Greetings,

regarding your slippage problem I have two questions/suggestions.

1. Is it possible for you to install conveyor covers on your conveyor and transfer points-this would eliminate most of your water problem.

2. What amount of pressure or weight do you have for your hydraulic take up or counter weight for your drive unit?

Remember that no matter how much tractive abilty you have that the wet conveyor belt is still going to slip as the belt will naturally

allow water to pool near the bottom and of course collect on the troughing idler side as it has no where to fall away due to the conveyor belts being non porous.

3. Do you have room to install a plow scraper to help push the water off the belting as it comes back to the tail pulley on the return/-as a rule plow scrapers are installed in front of the tail pulley frame to push belt spillage away from the tranfer point.

lzaharis ■

greetings from the US,

There are many manufacturers of Hydraulic take up units,

the two I am familiar with are Hewitt Robins and Continenetal Conveyor corporation.

1.

The tensioners are integral with the drive unit frame and they have a separate hydraulic powerpack that is 480 volt three phase

powered. the belt is tensioned using an unlagged pulley tensioned by a wire rope being tensioned by a hydraulic cylinder

controlled by the hydraulic power pack. the cylinder doing the tensioning work also has a large dry nitrogen gas accumulator to store fluid energy and absorb start up shock.

I would contact these folks or your equipment supplier and see

if any one makes an independant belt take up unit that you could

install. I am handicapped as I do not know your operating set up.

2. The other type of tensioners I am familiar with are the type with a pulley connected to a weight box used to tension the belt that is suspended under the conveyor on a set of vertical steel rails that allow the weight box to slide up and down according to load- this by far is the simplest way to solve your problem-all you need to do is add weight to maintain traction.

2a. You would of course have to build a steel structure to contain the pulley and weight box and bolt the rails to the structure. Of course the belt area near the vertical pulley sled will have to be guarded and you will need to run grease hoses to the pulley bearings. this is the simplest way and the quickest to solve your problem in this mechanics opinion.

lzaharis ■

The best way to prevent belt slippage at the drive pulley when the belt is wet is to install ceramic lagging on the pulley.

This can be done in place by most reputable belt splicing companies. You will need to completely slacken the belt until the drive pulley can be turned in place. (you may also need to unbolt the drive coupling) The splicing company can then remove the rubber lagging and install a ceramic lagging. Curing time will vary depending on the manufacturer. This will increase the friction and prevent slippage.

There are many companies that supply ceramic lagging.

Rema Tip Top and Flexco to name a couple.

Hope this helps.

Gary Blenkhorn ■

Could you use a different type of belt?

Looks like the backing material of your belt is not proper for your process.

Antonio Reis

Vitrom Mfg Consultants

Your Process and Manufacturing Solutions

Phone: 209.834.1900

Fax: 209.834.1039

www.vitrom.com ■

Dear Shri Rekhawar,

You have mentioned that the slippage problem is at the drive pulley of yard conveyor. The supplier of such conveyor has conflicting requirements of providing necessary idle tension in the belt. If he provides high tension then he will have a problem at the concave radius of the mobile machine or at inclined portion near head end. If he keeps the tension low, there would be not be a problem at the concave radius but there will be the slippage problem.

The specific solution to the problem is a design analysis of this conveyor in conjunction with the following:

1) Whether there is one drive pulley or two drive pulley

2) If there is one drive pulley then to examine the possibility of two drive pulley

3) Drive system starting torque.

4) Requirement at concave radial zone

5) Correction in take up force, in relation to the modified design

6) Using liner on the pulley which will have a better frictional grip. Ceramic liner has better grip but in certain situation it can reduce the belt life.

The issue you are referring to, is a routine exercise while designing the stockyard conveyor.

Regards,

Ishwar G Mulani.

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

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Dear Rekhawar:

Among the ideas:

1. more wrap angle

2. higher counterweight/hydraulic force (T2)

3. belt wipes

4. ceramic lagging

5. torque control during starting

I stronlgy recommend the ceramic lagging. This is the type fabricated as tiles and encased in and on a rubber sheet, or bonded to pulley. Yes, many manufacturers have the necessary testimonials.

