NO345889B1

NO345889B1 - Filter systems and methods

Info

Publication number: NO345889B1
Application number: NO20200216A
Authority: NO
Inventors: Runar Tenfjord
Original assignee: Tenko As
Priority date: 2020-02-19
Filing date: 2020-02-19
Publication date: 2021-09-27
Also published as: NO20200216A1; EP4106900A1; WO2021167469A1

Description

FILTER SYSTEMS

The present invention relates to filters, and particularly liquid filters, including but not limited to solutions for cleaning of such liquid filters.

BACKGROUND

Liquid filters are systems that enable unwanted solid particles or other pollutants in a liquid passed through the filter to be separated from the liquid by being filtered and the liquid to be cleaned in this way. In the most basic form, liquid filter systems may typically consist of a dirty liquid inlet sent for cleaning, an insert, such as a filter screen, through which the dirty liquid is forced, and a clean liquid outlet through which the cleaned part of the liquid exits. The solid particles and unwanted substances in the liquid cannot pass through the insert, and they are held on the inlet side of the insert, prevented from exiting with the clean liquid.

Along with the use of liquid filters for a certain period, such solid particles and unwanted substances may accumulate on the insert during the passage of the dirty liquid through the insert and start to block the passage of the fluid. With the inhibition of the passage of the liquid through the insert, liquid filter's working capacity decreases, and after a certain period, the process of filtering cannot be realised as efficiently and reliably as required.

In such a case, the insert may be taken out of the filter for cleaning and placed inside the filter again after a cleaning process. This cleaning method, which includes the process of removing the insert, cleaning it, and re-installing it can in many cases be difficult and time consuming. This can be disadvantageous in systems where the filter is installed with tight space requirements, or where the uptime requirements are high and/or personnel available for cleaning is not abundant.

Some methods are known for cleaning the insert without removing it from the filter. One of these methods is to flush the dirt and solid particles utilising the pressure of the process fluid, by opening a flushing valve placed on the end of the filter insert when it is time to clean it, without applying any additional mechanisms. A problem with such methods is that the flushing liquid cannot be equally applied to all the sections of the insert, making the cleaning process less efficient. In other filter cleaning methods, hydraulic or pneumatic systems are used which are expensive and complicated.

Therefore, they may not be preferred in many applications, due to cost, space requirements and operational reliability.

Publications which may be useful to understand the field of technology include:

US4315820A; US4552655A; US4818402A; US5632903A; US5667683A;

US20060004301A1; US20130026111A1; US20130291645A1; US20130306546A1; GB494417A; CN1331554C; EP2325081A2; and US20170021290. Other related publications include RU2626366 C1, which shows a head filter with a tubular body divided by a transverse partition into a filter chamber and a discharge chamber with a branch pipe, an external rotation drive and a screw connected thereto; EP 2527021 A1 which shows a filtering system that may include a backwashing unit arranged to clean the filter; US 2009/050582 A1, which shows a self-cleaning system for use with a filter; and EP 1785178 A1, which shows a filtering system that includes a filter housing with a fluid inlet and a fluid outlet, a substantially cylindrical filter located within the filter housing, and a backwash body movably mounted within the filter housing for backwashing the filter.

There is consequently a need for improved technology for liquid filters to address the above and/or other challenges. The present invention has the objective to provide such improvements, or at least to provide alternatives to existing technology.

SUMMARY

In an aspect, there is provided a filter having a filter housing having a fluid inlet and a fluid outlet; an elongate filter screen arranged in the filter housing between the fluid inlet and the fluid outlet; a cleaning member movable relative to and adjacent the filter screen; a back-wash outlet arranged at an inlet side of the filter screen; wherein the cleaning member is movable axially along a lead screw arranged in the filter housing by means of rotation of the lead screw by a drive motor. The filter screen has a circular cross-section and the cleaning member is a disc arranged inside the filter screen, the cleaning member being arranged to move adjacent but spaced from the filter screen during movement along the lead screw.

The filter screen and the back wash outlet may be arranged on an insert part which is releasably fixed on a receiver filter housing part, the insert part and the receiver filter housing part together making up the filter housing.

The filter screen may be elongate and arranged about the cleaning member.

