Dear Mr. Hasan,

I will suggest you to specify some technical information about the conveyor and scraper such as :

1) Belt width

2) Belt speed

3) troughing angle

4) Capacity (mtph)

5) Conveyed material name

6) Material size

7) Moisture content

8) Bulk density

9) Scraper type / arrangement

The above information will help the respondents like Mr. Gerald Coenen to give you a more appropriate and useful suggestion for you.

Regards,

Ishwar G Mulani.

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

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■

Use belt tracking carry idler frames with

HDPE covered rolls.

Urethane covered rolls should also work

provided the material is not acidic

(HDPE is cheaper but does not last as long

as urethane)

www.lorbrand.com ■

I would think that Pakistan is somewhat similar to Mexico, where I am at, in industrial technology... most of the time "first world" solutions never work, simply because this are considering that the actual conveyor and chutes are manufactured to CEMA standards. And most of the time, chutes are non existant and the conveyor was made by the local welder.

First of all, when dealing with belt misalignment, having a beltcleaner that works is only part of the solution and maybe not even that.

Have you tried cleaning the idlers and then running the belt and checking if it continues to misalign. If so, then what you need is an efficient belt cleaner.

Belt cleaners come in different shapes and sizes but all fall into the following 3 categories:

Precleaner: Soft blade (urethane, rubber, etc..) installed right at the pulley and acting against the belt direction equiped with an elastomer or spring tensioning device to keep the blades on the belt.

Scraper: Hard blade (tungsten, steel, etc...) installed right after the pulley and acting either perpendicular to the belt or with a slight angle in the direction of the belt travel equiped with a spring, bladder, elastomer, or a flexible cleaning blade for tensioning the scraper and keeping the blades in contact with the belt.

This two types of belt cleaners are manufactured by many different companies and all work well like Martin Engineering, Hosch, Flexco, Arch (Gordon), etc... and of course CTS (manufactured by us)

Usually the problem is not the belt cleaner but the installation. It is obvious but many times overlooked: A belt cleaner not properly installed will not work properly.

The third category is what we call "home made" which is a piece of rubber, old belt, etc... just forced to the belt acting as a scraper...this do not work, even if they do for the first 2 days, they will eventualy not work.

For a reversible belt, most precleaners would not work because this work against the belt travel and would brake any splice not properly vulcanized, which are fairly common. And on the scrapers

, you will be limited to those scrapers that act perpendicular to the belt, and this most of the time are too abrasive damaging the belt or the ones having a flexible blade.

I would recomend 2 scrapers acting with a slight angle with flexible blades, each at a different puley. And both installed by people who know what they are doing. When traveling in one direction one scraper cleans the belt and the other just glides not attacking either the belt or it's splice since the blade is flexible, and this is reversed when traveling in the other direction.

NOW..if the belt is misalianging for another reason that is not carryback material stuck to the return idlers, that is a whole other problem that can be any of the following reasons:

Defective or worn belt

Idlers installed at a slight angle

Pulleys at a slight angle

Incorrect splices

Material feeding of center

Conveyor structure not straight

You might try instaling auto alignement idlers, but this rarely work if the misalignment problem is too big.

I would recomend to check for the obvious like Pulleys and idlers not perpendicular with belt travel, and if this does not work... the best solution is to install vertical idlers every 1 or 2 meters and simply force the belt to work properly, This would in time damage the belt... but would be less expensive that correcting a bigger problem like a defective conveyor structure.

Good luck! ■

Mr. Hasan Kazmi,

Following features can reduce your difficulty:

1) Use rubber lagged pulleys. You are handling detergent which is non abrasive. So, you can have 8mm thick rubber lagging on pulleys/.

2) Use carrying rollers having 5 mm thick rubber lagging

3) Use return rollers of rubber disc type

4) Use external scraper and internal scraper at both the ends. The scraper blades should remove / shave off the material rather than converting it into paste. So, proper type of blade and proper pressure is necessary

5) Rollers should not be unnecessarily big in diameter. Lesser diameter means more centrifugal force for same peripheral speed. This improves the self-cleaning.

Rubber means flexible surface, so material automatically gets dislodged from rollers / pulleys (this is like car-tyre tending to remain clean as built up is on shaky surface i.e. rubber).

