DEAR RAO

It is not mandatory to form pipe shape on return side also.Pipe shape Return belt is considered due to following reasons

1.0 When you negotiat tight horrizontal curves on carrying side you can not negotiiate on return side without Pipe formation

2.0 Designer genrally wants sam structure width on return side as on carrying side. this can be maintained by keeping return side pipe , Thus conveyor width from bottom to top is same.

3.0 While Return side is in pipe shape there is no spillage of dirt along the conveyor path.

A R SINGH

modtech@modtechprojects.com ■

Dear Mr. Rao,

The earlier respondent has said that it is not necessary to have pipe in return all the time, but would be required in consideration as mentioned / explained.

I would only like to say that, people who have created the pipe conveyor after extensive thought, deliberation, experience, etc., during two-three decades time, it must have been found that keeping the belt in pipe form in return run is beneficial in totality in most of the average situations.

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 ■

Yes it is usually desirable to have return side in a pipe for:- negotiating curves, for keeping dirty side of belt on the inside (no spillage), for keeping the narrow section of conveyor structure for a given belt.

However there are quite a number of installations mainly in Japan where the client and supplier have decided on a (non return pipe conveyor) as this can save some cost.

P Holt

Dosco Overseas Eng Ltd. ■

Dear Mr. Rao,

I have already given a reply but some body has deteted the same.I do not know why! The very reasons are as follows.

1. In using pipe conveyor there is lot of structural savings. In case we do not use pipe shape the main objective is lost.

2. For better tracking.

Regards.

A.Banerjee ■

There are also cases where the return side pipe does leak and spill material with a pipe configuration that transports the return side with the seam down. ■

The thing that most people have missed is your request to have 60 degree idlers on the return. Inverted or otherwise. This is undoubtedly to retain the pipe /tube form. This is out of the question since you will have no control over the belt. It is true that with some belts there is little contact with the top idler rolls but this is not always the case. This all depends upon the drive and take-up configuration, plus the belt rigidity and the conveyor stopping characteristics. Should the tube start to open or roll, you will be in a hopeless position.

If you were thinking of opening the belt into a reverse 60deg configuration, the reverse bending would finish of your splices in no time and create just as many training problems. If you want a conventional return then that is what it must be with wider structure and flat or very low angle vee return idlers. Please remember that the belt will try to run on its edges. This type of configuration is best kept to short straight units with a good belt selection.

What you may wish to consider is having a full idler set at 4 normal pitches with half sets in between but you are only saving a handful of rolls and you must be absolutely sure that your belt selection and calculations are impeccable. ■

I have just realised that you are intending hanging the belt over the inverted idlers. This should not be undertaken for the following reasons.

1. The centre roll will damage the belt. (It would need to be rounded)

2. There would be no opertunity to examine or maintain the idler rolls.

3. The wing rolls would provide little ability to train the belt.

4. Setting alignment would be extemely difficult

5. The cost of the configuration is likely to exceed a standard idler set. ■