SE464062B

SE464062B - Self-cleaning filter

Info

Publication number: SE464062B
Application number: SE9000803A
Authority: SE
Inventors: Ulf Steiner
Original assignee: Ulf Steiner
Priority date: 1990-03-07
Filing date: 1990-03-07
Publication date: 1991-03-04
Also published as: SE9000803D0

Abstract

The invention relates to a pressure filter 1 for continuous and automatic rough-filtering of liquids, which is rinsed automatically at pre-set time intervals or at a pre-set pressure-drop value. The rinsing is achieved by a piston 9 being conducted to and fro inside a filter cage 2 provided with a large quantity of small holes 6. Between the inner side of the filter cage 2 and the periphery of the piston 9 there is an annular gap 10. Upon movement of the piston 9 the velocity of the liquid flow is substantially increased, thereby producing a severe fall in pressure in and close to the gap 10. This fall in pressure generates a flow of liquid through the holes 6 which loosens impurities which were stuck in the holes 6. The impurities are removed through a scavenging duct 8. The piston 9 can have a bevelled or otherwise configured periphery. Its guidance inside the filter cage 2 can be effected pneumatically, hydraulically or electrically. The filter cage 2 can be substantially cylindrical, conical or can have a corrugated or helical contacting surface. A sensor detects drops in pressure across the filter cage 2. <IMAGE>

Description

15 20 25 30 35 40 464 062 2 för klämning mellan skrapverktyg och filterkorg är dessutom stor. 15 20 25 30 35 40 464 062 2 for clamping between scraper tool and filter basket is also large.

För rengöring av en filterkorg utan extra spolvatten föreslås i svensk utläggningsskrift 7300770-0 att man i en konisk filter- korg bygger in en vippventil som genom att till en del strypa flödet genom filterkorgen inuti denna kan åstadkomma en virvel- bildning som avlägsnar ansamlade föroreningar. Denna uppfinning är dock begränsad till i det närmast koniska filterkorgar och möjlig- gör ej fullständig rengöring då vippventilen ej är flyttbar längs filterkorgen.For cleaning a filter basket without extra rinsing water, it is proposed in Swedish Offenlegungsschrift 7300770-0 that a tilting valve is built into a conical filter basket which, by partially restricting the flow through the filter basket inside it, can cause a vortex formation which removes accumulated contaminants. However, this invention is limited to almost conical filter baskets and does not allow complete cleaning as the rocker valve is not movable along the filter basket.

Uppfinningen enligt denna ansökan saknar nackdelarna i ovan- nämnda patentdokument, har en enkel uppbyggnad som fullständigt avviker från känd teknik, åstadkommer effektiv rengöring av hela filterkorgen utan flödesavbrott och gör det möjligt att även avlägsna föroreningar som är hårt fastsatta i filterkorgen, t ex fibermaterial och längsträckta föremål.The invention according to this application lacks the disadvantages of the above-mentioned patent documents, has a simple construction which completely deviates from known technology, provides efficient cleaning of the entire filter basket without flow interruptions and makes it possible to remove contaminants that are firmly attached to the filter basket, e.g. elongated objects.

Uppfinningen beskrivs närmare nedan med hänvisning till de bifogade, exemplifierande, schematiska och icke begränsande figu- rerna 1 - 6, där identiska delar har samma hânvisningsbeteckningar och i vilka figur 1 visar ett tryckfilter 1, utan ansamlade föroreningar, längs dess centrumaxel från sidan i ett snitt, vilket löper genom en filterkorg 2 som är försedd med ett stort antal små hål 6, en inloppsledning 3, en utloppsledning 5, en spolledning 8 med en ventil 7 samt en kolv 9 som visas i utdraget läge, figur 2 visar tryckförhàllandena i tryckfiltret 1 enligt figur 1, figur 3 visar tryckfiltret 1 i det fall då föroreningar ansamlats i filterkorgen 2 och kolven 9 fortfarande befinner sig i utdraget läge, figur 4 visar tryckförhàllandena i tryokfiltret 1 enligt figur 3, W figur 5 visar tryckfiltret 1 när kolven 9 framförs inuti filterkorgen 2, figur 6 visar tryckförhàllandena i tryckfiltret l enligt figur 5.The invention is described in more detail below with reference to the accompanying, exemplary, schematic and non-limiting figures 1-6, where identical parts have the same reference numerals and in which figure 1 shows a pressure filter 1, without accumulated contaminants, along its center axis from the side in a section, which runs through a filter basket 2 which is provided with a large number of small holes 6, an inlet line 3, an outlet line 5, a flush line 8 with a valve 7 and a piston 9 shown in the extended position, figure 2 shows the pressure conditions in the pressure filter 1 according to Figure 1, Figure 3 shows the pressure filter 1 in the case where contaminants have accumulated in the filter basket 2 and the piston 9 is still in the extended position, Figure 4 shows the pressure conditions in the pressure filter 1 according to Figure 3, W Figure 5 shows the pressure filter 1 when the piston 9 is advanced inside the filter basket 2, figure 6 shows the pressure conditions in the pressure filter 1 according to figure 5.

