Self cleaning by-pass filtration arrangement

In a fluid feed system, particularly a lubrication circuit of a turbo-engine, comprising a fluid reservoir, a supply pump, and user circuits supplied with fluid from said reservoir by said pump, a filtration arrangement comprising a main filter between said pump and said user circuits, a by-pass circuit by-passing said main filter in parallel therewith, said by-pass circuit including a by-pass control valve and a relief filter in series with said valve, and a return circuit connected between said by-pass circuit and said feed system upstream of said supply pump, said return circuit including throttling means and being connected to said by-pass circuit at a position downstream of said by-pass valve such that, when said main filter is blocked and said by-pass valveis open, fluid flows to said user circuits through said relief filter while a portion of said fluid passing through said by-pass circuit is returned upstream of said supply pump via said return circuit, and, when said by-pass valve is closed and said main filter is operational, a portion of the fluid flowing through said main filter for supply to said user circuits is returned upstream of said supply pump through said return circuit after passing through said relief filter in a direction opposite to th flow therethrough when said by-pass valve is open, thereby effecting a counter-flow cleaning of said relief filter.