It appears that you might be considering a short reversible conveyor. In such cases you have to accommodate the continuation of feed while the receiving machine retards to a stanstill and then accelerates in the opposite direction. This should not involve much accummulation during the time taken for your shorties to complete a reversal.

Skirts should be quite adequate and the power issues are not important. (Do you want to shift the stuff or not?)

Why should ISO show you how to calculate the cross section of a fully (????) skirted belt. Its not rocket science...no way. ■

Sometimes a wider belt doesn't cost much more because most of the money is in the frame, drive & terminals. The incremental cost to go 6" or 12" wider is surprisingly small at widths from 12 to 36". Sometimes it is an experience decision, not just a calculation decision ■

Originally Posted by ambhad

[B]It is also noted that in ISO no such method is given to calculate crosssectional area of fully skirted belt.

You can still do this with standard geometry. You know what the total area is, and you know what the surcharge angle of the material is. With the width between skirts, you can work out what the top area is and you know what the area of the bottom is.

Again, depending on the method of feeding the belt (flood loading or feeding into the centre of the belt), you could even consider it as a flat top making it easier.

This is the method I use to calculate the height against the skirts to calculate loading skirt friction. ■

Originally Posted by ambhad

Belt width fixing criteria for small conveyors used to feed other conveyors

........ Quite often such conveyors or belt feeders are made wider with less speed. We are little confused as to whether such short belts need to be wider than normal with less belt speed or not. ........

Dear Mr.Ambhad,

If the width is small, belt speed will be higher to carry the same amount of capacity. The time taken for each cycle will be very less. This may damage the smaller belt very fast since wear & tear will be very high.

Regards, ■

Dear Mr. Ambhad,

The belt conveyor implies that it is just conveying the material as being put on it at feed point. If the material is more than limit, there will be spillage. If there is no material, then it will run empty.

The belt feeder, is for regulated discharge by it. The belt feeder will be directly below hopper and it will draw out the material as per its setting. This draw out rate (mtph), will be practically constant whether the hopper is fully filled or partially filled. The material discharge by belt feeder will abruptly become zero when the hopper becomes empty.

For material flow, in a series of conveyors, one can have a differing belt width with appropriate belt speed to suit common conveying rate. For example, a 20 meter conveyor is coming out of crusher and it being of small length, say it is running at 1.5 mps with corresponding wider belt. Now, this conveyor is say feeding on to 3 km long conveyor where the speed could be around 4 mps, with corresponding lesser belt width (for economical installation). So, differing belt width and speed are not uncommon. The principle is that the flow rate is constant and

Flow rate = (flow cross section area) x (flow velocity).

For a very small conveyor, engineers often provide skirt board length from feed point to the head pulley to increase its ability for material cross section on belt and to use reduced speed for better life. Buyers sometimes give name belt feeders to such conveyors but functionally they are only conveyor.

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.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: parimul@pn2.vsnl.net.in ■

We don't normally use conveyors with narrow belts.

At less than 750mm they don't want to sit in the trough (unless the idlers are miles apart) and makes for difficult tracking.

This is a big consideration for reversible belts.

It is also a huge consideration for belts with concave vertical curves

Cheers

LSL Tekpro ■

Originally Posted by Graham Spriggs

We don't normally use conveyors with narrow belts.

At less than 750mm they don't want to sit in the trough (unless the idlers are miles apart) and makes for difficult tracking.

This is a big consideration for reversible belts.

It is also a huge consideration for belts with concave vertical curves

Cheers

LSL Tekpro

We had a guy who once said "you don't make belt conveyors less than 24" wide" so he didn't in his quotation.

Unfortunately, somebody else did and they got the order.

It's all about the individual application, so take care with generalised rules. ■

As far as belt width there is no limit. If you go into packaging conveyors and the like belt widths can be as little as 50mm e.g. mail sorting conveyors. When you get into narrow widths the style of belting changes gievn troughability and other issues and you need to start talking to the likes of Habasit who specialise in this type of belting. We move to conventional belting when abrasion and impact dictate but there is a cross over.

Cheers

Colin Benjamin

Gulf Conveyor Systems P/L

www.conveyorsystemstechnology.com ■

It is important to know the difference between a belt feeder and a transfer conveyor. The former regulates the volumetric rate by shearing the bulk material across the throat from a head above and through a regulating gate opening. A transfer belt conveyor receives a clean transfer of the material from another belt or other transfer device and carries the material that it receives without regulating it. The belt tension and power calculations must reflect this typically requiring much higher values at the feeders. Belt speed must be slow at the feeders to control wear and tear. Not so at the transfer conveyors. Thus for the same design rate the belt speed may be higher and belt width may be narrower at the transfer conveyors. Once the design rules are clear then the choice of belt width may be influenced by various factors. There may be reasons to use a common belt width at all conveyors, say for standardization.

Joe Dos Santos ■