Is there a point when single-wide pallet flow bays are a better choice than double-wide? The simple answer is, Yes.
While the answer itself is simple, the explanation has some complexity. That’s why Mallard Best Practices is back to breakdown this topic and help you make the best choice for your system design.
How Wide is Cost-Effective Pallet Flow?
Pallet flow rack is a dynamic pallet storage solution meaning that the pallets are in movement for at least part of the time spent in the storage rack. Most often pallet flow is designed as a first-in/first-out (FIFO) storage solution whereby the pallets are loaded from a rear aisle and flow down on inclined rails to the opposite aisle for extraction. The rails are comprised of wheels or rollers and they are secured to the pallet rack front and rear cross beams. The pallet movement must be very precise and controlled to ensure that the inventory arrives safely and squared with the pick face for quick, easy extraction.
For a single-wide pallet flow lane, the cross beams only support the weight of that single lane. Conversely, a double-wide lane means two separate pallet flow lanes are being supported by the front and rear cross-beams, and therefore, the weight is being distributed across a wider span. To provide the system stability required, more supports will be needed for the double-wide lane vs the single-wide lane.
Now, you may be thinking that the single lane pallet flow bay is more expensive than a double bay, and we understand why. Single-wide bays require more uprights, therefore, with more steel, there’s a heftier cost. Trust us, that isn’t the case. The Mallard team has done the math, and despite the fact that a single lane bay requires more uprights, the beams and uprights can be lighter due to lower load capacity. In the end, the lighter system is less costly than the beefy system and the pallet storage capacity is the same.
Pallet Flow – Zero Tolerance for Deflection
Additionally, a pallet rack bay in a static rack system, such as selective rack, has an allowable deflection that cannot exceed the length of the beam (L) divided by 180, in other words, up to .55″ or ½” of sag is allowable over a typical 8’ cross beam span. While this small amount of sag is permitted and considered safe in a static rack system, a pallet flow system is very different and does not allow for ANY beam deflection.
The movement of the pallet is critical in a gravity flow system. The pallet must flow centered within the lane. If the cross beams sag downward in the center, the pallets would be drawn to the center of the bay and not track properly, likely getting stuck or crossing over to the adjacent lane. For this reason, and cost to reinforce the lane, deep-lane pallet flow is almost always single-wide. A good rule of thumb is to limit double-wide pallet flow to 5-deep or less.
While double-wide bays can be a cost-effective option in shallow-depth lanes, they are not an option for pallet loads >1500 lbs. For these heavier loads, it is more economical to go to single-wide because, again, the reinforcements required to shore up the heavier pallets and ensure zero deflection would cost more overall than if you simply design the lane as a single.
If you have system design questions or would like the Mallard engineers to test your inventory you’re your pallet flow design, contact our team. Our gravity flow experts are available to help you find the most productive and cost-effective solution to your warehousing challenges.