GB2127317A - Filter cleaning - Google Patents

Abstract

A filter has an inlet for fluid to be cleaned, an outlet for cleaned fluid and an inward-flow tubular filter element 13 disposed in the flow path between the inlet and the outlet. The filter element is cleaned by jets of water delivered on to the interior of the element through an axially reciprocating nozzle 21 at more than 1000 psi. <IMAGE>

Description

SPECIFICATION Filter assembly This invention relates to a filter assembly and to a method of cleaning the filter element of such an assembly.

At present filter assemblies are provided with automated cycles for backwashing either with internal filtrate fluids by reversing the flow of the fluid or by external cleaning agents. In these cases the fluid just cleaned by the filter has its flow reversed or a cleaning agent is passed back through the filter element carrying collected particles with it. This conventional backwashing thus relies upon a reverse flow of fluid and requires filling of the filter chamber to ensure that the filter element is cleared throughout. Normally, a differential pressure sensor initiates the beginning of a backwash cycle at a predetermined pressure drop across the inlet and outlet headers.

An object of the present invention is to provide an improved filter assembly and method of backwashing.

According to the present invention a filter assembly comprises an inlet for fluid to be cleaned, an outlet for cleaned fluid and a filter medium disposed in the flow path between the inlet and the outlet, the improvements comprising the provision of backwash means including one or more jets positionable downstream of the filter medium and operable to backwash the filter medium by directing a jet or jets of high velocity cleaning fluid at the filter medium.

Preferably the filter medium comprises a metallic, cylindrical filter cartridge, eg of stainless steel, and a reciprocal backwash means positioned with the cartridge.

The invention also includes a method of backwashing a filter assembly comprising an inlet for fluid to be cleaned, an outlet for cleaned fluid, and a filter medium disposed in the flow path between the inlet and the outlet, the method comprising the steps of providing a backwash means having one or more jets, positioning the jet or jets downstream of the filter medium, supplying cleaning fluid to the backwash means at a pressure in excess of 1000 psi, and directing the high velocity cleaning fluid issuing from the jet or jets so as to play upon the filter medium and to clean it by the force and the cleaning fluid itself.

Preferably the filter medium is a cylindrical stainless steel filter element, the backwashing method comprising displacing the jet or jets in axial direction so as to clean the filter element throughout its length.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a front elevation of a filter assembly in accordance with the present invention; Figure 2 is a section as X-X in Figure 1; Figure 3 is a section as Y-Y in Figure 1; and Figure 4 is a view on the direction of arrow A showing the top of one of the filter units.

In the drawings a filter assembly 1 comprises two substantially identical filter units 2 mounted upon a rectangular frame work 3 consisting of top and bottom sections 4, 5, side sections (not shown) and a central section 6. Mounted upon the central section 6 between the two filter units 2 is a double-acting pneumatic cylinder 7 the purpose of which will be explained later.

Referring to one filter unit 2, and with particular reference to Figures 1 and 2, it will be seen that the filter unit is mounted to the framework 3 by bolts 8 and comprises a filter chamber 9 locked between top and bottom covers 10, The filter chamber 9 consists of an outer cylindrical casing 12 and includes a cylindrical filter element 13 mounted within the chamber 9 dividing it into two portions 14 and 15. The filter element 13 may be of any desired mesh but, where two units are combined in series as illustrated, the mesh sizes may be different such as 75 micron and 25 micron.

The filter element 13 is supported from collapse by a larger mesh screen 16 and a metallic cage 17 as seen in Figure 2.

The top cover 10 includes an inlet 18 to the portion 14 of the filter chamber 9 and the bottom cover 11 includes an outlet 19 from the portion 15 of the filter chamber 9, with a closable drain outlet 26 also being provided for backwashing as now explained.

Disposed centrally within each of the filter units 2 is a reciprocal backwash member 20 comprising one or more back washing jets 21 are the number of jets being determined by the optimum spread of the jet for particular applications free end thereof. The backwash member 20 passes through the top cover 10 and is supported therein by bearings 22 with appropriate seals 23 being provided as necessary.

The backwash member 20 consists of a tubular conduit 24 through the top of which water at a high pressure over 1000 psi is supplied to the jets 21. The backwash member 20 is connected to the pneumatic cylinder 7 by a bar 25 so to be moved thereby.

In use dirty fluid passes to the filter chamber 9, through the inlet 18 filling portion 14, and is pushed through the filter element 13 to the chamber portion 15 and outlet 19, particles larger than the mesh size being trapped by the filter element. When the filter element 13 is to be cleaned as determined by pressure switch or regular time control, the inlet 18 and outlet 19 are closed and the drain outlet 26 opened. Any residual fluid in the filter chamber 9 passes to drain and then the backwash member 20 is supplied with high pressure water and reciprocated within the filter chamber 9 by means of pneumatic cylinder 7. Instead of filling the portion 15 as in conventional backwash procedure so that particles are removed by backflow, the particles trapped on the filter element 13 are pushed off the filter element by the force of the high velocity water issuing from the jets 21.The particles then pass with the water to the drain outlet 26.

The filter units 2 are cartridge filters with filter elements 13 which may be replaced simply by releasing bolts 27 and separating the bottom cover from the top cover. The filter elements 13 are suitably of stainless steel material to withstand the velocity of the backwashing jets. The pressure of the water supplied to the backwash member 20 may be in the range of 1000-5000 psi preferably 2000-3500 psi eg a typical example would consist of using water of 2000 psi at approximately 10 gallons per minute per filter element. Although, water is the preferred backwashing fluid other fluids may be used if desired.

