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Power-User

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Screw Conveyor Shaft

04/24/2010 1:58 PM

Dear all,

I am facing frequent problem in shaft broken in my inclined screw conveyor.

shaft dia is 35mm.

I tried to control through relay. so that high current will make it to trip.

But still it broken.

I want to go for shear pin.

So please tell me how can I design it.

Please send me drawing if possible.

Thank you.

Regards.

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Commentator

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#1

Re: Screw Conveyor Shaft

04/24/2010 8:15 PM

It is not very clear...do you have a picture or something?

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Guru
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#2

Re: Screw Conveyor Shaft

04/24/2010 8:37 PM

Your relay has to be what we call a magnetic starter. It has 'heaters' that are changable, and sized to your motor's amperage levels. If the motor draws too many amps, or the power loses a leg, the starter breaks the circuit.

Using a shear pin will not solve your problems entirely, you will still have an interruption of process, and down time until a new pin is installed. Getting broken pins out can be troublesome, too.

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#3

Re: Screw Conveyor Shaft

04/24/2010 10:40 PM

It should be helpful if you tell us some more about the product and the mechanism. Is it a screw of Archimedes? What is the diameter of the tube? Is it bend when working - with the weight inside? If it is for light materials like flour, even sugar, you can also consider a spring type screw with only a piece of shaft on the motor. This works great in our chocolate mousse plant. How long is the shaft? And what is the motor- RPM - power?

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#4

Re: Screw Conveyor Shaft

04/25/2010 1:24 AM

You are looking for protection against over load. Please use friction type torque limiter which slips when overloading condition occurs. This will prevent damage to the screw. However check for the reasons for overloading. increasing Angle of repose may solve the problem of overloading.

kiran nawathe

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#5

Re: Screw Conveyor Shaft

04/25/2010 6:40 AM

Simply not enoughinfo to give good advice......

Infos and fotos please......

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#6

Re: Screw Conveyor Shaft

04/25/2010 12:42 PM

A couple quick questions:

Does the screw come to a stop before shaft shears?

Does the shaft shear in about the same location each time?

Where is the binding, and can the binding be remedied?

Hopefully, simple questions can result in obvious answers.

Bill

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#7

Re: Screw Conveyor Shaft

04/25/2010 11:57 PM

XCan you additionally give some picture of the borken face ?

The screw conveyor shaft breakages are frequently related to fatique. In that case the O/L relays will not trip.

The shear-pin will break, but that will not solve the problem.

If it is O/L problem, find the reason of overload. Try to eliminate it. If it is not possible, is it possible to redesign the shaft accordingly?

- Eliminate the cause

- Live with the cause (design so that the cause can do no damage)

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#8

Re: Screw Conveyor Shaft

04/26/2010 3:18 AM

Why is the mechanical overload taking place?

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#9

Re: Screw Conveyor Shaft

04/26/2010 8:35 AM

Just a thought,

When I had a problem to resolve with a 4 inch dia process damper shaft breaking due to high impact loads I used an interference fit shaft and this resolved the problem. We assume that whenever the impact was large enough to shear a key or break the shaft, the shaft would slip slightly until the overload ceased.

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#10
In reply to #9

Re: Screw Conveyor Shaft

04/26/2010 12:55 PM

Thank you,

What is interference fit?

Please see below pictures.

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#11
In reply to #10

Re: Screw Conveyor Shaft

04/26/2010 1:30 PM

Is this the input side of the srew? If yes it seems to me that something got stuck between the wall and the screw. (maybe a foreign part?) I also think the shaft has a couping there (hole and pin?) and the hollow side collapsed? If so - I should weld the spiral up a bit that there is less play in the input, so that your material has to go up and cannot get stuck between the wall and the screw.

What is the product? If powder, really consider only a spring type screw without center shaft. (eventually double - 2 pieces)

During transportation it will even be mixed more homogeneous.

What I see can be repaired.

Hammer the end of the shaft more original and weld it back up. Fix the hole and start running. Looks like Stainless Steel? Don't forget to fix the start of the screw too and give it less play in the beginning.

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Guru
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#12

Re: Screw Conveyor Shaft

04/26/2010 8:08 PM

What comes to mind when I look at your shaft is a well drillers connection. They can join drills and shaft strongly, deliver massive torque, and not break the shaft. If you can get such a connector, it could be welded to your shafts. I hope your shaft rotates the same way the drills go.

If your shaft goes the other way, it seems your pin is too close to the end of the female shaft. It looks like the end of the female shaft has ripped out, the hole was too close to the end.

It would be nice if you could just put a flange coupling there, there are many types, but all are larger than the shaft.

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#13

Re: Screw Conveyor Shaft

04/27/2010 10:05 PM

The photograph of the broken face would have helped as I mentioned earlier. Nor the MTBF (mean time between failures)

However looking at the snaps,

there is a groove between the drive and the load (screw portion) What is the purpose of this grrove? The shaft has broken from the edge of the groove. This is almost definitely a fatigue failure, likely torsional+bending.

Check up the

- bending loads on the shaft - supports, alignment,...

- What is the corner radius of the step (undercut) - if it is sharp, the stress concentration will be a recipe for failure.

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Andy Germany (1); Anonymous Poster (3); billrata (1); dvmdsc (2); kirannawathe (1); mike k (2); PWSlack (1); sandeep lokhande (1); vanuta (1)

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