Overhead conveyors move materials through a warehouse using rails, carriers, trolleys, or hooks suspended above the floor. They matter because they use vertical space that would otherwise be empty, leaving floor aisles open for workers, robots, and forklifts. In fulfillment centers, they can connect receiving, storage, picking, packing, sorting, and shipping zones with a steady flow of goods.
A well designed system reduces travel time, limits manual lifting, and helps keep orders moving predictably.
Key Facts
- Conveyor throughput can be estimated by Q = v / s, where Q is carriers per second, v is chain speed, and s is spacing between carriers.
- If each carrier holds mass m, mass flow rate is ṁ = Qm.
- Required lift power can be estimated by P = mgh / t for raising goods of mass m through height h in time t.
- Motor power for horizontal motion is often estimated by P = Fv, where F is the total resisting force and v is conveyor speed.
- Minimum carrier spacing must allow for item length, stopping distance, and safe clearance at switches and curves.
- Diverters and switches route carriers between zones, so their control timing strongly affects congestion and sorting accuracy.
Vocabulary
- Overhead conveyor
- A suspended transport system that moves carriers, hooks, or trolleys along rails above the warehouse floor.
- Carrier
- The moving support that holds an item, tote, garment, or container as it travels through the conveyor system.
- Diverter
- A mechanical or electromechanical device that changes a carrier from one rail path to another.
- Throughput
- The rate at which items or carriers pass through a system, usually measured in items per hour or carriers per minute.
- Accumulation zone
- A section of conveyor where carriers can wait temporarily without stopping the entire system.
Common Mistakes to Avoid
- Ignoring carrier spacing, which is wrong because spacing controls throughput, collision risk, and the ability to merge or divert safely.
- Using average demand only, which is wrong because warehouse systems must handle peak order periods and temporary backups.
- Treating all loads as identical, which is wrong because different masses, shapes, and centers of gravity change motor load and carrier stability.
- Placing switches too close together, which is wrong because carriers need enough time and distance for detection, decision making, and mechanical movement.
Practice Questions
- 1 An overhead conveyor moves at 0.8 m/s and carriers are spaced 2.0 m apart. What is the throughput in carriers per minute?
- 2 A system lifts 50 kg of goods through a height of 4 m in 20 s. Ignoring losses, what minimum power is required? Use g = 9.8 m/s^2.
- 3 A warehouse can install an overhead conveyor or add more floor carts. Explain two reasons the overhead conveyor might improve workflow, and one situation where it might not be the best choice.