Our first question this month asks what is the Maximum number of Shims that can be used to set the vertical of the uprights and our second is when does Shelving become Racking.
Maximum Number of Shims
Q. If the floor is uneven, what is the maximum number of shims we can use to set the vertical of the uprights?
A. This depends largely on the type of floor fixing you are using so would suggest you obtain some advice from your supplier. In our experience the ‘better’ fixings can allow around 50mm of shimming however we would always recommend that high piles of shims like this be locked together by placing a run of weld up the pile to lock them into a solid pack as there is a tendency for them to twist out of the pack particularly if only fitted with a single floor fixing and can then cause upright support problems. We would also caution on large packs of shimming as the truck will follow the floor while your rack is vertical and your beams are horizontal but the load is not. This means that during placement or retrieval of pallets it is often one side of the pallet or one corner of it that comes down on the beam first and imposes a very high point loads before the rest of the load is spread out over the both beams and the full length of the beams. This can cause local overstressing which can result in beam buckling and collapse! This does not occur often however it is not unknown so care is needed with the particular aspects of the site.
When does shelving become racking?
Q. Could you please shed some light on a question we have: ‘When does shelving become racking?’
A. A much more complex issue that it first seems as presumably you have discovered!!
Generally, shelving is storage media that cannot be approached by mechanical handling devices such as fork lift trucks, order pickers and other heavy pieces of mechanical handling equipment where it would be classed as racking. The reasoning being that with thin shelving upright and other sections an accidental collision from a piece of mechanical handling equipment can be very dangerous. Shelving is therefore normally hand loaded and due to manual handling guidance, has unit loads of less than 20 or 25 kilogrammes depending on the country, and is isolated from heavy mechanical handling equipment.
It is often thought that ‘shelving’ would have a height restriction however as I am sure you are aware it is possible to have 3 and 4 tier shelving systems as well as having crane swept systems where the crane is guided by mechanical means such that there is no possibility of the crane hitting the shelving structure. If shelving is correctly designed such high shelving structures are perfectly possible. Hand loading and picking as opposed to mechanical handling is the means of operation that probably gives the clearest definition between the two rather than any height definition.
Just to complete the storey, shelving is not suitable under any circumstances for operatives climbing the shelves to retrieve items of goods.
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