Dear Shri Banerjee,

You have asked about the suggestion for possible size of pipe conveyor for lime, iron ore, dolomite & coke. These materials could have varied values of abrasiveness for example there is coke, which is very abrasive, and there is other coke, which is not so abrasive. Similarly, iron ore can be of medium abrasiveness to very severe abrasiveness. So, you will get better response if you mention the characteristics of your materials including lump size etc.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Your pipe diameter is very large for the tonnage. Your speed is very slow, do you have a rational for such a slow speed and large pipe diameter? This large diameter also compromises the curving of the belt. It does not appear to be an economical solution.

A key parameter in selecting the pipe diameter is the lump sizes to be conveyed for each product and tonnnage. The lump size can restrict the product capacity of the cross-section.

For example, if the rock size is 150 mm, with 350 t/h of limstone, and belt speed is 1.5 m/s, then the 350mm diameter is border line due to the large lump. This also take a 1220mm belt width. The resulting belt cross-sectional loading is about 50%.

The crushed bulk density needs to be noted for each product.

Abrasion should not be an issue. The loading chute will control the abrasion damage.

The general geometry needs to be reviewed to give weight to any opinion.

Lawrence Nordell ■

Dear Banerjee,

I will post the geometry illustrations of the pipe cross-section tomorrow if you provide the bulk densities at the loading point. I understand your speed limit for the lime, which happens to be the highest tonnage product and possibly lowest bulk density. Have you thought about a variable speed drive? The lighter tonnages may cause the belt to cork-screw with the lighter cross-sectional loads that have sharp horizontally bends.

From this we ask for your vertical and horizontal geomtries. Better yet the whole conveyor geomtry.

Some convey lime up to 2 m/s with improved feed chutes. Once the gas cavity is contailed there is no dust. The secret is in the proper engineering of the load and discharge transfer stations.

LKN ■

Dear Shri A Banerjee,

Regarding your question about the importance of abrasion in pipe conveyor, the information is as below.

The pipe conveyor has overlapping edges. The pipe cross section between two idlers tries to expand, which may not be even visible so easily. However, when this cross section passes through the idlers section, the pipe profile tends to reduce in diameter. Accordingly, there is continuous rubbing between overlapping edges during travel of the belt, all the time. In view of this continuous rubbing, the belt edges tend to wear out faster. So, in case of very abrasive material, the selected belt speed will be somewhat lower, and it will also need somewhat thicker rubber covers on belt.

The above-mentioned rubbing of the belt edges is also the main reason for higher magnitude of artificial friction coefficient of conveying for pipe conveyors. So, in general, the pipe conveyor would consume more power compared to usual trough conveyor.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Dear Shri A Banerjee,

Here is the promised illustration of your specified pipe

cross-sectional configuration.

Lawrence Nordell

www.conveyor-dynamics.com

[IMG]d:\temp\pipe.jpg[/IMG] ■

A further comment on the cork-screw effect and its origin refer to my previous posting illustration of the cross-section:

Imagine a horizontal curve with its locus to the right of the crossection. Further imagine the belt has a set of distinct tension cords. As these cords try to pull the belt width at their apointed positions, there is an imbalance between the top and bottom section of the pipe due to the overlap/cut. Both belt edges of the cut tend to pull the belt top section clockwise towards the 3 o'clock position to become torsionally neutral.

Once the belt begins the corkscrew, the overlap weight imbalance, between top and bottom of belt, will continue to propogate is rotation until the overlap weight and torsional twist come back into balance.

The corkscrew can continue if the belt overlap has rotated beyond 3 o'clock and the horizontal curvature is reversed.

I disagree with Mr. Mulani's abrasion concern. Its is true there can be some rubbing in the overlap, and it can have an influence on power, however, unless the pipe undergoes some serious rotation, I do not see how an abrasive material can migrate to the overlap unless you are having this event on the return strand. Furthermore, larger pipe diameters have a problem with the overlap not being able to support themselves after use. They tend to collapse and pull away from the top idler restraint.

I am intersted in further dialog on the above.

LKN ■

Dear Banerjee,

I agree with Mr. Mulani on the power consumption of the pipe conveyor verses a conventional. Puting aside the benefits of dust control, spillage control and routing geometry, a pipe conveyor will consume more power for the following reasons:

1. about 20% more belt width and mass

2. 9-12 rolls per idler station vs 3-6 increasing seal and brg drag

3. about 30% closer spacing to maintain the pipe configuration

4. force at the belt-idler contact interface to maintain pipe shape

5. stiffer belt due to fabric reiforcement increasing spring effect

6. internal and external rubbing and creasing noted by Mr. Mulani

The difference is not small. Of course some will argue that the difference is small in the attempt to gain a foot hold on a project. They are not truthful to their profession. You must do further investigating to find the truth for yourself.

Pipe conveyors have advantages. Power parity is not one of them. I design both and only have a preference in giving our clients the best engineered product and value for their faith in our service. We have provided services for JPC as well.

Lawrence Nordell

www.conveyor-dynamics.com ■

Dear Shri Banerjee,

The hard core technical information is different from technical information given as a part of sales. The pipe conveyor consumes more power, and difference is of noticeable magnitude. However, pipe conveyor is used for certain reasons wherein extra power consumption is justified.

Mr. Nordell has already given detailed reply in this matter and hence, I am not going in further details.

Regarding, Mr. Nordell’s earlier query about the effect of abrasiveness of material on pipe conveyor, I go by the information which I am having i.e. abrasiveness affects the belt speed of pipe conveyor in a manner similar to conventional belt conveyor, and in addition due to rubbing of the edges.

The reason is that belt conveyor or any material handling equipment cannot remain free from material dust settling on various components like idlers, pulleys, belt surfaces etc. I am not sure to what extent Mr. Nordell may agree with this.

There is one pipe conveyor at Dahej in Gujarat, which is handling copper ore. As per the recent dialogue on this forum itself, the user had mentioned that the belt is practically intact (good condition), but its overlapping edges are worn out.

I hope the above information will be of use to you.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Another try at posting the pipe cross-section:



LKN ■

Mr. Banerjee,

No stone boxes and no restrictions.

Fine dry products, where belt conveyor transport is viable, can be loaded and transfered by a special chute configuration that virtually eliminates hydraulic jump, aeration, and other forms of undesirable effects.

The most significant factor is to maintain a constant product velocity from discharge to receiving belt This results in delivery of product onto the receiving belt at the speed of the belt without unacceptable vertical acceleration, product expansion or contraction. In-line and angular transfers do have different high requirements.

Chute geometry and flow surfaces are designed in a special manner to guaranty a constant product velocity. This is done using the Discrete Element Method (DEM) granular flow simulator. See our website for illustrations of generalized granular flow modeling.

Product placed on the belt can be transported at a speed up to the lifting velocity of the smallest particle size transported with respect to the gas turbulance generated at the product-gas interface. Above this critical gas turbulant velocity, unacceptable dust will likely be generated. Any cross wind or couterflow gas velocities must be considered. ■