Dry mix cleaning procedures

I have two dry mix tanks where there is residual dust left behind after processing. What is the industry standard for "cleaning" these? The introduction of water does not seem like the thing to do since there are no sanitary drains. Do we simply let them sit between process batches, sealed from possible pest introduction?

Do you process any Allergens in those tanks? and are they used for the same ingredients each time, no exceptions?  

Same raw materials each use, no allergens

Sorry for the questions, but details are important for solutions lol; 

1. What have you been doing?

2. Do the tanks have Tri-Clamp connections?

3. Do you have process air available?

We are starting up an rehabbed process - the cleaning practices in the past are suspect to say the least.

These are tanks equipped with augers dry mixing approximately 3000 lbs. of drys. Primary mixer drops to secondary mixer where the material is extracted via an auger feed system.

Air is available. Blowing things out seems the best option. Introduction of water into the dry system would cause caking of the materials. The surfaces of the SS are obviously very polished through the natural operating process.

That's a tricky one, my instinct says it shall be clean lol, I'd call the manufacturer and see what they recommend, but for now i'd use Process air. Just be a thorough as possible.

Just remember, if you get inspected, you'll need a scientific bases that defends any method you use.  

If you can put some feelers out regarding the scientific basis issue, that would be great. I will work with our sanitation contractor regarding testing.

In other input is appreciated.

Have you thought of Powder Pigging? We have successfully depolyed the technology in a pneumatic conveyor in UK.  Although normally used with liquid products it works with dry processes as well and means you can push a pig through using process air, wiping the pipe walls and dislodging any material without needing to use a wet cleaning process.