Screw Conveyors or Screw Feeders
Screw conveyors and screw feeders are very simple machines, yet they are probably the least
understood, most disliked and highest maintenance pieces of bulk material handling equipment in most
plants. Generally, they are considered as a “necessary evil” and tolerated only because there is no
better way to do the job.
There are literally thousands of possible combinations of screw conveyor parts, when you factor in all
of the different types, styles and material thickness options that are available. Out of those, there
may be a hundred combinations that will physically work on any given application, but may result in
poor reliability, high maintenance or excessive down time. With these facts in mind, there are two
things to remember:
- There’s a big difference between having 20 years of experience, and having 2 years of experience
ten times.
- You don’t know what you don’t know.
Our combined 150+ years of hands-on experience in a wide range of industries and applications gives
us the ability to select the proper combination of screw type, trough style, hanger style, material
type, material thicknesses, and inlet and discharge configuration and so on to make your application a
success.
Screw Feeders and Live-Bottom Feeders can be very effective at providing a reliable and repeatable
discharge rate from a storage vessel or surge bin. Also, when properly designed, they can provide for a
very uniform draw-down across the entire length of the bin discharge, which is valuable for preventing
stagnant areas within the bin where material becomes trapped. Our systems ensure your material is
processed uniformly; in other words, first-in and-first-out.
Some common methods for achieving a uniform draw-down are short pitch, variable pitch, stepped pitch,
tapered flights and cone screw technology. Unfortunately, some of these procedures do not work well in
specific applications and can, in some instances, make matters much worse, which is why you need to
work with experienced people.
Advantages
- Extremely versatile
- Totally enclosed dust and weather tight
- Can mix and convey simultaneously
- Convey simultaneously in two directions
- Readily reversible without a soft start
- Can be flood loaded simultaneously at multiple inlet locations
- High temperature materials (1000° +)
Limitations
- Harsh handling of fragile materials
- Higher power requirements
- Less potential length
- Cross contamination; not self-cleaning
- Maintenance more difficult
- Large spare parts inventory required
- Higher initial cost
This information is basic guidance in selecting an appropriate screw conveyor and has been excerpted
from the book entitled, Screw
Conveyors 101 and is authored by Mike Forcade, a member of our staff.
Another possible solution is a “Shaftless Screw”, which uses a very heavy flight, but no center pipe.
This option works well on materials that tend to stick and build up, as it would where the conventional
flights meet a center pipe; sewage sludge, for example, or on materials that have lumps that are too
large for the radial clearance of a conventional screw; hog heads and large cow bones would be a good
example.
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 our Bulk Material Handling products or services, call or click to schedule a free
consultation with one of our highly experienced employees.
