U.S. Department of Labor
Process: Hot Work
Hazard: Repeated Trauma
Repeated trauma injuries in hot work, are often the result of hand and arm vibration, excessive force, and inadequate recovery time when workers use pneumatic tools in association with hot work tasks. These tools (primarily hand held pneumatic grinders) are often used for removing paint or corrosion in preparation for hot work, or in dressing welds. Workers performing welding, burning, or brazing may be required to perform this type of work periodically for short or extended periods depending on the size of the job. Over time, repeated trauma disorders such as carpal tunnel syndrome, tendonitis, vibratory white finger disease, or other neurovascular disorders may develop unless employees are aware of their causes and early symptoms. These injuries are gradual in their onset and frequently workers do not report early symptoms, dismissing them as normal aches and pains. This can lead to a more severe condition requiring extensive and lengthy treatment of the injury when it is finally diagnosed, and may result in long term or permanent restrictions or disability.
A few newer models of pneumatic grinders are equipped with adjustable vibration damping handles and incorporate other design characteristics intended to reduce the effects of vibration. Anti-vibratory gloves are available which may help to reduce the problems associated with tight, static gripping as well as vibration. Defective tools that vibrate excessively should be removed from service. Workers should be encouraged to replace consumable-grinding discs frequently, as excessively worn or damaged discs contribute to vibration. One Shipyard has chosen to make the discs easily available to workers by placing "consumables cabinets" throughout the shipyard.
Alternating tasks that require the use of pneumatic tools with other work will allow for periodic recovery. For example, rather than completing all of the grinding on a large job before starting to weld, grinding and welding can be alternated to reduce the duration of the exposure to vibration. Periodically removing gloves and flexing the fingers will help to relax tense muscles that result from prolonged or forceful gripping of the tool. These simple techniques will greatly reduce the risk of repeated trauma disorders which can develop from the use of these pneumatic tools.
Welders who repeatedly use the neck muscles to flip the welding hood up or snap it down are at risk of developing a painful and potentially permanent neck injury. The force required to flip the hood can strain the neck muscles and compress the vertebrae in the upper spine. Over a period of time a musculoskeletal injury may develop. This type of injury may be avoided simply by using the hand to raise and lower the hood.
Shipyard medical personnel consider industrial hearing loss to be a repeated trauma. Noise-induced hearing loss is caused by repeated exposure to loud noise over time. The deterioration in hearing is gradual and may go unnoticed by workers until they start having difficulty communicating with others or find it hard to hear warning devices. At that point, significant permanent hearing loss has developed. Noise induced hearing loss is preventable. But once it is acquired, it is permanent and irreversible.
In shipyards the nature of the work and characteristics of the materials used often result in an extremely noisy environment. For example, use of pneumatic or impact tools on large, often hollow metal sub assemblies, hull sections, or in small enclosed areas, produce high levels of noise.
Employees performing hot work often do not think of themselves as vulnerable to noise because they are frequently moving to different work locations to perform different tasks. Also, the dynamic nature of shipyard work can result in frequent changes in noise levels.
Because of the unique nature of shipyard operations, what works best to prevent hearing loss is the consistent use of hearing protectors. In fact, most shipyards require hearing protection when working in high-noise areas and/or when using certain noisy equipment. A variety of hearing protectors should be made available to workers and they should be individually fitted with a hearing protector that is most comfortable to wear consistently. It has been shown that when workers are given an option about the type of protector to wear, they are more likely to use them. Some workers prefer the disposable foam plugs which expand in the ear to provide a snug custom fit. Others prefer the premolded flexible plug that comes in different sizes and has to be individually sized for each ear. Some of these have a cord attached to them so it doesn't get lost. Some workers may prefer ear muffs. For very loud noises, workers may be required to wear muffs and plugs together for additional hearing protection. Of most importance, the hearing protector has to be the right type of protector for each worker and the noise environment they are working in. Workers may be initially concerned that they may not be able to hear conversation, and even more so, machinery and warning sounds. That is why training on hearing protectors is so important. At training, many myths about hearing protectors will be dispelled. Workers will learn how to fit hearing protectors properly and may find that they hear better with the protectors on if they have normal hearing. Workers who have some hearing loss may find it more difficult to hear with conventional protectors, but there are specific protectors made for these situations that should be made available to them. Many shipyards place containers of earplugs at numerous locations throughout the yard, such as at the entrance to shops, break areas, or near gangways, and make earmuffs available in all tool cribs so they are easily obtainable.
Hearing tests are the only way to know for sure about one's hearing ability. There are two types of audiograms. A baseline audiogram is the first hearing test which allows for a comparison to future audiograms. The annual audiogram indicates if there are changes in hearing. Baseline and annual audiograms are enormously important and will identify early signs of hearing loss beyond those that are the result of the normal aging process. These annual checks also offer an excellent opportunity to reinforce hearing protector usage, to ensure that the worker understands the importance of hearing protection and how to use it properly. Discussing the results of the audiogram with the worker can have a tremendous impact on hearing protector usage and protecting oneself from loud noise.