Hand-arm vibrations measurements of a plastering machine

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Authors:   Eng. Potito Cordisco, Senior Project Manager, Vicoter
Eng. Mauro Terraneo, Chief Technical Officer, Vicoter

The vibrations induced on the human body from vibrating equipment can constitute a source of health risk, due to the stresses produced in the internal systems and organs. For this reason, vibrations are contemplated as a physical risk agent by the “consolidated law” on workplace safety, Italian Legislative Decree 81/2008 (in Title VIII, chapter III). Even without causing pathological effects, exposure to them can cause discomfort and disturbance in the performance of work tasks. The “Machinery Directive” 2006/42/EC requires manufacturers to quantify and declare the magnitude ​​of vibrations on their portable tools and machines.

The vibrations affecting a worker, depending on the parts of the body involved, are divided into two types: transmitted to the hand-arm system or to the whole body. The main difference between the two typologies is the frequency weighting curve to apply at the recorded data to identify the real response of the body part under investigation.

Lino Sella S.r.l. (https://www.linosella.com/it) is an Italian company producing construction machineries. Among these, we can find a plastering machines, which is designed to be operated by a single worker with the purpose to smooth the previously plastered walls in a uniform and accurate way. To be sold on the European market, this machine must respect the hand-arm vibration (HAV) regulation.

To satisfy legislative requirements, Lino Sella S.r.l. required Vicoter (www.vicoter.it) to measure the vibration levels of the plastering machinery in several working configurations and to evaluate the degree of health risk for the operators. Vicoter is an Italian company with a fifteen years’ experience in the sector of vibration measurements, performing in-situ recording of accelerations in compliance with the higher standards and using certified and cutting-edge instrumentation and methodologies.

According to current INAIL regulation (https://www.inail.it/cs/internet/home.html) in  the section “MEASUREMENT OF EXPOSURE TO THE HAND-ARM SYSTEM”, a triaxial accelerometer was placed in correspondence with each hand of the operator and, for each possible plastering machine tool, three tests were carried out, each lasting one minute. During testing, the trowel was operated at the maximum rotational speed.

Tests on Lino Sella’s plastering machine.

Measured data were processed according to the UNI EN ISO 5349 standard (parts 1 and 2), thanks to the use of the certified software Siemens-TestLabTM implementing such specific frequency weighting filter, Wh.

Hand-arm frequency response filter.

This procedure, starting from the values ​​ acquired on each single direction and applied to each measurement point, allows obtaining the RMS value of the accelerations transmitted to the hands. Comparing such levels with the thresholds dictated by the standard, it is possible to estimate the vibration risk to which a worker is subjected operating the device.

Measured values demonstrated that the tested plastering machine manufactured by Lino Sella S.r.l. induces vibrations in user hand-arm system below the limits imposed by the regulations.