1. arkangel Guest
How long an standar SBR belt will last? an average, with cold climate and abrasive conveyed material (dross like sand texture) 36inch and 200TPH

Dear Sir,
belt lifetime is influenced with high amount of parameters and teoretical calculation is difficult, because some influence factors multiply and some of them are independent. To determine the belt lifetime we use teoretical calculation and data acquired from several years long monitoring under specific condition. In case that the customer does not have such information, we are able to find in our database the conveyors with similiar operational conditions.

For basic estimation of belt lifetime we need following parameters:
- axis length of conveyor
- length of the belt
- speed of the belt
- how many hours per year the belt is conveying the material
- type of the belt (information from producer)
- thickness of top and bottom rubber covers
- category of rubber (X, Y or different category used by producer, all information on stamp)
- information about conveyed material (type of material, lump size)
- from which height falls the material on belt and under which angle

Is your question related to belt you intend to replace or to new belt which is prepared for use. If this material is conveyed by more conveyors, do you have related information about lifetime of previously used belts? If yes, can you draw wear profile of rubber covers. We are interesting in which place the belt wears most quickly.

Are you using high volume of conveyors and are you interested in long time monitoring of belt lifetime?

3. ## Belt Wear Predictions

Dear Sir:
We have developed a wear prediction method based on modeling the granular flow dynamics as defined by the impact and shear work between particles(granular medium simulating ore bits) and belt or liner surfaces.

Temperature drop alters the viscoelastic properties, specifically it increases the Dynamic Modulus(E') and Loss Modulus(E'') of rubber below the glass transition zone (varies with rubber - usually about -30 deg C). This is similar to inceasing the strain rate. If the rubber is dynamically strained due to high impingement velocity it may not be able to comply resulting in excessive wear. The concept can be physically modelled mathematically, if the rubber, granular dynamics, and geometry properties are definable.

Field measurements will lead to better understanding of the wear mechanisms. We have published our approach. Contact me if you have further interest.
Lawrence Nordell
Conveyor Dynamics, Inc.
phone 360/671-2200
Fax 360/671-8450

4. Dear Arkangel:

As both respondents have indicated, there is more involved with projecting belt life than the type of belt being used and the material being carried. I have inspected fabric carcass SBR cover belts that are in excellent condition after thirty plus years of service (minor top & bottom cover wear only). I've also seen belts which have worn out within weeks.

Belts should not wear appreciably, if they are treated properly. This includes "gentle" loading, properly adjusted skirting and cleaners, and good preventive maintenance practices. Abrasive materials can wear a belt out quickly if allowed to slide against the belt surface, which is not what a conveyor belt system is designed for.

To give a guess, based on the information you gave and based on an intermediate level of system design and preventive maintenance a belt on your system would likely require replacement after 7 to 10 years. This reduction in service life from the original example reflects the general overworking of maintenance staff, that prevents a good PM program.

Hope this helps.

5. ## Belt Wear Life - Sand

Another posting

SBR is used to stabilize sun and ozone. Natural rubber has a better abrasion index. For this installation, material, proper cover selection, belt speed, and chute loading, and cycles of wear - the belt could last your life time.

We installed, in 1987, a ST-6600 N/mm, 1800mm 6600 t/h 4 m/s loading at 16 degrees conveyor transporting primary crushed copper ore (-300mm). The first belt wore out 18mm top cover in 3 years. The new chute increased the life an estimated 20-30 years. Belt is due to shut down after 8 years. Still has most life left.

Lawrence Nordell
President
Conveyor Dynamics, Inc.
1111 West Holly St.
Bellingham, WA 98225
USA
ph 360/671-2200
fx 360/671-8450
email nordell@conveyor-dynamics.com
www.conveyor-dyamics.com

6. ## Belt life

Dear Sir,
I fully agree with Mr. Nordell as in INDIA with proper maintenance the expected belt life is 15-20 years.
Regards.
A.Banerjee

7. There was a section dealing with belt life predictions at the back end of the old grey Yokohama conveyor belt manual. Can anyone recall the name/title of the formula quoted in the procedure?

8. Dear Mr. Arkangel,

While predicting the belt life, it is essential to know about the features influencing the belt life. These are mainly as below :
1) Belt carcass weakening due to impact strain by the lumpy material.
2) Belt carcass weakening due to bending cycles and starting condition i.e. whether frequently applied sudden loads or gradually applied loads.
3) Belt cover wear at loading zone due to incoming material velocity component along belt and perpendicular to belt. The difference in velocity along belt contributes to the quantum of abrasion and perpendicular component will contribute to the pressing intensity of the abrasion.
4) Belt bottom cover wear while travelling on carrying run due to installation tolerance i.e. roller axis not being exactly perpendicular to belt travel.
5) Belt bottom cover wear due to casual slip between belt and drive pulley periphery particularly during start-up and inadequacy of the take-up tension. A properly designed and maintained conveyor would not have such occurrence.
6) Belt top cover wear due to subtle rubbing of the material on belt, during course of travel. As stated by Dunlop, this aspect cannot be ignored.
7) Belt top cover wear while travelling on the return run due to tolerance in idler installation i.e. roller axis not being exactly perpendicular to the belt travel.
8) Belt exposure to direct sunlight and surrounding atmosphere that means whether conveyor belt is open to the sky or it is in an enclosed gallery. This contributes to belt ageing, deterioration etc.
9) Proper design of take-up and regular upkeep of tension if the belt tension magnitude is maintained by manual screw take-up or motorised winch adjustment by manual attendance.

