Vibrations exposure values

Table 17.1 Examples of vibration exposure values measured by HSE on work equipment...

The exposure action value (EAV) is a daily amount of vibration exposure, above which employers are required to take action to control exposure. Daily exposure action value is 2.5 m/s. ... 

Within this family of exposure functions, usually only those with even integer values of m are of interest A commonly used function is the so-called energy-equivalent vibration exposure for which F(ajf)) = aj(t) and m = r = 2 ... 

A second function, used for exposure to whole-body vibration, is the vibration dose value, VDV, for which F aJ,t)) = ajf) and m = r = 4. The function is thus ... 

These new Regulations implement European Directive Vibration Directive 2002/44/EC. They came into force in July 2005 with some transitional arrangements for the exposure limits until 2010 (2014 for WBV (whole-body vibration) exposure limit value for agriculture and forestry sectors). 

In accordance with the type of crop protection procedure, the stages of the work had different cycle times. For herbicide application, the complete task was done in approximately 18 minutes, while, in the fertilizer application was finished in only 5 minutes. Samples collection allowed us to identify the Vibration Dose Value in RMS (RMS VDV), maximum peak level (Peak), and value of daily exposure (8-hour reference period) to WBV (A(8)). EMB-201A aircraft applying herbicide, (sample = 01 36 41, n = 5792), showed RMS VDV = 8,053 m/s and Peak = 141,490 m/s. Also applying herbicide, EMB-202 aircraft (sample = 01 31 40, n = 5493), showed RMS VDV = 11,098 m/s and Peak=96,774 m/s. Finally, EMB-202 aircraft applying fertilizer (sample = 01 17 11, n = 4624) showed RMS VDV = 9,470 m/s and Peak = 120,277 m/s. Figure 1 show data points corresponding to the combined axis (X, Y and Z) Vibration Total Value (RMS VTV) for these three situations respectively. 

It is world-wide accepted that discomfort, reduced work efficiency and health impairments are problems found among professionals repeatedly exposed to Whole-Body Vibrations (WBV) (Melo Miguel, 2000 Bernardo, et al., 2014). The risk depends on its intensity and duration. Several standards define procedures for measurement and evaluation of Whole-Body Vibration (WBV), providing limit values and action levels . However, there are no studies demonstrating what is the dose of WBV that can cause any specific disorder related to the magnitude, frequency, direction and duration of vibration exposure (Griffin, 2004). 

The International Organization for Standardization (ISO) standard 2631-1, Mechanical Vibration and Shock Evaluation of Human Exposure to Whole-Body Vibration Part I General Requirements , specify how to measure and analyze WBV. Action limits and exposure limits values are presented in Table 1 (Lewis Johnson, 2012). To further evaluate transient shock vibration exposures in relation to human health, the International Organization for Standardization (ISO) published a new WBV standard, ISO 2631-5, in 2004. Long-term... 

The IR spectrum that results from dosing CF4 onto the SWNTs was measured before and after the ozone opening treatment/vacuum heating cycle. There is a vibrational frequency in the spectrum of CF4 that experiences diiferent relative shifts with respect to the values that it has in the gas phase when the CF4 molecules are adsorbed on the outside, or on the inside of the nanotubes. The shifted value of the frequency corresponding to adsorption on the interior of the nanotubes is only present on the etched nanotubes that corresponding to adsorption on the outer surface is present on both etched and nonetched tubes. (The traces corresponding to the unetched and etched spectra as a function of increased CF4 exposure are presented in Fig. 16.3.) Additionally, the intensity... 

The product of the collision-induced dissociative chemisorption event is identified by high resolution electron energy loss spectroscopy. Fig. 9a shows the vibrational spectrum of a monolayer of methane at 46 K before bombardment with Ar. The vibrational frequencies are unperturbed from the gas phase values within the resolution of this technique ( 20 cm-1). The loss observed at 1305 cm" is assigned to the V4 mode, the loss at 1550 cm- to the >2 mode and the losses at 2895 cm 1 and 3015 cm- to the vi and V3 modes, respectively. Fig. 9b shows the vibrational spectrum after exposure of the methane monolayer at 46 K to a beam of Ar atoms with a translational energy of 36 kcal/mole. This spectrum has been assigned previously to an adsorbed methyl radical. 

