Mr. Sganesh,

In the context of your post you are asking about pocket belts (flexowall, beltwall, etc). I am not sure that breaker is the correct terminology for the cross-rigidizing reinforcement. Breakers imply impact resistance or energy absorption. Cross-rigidization is for flex resistance so that the flat belt does not dish between the corrugated walls and cleats. Dished pockets will gallop excessively as they travel of the carrying rolls, bouncing and spilling the bulk material. Also the belt must act as a one-way slab on the return, spanning between stub rolls and deflector wheels. Cross-rigidization requires steel wires that act as slab reinforcement of the belt and limit the dishing deflection. I cannot imagine that fabric plies, for this purpose would provide the required stiffness to limit the dishing deflection.

Joe Dos Santos ■

Hi SG,

As you say, this is a matter for the belt manufacturer. Absolutely. There are different cooling rates and consequent residual stresses to be addressed.

Have you any evidence of where the warp material is substantially different to the weft?

Are such belts offered in catalogues?

Personally I do not even know the degree of support within the cross cleats which span the flexible sidewalls. Is there any FEA illustration of the pocket belts available?

How long do these fancy types of belt really, honestly last? ■

Mr. louispanjang,

Indeed I have seen the guts of such a belt though not in the pocket belt but rather in the latest cable belt construction. The same (I assume) cross-rigidization is use at cable belt so it can support the bulk load as a one way slab between the carrying/tensioning wire ropes. parallel, rigid cross wires are at the top and at the bottom of the carcass, covered by the cover rubber. In the case of the cable belt I imagine that it is a one-way slab calculation not being greatly concerned with the deflection. Indeed some deflection will be desired to hammock the load. In the case of the pocket belts it is likely a one way slab calculation for support of the return on stub rolls and at the deflection wheels and a deflection calculation to limit dishing of the pockets and flex due to cantilevered load on the cross cleats.

Joe Dos Santos ■

Hi Joe,

My pons asinorum is the behaviour of the cross cleat junction with the sidewalls and main belt. If the sidewall is flexible enough to negotiate the pulleys and the cross cleats are vulcanised onto those sidewalls then there is questionable sustainment of the cross cleat during vertical/near vertical conveying.Similarly the joint between the cross cleat and the main belt probably offers even less sustainment towards keeping the cleat in a flat horizontal plane during vertical conveying. I imagine there is a trade off between sidewall flexibility and overall life.

I designed one of the earliest slewing vertical flexowell elevators of Bootle Docks, Liverpool, and it worked well. With time the geometric nicety becomes clouded,not by doubt but by possible oversight.

Do Flexowell ever read these posts? ■

I have seen cases where the cross cleats were bolted to the base belt and bolted to the corrugated side walls. I have seen cases where the cross cleats were vulcanized to the base belt and bolted to the corrugated side walls. I have not seen cases where the cross cleats were vulcanized the the corrugated side walls.

In principle, a very localized attachment to the corrugated side wall, even if it has length along a single corrugation, does not present a problem. The corrugations expand as they go around a pulley or contract as they go around a deflection wheel but the connection and alignment is preserved. When conveying vertically the load of the cross cleat onto the corrugated skirt is resisted by shear through the sidewalls not by tension on the corrugations. No doubt the force distribution is quite complex. This attachment does alleviate some of the moment of the cross cleat onto the base belt though not completely. The nature of the connection certainly implies that it is intended to take moment

My analysis here is quite speculative and it would be nice to have a pocket belt expert clarify these matters for us.

Joe Dos Santos ■

Mr. Sganesh,

I do believe that fabric reinforcement (plies) is being used as the strength reinforcement as well, but this is apart from the cross rigidization which is made up of cross-wire layers at the top and bottom of the carcass.

Joe Dos Santos ■

It is always best to follow the belt manufacturers recommended procedures for splicing whether it is steel cord or fabric.

For example here is Fenner Dunlop's recommendations for steel cord. Click Here to download the PDF. ■

Originally Posted by Joseph A. Dos Santos

Mr. Sganesh,

I do believe that fabric reinforcement (plies) is being used as the strength reinforcement as well, but this is apart from the cross rigidization which is made up of cross-wire layers at the top and bottom of the carcass.

Joe Dos Santos

Dear Mr. Santos,

Generally cross rigid fibre glass plies are supposed to be the best as they are wear-resistant. These are being used by some of the top manufacturers of base belts.

Rgds,

Rupen R Avalani ■

Didn't fibreglass weft originate in early cable belts? ■

Interesting, I am not aware of any fiber glass weft being used for cross-rigidizing of base belts for the pocket belt system. It is a matter of both strength and stiffness. The cross reinforcement, with the base belt carcass, creates a one way slab the is cross-wise stiff but longitudinally flexible. I would expect fiberglass to be less stiff than the cross rigidizingt steel wires. I could be wrong. How long has fiberglass been used for the cross-rigidizing of pocket belt base belts?

At the cable belt, that is a somewhat different matter. The original system used external cross-bars of steel, then they went to steel cross-bars embedded in the belt, then fiberglass bars embedded in the belt then, ultimately the cross-rigidizing wires, like the pocket belt base belts. The rationalization for the fiberglass bars, over the steel bars, was the desire for flex under load that would create a modest natural trough. I am not aware of fiberglass fabric or wires being used in cable-belts.

Joe Dos Santos ■

We have had interesting exchanges on this matter. I am curious. Are any of the commentators representative experts of the pocket belt manufacturers, such as Metso, Beltwall, etc? I know that I am not an expert on the Pocket belt technology and the cross-rigidizing of the base belt, merely a long time observer. The physical measure of cross-rigidity is an interesting one. I would love to hear from the experts of the companies that engineer and build the pocket belts.

Joe Dos Santos ■

Originally Posted by louispanjang

Hi Joe,

...

Do Flexowell ever read these posts?

It appears that the belt makers do not offer the information for examination, with (or for) learned comment, here or elsewhere.

Five years life, quoted by SG, suggests that, subject to availablity, a structure that supports a simpler troughed belt might often prove a more economic solution than a seriously expensive trade secret. Add to that the preceding evidence that manufacturers are reluctant to publicly discuss their products and the risk then encompasses OPEX as well as the original CAPEX.

(How's that for opening the door?) ■

Louis,

You have just made the best argument that I can think of for the Dos Santos Sandwich Belt High Angle Conveyors. They use all conventional conveyor components and equipment including smooth surfaced rubber belts that can be continuously scraped clean. I think that everyone in this forum knows that I have openly and prolifically published the basis for our technology including many project accounts. In my own early development of our technology there was the Loop Belt, which was my inspiration to take the technology much further, to its present generalization. The technical and theoretical basis for the loop belt could not be found in any publications at that time and was guarded in secrecy. The basis became obvious to me on further scrutiny. Not only did I determine the technical and theoretical basis for the Loop Belt, I developed it further, beyond the limiting C-shaped profile, discontinuities and compromising transitions. This is the Dos Santos Sandwich belt technology, open transparent and successful with many installations in operation.

I am sure that the same kind of scrutiny can easily reveal all of the secrets that the pocket belt manufacturers seem determined to hold. After all it is not rocket science. To this writer it is a highly specialized, expensive system that cannot be scraped clean and, with the availability of the Dos Santos Sandwich Belt systems, is not worth pursuing.

Joe Dos Santos ■

Just yesterday Phoenix opened a thread in 'News from Industry' introducing their aquisition of a small, relatively unknown, outfit from Norfolk, UK, who I thought had long since disappeared into obscurity. Perhaps someone from there will read this post and hasten to the defence of cleated sidewalls.

I live in hope....of more learned discussion. ■