Rema Tip Top: www.rema.com/lagging/prodd.htm

Richwood Industries:www.relyonrichwood.com/products/pulley.html

There are many issues on the reasons why to use this product beyond its wear and maintenance benefits. Handling moisture and cutting through the pulley-to-belt product slime with the laggings unique surface geometry are a few critical points. Let the manufacturers do their selling job on you.

90:1 price ratio seams quite excessive. I tend to believe you are being gouged.

Lawrence Nordell

www.conveyor-dynamics.com ■

REkhawar:

Sorry for the 90:1 price ratio comment when my fingers meant 8:1.

THe friction values in practice vary more for rubber to rubber (RTR) than ceramic to rubber (CTR). Dry RTR can have 0.6 or higher while wet (water only) it may drop to .35 with grooved lagging, 0.25 with non-grooved and .20 or lower with slimes. Ceramics can yield 1.0 dry, .45 wet and .35 wet with slimes.

The iron ore, bauxite, and nickel industries prefer it to rubber with grooving. The major caveate beyond price is high tension belts in the mega-watt range.

You can find other historical comments on non-rubber based ceramics within this forum. I suggest, unless you have a strong heart and a high degree of competency, stick with convention.

LKN ■

Dear rekhawar:

i concur with Gary Blenkhorn & Larry Nordell. Your best chance for success is with a premium quality rubber-backed ceramic lagging, such as that supplied by Rema. Avoid the low cost ones - they are too expensive!

Of the other options mentioned, I assume that you are already using belt covers. As far as the belt wrap is concerned - refer to the discussion between Larry and myself on a previous thread - Larry maintains that the 1-second "rule" must apply - therefore, your 200 degree wrap may bst e excessive.

Best of luck on your project. ■

Dear Shri Rekhawar,

in addition to increase friction between belt and pulley and to increase belt tension in rainy season question arises if belt does only slip during start-up.

If yes one should think about the installed drive and the torque limitation during start-up. Here a 'right' selected Turbo Coupling could help minimizing start-up factor and slipping belt.

For more information on this kindly visit our homepage:

http://www.startup-components.com

Best regards

S. Obser ■

Dear Mr Rekawar

How did U go with the ceramic lagging for yr drive pulleys as per posts in Aug 2004??

Did U use the rubber backed cermaic lagging??

What were the applications where U installed the new lagging?

Cheers

James ■

Hello Rekharwar..

In the old days, if the counterweight and wrap were correct, I used to rectify drive slip in the rain by lagging the drive pulleys with Linatex. This is the pink natural soft rubber with chevron grooves to let the water out, and has a high friction factor when wet.

Nowadays I don't come across the problem much as designers seem to be a bit better now (and I probably lead a more sheltered life).

For your case, attach embossed ceramic tiles to the steel shell of the drive pulley with the correct epoxy (..note: correct epoxy), and all will be well.

(Do not use rubber backed ceramics, it is too expensive and there are far too many reports of failure of the bonding).

Regards

LSL Tekpro ■

Graham,

Could you share with us the installation time of direct bonded ceramics verses embedded ceramic tiles onto a rubber sheet such as REMA or RICHWOOD?

Dont you believe the removal and installation time of the direct bonded tiles will require significantly more down time?

The direct tile method may be superior, all things considered, but it does not have the time-in-service and reputation for quality control to the expected tolerances compared to embedded tiles in rubber. Your bad experience is noted. Do you think it is an aberation of the locals?

Properly designed, manufactured and installed embedded ceramic tiles in rubber does have a good track record throughout the world. I say this because of your rather staunch criticism of the rubber sheet ceramic lagging.

Looking forward to your comments. ■

Good day Larry et al..

Indeed it does take longer to epoxy the tiles into the shell than to stick on the rubber backed stuff.

You first have to shot blast the bare shell, and then epoxy on the tiles typically in three stages, thus rotating the pulley through 120 degrees at a time.

