Our first question this month asks about safe working loads for a stackable drum storage unit whilst the second question asks for guidance on spacing bars fitted between the racks.
Load Testing
Q. We have constructed stackable drum storage units in house for our own use. What would be the requirements/contacts to establish safe working load etc? This is to ensure their safety for use around our personnel.
A. It sounds as if you might be in a little trouble here!
As you have no doubt realised the owner / operator of a racking system has a duty to inform his operatives on how to use the system safely before allowing it to be used. Fundamental to this is the need to identify and inform operatives of the safe carrying capacity of the structure that you have created with an adequate factor of safety so that operatives can know how to use it safely.
Often in these situations structures have been welded together from surplus material with no involvement of a structural engineer who might be able to calculate a carrying capacity based on section sizes and materials if these are known together with specified weld dimensions and quality of welding operators involved to achieve known joint strengths.
Usually such structures are to a visual examination ‘well over designed’, however this will not wash with HSE in the event of a collapse and an injury resulting from this. It is also very difficult / impossible to identify a good weld from a bad one just on a visual examination.
We would suggest you need the services of a chartered structural engineer experienced in steelwork design and carrying adequate professional liability insurance, who might be able to make some calculation to identify what the carrying capacity is with the appropriate safety factor. As we suggested at the beginning it would have been better to calculate section sizes and weld details for a given carrying capacity at the beginning and then fabricate something that is going to suite the requirement rather than doing things the other way round and hoping that what has been made is adequate for the purpose.
Your only alternative to this is to get a reputable company to load test your structure and issue a certificate of test with the appropriate safety factor removed to give you a safe working load. You might find it appropriate to have a structural engineer supervise this and issue an appropriate certificate for safe working load as opposed to the test load. There is always the risk in such situations that the structure is destroyed under the test load so safety of those nearby while the test is being done is paramount.
Q. I have some racking in our warehouse and I have been told that I must have spacing bars fitted between the racks which are back to back. The back to back racks are 450cm tall and 110cm deep each.
A. SEMA recommend the use of run spacers on rows of back to back racking however it could be argued that structurally it is not necessary. Plainly if a run of single sided racking will stand by itself along the gable wall of a building for instance, then it is difficult to argue that it is essential that two identical such runs in a back to back orientation must be tied together with row spacers.
SEMA take the view that row spacers add significantly to the robustness of the rack design particularly if the rack is accidently damaged in some way by a fork lift truck. Their presence can stop a minor incident becoming a major collapse. The cost of these items is small in relation to the cost of the racking system as a whole and SEMA consider the marginal increase in cost is more than justified by the extra security achieved.
If you look in BS EN 15635 clause 6.3 e) the spacing of these items is defined however the requirement to have them included is by implication rather than as a formal requirement.
Hope this explanation helps. SEMA has a code of practice on load notices http://www.sema.org.uk/page.asp?node=2 which gives recommendation on the information that should be on a load notice.
The HSE publication HSG76 also gives some guidance http://www.hse.gov.uk/pubns/book s/hsg76.htm.
Comments are closed.