Our first question this month asks about Back Stops and our second is looking for information on tyre racking.
Back Stops
Q. We have a new install and would like to know do we need back stops?
A. The SEMA policy with respect to back-stop beams is given in clause 3.10 of the SEMA Code of Practice for the Use of Static Pallet Racking, a free copy of which is available via the SEMA website:
3.10 Pallet back stops
The use of pallet back stops attached to the racking structure is not widespread because of the danger of structural damage and is not recommended.
If racking layouts are correctly designed to give adequate clearance between back to back pallets or load, or alternatively, between a pallet or load and other obstructions at the back of a rack, then back stops are unnecessary for a trained driver to deposit a pallet correctly. (See appendix 5)
If back stops must be provided then they should be designed either:
1. As a replaceable warning device which will give way without structural damage to any structural rack members. This type of pallet stop is known as a safety back stop.
Or
2. For a load or thrust stated by the Specifier, which can be regulated. A pallet stop designed for this load or thrust is known as a buffering back stop. The racking structure shall also be designed for the load or thrust. Recent research shows that this load of thrust is very difficult to define.
BSEN15635 “Steel static storage systems – Application and maintenance of storage equipment” gives the following with respect to backstops
E.4 Incorrect placement of unit loads
If a unit load is not placed in the correct way, a larger than normal horizontal and/or vertical force will be exerted on the storage equipment during loading.
For example, a larger than normal horizontal force will be exerted on the storage equipment during loading when either of the following types of misuse occurs:
a) When a pallet, or other media, is pushed rearwards while in contact with the beams or pallet foot supports, thereby creating a large horizontal frictional force. For example, in the case of a steel stillage when the front two of the four legs are placed on the pallet foot supports and the stillage is slid into the storage position;
b) When a backstop is intentionally and forcibly used, i.e. the truck driver continues driving until impact occurs with the pallet stop. In practice, this can occur when the pallet backstops are provided, thereby creating large impact forces and damage to the backstops and supporting rack structure. Therefore, sufficient horizontal clearance should be provided according to EN 15620 and truck drivers should be trained to place the unit loads correctly and accurately without the use of pallet buffering back stops.
Tyre Racking
Q. I am looking for information or guidance on tyre racks (either portable or stationary) design and limitations. Ultimately, I am looking to reduce the risk potential of our employees working around tyres stored in racks. What is the best (safest) storage system to use in our new facilities?
A. SEMA does not have any guidance specifically relating to tyre racks and we are not aware of similar guidance elsewhere.
In the UK and Europe there is guidance with respect to floor fixing shelving. In both cases stability is considered via the height to depth ratio (H:D). In the UK the SEMA Code of Practice for the design of Low-rise static steel shelving gives the following in clause 14.2;
14.2 Height to Depth ratios
14.2.1 the height of the shelving for the purpose of assessing height to depth ratios shall be the height to the top of the topmost loaded shelf. The depths of the shelving shall be the overall depth of the frame. Where shelving is joined together back to back to form double sided runs, the depth of the shelving shall be the overall depth of the two frames and the space between provided that the links joining the frames together are spaced at not more than 2.0m centres vertical.
14.2.2 For height to depth ratios not exceeding 4: 1 the shelving can be free standing without the need to fix to the floor, walls or adjacent structures. Care should be taken in all cases to ensure that unsuitable floor coverings are identified. For instance, thick carpet can result in unstable surfaces and might need to be removed.
FEM10.2.06-1 the “Design of ?hand loaded low rise steel static shelving’” states the following in clause 9.3.1;
9.3.1 General
Low rise shelving more than 1.6m high with a height to depth ratio exceeding 5:1 shall be fixed to the floor as defined below.
•Height is the height to the top of the frame;
•Width is the width of the single frame or, in the case of a double sided run the width may be taken as the overall width of the two frames provided that the frames are connected together with a device capable of resisting both tensile and compressive forces.
NOTE: it is noted that this limit is different to the limit in some other codes:
There are a number of companies in Europe that offer tyre racking and these designs often incorporate specially designed beams with top surfaces to match the shape of the wheels.
SEMA Rack Safety Awareness 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 held at the SEMA headquarters in Burntwood, Staffordshire, 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 has 26 publications – Codes of Practice, ‘Guides’ and European documents – all of which are available to purchase online. For further information on these documents contact SEMA or visit our website, www.sema.org.uk.
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