This month we bring you enquiries and answers relating to building a mezzanine from pallet racking columns and beams, building racking outside that will be subject to all weather and fixing racking to a wall.
Building a mezzanine from pallet racking columns and beams
Q. I have a question about the suitability of using pallet racking material to construct a mezzanine that will support people. My company claims that this structure can support a load rating of 125lbs/ft?. The mezzanine structure is 55’9’’ wide x 41’ 3’’ long x 108’’ high and is constructed from “used” USP pallet racking columns and beams.
This structure essentially consists of forty (40) 48’’ x 96’’ frames consisting of 4 columns and two beams that have been interconnected with bar grating and floor board. There are about a dozen bar grating sections that are 30’’ wide x 120’’ long running between the pallet rack beams on the top of the structure. The bar grating is clipped onto the structural beams with beam clips. On top of the bar grating lies about a dozen 3/4’’ thick tongue and groove OSB boards (the floor of the mezzanine) that have been laid at 90 degrees to the bar grating and tek-screwed to the beams and bar grating.
-The beams are 4’’ and 5’’ C-channels that supposedly have a load capacity of 6300 lbs and 7100 lbs respectively.
-The columns are your typical 3’’x 3’’ pallet racking columns and there are 80 of them supporting the entire structure.
– Each column is supposed to be bolted to the floor with two 1/2’’ x 3-1/2’’ lag bolts, but most actually have only one 3/8’’ x 3-1/2’’ lag bolt.
Many of my colleagues have expressed safety concerns with the building material of this structure. The contracting company provided these specifications, but without the services of a structural engineer.
Does the description of this structure present any apparent safety concerns in your opinion?
A. First of all it is not clear if this structure is built in the UK or overseas and while that does not make any difference to the safety aspects, any such structure in the UK falls under the requirements of our Building Regulations and structural calculations have to be submitted for independent checking by a different structural engineer.
As far as SEMA is concerned all that we can say is that it is possible to construct safe structures along the lines that you describe. Unfortunately ‘the devil is in the detail’ with stability and other bracing being critically important. From what you say it might be the case that little or no structural engineering input has gone into this design. The combination of bar grating and what we assume is chipboard floor is to say the least unusual. In the UK we would normally expect to see thicker board (38mm) as a matter of course though the combination of grating and board might make this possible depending upon the support centres being provided.
The total loading of the floor spread over all the columns sounds a little on the ‘high’ side however not impossible though it does depend upon the particular type of pallet racking upright that has been used. Again it is assumed that there are several beam levels below the floor level stabilising the pallet racking columns and if this is not the case it is suggested you might well have cause for concern.
We suggest that your floor supplier be asked to provide calculations justifying the design as it has been built and then the services of a competent structural engineer with experience of the design of this type of structure be used to carry out a check on this design. This latter step should not take an enormous amount of time or cost and will indicate very quickly whether the design is in the correct order or otherwise.
Please remember that with all such structures there are likely to be people working both above and below the floor and if an incident does occur then it is unlikely that everyone will escape without injury.
Finally we can only repeat the words from the airline industry where it was said ‘if you think safety is expensive then try having an accident.’
Building racking outside
Q. I wish to install some static pallet racking outside. We already have indoor racking which complies with the SEMA code of practice and is inspected accordingly.
Are there any extra checks we need to carry out on racking which is outside and how do we comply with regards to rusting of the uprights/beams?
A. The inspection checks for external racking are similar to internal racking; however, the design and the protection coating can be significantly different.
The supplier should design the racking to ensure that it is acceptable for the additional wind loading and the racking should be installed by trained installers who are members of SEIRS (Storage Equipment Installers Registration Scheme). The design often requires the use of different floor fixings to the standard fixings used on internal racking.
The normal painted finish provides very little corrosion protection for external racking which therefore rusts in quite a short period of time. The beams are not painted internally and can rust from the inside out. A competent ‘third party’ rack inspector, preferably a SARI (SEMA Approved Rack Inspector), will be able to give an opinion as to whether the racking will last for another year or whether it needs to be replaced. Racking with a galvanised finish is normal for external applications and will last longer outside. Any new rack purchased for an external environment should be designed to suit this environment with a galvanised finish.
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 Publications
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
The next SEMA annual conference, “Safety in the Storage Industry: Safer By Design”, is scheduled for Thursday, 5 November 2009, the venue being the National Metalforming Centre, West Bromwich, West Midlands. To obtain a copy of the programme and a booking form please contact SEMA.
SEMA Tel: 0121 601 6350 www.sema.org.uk
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