The material handling industry is abundant with new technologies and innovations. In the background of all this fancy new technology is a variety of less exciting, but equally important equipment, including pallet racking
With all of the moving parts of a material handling system, rack if often viewed as “just rack.” It is often the last part of a system to be considered and is usually seen as a simple piece of the puzzle. However, there are actually a multitude of different aspects that must be considered when designing and ordering pallet racking to ensure a proper fit for a material handling system. This is why it is important to allow ample time for industry experts to analyze the many aspects of a proper rack design.
The design of pallet rack systems can be broken down into (3) major elements as follows: 1) details of the product being stored; 2) physical site variables; and 3) rack design variables. This article will take a quick look at each element.
Product Being Stored
- Size and Weight of the Product – This is the most important aspect of designing pallet rack systems. Since racks are designed with a built-in safety factor, it is important not to inflate the weight of the product, which will increase the cost of the rack components.
- Type and Construction of the Pallet – Because so many types of pallets are being used, it would be inaccurate to say that there is a “standard” pallet. That said, the “typical” pallet for the US market is a 40” wide x 48” deep wood pallet with entry on all four sides and bottom boards running front to back – commonly referred to as a GMA pallet. Note the distinction between a pallet and a skid is that a skid has no bottom boards.
- Storage of Product on Pallet – If product overhangs the pallet, the racks may need to increase in width or depth to accommodate the overhang.
Physical Site Considerations
- Fire-Life-Safety – Each local government has multiple codes related to fire, life, and safety that influence the pallet racking design. Chief among them is the walk distance to exit the building in the event of a fire (i.e. “egress” distance). Rack or storage locations may need to be removed from the design to comply with the maximum egress distance. Lights and exit signs may need to be added within the rack to light the egress path. The egress path may need to be clearly marked (and possibly with reflective tape).
- Seismic Classification – The government classifies each site location by potential ground motion in the event of an earthquake. All site locations have a seismic classification, even if the potential for an earthquake is low. This is why the building address is so important.
- Concrete Floor Specifications – This is used to determine if the concrete slab can support the weight of the pallet rack and the product being stored. Depending on the strength of the concrete, larger foot plates may be required to spread the load of your pallet racking.
- Separation Requirement – This is a measure of the minimum distance between the rack and any building elements, mainly the building columns. This requirement can significantly impact the layout, especially the quantity and width of the drive aisles.
- Sprinkler Requirement – In-rack sprinklers are typically determined by the type of product being stored and by the specifications of the insurance company. If sprinklers are required, additional distance between racks and special bracing may be necessary to accommodate the pipes passing through the racks.
- Building Specific Elements – These elements include size and type of building columns; location of roof drains or other obstructions on building columns; or presence of wind bracing (aka “K-bracing”).
Pallet Racking Design
- Definitions – An upright frame (1) is constructed of two vertical columns with bracing (2) between them. Horizontal beams (3) connect the uprights together and support the pallets.
- Rack Profiles – A “profile” is a drawing that shows the distance between beam levels for each bay of rack. If there are long spans between beam levels, additional bracing may be required.
- Reinforcement – Additional bracing of the upright frame may be required and is determined by the distance between beam levels and the seismic classification. This can include bracing that is thicker, bracing that has been doubled, and a different bracing pattern that is closer together.
- Beam Design – Beam design is driven by the seismic classification which determines the size and type of connector and how the connectors are welded to the ends of the beams. The length of the beams is determined by establishing the clearances required between pallets as they are stored on the rack as well as the distance required between the pallets and the rack uprights. Typical clearances normally fall within 4” to 6”.
- Closed Tube or Open Tube – This refers to the construction of the vertical columns of the upright frames. Columns can have an open back (“open tube”) or closed back (“closed tube”). Many times the choice is customer preference, but there can be advantages of one over the other depending on the application.
- Structural Steel Racking – Structural steel may be utilized in lieu of formed steel racking, based on the application. Traditionally structural steel racking is more expensive than formed steel racking but can also provide increased load capacities if needed.
- Column Punching – the holes that are punched in the face of the vertical columns to which the beams are connected vary greatly by manufacturer. This is important in case the punching needs to match existing pallet rack.
- Pallet Racking Accessories – The most common accessories are wire decks, pallet support bars, column protectors, and end-of-aisle guarding. Please let your integrator know if these are required or desired for the application.
- Pick-Up and Drop-Off Stations – Pallet racking is typically designed with one bay removed from the end of every other row so pallets can be temporarily stored on the floor until they can be put away inside the racks. These are referred to as P&D Stations (Pick-Up and Drop-Off Stations).
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