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Clean in Place Filter replacing Bag Filters
Date : August 2006
Fluid : Viscous food ingredients
Flowrate : 45 m3./hr 9 165 gpm )
Level of suspended solids : a high level of suspended solids
Line size : 3"
Working pressure : up to 10 barG using PD pumps
Retention rating : 600μ
Purpose of filter : remove miscellaneous debris & packing etc
Requirement:
The client had been successfully using a duplex tough woven polypropylene bag filter
arrangement to filter viscous food ingredients and similar products for many years.
They ideally wanted to use a permanent filter media that could be regenerated and
reused continually and reduce their inventory and minimise operator intervention in
the process.
Problems to be overcome:
The bags although very tough woven polypropylene,
which can often be washed and reused on many
applications, cannot be cleaned on this process as they
become grossly contaminated with solids. Mesh baskets
were trialled but encountered the same problem in that it
was not possible to clean them. In order to achieve
uninterrupted flow the use of a duplex filter was
required.
Solution:
We supplied them with an RPA model DCF1600 Disc Cleaned Filter which utilises a
very robust 380 micron slotted wedgewire element. As the apertures are slot shaped it
was decided to use a finer grade than the 600 micron bags they had been using in
order to achieve a similar level of separation.
Flow enters the vessel at the top - to the side and flows down through, from the inside to the outside of the element. Debris is collected on the inside of the element. A Teflon cleaning disc shaped doctor is actuated by a piston and cleans the debris off the element and deposits it in a sump below the element for periodic discharge, by the line pressure, upon the purge valve opening. The cleaning action is continuous and keeps the delta-P to a minimum at all times. The purging of solids can be set for timed intervals based on the solids loading.
The filter can be fully automatic requiring no operator intervention and the cleaning and purging cycle can be initiated by Differential Pressure sensors on some applications.
The piston seal in the lid is a flush seal which is useful on applications with sticky fluids and abrasive constituents which might damage the piston. They are also available in a Twin version using twin pneumatic actuators mounted outboard and driving the central doctor drive shaft for applications where the fluid might damage the pneumatic pistons and therefore needing isolation from them.
Hall Pyke has used DCF filters on fluids with viscosities up to 1 million centipoises.
