'Drag chain' could refer to a reclaimer; scraper chain conveyor; apron feeder etc. Each has its own particular drag force. Selected chain speed determines rpm and motor power is chain speed x drag but usually factored according to the drive duty. Maybe it doesn't help much: but neither does the question. ■

Hello,

As said by earlier respondent, the question is incomplete, and also calculation of tractive pull and power is a big subject, and its practical design procedure cannot be explained in the forum. Refer literature / manufacturer's leaflet etc. for basic information.

You are referring to drag chain conveyor i.e. where material is conveyed by dragging. In this there are two categories: 1) Chain is sliding and material is sliding (dragged). 2) Chain is rolling and material is sliding (dragged).

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

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: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

OK then: let's get you going in some sort of direction.

Bulk solids pressure is no different to liquids. It is independent of direction and dependent on depth. Ignore the dymanic pressure build up from blocked chutes, hopper transitions and the like. The main characteristic is the internal friction within the burden and it isn't important. All you need to realise is that if the internal frction exceeds the metal to burden friction you are in business. If the metal moves then the material has to. (If the internal friction is lesser then you are ploughing chain flights around for nought.) That is your maximum effort condition and there are only geometric variances to consider viz. bed width and sidewall height. You obtain the rolling resistance of the chaintrack according to the manufacturer's catalogue and it should then be recognised as negligible if you can justify the consideration of a chain in the first place. So you claculate the wall pressures and floor pressure per unit length; multiply the pressures by length and the coeffiecent of sliding friction between the burden and steel (liner) plate and that is your drag. Subsequent chain speed and power is your own affair depending on how long you want the thing to last for and how much throughput you need.

If you are talking about a chain hauled reclaimer type gadget, specifically the portal variety, there is only the bed width to condsider and the steel to burden coefficient of friction is replaced by the material friction. With experience it is possible to calculate the power consumption of a reclaimer within 4% in a few minutes if you know the pile width and the lump size. I've done it many times and 4% accuracy proved better than most longer routes.

It is really quite simple, isn't it? Do not try to delve into complex theories which contradict each other for the main part and only confuse the concientious. Available motor sizes should limit the sophistication of your calculation and throw criticism awry.

I could, so I will, state that cutting force is independent of direction and only mildly affected by burden depth. Detail engineering will determine what the flight area needs to be so that the internal friction takes over and Panzer conveyors usually have a residual bed to keep the chain flights away from the pans.

That's about it for me, but if I think of anything more I'll be Bach. ■