Screw Conveyors 3

[sewerfix]

General Question
What would the selection criteria for using shaft versus shaftless screw conveyors?
Are there any major advantages of one over the other?

 

[smckennz]

Shaft screw conveyors are strong and will last a long time. Very expensive though.

Shaftless screws can go around corners, but tend to wear the casing because the casing acts as the guide. OK for occasional use on coarse nonabrasive materials such as grain. Also sizes are normally small.

For heavy continuous duty use shaft.
For occasional light duty use shaftless.

I got landed with a shaftless screw for conveying sand. Total misapplication and I had to pull it out. We call them "chook-feeders"

Cheers

Steve McKenzie

 

[ischgl99]

This may or may not apply to your application, a couple projects I was on used shaftless conveyors for dewatered sludge that were smaller then the discharge chute from the machine, which was sized for a shafted conveyor, requiring the chute to be necked down in size between the machine and conveyor. This caused serious bridging problems and required the replacement of the conveyor with a larger size in one instance and speeding up the conveyor in others. Smaller is not always better even when ratings are the same.

Shafted conveyors also seemed to convey better on inclines then the shaftless and the shafted lets water drain better when flushed. The shaftless conveyor runs on a teflon wear pad that seals the flights and prevents flushing water from draining. Mike Bensema

http://www.dutchmenservices.com

 

[Drazen]

Did you notice that shaftless conveyers have profiled stators, that is static part of conveyor has a groove calculated to fit the shape of a "screw" itself. Such design gives more turbulation to moving mass and completely avoids dead corners.
I presume that is the reason for use it in sludge conveying applications.

On the other hand, standard screws with shafts have ability to be used as rather precise dosing devices in a wide range of applications. (I saw screws with 10 mm as well as 150 mm in diametar serving the same purpose).

 

[stanier]

I have used many shaftless screw conveyors on municipal sewage sludge either primary or activated. Conveyors up to 45m long have not been a problem. The conveyors have troughs in UHMWPE up to 400mmm width. Sharing knowledge is a way to immortality

 

[sewerfix]

From my background in waste water treatment plants, we always used shaftless spiral conveyors for inlet works screenings, grit transfer and dewatered sludges. In specifications I only ever see shaftless conveyors.

I'm doing a subject at Uni - Materials Handling and the lecturer is from the grain industry and unfortunately is only discussing shafted conveyors.
I was wondering the selection criteria for the conveyor type. Thanks for everyones input.

Andrew

 

[calculate]

For reference: Screw Conveyor Horsepower Calculation at:

http://www.geocities.com/brybolt/calculate.html

 

[PeterCharles]

There are two types of centreless screws used in screw conveyors :-
1) flexible bits of wire that go in small diameter (3"-4&quot bits of flexible tube for very light duty applications
2) 1/4" thick flighting designed to go in more conventional screw conveyors.

I was involved with a 12" screw conveyor handling fine wet coal which built up very quickly between the flight and centre tube. We changed to a centreless screw and the problem went away.

 

[beloka]

http://www.jacmor.com.au/

I suggest you refer your query to a reputable designer manufacturer. This manufacturer JACMOR ENGINEERING is known as such in Australia at least. PS I have no connection with JACMOR but have used their equipment.

 

[varrier]

hello sewerfix,


you will get answer for you qustion from the site

http://www.martinsprocket.com

http://www.arlat.com/conveyor.htm

varrier

 

[BulkNet]

In response to beloka, you may also wish to try BulkNet or Scott Spiral which is a direct competitor to Jacmor and will provide outstanding quality with price.

 

[gongmuro]

I have used shaftless screw conveyors for sewerage screenings with relatively good results, bu now I have a client that wants to use one for vertical conveying. has anyone done this? He also wants calculations on the amount of compression (deflection) in the screw. Any idea on where I can find a reference? Thanks,

Bob

 

[clemm]

20 years in plant maintenance. Unless you have a very, very good reason to use the shaftless, Save yourself some money and your mechanics alot of grief. Send the shaftless to the scrapyard where it belongs. The shaft helps convey, as product tends to slip thru the hole where the shaft should be. If you bend a piece of metal back and forth enough times IT WILL BREAK, This applys to metals that are desighned to bend as well, IE: shaftless screws> they bend alot on every revoultion, a shafted bends a litle and will eventully break as well, unless you give them some flex at the joints. Genearly shafted performs better and lasts longer.

 

[ischgl99]

gongmuro, I commissioned a couple centrifuge projects that used vertical shaftless conveyors on municipal wastewater. The vertical runs tended to plug easily when the solids were not dry enough or a water slug caused the sludge to slip on the flights. Spirac may have some info for you, they are located in Georgia.

Mike Bensema

http://www.dutchmenservices.com

 

[gahyde]

Some of the comments are confusing the two different types of shaftless design. One is the smaller flexibe type, much like a thin 4" OD spring (see

http://www.flexicon.com).

The other is heaver (think one inch thick spiral flighting up to 36"OD) used in WWTP & other industries(see

http://www.spirac.com)

or contact me for discussion at greg.hyde@spirac.com

 

[gahyde]

adder- A lot of people are trying to get into shaftless that do not have clue. If you are considering shaftless get a mfr than has been in the businesss more than 10 years. SPIRAC invented the technology in Sweden 30 years ago and have thousands of installations all over the world, offices in 6 countries on 4 continents.