Crushing Silica

Being a silica compound, I suspect this is relatively high on the mohs scale for hardness, maybe 7. Typical crushers would not likely do this to the size you need.

One possibility is a type of crusher that crashes two streams of feed into each other at very high speeds. This process causes little contamination from wear part shedding. Barmac and Simplicity are both brands I have experience with. Barmac is made by Metso which is an international company that makes a wide variety of crushing, grinding and milling equipment. I am not plugging them but their web site has explanations of various types of reduction equipment.

A cage mill could also do it but they cause a slight amount of wear part contamination that you may be able to remove with a magnet. A tube mill with ball or rod media is another possibility.

Depending on how much you use, maybe you should be looking to your silica suppliers. It is very common for this type of material to be available sized to your specific needs. There are companies whose principal job is to size minerals and ceramics for the end user.

Fine silica is used in the food industry for many things. I believe if you look there you will find it even finer then what you want.

Was even told while working as a contractor at a silica plant that the big breweries put in beer to give it body and clarity.

It's also a dietary supplement to help one absorb and utilize calcium better.

One of the abrasives used it tooth paste.

I believe these people will have what you want.

http://www.grace.com/

How expensive are the flow control valves? Would it be worth it to change them out on a scheduled downtime maintainance cycle instead of getting a crusher? Do you think that by making the grit smaller, you will get much less damage to the flow control valves? Is there a better material you can use instead of silica? Say, something a bit less abrasive, like, say, sawdust? Could you pass the silica through a flame to cause it to "ball up" instead of being sharp like it is now?

As far as I know fumed silica in the particle sizes 10 - 40 nm is used as filler for LIM applications. 0.39 mm is 10000 times larger. It is doubtful that you get the desired reinforcement with such large filler size. Is there any specific reason for this?

http://www.aerosil.com/product/aerosil/en/Pages/default.aspx

You don't mention the type of valve you are using. Rubber pinch valves are likely the best. They are available manually actuated, direct air actuated, air over mechanical pinch, hydraulic and electric. Clarkson does air over hydrualic $$$, Larox and Red Valve have a wide veriety (I have sold simple Red Valves that are performing very well to replace Clarkson), Onyx has small valves, RF Valve has 1" - 60", Richway has 1/4" - 2", & Schubert & Salzer has up to 2".