Mr Banerjee,

The suitability depends upon the lump size of the various products that you are handling and the angles that you intend negotiating with the conveyor.

One important item often overlooked is that at lower capacities the the carrying ability of the pipe is no better than a standard conveyor so incline restrictions for materials on conventional conveyors apply.

Engicon Systems (Pty) Ltd

Tel +27-789-2102

Fax +11-789-9664

https://edir.bulk-online.com/profile...on-systems.htm ■

There is no reason to have a variable if you are satisfied that the mix of materials would not cause run back on a conventional conveyor. Idler indentation is quite pronounced on pipe conveyors and material agitation is more than you may imagin.

Providing you have a central controlled feed there and the above criteria is met you should have no problems.

With regard to pipe roll. This is dependant upon idler configuration, accuracy of manufacture and erection. Certain idler configurations make belt training easier and less prone to roll if all conditions are not perfect. You can open the forum to heated debate on that subect.

Your statement that you are compelled to use a pipe conveyor is odd. These conveyors are primarily used for difficult routing problems or spillage control, providing cleaning at the tail is not a problem. They should not be considered as solutions for inclines as more practical and cheaper solutions are available.

Engicon Systems (Pty) Ltd

Tel +27-789-2102

Fax +11-789-9664 ■

Dear Mr Banerjee,

I am curious to know why such a low speed has been selected. Since the 'packing' of material in a pipe belt is much more effective than in a troughed belt, the normal consideration of degeneration of lime (in particular) during conveying at higher speeds should not apply to the same extent. A low momentum pipe belt would not only increase the power consumption but would also call for a wider belt and hence higher costs than should have been required.

Further, since lime is exothermic in nature, are you considering a belt with heat resistant covers ?

regards

Kayem ■

If you are going to use heat resistant belt please check that it is suitable for pipe conveyors and is not to rigid, otherwise your power calculations will be out of the window. Also check that the belt is not liable to work hardening otherwise you will need a progressively higher power to run it as the belt ages.

Engicon Systems (Pty) Ltd

Tel +27-11-789-2102

Fax +27-11-789-9664 ■

Dear Mr Banerjee

In case of you pipe conveyor is properly aligned and trained , belt joints are perfect then your pipe conveyor will not tilt in any of the condition either fully loaded or partly loaded or conveyor running empty.

pipe size is to be selected considering about 70 percent filling with lowest density material.

There is no problem with heat resistace belt .

While designing conveyor you pl keep magin in Kw rating of conveyor this is required when belt is new sometimes it is more regid and require more power than anticipated due to additional load of new belt on pipe forming rollers.

Regarding lime degradation considering same speed on pipe conveyor or belt conveyor there should not be much difference except in pipe conveyor there is turbulance in material inside belt at the time of pipe closing and opening

A R SINGH ■

I do agree with many comments. However, some comments on pipe conveyors with circular (not oval) behavior may not be correct.

1. PIPE ROLL, TILT, TWIST, CORK-SCREW or ROTATION

Mr. Morgan and Mr. Singh noted that pipe roll or tilt ( rotating, twisting or corkscrewing) - it is dependent on idler configuration, alignment or training. This is true.

Idler alignment offsets are also applied to correct for pipe crossectional rotation when veritical and/or horizontal belt curvatures are applied along the longitudinal axis. This is in addition to, and independent of, basic idler training and structural alignment corrections.

When conveyor axial curves are used, the corrective action is only good for one crossectional loading case. Hence, the often noted requirement to use one idler tracking aligment or offset with one filling condition.

When the curved belt pipe structure is analyzed (made from a flat plate which has two free edges and is not a closed homogeneous isotropic ring) including its width overlap, one can intuit, or calculate the behavior due to the assymetry of internal and external forces acting on the pipe crossection that induces rotation, twist, roll et al.

Intuitively, assume a pipe (ring), with a cut in its ring structure at 12 o'clock. Apply a horizontal curve and belt tension along the belt's curved axis. The inside and outside cut or free vertical edges will tend to move toward the direction of radial pull which is the curve's center. This will induce rotation of the crossection. Once twisted off the vertical plane, the overlap weight aids in further twisting. THis results in aggravated transverse rotation, roll, twist, or cork-screwing. To counter this effect the idlers are axially twisted, using friction, to counter transverse rotation. Idler contact friction and force with the belt is applied along the idler fleet angle with the belt's axis. THis is integrated with the applied belt and product forces (masses). Change the crossectional mass or belt tension and you can change the degree of the pipe's transverse rotation.

