Severe degree of bend on beams
Q. A substantial amount of re-organising in one of our facilities was undertaken last year.
The declared maximum weight for each cross member beam is 2100kg. An exercise has been conducted to validate we are not exceeding this declaration and it confirms we are within this limit. However, when assessing the storage facility, the beams have a severe degree of bend. What would be the logic/solution to this problem?
A. First of all we wonder if your substantial re-organising of the racking has involved moving beam positions on the upright. Carrying capacity of the beam depends on a combination of the beam strength and also of the strength of the associated upright. If the beam is lifted giving a larger pitch between beams on the upright, then the upright will be more flexible and, in turn, cause the beam to deflect more. If beam pitches are moved then it is necessary to recalculate the capacity of the rack and possibly revise the carrying capacities originally shown on the racking. Some racking has the carrying capacity of the beams painted or marked on them, however, this is only valid for the particular beam pitch which was specified at the time of the original order.
A second thought would be to check that your loading is uniformly distributed over the whole storage area. Carrying capacities are normally calculated on this basis and if you are using different size pallets or have pallets that are loaded in a way that is not uniform then you may have a problem.
It would also be sensible to ensure that the beams return to straight in the unloaded condition. It is not unknown for a previous overload to cause a permanent ‘set’ in a beam which then ensures that under subsequent normal loading an excessive deflection takes place.
If all of these situations are in order it is suggested that you measure the deflection (use a taut string line below the beam as measuring from the floor includes the inaccuracies of the floor itself). Under full working load you might expect to see a maximum deflection of Span / 200. In other words if you have a 2700mm long beam the expected deflection would be 2700 / 200 = 13.5mm which is in fact quite noticeable in a racking situation – however it is the limitation laid down in the SEMA code of practice for the design of these products and is quite normal.
If your deflection exceeds this value then you do have a problem and we would urge you to make contact with the supplier of the product (whose name may well be on some of the rack warning notices or stamped on the upright or beam sections) and seek his advice. If you are not able to identify the supplier then there are consultants who operate in this field who might be able to help you and SEMA would be prepared to provide the names of some consultants known to be operating in this field if you so wish.
Effect of tack welding racking
Q. What is the effect of tack welding on racking post installation – how does it affect the steel?
A. Tack welding may have little effect on most steels. However the racking industry has in the past and even today used substantial volumes of cold reduced steel where heat input from welding operations will anneal the steel and substantially soften it. If this is a genuine tack done by a good quality operator the effect may be minimal, however, there is no way of proving this and most manufacturers will specifically state in their terms and conditions that welding will invalidate any guarantee on their product.
SEMA Technical Enquiries
We hope you find the above articles, and those in previous editions, interesting. If you have a query send it to us by fax or email and we will do our best to have it answered by one of our technical experts.
SEMA Rack Safety Awareness and Inspection Courses
SEMA runs a one-day safety course on Rack Safety Awareness and Inspection. These courses are aimed at end users, giving an in-depth look at the need for inspections, how to conduct an assessment and what actions to take when this is completed. These courses are normally held at the SEMA headquarters but arrangements can be made to hold them at the delegates’ premises.
SEMA Approved Rack Inspectors Qualification
This qualification is aimed at professionals who conduct rack surveys as an integral and significant part of their duties. It involves delegates in undertaking an in-depth SEMA Course, together with an examination and practical assessment. CPD will be an important part of the qualification, demonstrating to end users that SEMA Approved Inspectors maintain a high professional standard.
SEMA publishes a number of documents including Codes of Practice, ‘Guides’ and European documents – all of which are available from our Office. For further information on these documents contact SEMA or visit our website, www.sema.org.uk. and click on ‘Codes of Practice’.
SEMA USERS Club
SEMA runs a USERS Club designed to be of benefit to purchasers and users of storage equipment.
Members receive newsletters, access to specialised events and discounted rates on publications and codes of practice. For further information contact SEMA.
SEMA Annual Safety Conference 2009 – a date for your diary
The next SEMA annual conference in the series “Safety in the Storage Industry” is scheduled for Thursday, 5 November 2009, the venue being the National Motorcycle Museum, Solihull.
Tel: 0121 601 6350