Drag Conveyors
Drag conveyors (also known as “En-Masse”, drag-chain or scrapper flight conveyors) are available in
flat-bottom and round bottom styles. Flat bottom styles tend to be a more heavy duty, industrial grade
(for aggregates, biomass, cement or coal), whereas, round bottom units are usually considered to be
lighter duty, commercial grade (grain handling) units. The fact that we offer both allows us to match
your requirements with the most cost effective option; in other words our conveyors are, “Engineered
for the Project”.
All drag conveyors utilize scraper-style flights that are attached to either a single strand or dual
strands of chain and they all move product more-or-less “En-Masse”. The exception to the scraper-style
flight is the reclaimer (or “under pile reclaimer”) style of conveyors, which utilize a special “welded
drag chain” that may, or may not have wing-style extensions welded to the side bars. WDH110 (6” pitch x
10” wide) and WDH480 (8” pitch x 12 3/4” wide) are two common reclaimer chains and they are frequently
arranged to have two or more strands side-by-side in a common housing with common drive and tail
shafts.
Most drag conveyors are used transfer bulk materials from one point to another and their inherent
efficiency allows them to do so at up to 50% less motor power than a comparable screw conveyor.
However, when properly designed, a drag conveyor can function reasonably well as a “feeder”, regulating
the withdrawal of material from some static storage vessel or surge bin. However, they will not be as
effective as a screw feeder or live-bottom feeder at achieving a uniform draw-down from the bin.
A major advantage of a drag conveyor is the ability to convey in more than one plane with a single
unit, for example; you can move material on a horizontal plane, then a bend upwards (up to 90°) on a
vertical plane and then back to horizontal. Doing this with convention screw conveyors and a bucket
elevator would require at least three separate pieces of equipment, each with its own drive, plus the
transfer points. A configuration starting with a horizontal section and then an inclined section is
called an “L-Path” conveyor; add a second bend back to horizontal and it is called an “S-Path”
conveyor.
Advantages
- More self-cleaning, less cross contamination
- Gentle handling of fragile materials
- Less power required than screw conveyor
- More efficient on an incline
- Can incorporate a vertical bend
- Greater length potential
- Lighter per-foot weight than screw conveyor
Limitations
- Sticky materials adhere to flights and chain
- Can’t mix or blend while conveying
- Extremely abrasive materials will damage chain
- Don’t uniformly draw-down from a long bin
- Hard to make “sanitary” for food handling
TPI Engineered Systems is based in Atlanta, Georgia; serving as the premier designer, engineer,
manufacturer, and installer of custom bulk materials conveyor systems all across the United States. For
more information on any of the TPI Systems, call 804-232-4580 to speak to one of our knowledgeable and
highly experienced employees.
