Metal finishing Q&As since 1989

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Coating a SS weigh hopper to overcome material sticking problem

2003

I work for a chemical process plant which produces alumina of various grades for various industrial application . To bag our product which is in a powder form we have bagging machines installed in the system. One of our product grade is a very fine material. This product when bagged by the automatic bagging machines is giving us inaccuracies in weighing. We have found the reason. The weigh hopper which weighs the material before dumping onto the HDPE bags is of SS316 material.This powder is sticking on to the weigh hopper causing the inaccuracies. Can we use Teflon lining on the SS316 material to avoid the sticking problem or can any other coating material be used. Pl inform. The product specs are : Bulk density - 0.65 gm /cc (loose )and 0.98 gm/cc (packed), Particle size distribution (d50)-3.5 - 4.5

Gopal Srinivas
- Belgaum , Karnataka , India

UHMW (ultra high molecular weight polyethylene) can be applied with a wide tape. This has properties quite similar to teflon, is cheaper, can be applied or removed on site and has excellent wear properties. No, I do not know where you would get it in your country.

James Watts
- Navarre, Florida
2003

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2003

Hi Gopal,

Please consider the 'angle' ! It doesn't matter what material you use, if the powder can't fall off, then it will stay 'aboard' and cause weighing inaccuracies.

Yes, you could use a thin teflon, preferably a PTFE type, but with a treated 'back' that will allow itself to be bonded/glued to the s.s. weighing table.

If, on the other hand, you have a problem with a chute and the Poly bags sticking to it, then go for a minimum l5% slope angle. Then you could use ordinary h.d. Pe. or a dissimilar polyolefin such as PP.

Back in the mid sixties, Canada was the first Country in the world to use Polyethylene for mining launders (Alcore Fabricating in Richmond Hill, Ontario) ... to replace mild steel, but this was for wet slurries.

As James Watt pointed out, uhmw Pe is very good on abrasion, better than teflon ... but there is one grade (SIMONA product) that has a molecular weight of l million and is WELDABLE whereas all other uhmw Pe is not weldable.

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

You can use PTFE COATED POLYMIX SHEET. It can be pasted with any suitable adhesive. It has excellent non stick property on one side and the other side can be pasted.

Bipin Bansal Singh
- NOIDA, U.P., India
2006