Wrist mounted vibration transducers – not again!
Once more there are claims that wrist/glove mounted vibration transducers can be used to assess HAV risk in operators as per the British Standard (BS5349). No they can’t. Thank you for listening…
I would suggest that anyone considering using any of the wrist (or glove) mounted automated transducer measurement systems in an attempt to measure vibration (as against using them as tool timers linked to properly measured tool vibration levels) to assess operator exposure should consider the following before making a decision:-
- It is specifically deprecated by the HSE. Their recent guidance states: “There is currently no wrist or glove mounted device which measures vibration suitable for use in a vibration risk assessment”. Hence as wrist (or glove) mounted transducers do not measure according to ISO/BS5349, the data they produce is not related to the EAV or the ELV dose values and cannot be used for comparison with them in a risk assessment. Those are the facts. This could not be clearer…
- Carry out a simple experiment on a high vibration tool (impulsive tools in particular): measure on the tool handle as per BS5349. Measure on the wrist with the wristband loose, and again with it tight enough to cut off the blood supply to the hand. Compare with the measurement made to the standard. They are different – which means they are wrong by definition as all the risk statistics were based on tool handle measurements.
- How do you persuade the operator to move the wristband to the other hand as is necessary when using different tools/handles or when swapping the tool to the other hand? This doesn’t seem to be mentioned anywhere in the vibration monitoring system sales literature.
- The HSE specifically say that you should spend a minimum on monitoring and focus resources on risk reduction instead. This makes a lot of sense and is best practice.
A recent back-to-back vibration measurement test on 2 items of plant compared the results from BS5349 measurements (2 different personnel using 2 different meters) with those from a “leading” wrist-mounted transducer system (the latter carefully controlled in a way that probably does not reflect general use). Whilst all the BS values were within 5% of each other, the comparable wrist-mounted data varied by between 14% and 240%…
There is an IOM report that is purported to validate wrist measured vibration data. However, this is based on a statistical analysis of supplied data sets without knowledge of any potential exclusions, i.e. it is not an independent study of the validity of wrist mounted vibration monitoring. Validating alternative automated HAV monitoring wrist or glove techniques would require submission to ISO/BS committees, peer review and the extensive reevaluation of risk data, not just a limited statisical analysis carried out in isolation. Moreover, the problems associated with the laws of physics and human nature would still remain.
Now imagine you are the barrister for a HAV injury claimant. Based on the above, just how easy would you find it to drive a coach and horses through a risk management defence based on wrist-mounted vibration data capture? Potentially a very costly mistake…
The new HSE guidance on HAV measurement and management covering the increasing concerns over mis-measurement may well change the way you measure and monitor HAV risk – dramatically… We have developed a short HAV Master Class competency update workshop that covers these and other issues. Check availability and dates to ensure that you are up to date with best practice.
There is considerable deliberately disingenuous disinformation put out by some suppliers taking advantage of the technical nature of the subject to promote sales of products that do not perform as advertised. Tool timers: fine if properly set-up. Vibration dosimeters: absolutely not. In addition, the whole thrust of the wrist/glove mounted automated vibration measurement system approach is that you should spend your resources on continuous, costly logging and measurement rather than on reducing the risk. This directly contradicts HSE advice and goes against current best practice.
In its place
This type of monitoring certainly has a place in risk management – provided that you can justify the high cost. Whether it is a good choice depends on the cost v benefit for your particular circumstances. If you have spent much of your budget on monitoring, there may little left to actually reduce the risk e.g. by buying better tools instead. These monitoring systems may be OK as sophisticated tool timers used to monitor likely exposures provided properly measured tool data is used in the calculation and not the wrist/glove measurements. They can also sometimes give an indication that a tool needs to be serviced – although the operator could do that for free…
Whilst hand-held transducers are not generally recommended, they can be used in circumstances where hard-mounting a transducer would be difficult – as long as you can make sure that the transducer is very firmly held against the tool. However, the results should be treated with care as they can be significantly different to hard-mounted transducer data.
White paper: HAV mis-measurement – to no standards whatsoever… New HSE guidance
Contact us if you’d like to discuss the issues surrounding current HAV risk management best practice. More information about this white paper and a summary of the latest HSE guidance on the topic is available here>.