How safe is your palletiser?
Most palletiser related injuries occur when people enter the machine and are trapped between its many parts. Paul Laidler of TÜV SÜD Product Service examines safety in this important area of packaging machinery operation.
Packaging machines, and in particular palletisers and depalletisers, are some of the most prevalent machine types found across the majority of manufacturing sectors. The Health and Safety Executive (HSE) has recognised palletisers and depalletisers as a class of machine that require particular attention as injuries can be severe or even fatal. HSE statistics in March 2012 showed that, in the previous five years, there had been 44 serious accidents, including a fatality, and two dangerous occurrences involving palletisers and depalletisers, with six of these accidents resulting in prosecution.
The HSE outlines safety principles for palletisers, which includes guarding of machine entry or exit points, with methods including interlocking moveable guards, captive key exchange systems or electro-sensitive protection equipment (ESPE), such as light curtains. Due to the size of palletisers, full body access is a common occurrence. If not appropriately guarded, unsafe access is therefore possible, as well as unsafe transfer between zones within the machine. This means that personnel can be in the machinery without the knowledge of those outside and as HSE prosecutions have shown, the machinery might be re-started with severe consequences.
Where light curtains are in place, it should be safe to assume that operators are fully protected, but we all too regularly see them positioned incorrectly so that they afford no safety benefit. One common area of concern is the positioning and detection capabilities of the light curtain as they tend to be positioned to detect the pallet, rather than the pallet load. This means that the gap between the light curtain and the pallet load is too large, which allows entry when in a muted state. It is therefore advised that 'EN 415-4: Palletisers and Depalletisers' is referenced for additional information.
It is also essential that, when used, guards are of the correct dimensions to stop people getting under or over them. The height of guards must therefore be selected using Table 2 of EN ISO 13857 'Safety of machinery - Safety distances to prevent hazard zones being reached by upper and lower limbs', rather than Table 1.
One option to improve safety at entry and exit points is to use a captive key exchange system. This is a simple, but highly effective, method to guard against such a potentially fatal occurrence. A mechanical key must be removed to isolate the machine and release another key, which the person takes with them into the palletiser. While the key is with the person, they are safe as under no circumstances can the machinery be re-started until that key is returned. Another common sight is the lack of infill panels between conveyor rollers, which is also a requirement within EN 415-4 to prevent trapping and crushing between the pallet and the roller. If fitted, they would prevent injury if limbs come into contact between the conveyor and the pallet.
However, these problems are not limited to old legacy machinery with retrofitted guarding, as they are still a common occurrence with new machinery carrying CE marking. In such cases, if the machinery manufacturer has installed guarding incorrectly, they can be prosecuted under the Machinery Directive.
The safety standard that should be followed to ensure safety is 'EN 415-4: Palletisers and Depalletisers'. Originally published in 1997 by CEN, the European Committee for Standardisation, a decision was taken in 2006 to completely revise the Standard, taking into account changes in machinery technology such as the increasingly widespread use of industrial robots. The reasons given for the review also specifically mentioned "the additional risks posed by palletising and depalletising systems" as well as "additional measures to minimize the risk of a machine being reset and restarted while someone is inside the machine."
CEN's aim was to publish the revised version of EN 415-4 by 2011, but it is still under development. This means that while EN 415-4 had been harmonised to the old Machinery Directive 98/37/EC, when this was replaced by 2006/42/EC on 30 December 2009, it ceased to be a harmonised Standard. This means that technically there is no standard for palletisers and depalletisers on the latest listing for Machinery Directive published in the Official Journal of the European Union.
While this means that machinery owners cannot be prosecuted under EN 415-4, they could still be prosecuted under the Provision and Use of Work Equipment Regulations (PUWER), or machinery suppliers prosecuted under the Supply of Machinery Regulations, which relates to CE Marking requirements. However, TÜV SÜD's advice is to continue using the Standard as it remains current and indicates 'best practice', and shows due diligence on the part of the machinery owner, until its revision is complete and published.
While we wait for CEN to publish a revised standard and best practice, advice is to continue to follow the existing EN 415-4, it remains a difficult task. The failures we see on site are often due to a lack of appropriate internal expertise and physical resource to do an in-depth and correct PUWER assessment of all machinery. With palletiser machinery being on such a large and complex scale, the issue of time and expertise availability is further magnified.
However, to immediately identify any issues, a thorough and correct PUWER assessment should be completed before any new machinery goes into operation. Problems can then be rectified with the manufacturer, so that they or the machinery owner no longer run the risk of a prosecution under the Machinery Directive or PUWER. A decision to 'make do' or not invest in the appropriate expertise to run PUWER assessments on palletiser and depalletiser machinery could prove fatal - the HSE statistics prove that.
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