All this can take up to 3 days. However, if you simply trowel on the ceramic bead/epoxy mix, you can reduce this time. This is also even cheaper than the tiles, which is far cheaper than the rubber backed stuff (for which I have the distaste that you have noted).

The point is, that if you do it nicely, and use the correct epoxy, (say it again Spriggs...USE THE CORRECT EPOXY) you only ever have to do it once.

I have tried the trowel on the ceramic bead/epoxy mix on a drive pulley as well as the usual non drive ones, with great success. No drive slip, no wear, and very belt friendly. All this despite being fully exposed to the elements and within 100m of the Atlantic Ocean!

My test work on ceramic lagging is now into its 6th year or so.

Two out of three rubber backed ceramics failed within 3 years, and the third is on the way out.

Only one out of three conveyors full of direct applied ceramics failed on me. This was due to the incorrect epoxy being used in this one instance, and the supplier still apologises to this day for the boo-boo.

The big dual carry conveyor has epoxy/ceramic tiles on the drive pulleys (and has multiples of 400kW drives).

No problems on the drives at all, and I would be interested to hear why people say this is bad for the belt. There is no sign of this at all that I have come across. Also on the Dual Carry, the low tension non-drive pulleys had plain rubber lagging though, most of which didn't last a year with all the sand about.

Regards

LSL Tekpro ■

Good day Larry et al..

Indeed it does take longer to epoxy the tiles into the shell than to stick on the rubber backed stuff.

You first have to shot blast the bare shell, and then epoxy on the tiles typically in three stages, thus rotating the pulley through 120 degrees at a time.

All this can take up to 3 days. However, if you simply trowel on the ceramic bead/epoxy mix, you can reduce this time. This is also even cheaper than the tiles, which is far cheaper than the rubber backed stuff (for which I have the distaste that you have noted).

The point is, that if you do it nicely, and use the correct epoxy, (say it again Spriggs...USE THE CORRECT EPOXY) you only ever have to do it once.

I have tried the trowel on the ceramic bead/epoxy mix on a drive pulley as well as the usual non drive ones, with great success. No drive slip, no wear, and very belt friendly. All this despite being fully exposed to the elements and within 100m of the Atlantic Ocean!

My test work on ceramic lagging is now into its 6th year or so.

Two out of three rubber backed ceramics failed within 3 years, and the third is on the way out.

Only one out of three conveyors full of direct applied ceramics failed on me. This was due to the incorrect epoxy being used in this one instance, and the supplier still apologises to this day for the boo-boo.

The big dual carry conveyor has epoxy/ceramic tiles on the drive pulleys (and has multiples of 400kW drives).

No problems on the drives at all, and I would be interested to hear why people say this is bad for the belt. There is no sign of this at all that I have come across. Also on the Dual Carry, the low tension non-drive pulleys had plain rubber lagging though, most of which didn't last a year with all the sand about.

Regards

LSL Tekpro ■

Dear Graham,

You do have many tails of whoa. Pretty interesting statistics of failure rates. I can tell you with a high degree of certainty, if it happened in OZ, they would chuck the lot.

Given that hundreds and maybe thousands of rubber backed ceramics are in operation there, with many years of service, I'd say you got bum equipment in SA or is that only for T-shirts.

On the note of troweling on ceramic, I have another tail of whoa. Island Copper, on Vancouver Island in Canada, tried it on a 4000 hp incline with ST-4000 N/mm steel cord belt. It ground down one side of the bottom cover enough, in one year, that corrections to the pulley face still caused the demise of the belt within one more year. Pretty expensive lesson. THe mine is now retired. This is not a condemnation of your concept, just a cautionary note.

This installation is within 100m of the pacific ocean.

Lawrence Nordell

www.conveyor-dynamics.com ■

Dear Graham,

You do have many tails of whoa. Pretty interesting statistics of failure rates. I can tell you with a high degree of certainty, if it happened in OZ, they would chuck the lot.

Given that hundreds and maybe thousands of rubber backed ceramics are in operation there, with many years of service, I'd say you got bum equipment in SA or is that only for T-shirts.

