Contact Friction
Whilst practical experience in a particular situation is invaluable and may encourage the examination of other applications there is no alternative to testing the slip properties of a different bulk product in a particular conditon with the contact surface in question. Thise can be done by conduction full scale trials or measuring the value with a wall friction tester. Cruce assessments may be made by placing the material on an inclined slope of adjustable steepness until the product slips, but this is only representative for low contact pressures. The cost of the equipment is hardly significant against the design value for optimising the construction.
It is dangerous practice to accept statements such as 'A low friction surface', because the value depends on the interaction with the contact material with the product in question. What may exhibit low friction with one bulk material could present high values with another, or the same in a different condition. Wear in use is also a factor that can cause friction to either increase or reduce, depending on circumstances.
'Measure every time' is the professional way to approach wall friction values. It is a false economy, exposing the design to excess costs and the propects of failure, to accept figures without verification. ■
Liner
DEAR JACK,
GENERALLY A COATING HAS A SHOT LIFETIME, ESPECIALLY BY ABRASIVE POWDERS. SOME TIMES IS DANGEROUS TO DECREASE THE FRICTION BECAUSE THE SILO PRESSURE WILL INCREASE AND THIS CAN COARSE STATIC PROBLEMS.
WE CAN HELP YOU WITH EXPERTISE AND MEASUREMENT OF POWDER IN ORDER TO CALCULATE THE POSSIBLE BRIDGING DIAMETER. WE CAN ALSO DELIVER THE COMPLETE INSTALLATION WITH GUARANTEE FOR NO BRIDGING AND NO RAT-HOLING.
FOR YOUR OWN EDUCATION I SUGGEST TO FOLLOW OUR COURSE
“QUALITY CONTROL AND POWDER TECHNOLOGY” IN NOVEMBER 2003.
IPT
SINCE 1974 SERVING THE WORLD
QUALITY CONTROL
AND POWDER TECHNOLOGY
5-7 November 2003
Delft - Netherlands
SPONSOR:
IPT-Industrial Powder Technology-Vaduz
Delft University of Technology
Faculty of design, Engineering & production
Transport and Logistic Technology
CHAIRMAN: Dr Ir. I A S Z Peschl
Prof. Dr. Ir. G. Lodewijks
1st DAY
INTRODUCTION
A. POWDER TECHNOLOGY
B. MEASUREMENT OF POWDER PROPERTIES
2nd DAY
C. QUALITY CONTROL - ON LINEN AND IN LABORATORY
3rd DAY
·SEGREGATION
·AND DEGRADATION
·DUST: PROBLEMS AND SOLUTIONS
Consult our website: WWW.IPT-ONLINE.COM - for full program and registration form
BEST REGARDS
DR. IVAN PESCHL ■
Re: Plasma Coating
Jack,
I agree with both the replies you have received in that there is no substitute for proper design both on the shear tester where you are able to quantify the friction characteristics of the liner and on bin wall loading where you must of course take the testwork into account when designing the structures. The test results will also reveal the critical ratole dimensions and other parameters suggested by Dr Peschl.
In terms of plasma coating it is in itself a good product however very expensive, applied at less than a millimeter thickness and thus used primarily for small areas, building up shafts and the like. Although it may have been done I am not aware of it being used on large areas as a bin lining.
The range of liners available today is vast and it appears that the dilema you face is not unique as the trade off between friction characteristics and wear resistance has plagued designers in this field for decades.
There are many consultants able to assist you, myself included, and I would urge you to consider shear tests on your materials with a range of liners. The composite glass and alumina tile lining is to my mind worth including in your testwork as it goes a long way to meeting the demands of both low friction characteristics and good wear resistance.
Good luck to you ■
Plasma Coating
Does anyone have experience with using Plasma Coatings for wall friction reduction for bin/silo/hopper applications ?
Any long term experience with wear and coating life ?
Plasma coatings usually give low traction and low adhesion on the wall surface.
Thanks in advance,
Jack ■