As previously answered, coloration is usually due to release of metal ormetal oxide in during your clay processing.

We specialize in welding and thermalspray overlay for wear application.

It can be more costly at first but more interesting in the long run (less downtime, less maintenance) but you can use either hardfacing material that are not iron based (nickel, cobalt) with tungsten carbide or other hard particles. Some of our alloys are also repairable so you can also easily rebuild the original equipment when it starts to wear down.

Ceramic or polyurethane can work too in some cases and have their own advantages and inconvenients.

It depends on wear rate and economic of your case (we deal with equipments in Mining that only last 1 h without proper protection and some other that we brought from 3 months to now 2 years) ■

Calcined Chinaclay will be ground by our ceramic lined Alpine Super Orion ball mills in circuit loop with Alpine classifier.

The wear rate of calcined chinaclay depends on the temperture of calcination. In any case the ceramic wear protection will be required to avoid iron contanimation of the fine product.

Please contact us or our office in Chennai for suitable equipment. ■

Nobody knows - it must be too specialised.

Try Google for Vendors and talk to them direct. ■

L o n g s h o t ??

Colour change might be due to a further oxidation level of freshly exposed surfaces which in turn has increased the hardness of the nip product.

As John RZ says this is a process issue probably caused by unforeseen mechanical disturbance of the chemical properties. Assuming the grinder was reasonably accurately selected it might be helpful to introduce a measure of inertness into the proceedings. ■

You want a white product. Discolouration is due contamination of iron particles from wear of grinding mill components.

You may consider using a ball mill with ceramic liners and grinding media. Similar mills are used in white cemet plants for grinding raw meal / clinker. Calcined china clay is not harder to grind than clinker forwhite cement.

vinayak sathe : vianayak.sathe@gmail.com ■

Please let me know of any specific questions you might have in regards to color change. General Kinematics manufactures vibratory mills that will suite your needs.

Best Regards,

Todd ■