Abstract: There is described a liquid treatment installation including a tank which defines a substantially vertical flow channel of circular cross section. Disposed coaxially in the flow channel there is a spiral separator plate pack 20 which comprises one or more conical helical plates which define at least one helical flow passage between axially facing surfaces of the plate or plates. The conical helical plate or plates of the separator plate pack 20 consist of a plurality of platelets 10, which have dimensions that allow them to pass through an opening 21 which runs axially through the centre of the spiral separator. The invention also relates to a method of constructing the above liquid treatment installation and to a method for assembling the spiral separator plate pack 20.

Abstract: A method and apparatus for separating suspended solid particles and/or fluid droplets from a body of liquid is described. Fluid is caused to flow through at least one helical flow path defined between axially facing surfaces of a number of conical helical plates. Preferably, a substantially vertical flow channel of circular cross-section has disposed therein at least one conical helical plate with a diameter substantially equal to that of the flow channel. The conical helical plate or plates are arranged coaxially in the flow channel and define at least one helical flow path coaxial with the flow channel between axially facing surfaces of the plate or plates. The plate or plates are preferably capable of rotating about the axis of the flow channel, and may be driven. While they may be driven at a greater or lesser speed, they are preferably driven at a speed so as to approximately correspond with the flow rate of the liquid.