Drum filters generally rely on the residual precoat for successful operation. The precoat thickness will influence also pressure drop at the beginning of the cycle. Pulp concentration is also involved in filtration efficiency, especially if time is considered.

Cloth simply has to maintain a precoat and accommodate the corrosive effects of the solvent. A good cloth manufacturer will put you straight in no time flat.■

Dorr Oliver would have had enough sense to make the drum from suitable material for the intended duty. Either you've got it or you haven't. Pitting.

Kindly post one question at a time. First you asked about cloth: now you ask about drum suitability. I suppose sometime you will ask about the consideration of nozzle load pulsation, seal face pressure and pulp inlet turbulence.

In Saath Efrika in the 1970's Palborwa copper mine managed to fit a drum in the wrong way round and then had the gall to complain to Batemans that it wasn't working properly. Drum filters are very effective if they are used correctly, despite the arduous duty. ■