Get on the Right Track with Push-Back Rack Carts, Wheels, & Rails

Push-Back Pallet Rack - Apex Cos.

Push-back pallet rack is a dense storage solution that combines the density of drive-in rack with the selectivity of single selective rack for high volume, multi-SKU applications. 2 to 6-deep push-back lanes consist of nested wheeled carts that flow on top of inclined rails set inside the pallet rack bay. The carts are designed to stack, or nest, one on top of the other when empty. As pallets are loaded, the forklift operator places the first pallet on the top cart. To load all subsequent pallets, the operator pushes back the front pallet load to reveal the next available cart. The last pallet loaded sits directly on the push-back rails. i.e., a 6-deep lane would have 5 carts.

Push-Back Pallet Rack - Apex Cos.Push-Back Rack Advantages

  • Ideal for high-volume, low-SKU inventory
  • Offers deep reserve pallet storage
  • Consolidates footprint – single-aisle load & pick
  • Supports LIFO stock rotation
  • Easy SKU selectivity

Push-back rack supports Last-In/First-Out (LIFO) inventory rotation and can be constructed as back to back or single rows. The system is highly effective in freezer and cold-storage facilities as well as ambient climates. It does not require special forklift equipment though it is very important to properly train forklift operators to load and unload the system.

Push-Back Pallet Rack - Apex Cos.

Let’s look at some of the major considerations that go into a push-back system design and the variations you may see from manufacturer to manufacturer.


Designing Push-Back Rack

Push-back systems are designed using structural or roll-formed pallet racking depending upon system capacity needs and inventory/application specs. The rails are constructed from either C-channel, I- beams or structural tubing.

Rail Manufacturing

  • I-beam – I-beam rails are manufactured from structural hot-rolled steel. They are used to provide strong support for heavy-duty applications. Additionally, the system can be configured with fewer frames and beams due to the I-beam support. The cart’s wheels flow on the lower flange of the I-beam while the upper flange protects the wheels from debris. One caution on the I-beam can be increased friction which slows the cart.
  • C-channel –C-channel rails are also manufactured from hot-rolled structural steel and designed for heavy-duty use and abuse-resistance. As with the I-beam, C-channels rails can create slightly more friction vs. tubing options which can slow the carts. To adjust for the friction, the incline can be increased slightly. Typical rail incline is 3/8” per foot. Good, quality wheels can also help minimize friction and ensure efficient cart flow. In a heavy-duty system, the rails are tied to front, rear, and cross beams.
  • Structural Tube – In this design, the carts sit on top of the rails. The structural tubing creates limited wheel friction which requires less pitch and a lower lane profile while ensuring steady cart flow. Additionally, less friction requires less force to push the pallets back during loading.

Push-Back Pallet Rack - Apex Cos.


Cart Manufacturing

Push-back carts are constructed from either roll-formed tube or structural angle with the design varying by manufacturer. The sides of the cart are welded to create a frame which supports the pallet. Carts are typically 4-sided, though 3-sided carts are also available. While 3-sided carts may be more affordable, they can be less durable than the 4-sided designs.

Carts can be all the same size or get progressively smaller. In either design, the carts are configured to nest together at the pick face. The forklift operator must be acutely aware of the cart size and position to accurately load the pallet. To assist the driver, carts are often color-coded so that operators can identify the pallet position as they are loading the system.

  • Roll-formed carts – cold-rolled steel tube sections
  • Structural angle carts – hot-rolled structural steel angle, used for low profile designs
  • Cart accessories
    • Pallet stops – a safety feature attached to the center of the front cross member on the bottom cart.
      • Helps forklift operators see if the lane is full – the stop is attached to the front cross member of the bottom cart which is hidden by the front pallet when the lane is full.
      • Provides a center mark to help load the carts correctly
      • Catches the bottom of the pallet during extraction if the forks are not properly tilted, allowing the driver time to adjust and protect the load from falling
      • Prevents the pallets from shifting as they flow forward in the lane
    • Backstop – the top cart can be equipped with a pallet backstop to ensure the pallet stays securely on the cart and does not shift too far back
    • Rubber bumpers – located in front of the cart to cushion the impact and reduce noise as the carts flow forward particularly important with heavy loads
    • Lift-out protectors – connect the carts to the rails to hold them in place when extracting pallets
    • Pallet catch – protruding, serrated edge(s) that grabs the bottom board and holds the pallet in place if it is not properly positioned on the cart

Cart Design for Non-Standard Pallet Loads

If you are using non-standard sized or shaped pallets, or pallets that are in poor condition, it is important to design your push-back cars to protect against falling debris and materials. Luckily, there are several effective options that can be used. Note, however, when you customize the carts, you must also make accommodation for the last pallet position. While the last pallet would normally just sit upon the rails, that spot can be equipped with a third support rail or full shelf to provide needed support.

Cart Options

  • Decked cart – carts fitted with wire deck or solid-surface steel decking to support different sizes of pallet loads and pallets without a flat bottom.
  • Wire mesh cart – carts are custom-fit with wire mesh or bar grating to provide adequate support for poor pallets
  • Extra supports – carts can be manufactured with extra left to right or front to back supports
Push-Back Pallet Rack - Apex Cos.
Metal Deck on Push-Back Carts

Push-Back Wheel Design

Push-back wheels are typically manufactured from stainless steel and are designed for rugged, long-term use. They are pre-lubricated and often pre-installed on the push-back carts. Bearings should be self-contained for protection from dirt and debris.

The wheel design and positioning are vital to the success of the system. The cart can be designed to position the wheel to sit straight (flush) on the rail surface or at a slight angle. Additionally, the wheel shape can vary from flat to tapered or flanged. Both the positioning and shape of the wheel directly affect the amount of friction between the wheel and the rail which directly affects the flow.  Here is a little more detail on different wheel options.

Wheel Shape

Flat – A flat wheel is a full-surface wheel that runs flush against the rail.  A benefit of this assembly is that it requires less force to turn the wheel and move the pallet load which reduces wear and tear on the forklift.

Tapered – A tapered wheel has rounded sides to reduce friction as it rolls. Less friction allows for smoother, faster flow.

Flanged – These wheels have a flanged edge that sit inside channel rails in order to help guide the wheel.

 

2-Deep Push-Back - Apex Cos.
2-Deep Push-Back – Cold-Storage

Push-Back Cautions – Wheels & Weights

Push-back wheels are carefully designed and lubricated to perform with little to no maintenance in a typical system. If the system is subjected to ice, lubricants, or liquids, it can impede the flow and possibly even cause the pallets to shift during flow. The system should be regularly evaluated to ensure that it is free from debris, oils, etc. to provide the safest operation.

Pallets in the lane should all be the same weights. Pallets of varying weights can cause the risk of heavier pallets pushing lighter pallets from the lane. The exception to this rule is for 2-deep case pick push-back lanes. Lower level case picking can be designed to accommodate slight pallet weight variations.

The Apex Cos. team is ready to work with you to find the best storage solution for your inventory storage and distribution needs. We’ve designed and installed many push-back systems as well as f push-back lanes within pick module systems. Let’s get started solving your warehousing challenges, give us a call today.