Examining palletiser safety

A key safety principle for palletisers and depalletisers is 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.

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.

These safety points are key considerations when using palletisers and depalletisers. However, it is also important to keep abreast of the latest European machine safety regulations and the latest guidance from the Health & Safety Executive.