Tryckfiltret 1 innefattar en cylindrisk filterkorg 2, vilken har ungefär samma innerdiameter som en inloppsledning 3. Tryck- filtrets 1 utloppsledning 5 är företrädesvis placerad i en del av tryckfiltret 1 som är belägen mitt för filterkorgen 2 i dess nedströmsände. Inloppsledningen 3 och utloppsledningen 5 har 10 15 20 25 30 35 40 3 464 062 ungefär samma tvärsnittsarea. Filterkorgen 2 är försedd med ett stort antal små hål 6. Den sammanlagda arean för hålen 6 är mycket större, företrädesvis 3 - 4 gånger större, än tvärsnittsarean för inloppsledningen 3.The pressure filter 1 comprises a cylindrical filter basket 2, which has approximately the same inner diameter as an inlet line 3. The outlet line 5 of the pressure filter 1 is preferably located in a part of the pressure filter 1 which is located in the middle of the filter basket 2 at its downstream end. The inlet line 3 and the outlet line 5 have approximately the same cross-sectional area. The filter basket 2 is provided with a large number of small holes 6. The total area of the holes 6 is much larger, preferably 3-4 times larger, than the cross-sectional area of the inlet line 3.

I figurerna 2, 4 och 6 visas tryckförhållandena i tryckfilt- ret 1 i tre olika fall. Förutom ovan angivna beteckningar åter- finns i dessa figurer nedanstående beteckningar P,== trycket vid insidan av filterkorgens 2 uppströmsände IQ = trycket vid insidan av filterkorgens 2 nedströmsände, IQ = trycket vid utsidan av filterkorgens 2 uppströmsände, Iﬂ = trycket vid utsidan av filterkorgens 2 nedströmsände, IL = vätskans medelhastighet vid inloppet till filterkorgen 2, IL = vätskans medelhastighet vid filterkorgens 2 utsida mitt för filterkorgens 2 nedströmsände, Pm visar tryckvariationerna längs filterkorgens 2 insida (heldragen linje), Pm visar tryckvariationerna längs filterkorgens 2 utsida (streckad linje).Figures 2, 4 and 6 show the pressure conditions in the pressure filter 1 in three different cases. In addition to the above designations, these figures show the following designations P, == the pressure inside the upstream end of the filter basket 2 IQ = the pressure inside the downstream end of the filter basket 2, IQ = the pressure outside the upstream end of the filter basket 2, I ﬂ = the pressure outside the filter basket 2 downstream end, IL = mean velocity of the liquid at the inlet to the filter basket 2, IL = mean velocity of the liquid at the outside of the filter basket 2 opposite the downstream end of the filter basket 2, Pm shows the pressure variations along the inside of the filter basket 2 (solid line), Pm shows the pressure variations along the outside of the filter basket 2 .

