Re: Ceramic Pulley Lagging
Hi Larry,
I am not going to reply to you point by point but the reservations you are having very much tally with my experiences with ceramic lagged drives with high tensioned belts. In designs/systems I have been involved in I have found it absolutely essential that the transitions are right as any uneven tensions across the pulley face tends to destroy the lagging and in some instances create bad belt cover wear on the cover face that contacts the pulley. In another instance the slight longitudinal cable stretch variation that can occur with 45 degree troughs combined with the high belt tension had an effect. In all instances the conclusion I reached was that as there is absolutely no "give" in the ceramic lagging any slight differential in the way the belt contacts the pulley face can lead to slight speed differentials thus creating the shear and/or wear issues when combined with the overall very high face pressures that occur between belt and pulley in such high tension applications.
Going down the lines you are taking may both add to and further explain the experiences I have seen. In at least one instance we reverted to rubber lagged pulley and while the rubber lagging did not last as long the serious problem of abnormal and serious belt wear disappeared. By the way one instance you know well where this has been an issue (I don't know what has been done recently) is CV555 at Channar.
Like you I look forward to the inputs of others
Regards
Col Benjamin
Gulf Conveyor Systems P/L ■
Lagging
Ceramic, like any lagging has it's pros and cons. I would contact Rema Tip Top for in depth assistance on this issue. ■
Re: Ceramic Pulley Lagging
I would not recommend you contact Rema tip top, because as far as I know they do the rubber backed stuff.
I have never known rubber backed stuff to last as the tiles fall out and the rubber comes off.
The only ceramic I recommend (as discussed at length in a previous thread) is to adhere smooth cramic tiles directly to the pulley shell.
I don't use the tiles covered in those little nipple things even for drive pulleys. They work fine without them and you don't have the danger of them shreding your bottom cover, if the pulley is not properly aligned.
Anyway, the important things are:
- Properly prep the shell before applying the Epoxy, and
- USE THE CORRECT EPOXY.
The expert to contact if Faan Viljoen here in South Africa at Multotec... Larry I think you already contacted him
Cheers
LSL Tekpro ■
Re: Ceramic Pulley Lagging
Yes, I did contact them and they were helpful. I thank you.
However, as I stated above, I have now become informed ,by a client, of grave and unacceptable belt pulley cover loss attributed to ceramic tiles glued directly to the pulley surface. The client is adamant that the non-compliant tile base is the cause of the belt cover failure.
As a consequence we have now investigated the reason for tile debonding from the rubber matrix. We believe we understand the nature of tile debonding and have conceived a solution. We have developed a means to reduce the maximum localized Von Mises and shear stresses to less than half the typical tiles.
Another point, does the typical tile with nibs configuration cause loss of integrity of the 1-2 mm of belt's bottom cover which in turn results in an increase in the rubber rolling drag? Normally, power should drop with time in service. This phenomenon is now being studied. Our FEA analysis shows a dramatic stress increase in the belt's cover around the nib edges. This stress seems sufficient to cause a failure in the polymer intergrity.
To date, we have only analyzed the stress field with the tiles embedded in the rubber matrix. Shortly, due to a client's claim of bottom cover failure with direct bonding, we will make this a part of the study. ■
Re: Ceramic Pulley Lagging
Larry
I hear what you say about the nibs..
That's why I don't ever use them, and I have no problem with bottom cover wear.
Cheers
LSL Tekpro ■
Re: Ceramic Pulley Lagging
Graham,
What is the surface geometry of the ceramic tiles you use?
Larry ■
Re: Ceramic Pulley Lagging
I use the 6 x 25 x 100 tiles for non-drive and 10 x 25 x 100 tiles for drives.
The extra thickness of the drive tiles makes the diameter of ceramic lagged drive pulleys the same as for rubber lagged, so they are interchangeable.
Note also.... Faan Viljoen says it is important to only use MM660 Epoxy.
Cheers
LSL Tekpro ■
Re: Ceramic Pulley Lagging
Graham,
What is the surface geometry. Is it smooth or lumpy or? Can you post a photo?
Hopefully, its not the dreaded Micke sand paper like material that causes caking on the surface and destroys the belt's bottom cover. ■
Re: Ceramic Pulley Lagging
Larry
Its not like sand paper, but conversely it is not dead smooth. Faan Viljoen gave me a shaped rod of it made into a presentation carving knife sharpener with a smart wooden handle.
It worked for a while, but is now somewhat too smooth to sharpen my pangas.
This is why it is bottom cover friendly. I also haven't had any problems with drive slip.
Some people use ceramics to be able to increase the coefficient of friction. I don't. I still use 0.35 and simply enjoy the benefit of much longer lagging life.
