GB1283075A - Improvements in or relating to filter units - Google Patents

Abstract

1283075 Filters ASSOCIATED ELECTRICAL INDUSTRIES Ltd 29 May 1970 [30 May 1969] 27464/69 Heading B1D A two-stage filter for removing entrained water from oil or other non-aqueous liquid comprises a closed container 8 divided into two chambers by a tubular partition 17, the outer chamber 20 containing filter material 18 of the molecular sieve type and the inner chamber containing secondary filter material 14. The liquid to be treated is fed in through pipe 2, flows up through filter material 18, weirs over the top of the partition 17 into annular cavity 21, and then passes radially through the filter material 14 to the outlet pipe 3. The apparatus is particularly suitable for removing entrained water from insulating oil employed in transformers and reactors; in this application, filter material 18 is in the form of pellets of an alkali silico-alumina compound, and filter material 14 comprises a cylindrical paper element which is closed at its upper end by metal cap 15. A gauze 19 prevents entry of molecular sieve pellets into the oil supply pipe 2. When the pellets become saturated with water, valves 4 and 7 are closed, plug 13 is removed to allow oil to drain from the container, then cap 12 is removed and the pellets are caught in a suitable manner. The lid 9 may also be opened to allow any remaining pellets to be scooped out. Cap 12 and plug 13 are then replaced; and a fresh supply of pellets is poured into chamber 20. The paper element 14 may be replaced at the same time, if necessary. An electrode such as a metal plate may be disposed within the molecular sieve material in chamber 20; and the electrical resistance between the plate and the wall of the container may be measured in order to determine when the molecular sieve material becomes saturated with water. Also described is a two-stage filter unit (Fig. 3-not shown) wherein the molecular sieve material is contained within a metal inner container of annular form having perforated top and bottom end walls. This construction facilitates replacement of the molecular sieve material.