# Thread: Capacity Calculation for a Double Screw Conveyor

1. ## Capacity calculation for a double screw conveyer

dear professionals ,

i am working on designing a screw conveyor
i would like to know about the decision factors for selecting the pitch,width , thickness of the screw conveyor & dia of the shaft .

secondly what is meant by trough filling factor
thanking you

regards
sachin

2. DEAR SACHIN,

FOR SELECTION OF DOUBLE SCREW CONVEYOR,WE SHOULD
KNOW THE FOLLOWING:-
1) MATERIAL TO BE HANDLED
2) CAPACITY
3) MATERIAL CHARACTERSTICS
4) LENGTH OF SCREW CONVEYOR

THE FILLING FACTOR WILL BE SELECTED BASED ON THE MATERIAL
TO BE CONVEYED AND ITS CHARACTERSTICS ETC. OR IN OTHER WORDS HOW MUCH MATERIAL IS FILLED IN THE TROUGH.

THANKS

3. Dear Shri Sachin,

The selection of particular type of screw conveyor is a big subject and cannot be narrated here. Firstly, I would like to draw your attention to the following variants of the screw conveyor in context of the points you have referred.
- Regular pitch screw conveyor
- Regular pitch double type screw conveyor
- Short pitch screw conveyor
- Short pitch double flight screw conveyor
The above mentions only certain types with respect to conveying. Of course there are also different versions such ribbon flight, pedal flight, etc. for specific function, other than just conveying.

As for the use of particular type in context of pitch and number of flights, I can mention only certain hints as below about their functional characteristics.
- Shorter pitch imparts more powerful push to the material (wedge principal or tightening screw having less helix angle).
- Shorter pitch or double flight promotes more precise / steady flow.
- Shorter pitch and double flight reduces the material flush back (fluidic material).
- Shorter pitch reduces the agitation.

Regards,
Ishwar G Mulani.
Author of Book : Engineering Science and Application Design for Belt Conveyors.
Author of Book : Belt Feeder Design and Hopper Bin Silo
Advisor / Consultant for Bulk Material Handling System & Issues.
Email : parimul@pn2.vsnl.net.in
Tel.: 0091 (0)20 25882916

4. Dear Shri I G Mulani & BALVINDER SINGH

The material i have to convey is fly ash with 3-6% moisture ,
but the screw convweyor during conveying will spray water on the dry ash and convert it into wet form before discharging it from its outlet .
The bulk density of fly ash is 0.8 tonnes/m3
& its weight density is 1.6 tonnes/m3
the length i am considering for the conveyor is 2.5 meters. i am considering Regular pitch double type screw conveyor,pedal flight type .

i think that smaller pitch will definetely apply more force not only because of the pitch but the resistance of pushing the material will also increase and hence demanding for a higher bkw for the same amount of material to be conveyed .

thirdly the filling factor will depend on the rpm and the pitch of the conveyer .
please comment am i right or wrong and suggest me in either case./

thanking you

with regards

sachin arora
energo engineering projects ltd
ohkla phase-ii
nd-110020
new delhi
ph-91-11-30882047

5. RPD - Invista (UK) Ltd., U.K. Guest
Sachin,

What you have descibed in your last posting is not a screw conveyor, it is an "ash conditioner" and is a very diffferent animal.

A screw conveyor is designed to move material forward, generally with minimum possible power input. An ash conditioner is designed to put much more power in to shear and back mix the bulk material to ensure good mixing of the powder and water and achieve the required residense time. It is a piece of process equipment not a transfer device.

They generally have a series of adjustable blades, some of which force the material forwards and some back.

You may have stood a chance designing a screw conveyor but if you have no experience of the equipment trying to design it based on responses to questions posted on a forum is asking for trouble.

I would suggest talking to suppliers of this type of equipment.

6. DEAR MR RPD ,
I DO AGREE THAT IT IS A DUST CONDITIONER AND HAS A FUNCTION OF CONDITIONING THE ASH RATHER THAN TRANSFERRING .
I ALSO DO AGREE THAT THE DESIGNING PARAMETERS ARE A LOT DIFFERENT THAN THAT OF A SCREW CONVEYER .
IT IS ALSO GOING TO BE DESIGNED BY SOME ASH CONDITIONER DESIGNER , BUT I ALSO WANT TO DESIGN IT ON MY END AND WILL SEE THAT HOW CLOSE I AM TO THE ACTUAL DESIGN .
IN THIS REGARDS I NEED YOUR VALUABLE SUGGESTION LIKE THE ABOVE ONE.

THANKING YOU ONCE AGAIN

WITH REGARDS

SACHIN ARORA

7. ## Ash conditioner design

You say that you wish to determine the design yourself yet are asking other to supply the information. I suggest that if you wish to understand the mechanics of screw equipment and of particuate solids. it would be better to start with the literature and develop an appreciation on fundamental grounds, rather than the opinion of others.

As RPD says, an ash conditioner is totally different from a screw conveyor and the process is essentially one of continuous mixing. If you work through a literature search on helical screws and continuous mixing, you should form a good idea of what is involved. It is no task for amateurs to design equipment of this type. Even with 'simple' screw conveyors, it has been pointed out that there are many variations of construction and duty. Conveying, dispensing, feeding, elevating and screw hopper dischargers have different functions, objectives and work on a various different operating principles. For example, there is no comparison between the mechanics an Archimedian conveyor and a static screw elevator as they operate on entirely different principles, although both employ a screw and a surrounding circular casing. I would recommend that you start with horizontal, controlled infeed, partially loaded screw conveyors, as described and backed with application data in the CEMA publications, and leave the awkward jobs to the specialists. There are enough disasters in the industry already, as the situation is not much improved from the Rand reposts of the 80's.

8. A screw type ash conditioner is at best a tempermental beast.

Even those who claim to know how to do it often end up making slightly wet dust or slurry.

Lyn's comments are a stern but fair warning!

9. ## thanks to all professionals

once again thanks to all the proffesionals for your valuable time

with regards
sachin arora

10. nikhilmohite2010 Guest

## Thank you for this clarification

Dear Sir,.
Thank you all of you for giving such information in detail.
Thanks & Regards,
Nikhil Mohite

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