Lyn Bates kindly explained to me(via a previous thread about coffee) the mechanism behind the 'Brazil Nut Effect'.

Although perhaps not thoroughly relevant here it does recognise the confusing fluctuations in coffee density.

We need to have some idea about the feed to the packer, the ullage requirement of the pack and also the density of solid coffee.

Mixing is not the answer: far from it. Vacuum could be introduced to degas within an upstream container fitted with a standpipe which should have the discharge very near the receiving/sealing elements. Alternatively, depending on the moisture content, freezing might help.

How did you reach 0.35tm^-1 previously?

Forum members will surely treat this thread to the deference it merits since, with perfect timing, it is the only worthwhile topic during recent times. Thank you very much and a Happy New Year! ■

The density variation will have come about due to the erratic nature of the material behaviour in the flow channel. In a funnel flow hopper the output occurs as a series of collapsing arches, the density depending on how the material has settled from its last discharge, amongst other things such as temperature, humidity and time; apart from any change in the material condition caused by segregation etc. Mass flow gives a more consistent discharge condition, but usually at a slower rate. A review of the overall flow route is needed to assess the situation properly but it may be practical to affect an improvement by a redesign of the feed hopper. A small vibrator linked to the discharge may also be worth a try as a quick fix. ■