What is the failure?

Is the problem related to the failure of ball bearings?

Regards,

Antonio Reis

Vitrom Mfg Consultants

Your Process and Manufacturing Solutions

Phone: 209.834.1900

Fax: 209.834.1039

www.vitrom.com ■

Please be sure the selected belt is capable of troughing at a 45 degree angle with the belt width used. A common mistake in the conveyor industry is to force a belt into a trough that it was not designed for. This will cause undue stress on the outer (wing rolls) and coulkd also make the belt cup.

Another thing to check is the speed of the roller. Is the belt speed sufficient to exceed the rated bearing speed of the roller.

Hopes this gives you some help. ■

Are the rollers failing in all areas of the belt or are they isolated?

Please provide the following info if available.

Width of Belt -

Rating of Iders -

Max belt capacity -

Speed of belt -

Spec on belt -

We can then determine if there is a problem in the system.

Gary Blenkhorn ■

Fernando,

My personal opinion, and note that I don't have much information on the system, you may have unfavorable distance between idler assemblies and the belt deflect enough that it loads the bearings axially above the bearings rating.

Maybe you have the capabilities of measuring the axial force by using a simple load cell.

Good luck.



Antonio Reis

Vitrom Mfg Consultants

Your Process and Manufacturing Solutions

Phone: 209.834.1900

Fax: 209.834.1039

www.vitrom.com ■

I am assuming an idler spacing of approx 1.2 M, my calculations come up with the belt being loaded approx 95%.

Calculated load on idlers is approx 8000 N.

For a 2% sag counterweight should be approx 9000 kg.

Accel tension 175 kN.

Running tension 85 kN.

Hope this info is helpfull.

Gary Blenkhorn ■

Hello Mr. Fernando N. Ribeiro,

It is interesting to see impressive responses to your query. Lot of information is already available in this discussion thread. However, if you can mention following data, possibly it will complete the data required for analysis by various respondents :

1) Material bulk density.

2) Material size, maximum and some indication of size gradation.

3) Bearing size and number (for the side rollers).

4) Spindle size between bearings (for side rollers).

5) Length of central roller and side roller.

6) Whether fixed frame type or garland type.

7) Pitch of idlers.

It is presumed that bearing size is same for central rollers and side rollers. If not so, please clarify. The belt sag % between idlers will play dominant role for such deep trough conveyor handling material of high bulk density.

Now one has to check whether the failure is due to inadequate design or some other reason.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Dear Mr. Fernando,

Regarding load on side rollers, I would like inform the following.

One needs to check the load on rollers mainly for 3 conditions viz. (1) Material regular load on belt and idler vertical misalignment zero, (2) Material regular load on belt and vertical misalignment of idler, (3) Material regular load on conveyor but empty belt on vertically misaligned idler.

The last one is likely to give maximum load on side roller.

Again in each case the radial and axial load is composed of material pressure (force) on belt, belt’s own pressure (force) and roller self weight, with their differing application points. The load mentioned by you is possibly material force (pressure) in one case, mostly number 1 above.

The calculation of load on idler is a complex and lengthy issue and difficult to describe further on the website. Please also check the vertical misalignment of idlers for the conveyor under analysis.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Fernando,

When you analyze the wing roll loading, do you consider the following:

1. upper bearing takes all thrust load plus partial radial load

note: the bearing is seated against the shaft shoulder on the

upper bearing, but has clearance to the retainer ring on

the lower bearing not allowing the thrust to be shared.

2. dynamic factor of belt vibration action as noted in the Precismeca design manual that is a multiple to stady-state

P.S. We wondered where you went after MGS, assuming you are the same FNR we knew. If so, glad to know where you are.

Regards,

Lawrence Nordell

Conveyor Dynamics, Inc. ■

Fernando,

A further comment on the bet specs. causing added wing roll loading. I do not believe the belt bending stiffnes causes significant loading on the outer roll. The belt is too flexible and wide.

Lawrence Nordell

CDI ■

Hello,

I have just picked up on this thread and will review previous comments.

However briefly:

1. Are the idlers equal roll i.e. centre roll length = wing roll length?

2. Vertical Misalignment load would also affect the centre roll.

3. The calculated deflection of 12 minutes is high and leaves very little allowance for manufacturing tolerances. What bearing is used and what is the shaft diameter.

Regards,

Adi Frittella

Melco Conveyor Equipment

adif@melco.co.za ■

Hello again,

Sorry about previous posting. I note that the information is already available.

I have run some quick calculations and estimate the bearing life on the centre roll (with 6306 bearing) at 14,500h and the deflection to be in excess of 17 minutes of arc for a 30mm diameter shaft.

This indicates an underdesigned idler.

What is still surprising is that the wing roll and not the centre roll are failing.

I have not considered the factors outlined by Larry as yet.

Adi Frittella

Melco Conveyor Equipment

adif@melco.co.za ■

Hello Fernando,

Sorry again, but one of your previous posts showed the bearing size as 6306 (your reply to Mr Mulani).

Using a 40mm shaft and 6308 bearing I would estimate a life in excess of 40,000h and a shaft deflection of around 6 minutes (on the centre roller). Hence idler selection appears correct.

In summary:

1. Idler selection correct.

2. Idler failure is random and not specific to areas of high tension (eg curve).

3. Sealing system checked and is suitable.

What else:

- Could it be a temperature effect - are failures seasonal?

- Has it something to do with the workings of the machine?

A very interesting thread.

Will keep on investigating.

Adi Frittella

Melco Conveyor Equipment

adif@melco.co.za ■

In my opinion you are fishing in the wrong pound.

As I remembered you stated that the belt is 650m long... A few cords broken on the belt will not affect the bearing life of the wing idlers.

The progress of this thread leads me to the following:

1- The loading of the conveyor in not constant or even. I suspect that frequently there are load voids of 20-40 meters.

2- I suspect the tension systems of the belt is operating at the upper limits meaning that the belt could be shortened by some.

3- I suspect that the belt deflects between idles and in the process hammers idlers to dead.

4- The center idler takes the impact perpendicular to the axial load and the wing idles divide the load in some fashion that would be very difficult to calculate.

A small slippage of the belt can make amplify the affect several times.

Just an opinion.

Antonio Reis

Vitrom Mfg Consultants

Your Process and Manufacturing Solutions

Phone: 209.834.1900

Fax: 209.834.1039

www.vitrom.com ■

Dear Mr. Fernando Ribeiro,

This has developed into a very interesting thread.

It appears that there is nothing wrong with the idlers - but this one conveyor is placing undue stress on the wing cans. Although you are having bearing failures as the primary cause of idler failure, I would be interested in the answers to the following:

[1] Is there a definitive wear pattern on the face of the angled (wing) idlers - specifically at or near the point where the belt edge runs against the can?

[2] Are both idler bearings failing, or only the outboard bearing?

[3] Are all of the idler sets failing, or just those in the transition zones? If all, are they failing at the same rate?

[4] Has the conveyor been aligned properly?

[5] What is the belt sag % between carry idlers and between return idlers? (Note: on the carry side, make this measurement in the middle of the belt, not at the edges.)

From the data provided to date, I suspect that the belt and idlers are suited to the conveyor, but the idler placement (alignment) or belt tension may be off.

If the belt tension is too great, the end user has the choice of lowering it or upgrading the idlers to accommodate the extra forces involved. If the tension is too great, the idler failures are only the first casualty they can expect to experience -- they can also face problems with their pulleys and belt.

Regards, ■

Dear Mr. Ribeiro,

I look forward to seeing the test results.

It is a pleasure to see a company taking the care to troubleshoot a problem such as this.

Regards, ■