While these monitoring techniques have been commonplace at many production plants for a long time, little attention has been placed on how excessive vibration af­fects workers. However, there is growing concern about the health and safety risks associated with working in, on or near highly vibrating equipment, or using hand tools that transmit severe vibrations to the person performing the work.

Considering the value of a highly trained and skilled operator and the time and effort needed to recruit and retain experienced workers, it stands to reason that methods similar to those accepted for maximizing machinery ‘health’ and productivity can and should be applied to the worker as well. To­day, real awareness of this problem is no longer limited to the medical field, but is emerging in impor­tance for those concerned with ergonomics, workplace safety and injury prevention.

What forms of vibration exposure are potentially injurious to workers? Two types of vibration are recognized as harmful to humans and regulated by various govern­ment agencies responsible for the health and safety of workers. These are Whole-body Vibration, such as that endured by workers operating heavy equipment or even fork lift trucks, and Hand-arm Vibration, commonly caused by rotating and reciprocating hand tools such as scalers, grinders, saws and nut-runners.

Whole body vibration can hasten the onset of lower back problems and exacerbate their severity, a leading cause of lost work hours, and some studies indicate it may even have negative effects on female reproduction.

Repeated exposure to vibration from hand tools causes “Raynaud’s Syndrome of Occupational Origin”, or ‘Vibration White Finger’ (VWF) disease. It is also sometimes called Hand Arm Vibration Syndrome, or HAVS.

A person with HAVS will experience spurious attacks of numbness and tingling in their digits, often while not at work. Loss of tactile acuity and fine motor control in the fingers is also common. Both hand-arm and whole body exposures have been shown to decrease the productivity and well-being of workers and in the most extreme cases, ir­reparable physical debilitation can occur. In either case, the price of vibration induced injury in both quality of life and productivity is not easy to dismiss.

Costs to the employer might seem diffi­cult to quantify if they are limited to mar­ginally decreased performance levels of their skilled labor force, but substantial financial liability in the form of increased workers’ compensation claims is very real and sur­facing in many affected industries.

What Are Safe Exposure Limits?

Recognition of the problem has led to legislation that limits the exposure of work­ers to excessive vibration levels, and these limits have been adopted worldwide, re­sulting in increased activity by safety and health professionals in performing risk as­sessments of these hazards and taking steps to mitigate the problem where necessary.

Historically it would appear less emphasis has been placed on eliminating vibration ex­posure as a source of potential injury in the US, but this may be about to change with the release of the latest revision of ANSI 2.70 (2006), “Guide for the Measurement and Evaluation of Human Vibration to Exposure of Vibration Transmitted to the Hand,” which incorporates exposure limit recommendations that are similar to those currently being enforced in the EU. In addi­tion to specifying the recommended method for measurement and data analysis, the stan­dard contains three annexes that provide guidance for vibration and health risk as­sessments, mitigating health risks, train­ing and medical surveillance related to hand-transmitted vibration. Similarly, ANSI S3.18 (2002) covers the measure­ment and related activities necessary to properly assess risk to a worker from Whole-body vibration exposures.

How to determine risk for vibration related injury and what to do about it.

Any good risk assessment program will identify work operations that have poten­tial for causing injury from high vibration levels. The commonly accepted approach is to perform baseline measurements using an instrument to determine what levels of vibration are present, much in the way noise is measured in a manufacturing or process environment.

Just like noise, the amplitude and the frequency of the vibration is very impor­tant to account for, as it is only certain fre­quencies that tend to cause physiological stress, damage and the injuries that result. Unlike noise, where it is possible to use just one sensor (a microphone) to sample the entire hazard accurately, vibration must be measured in three different directions, or axes (x,y,z) simultaneously – and until the recent development of rugged, com­pact tri-axial measuring instruments, this was not very practical in any place other than a laboratory environment.

To begin a program, it may be possible to gain some knowledge as to what various machines’ “normal” measured vibration lev­els are from the maintenance department, especially if they have a predictive mainte­nance program. This might be useful in di­recting you to some known sources of risk. But be very careful as these types of mea­surements are performed for predictive maintenance purposes and ARE NOT valid in assessing risk of injury, as they do not fo­cus on the frequencies of vibration that are proven harmful to humans.

Data from the maintenance department should only be used to identify known vi­bration generators within your facility, as a rough guide to identifying potential sources of injury. Vibration exposure measurements that are consistent with the ISO and ANSI standards for Human Vibration Exposure should then be performed, using appropri­ate instrumentation. Portable instruments de­signed expressly for gathering the correct frequency and amplitude data of the vibra­tion source have been developed and are commercially available.

Like many hazards, relatively high levels of exposure can be tolerated for short peri­ods of time, but longer and repeated expo­sures will undoubtedly cause an injury. The latest ANSI standard on Hand-arm vibration even includes a section that will predict in years when an injury from excessive vibra­tion will occur in ten percent of the work­ers, given a known level of daily exposure.

By understanding that high levels of hu­man exposure to vibration in the workplace has the potential to cause a negative out­come in the health of the workers, as well as the financial health of the organization, it is possible to perform a meaningful risk as­sessment that will uncover any possible threat to the well-being of all concerned. Science and technology in the 21st Century, understanding of the physiology and mech­anisms in which injuries can occur, and de­velopment of measurement techniques and devices that can provide useful exposure data, have given us the tools necessary to increase the productivity and ‘uptime’ of ALL components of a smoothly running production facility, human and non-human alike. FSM