If there are differences in the working conditions between the component to be assessed and the one which has been observed it has to be examined to what extent these working conditions are encountered in any of the observed plants. An analysis of dependencies is helpful in this context. For example, generally reliability data of components exposed to aggressive media are worse than those to be expected in case of exposure to water. They then may serve as conservative estimates. The same is tme for cases of strong mechanical loads like, for instance, strong vibrations. Values obtained for such cases may also serve as conservative assessments for components under normal loads. 

The exposure limit value (ELV) is the maximum amount of vibration an employee may be exposed to on any single day. It represents a high risk above which employees should not be exposed. Daily ELV is 5m/s Health and safety surveillance, information and training must be provided by the employers. 

There is extensive literature on the occurrence of health effects and injury from exposure to vibration, shock, and impact, which has been reviewed recently (von Gierke et al 2002) and serves as the basis for the present discussion. Estimates of exposures necessary for common human responses and health effects are summarized in Table 10.2 for healthy adults the interested reader is directed to the references given in the table for more complete information, or to the recent review article cited. Included in Table 10.2 are the metric used for assessing the exposure, the frequency weighting of the stimidus, and a representative value for the response or health effect under consideration. As already noted, there are large variations between individuals in response, and susceptibility, to vi-bratirHi, shock, and impact. 

Risk of Injury. Exposures to vibration magnitudes between the flireshold for perception and that for health effects commonly occur in daily life. Near-daily exposures to values of nwA <8> in excess of those estimated to result in 5 to 10% injury in Table 10.2 occur in numerous occupations (involving some 8 million persons in die United States) and lead to the symptoms described in Sec. 10.1.2. 

Interrelations can be found between the perception of vibrations and the measurable vibration intensity (Figure 7.11). The intensities of perception develop along steps A through F and are characterized, in accordance with the effect of these vibrations along the Jt, y, and z axes, by the letters KX, KY, and KZ respectively KB stands for the structure related perception intensity. Characteristic control parameters for vibration are vibration path, oscillation frequency or acceleration, frequency, duration of exposure, and frequency of occurrence. So-called KB-values have been suggested as an evaluative scale for vibrations in apartments and comparable rooms, whereby these values vary, depending on the character of the area in question (strictly residential area to industrial areas), between 0.1 and 12 [7-22]. 

The source of noise and vibration on demolition sites will normally be caused by the use of plant and equipment, falling debris and/or explosives. Compressors, pneumatic hand-held tools, front end loaders, excavators and other equipment can create noise levels of more than the lower exposure action level of 80dB(A) and may at times create peak noise levels of more than 137 dB(C) the lower peak sound pressure action value. A noise assessment will be required and workers given ear defenders. 

The Control of Vibration at Work Regulations introduce, for both hand-arm and whole-body vibrations, a daily exposure limit and action values. These values are as follows ... 

An exposure limit value must not be exceeded. If an exposure action value is exceeded, then action must be taken to reduce the value. The expression A(8) is added to the exposure limit or action value to denote that it is an average value spread over an 8-hour working day. Thus the daily exposure limit value for hand-arm vibration is 5 m/s A(8). 

Since the exposure limit or action value is averaged over 8 hours, it is possible to work with higher values for a reduced exposure time. Table 17.3 shows the reduction in exposure time as the size of the vibration increases. 

The Regulations require that where there is a likelihood of WBV, the employer must undertake a risk assessment. The HSE Guidance document, L141, gives detailed advice to help with this risk assessment and on estimating daily exposure levels. Whole-body vibrations risks are low for exposures around the action value and usually only simple control measures are necessary. 

For work equipment first provided to employees for use prior to 6 July 2007 and where compliances with the exposure limit values is not possible, employers have until 2010 to comply and, in the case of agriculture and forestry, 2014 (for whole body vibration). 

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