Cheers
LSL Tekpro ■
Re: Ceramic Pulley Lagging
Graham,
Are you saying the ceramic are not tiles but rods? I note the dimensions of 6 x 25 x 100 mm or 10 x 25 x 100 mm. Were is the rod? Do you have any photos of an installtion? Can Faan send along a catalog? ■
Re: Ceramic Pulley Lagging
Larry
Faan makes the ceramics into any shape you like.
What I was getting at was that the same ceramic material, made into a knife sharpening rod shape, behaved as I described.
To contact Faan for info, use :...
faanv@multotec.co.za
Cheers
LSL Tekpro ■
Re: Ceramic Pulley Lagging
Sirs,
We are using cermic lagged pulley for last two years. It has solved belt slippage problem.
We have oberved very less no. tiles getting detached from rubber base. We have observed scratches on some part of bottom cover.
The motor rating of two yard conveyors is 200 KW and 125KW. The approximate counterweights in these conveyors is 9MT and 7MT respectively. And belt rubber is M24 grade.
I would like to know upto what tension ratings, it would be advisable to use cermic pulley lagging.
Regards, ■
Re: Ceramic Pulley Lagging
Urwithdilip..
I find it hard to believe that in 2006 someone designed you a conveyor which resulted in belt slip.. to the extent that you had to put ceramic lagging on to solve the problem.
(It simply re-inforces the philosophy that people should get experienced materials handling engineers in to design conveyors properly.)
Concerning your rubber backed ceramic lagging, I fear that now is the time for the tiles to start falling out.
Up till now, mine started to fall out after a short time like this, which is why we have banned rubber backed ceramics totally.
We have had good success and life with un-nibbed ceramics directly glued on with epoxy as I said above, and in previous threads.
I have done numerous drives up to 400kW with multipes up to 1.2 Meggawatts with this method and this has had no ill effects on the belts.
Cheers
LSL Tekpro ■
Re: Ceramic Pulley Lagging
Thank you sir,
Actually the system was designed way back in 1996, and we encountered the problem of belt slippage mostly during monsoon periods.
So, respecting your experience one may go upto 1.2Mw drives with cermic lagging.
Once again thanks.
Regards,
Dilip ■
Re: Ceramic Pulley Lagging
Indeed...Dilip
Going by the performance of the 1.2MW drive, I would not hesitate to put in drives of greater power using this method.
Cheers
LSL Tekpro ■
Re: Ceramic Pulley Lagging
Graham,
I would note the surface testure of the Multotec tiles does differ from Rema Tip-Top and Richwood. This is what I asked in earlier emails.
This may make the difference with the damage caused to be belt"s cover. WIth this surface geometry, I wonder if it can develop the same driving toqrue?
We are about to conduct some laboratory testing to identify the surface mechaniisms that contribute the most benefit to driving torque. We have already produce FEA on some types of surface geometry. Have you already looked into this detail? ■
Re: Ceramic Pulley Lagging
Larry
The thing is that if you use mu=0.35 with the "smooth" (un-nibbed) Multotec tile, the pulley can be reliably used to transmit the drive torque. This is unless you are conveying something awkward like soggy carnalite or similar (then even use mu=0.12).
I have never used Rema tip top ceramics other than nibbed rubber backed. So I cannot compare the relative effects of different smooth tiles from different manufacturers.
Multotec ceramics are pretty much the only ones that I have had success, with so no need for research, as they are plentiful, and Faan knows that I would do really disgusting things to his chickens if he tried to rip me off.
Cheers
LSL Tekpro ■
Re: Ceramic Pulley Lagging
Graham,
Most users wish both long life and high torque capacity. You only want long life or so it seems.
We have experimented with various surface configurations knowing that the present designs are mean to rubber whether in matrix or not. We wish to obtain a higher torque transmission, higher bond strength and higher wear life. Maybe these need a new surface design and maybe a new (epoxy?) bonding mechanism.
I am searching to understand if someone has already completed this process. No need to invent to obvious. That is the reason for the start of the thread. Rema, Richwood, Flexco (Bell Bane), Corrosion Engineering, and Multotec are only a few of the many suppliers. ■
Re: Ceramic Pulley Lagging
Exactly so Larry...
I got the ceramic lagging life and belt life now, with torque which is quite adequate for me.
It all started some years back, when I had some rubber lagging which, when used even on non-drive pulleys of an overland conveyor, in conjunction with a Goodyear belt with their (then) new more abrasion resistant covers, lasted about two weeks.
I had piles of rubber fibrils on the floor on each side of the tail pulley for example. You could actually see the fibrils leave the lagging in a sort of black cloud. (Tests showed that there actually wasn't that much wrong with the rubber lagging.)
It was then that I decided to go the ceramic route and am now satisfied with my lot, having had numerous bad experiences along the way I might add.