The lead screw may be arranged co-axially inside the filter screen.

The lead screw may have a helical lead face operable to engage a follower protrusion arranged on the cleaning member and move the cleaning member axially along the lead screw.

The lead face may be arranged to reverse the movement of the cleaning member when the cleaning member has reached an end position of a pre-determined cleaning stroke.

The follower protrusion may have a first orientation for moving the cleaning member in a first direction along the lead screw and a second orientation for moving the cleaning member in a second, opposite direction along the lead screw.

The lead face may be arranged to change the orientation from the first orientation to the second orientation upon the cleaning member reaching the end position.

The lead screw and/or the cleaning member may be made at least partly of a polymer material, particularly a polymer plastic.

The cleaning member may comprise a plurality of fluid inlets or outlets connected to a pressure source via a fluid connection.

The pressure source may be a pump.

The pressure source may be operable to create a suction in the outlets such as to produce a fluid flow out of the inlet side through the outlets.

The pressure source may be fluidly connected to the back-wash outlet, wherein the back-wash outlet has a lower pressure than that of the inlet side.

The pressure source may be operable to create an outflow of fluid through the outlets such as to produce a fluid flow into the inlet side through the inlets.

The fluid inlets or outlets may be distributed around a peripheral part of the cleaning member. The cleaning member may for this purpose be a disc-shaped cleaning member.

The fluid inlets or outlets may be directed such as to produce a fluid flow substantially perpendicular to the longitudinal axis of the lead screw. Alternatively, the fluid inlets or outlets may be directed such as to produce a fluid flow which is angled and not perpendicular to the longitudinal axis of the lead screw, such as an upward-directed or downward-directed fluid flow.

The fluid connection may be a flexible pipe arranged helically about the lead screw.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics will become clear from the following description of illustrative embodiments, given as non-restrictive examples, with reference to the attached drawings, in which:

Figure 1 is a schematic illustration of parts of a filter.

Figure 2 is a schematic illustration of parts of a filter.

Figure 3 is a schematic illustration of an assembled filter.

Figure 4 is a schematic illustration of parts of a lead screw for a filter.

Figure 5 illustrates a cleaning member and associated components according to an embodiment.

DETAILED DESCRIPTION

The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, ”upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader’s convenience only and shall not be limiting.

Referring now to Figs 1-3, Figure 3 shows a filter 100 according to an embodiment. Figures 1 and 2 illustrate parts of the filter 100. The filter 100 illustrated in Fig.3 is assembled from a filter housing part 13 (see Fig.2) and an insert part 20 (see Fig.1). The insert part 20 is fixed onto the filter housing part 13 and secured by a connection arrangement, such as a flange 14a,b, as illustrated. The connection arrangement sealingly connects the insert part 20 and the filter housing part 13 to produce a filter housing 10 which forms a closed volume but with inlets and outlets described below, configured to contain liquids therein.

The filter 100 has a fluid inlet 11 and a fluid outlet 12. Liquids to be treated by the filter 100 are provided to the inlet 11 and passed through the filter 100 to exit via the outlet 12.

The filter may, for example, be a so-called “Bernoulli filter”, known in the art.

An elongate filter screen 21 is arranged in the filter housing 10 between the fluid inlet 11 and the fluid outlet 12. The filter screen 21 may, for example, be a meshed plate with a suitable opening width or another shaped body with same mechanical effect such as for example a perforated pipe, selected according to the fluids which are to be filtered. The fluid passing through the filter 100 will thus pass through the filter screen 21 to reach the outlet 12. The filter screen 21 separates the interior volume of the housing 10 into an inlet side 25 of the filter screen 21 and an outlet side 31 of the filter screen 21. Solid particles and unwanted substances will thus be prevented by the filter screen 21 from flowing with the fluid to the outlet side 31 and out of the outlet 12.

In addition to the inlet 11 and outlet 12, which form the regular process inlet and outlet, a back-wash outlet 24 is arranged at the inlet side 25 of the filter screen 21. The function of the back-wash outlet 24 will be described below.

