I don't know of a "Scientific" method. It generally takes an experienced belt technician to make a determination. This is based years of field experience. Further, there are ways to do non-destructive testing in splices or damaged areas. Fenner Dunlop provides X-ray services that would fit your needs. The x-ray testing is best for singular/specific areas - like splices. The result can be emailed is has outstanding resolution.

Buddy WIlson

Application Engineer/TSM-Southeast

Fenner Dunlop Americas ■

As I know for the wire rope, factors related to the residual life including external wire broken (visible), corrosion (not common),internal wire broken(weak magnetic inspection) and fatigue(weak magnetic inspection).

Standard applied in many countries emphasis external wire broken is the key to determine resdual life for a wire rope but if you read this article you'll realized it's just another experience based "solution"

http://books.google.com/books?id=UMC...20rope&f=false

It's the same case for conveyor, so far, all these standard recommanding the determination of the resdual life for conveyor is bascally the same as that to determine resudal life for wire ropes.

You may wanna try some professional monitoring equipment if budget is sufficient. Otherwise experience based decision should be the "best available" determation for this issue. ■

Originally Posted by sganesh

Conveyor belt joints conditions- Any Scientific Method?

Dear Experts,

For many mechanical equipments, we have certain condition monitoring devices like pressure gauges, temperature gauges, vibration readings, thickness gauges etc. In wire ropes and load carrying members, we measure the diameters or count the number of damaged wires.

These methods help us to have better decision to know about the residual life, particularly whether these equipments need to be changed or not.

Like the above examples, are there any scientific methods to know the strength and residual life of the joints of conveyors? Many times I find the decisions are purely based on individual experience which varies from person to person.

Though my question targets for the hot vulcanised joints of fabric belts, I welcome the answers of cold vulcanised joints and hot vulcanised joints of steel cord conveyors also.

Thanks & regards,

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visually inspecting splices is a general rule anyway as separations can be easily seen with close inspection.

All my experience is with belt using cordage weaving and mechanical splices where splice conditions are monitored visually to determine the joints condition, and in general the splices were cut out and replaced every year with no exception (this is was done /still being done with belts that are mounted on towers delivering to stockpiles etc. (with splices that have dutch man edges). ■

Unfortunately the question has many answers:

1. Area dimension of a fabric splice does have some bearing on its fatigue strength within the area of the splice, but is more importantly involved with where the area is removed: Side, center, symmetrical, non-symmetrical, random calico such as with punctures, et al. Once you see the stress-strain flow, this leads to regions that are more sensitive and less-so. Reverse-Calico could be another name for the Super-Screw.

2. Untill recently, where we have studied fabric splice for pipe conveyors, we offered published mapping of the stress-strain flux magnitude in steel cord belts. Each are of rubber and steel cords were evaluated, tested, and optimized for rubber engagment, for size of wire cord for same strength, butt end clearances and type of materials, number of steps, bend zone lengths on leading edge and trailing ends of splice field, staggering of individual cords, bias angle, etc. See Bulk Solids Publications by Qiu, Sethi, Nordell in various issues and issues outside of BSH.

3. For fabric splices, there are additional choices for strength besides the mfgrs. published recommendations including knowledge of stress and strain flow and how to regulate (reduce) magnitude of strain flux. There are multiple ways. You can have multiple variants of 2, 3, 4, 5, and 6-10 step splices. By example, a 3-step splice can have individual patterns designated 123, 132, and 213, with some applying 12333. Numbers indicate the partion of the splice into equal catagories of the total overlapping length. Each has its weaknesses and strengths assuming the cord diameter has been optimized. Then there are the splices where the overlap lengths are not equal. There are splices with joggles that have differing rubber gaps between steel cords.

4. Splice strengths are not equal for differing cord constructions and core gum rubber suppliers.

5. Core gums can show great promise with H-Block dynamic cycling of 3 or 5 wire coupons, but, will not do as well in a multiple stage splice because of poor load sharing characteristics of rubber moduli differences between suppliers.

6. For pipe conveyors, often in longer, high lift, and high tonnage belts you need both fabric and steel cord reinforcement. Kevlar can also be included in this discussion. In addition, steel cord splices are often enhanced with fabric plies to improve common splice pattern dynamic strength. These differ according to the task at hand.

The subject is very complex and does not lend itself well to simplifications. Within each catagory above there is a significant amount of research that has been applied, tested, materials reformulated, and so on. The process for improvement continues with questions like what should the Belt Safety Factor be? It differs with the application. Unfortunately, these interesting questions and their answers will not be found in Standards, Mfgrs. guidelines or academic publications. Only, until recently have we been able to configure the full context of splice construction using Finite Element Analysis (FEA). Even here the orthotropic strain-energy equations differ between FEA codes. ■

Mr. Ellis,

The original question was: "are there any scientific methods to know the strength and residual life of the joints of conveyors?" To this question the answer is YES.

In high-strength steel cord belts (> ST-5000 N/mm), steel cord fatigue is of major importance. The steel cords can fail before the rubber fatigues due to the significant difference in bending stiffness between splice and parent belt construction. Special features are applied that mitigate this stiffness differential.

Published literature clearly answers why we apply:

1. Specific splice patterns and lengths?

2. Typical 4-step has many combinations to organize the cords (1234 or 1324, or 1342 or 3142) but not other combinations?

