🌿 Hand-transmitted vibration — the daily exposure A(8)

Environment PN-EN ISO 5349-1

Overview

Intensive vibration may be transmitted to the hands and arms of the operator from vibrating tools, machines or workpieces — chain saws, percussive tools, grinders with pneumatic, electric, hydraulic or combustion drive. The continuous, habitual use of such tools is associated with diseases of the blood vessels, the nerves, the bones, the joints, the muscles and the connective tissue of the hand and the forearm; the syndrome of those changes (the hand-arm vibration syndrome, HAVS) is recognised in Poland as an occupational disease and constitutes about 3 % of all the occupational diseases registered.

The standard specifies the general requirements concerning the measurement and the reporting of the exposure to hand-transmitted vibration in three perpendicular axes. It defines the frequency weighting Wh and the band-limiting filters (6.3 Hz and 1250 Hz), so that the results of the measurements should be comparable; the values obtained serve to predict adverse effects over the range of the octave bands from 8 Hz to 1000 Hz. The standard applies to periodic, random and non-periodic vibration, and provisionally also to repeated shocks; it does not specify limits of safe exposure — the admissible values are laid down by national law. The 2001 edition replaced ISO 5349:1986: the assessment was based on the vector sum of the three components instead of on the largest component, and the reference time was changed from 4 h to 8 h. Practical guidance on measurements at the workplace is contained in part 2 (PN-EN ISO 5349-2:2004), and the requirements for the apparatus — in ISO 8041.

In Poland the measurements are made on the principles of the regulation of the Minister of Health on tests and measurements of agents harmful to health in the working environment, and the result is compared with the NDN from the regulation on the maximum admissible concentrations (NDS) and the maximum admissible intensities (NDN); the regulation on health and safety at work involving exposure to noise or to vibration additionally introduces an action level.

Method principle

The basic quantity is the r.m.s. value of the acceleration of vibration frequency-weighted with the Wh filter, in m/s², measured by the method of linear integration over a time representative of the signal. The vibration is measured in the three directions x, y, z of the basicentric system associated with the handle, preferably simultaneously, on the vibrating surface as close as possible to the centre of the gripping zone. It is assumed that the vibration in each direction is equally harmful, so the assessment is based on the vector sum ahv = √(ahwx² + ahwy² + ahwz²). The daily exposure is the energy-equivalent value referred to 8 h: A(8) = ahv·√(T/T0), where T is the total daily duration of exposure and T0 = 8 h (28 800 s); with several tasks of different levels A(8) = √(1/T0·Σ ahvi²·Ti). An example from the standard: 2 m/s² for 1 h, 3.5 m/s² for 3 h and 10 m/s² for 0.5 h give A(8) = 3.4 m/s². Where only one axis has been measured, the vector sum is estimated with a multiplier of 1.0–1.7, which should be stated together with its justification.

Applications

• Measurements of hand-transmitted vibration at workplaces required by the health and safety regulations — operators of pneumatic hammers, percussive drills, grinders, chain saws, riveting hammers and impact wrenches
• The machinery, metallurgical and shipbuilding industries, forestry, stonemasonry, mining, building
• Comparison with the NDN (A(8) = 2.8 m/s², exposure ≤ 30 min: 11.2 m/s²) and with the action level of 2.5 m/s²; for young persons and pregnant women 1.0 m/s² and 4.0 m/s²
• Selection of tools and anti-vibration gloves, planning of the working time in exposure
• Documentation of the exposure in the adjudication of the hand-arm vibration syndrome as an occupational disease

Key parameters

Standard

Standard number

PN-EN ISO 5349-1:2004

Title (PL)

Drgania mechaniczne — Pomiar i wyznaczanie ekspozycji człowieka na drgania przenoszone przez kończyny górne — Część 1: Wymagania ogólne

Title (EN)

Mechanical vibration — Measurement and evaluation of human exposure to hand-transmitted vibration — Part 1: General requirements

Step-by-step procedure

1. Identification of the tasks

   Identify all the sources of vibration (tools, workpieces), the modes of operation of the tool (e.g. drilling with and without percussion), the changes of conditions (hard/soft substrate) and the interchangeable tools (discs, chisels, abrasive paper) which may significantly affect the exposure. Collect information from the workers and the manufacturers' data on the emission of vibration.

2. Organisation of the measurement

   Choose the manner: a long-duration measurement of continuous work, a long-duration measurement of intermittent work (without taking the hands away), a short-duration measurement of the individual phases, or a measurement of a fixed duration for a series of blows (riveting hammers, impact screwdrivers). Where a measurement during normal production is impossible, a simulation of the work under conditions as close as possible to the real ones is permitted.

3. Mounting of the transducers

   Mount the accelerometers rigidly on the handle as close as possible to the centre of the gripping zone, in three perpendicular axes; with side handles (e.g. angle grinders) use two positions on both sides of the palm and average them. Check the measuring channel with a calibrator before the measurements and after them.

4. Measurement

   The worker performs typical tasks with a typical grip and feed force. Average over a representative time: in total at least 1 min and at least 3 samples for each task, at different times of the day; avoid samples shorter than 8 s. Record ahwx, ahwy, ahwz separately and calculate ahv for each task.

5. Duration of exposure

   Determine the real daily time of contact of the hands with the vibrating surface for each task — with a stopwatch, with a recorder, from a recording or by sampling of the activity — and from the records of the work. The declarations of the workers usually overstate the time, because they include the breaks in the operation of the tool.

6. Calculation of A(8) and of the short-term exposure

   Calculate A(8) = √(1/T0·Σ ahvi²·Ti), stating the contributions of the individual tasks. If the total duration of exposure t ≤ 30 min, determine the short-term exposure ahv,max = the greatest of the vector sums; where t > 30 min but the individual tasks last ≤ 30 min, determine both indices.

7. Assessment and test report

   Compare A(8) with the NDN of 2.8 m/s² (action level 2.5 m/s²) and ahv,max with 11.2 m/s²; for young persons and pregnant women 1.0 and 4.0 m/s². In the test report give the axial components, the location of the transducers, the grip and feed forces, the posture of the operator and the multiplier used where fewer than three axes were measured.

Required equipment and apparatus

Health and safety (OHS)

• The measurements are made during the normal operation of the tools — the protective measures of the workplace (protection of the eyes, of the hearing, gloves) are in force also for the person making the measurement
• Lead the cables of the transducers in such a way that they do not get caught in the moving parts of the tool
• Assess very short, intensive exposures (t ≤ 30 min) by the short-term exposure — A(8) alone could understate the hazard

Frequently asked questions