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Shafted Screw Conveyors vs Shaftless Screw Conveyors

07
Jan, 2018
By Greg Hyde
Shafted Screw Conveyors vs Shaftless Screw Conveyors
  • Learning Center,Material Handling Systems,Product Comparison,Screw Conveyors
  • 2 comments

Over the years, the use of screw conveyors in municipal wastewater plants has been popular for a combination of reasons. The full enclosure of the screw conveyor helps with two big housekeeping issues at the wastewater treatment plant; spilling of materials and odor control. Another reason many plants use screw conveyors is their compact design. The compact design allows for their use in tight and congested areas of the plants. In addition to this, their ability to handle a wide variety of materials also makes them a good choice.

One question that a lot of engineers and plant people ask about screw conveyors is: “when should I use a shafted screw conveyor” or “when should I use a shaftless screw conveyor”? These are great questions and the answer should be investigated for each individual operation as they assess their day to day needs.

JMS Bio-SCREW (Screw Conveyor system) shafted screw
Shafted Screw Conveyor
JMS Bio-SCREW (Screw Conveyor system) shafless screw
Shaftless Screw Conveyor

 

Why use shafted screw conveyors?

JMS Bio-SCREW Shafted Screw Conveyors

A shafted screw conveyor is a screw conveyor that has a solid shaft that goes through the flighting of the screw. This helps hold the flighting off of the bottom of the trough.

Pros of a shafted screw conveyor:

  • A shafted screw conveyor can be a longer length. In most applications, the shafted screw conveyor uses hanger bearings every 10-12 feet.
  • A shafted screw conveyor has no need for a liner which results in less maintenance.
  • A shafted screw conveyor can run at higher rpms because there is no concern about liner wear.

Cons of a shafted screw conveyor:

  • The need of hanger bearings for longer conveyors. These may obstruct material flow in high capacity conveyors.
  • Shafted screw conveyors have a lower fill rate due to the need for hanger bearings. The usual fill rate for a shafted screw is around 15%-30%.
  • Shafted screws are not suited for stringy materials like screenings.
  • Shafted screw conveyors may have a higher capital cost in certain situations with flanged shafts and flexible hanger bearings.

Why use shaftless screw conveyors?

JMS Bio-SCREW (Shafltess Screw Conveyors)

A shaftless screw conveyor has only a spiral or helix without a center shaft. The screw then rides on a liner which is typically made from ultra-high molecular weight Polyethylene material. The only connection point in a shaftless screw conveyor is at the drive end of the screw conveyor.

Pros of a shaftless screw conveyor:

  • One of the main reason to use a shaftless conveyor is the ability to handle different type of material. Shaftless screw conveyors can convey stingy, sticky, wet, and lumpy materials.
  • Without the need for hanger bearings a shaftless conveyor can have a higher fill rate at closer to 35%-40%. For applications such as live bottom hoppers, and metered feed, it is possible to run a shaftless screw conveyor at 100%.
  • Shaftless screw conveyors are ideal for pulling vertical conveyors since there is not a bottom shaft or seal.

Cons of a shaftless screw conveyor:

  • A Shaftless conveyor is going to need the liner removed and replaced since it is a wear item. This can often be an issue if the screw conveyor is located high up or in a tight location.
  • For longer runs and higher volume applications, there will be the need for reinforcements on the screw, due to the compression of the spiral under pushing load, and elongation under pulling load.

Conclusion on Shafted Screw Conveyors vs Shaftless Screw Conveyors

Screw Conveyors are a standard ”go to” in wastewater treatment plants in both shafted and shaftless forms. Both designs have their pros and cons, and the final choice typically comes down to what material the screw conveyor conveying, and owner preference. Below is a chart for quick reference to choose between a shafted and shaftless screw conveyors depending on the material being conveyed.

Shafted screw conveyors vs shaftless screw conveyors chart

Click this Image to see the JMS Shafted vs Shaftless Screw Conveyor Chart

About Greg Hyde

Greg Hyde joined the JMS Sales and Marketing Team as Product Manager | Material Handling. Greg has over 30 years of experience in material handling systems, having held high level engineering, sales and business management positions with large full line conveyor manufacturers. He is responsible for overall support and growth of the JMS Bio-HANDLING product line. Outside of work, Greg is a founding member of the “Jammin’ 4 Water” (Water Charities Fundraising Inc.). In regards to his position, Greg says, “ JMS has a rich history in design, quality and material handling. I’m excited to be part of this great team and look forward to guiding the Bio-HANDLING product family for long-term growth.”

2 Comments

  • By Juan Sabio

    Hi,
    I am actually working in Brazil in a project that we need a conveyor system, handling 25 ton/hour of hot (180°- 220° C) Soderberg electrode carbon paste mass (petroleum coke and pitch) from the mixer to an extruder. The first 2.5 – 3 meters the convey is horizontal then the next 3.5- 4 meter should inclined 75 – 90 ° angle inclination to feed the extruder

  • By JMS

    Hello,

    I have given your contact info to our sales team and someone should be in touch with you. If not you can reach out to our team at sales@jmsequipment.com

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