What Is Span Track? How Gravity Roller Tracks Work In Carton Flow

Span Track

A modular roller track used in carton flow systems to move cases or totes forward by gravity.

Span track is a lightweight, modular roller track used to create inclined gravity-flow lanes inside shelving and racking systems. Each lane consists of parallel roller strips mounted on a slight decline so that full cases or totes move forward under their own weight to the pick face. Operators load product at the rear or high end and pick from the front; when an item is removed the remaining items roll forward to maintain the pick-face. The system is simple mechanically but requires attention to lane width, roller diameter, incline, and braking to handle different package sizes and weights safely.

How Span Track Works

A span track lane is made of continuous rollers set into a frame or plastic channel. The rollers are freely turning, and the lane is mounted with a decline typically between 1° and 4° depending on case friction and weight. The momentum and speed of cartons are controlled by roller diameter, roller surface (plastic versus steel), and accessories such as speed regulators, retarder rollers, or friction brakes. Because movement is powered by gravity, electrical or mechanical drive components are unnecessary for the lane itself, lowering energy and maintenance costs.

Typical Applications

• Pick-And-Pack Systems: High-density pick lanes for fast-moving SKUs where replenishment from the rear keeps the pick-face full.
• Order Consolidation: Short flow lanes used to sequence cases into packing stations so orders are assembled FIFO.
• Reserve Storage: Back-of-rack buffering where cartons move forward to a staging point for later handling.

Design Considerations

Proper span track design starts with the SKU set and the pick environment. Key variables include roller diameter, lane width, lane incline, and end-of-lane controls. Smaller rollers reduce noise and can limit speed, while larger rollers reduce rolling resistance for heavier cases. Lane width must match the narrowest and widest cartons in a family; adjustable dividers are common to group SKUs. The decline should be enough to move the product reliably but shallow enough to avoid excessive speeds that could damage product or create safety hazards.

• Roller Diameter: Affects speed and capacity—choose larger rollers for heavy or irregular-bottom cartons.
• Lane Incline: Typically set between 1°–4°; test with the heaviest and lightest cartons expected.
• Lane Width and Guides: Use adjustable side guides to prevent skewing and to accommodate multiple SKU widths.
• Speed Control: Retarders, brake rollers, or foam inserts can control carton velocity at the pick face.

Safety And Maintenance

Span track reduces manual handling but introduces specific safety and inspection needs. Regular inspection of rollers and bearings prevents jams and sudden stops that create pinch points. End-of-lane stops and pick-face guards prevent cartons from leaving the lane accidentally. Lock-out procedures are required when performing maintenance on packed lanes, and training should emphasize keeping hands clear of roller nip points during replenishment.

• Inspection Frequency: Inspect rollers and lanes monthly for wear in high-use environments; more frequent checks in 24/7 operations.
• Housekeeping: Keep lanes free of debris that can jam rollers or change friction characteristics.
• Personal Protective Equipment: Gloves and safe-lifting techniques reduce strain when loading the high end of lanes.

Practical Example

A mid-sized ecommerce warehouse converted two shelving aisles to carton flow lanes using span track to improve picking speed on 20 fast-moving SKUs. Engineers chose 1.5" rollers, set the incline to 2°, and installed adjustable dividers so each lane handled three related SKUs. Speed-regulating rollers were added at the pick face to protect fragile items. The result was a measurable increase in picks per hour and a reduction in replenishment trips to the pick face because cases were pre-staged behind the pick position.

When Span Track Is Not Suitable

Span track is optimized for uniform cartons and totes. It performs poorly with mixed-size random cartons, very irregular-bottom containers, or packages that require powered positioning or inspection mid-lane. For full-pallet flows or heavy unit loads, pallet flow systems with rollers sized and rated for pallet weights are more appropriate. If FIFO sequencing with precise control is required (e.g., date-sensitive pharmaceuticals), consider powered conveyors or automated flow modules with sensors.

Installation Tips

• Pilot Test: Install a short test run with the heaviest and lightest cartons to validate incline and speed controls before rolling out across aisles.
• Modularity: Keep sections modular so lanes can be reconfigured when SKU profiles change.
• Integration With WMS/WCS: Use your warehouse management or control system to reserve lanes for specific SKUs and to track replenishment triggers.

In short, the Span Track is a cost-effective, low-maintenance element for carton flow that increases pick-face density and supports FIFO picking when designed for the SKU set and integrated with safe operating procedures.