Dear S.M.SUBRA

You wants to install drive at tail end to save cable length. You may do so but before doing pl check your belt tension will increase you may have to go next size of belting.

Due to incresed tension your idler life will reduce or you may have to go next higher size of idlers. Your pulley shaft and bearing sizes may change.

you have to design complete system and then compare costs. In my openion providing drive at tail instead of head is not economical.

A R SINGH ■

Dear Mr. Subra,

Maximum tension in belt and thereby the belt size differs depending upon the number of drives and their location. You can have a head end single drive or two number of drive at head end or tail end single drive or two number of drive at tail end or one head end drive and one tail end drive. Drive quantity and their location is selected such that cost of mechanical, electrical, structural and civil work altogether become least. Which arrangement will result into economical solution depends upon conveyor profile i.e. positive lift or negative lift, length of horizontal portion, and so on.

It is an elaborate design exercise to derive optimum arrangement economically and technically.

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 ■

You will not have a slack top side. Picture this, you are extending the tension from the head pulley all the way along the return side until you reach the drive, The tension on the top side is a function of the loading of the material.

What the previous respondents are saying is that your system needs to be designed to handle this expansion of the tensions. Your system needs to be completely engineered for a return side drive. The location of the take-up will also need to be analysed.

Gary Blenkhorn ■

Drives at the tail have been done before. One serious point you should consider: the complete return strand is wound up as a high energy spring that will collapse in an abnormal way where there is no mass dampening along the return belt strand.

Take Anamax mine in Arizona, designed by Stephens Adamson in the late 1960;s (from memory). Hewitt Robins warned that the 8000 ft overland would suffer a catastrphic failure. No heed was taken. THe gravity take-up was launched out of its structure and destroyed the drive station.

I believe I wrote on the subject in the 1984 publication in Bulk Solids Handling as a case study. This conveyor defined the need to have a 2-dimensional wave equation. Otherwise, the belt tension collapsed to below zero, which is not possible.

Get help when in doubt. ■

Yes you should be concerned about the return rollers subjected to the high belt tension and have no material dampening.

Further, the range of belt tensions will be extreme between cold weather and full load verses hot weather and no load. The return strand belt will likely hit a major vibration mode, between the ranges of belt tension, and result in high belt flap which will reduce idler bearing life. ■