As can be seen the belt life depends upon quality of design, quality of installation and also on quality of maintenance. It is also influenced by the quality of feeding equipment i.e. whether such equipment are maintaining feeding as per design condition or feeding erratically.

There are design and calculation procedures to predict belt life, however while predicting such life it is essential to make a qualitative assessment of aforesaid points. The belt life prediction independent of the aforesaid points would be unreliable. The calculation procedure together with the feedback from industry gives reasonable judgement.

Although the situation may look quite complex but for business organisation doing business in a particular sector of industry do not find difficulty in this matter. For example, particular company dealing with coal handling plant, already have the feedback about the life the customer is getting in context of the prevailing design practice, quality of the engineering and quality of installation & maintenance. During service tenure we could easily tackle such matter for the concerned industries. Often talking to the plant operator provides factual information.

Because of the interdependence of the belt quality and the conveyor quality, the belt manufacture is rarely able to give formal guarantee for the true expected life. He has to only consider such guarantee on safer side because many of the factors affecting the belt life are not under his control.

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.
Pune, India.
Tel.: 0091 (0)20 25871916

9. Dear Mr. Mulani,

Some of your comments are valid if you consider designing a conveyor with inherent defects or poor design criteria. It is not clear if you are advacating for good conveyor design or belt design. Proper and modern design criteria will account for many of your points impacting the belt's life such as items:

1. Impact (gouging) resistant design due to know forces can be made tolerable with good chute design

2. Starting and stopping sudden events only influence belt cover life is there is drive slippage.

3. Modern chute design mitigates this event by multiples

4. True only with bad installation practices - modern installation criteria eliminate such wear - this must be considered with the other noted good practices

5. With proper design the event is nil

6. In all my years of design and evaluation of plant and overland belts, I have never seen such an event. I have heard engineers talk about it. Maybe you can offer some installation references. We can deduce the nature of product retardation with respect to belt motion. The product moves maybe 100-200mm over a 10 km length of level (horizontal belt). It usually occurs when the product is lauched over the idler. The normal force is very small compared to the forces from chute impact and product slip to speed.

High inclines can have pronounced slip between product and belt. This has been studied in some depth to correct for weigh scale readings. It amy become a wear issue if severe. Usually, this would occur with other obvious problems such as capacity and spillage.

7. The same as point 4.

8. Aging produces oxidation. High temperature will accelerate ageing. Ultravilet attack is another ageing mechanism, as there are many other cover damaging methods such as iron ore and coal ores that suck out the plastisizers - big problem if the manufacturer does not correctoly compound for the product.

9. ????

10. Missing:

a. Designing for gouging verses abrasion resistance
b. Idler junctions stress failure
c. Trough angle - 45 are worse than 35 degrees due to higher pressure
d. Shorten center roll influence on idler to belt pressure and slip
e. Idler spacing more will produce more wear? Maybe not.
f. Forward tilt of idler rolls - can produce unacceptable wear if yield strength of rubber is exceeded. WHo practices such analysis?
g. Skirtboard design against trapping material and grooving belt
h. High wear due to rip detection loops increased stiffening at impact point

This list can go on and on. The point is the overall design against unacceptable wear is very complex.

10. Referring to my earlier reply and Mr. Nordell’s response; small clarification is as below for the numerous readers.

I have drawn attention to various points, so that concerned designer (and the people introducing design related decisions), take care of these aspects to get better design, better equipment and better life of not only for belt but also for other items as an integrated approach. This is not in context of particular method or it is not addressed to experts or internationally top class conveyor designers. I stand for best of the design and equipment.

I am referring to huge number of conveyors and plants, ranging from small to large, and as constructed across the world, and not to exceptional segment of conveyors. In the world scenario where huge number of conveyors are being made, we are not in the picture in their design etc. All the plants obviously will have workable design-construction, but workable design-construction does not imply perfection on all counts, by all the people. The workable design will have degree of imperfections, and thereby resulting life would be accordingly.
In a broader perspective, unfortunately business situations rarely provide free hand to designer all the time. Sometimes he is constrained by the market price, buyers technical preferences / beliefs / insistence, land constrain, own purchase department preferences, and so on. Such complexities are ground realities in business activities, wherein workable (or excellent workable) design is certainly achieved by them, but it will have different shades of perfectness. And so we see very good plant, good plant, average plant etc.

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.
Pune, India.
Tel.: 0091 (0)20 25871916

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