Empty pallet stacking or unstacking machines
Published by CEN: 1997
Published by BSI: 1998
Reviewed: 2006 when a decision was taken to completely revise the Standard. Standard being revised by CEN/TC 146 WG3 convened by P. Capelli (UNI).
The revised Standard will take into account:
The revised version of EN 415-4 is unlikely to be published until 2011.
Amended: No amendments
Note: This Standard has only been harmonized to the Machinery Directive 98/37/EC and so when this Directive was replaced by 2006/42/EC on 30 December 2009 this Standard ceased to be a harmonized Standard.
Clause 3 describes the different types of palletizer and depalletizer covered by this Standard and includes isometric drawings to illustrate how each machine works.
Clause 3 also defines the typical terminology used when discussing these machines like pallet, layer layout and pallet load.
Clause 4 of the Standard identifies the injuries that can be caused by each type of palletizer and depalletizer.
Most injuries occur when operators or maintenance personnel enter the machine and become trapped between fixed parts and moving parts such as:
The risk of injury is increased by the unexpected nature of machine movements.
There are also hazards from falling loads, sudden movements of jammed product or pallets when they are freed, or by movement due to stored energy in pneumatic or hydraulic systems.
In the UK deaths occur annually on palletizers and depalletizers.
Clause 5.2.4 confirms that danger zones must be protected with a combination of fixed and interlocking guards and the height of distance guards must be selected using Table 2 of EN 294 (now replaced by EN ISO 13857) rather than Table 1.
Clause 5.3.1 describes several methods of safeguarding the pallet entry or exit openings in palletizers and depalletizers. These methods include:
Clause 5.3.2 makes the point that the entry and exit point for people should be different from the entry or exit points for pallets. Typically this will be a guard door interlocked with a device complying with EN 1088. The reason for this requirement is that if an operator enters a machine through an ESPE there is no visual clue that someone has entered the machine 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 makes the point that after a person has entered a machine it must only be possible to reset and restart a palletizer or depalletizer 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 zone. On some large machines where it is not possible to see all of the inside of the machine from a single position, it may be necessary to have more than one device to comply with this requirement.
On machines where it is possible for someone inside the machine to not be seen by someone outside the machine, clause 5.3.4 requires that presence-sensing devices or trapped key interlocking devices are used to minimize this risk.
Clause 5.6.1 requires that loads and mechanisms are automatically restrained when the machine is stopped so that they do not move unexpectedly under gravity when an operator enters the machine.
Manufacturers of palletizers and depalletizers now routinely fit safety rated ESPE to pallet entry and exit points, however it is still possible to find machines where the device for resetting the ESPE is not located where there is a clear view of the danger zone.
The Standard suggests a presence sensing or trapped key interlocking system as a method of preventing starting of a machine while someone is still inside, however the most popular method of minimizing this risk is an interlocking device which provides a key for the operator to take with him into the machine. This type of key system is not described in either this Standard or EN 1088 and so it is not surprising that there is some confusion about the correct use of these devices.
EN 415-4 can be purchased as BS EN 415-4: 1998 from BSI Standards.