Double the Volume: Tubular Drag Conveyors

Coffee roasters and processors have long sought a means to convey valuable product with less breakage, spillage, and contamination risk. Although tubular drag conveyors have offered these desired attributes compared to alternative systems, many in the industry have selected more traditional options to move higher volumes.

Now, however, 8” diameter tubular drag conveyors have become widely available that essentially double the volumes of smaller 6” units. Today, 8” tubular drag cable conveyors can move up to 2,000 Ft³ and 80,000 pounds per hour depending on the bulk density of materials. This provides comparable volumes and pricing to conventional industrial systems.

Product Quality

Since coffee beans and ground coffee are delicate and present a higher value in undamaged form, preserving product integrity is important. However, the rough mechanical action of scooping/dumping product from buckets can cause incidental damage, lowering value. So can the high-velocity conveyance of pneumatic systems through vertical/horizontal tubing, turns, and sweeps, which can damage product during the process.

In contrast, tubular cable conveyors offer a gentler alternative. When the systems move product through a sealed tube using a coated, flexible stainless-steel drag cable pulled through on a loop, the solid circular discs attached to the cable push the product at low speed through the tube without the use of air, preserving product integrity and minimizing waste. These conveyors excel in transporting delicate coffee beans and precise blends in versatile layouts and configurations.

Product Preservation

Enclosed conveyors prevent the product loss intrinsic to open systems. Once the coffee is in the enclosed tube, it cannot fall out, and no product is lost in the form of escaped dust.

Preventing product loss can offer considerable benefits to the coffee processor’s profitability, with surprisingly quick ROI in some cases.


Open systems like bucket elevators and belt conveyors are common but pose contamination risk. With either of these systems, any product that is uncovered can potentially expose it to contaminants and moisture in the surrounding environment. Open systems also allow product spillage onto the plant floor, which can present a slip and fall hazard if not promptly addressed.

Unlike open systems, closed systems like tubular drag cable conveyors effectively seal off product from the outside environment and any potential contamination from that source. The enclosed nature of the systems ensures no dust escapes that could lead to a potentially hazardous dust coating on the floor or process equipment. The result is a safer, cleaner, dust-free work environment and reduced risk of dust explosions if the product is in ground or powdered form.

The enclosed systems also eliminate the risk of slip and fall incidents due to product discharge onto the processing floor.
Coffee roasters will do well to consider 8” systems that can double the coffee volume processed compared to 6” units, while safely, gently conveying product.

by Karl Seidel

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