level in the cabin is reduced through the use of specially designed cabins.
Through the use of specially designed cabin enclosures, the noise entering the truck’s cabin is mitigated and operator exposures are reduced. Sound pressure levels on the construction site, however, may still be above the OSHA Permissible Exposure Limit and workers may need to wear hearing protection for more than intermittent visits.
Caterpillar 773G Dump Truck
- Engine: 775 horsepower diesel
- Vehicle Weight: 226,503 pounds
- Vehicle Height: 14.63 feet
- Bed Capacity: 46.41 cubic yards
- Noise Control Methods: rubber lining option, isolation cab mounts, and cab isolation
- Operator Sound Pressure Level: 76 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA)
- Outside Sound Pressure Level: 86 dBA at 15 meters (49 feet)
Caterpillar 725 Articulated Dump Truck
- Engine: 309 horsepower diesel
- Vehicle Weight: 49,075 pounds
- Vehicle Height: 12.28 feet
- Bed Capacity: 18.8 cubic yards
- Noise Control Methods: cab isolation
- Operator Sound Pressure Level: 76 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA)
Volvo A30F Articulated Dump Truck
- Engine: 357 horsepower diesel
- Vehicle Weight: 112,700 pounds
- Vehicle Height: 11 feet, 3 inches
- Bed Capacity: 22.9 cubic yards
- Noise Control Methods: rubber lining option, isolation cab mounts, and cab isolation
- Operator Sound Pressure Level: 74 dBA with the Care Cab (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA)
- Outside Sound Pressure Level: 109 dBA
Komatsu HM300-5 Articulated Dump Truck
- Engine: 332 horsepower diesel
- Vehicle Weight: 116,823 pounds
- Vehicle Height: 11 feet, 6 inches
- Bed Capacity: 22.4 cubic yards
- Noise Control Methods: integrated floor sealing and cab isolation
- Operator Sound Pressure Level: 73 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA)
John Deere 250D-II Articulated Dump Truck
- Engine: 265 horsepower diesel
- Vehicle Weight: 91,490 pounds
- Vehicle Height: 11 feet, 9 inches
- Bed Capacity: 18 cubic yards
- Noise Control Methods: cab isolation
- Operator Sound Pressure Level: 73 dBA (OSHA’s Permissible Exposure Limit for an 8-hour time-weighted average is 90 dBA)
- Outside Sound Pressure Level: 107 dBA
Risks Addressed:
Over time, exposure to noise levels at or above 85 decibels can 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).
Noise exposure has also been associated with temporary hearing loss, perception of noisiness and masking, increased stress, fatigue, disturbance of sleep, decreased concentration and decreased 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 in order to be perceived, and if the force is too strong, cell damage and cell death can occur (Berger et al., 2003).
A survey measured all of the sources of noise within a mine, including dump trucks. Most of the noise from the dump truck came from the engine and exhaust. Measurements outside of the cabin indicated the machine produced a sound pressure level of 87 to 102 dBA (Tripathy, 1999).
A study of surface mining operations reported sound pressure levels of 87.8 and 89.8 dBA outside of a dump truck when the truck was moving with a load and without a load, respectively (Pathak, 1997).
How Risks are Reduced:
These diesel-powered machines move large amounts of earth and other materials and are designed to reduce the amount noise from the engine that reaches the operator. The controls designed to reduce noise exposure vary between machines, but include vibration-absorbing cabin mounts and rubber lining. Specially designed cabin enclosures for the dump truck operator reduce the sound level at the operator’s ear.
While there are no peer-reviewed data on these specific controls, manufacturers’ evidence indicates exposure 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 machine, 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 of existing equipment can decrease excess sound as well (Suter, 2002).
John Deere claims that "With cab sound levels that are three dBA lower than their predecessors, these trucks are noticeably easier on the ears."
Volvo states that “The Care Cab features very effective sound insulation and is mounted on optimally positioned rubber pads to reduce vibration. Comfortably low internal noise level (only 74 dBA – ISO 6396) reduces fatigue to help boost operator productivity.”
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. The number of time-consuming complaints received by the vehicle owner may be reduced, thereby increasing productivity.
Additional Considerations:
Data from OSHA and the Bureau of Labor Statistics indicate that 60 to 80 deaths each year result from vehicles backing over workers. The danger is greater in industries that use larger vehicles, such as trucking, highway construction, and sanitation. There are many ways to reduce the risk of backovers. First, the need to back vehicles should be reduced to the extent possible. When backing is necessary, traffic control plans should be used to keep vehicle and people on foot separated. Vehicles can be equipped with backup alarms, cameras, and proximity sensing devices and drivers should use spotters. Workers on foot should be required to wear high-visibility clothing when they will be near moving vehicles. Drivers, spotters, and pedestrians should receive general and site-specific training on preventing backovers.
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 safety recommendations and comply with any applicable local, state or federal regulations.
Contributors:
Andrew Kingston and Michael R. Cooper - Aria Environmental, Inc.
Bruce Lippy - CPWR
Availability
Komatsu Dump Trucks
To obtain information, visit http://www.komatsuamerica.com
or contact 1-847-437-5800
Caterpillar Dump Trucks
To obtain information, visit http://www.cat.com
or contact 1-309-675-1000
Volvo Dump Trucks
To obtain information, visit http://www.volvoce.com/constructionequipment
or contact 1-828-650-2000
John Deere Dump Trucks
To obtain information, visit http://www.deere.com
or contact 1-309-765-8000