2. POWER IS DEPENDENT MORE ON PRESSURE THAN SPEED?

This is true but with notations. The notion between belt speed, material loading and power stated by Kayem: "a low momentum pipe belt will increase power" is interesting. The statement implies - increasing speed decreases power - is counter-intuitive. Certainly, belt tension and roll pressure will increase wth lower speeds. But, is this enough to offset KW = P*V, where the difference between pull (P) and velocity (V) favors P over V between mass flow and power flow? This is usually not the case when including all the parasitic and efficiency losses.

PRODUCT DEGRADATION

THe internal agitation of product in a pipe belt can be greater than with an open belt due to its greater consolidation force variances when conveyed from pipe shape trough roll to mid-span dialation and back to trough shape. In my estimation, the pipe acts like a compression grinder from idler frame to frame. Conventionall belts have a greater freedom with, less crossectional constriction or comminution pressures. I can agree that the belt sag between pipe idlers is less, but this is with closer idler spacing. THe best test is to measure it and then publish before making claims. CDI has tested the comminution on a 9 km overland with a highly friable coal. THe degree of breakage along the 9km transport length is significantly less than going through one transfer station. ■

Addendum to Rotation:

I failed to note: rotation comes from the overlap of the cut region, at 12 o'clock, where a greater horizontal (tangential) force is applied to the pipe (ring) top structure verses its bottom 6 o'clock region. ■

Dear Mr Nordell

Thankyou very much for your for your valuable reply.

you are correct as conveyor is having unsymatrical weight weight at the top chances of cork screw while it is running empty are maximum

FOR STRAIGHT PORTION If conveyor is alignrd in empty condition it may not twist / cork screw while it is partially or fulley loaded.

It may not be true for curved portion as explained by you

A R SINGH ■

Dear Mr Banerjee,

With the product mix and load mix that you have, you may be better served with a MultiFold (Imperial Technologies) or Snake Belt (Dos Santos International) system.

Both of these systems can handle your incline needs easily and are capable of handling smaller loads without roll-back issues

Regards, ■

Dear sir

Snake conveyor cannot replace pipe conveyor as same c\cannot negotiate horrizontal curves.

Snake conveyor can be subsitude of high angle flexowall type conveyor not pipe conveyor.

Each type of conveyor is having its own advantage and disadvantagees. These conveyors to be used only when conventional Belt conveyors are not feasible or uneconomical due to layout costraints.

In snake conveyors additional power is required to run the second Belt.

we have not used these snake conveyors in india , and not aware of its advantages and disadvantages particularly with respect to following

1.0 maximum lump size which can be conveyed

2.0 whether it is feasible to convey poweder like cement

3.0 Power consumption

4.0 Belt life

5.0 Degradation of material

A R SINGH ■

Dear Mr. A.R. Singh:

I am aware that Pipe Conveyors are the prefered choice for horizontal curves. However, your post is the first mention in this string of such a curve requirement - as you did not start the string, are you sure that a corizontal curve is involved?

As far as your questions are concerned, the following applies for both the Multi-Fold Belt and Belt-on-Belt Conveyors (Snake, HAC, and Loop):

(1) Maximum Lump Size - depends on belt width, and idler arrangement - check with the manufacturer (The worst that I've seen is concrete reclaim conveyed on these, including pieces of re-bar).

(2) Although I've seen powdery materials conveyed with both system types including cement, they are generally used for coal, iron ore, salt, gypsum, muck, et cetera.

(3) Power Consumption - you need to check with the manufacturers on this. Generallly, there is an increase in power requirements because there is an upper belt, or an upper folded belt in the case of the Multi-Fold System, that is used to hold the material in place. However, this is similar to the Pipe Conveyor's extra power requirement for folding the pipe belt and for overcoming the extra resistance of the tube forming idlers.

(4) Belt life depends on design and maintenance to a large degree. I am aware of systems that require a belt change every five years and I know of two systems where the belts have lasted over thirty years.

(5) Degradation of material can occur - especially with soft materiuals, such as coal. Again, much depends on the design and operating conditions.

All of your points are relevant, and I suggested these alternatives based on the initial question, which stressed the need for a higher angle of conveyance and to carry various materials at relatively low production rates. If horizontal curves are involved, I would not suggest using either system.

Regards, ■

Dear sir

I donot feel angle of inclination is too high that snke conveyor is required.

A R SINGH ■

Dear Mr. A.R. Singh:

I agree that the incline angle does not require a Snake Belt. However, a Snake Belt or a Multi-Fold Belt could be used instead of a Pipe Conveyor, unless horizontal curves are involved.

Presumably, a Pipe Conveyor has been considered over troughed belt systems for its material containment properties. Both of the other systems suggested also act to contain spillage and airborne fines.

