Spiral conveyors move cartons, totes, and parcels up or down between warehouse levels using a compact rotating or belt-driven path. They matter because vertical movement is often a bottleneck in fulfillment centers, especially where floor space is limited. By wrapping the travel path into a helix, a spiral conveyor can connect mezzanines, sortation lines, packing areas, and shipping docks in a small footprint.
This makes it a key machine in modern logistics automation.
Key Facts
- Vertical rise per turn: h = p, where p is the helix pitch.
- Approximate path length per turn: L = sqrt((2πr)^2 + p^2).
- Throughput estimate: items per hour = 3600 / time gap in seconds.
- Power for lifting: P = mgh / t, not including friction and motor losses.
- Efficiency relation: P_input = P_output / η.
- Gentle handling requires controlled speed, stable spacing, and enough friction to prevent sliding.
Vocabulary
- Spiral conveyor
- A conveyor system that moves items along a helical path to raise or lower them between levels.
- Pitch
- The vertical height gained or lost during one complete turn of the spiral path.
- Throughput
- The number of items a conveyor system can move in a given amount of time, often measured in items per hour.
- Coefficient of friction
- A number that describes how strongly two surfaces resist sliding against each other.
- Accumulation
- The controlled holding of items on a conveyor so downstream equipment can catch up without stopping the entire system.
Common Mistakes to Avoid
- Confusing vertical height with travel distance, which is wrong because a carton moves along the longer spiral path, not straight upward.
- Ignoring friction and motor efficiency, which is wrong because real conveyors need more input power than the ideal lifting energy mgh.
- Using average speed without checking item spacing, which is wrong because high belt speed can still give low throughput if gaps between parcels are large.
- Assuming every load is stable on a spiral, which is wrong because tall, heavy, or poorly centered cartons may tip or slide if speed and incline are not controlled.
Practice Questions
- 1 A spiral conveyor raises a 12 kg tote by 5.0 m in 20 s. What is the ideal lifting power in watts, using g = 9.8 m/s^2?
- 2 A spiral has radius 1.2 m and pitch 0.80 m per turn. Estimate the path length for one full turn using L = sqrt((2πr)^2 + p^2).
- 3 A warehouse must choose between a vertical lift and a spiral conveyor for moving fragile parcels between two levels. Explain why the spiral conveyor may provide smoother continuous flow, and name one design factor that helps prevent parcel damage.