Judging by your photograph that you so kindly provided It looks exactly like an over load-stress situation.

How often to you grease these idlers?

IF YOU ARE NOT GREASING YOU WILL ALWAYS HAVE PROBLEMS.

Can you afford to reduce the belt loading and then in turn reduce the stresses on the idlers? That seems to be the root of your problem judging by the condition of the idlers in the photograph. ■

Ok we still do not know the tonnage you are moving or whether it is wet lime etc.

can you forward a better set of pictures to me at

lzaharis@lightlink.com ■

Looking at the photo - seems like 2 different idlers next to each other.

First, U need to determine the loading on the idler....

In the curved area - if u use the same load rating idlers in the straight section...U will need to reduce the spacing > as this seems to have been done.

If U do not have this, U can estimate/calculate the load from geometry.

Also...look at belt conveyor idlers books eg Apex Fenner, Sandvik/Prok etc etc...

Next - U need to design/select the idler to suit.

From the photos.....

one shows a stub shaft welded to the end disc....it will be very hard to get the idler shell face run out smal....so u will get flapping of the belt and increased loads...not good for the idler..

one shows a thru shaft and the failed connection to the idler end disc.

U have live shafts > under comment shaft design codes, weldments to the shafts are not preferred and if not avoidable, the stress level is the shaft has been very small to avoid fatigue type cracking. Further, the quality of the weldment has to suit fatigue type loading.

If U wish to stick with live shafts > suggest that U go to a belt conveyor pulley manufacturer for their design/make/supply. Ensure that U get a shaft locking element connection between the shaft and the end disc and NOT welded as U have got now.

The other alternative is to go to DEAD shafts ie non rotating...similar to belt conveyors..suitably selected for the loadings and speed etc.

Your problem will be solved.

End of matter.

Cheers

James ■

Dear Mr Pk Gupta

It appears idlers at curved portion failed due to improper selection of idler comonants. At curved portion idlers are to be very carefully selected based on idler loading

It appears these rollers are on 90 degree curve and loading on each roller is more than idler rating

In case you give us follwing information we cn select proper idlers for you

1.0 Belt tension at curved portion in case this figure is not readyly available you can give us conveyor profile ,conveyor capacity,conveyor lift and belt width

2.0 No of rollers provided on curve

3.0 Weight of belt / m run

3.0 Existing idler Tube dia, shaft dia and bearing dia

4.0 existing conveyor motor rating

we will calculate belt tension and select roller size and spacing for you

A R SINgh ■

Dear Mr. PRAMOD GUPTA,

This upper bend area for corrugated sidewall belt systems is an extremely high tension point for both the belt and the supporting idlers. Typically, the belt manufacturer works closely with the conveyor system design company to ensure that proper idlers are specified. I suggest that you contact the belt manufacturer for their input.

If you can not get a good response from them, I can give you a couple of firms to contact on this problem - but expect them to charge for their time and expertise.

Regards, ■

Looking at the photo again.....yes it is on the carry high tension side.

The FY bearings are quite close to each other looking at the bolts.

So.....U do not have much choice on the spacing.

The issue is the shaft size/design and connection to the idler end disc.

Is this machine a genuine OEM machine or a cheap copy??

The OEM is serious and protective of his reputation should be right there with the answers.

Other than that - U need to get a better design for the idler.

U need to supply

belt tension - can est .

idler face width

belt width

bearing centres

belt wrap/change of angle at each idler.

A good "pulley" supplier should be able to design and make suitable pulleys for U.

Cheers

James ■

We're all on a learning curve here. HO HO HO.

Your photos show the two lower rollers relatively clean about where the cleats run, showing paint. On the uppermost roller the similar contact zone is polished whereas the central zone still shows clean paint.

Suggesting that the top roller has exhibited a measure of seizure, from the polished zone, it would be helpful to know which rollers deteriorated first.

Since there is accretion on the lower rollers while the top roller is clean suggests earlier deterioration of the lower rollers. Which one? The middle one. If the bottom roller had failed then the top idler would be unaffected and a lower idler would have dropped out.

Accretion distribution on the central portion of the lower rollers shows that the belt is not making proper contact on those rollers and the shafts are deflecting under 2 concentrated loads, under the cleats, rather than operating under the UDL which the designer considered. I would have considered a UDL until today & so would anybody else who had read the Flexowell Manual in the early 90's. OK so refresh me!

But I do remember the knowledgeable Flexowell Sales Engineer mention that there is little bit of distortion along the edge portions which is highly desireable from the mold release aspect.

I don't remember anything said about the central portion hogging away from the rollers. We know that convex curves on troughed belts must be limited to prevent excessive edge tension developing the dreaded "W".

If the top roller is clean because it is out of the path of debris then the issue of two concentrated shaft loads is probably the business for now. ■

Further to my previous blurb I have now realised,remembered, that this type of belt is stretched between side deflection rollers, at the base of the lift, and the more familiar friction drive at the head pulley. Tension distribution across the belt cross section will vary from two distinct concentrated reactions at the bottom to a reasonably uniform distributed tension at the top. Although the tension at the bottom is much less than at the head I suspect there is a distortion of the belt which is not fully corrected until the belt has substantially navigated the top vertical curve.

We had a similar phenomenon in a recent thread about flat belts folding over in a GTU & although the conditions vary these threads highlight that we are neglecting, taking for granted even, the possible behaviour of dangling rubber.

For myself I am now surprised that more roller failures have not been exhibited & reported. Maybe the design manuals have been updated since my day: but these failures suggest that they have not or that they are not being read properly. ■

Dear Sir

As a previous manufacturer of idlers I can only suggest that you firstly increase the series shaft from what seems to be a 25mm shaft diametre to a 30mm shaft diametre and then to look at decreasing your idler frame spacing as well as possibly going from a 3 idlers per frame to a 5 idlers per frame configuration.

This reduces the shaft length and thus reduces the shaft deflection, which is detrimental to the bearings. The load per frame is also carried by 10 bearings instead of 6 when using 5 idlers per frame.

I agree with the gentlemen before that the weight and tension calculations for this section would have highlighted that the idlers you are using are not suitable, however I presume that you are looking for a speedy solution to your problem and the above may help

Good luck

Mark Hupertz ■

This is something I come across quite often, but not so severe as this. The problem is that the rollers (as well as not being up to the job) have not been positioned correctly. They are supposed to be positioned so that all rollers have exactly the same amount of deflection as each other. The fact is, if you have 3 rollers acting as deflection rollers in the curve, once one has gone, then the other two have to take the extra force and so will soon deteriorate aswell.

To quickly solve this, remove the three, replace with 5 and ensure all EXACTLY act on the same degree of deflection as each other. This will increase the radius of the curve and reduce the forces actually acting on them. By increasing the radius of the rollers will also help, and for security, increase the size of the shaft. If you want further help, contact me at stan.holcroft@fennerdunlop.com

Regards, hope this helps you,

Stan ■

This is cuious. I assume that all failures are on the same side of the conveyor otherwise the ends of the other side of the rolls would have failed by now.

The rolls are compelled to turn even in this state and with this level of distortion should have broken off at the opposite side long ago. This dilutes theories on underdesign and poor idler manfacture although they can not be fully discounted.

The polishing suggests steel misalignment at 90deg to the tangent of the belt i.e. one is stringer higher than the other but my money goes on product size/overloading/non-central feed onto the belt. ■