Inspection conveyor: requirements and layout
How to design an inspection conveyor: lighting, height, belt speed, operator workplace ergonomics. We break down requirements for sorting equipment.
An inspection conveyor is a workplace disguised as a transporter. Its job is not just to move product but to create conditions in which an operator notices every defect throughout an eight-hour shift. If the lighting is weak, the speed too high and the belt height awkward, the share of missed defects rises sharply. This article breaks down how we design an inspection conveyor.
Lighting: the main inspection parameter
Sorting quality depends 90% on light. The eye tires from uneven lighting and glare, so above the inspection zone we install LED luminaires with a diffuser. The norm for most food products is 800–1000 lux on the belt surface; for delicate inspection (detecting small spots, larvae, darkening) up to 1500 lux. Colour temperature is neutral, 4000–5000 K: warm light distorts the product’s natural colour, while cold light tires the eyes.
We position luminaires so the operator does not see the light source directly and no shadows fall from hands. For some tasks we add backlighting through a translucent belt — this shows foreign bodies in high contrast.
The belt colour also affects inspection quality. For light products we choose a dark or blue belt, for dark ones a light belt: contrast between product and background helps the eye pick out a defect faster. Blue is additionally useful because it hardly occurs in the nature of food products, so any stray belt fragment on the product is immediately noticeable.
Operator workplace ergonomics
The operator stands or sits by the belt for hours, so the conveyor is designed around the person. Key parameters:
- Working surface height — 850–950 mm for standing work, adjustable to operator height.
- Belt width — 400–800 mm; a wider belt forces reaching, which tires the back.
- Reach depth — the operator should reach the far edge of the belt without bending the torso.
- Reject trays — at hand level, on both sides of the belt, to avoid turning the whole body.
- Footrests and mats — reduce fatigue during standing work.
Belt speed and throughput
Speed is a compromise between throughput and quality. A too-fast belt prevents the eye from fixing a defect, a too-slow one cuts capacity. Below are the benchmarks we design for.
| Product | Belt speed | Belt loading | Operators per 1 m |
|---|---|---|---|
| Berries, small fruit | 0.05–0.10 m/s | single layer, 50–60% | 2 |
| Vegetables (potato, carrot) | 0.10–0.15 m/s | single layer, 60–70% | 1–2 |
| Nuts, kernel | 0.08–0.12 m/s | thin even layer | 2 |
| Packaged goods | 0.15–0.25 m/s | one by one with a gap | 1 |
Engineer’s tip. Product on an inspection belt must lie in a single layer and not fully cover the width. If the product lies in a heap or a dense mat, the operator physically cannot see what is underneath. A wider belt with low loading beats a narrow overloaded one.
Layout: roller vs belt
The classic inspection conveyor is belt-type, but for round products (potatoes, onions, citrus) a roller type is more effective. The rotating rollers turn the product so the operator sees it from all sides — a defect on the underside cannot hide. We design such solutions in the custom equipment section. For flat and delicate products we choose the belt option from the range of conveyors.
Hygiene and materials
An inspection conveyor sits in the open-product zone, so all contact surfaces are stainless steel AISI 304 and the belt is a food polymer certified to EU 1935/2004. We design the structure without stagnation zones, with drainage slopes and the ability to clean without disassembly. Reject trays are made removable for easy cleaning.
We separately plan the handling of the rejected flow. Removed defects and waste have to go somewhere — for this, collection bins or a removal conveyor are placed under the trays. If this is not provided for, rejected product accumulates at the workplace, hinders the operator and creates a hygiene problem. So we always design the inspection module together with waste logistics, not just as a “belt with light”.
Organising shift work
Quality inspection is also a matter of the work regime. The operator’s attention tires: after 45–60 minutes of continuous inspection the share of missed defects rises. So on lines with high quality requirements we, together with the customer, plan operator rotation and breaks. The conveyor is designed so an operator can be replaced without stopping the line, and the workplaces are interchangeable. This is an organisational decision, but it must be taken into account at the layout stage — for example, providing enough room for staff changeover and convenient access to each position.
Conclusion
An inspection conveyor is the engineering of attention: correct light, comfortable height, moderate speed and a single-layer product flow. An error in any of these parameters means missed defects and complaints. If you need an inspection conveyor for a specific product, get in touch — we’ll design the workplaces and layout for your sorting line.
