http://www.documentbays.org/89985-bs-en-15620-2008.html

3.17reference directionsdirections at 90° to each other related to the orientation of the rackingNOTE The reference directions X, Y and Z are defined in Figure 1. X is the down aisle direction, Y is the verticaldirection and Z is the cross aisle direction.3.18single deep rackingpallet racking where there is only a single run of unit loads each side of the aisle, which is served by thehandling equipment in that aisle3.19specificationdetailed description of the user’s requirements including the racking specification and other data such as theambient storage conditions, the floor construction, local authority requirements, etc., including all detailsaffecting either the design of the installation or its construction3.20specifierperson or company that provides the supplier with a specification based on the user’s requirementsNOTE The specifier may be a consultant, other specialist, the user or the equipment supplier acting as the specifier.3.21stacker cranea storage and retrieval machine running on a rail and stabilised at the top of the mast by an upper guide rail

suppliercompany that supplies the storage equipmentNOTE The Company may be the original manufacturer or an intermediate company acting as a distributor.3.23tolerancesdimensional variations from the nominal dimension or position arising from manufacture, assembly anderection of handling and storage equipment and other aspects of their environment that may affect the systemsuch as the building, the unit load and the concrete floor3.24usercompany or person who manages and operates the installation on a daily basis and is responsible for thecontinuing safety of the installation3.25very narrow aisleVNAaisle of a width to cater only for the truck and the unit load width plus an operational clearance where the truckcannot make 90° turns into the rack face for loading and off loading4 Racking classes4.1 GeneralErection tolerances, deformations and clearances have been divided into four groups to cover the generalrequirements of the four groups of handling equipment. The racking for each classification requires a differentstandard of installation tolerances, deformations and minimum clearances for safe operation. See Annex B formore information on general safety philosophy.4.2 Class 100, Stacker cranePallet racking arranged as for a very narrow aisle system but operated by a stacker crane. The aisles are wideenough only for the stacker crane or load width plus operational clearance as shown in Figure 4.