Med utgångspunkt från bl a Bernoullis teorem och från att, vid icke förorenad filterkorg 2, vätskehastígheten är noll såväl inuti filterkorgen 2 vid dess nedströmsände som utanför filter- korgen 2 vid dess uppströmsände erhålls P,-EQ = (Uf 23,)/2 , med_§ = vätskans densitet P, - P3 = - (U: -3 )/2 Dessa samband visas i figur 2 där man även ser att, vid ej förorenad filterkorg 2, Pm och Pm skär varandra i en punkt som ligger mellan filterkorgens 2 uppströmsände och dess nedströms- ände.Based on, among other things, Bernoulli's theorem and on the fact that, in the case of an unpolluted filter basket 2, the liquid velocity is zero both inside the filter basket 2 at its downstream end and outside the filter basket 2 at its upstream end, P, -EQ = (Uf 23,) / 2, med_§ = density of the liquid P, - P3 = - (U: -3) / 2 These relationships are shown in figure 2 where it is also seen that, in the case of unpolluted filter basket 2, Pm and Pm intersect at a point which lies between the filter basket 2 upstream end and its downstream end.

Tillsammans med de ovan angivna sambanden erhålls P, - P, = (P, - P,) + (v33: + 112,5* )/z Om U,==IL = U blir tryckfallet över filterkorgen 2 således ca 2* Uäšlstörre i dess nedströmsände än i dess uppströmsände. Den vätska som strömmar in i filterkorgen 2 från inloppsledningen 3 kommer därför, så länge hålen 6 i filterkorgen 2 ej är helt eller delvis igensatta, att huvudsakligen passera genom hålen 6 i fil- terkorgens 2 nedströmsände. Hålen 6 blir alltså igensatta med föroreningar med början från nämnda nedströmsände. Det uppstår därför en front av föroreningar som rör sig mot nämnda uppströms- ände. Vätskepassagen genom filterkorgen 2 kommer således att efter 10 15 20 25 30 35 464 062 4 hand ske allt närmare uppströmsänden.Together with the above-mentioned relationships, P, - P, = (P, - P,) + (v33: + 112,5 *) / z If U, == IL = U, the pressure drop across the filter basket 2 is thus approx. 2 * Uäšlstörre at its downstream end than at its upstream end. The liquid flowing into the filter basket 2 from the inlet line 3 will therefore, as long as the holes 6 in the filter basket 2 are not completely or partially clogged, mainly pass through the holes 6 in the downstream end of the filter basket 2. The holes 6 thus become clogged with contaminants starting from said downstream end. Therefore, a front of contaminants arises which moves towards said upstream end. The liquid passage through the filter basket 2 will thus, after a hand, take place ever closer to the upstream end.

I figur 3 visas tryckförhàllandena i tryckfiltret l när fronten av föroreningar nått ett stycke uppströms i filterkorgen 2. Efterhand ökar tryckfallet över filterkorgens 2 nedströmsände upp till ett gränsvärde samtidigt som det minskar över dess ned- strömsände. När fronten av föroreningar närmar sig filterkorgens 2 uppströmsände, och därvid vätskan i allt mindre mängd och med allt större svårighet passerar filterkorgen 2, eftersom den sammanlagda arean av icke igensatta hål 6 inte längre är stor i förhållande till tvärsnittsarean för inloppsledningen 3, ökar det totala tryckfallet över filterkorgen 2 snabbt. I Vid renspolning av filterkorgen 2 förfars enligt nedan med hänvisning till figurerna 5 och 6. Först öppnas en ventil 7 till en spolledning 8, vars tvärsnittsarea är avsevärt mindre än tvär- snittsarean för inloppsledningen 3 och som är så placerad att vätskan kan nå spolledningen 8 ofiltrerad, dvs utan att passera hälen 6 i filterkorgen 2. Grövre föroreningar, vilka ansamlats i filterkorgen 2 och som ej fastnat i hålen 6, spolas därvid direkt ut i spolledningen 8. Därefter trycks en kolv 9 in i filterkorgen 2 från dennas nedströmsände mot dennas uppströmsände utmed dennas centrumlinje. Kolven 9 har sådan tvärsnittsarea att det mellan filterkorgen 2 och den inskjutna kolven 9 finns en ringformad spalt 10. Praktiska försök har visat att en radiell bredd för spalten 10 som utgör 1 % - 20 %, företrädesvis 4 %, av kolvens 9 tvärsnittsdiameter leder till optimal renspolningseffekt.Figure 3 shows the pressure conditions in the pressure filter 1 when the front of contaminants has reached some distance upstream in the filter basket 2. Gradually the pressure drop across the downstream end of the filter basket 2 increases up to a limit value while decreasing over its downstream end. As the front of contaminants approaches the upstream end of the filter basket 2, and thereby the liquid in less and less quantity and with increasing difficulty passes the filter basket 2, since the total area of non-clogged holes 6 is no longer large in relation to the cross-sectional area of the inlet line 3, the total the pressure drop across the filter basket 2 quickly. When flushing the filter basket 2, proceed as follows with reference to Figures 5 and 6. First, a valve 7 is opened to a flush line 8, the cross-sectional area of which is considerably smaller than the cross-sectional area of the inlet line 3 and which is positioned so that the liquid can reach the flush line 8. unfiltered, ie without passing the heel 6 in the filter basket 2. Coarse contaminants, which have accumulated in the filter basket 2 and which are not stuck in the holes 6, are then flushed directly into the flush line 8. Then a piston 9 is pushed into the filter basket 2 from its downstream end towards its upstream end along its center line. The piston 9 has such a cross-sectional area that between the filter basket 2 and the inserted piston 9 there is an annular gap 10. Practical tests have shown that a radial width of the gap 10 which constitutes 1% - 20%, preferably 4%, of the cross-sectional diameter of the piston 9 leads to optimal cleaning effect.

