Engineering noise control for push boats
Rio Tinto Brazil's (RTB) barging operation, Transbarge Navegaçion (TBN), is based in Asuncion, Paraguay. It uses three "pushboats" to convey loaded barges of iron ore along the Paraguay River for delivery to customers. The pushboats were constructed in the 1950s before modern regulations on noise controls were in place.
TBN has had a significant number of noise induced hearing loss (NIHL) cases over the years associated with work on the current three barge pushboats. Noise levels on the pushboats range between 98 dB(A) in the lower level of the engine room to 107 dB(A) between the engines. Crew working in the engine or generator rooms were often exposed to noise levels well above the acceptable average daily noise dose level of 85 dB(A). At these noise levels, currently available hearing protection technology cannot reduce exposures to below 82 dB(A) for the shift, our Rio Tinto target.
Consultants in engineering noise control were engaged to support TBN in identifying solutions for high noise levels. Engineering controls implemented include provision of a soundproofed control room in the engine room (with a noise level of 80 dB(A)), soundproofing of the generator room and installation of silencers at the generator outlets. TBN are also currently refurbishing two second hand boats for use, including engineering noise controls. Although hearing protection still needs to be worn during time spent in the engine room and generator room, the engineering controls reduce the time required to wear hearing protectors from full shift with exposures still above 82 dB(A) to about 50 per cent with exposures controlled to below 82. A comprehensive hearing conservation programme has been implemented that ensures effective wear of these hearing defenders.
When the 82 dB(A) target was set the tremendous challenge of noise reduction was recognised as the pushboats are essentially diesel engines inside a resounding metal drum. By a carefully designed programme of controls, TBN has demonstrated that the almost impossible can be achieved.
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