Regards, ■

Dear KHALID:

I do not sell Sandwich Belt Systems - I only perform troubleshooting services. As such I cannot answer your question on patents. However, I believe that the original patents on this type of system were held by Hewitt-Robins for their Loop Belt System. After that, Continental Conveyor introduced their High Angle Conveyor (HAC) system, and Dos Santos International introduced their Snake Conveyor System. Of these three suppliers, the Loop Belt System is the heavyweight, with specially designed belts, extremely heavy structure, and belt widths up to 120 inches wide (steel cord or seven-ply fabric carcass belts).

As far as representation is concerned, you would have to contact the manufacturers.

Contact information for Sandwich Belt Systems is as follows:

Sandwich Belt : www.dossantosintl.com

HAC System:

www.continentalconveyor.com

Loop Belt System:

No longer produced by Hewitt-Robins but available through parent company of Flexo-Wall Belt system. (with the recent purchases, I've lost track of the them)

Note: you should also investigate the Multi-Fold belt system produced by Imperial Technologies (www.imperial-technologies.com) The Multi-Fold system they show on their web site on a Mountain Face is actually a decline conveyor system carrying Gypsum, located outside of Las Vegas, Nevada, USA with a multiple (3) take-up system that is interesting.

All three of these web sites are worth a visit.

As with Pipe Belts, Corriugated Sidewall Belts, Square Belts, et cetera these belt systems are a specialty product requiring detailed engineering to work properly. As such, you can save yourself and your customers a lot of grief by working with the developers instead of trying to copy them.

Regards, ■

DEAR KHALID

INSTEAD OF ASKING THIS QUESTION IN FORUM WHY DONT YOU ASK DIRECTLY ABOUT PATENT RIGHTS FROM DOS SANTOS .

A R SINGH ■

Mr A.Banerjee

Mr A.Banerjee i could not understand what doyou mean by "All CAPS in mail lingo for yelling & screaming at your voice"

A R SINGH. ■

I have read the discussion (on the subject) to this point and wish to (belatedly) reply.

Background:

Sandwich belt conveyors (conveyor with cover belt) were first introduced in the German lignite mines, in the late 1940's and much activity followed including various patent filings, prototypes, etc, thru the mid 1950's. For many reasons, including available technology, these efforts did not prove successful and died out before 1960. Some good came out of this including a very crude mathematical model of the sandwich belt (including hugging pressure calculations) and a skillfully written survey article that separated the good ideas from the bad ones (thus implied the direction for success).

The first (lasting) success in sandwich belt high angle conveying came in the Loop Belt, in the 1970's. This system demonstrated fully the sandwich belt principles including the handling of widely varying materials at very high volumetric rates, at high belt speeds, often exceeding 5 m/s (1000 FPM), with very wide belts to 3 meters (120 inches) wide. Loop belts were designed for self-unloading ship applications. Poor execution of details, exceptions to good (already well established) conveyor design rules (exceptions of convenience) and lack of imagination regarding broad application, stalled the technical progress of this otherwise stellar development. This was a resounding success however with many impressive installations.

It is against this backdrop that I became deeply involved in the sandwich belt high angle conveyor development, at the end of the 1970's. Recognizing the merits of the sandwich belt principle I also recognized the industry's poor understanding of the technology. So, more importantly then any particular invention I sought to rationalize the sandwich belt high-angle conveyor technology in the (already well established and proven) conventional conveyor technology. This was done successfully and published by the writer, most notably in the 1982 landmark article entitled “Evolution of Sandwich Belt High Angle Conveyors”, by Dos Santos and Frizzell. Disclosure of the “Snake Sandwich High Angle Conveyor” as well as the “Mechanically Pressed (with fully equalized spring loaded pressing rolls) High Angle Conveyor” is included in this 1982 writing. The former, now known as the “DSI Snake”, was selected as the preferred system in a USA Bureau of mines study report and the latter now known as the HAC was invented and marketed by the writer at Continental Conveyor USA, from 1982 until 1997.

Response to Specific Comments:

1.Continuous Hugging regardless of load: Dos Santos sandwich belt conveyors are intended for high angle application. These continuously hug the material conveyed regardless of the load level (degree of cross-sectional filling). There is no cross-section when there is no material load and the belts are in full face contact with each other. This differs from pipe belts that have a defined cross-section regardless of the degree of filling. Pipe belts cannot operate at high angles without the material sliding back and plugging the cross-section.