Cheers
LSL Tekpro ■
Ceramic Lagging
Gentlemen,
I have read with interest this discussion and I am surprised that more has not been made of the fact that the belt length will change when the tension drops from T1 to T2; with textile reinforced belting this change in length can be quite significant. It is well known that on a plain drive pulley, or one with rubber lagging, only part of the arc of contact is in static frictional contact and in the second part of the arc, creep or slippage will occur between the belt and the pulley, hence the much reported belt wear problems. This creep is due to the change in belt length and the torque being applied. With ceramic lagging the relationship between the two surfaces becomes more complex due to mechanical locking between the protrusions on the tiles and the belt and I believe that much higher shear stresses are developed in the bottom cover when ceramic tile lagging of this type is used. It is therefore important that the tiles with the protrusions are mounted on rubber so that the tile can move and compensate for the change in belt length. These high shear stresses in the bottom cover most likely account for tiles being ripped out and for textile reinforced belts to suffer multiple transverse tears in the bottom cover.
In Graham’s case he is using smooth tiles bonded directly to the pulley, so some creep must be taking place and some belt cover wear would be expected. He has also stated that he is using a conservative coefficient of friction, which means a low T1/T2 ratio. There are also commercially available rubber/ceramic lagging types that have smooth tiles and these are very good for avoiding wear on non driven pulleys.
As Col has pointed out above, if the drive pulley is located at the head pulley then the T1 tensions will not be uniform across the belt and some areas will have a higher T1 tension than others and this will compound the problems of creep and wear.
Based on a review of a number of unexplained multiple splice failures, I believe there is evidence to suggest that when designers use a high T1/T2 ratio combined with ceramic tile lagging with protrusions, the high shear stresses developed may also impact on the splice failing.
In addition, some of the ceramic tile laggings available only support 50% of the belts surface and this can increases the pressure between the belt and the pulley to unacceptably high levels.
For the above reasons I believe designers should think very carefully before using ceramic tile lagging with protrusions in conjunction with a high T1/T2 ratio particularly on textile reinforced belts. Some designers are tempted to use a high coefficient of friction so that they can use a lower strength and therefore less expensive belt but in reality, the extra shear stresses may well warrant a higher belt safety factor, which will negate any perceived benefits.
I have personally had very good experience with Belle Bane rubber lagging, which has a diamond pattern plus transverse groove that allow the rubber to deflect to compensate for the change in belt length. I believe Hamersley Iron achieved better than 15 years life with this lagging type on the original 700 kW drives at Channar.
Dave Beckley
Conveyor Design Consultants of WA
Perth, Western Australia. ■
Re: Ceramic Pulley Lagging
Hi Dave,
I think the points made by Dave are very much in line with the observations I have made. I am not however convinced that the rubber backed ceramics will give enough flexibility to compensate for the shear force changes with very high tension belts. In many cases the belt lengths disguise the bottom cover wear ie the wear is not a significant issue as far as belt life is concerned (eg Channar) but this has not always been the case as evidenced by the coal mine reference I referred to in my earlier posting. Ceramics are also far less forgiving if transitions etc are poorly designed or installed. In far too many cases ceramic lagging is being retro-fitted because of poor rubber lagging life when in fact the rubber lagging wear is symptomatic of other issues. The problems encountered I feel are more about design fundamentals than the design of the lagging per se
Col Benjamin
Gulf Conveyor Systems Pty Ltd ■
Re: Ceramic Pulley Lagging
Hi all..
I have just returned from Sishen Iron Ore Mine where a couple of my young engineers have been hot commissioning the materials handling system for the big expansion there.
One of the new conveyors feeding a new stockpile has a single 750kW drive on a ceramic covered drive pulley.
It uses the nibbed type ceramic tile directely bonded onto the steel pulley shell.
The belt is St 2000.
The conveyor has only been running for 3 weeks so far, but I inspected both the pulley and the belt. Both are as new, and there is no evidence of any trauma to the the belt.
(The reason for the nibbed tiles is that the engineer wanted a relatively high mu for the single drive application combined with the concave profile)
Cheers
LSL Tekpro ■
Re: Ceramic Pulley Lagging
Dear All,
The points made by All are the reason for the posting of this thread and to engage in dialogue that may shed light on what is or is not known by research, by observation, or by intuition of belt dynamics in contact with pulleys related to driving force and damages.
CDI has been conducting analysis on various forms of ceramic tile shapes to better understand the physics and critical criteria where degradation takes place between belt and ceramic tiles and between tiles and rubber when the tiles are bonded to the pulley using a rubber matrix. We have come to believe the geometry and placement of the ceramic tile surface plays a large part in its success or failure.
