Wont work - been tried before in the sugar industry

Use inline idlers sets

I am assuming that your offsets have a foward tilt built into them.

U could try to remove the tilt by inserting tapered packers as an alterntaive to replacing idler sets

Ta

James ■

Hello Gareth,

Your best bet would be to replace the idlers, as suggested by Mr. Morrish.

To answer your specific questions:

(1) If you run the belt in the reverse direction of the offset idlers, you are emphasizing the belt tracking influences of the two wing cans. Therefore, you will get eratic belt training.

(2) The severity of any belt mistracking will depend on the placement of the idlers, any material build-up on the idlers, and the condition of the belt's bottom cover. Given that the idlers are set (placed) to provide good tracking in one direction, it is likely that the belt would want to run off the system when run in the reverse direction.

Note: the negative influences can be diminished somewhat by ensuring that all idlers and pullies are perfectly(?) square and that you install in-line self-training idlers periodically.

(3) If you placed every other idler in its reverse direction, you would either have trackung problems in both directions or the belt would be sufficiently confused that it would run straight.

Good Luck with your project. ■

Good morning Gareth..

I have had some success with reversible conveyors, though I tend to avoid them by favouring the dual carry principle of loading the return belt instead.

My experiences are as follows on reversible belts:

- Best to use garland idlers

- If you use fixed idlers then use ones with zero degrees forward tilt

- Do not even think of using tilted idlers one in one way and the next the other way round. Any vertical misalignment will kill you

- Do not use belt friendly off-set frames if you are conveying lumpy material, as in one direction the material will get trapped between the wing roll and the frame. Otherwise off-sets are fine.

- It is essential to optically align the idlers before you pull in the belt, as it is also essential that you do not train the belt.

- Pulley alignment must be perfect

- Edge crown the terminal and take-up pulleys (essential)

- Loadings must be central

- Take care with belt quality and straight splices

- Allow the belt to bed in and as mentioned above resist the temptation to climb in and train the belt.

- And don't let anyone else climb in an start hitting the idlers when you are not there. This is the absolute downfall of reversible conveyors, as you will never get it right after that unless you start from scratch, which is difficult with the belt in place.

Regards

LSL Tekpro ■

The use of garland idlers must be the subject of further discussion since there is a tendancey for backward tilt on these units due to belt drag. This may be inconsequential or a concern depending upon belt loading etc. I would rather recommend high quality fixed frame idlers of special order where you can ensure that they are tilt free.

Please remember that normal tilt free idlers are allowed a forward tilt as part of there manufacturing tolerance. This tolerance tilt need not be the same on both sides of the idler which will generate greater head aches and confusion in your application.

Keeping other people off the conveyor is ABOLUTELY essential. If possible tack the Idler frames in position once the conveyor is tracked to your satisfaction. ■

My good friend Graham Shortt informs me that he has a design for galand idler stands that replace conventional fixed idler frames, thus allowing garland idlers to be fitted easily as a replacement, to make belts reversible.

This was done in conjunction with Melco here in South Africa, and there can be no doubt that the garlands improve things considerably in practice for reversible belts.

LSL Tekpro ■

As described in other threads, Common problems that cause belts to track poorly, reversing also:

1. Belt Cupping

2. Crooked splice

3. Belt camber

4. Offcentered loading

5. Segregated Loading

6. Surge loading

7. Over tensioning

8. Worn pulleys

9. Worn pulley lagging

10. Incorrect belt (does not rest fulley in trough) ■

A South African based company makes an innovative tracking system that potentially works equally well regardless of direction of travel, they are:

TRU-TRAC ROLLERS (Pty) Ltd.

Conveyor Belt Tracking Technology

Tel: +27 (0)12 6619531 Fax: +27 (0)12 6619489

Email: info@tru-trac.com Website: www.tru-trac.com

Have good reports of effectiveness of this system ■

A South African based company makes an innovative tracking system that potentially works equally well regardless of direction of travel, they are:

TRU-TRAC ROLLERS (Pty) Ltd.

Conveyor Belt Tracking Technology

Tel: +27 (0)12 6619531 Fax: +27 (0)12 6619489

Email: info@tru-trac.com Website: www.tru-trac.com

Have good reports of effectiveness of this system ■

Dear Mr. Gareth Blakey,

Please clarify whether the idlers you are mentioning have forward tilt. If there is no forward tilt, the belt-idler behaviour will be subjected to following influences :

For the offset idler it is generally preferred that the belt should first touch central roller. In this situation, for the approaching belt, the material side forces are under a passive state, which are much higher compared to the active status of the material forces while leaving the idler. Thus, in this correct position the belt is first getting supported at the bottom so there will be least pinching / straining of the belt. However, when the belt is running in reverse direction on such idler, material side pressure of passive status is much higher and it will tend to force the belt downward i.e. trough belt will tend to wedge in between the inclined idlers, below which there is no direct supporting roller. This will enhance the pinching effect / strain and it will also marginally increase the drag resistance of the belt. However, if you are having strong carcass belt, it will not result into remarkably adverse situation. But for thin carcass the effect will be pronounced.

If you have got a forward tilt idler then it will be difficult the avoid misaligning action. Only solution to this would be to place 50% of idlers in reverse orientation i.e. one idler as central roller in leading place whereas the next idler has central roller on trailing place. This will neutralise the aligning versus the misaligning action and you will be using the conveyor as if it has no forward tilt of the idlers.

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 ■

Dear Mr Mulani..

I must disagree with you, as what you say is normally not the case in practice..you say..

".......If you have got a forward tilt idler then it will be difficult the avoid misaligning action. Only solution to this would be to place 50% of idlers in reverse orientation i.e. one idler as central roller in leading place whereas the next idler has central roller on trailing place. This will neutralise the aligning versus the misaligning action and you will be using the conveyor as if it has no forward tilt of the idlers........ "

All very well in theory, but in practice the idlers are never perfectly aligned, and so for varying loads the belt training situation varies too.

Never use forward tilted idlers in any configuration on reversible conveyors if you want to be sure of a good night's sleep.

From my experience with reversing belts, I believe the correct solution is as per the previous discussion whereby garland idlers are used. To this end, as we mentioned earlier, you can replace the idler brackets directly with garland idler stands as per Graham Shortt's very nice arrangement. In this way, there are no steelwork modifications required, and it actually works very well... It keeps it simple too..

Regards

LSL Tekpro ■