2.Power requirements: The Dos Santos high angle conveyors use two endless belts that share a common carrying path. It is not correct to label one or the other as a “second belt” as both are typically driven and both share the material load. Higher travel resistance per unit of length (as expected for the two belts on closely spaced idlers) does not typically produce higher travel resistance per unit of lift (as the high angle path is shorter). Early testing and monitoring revealed that power requirement is actually slightly less then conventional at units of significant lift, elevating heavy materials at high tonnage rates. We do concede slightly higher connected power at smaller units but this is typically due to increased terminal resistances (due to twice the scrapers and pulleys) not belt line resistances. In any case our power requirements are always less then the power requirements at pipe belts.

3.Maximum Lump Size: Large belts can handle large lumps small belts cannot. The Dos Santos lump criteria (proven successful in many installations) makes DSI sandwich belts compatible with the conventional belts at the same installation. We must remember that the sandwich conveyor for the same conveying capacity is wider than the conventional conveyor.

4.Belt life: Dos Santos Sandwich belts have the same operating and maintenance characteristics as conventional conveyors, including belt life. This is no accident and is at the very heart of the Dos Santos development as described in the background.

5.No Material Degradation with DSI Systems: No material degradation occurs at Dos Santos Sandwich belts. Material quality preservation is a sandwich belt attribute that we promote against other elevating systems. The material is hugged gently and continuously and does not move within the sandwich, from loading to discharge. It is this attribute that makes Dos Santos sandwich belts so popular for handling screened wood chips (which cannot tolerate any breakage after screening). Independent customer testing and installations have repeatedly demonstrated no material degradation (due to conveying in the sandwich) even with the most damage prone materials such as wood chips and various grains.

6.Material Degradation with other systems: Material degradation with other systems, most notably the “Loop Belt” is due to poor execution not principle. Loop belt sandwich entrances are typically abrupt with incidental crushing loads at the first inverted idler. This not only degrades the material but imparts a hard toll on the equipment and belt. Indeed, the incidental loads are so high that special live shaft pulley rolls are used in this area.

7.Current Sandwich Belts Systems: Three prominent system are mentioned, The Loop Belt, The DSI Snake and The HAC. I am inventor of the latter two systems (the Snake and the HAC).

a.The Loop Belt was invented at Stephens Adamson in the 1970’s. I am not aware of any Hewitt-Robins connection [Hewitt-Robins did make a (one-of a kind) Ferris-wheel type belt system for a self-unloading ship application. A steel wheel with material compartments was covered by an outer belt which served to cover and contain the material within the compartments. This system was never repeated.] The Loop Belt system broke new ground but stalled technologically very early. Today Loop Belts have no champion and new installations are repeated, same as, by former employees or company clones of the long defunct Stephens-Adamason Company. Because of the minimal duty at self-unloading ships their short comings (poor execution) are not dramatized (but are recognized).

8.Steel Cord Belts: In general steel cord belts cannot be used at any sandwich belts pursuant to their rationalization in the conventional conveyor technology. This is due to radius of curvature constraints at the inverted convex curves.

9.Propriety: The last writer appears obsessed with the proprietary status of the sandwich belt systems. History has demonstrated, in the case of sandwich belts, that each invention (for which a patent can be awarded) is far less important than the broader technology and its rationalization. Most of the past inventions did not survive. Indeed the remaining systems, which have demonstrated resounding success and hold the greatest promise into the future, are pursuant to the Dos Santos rationalization of sandwich belt high angle conveyors in the conventional conveyor technology.

I welcome your comments.

Joseph A. Dos Santos, PE ■

Mr. Dos Santos,

You are correct on the Loop System, I was going by memory on the ancient history of that system and had mis-identified H-R as the originator instead of S-A. My apologies.

As far as the Wheel System is concerned, there are two applications that I am aware of (both for ship unloading on the Great Lakes) - one on the Presque Isle, where the wheel is transverse to the hold and boom belts, and one on the Cort, where the wheel is in-line with the other belts. The maintenance problems associated with this system include relatively rapid bogie wheel wear and rapid wear of the inner wheel belt, although the inner belt on the Cort has lasted well since it was converted to a steel cord from a multiple ply fabric carcass belt. As far as the developers are concerned, my understanding is that the Wheel System was developed by Litton Industries, not Hewitt-Robbins (although I believe that H-R did help).

Regards,



Regards, ■

Dave,

LItton Industries, I believe, purchase HR in the late 1960's. I do not believe they where involved in material handling before the HR purchase. I went to work for them in 1974, some time after the purchase.

PWH, I believe, patented a high angle conveyor concept for their coal mine stacker systems as Joe has mentioned. They used a second cover belt without the hold down rolls. This was applied the the late 1940's. They could not get the high angle without spillage while transporting large lumps. THis is what I was told by PWH in Badoyenhausen, Germany just after PWH purchased HR from Litton.

