Measurement Hints

It is absolutely imperative that the measurement pick-up (accelerometer) is rigidly fastened to the surface of the tool handle. The very best way to do this would be to drill and tap a hole and fix the accelerometer directly; this doesn’t usually go down too well with the boss though! Failing that, fast-setting epoxy glue or jubilee clips should be used. Cable ties are a last resort and only ratchet-less ones with a tightening tool should be used if absolutely necessary.

Watch out for overload or under-range messages. An overload message will occur when the peak of a vibration waveform exceeds the capabilities of the instrument to measure (see figure 3). This leads to a loss of measurement information and therefore errors; if this occurs then the measurement must be taken again. An under-range message will occur if the actual measurement reading (rms) falls too close to the electrical noise within the instrument circuits, this also causes an error. As some percussive tools have a huge difference between the peak and rms (see figure 3) it is possible to encounter both states at the same time. This is especially true with older technology instruments.

Conclusions

The changes brought by this new set of regulations are not necessarily profound (apart from a fairly large change in the action levels!). There is, however a lot of detail and many small changes from the existing position, which require care in implementation. The guidance on regulations from the HSE should be read and digested and it may well be wise to attend a ‘Competent Person’ training course for Vibration at Work assessments.

This legislation is written from the point of view of the HSE, whose primary concern is with the protection of employees who are exposed to excessive Vibration levels. What they are not concerned with is civil litigation. In other words, as long as an employer is taking enough action in the eyes of the HSE to prevent injury to people from excessive vibration levels whilst at work, they will be happy. The problem is that this may well not be enough to mitigate any claims that come along in the future!

Further Reading

Controlling Vibration at Work – The Control of Vibration at Work Regulations 2005. HSE Books (L140) (ISBN 0-7176-6125-3). www.hsebooks.co.uk
Directive 2002/44/EC on the Minimum Health and Safety Requirements Regarding the Exposure of Workers to the Risks Arising From Physical Agents (Vibration). Available form the E.U. web site at http://europa.eu/ (type 2003/10/EC into search)