Our first question this month concerns the effect of deflection on a beam and how much is allowable.
Then we consider the benefits of a SWL notice and its need when racking will be used for storing light weight product only.
Beam Flexing
Q. A few months ago we bought some second-hand pallet racking from a company who were told that the heaviest pallet we would be using would be a maximum weight of 1000kgs of glass. We have started to notice that the beams in some areas were bowing with 800kgs for one pallet and 900kgs for the other, side by side. A representative from the company who supplied and fitted the racking said that there was an acceptable amount of bowing allowed and what we were experiencing was acceptable. Could you clarify what the acceptable levels of bowing are as my worry is that if we keep using this racking as we are at the moment, we may end up with an accident.
A. SEMA have no control over what standards second hand racking might be sold to and this is a matter between the purchaser and seller perhaps in a similar manner to buying something second hand off the Internet.
There might be two issues here. First of all, yes beams do deflect under load and this can be quite noticeable when applied loads get towards maximum. The SEMA Codes of Practice allows a maximum deflection of span / 200 when a pair of beams is under maximum load.
For beam length of 2700 mm this would be 2700 / 200 =13.5 mm. This may not seem a lot however it is quite noticeable when the lower run of beams is viewed along the aisle when it can look something like a washing line. If you wish to check this we suggest the use of a taut string line immediately under the beam and measure vertically from the string line to the underside of the beam at centre and ends of beams. The temptation to measure to the floor should be avoided as often the floor is not level to start with.
If your beams are getting close to the top of the pallet bellow you may have inadequate clearances. SEMA recommend a minimum of 75 mm clear to allow the pallet to be handled in and out of its location and deflections should be nowhere close to this. If this is the case and you may have to re-profile the rack by increasing the nominal space between beams. Be aware that this will result in a longer free length of upright between the beams so the upright will not carry the same load therefore you can expect to have to de-rate the carrying capacity of your rack and change the load signs which your supplier should have attached to the rack defining the carrying capacity when supplied.
It is hoped that helps and if you need more assistance try having a look at the SEMA Code of Practice for Use of Static Pallet racking. Go to the SEMA web site, click on the top bar marked Codes of Practice and the drop down menu will appear to this particular document and if you fill in the online form and meet the criteria a free pdf version of the code will be sent which has a lot of this information. Also another free download off the HSE web site is well worth while. Search ‘HSG 76’ and be well stocked up with printer ink as this is over a 100 pages!
Changing Loads
Q. We have standard warehouse racking in all of our stores and are never going to get anywhere near to the SWL with any of the products that we sell. Typically, a fully loaded bay or run would probably be around 10% of the SWL.
I am aware that HSG76 states that signage should be in place but given that we will never store anywhere near the maximum load allowed, do we still need to provide SWL notices.
A. You are correct in that there is no specific legislation that requires a sign to be placed on racking, however it is good practice, and it is this “however” that is important!
There is an obligation on an employer to ensure operatives have all the information needed to operate the racking system safely. In your situation the system will operate satisfactorily as long as you are storing your present range of products. If this changes due to a change in your company’s policy or business then there is a need to have within your procedures something which highlights the need to review the carrying capacity of the racking as part of any change that might be made.
It is reasonably foreseeable that in the turmoil of such a policy change within a company such an issue might get overlooked! In the event of an accident so caused the question might be posed as to why the industry standard policy of having load notices on the racks was not followed, who made the decision not to do this and why? The answer to the last question would likely be to save a little management time and some minor cost which might not go down too well as a reason given an injury claim in court.
Hope this explains the logic behind the HSE, Environmental Health and SEMA coming as close to saying load signs are mandatory as possible without actually saying that.
If you want to remove them it is suggested your company procedures need to be absolutely watertight so that changes would be picked up and the rack would never be overloaded no matter what the circumstances.
Another important reason to keep them is that they usually have the supplier’s address and telephone number together with some other general guidance relating to safe usage on them. All operatives are exposed to this safe use guidance and in the event of some rack damage this allows shop floor personal to seek advice or replacement materials without having to trawl through filing cabinets of orders and paperwork from 10 years ago to identify who supplied the rack and from where a replacement beam can be obtained.
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