Liquid purification or separation – Flow – fluid pressure or material level – responsive – Flow cut-off requiring reset
Patent
1997-07-31
1999-05-25
Hruskoci, Peter A.
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Flow cut-off requiring reset
210108, 210167, 210295, 2103232, 21032301, 210411, 2104161, 494 5, 494 24, B01D 2966
Patent
active
059067330
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to liquid cleaning systems of the type in which a liquid is pumped around the system by way of a self-cleaning, barrier filter of the so-called back-flush type, and in particular relates to the incorporation of a fluid-powered centrifugal cleaner to process the contaminated liquid back-flushed from the barrier filter.
Self-cleaning barrier filter units are well known in the art in which a housing contains a plurality of filter elements or discrete surface regions each having an inlet surface exposed to a common inlet chamber of the pumped fluid and an opposite, outlet, surface exposed to a common outlet chamber in which the filtrate, the cleaned fluid, is collected before leaving the unit still under pressure. In addition, the inlet chamber has a shield or cover member which is operable periodically to isolate each inlet surface in turn from the inlet chamber and connect it instead to a rejection conduit which leaves the housing, so that as the shield member moves from element to element the temporarily shielded element is subject to reverse flow from the outlet chamber which serves to lift contaminant debris from the inlet surface of the element and flush it along the rejection conduit.
Such self cleaning barrier filter units may operate in a so-called intermittent manner, in which the shield or cover member moves only occasionally between inlet surface regions, and possibly limiting flow through the inlet surface region for a predetermined interval less than the total time it serves that region and/or whilst it is changing between inlet surface regions, or so that the flow of back-flushed liquid is more continuous but from a continuously varying, and frequently cleaned, region of inlet surface.
Whereas it is conventional in full flow or barrier filter design that each filter unit passes liquid with minimum pressure difference across it (subject of course to having a pore size to trap particles of the required dimensions), it is found that to efficiently flush such trapped contaminant particles from a filter requires a large pressure difference to be available to establish a high flow rate through the filter and carry them from the inlet surface region. However, if the filter element should become significantly or completely blocked to liquid passage, possibly over a period of time by inefficient flushing of the contaminants, the prolonged and repeated application of significant pressure difference across the filter region risks effecting physical damage to the underlying structure of the pressure filter in that region.
Thus it is important to the operating life of the filter unit that the back-flushing removes contaminants from the back-flushed region efficiently and without permitting a progressive accumulation.
Most simply the back-flushed liquid, despite the high concentration of contaminants, is returned directly to the reservoir from where it is subsequently pumped around the system and the solid contaminants are again held by the barrier filter. Whereas such an arrangement ensures the contaminants are contained in the system between the reservoir and barrier filter, the liquid in the reservoir does become progressively more contaminated.
As indicated above, a conventional full-flow or barrier type filter element normally intends to produce a relatively small pressure drop across it as liquid flows therethrough and it is known to interpose such a further barrier filter between the back-flush arrangement and the reservoir to isolate solid contaminant without significantly reducing the pressure difference applied across the back-flushed region of the filter.
However, such further barrier filter whilst having of necessity a significant surface area, is capable only of trapping a relatively small volume of contaminants and therefore is necessarily coarse if it is not to become blocked in a very short time. In practice therefore, such filters serves only to trap large particles whilst permitting small particles of soot etc to remain in the li
REFERENCES:
patent: 2858941 (1958-11-01), Darnell
patent: 3784092 (1974-01-01), Gibson
patent: 3791576 (1974-02-01), Bazil
patent: 3907686 (1975-09-01), Fletcher et al.
patent: 4352739 (1982-10-01), Oliver, Jr. et al.
Hruskoci Peter A.
The Glacier Metal Company Limited
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