Preferably, as indicated above, the pressure differential over the filter elements 13 is constantly monitored so that a backwash sequence is automatically instituted.

The filter assembly of the present invention may consists of one, two or more filter units and may be part of a high pressure cleaning apparatus or, alternatively, it may be an independent apparatus having its own means for providing the high pressure water as described. The backwashing cleaning operation is extremely efficient and fast. This enables an operator to use just one filter set as opposed to the prior art arrangement of a bank of filters with some being out of operation for backflushing at any one time.

If desired there is another point; the backflushed water or cleaning fluid may be collected in a tank with a micron filter base so that it is allowed to drain through before being returned to the system prior to the filters, thereby minimising or event totally removing any loss of cleaning fluid due to backwash.

This is due to the fact that in the present invention small quantities of water for backflushing are used typically a maximum of 5 gallons per cylinder and to treat this small quantity of water is easy and relatively cheap. If desired it could even be centrifuged out.

The system of the present is ideally a fully automated system with butterfly or ball valves, hydraulically, electrically or pneumatically controlled to divert the water and close off the flow from the pump as required.

CLAIMS (Filed on 24.8.83.) 1. Afilter assembly comprising an inletforfluid to be cleaned, an outlet for cleaned fluid and a filter medium disposed in the flow path between the inlet and the outlet, the improvement comprising the provision of backwash means including one or more jets positionable downstream of the filter medium and operable to backwash the filter medium by directing a jet or jets of high velocity cleaning fluid at the filter medium.

2. A filter assembly according to claim 1 wherein the filter medium comprises a metallic cylindrical filter cartridge.

3. A filter assembly according to claim 1 or 2 wherein the backwash means is reciprocal relative to the filter medium.

4. A method of backwashing a filter assembly comprising an inlet for fluid to be cleaned, an outlet for cleaned fluid, and a filter medium disposed in the flow path between the inlet and the outlet, the method comprising the steps of providing a backwash means having one or more jets, positioning the jet or jets downstream of the filter medium, supplying cleaning fluid to the backwash means at a pressure in excess of 1000 psi, and directing the high velocity cleaning fluid issuing from the jet or jets so as to play upon the filter medium and to clean it by the force of the cleaning fluid itself.

5. A method of backwashing a filter assembly according to claim 4, the filter medium being a cylindrical cage, the method comprising the further step of reciprocating the backwash means within the filter cage in axial direction.

6. A filter assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. A method of backwashing a filter assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. water supplied to the backwash member 20 may be in the range of 1000-5000 psi preferably 2000-3500 psi eg a typical example would consist of using water of 2000 psi at approximately 10 gallons per minute per filter element. Although, water is the preferred backwashing fluid other fluids may be used if desired. Preferably, as indicated above, the pressure differential over the filter elements 13 is constantly monitored so that a backwash sequence is automatically instituted. The filter assembly of the present invention may consists of one, two or more filter units and may be part of a high pressure cleaning apparatus or, alternatively, it may be an independent apparatus having its own means for providing the high pressure water as described. The backwashing cleaning operation is extremely efficient and fast. This enables an operator to use just one filter set as opposed to the prior art arrangement of a bank of filters with some being out of operation for backflushing at any one time. If desired there is another point; the backflushed water or cleaning fluid may be collected in a tank with a micron filter base so that it is allowed to drain through before being returned to the system prior to the filters, thereby minimising or event totally removing any loss of cleaning fluid due to backwash. This is due to the fact that in the present invention small quantities of water for backflushing are used typically a maximum of 5 gallons per cylinder and to treat this small quantity of water is easy and relatively cheap. If desired it could even be centrifuged out. The system of the present is ideally a fully automated system with butterfly or ball valves, hydraulically, electrically or pneumatically controlled to divert the water and close off the flow from the pump as required. CLAIMS (Filed on 24.8.83.)

1. Afilter assembly comprising an inletforfluid to be cleaned, an outlet for cleaned fluid and a filter medium disposed in the flow path between the inlet and the outlet, the improvement comprising the provision of backwash means including one or more jets positionable downstream of the filter medium and operable to backwash the filter medium by directing a jet or jets of high velocity cleaning fluid at the filter medium.

2. A filter assembly according to claim 1 wherein the filter medium comprises a metallic cylindrical filter cartridge.

3. A filter assembly according to claim 1 or 2 wherein the backwash means is reciprocal relative to the filter medium.

4. A method of backwashing a filter assembly comprising an inlet for fluid to be cleaned, an outlet for cleaned fluid, and a filter medium disposed in the flow path between the inlet and the outlet, the method comprising the steps of providing a backwash means having one or more jets, positioning the jet or jets downstream of the filter medium, supplying cleaning fluid to the backwash means at a pressure in excess of 1000 psi, and directing the high velocity cleaning fluid issuing from the jet or jets so as to play upon the filter medium and to clean it by the force of the cleaning fluid itself.

5. A method of backwashing a filter assembly according to claim 4, the filter medium being a cylindrical cage, the method comprising the further step of reciprocating the backwash means within the filter cage in axial direction.

6. A filter assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. A method of backwashing a filter assembly substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.