04 October 2017 How to reduce the risk of hand-arm vibration and reaction
Anyone who has ever used screwdrivers on an assembly line knows how important it is to employ ergonomically designed tools, which are key to operator health and safety in the workplace: such conditions are also necessary to reduce rejects and production downtime, as well as improve the quality standard of the finished product. In this article, we’ll be explaining how to reduce the risk of hand-arm vibration and reaction.
Vibration and reaction are risk factors still found in many manufacturing environments and our various customers – for whom operator health is a primary concern – have contacted us on a number of occasions to ask for exhaustive information on how to deal with these risk factors. Let’s find out more.
What causes the risk of hand-arm vibration?
Like most hand-held equipment, screwdrivers are a source of vibration. The definition of “Hand-arm vibration” (according to Italian legislation – D.Lgs 81/2008 – pay attention, this law refers to European legislation) is as follows: mechanical vibration that, when transmitted into an individual’s hands and arms, can lead to a health and safety risk for workers, especially vascular, osteoarticular, neurological and/or muscular disorders. This class of risk is often referred to by its acronym, HAV.
The most common effects of exposure to vibrations for the hand-arm system can be attributed to vascular or neurological lesions that result in the progressive loss of sensitivity in one of more fingers.
Solutions to hand-arm vibration risk
To reduce the risk of hand-arm vibrations, you can opt for screwdrivers with automatic air or power shut-off, which have vibration levels of less than 2,5 m/s2, which is the limit established by Italian law (D.Lgs 81/2008, art. 201).
How do they work? These screwdrivers shut off the supply air to the air motor or, in the case of electric tools, shut-off the electric feed, when they reach a preset torque.
It’s worth remembering that the use of a technologically cutting-edge automatic shutoff clutch can reduce vibration levels to well below 1 m/s2 under certain conditions: we should point out that, in addition to reducing the source of vibrations, exposure time is also much lower, roughly four times less, for example, than exposure time with slip clutch screwdrivers.
For more in-depth information on these technical subjects, which are linked to current regulations, take a look at our Manual on ergonomics and safety in industrial tightening operations (available in Italian).
What causes the risk of hand-arm reaction?
When a screwdriver has completed tightening and the preset torque is reached, the tool can react, with reactions that are especially evident when tightening torques are high. These reactions can cause reaction, which strains the operator’s hand and arm, causing damage to their muscles and tendons in the long term. This sort of reaction often results in sudden movements of the hand-arm system and excessive use of force needed by the operator to counter the reaction.
How can all this be prevented?
Solutions to hand-arm reaction risk
In addition to using the mechanical clutch screwdrivers with automatic shut-off as recommended above – which, by instantly cutting off transmission between the blade and rotating parts, cancel out the inertial force – when dealing with high torques and wanting to further reduce the operator’s risk of hand-arm damage, using auxiliary grips is the most effective option to prevent reaction: one of the most commonly encountered risk factors.
In such cases, you can make use of a Fiam aid devised in response to ISO standard 11148-6 that – for jobs with a torque in excess of 4 Nm for straight tools and 10 Nm for pistol tools – recommends the use of an auxiliary grip designed to reduce the reaction, sharing the load between both hands instead of just one.
Beyond auxiliary grips: short guide to other aids for hand-arm system health
We’ll now take a quick look at the main features of other ergonomic solutions that – when used in conjunction with hand-held tools – benefit operators greatly as they perform assembly jobs.
Telescopic arms They cancel out the reaction on the hand fully and ensure easy handling and unrestricted action as they:
- Absorb the tool’s reaction
- Allow the tool to rotate around its own axis and hence work correctly even with tightening jobs on an angle
Cartesian arms Solutions that:
- Stop the tool kicking back against the operator’s hand
- Require no effort to hold the tool
- Drastically reduce vibrations or eliminate them altogether
- Allow the operator to hold the tool practically straight on to the point being worked on
Do you want to receive further information on these solutions for your business? You can contact the Fiam Technical Consultancy Service directly, leaving a comment below or using the relevant contact form on our website.
In addition, you can order a copy of the “Ergonomics and safety in industrial tightening operations” manual published by Fiam and available in Italian or attend one of the numerous courses on the subject of ergonomics that we organize on a regular basis both at our premises and directly at the customers’ manufacturing plants.