Poorly guarded palletiser machines used in manufacturing pose a serious risk of death and injury – particularly during maintenance – but a soon to be revised European standard sets out the safety precautions to follow.
Packaging machines, and in particular palletisers and depalletisers, are one of the most common types of machinery found in manufacturing plants. Due to the number of serious injuries occurring on them each year, the Health and Safety Executive (HSE) recognises that palletisers are a class of machine that requires particular attention.
Indeed, in March 2014 HSE prosecuted a manufacturing firm after a worker suffered a hand injury while clearing a blockage on a poorly-guarded palletiser machine. He suffered multiple fractures of his hand and lacerations and was unable to return to work to perform a similar role for several months. The worker had bypassed an interlocked gate, which was a common practice by staff, to clear the blockage n the machine. As he restarted the palletiser, his hand, which was resting on the top frame of the machine, was struck by a moving part which operated the claw mechanism.
The standard EN 415-4: Safety of packaging machines. Palletisers and Depalletisers is the main reference for employers whose activities include this type of equipment. Clause three describes the different types of palletiser and depalletiser and includes isometric drawings to illustrate how each machine works, as well as defining the terminology used for such machines, such as ‘pallet’, ‘layer layout’ and ‘pallet load’.
HSE also outlines safety principles for palletisers and depalletisers, which state that danger zones must be protected, including the guarding of machine entry or exit points, with methods such as interlocking moveable guards, captive key exchange systems or electro-sensitive protection equipment (ESPE), such as light curtains.
Ease of access
Due to their size, if palletisers are not appropriately guarded, unsafe access and unsafe transfer between zones within the machine is possible. This means that personnel can be inside the machinery danger zone without those outside knowing, who can re-start the equipment with severe consequences for those inside. Consequently, most palletiser-related injuries happen when people enter the machine for maintenance or to check if there is a problem with it, and they end up trapped between its many parts, such as transfer devices, rise and fall mechanisms, pusher mechanisms, industrial robots and moving pallets.
As palletisers transport heavy and bulky loads, operators are also exposed to potential hazards from loads falling off the moving pallets. The risk of injury is also increased by the unexpected nature of machine movements. It is therefore essential that guards are of the correct dimensions to stop people getting under or over them.
Where light curtains are in place, which are opto-electronic devices used to safeguard personnel, many assume that operators are fully protected, but if they are positioned incorrectly there is no safety benefit at all. Indeed, a 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 also essential that where guards are used they are of the correct dimensions to stop people getting under or over them. Clause 5.3.2 of EN 415-4 states that the entry and exit point for people should be different from the entry or exit points for pallets, and typically this will be a guard door interlocked with a device complying with EN 1088. The reason for this is that if an operator enters a machine through an ESPE there is no visual clue that someone has entered the danger area, only that the ESPE has initiated a stop, which could be for a number of reasons.
However, if the operator uses the personnel access door, it is clear that someone has entered the machine. Clause 5.3.3 states that after a person has entered a machine, it must only be possible to reset and restart a palletiser or depalletiser by a deliberate action on a device located outside of the danger zone, in a position where the person operating the device has a clear view of the danger area. On some large machines, where it is not possible to see all of the inside from a single position, it may be necessary to have more than one device to comply with this requirement.
One option to improve safety at entry/exit points is to use a captive key exchange system. This is a simple but highly effective method to guard against a potentially fatal occurrence. A mechanical key must be removed to isolate the machine and to release another key, which the person takes with them into the palletiser. While the key remains with the person, the machinery cannot be restarted.
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 in the event of a person’s limbs coming between the conveyor and the pallet.
The correct standard
These safety problems are not limited to old legacy machinery with retrofitted guarding; 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 regulations implementing the Machinery Directive.
EN 415-4 was originally published in 1997 by the European Committee for Standardisation (CEN). 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 included “the additional risks posed by palletising and depalletising systems”, and “additional measures to minimise 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. While EN 415-4 had been harmonised to the old Machinery Directive 98/37/EC, it ceased to be a harmonised standard when this was replaced by Machinery Directive 2006/42/EC on 30 December 2009. This means that technically there is no standard for palletisers and depalletisers on the latest listing for the Machinery Directive published in the Official Journal of the European Union.
Although 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 relate to CE marking requirements.
Until the revision of a new standard is complete and published, the advice is to continue using the existing standard, as it remains current, indicates best practice and shows due diligence on the part of the machinery owner.
While we wait for CEN to publish a revised standard, following EN 415- 4 remains a difficult task for many employers. The failures 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 the availability of expertise are paramount.
To immediately identify any issues a thorough PUWER assessment should be completed before new machinery goes into operation. Problems can then be rectified with the manufacturer, so that operatives remain safe and the machinery owner does not face the risk of a prosecution under the Machinery Directive or PUWER. A PUWER assessment on palletiser and depalletiser machinery could prove vital.
Paul Laidler is business director for machinery safety at TÜV SÜD Product Service
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