Regards,

Ishwar G Mulani.

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

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■

Just my two cents.

I agree with some comments from the previous posters and strongly disagree with others.

In most cases the local welder is as good as one can get because even if a system from a preferred company is installed, the local welder ends up performing the task most of the time.

Most belt cleaners lack performance because the systems are over simplistic and not adquate for the task. As an example in this thread five people provided opinions yet the belt material was never considered or mentioned.

In general I consider three types of belt cleaners; Scrappers or plows, counter rotating/surface profiled rolls and liquid/air belt washer systems.

All types are efficient in those applications were the designer and integrator condidered the system as an integral part of the bulk transfer system and not an after thought.

I designed and installed several systems and unfortunatly never in a situation where I could get a catalogue and order an "off the shelf" unit.

In every scraper type cleaner there is pressure between the belt and the scrapper creating the possibility for wear and mistracking. As the adhesion of the bulk material to the belt increases, the attack angle of the blade and the pressure it exerts on the belt also increases to be able to remove the material. It is wise to design a cleaning system customized to the process requirements optimizing for the usable life of the system.

Antonio Reis

Vitrom Mfg Consultants

www.vitrom.com ■

Mr. Hasan Kazmi:

It appears that you have both a carryover and a spillage problem, which is giving you a third problem of belt mistracking.

You also mentioned that this system is reversible. Is the problem of mistraining worse in one direction, or do you have serious mistracking both ways?

In general, carryover is controlled by using cleaners on, and just after the discharge pulley(s). Also, carryover, if not controlled, will build up on the return idlers and can cause mistraining on the return run and at the start of the carry run. That is, carryover should not cause build-up of material on the carry (troughed)

idlers. If you are experiencing materiual build-up on the carry idlers, it is more likely to come from spillage.

Having said this, you can try to eliminate carryover by upgrading your belt cleaners. The fact that your belt is reversible will limit your choice of cleaners. As others have pointed out, cleaners are only as good as their installation and maintenance. If you can not eliminate or control carryover, you can try to minimize the effect by the methods suggested by Dr. Mulani. In addition to the points he suggested, you can try using scalper blades on the built-up idlers to scrape off the contaminate. If you do, use drip pans to catch or deflect the material away from the conveyor.



As always, it is difficult to make suggestions without observing the system. Because of this, it may be helpful for you to call in representatives of your local belt service companies, consultants, or cleaner manufacturers. Evaluate their recommendations and proceed accordingly.

Good luck! ■

Dear Sir,

have a look to our

www.vsr-industrietechnik.de

We await your detailed inquiry.

Thanks in advance ■

Dear Mr. Hasan,

While correct belt cleaning is certainly the start of keeping a belt tracked properly, there are other areas that may be causing the belt to mistrack also. My recommendations would be:

1. Multiple cleaners to effectively reduce carryback to an acceptable level. This may require as many as 5 cleaners.

2. Make sure there is not a condition of the belt that is contributing to the tracking problems, belt cupping, crooked splice, belt camber, or transition distance problems.

3. Make sure the original installation of the conveyor structure is aligned in three planes. The tolerances can be found in the CEMA handbook 5th addition appendix C page 407. If you do not have access to this book let me know and I will fax you a copy of that section.

Tracking problems can be varied. We have a section in our Foundations III book covering tracking problems. Please contact Gini at 309-594-2384 ext 429 for a copy. ■

Are you able to install a "wash box"? If you are able to, install a wash box, I recommend installing it just behind the head pulley and install a secondary scraper just behind.

If you cannot allow any more moisture to be added to the product, you will have to divert the washed off fugitive material to another area.

Without seeing your exact application it is hard to know if this will work for you.

If Larry Goldbeck reads this reply, he could give you more insight as Martin manufactures "wash box" systems.

Regards,

Brent Wheeliker

Clemro Western ■

I agree with Mr. Miller that spillage may be your problem on the misalignment. Installing rubber, UHWM, or urethane lagged rolls is just a "band-aid" for the larger problem of poor skirting. By making some alterations to whatever chute work in currently in place a nice skirt seal with a slider bed should prevent the spillage and thus prevent buildup on the rollers.

www.aeec.com ■