Safety and Efficiency in Very Narrow Aisles

Dense storage systems are very much part of the modern world of logistics. For their safe and efficient operation, they depend on the interaction of three elements - the racking, the trucks and the floor. In technical terms, the racking and trucks are perceived as being highly engineered, and the trucks in particular have become very sophisticated. Floors however are often misunderstood and neglected.

Reasons for this are many and varied. Often buildings are completed before the storage scheme for them is finalised. Other reasons include the floor never being surveyed, data from the survey is missing or unavailable for the user, incorrect tolerances were used in the survey, and exceptional measurements or allowances are taken as the required norm. The end result is an inadequate floor - this creates unsafe and inefficient operations in the warehouse, and inefficiency costs money.

Fortunately, things are about to change. Thanks to a UK initiative through SEMA, a European standard for warehouse floors used with racking is being developed. SEMA is making sure that all of the factors are being considered, not least, the interaction between the trucks and the floor and the effect this has on the truck/racking interface. BITA, The British Industrial Truck Association, is represented on the working group. There is also close liaison with The Concrete Society, which publishes the floor design and construction guidance in the UK - better known as TR34.

Within TR34 there are two sections on floor flatness: The first is for free movement areas typically found in warehouses with wide aisle racking systems. The second is Appendix C, which deals specifically with the aisles within a VNA system – known as defined movement areas.

Contract managers and engineers are used to providing suppliers and sub contractors with specifications for materials and work. Specifications invariably provide performance requirements for a range of parameters with measurements or tolerances being the most common. For floors, TR34 sets out the requirements in clear terms with little room for confusion and is therefore cited as the required standard. All too often, flatness is then forgotten about, with potentially damaging effects on the client.

On a new build VNA scheme, satisfactory floor flatness can be achieved as follows:

1. Specify the VNA truck - of particular relevance is working aisle width, maximum lift height and wheel configuration.
2. Design and define the racking scheme, particularly the position of the aisles and determine the floor loading through the rack base plates.
3. Design and specify the floor, determine the position of the floor joints (avoiding longitudinal joints down narrow aisles), and determine and specify the relevant floor flatness category to TR34.
4. Use a specialist contractor to construct the floor.
5. 5nstall the rack.
6. Survey the flatness of the constructed floor (particularly down every narrow aisle), and check against the requirements of the specified category in TR34.
7. Locally grind where necessary.
8. Re-survey any ground areas and check the results against TR34.

It is likely that CEN will adopt similar classifications as TR34 with three grades of floor in each of the free and defined movement groups. Within each group, the grade of floor will be determined by the top beam height of the racking. If we can be sure that the flooring industry can reliably deliver these grades of floor, then specifiers will be able to design for optimised efficiency and safety.