We too believe the tiles can damage the belt or loose competence for various reasons. There are a number of mechanisms at work:
1. apparent friction of surfaces in contact
2. belt-to-pulley contact pressures, shear work, and contact angle
3. belt cover rheology and bonding rheology
4. tile geometry, texture, composition and placement accuracy
5. .........
Our purpose is to see if there are "best practices" that can be documented by analytic tools, or there are new methods which may show promise over the existing lot.
We see the need to apply better wear and coefficient of friction performance measures than are published in mfgrs. literature. The literature does not give any negatives or product limitations. Yet we see many installations with damage to belt and damage to tiles. Does success in one area dictate to all areas? Obviously not or we would see a clear winner by now. So what are the limits and why? ■
Drive Traction
Hi Larry,
What we really need is a better understanding of the drive mechanics. As you are well aware what Euler gave us with a leather belt or a rope on a polished cast iron drum is not suitable for designing high power belt conveyor drives. The inadequacies of the standard rope friction equation tend to be compensated for by designers reducing the value for the coefficient of friction of rubber on rubber from 0.7+ down to 0.25 or less to prevent slip occurring
We need a new formula that includes at least the following variables:-
Effective tension, wrap angle, realistic static and sliding coefficients of friction, pulley diameter, belt speed, the elastic modulus of the belt, the thickness of the cover rubber and its shear modulus, the thickness of the rubber lagging or the base rubber for tiles and its shear properties.
The person who solves this one will go down in the history books as an engineering hero.
Regards,
Dave Beckley
Conveyor Design Consultants of WA
Perth, Western Australia
www.cdcwa.com.au ■
Re: Ceramic Pulley Lagging
Hi All,
I would add a couple of other issues besides what Dave has put in.
1) The current published methodologies for designing transitions I believe are inadequate. If the transitions are not right in all circumstances then the face pressure over the head pulley will not be uniform. This is particularly the case when we have a drive pulley at the head.
2) The effect of water, fine dust and other environmental issues including temperature all have an impact. As Dave says, what we do now is use a much lower friction factor but the dynamics with a more rigid surface such as ceramics is far different than with a rubber surface and what we have done is followed what we do with rubber without looking into the differences in the 2 materials.
Col Benjamin
Gulf Conveyor Systems Pty Ltd ■
Alumina Ceramics, Zirconia Ceramics & Zta
Wear resistant ceramic lining – Alumina, zirconia & ZTA
Ceramic grinding media – alumina & zirconia
Steel & rubber backed ceramic plate
Pulley lagging
https://aluminaceramics.wordpress.com/ ■
Ceramic Pulley Lagging
Dear All:
I have been confronted with many field studies on ceramic pulley lagging. In searching for the latest-and-greatest ceramic tile lagging, a number of issues have occurred that question some wisdom and cloud prudent recommendations:
1. Size, shape, location of ceramic tiles - recent high powered conveyor had tiles pulled off the pulley rubber surface. Experts reported on a fix that proved not to work. In part, the fix was to increase the spacing between tiles. A mathematical arguement was presented. When Finite Element Analysis (FEA) was applied, the sparse tiles showed a higher Von Mises and shear stress than closely spaced tiles. Are there success stories where sparsely spaced tiles show better performance?
2. Anchor ceramic tiles to drum directly using an epoxy. I guess it worked in some locations. However, on at least one high powered systems, it highly degraded the belt bottom cover and forced a belt replacement. Client was very upset with the lagging and removed the ceramic tile expoxy lagged pulleys. Are there other case studies that have a similar outcome?
3. When using ceramic tiles, the belt bottom cover needs to be designed to be compatible with the tile design and rubber matrix that contains the tiles. Published papers argue that there is an optimum belt bottom cover thickness for ceramic tiles that will not degrade the belt's bottom cover. Is there a concurrence on this issue? Is there a limit on belt-to-pulley normal pressure and shear stress for which ceramic tiles cannot be used?
4. Finite Element Analysis (FEA), performed on typical tile patterns used on high powered pulleys, show the point where the shear stress will cause the tiles to debond. This seems to lead to an alternative shape and attachment that may cut in half the maximum shear stress and local strain fluctuation. Are there any new ceramic tile shapes, other than conventional tiles with little nibs, that are being promoted?
5. Is anyone aware of the belt-to-pulley pressure required to fully engage the 20 mm square tiles with 1.0 mm little nibs? We note the nibs are not always oriented in the same direction. Should this matter? THis study beings into focus on how the ceramic tiles work?
6. There seem to be many tile formats- square, round, diamond, long and narrow, ...... Does anyone know the arguements for why the differences and which is the best for today's high powered belt designs?
7. Worst of all, is anyone aware of the loss of conveyor power due to the use of ceramic tiles with 1mm high nibs? ■