When does shelving become racking and how do inspections differ forms the basis of our first question this month. Then we have a question relating to the correct positioning and usage of pallets and pallet blocks.
When does shelving become Racking
Q. During inspections and audits, I am often asked when does shelving become racking that would require inspection and when can it remain a standalone shelved rack carrying minimal loading, only requiring a pre-user check supported by perhaps a monthly visual inspection. Other questions are, should this be fixed to the wall, floor or both, would something like a 6ft letter rack require statutory inspections and what degree of competency sould an inspector have be?
A. Not a straightforward question and one that is full of grey areas between different definitions as I am sure you have discovered.
The first issue is to whether the rack is accessed by powered mechanical equipment or substantial hand powered equipment such as hand pallet trucks. If goods are placed by powered equipment then it tends to be defined and treated as pallet racking no matter what the height, as the forces of accidental impact can be severe and safety factors need to be proportionate. Into this category you should add storage accessed by hand pallet trucks or similar types of bogeys, as an impact from a hand pallet truck with a 0.5 tonne pallet being pulled or pushed along can be similar to the impact from a powered machine.
At the other end of the scale we have office shelving such as letter racking which most people never dream of having inspected although perhaps they should, as people do on occasion pull over wooden or steel cupboards while trying to access the top shelf without using an appropriate set of steps. Usually such storage is light weight though sometimes it is wise to look at how paper for the photocopier is stored! Common sense tends to prevail here and inspections are not normally required for office furniture.
Somewhere in between these two sits shelving which must be hand loaded and which in general needs the same level of inspection as pallet racking. Often these are carrying heavy loads and collapses of this kind of material can cause serious injury, so it is difficult to justify a lower level of safety here. One of the problems with stores is that one bay of shelving can be used for storing light weight uniforms or rubber belts while the next bay contains spare starter motors for engines imposing the maximum load that the system will carry, all stored on the same type of shelving.
SEMA splits shelving into ‘low rise’ and ‘high rise’ categories.
Low rise is less than 3600 mm in height and less than 6:1 in height to depth ratio (height is floor to topmost loaded shelf and depth is overall depth of bay, or two bays if joined together back to back).
High rise is best defined as anything that is too tall or slender to fit into the low rise category with most of the limitations on this being design ones. More substantial structures require more precise design methods.
Taking your query as to whether it should be fixed to back to a wall or to a floor SEMA recommend that all shelving with a height to depth ratio of less than 4:1 can be free standing. Anything greater than 4:1 requires fixing to the floor and / or the building or other structure, the requirement becoming more complex the higher the frame and the more side force on the shelving system. (see SEMA high and low rise shelving codes for more information).
Fixing to a building or other structure is not as simple as it sounds; modern buildings tend to be made of lightweight materials, the designers of which are reluctant to accept loads onto their structure other than what was originally specified. Older buildings are often more substantial in nature and the original designers are no longer around to dispute the matter.
We would suggest that you could start by reading through the two SEMA codes:- Design of low rise steel shelving and Design of high rise steel shelving as a good starting point to try and clear up some of the grey areas for your particular installation.
Poorly Positioned Pallets
Q. Recently I visited a warehouse where (amongst other issues) the pallets appeared to be poorly positioned in the racking with the pallet blocks overhanging the racking beams .From memory I believe that the pallet blocks should be placed on the beams (to prevent undue stress on the pallet base members), however I cannot find this written in the HSE documents, PM15 or HSG76. Please can you confirm if this is the case?
A. Your memory is correct and corner blocks on pallets should be supported directly on the beams. This seems to have been something that has been omitted in extracting the most important issues from the SEMA codes for insertion into HSG 76.
Some guidance on this is given in BS EN 15635:2008 Static Steel Storage Systems – application and maintenance of storage equipment, which indicates a general 50mm overhang of the pallet from the face of the beam.
More detailed information is given in BS EN 15620:2008 Static Steel storage systems – tolerances deformations and clearances, which applies a +/- 10mm tolerance to this 50mm placement which should be equal to front and back of the rack.
From the information received it would appear that while this requirement is not being met probably because the racking has been specified for a different depth of pallet the corner block is just being supported on the beams by about 20mm or so which is not ideal, however not dangerous as long as the user maintains what seems to be presently happening and locates the pallet exactly equally on the front and back beams.
There is a strong possibility that someone will try to position pallets such that they are achieving the recommended 50mm overhang at the front which they can see during the positioning operation and will then end up with the rear of the pallet being supported on the bottom board only, which is not acceptable and is dangerous. There is also the possibility of a non-standard pallet appearing in the warehouse with smaller corner blocks which will make the present situation worse.
The question is whether the User has a good enough management system in this warehouse to ensure that all this never happens. Alternatively they strip down the racking, obtain new frame bracing members which will allow the rack to be re-built to the correct depth using the existing uprights and beams. This will suit the pallets currently in use and eliminate the possibility of miss-positioning these pallets altogether.
SEMA is delighted to be working with WLN on the storage Q and A Column, on the WLN website is a list of previously published columns.
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