Dear Mr. Yung,

The earlier respondents have already given the information in detail. However, I would like to add following for general clarity :

Firstly, there is issue of the maximum cross section that can be achieved on a particular belt. This will depend upon material surcharge angle, troughing idler shape, inclination, etc. In this calculation, the usable minimum edge clearance at the belt is considered, as recommended by the standard / practice you are using. In this calculation the cross-section shape will also be as per the practice / standard you are following for your calculation.

Now, the conveyor design fundamental parameters are capacity (actual conveying rate design), belt width and belt speed. You will rarely be able to use the belt speed, which will create the optimum maximum cross section as per earlier paragraph. Generally speed will be somewhat higher as per the available pulley size and gear box ratio, Therefore, accordingly you will be creating a cross section which is somewhat less than the maximum as mentioned in first para. So, in this situation, using the shape of the cross section one has to make backward calculation for the corresponding edge clearance. This means this edge clearance will be somewhat more than the usable minimum.

So, the dimensioned cross section as depicted by standards / practice, do not conflict with the cross section area corresponding to capacity and belt speed.

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.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Dear Mr. Yung,

Please be advised regarding the selection of the belt width, speed and edge clearance to contain material spillage.

Mr. Mulani indicates to rely on standards and did not adequately discuss the importance of the edge clearance selection. The edge clearance controls spillage. If you do not adequately design for belt width, belt speed and chute loading procedures you will not obtain the no-spillage result you seek.

Standards are a starting point. They are typically quite old and behind modern engineering as noted below.

Design standards do not treat the need for edge clearance and its relevance to chute loading dynamics (forming the proper surcharge angle and lump pile). I therefore suggest you read modern methods of selecting the belt width, speed and edge clearance. Note, if the load stream is delivered in the center of chute crossection, it will tend to flush the load to the skirts and away from the center. If so, what will be the surcharge angle you design too? Good chute design takes this into account. The standards do not.

DIN and other standards specify edge clearance based on ancient 1960's data. The typical form is 5.5% of belt width plus 20mm. This only accounts for some guess at belt loading due to some mistracking, belt and installation construction errors that cause belt to wander in the loading station and from so-so field splice tracking influence. They say nothing about material lump containment.

Today, the edge clearance is selected closer to 75mm plus lump containment regardless of belt width. Lump containment, as a rule of thumb, is about half the largest rock diameter. This assumes the best method of chute loading.

Horizontal curves create another design dimension.

Belt speed is selected from optimizing power, wear life, belt strength, and vibration control. Faster means narrow with less belt rubber and steel, and higher belt power, strength, wear, and more vibration modes. Faster also means greater idler spacing to take advantage of the lower crossectional loading.

None of these points are discussed in the industrial standards. ■

Mr. Yung’s question is of basic nature. So my reply is also of basic nature.

As for reader’s general information; good standard / practice accounts for varied influence on cross section by the term ‘filling ratio’ or ‘filling factor’. Its value depends upon evenness in feeding, lump-size / percentage / oblongness, magnitude of aligned / mis-aligned running, vibration-frequency / magnitude / duration (i.e. speed, idler pitch, sag and conveying length).

Many of the important conveying systems receive feed from reclaimer machines which often have cyclic feeding, where cross section on belt is also fluctuating in cyclic pattern. The analysis of variation in cross section, usable cross section and its implication on conveyor is a routine matter, without which there may be all-round chaos in material handling systems.

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.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

The formule for A1th fior BW<2000 mm

A1th =(((0,9B-50)-LM)/2*cos)*2+LM

I SUGGEST THIS IS WHAT YOU WANTED

THE MAXIMUM HORIZONTAL WIDTH OF THE PRODUCT ON THE BELT

KIND REGARDS

JOHAN BRANDS

THE NETHERLANDS

e-MAIL: i.s.t@wanadoo.nl ■

Any standard publications (CEMA "Belt Conveyors for Bulk Materials", MHEA "Recommended Practice for Troughed Belt Conveyors", etc) will all give information on calculating the material cross section on the belt.

In practice the accuracy of your calculation will depend on how closely the characteristics of material handled agree with the values you used in the calculation. ■

Following steps can do it:

1. know capacity in t/h = tons per hour; t = tons; h = hour

2. know bulk density of product = rho = t/cm where cm is cubic meter

3. calculate flow rate volume = capacity / density in cm/s

volume rate = ((t/h) (h/s = 1/3600) = t/s) (1/rho = cm/t) = cm/s

s= seconds

4. select best belt velocity for product = v= m/s where m= meters

5. calculate crossectional area = volume rate / speed =

Area = (cm/s) / (1/v = 1/(m/s)) = square meters

6. select belt width and idler trough angle to contain Area with sufficient edge distance to control spillage of large lumps. Must know surcharge angle as you see in DIN calc.

7. Check if belt width is satisfactory for belt strength and troughing with selected trough angle

As has been noted there are many publish docs on more detail. ■