3. Splices reinforced with speciifc fabrics - some fabrics perform better than others

4. Large and costly machines built to study the many attributes of the splice?

5. Research work showing sensitivity of cord diameter to gap between cords

6. ST-5100 N/mm belt strength, with a 2-step splice, achieves 60% fatigue efficiency, while published DIN splice standards 45% efficiency with 123, or 132 splice depending on where you are doing underground or above ground with a similar belt construction?

7. In short, why and by how much does performance differ between splice patterns?

You opinion (NO), without stating any facts. What good is such a comment without stating knowledge? Constructing and cooking a splice does not make an expert. You assume all core rubbers perform the same, material composition and all wire ropes are created equal, fabric and no-fabric reinforcement is of equal importance, etc.

In reality, this is not so. Many competent researchers have made this discovery, published details, and moved on to improve splice strength using the many tools now available - FEA - Splice fatigue coupon testers - Splice fatigue testing with full scale splice from 1-step to6-step multi-stage and multiple repititions, changes in rubber compounds, et al.

CDI contributed to the designed, successful testing , and installation of a ST-8000 N/mm belt construction that achieved better than 50% splice efficiency. Then we altered the materials of constructions, but not the splice pattern, and raised the belt and splice to ST-10,000 N/mm while achieving about the same splice efficiency.

What have you contributed that we should consider your comments as sincere and insightful? ■

I Agree in part.

Too strong an opinion leaves no room to hide when facts negate opinion. ■

Originally Posted by WilsonBW

I don't know of a "Scientific" method. It generally takes an experienced belt technician to make a determination. This is based years of field experience. Further, there are ways to do non-destructive testing in splices or damaged areas. Fenner Dunlop provides X-ray services that would fit your needs. The x-ray testing is best for singular/specific areas - like splices. The result can be emailed is has outstanding resolution.

Buddy WIlson

Application Engineer/TSM-Southeast

Fenner Dunlop Americas

To clarify, my post was based on fabric carcass belting. You can, when installing the splice in the fabric carcass belt, insert metal sensors (discs really) on each end of the splice and take a reading upon initial installation as far as distance between the two. You can then use a monitoring system similar to that used on steel cord to continually measure the distance between the two discs. This can give you an "idea" of movement within the splice.

The same scanning technology can be used to on steel cord belting as well. But it is important to set a benchmark & then measure changes (ideally upon initial installation). In steel cord, if a benchmark is set, you can measure movement or changes in the splice (cracked, broken or corroded cords). I hope this is helpful.

Buddy Wilson

Applications Engineer / TSM-Southeast

Fenner Dunlop Americas ■

I submit an answer on how to measure residual strength capacity of steel cord belt splices. I had hoped the multiple suppliers of the equipment would respond. Apparently they are not reading the form postings.

Steel cord splice residual strength can be monitored and measured for remaining core rubber fatigue capacity by observing the growth of rubber displacement along the steel cord axis at the splice cord butt ends. Some knowledge of the rubber properties and splice pattern also need to be known. For instance:

1. Growth or displacement of opposing cords can be measured by plotting the progressive butt end displacement. Canada Conveyor Belt aka Conveyor Belt Technology (sic) have a monitoring system that use a magnetic dopler pattern to image the butt ends that has a resolution of less than 1 mm. Typical growth of some core gums are in the range of 0.5mm growth per 1000 belt full load cycles. These details will differ with core gum properties, loads, load history, splice pattern, and temperature at time of measurement, et al

2. Classify displacement of butt ends in a lab test jig as a function of time and load history. FEA splice pattern that give representative single cycle growth. All rubbers will grow with repeated strain and strain magnitude, et al. The rate will depend on splice pattern, splice loading, accuracy of construction of splice, plant and construction hygene (build-up on pulleys, straight running of conveyor, transition at head and tail, and vertical curve stresses and efficiency of splice with pattern and vulcanizing contractor). Regardless, the butt ends will grow according to load history and physical properties.

3. Plotting butt end displacement history with appropriate monitoring equipment will give operator knowledge of butt end growth rate and remaining life, if the splice has been analyzed for initial growth with expected nominal load. ■

This is not rocket science, simply use Super Screw belt joins for Hi temp belts.

We supply worldwide Super screw TR temp resistant to 200 deg C for belt joins on Hi temp Nitrile and EPDM belts.

A join can be completed in a matter of hours and all is needed is a cordless drill.

Check this video or visit our website at www.wabelting.com.au

http://www.youtube.com/watch?v=Zfe-PHtsc3E

David Cotton

Director ■

Originally Posted by lzaharis

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visually inspecting splices is a general rule anyway as separations can be easily seen with close inspection.

All my experience is with belt using cordage weaving and mechanical splices where splice conditions are monitored visually to determine the joints condition, and in general the splices were cut out and replaced every year with no exception (this is was done /still being done with belts that are mounted on towers delivering to stockpiles etc. (with splices that have dutch man edges).

Dear Lzaharis,

Visual inspection is not an accurate method to evaluate the condition of conveyor belt or wire rope. Even though the close inspection will take forever to finish it, and the belt will be stopped only for inspection for one day long. ■

Dear Sirs

If in doubt, we do continious x-ray scanning of steel-cord conveyor belts and can subsequently detect failure of splices. For more information we can be contacted at cpands@mweb.co.za. ■