Pallet rack is to a warehouse as a skeleton is to a body. Both provide structure and support to an overall entity. And, if part of either is broken, it’s very painful….. Modern Materials Handling 2/1/2011
WHAT PALLET RACK SYSTEM IS RIGHT FOR YOU?
- Selective Rack
- Double Deep Rack
- Drive in & Drive Through Rack
- Gravity Flow Rack
- Push Back Rack
Selective pallet rack is the most common type of pallet storage. Selective rack uses uprights and a pair of cross beams to create a “shelf” for storing a pallet. Depending on the height of your pallet and ceiling height that will determine the number of levels (shelves) per bay.
Drive-in racking is a type of storage system that allows fork trucks to drive directly into a bay. Pallets rest on side rails rather than cross beams, which leaves the face of the bay open. The uprights are typically tied together at the top of the upright to add rigidity to the system. The only difference between drive-in and drive-through racks is whether there is an entrance at only one end (drive-in) or both ends (drive-through).
This style of rack is commonly 6-8 pallets deep per bay. Fork trucks elevate a load to the proper level and load it in the back of the system first. The second pallet will be placed in the second position from the back and continue until a lane is full. Drive-in racks are LIFO, while drive-through racks are typically FIFO. This type of system is best suited for storing a large quantity of pallets of the same product.
DOUBLE DEEP RACK:
Double-deep rack stores one pallet load behind another in a structure that’s twice as deep as selective rack. Double deep rack doubles storage, but it limits access and flexibility.
To access the rear pallet load, the front pallet position must be empty. Double handling is necessary unless pallets are stored on a last-in/first-out basis. In most cases, two pallets with the same product are stored in a slot of a double-deep rack, which limits flexibility and requires a deep-reach lift truck to access loads in the rear position.
DRIVE IN RACK:
Drive-in rack can be configured to store loads four or more deep, creating very dense storage. For example, a drive-in system that stores pallets four high and five deep can hold 20 pallet loads in each bay.
In a drive-in system, lift trucks drive into the front of a storage bay, place a load in the designated position then back out. The rack is designed without traditional beams across the bays so lift trucks can maneuver in and out. Instead, pallets rest on rails that run along the inside of the bay, perpendicular to the aisles.
Pallets are stored on a last-in/first-out basis. Each bay is typically dedicated to a single product, so drive-in rack is best used for storing large quantities of the same product. They work well where an entire bay of product is moved at once, such as in staging product for shipping.
GRAVITY FLOW RACK:
Gravity flow rack combines a stationary rack structure with skate wheel or roller conveyor to create a dynamic storage system. Pallets are loaded into the back end of the rack then travel down the slightly inclined lane of conveyor so they can be retrieved from the front of the system.
Flow rack systems provide high-density storage by storing product many pallets deep. Because each layer of flow rack is typically dedicated to a single product, these systems offer less storage flexibility than selective rack but more than drive-in or drive-through.
This is a good option for storing dated products because it allows easy rotation of inventory on a first-in/first-out basis. It can be used for picking by the piece, carton or pallet. Carton flow rack that stores individual cartons are also available from many manufacturers.
Push-back rack combines a stationary rack structure with nested carts that move along inclined rails. The first pallet, which is loaded from the front, is placed on top of the cart. When the second pallet is loaded, it pushes back the first pallet, exposing the second cart, and so on.
Usually configured two to five pallets deep, these systems offer dense storage. Like flow rack, push-back rack does not require a lift truck to enter the racking structure or require an entire bay to be dedicated to one product. Unlike flow-rack, however, push-back rack manages inventory on a last-in/first-out basis and requires less space than flow-rack because rear access is not necessary.