Därefter förblir ventilen 7 öppen medan kolven 9 rör sig en eller flera gånger fram och åter i filterkorgen 2 från sitt ut- gàngsläge utanför filterkorgens 2 nedströmsände till ett ändläge inuti filterkorgen 2 nära dess uppströmsände. I spalten 10 uppstår vid kolvens 9 rörelse en avsevärd höjning av vätskeflödets hastig- het. I figur 6 ser man att denna hastighetshöjning åstadkommer en trycksänkning intill spalten 10 samt något uppströms och nedströms denna, så att trycket på filterkorgens 2 insida blir lägre än pà dess utsida och därvid vätskan i detta område strömmar in i fil- terkorgen 2 genom hålen 6. De föroreningar som fastnat i och intill hålen 6 lossnar därför och spolas ut via spolledningen 8.Thereafter, the valve 7 remains open while the piston 9 moves one or more times back and forth in the filter basket 2 from its initial position outside the downstream end of the filter basket 2 to an end position inside the filter basket 2 near its upstream end. In the gap 10, with the movement of the piston 9, a considerable increase in the velocity of the liquid flow occurs. Figure 6 shows that this increase in speed causes a pressure drop next to the gap 10 and slightly upstream and downstream thereof, so that the pressure on the inside of the filter basket 2 becomes lower than on its outside and the liquid in this area flows into the filter basket 2 through the holes 6. The contaminants stuck in and next to the holes 6 therefore come loose and are flushed out via the flushing line 8.

Ovannämnda renspolning sker med förutbestämda tidsintervall eller initieras av en sensor som registrerar tryckfallet över filterkor- gen 2. 10 15 5 464 062 Kolven 9 behöver under sin fram- och âtergående rörelse inte föras ända fram till filterkorgens 2 uppströmsände. Inte heller behöver kolven 9 passera förbi fronten av föroreningar. Denna front förflyttas under ovanstående renspolningsförfarande ändå allt närmare filterkorgens 2 nedströmsände. ' Kolven 9 kan drivas och styras på ett flertal sätt. Exempel- vis kan en rotationsrörelse via ett länksystem överföras till kolven 9. Därigenom kan man använda elektriska eller pneumatiska standardiserade 90-graders vriddon. Drívníngen kan även ske med skruv eller kolv. Styrningen av kolven 9 sker lämpligen utmed en enda utmed filterkorgens 2 centrumaxel placerad gejder, som är utformad sä att det ej uppstår klämning mellan kolven 9 och fil- terkorgen 2.The above-mentioned purge takes place at predetermined time intervals or is initiated by a sensor which registers the pressure drop across the filter basket 2. During its reciprocating movement, the piston 9 does not have to be moved all the way to the upstream end of the filter basket 2. Also, the piston 9 does not have to pass past the front of contaminants. This front is moved during the above flushing procedure still closer to the downstream end of the filter basket 2. The piston 9 can be driven and controlled in a number of ways. For example, a rotational movement can be transmitted via a link system to the piston 9. Thereby, electric or pneumatic standardized 90-degree rotators can be used. The drive can also be done with a screw or piston. The control of the piston 9 suitably takes place along a single guide placed along the center axis of the filter basket 2, which is designed so that no squeezing occurs between the piston 9 and the filter basket 2.