On the note of troweling on ceramic, I have another tail of whoa. Island Copper, on Vancouver Island in Canada, tried it on a 4000 hp incline with ST-4000 N/mm steel cord belt. It ground down one side of the bottom cover enough, in one year, that corrections to the pulley face still caused the demise of the belt within one more year. Pretty expensive lesson. THe mine is now retired. This is not a condemnation of your concept, just a cautionary note.

This installation is within 100m of the pacific ocean.

Lawrence Nordell

www.conveyor-dynamics.com ■

Hello Dave and Larry..et al..

Many thanks for that, your experiences make this all the more interesting.

One last comment from me, and that is it isn't just me is RSA who has these concerns on rubber backed ceramics, and our local supplier himself has deviated away from it in favour of the direct epoxy method from his experiences. Also, many mines are also changing over to the direct epoxy method, especially trowel on, as it is so cheap.

Our input to SABS 1669 part 2 which deals with lagging of pulleys is currently also dealing with the fact that the replacement ceramic epoxy lagging is thinner than the rubber backed equivalent, so if you replace one pulley in a dual drive pulley configuration your power balance can be destroyed. Once this is sorted, we may see even more users using it.

And Dave, regarding my T1 / T2, the Dual Carry has 400kW drives in pairs, thus making 800kW drive stations T1 / T3, and T3 / T2, no wear not a mark on the belt and in a sand dune area.

So finally, why do you think we have such differing experiences? We maybe in different countries, we don't appear to be on the same planet. (I even know of one guy here in RSA who still swears by the rubber backed ceramics...just to confuse me further.)

Regards

LSL Tekpro ■

Hello Dave and Larry..et al..

Many thanks for that, your experiences make this all the more interesting.

One last comment from me, and that is it isn't just me is RSA who has these concerns on rubber backed ceramics, and our local supplier himself has deviated away from it in favour of the direct epoxy method from his experiences. Also, many mines are also changing over to the direct epoxy method, especially trowel on, as it is so cheap.

Our input to SABS 1669 part 2 which deals with lagging of pulleys is currently also dealing with the fact that the replacement ceramic epoxy lagging is thinner than the rubber backed equivalent, so if you replace one pulley in a dual drive pulley configuration your power balance can be destroyed. Once this is sorted, we may see even more users using it.

And Dave, regarding my T1 / T2, the Dual Carry has 400kW drives in pairs, thus making 800kW drive stations T1 / T3, and T3 / T2, no wear not a mark on the belt and in a sand dune area.

So finally, why do you think we have such differing experiences? We maybe in different countries, we don't appear to be on the same planet. (I even know of one guy here in RSA who still swears by the rubber backed ceramics...just to confuse me further.)

Regards

LSL Tekpro ■

Dave..

Indeed concentricity is important, and I have seen some pretty lousy out of rounds where the trowel on method has been used.

For epoxy / tiles however, the concentricity is better because the standard tiles are exactly 6mm thick and the epoxy is only 2mm thick. It is therefore easy to get concentricity to within 1mm.

This makes 8mm which is therefore well short of the 12mm for the other lagging as stated earlier for the drive pulleys.

I use 10mm thick tiles on the drives for this reason, but also with 2mm epoxy. As a result the concentricity is good.

I am also having good results with plain tiles (i.e. unembossed) on the drive pulleys. It is cheaper and also probably more belt friendly

Cheers

LSL Tekpro ■

Dave..

Indeed concentricity is important, and I have seen some pretty lousy out of rounds where the trowel on method has been used.

For epoxy / tiles however, the concentricity is better because the standard tiles are exactly 6mm thick and the epoxy is only 2mm thick. It is therefore easy to get concentricity to within 1mm.

This makes 8mm which is therefore well short of the 12mm for the other lagging as stated earlier for the drive pulleys.

I use 10mm thick tiles on the drives for this reason, but also with 2mm epoxy. As a result the concentricity is good.

I am also having good results with plain tiles (i.e. unembossed) on the drive pulleys. It is cheaper and also probably more belt friendly

Cheers

LSL Tekpro ■