Sandblasting Noise Project New Nozzle
Using the recommendations from Noise Control Engineering obtained from FY 2012 Research Projects 0857 and 6433, and the 2012 noise data obtained by a partnership with National Institute for Occupational Safety and Health, can we identify ways to reduce noise in sandblasting and metal preparation procedures with appropriate engineering controls?
Where do we focus our efforts and resources that will have the biggest impact on employee safety and health in high noise processes such as blasting and metal preparation with regard to preventing hearing loss through engineering controls for reducing noise exposure? The sand blast, surface preparation industry is very large, however much of the research and development resources are directed toward improving personal protective equipment (PPE) instead of reducing noise sources. This is a short-term approach that is driven by economics. The OSHA regulations allow short-sighted companies using sand blast equipment to protect workers through inexpensive PPE instead of the apparently more costly processes of reducing noise at the source through elimination, substitution and engineering controls. Reclamation recognizes the moral obligation to protect worker's hearing and understands the long-term benefits of eliminating noise sources and keeping all exposures as low as reasonably achievable.
Need and Benefit
Hearing loss is a key safety issue within Reclamation. Reclamation paid approximately $5.24 million dollars over the last 10 years in workers compensation for hearing loss claims. More than $2.5 million of that over the last 10 years was from the Pacific Northwest Region. Industry standards suggest indirect costs (loss of production, worker morale, etc.) may be 4-times greater than the associated direct costs.
Noise is often overlooked as a hazard because there are no obvious indicators of acute or chronic exposure. However, noise induced hearing loss (NIHL) is one of the highest workers compensation expenses agencies have for non-traumatic injuries. NIHL is preventable by reducing the noise at the source, providing effective hearing protectors, and/or by limiting frequency and duration of exposure. Reclamation dams use large steel gates and stop-logs that must be sandblasted before re-coating. Workers are exposed to extreme noise levels due to the configuration of the gates and the limitations of equipment. Occupational Safety and Health Administration requires elimination/reduction and engineering contol (if feasible) of a hazard prior to implementing administrative and personal protective equipment strategies. Short-sighted companies argue the feasibility of elimination/reduction and engineering contols and opt for apparently inexpensive personal protective equipment.
The sandblasting process is a primary high noise procedure conducted during a major powerplant overhaul and equipment rehabilitation. Industry data show a median time-weighted average (TWA) exposure for all blasting at 92 dBA with short-term exposures easily exceeding 115 dBA. Abrasive blasting with mineral grit showed 50th percentile (median) TWA exposures of 95 dBA with a 114 dBA maximum TWA. The National Institute for Occupational Safety and Health guideline for using double hearing protection, wearing both earplugs and earmuffs is for noise exposures that exceed 100 dBA over an 8-hour period. Reclamation Safety and Health Standards require dual hearing protection consisting of both insert type earplugs and muff type devices to noise exposure to 90 dBA. One challenge is fitting the required muff hearing protection within the hood typically used by sand blasters. Moral responsibility aside, sand blast noise produced by sand blasting hydropower equipment (gates and stop logs) cannot be controlled by double PPE alone. A noise elimination of a minimum of 10 dBA is needed to reduce the NIHL from exposures above the TWA.
As Reclamation moves forward in equipment rehabilitation and modernization, it is imperative that employee safety be a strong consideration. Any renovations or updated operational processes must consider impacts to employee health, including noise impacts. To ensure that employee health and safety is a solution criteria, the engineer staff must be provided with criteria for change, or a driver for change. The ONR design engineers have years of research and many resources at their disposal for large scale sandblasting and other high-noise operations research. This study will provide data to support the consideration of hazardous noise production as design criteria and will enable the engineers to focus energies toward redesign of those equipment or areas where the noises levels are the highest. The data from this study could result in new transferable technologies that could be used by all of Reclamation and all other agencies who perform large-scale sandblasting and other operations involving hazardous noise levels. This would enhance the opportunity for Reclamation to create demonstration projects and/or test new technologies that could be transferred between private and federal stakeholders.
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