Safety in channel storage systems employing shuttles

In order to enhance storage capacity and/or storage density, channel storage systems employing shuttles are increasingly being used. Owing to the automatic pallet stocking and retrieval processes, these systems present hazards to persons. Possible measures for reduction of these hazards have been developed by the materials handling and warehousing technology committee of experts in conjunction with manufacturers and the market surveillance authorities.

Channel storage systems employing shuttles are a space-saving solution for the storage of goods. The goods are generally stored on pallets located in a long row one behind the other in special shelf rails (channels). A shelf consists of multiple channels which are located above and beside each other without aisles. The pallets can therefore be accessed only at the two ends of each channel.

A “shuttle“ is used to move the pallets within a channel. At stocking, a pallet is inserted into one end of the channel by a fork-lift truck (generally a reach or counterbalanced fork-lift truck). From there, it is retrieved by the shuttle and automatically transported along the channel to the storage point. The shuttle runs on special guides within the individual channels. For retrieval, the entire shuttle or its lifting mechanism passes beneath a pallet and raises it. The hoist height is generally only a few centimetres, sufficient to lift a pallet clear. The shuttle is powered by onboard batteries.

The shuttle is in turn transported to the desired channel and inserted into it by a fork-lift truck. Once the channel is reached, the shuttle leaves the truck and enters the desired channel, generally automatically. The shuttle receives its start signal from a remote control, which is typically located on the fork-lift truck and is operated by the driver of the latter. The stocking and retrieval processes themselves are automatic, i.e. they usually involve no further observation by the fork-lift truck driver.

The materials handling and warehousing technology committee of experts at the BGHW (the BG responsible for trade and goods distribution) in Mannheim has lately received an increasing number of inquiries concerning how persons are to be protected who, whether in accordance with the regulations or not, access a channel storage system and may therefore find themselves within the danger zone of the automatic shuttles travelling within it.

Should persons approach the shelf, for example because their workplace is located there or because pedestrian areas pass by the shelves, they may enter it, either consciously or otherwise. Should they do so, they will be exposed to crushing and shear hazards towards the bottom of the shelf (up to a height of approximately 2.5 m) between the shuttle and the shelf or the pallets in storage. Persons with the task of clearing faults such as functional stoppage of the shuttle (fl at battery, electronic faults, mechanical jamming, etc.) or slippages of loads within the shelf may be exposed to such hazards throughout the shelf area.

Experts disagree regarding what protective measures are necessary for such storage systems and may be installed in consideration of up-todate good practice. The materials handling and warehousing technology committee of experts has therefore discussed this issue with manufacturers of shuttles and the corresponding storage systems, the market surveillance authorities, and representatives from several BGs. The results were recorded in a table showing the hazards identifi ed, the risk presented, and examples of protective measures. Based upon this table, the materials handling and warehousing technology committee of experts has produced a brochure („Kanalläger mit Satellitenfahrzeugen: Handlungshilfe zur Risikound Gefährdungsbeurteilung“ (channel storage systems employing shuttles: a practical guide to risk assessment) (in German)) which assists the manufacturers of shuttles and of channel storage systems in which shuttles are employed in the conducting of risk assessments in accordance with the Machinery Directive. The brochure may also be useful during workplaceoriented risk assessments in plants in which such storage systems are operated.

Dr. Hans-Peter Kany
Representative of the materials handling and warehousing technology committee of experts at the BGHW for questions concerning safety in channel storage systems employing shuttles.
Tel.: +49 621 1835910
hp.kany@bghw.de