Ammonium Sulphate is hygroscopic material and if the dryers are not working the moisture in the material cakes the material in the silo. I cold conditions probable the air passes through it dew point and condensation inside the silo causes caking.

Solution to your problem is to avoid caking in the first place liners and cone angle alone will not work . Lagging and cladding the silo will help coupled with a dehumidifier to keep the top silo air dry. Mass flow design is also important to keep the whole silo contents moving. Dead regions will cake with time. ■

You are getting what is termed as "ratholing" due to cohesion which is common with conical bins at 45 degrees discharge. This is due to improper design of the bin.

See http://www.jenike.com/Solutions/poorflow.html for more information ■

Sanjay,

You may want to consider a live-bottom feeder and reducing or eliminating the cone at the bottom of the hopper. The angle of flow will not be important and ratholing will be eliminated. Additionally, throughput rates will be kept constant if the material becomes sticky when wet. A Steele even-feeder will eliminate this problem.

Feel free to contact me if we can be of assistance.

-Jon Babek

jonbabek@jcstele.com

www.jcsteele.com ■

There are times when all you are left with is to fit a mechanical discharger.

Do a Google on "bin discharger", there are a lot to choose from but you will probably have to modify your bin. ■

The information indicates cohesive arching as the cause of 'hand-up's'' as freezing of the contents would create impossible discharge conditions and be easy to recognise. Lining the cone, even at a steeper angle, would be unduly expensive and inefficient. Clearly, no wall friction tests have been undertaken as these would not be relevant to a 45 degree cone except for confirming final, unconfined clearance.

If headroom is available, a section of the silo cone could be replaced with a construction to exploit a combination of mass flow with Sigma two relief plane flow to secure the benefit of a massive increase in effective outlet. Failing the availability of this space and possibly a cheaper option, a cantilever-mounted, progressive-exptraction screw from the hip, down the cone would provide hoop stress relief and positive discharge from a flow slot effectively seven foot long to eliminate arching and ratholing hazards; contact lyn@ajax.co.uk for further information. ■