Claims

10 15 20 25 30 40 e 464 062 PATENT REQUIREMENTS

Pressure filter (1) for coarse filtration of liquids with an inlet line (3), an outlet line (5) and a filter basket (2) which is pierced by a larger number of small holes (6), characterized by that the outlet line (5) has approximately the same cross-sectional area as the inlet line (3), that the total cross-sectional area of the holes (6) is much larger, preferably 3-4 times larger, than the cross-sectional area of the inlet line (3), that it is provided with a flush line (8) with a valve (7), which flush line (8) has a cross-sectional area which is substantially smaller than the cross-sectional area of the inlet line (3) and is positioned so that liquid can reach it without passing through the holes (6), and a piston (9), which is movable along the center axis of the filter basket (2) and is so arranged and shaped that in forward and / or reciprocating movement inside the filter basket (2), after opening the valve (7), it has a constant or variable gap (10) between it and the inside of the filter basket (2) and produces a considerable increase in the velocity of the liquid in the gap (10), whereby the resulting pressure drop in the gap (10) and slightly upstream and downstream thereof causes a flow of liquid through the halo (6) towards the interior of the filter basket (2), which flow releases contaminants which are stuck in and next to the heel (6) and which after detachment is flushed out of the pressure filter (1) through the flushing line (8). l

Pressure filter (1) according to claim 1, characterized in that the filter basket (2) and the piston (9) have such dimensions that the gap (10) has a radial width which is 1% - 20%, and preferably 4% , of the cross-sectional diameter of the inlet pipe (3).

Pressure filter (1) according to claim 1 or 2, characterized in that the piston (9) is provided on one or both sides with a peripheral chamfer, preferably only on that of its sides facing the filter basket (2) downstream end, which chamfer may have a constant or variable angle along the periphery of the piston (9).

Pressure filter (1) according to one of the preceding claims, characterized in that the piston (9) has inclined grooves along its periphery, which are designed so that during the reciprocating movement of the piston (9) inside and out the filter basket (2) the liquid at and next to the gap (10) flows spirally along the filter basket (2) in its longitudinal direction.

Pressure filter (1) according to any one of the preceding claims, characterized in that the filter basket (2) has a slightly conical shape with a larger cross-sectional area at its upstream end than at its downstream end.

Pressure filter (1) according to one of Claims 1 to 4, characterized in that the filter basket (2) has a slightly conical shape with a larger cross-sectional area at its downstream end than at its upstream end.

Pressure filter (1) according to one of Claims 1 to 4, characterized in that the filter basket (2) is designed such that its cross-sectional area varies along its length, preferably so that the filter basket (2) has a corrugated or helical inner surface. . Ä

Pressure filter (1) according to one of the preceding claims, characterized in that the speed of the piston (9) can be varied between 10% and 100% of the inlet speed of the liquid entering the pressure filter.

Pressure filter (1) according to one of the preceding claims, characterized in that the piston (9) is guided during its movement inside the filter basket (2) along a single guide placed along the center axis of the filter basket (2) and that its reciprocating movement is obtained. by means of a single or double-threaded screw, by a piston or by an electric or pneumatic 90-degree rotary device whose rotational movement is transmitted to the piston (9) by means of a link system.

Pressure filter (1) according to one of the preceding claims, characterized in that the outlet line (5) is located approximately at the same height as the filter basket (2).

Pressure filter (1) according to one of the preceding claims, characterized in that it is provided with a sensor which detects whether the piston (9) gets stuck during its reciprocating or reciprocating movement and if so emits an alarm signal.

Pressure filter (1) according to any one of the preceding claims, characterized in that it is provided with means which initiate purge of the filter basket (2), which means consist of one or more sensors which measure the pressure drop across the filter basket (2) and timers and which are arranged so that flushing of the filter basket (2) can take place either when preset limit values for said pressure drop are exceeded or with preset time intervals.