Later Stephens-Adamson invented a cover belt that used lead weights integrated in the belt carcas to apply sufficient weight to hold the rock in place on the steep slope > 20 degrees. This was used in ship loaders or maybe unloaders. ■

Mr. Miller,

Thanks for the clarification on the H-R self unloader wheels.

Larry,

The "Retainer Belt" (cover belt weighted with lead blocks, then with lead shot) was indeed used at self-unloading ships but only for a short time span. It was abandoned in favor of the Loop Belt after the Loop Belt was developed. Stephens-Adamson did build and maintain a demonstration system, at their Bellevile Ontario Plant, into the early 1980's, that included a Retainer Belt, a Loop Belt and a Beltavator. This demo sysetm was government funded.

As an aside, S-A also used government funds to build a high speed conventional conveyor (2000 FPM plus) test and demo system, in Belleville, during the 70's.

Joe Dos Santos, PE ■

How much history will be lost if we don't have these discusions.

One tid-bit of history: when I visited ??-Wellman in mid 1970, I believe, in Cleveland, before Dravo purchased them. I was introduced to Mr. Wellman, an prolific inventor, who sat in a hugh office, by himself. He was interested in the concept of dynamic analysis I presented.

He showed me a 16mm film clip of his high speed shiftable-on-the-fly belt, operating on the Oroville 1950's or Shasta 1940's dam. It was probably Shasta. The film depicted tractors moving the rail by picking it up and simutaneously moving it about a meter where you could see dam ballast transported at about 1300 fpm. The German's copied his concept for the Brown Coal fields after seeing it in action. They never applied the operational move.

Since you also have a repositoryof history, you could share the same. I do recall we met in the Dravo office during your development of the HAC, which Dravo chose not to pursue. ■

Thank you for a roundabout way to revive a very fascinating thread. I'm still reading it again and will repeat.

Applications for metal detection along steel chord belts have been discussed at great length on other threads and you can refer to these.

The previous post to that one was duplicated in today's thread and replies are in progress. ■

Hello,

This thread is about 14 years old. I am attending it just for general information. Presently this may not have relevance to your problem.

You have chosen pipe conveyor which can carry iron ore at the rate of upto 500 mtph. Your query is whether the pipe conveyor will have any problem if you use it for 150 mtph. As a rule, pipe conveyor cannot have problem even when running at empty condition, because continuous feeding round the clock is not possible most of the times and some times there may be no material to feed. So conveyor or pipe conveyor cannot not have problem when running at empty or partial or full load condition.

Only in some types of rotary crushers, frequent empty running is not advisable because it will make noise and reduce the life of crusher.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis is ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 2012.

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

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Really lower volumes are not a problem in a pipe conveyor, with materials that easily roll it is better than in conventional trough belt.

For example for materials such as granular spherical or powder type which on steeper inclines would roll back on the belt, in a pipe conveyor they would roll back less due to more contact and in anycase be contained until following material came to take it.

The only problem with low fills like empty belts you can get a somewhat different tracking position.

Paul Holt ■

Indeed the material has no where to go but backwards as it is contained from going out. Discharge would be in the form of slugs that plugged or nearly plugged the pipe cross-section depending on how bad the profile angle violation. This behavior will result in bad wear and tear and, depending how long the plug, could result in stalling the belt drive due to material weight overload and especially increased belt line travel resistance as the swelled material cross-section is squeezed through the lesser aperture of the pipe section at each hex idler. ■

In my experience yes you can get a little extra wear if you have material consistently sliding on the belt but it is small.

Regarding overload with plugs it is not usual, because the pipe is semi rigid slide back does not cause plug to expand the belt diameter beyond the the pipe hexagon idlers.

The place where this can occur is if overloading the belt at the tailend where control caution in needed. ■

Paul,

As I said, the severity of the wear and tear and belt line resistance will depend on the severity of the profile angle violation. We have long known and it was demonstrated by A. Vierling in the 1950's, 1960's that increasing the troughing angle results in wedging that allows us to increase the conveying angle to a value approaching the angle of repose of the conveyed material. This is accompanied by increased belt line resistance to travel, thus increased power required. This effect was especially accentuated when the wedging was done with 2-roll V type troughing idlers. With incline angles that result in material slide back or roll back but don't exceed the material's angle of repose the pipe plugging/filling may stop due to wedging before complete plugging occurs so a free surface of the material remains and the pipe is not completely plugged. At conveying angles that exceed the material's angle of repose complete plugging and possible swelling will occur just as in the case of 100% filling at loading. ■