Ravi

Have you considered low friction linings for the chute, or changing the chute configuration to improve material flow?

It is useful to have the urea tested with various linings by an organisation such as TUNRA to confirm friction angles with various lining materials.

Regards ■

The configuration of the chute, which is presumably stainless steel, will have an important bearing on how best to approach this problem. It would be a good start to see how damp urea sticks to UHMDP compared with stainless. Just leave a pile on a sample of the two surfaces overnight, and compare the release conditions when they have dried out, to assess if it is worth lining with this material.

Another approach on flat surfaces is to hang sheets of rubber belting that can be occasionally agitated with a small air cylinder to shake off any material that is stuck. For vertical chutes it may be sufficient to just pack the top fixing edge slightly away from the wall so that the sheet is flexible enough to prevent to formation of a stable bed of residue.

Radiused corners are also good practice for dealing with sticky materials because square corners provide a large surface area in relation to the weight of any material builing up in a corner and the two faces offer good support for materials that tend to stick.

Another point is to try and focuss the flow stream to miss side walls and, if they have to impact on a contact face, make the initial surface at an oblique angle and curve the surface to change the flow direction, even if this means adding a profiled plate inside the chute. Separate, small and steeply inclined, side deflector plates could possibly be fitted, to direct the material away from the side walls or corners.

Depending on the ambient conditions it may be worth insulating the chute to reduce condenation effects. These are particularly prone to occur with material arriving in a warm condition when the ambient temperature is below its dew point.

Failing a cure by one of these methods, send a drawing of the chute to me at lyn@ajax.co.uk, and I will review what other options may be available. ■

Dear Shri Ravi,

You already have the answers suggesting very useful and appropriate solutions. Possibly, UHMW polymer liner will improve the flow. Other means is to use chute vibrator of appropriate capacity (i.e. neither very strong nor very weak).

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyor.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■