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Comparing Gravity Flow Rack Types

picking totes from flow rackWalk into any order fulfillment operation, and you’re probably going to see gravity flow rack.

The reason is obvious–it’s one of the best ways to pick orders utilizing first-in, first-out principles. It used to be that there was one kind of the stuff, the plastic-wheel tracks, but these days the choices are more diverse than ever. For the most part, these flow rack types act the same; they decline toward the picker and boxes or totes or even larger components flow toward him. They’re restocked from the rear and picked from the front onto a takeaway conveyor line, a cart, workstation, or another step in the process.

  • carton flow racks - with span trackThe most dominant type in recent years has been Span Track and other carton flow tracks. It has risen to prominence because it has such versatility and utility. You can turn any rack bay into flow storage with it. Warehouse managers like that because they can use their existing rack and still have pallet storage above the flow storage. It’s also durable stuff: full width rollers rather than flow wheel lanes. These are still lanes, in essence, but they tend to offer more flexibility than roll tracks. They’re more durable, as well, and lots easier to replace in the event of damage.

I’ve seen them used to hold the typical cartons or totes, but also a variety of other things, including car seats (for an automotive Tier one supplier), larger shipping bins, solid components, finished goods, etc. In general, you can expect your products to stay within a lane system with flow tracks, although it’s easy enough to do some things with larger loads that might cross tracks and be held on multiple tracks at the same time.

Carton flow tracks are even more diverse…you can get them in high profile (those rest above the beam), low profile (these nest between rack beams), and “deck” that are mostly used as drop-in, single-deep storage. Moreover, they are being used in preconfigured racks these days, such as Stationary Carton Flow Rack and Mobile Carton flow racking. We used them to create standardized pallet + carton flow picking modules. No doubt – it’s versatile stuff.

  • The most difference between the flow storage types are gravity skatewheel flow racks. They’re heavy-duty gravity racks that use full-strength skatewheel conveyor sections rather than flow track rails or wheel tracks. These are a completely different animal for a couple of reasons.

Gravity skatewheel flow rackThe first is versatility. These racks become a “shelf” of flow. No matter how wide your rack is, every inch of the between-beam space is live flow storage. There are no lanes. So you can put a variety of different things on the same shelf in the same rack and it’ll flow. You can grab a tote and move it “cross-lane”. You’re not restricted. Now, if your load is consistently the same, you may not need this kind of versatility.

The second is capacity. They’re used a lot in assembly and manufacturing because they can be very strong. Also, you can get pretty narrow with them–as little as 24″ wide for a single conveyor section of flow. Not every flow rack type offers that kind of size selectivity. These are more specialized than the other types, but when you want the versatility, or you need the capacity, they are an excellent solution.

  • Wheel Track type racks were the first true mass-market flow rack, and plenty of them are in use and working great. They are the old standby. This design uses inclined shelves equipped with roll track to move cartons by gravity from the restocking to the picking side of the system.

Plastic wheel gravity flow racksThey can be less expensive than the alternatives, and better for lighter, very consistent loads that do not change over time. Since the racks are designed from the ground up to be flow racks, you aren’t using pallet rack to support flow storage. We use them a lot in distribution applications where the load is predictable and consistent.

In the final analysis, your application will decide what rack works the best for you. There are more types than these, but most applications will start here and work forward.

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Scott Stone Cisco-Eagle's Director of Marketing. He has over 25 years of experience in the industry.