A cleaning member 22 is movable relative to and adjacent the filter screen 21, inside the housing 10. The cleaning member 22 is arranged on the inlet side 25 of the filter screen 21. The cleaning member 22 is movable axially along a lead screw 23 arranged in the filter housing 10 by means of rotation of the lead screw 23 by a drive motor 26. In Figs 1 and 3, the cleaning member 22 is illustrated both in its uppermost position, indicated as 27’ and being near the top of the insert part 20 adjacent the motor 26, and in its lowermost position, illustrated as 27. It will be understood that this relates to the same cleaning member 22 shown in two different positions, and only one cleaning member 22 is necessary.

Illustrated in Fig.4, movement of the cleaning member 22 is provided by the lead screw 23 having a helical lead face 41 operable to engage a follower protrusion 42 arranged on the cleaning member 22. The lead face 41 thus moves the cleaning member 22 axially along the lead screw 23, i.e. up and down inside the filter screen 21 when the filter 100 is in the orientation shown in Fig.3.

The cleaning member 22 is arranged to slide axially along one or more axial guide faces arranged to avoid rotation of the cleaning member 22 due to friction the lead face 41 and the protrusion 42. The guide face may be, for example, formed by vertical tracks in the filter screen 21, such as a recess or protrusion in the screen slidingly cooperating with a corresponding recess or protrusion in the cleaning member 22. Alternatively, as in the embodiment illustrated here (see Fig.1), longitudinal guide posts 22a,b may be arranged inside the filter screen 21 fitting into corresponding throughbores or recesses in the cleaning member 22. The outside surface of guide posts 22a,b thus make up the axial guide face along which the cleaning member 22 can slide axially (i.e., up and down in the orientation as shown and along the longitudinal axis of the lead screw 23), but which prevents the cleaning member 22 from rotation about the longitudinal axis.

The drive motor 26 may preferably be arranged at an outside of the housing 10. A sealed feed-through for the shaft connecting the motor 26 and the lead screw 23 can ensure that the housing remains fluid-tight.

In the illustrated embodiment, the filter screen 21 is elongate with a circular crosssection, and arranged about the cleaning member 22, which in this embodiment is a disc arranged inside the filter screen 21. Other configurations may, however, be possible, for example could the filter screen 21 have a different cross-section shape which is not circular. The cleaning member 22 may, correspondingly, have a non-circular shape.

In the illustrated embodiment, the lead screw 23 is arranged co-axially inside the filter screen 21, and co-axially with the cleaning member 22.

The circular cross-sections and co-axial arrangements of these components may provide an advantageous design for compactness and fluid flow properties, however other configurations may also be possible.

Advantageously, the lead face 41 can be arranged to automatically reverse the movement of the cleaning member 22 when the cleaning member 22 has reached an end position 27 of a pre-determined cleaning stroke. (In the orientation shown in Fig.3, the end position 27 is the lowermost end position.) The automatic reversal can be arranged by the lead face 41 being arranged to lead the cleaning member upwardly again when it reaches the lowermost end position, and to follow an upward-leading path of the lead face 41.

Optionally, the protrusion 42 has a first orientation for moving the cleaning member 22 in a first direction along the lead screw 23 and a second orientation for moving the cleaning member 22 in a second, opposite direction along the lead screw 23. The lead face can be arranged to change the orientation from the first orientation to the second orientation upon the cleaning member 22 reaching the end position 27. The protrusion 42 may, for example, be a follower blade which is rotatable (“turnable”) such that the lead face 41 can change the blade orientation when the cleaning member 22 reaches the end position 27. The follower blade will then follow the lead face 41 upwardly and back towards its uppermost position.

Alternatively, a reversal of the movement of the cleaning member 22 can be effectuated by changing the direction of rotation of the lead screw 23 by means of the motor 26 and/or the transmission between the motor 26 and the lead screw 23.

The protrusion 42 may be arranged in a nut fixed to the cleaning member 22 and arranged about the lead screw 23, wherein the nut cooperates with the lead screw 23 to move the cleaning member 22 in the axial direction of the lead screw 23.

Optionally to having a follower blade or a similar member which engages the helical lead face 41, the nut may have a protrusion in the form of its own helical faces which cooperate with corresponding helical lead face(s) 41 on the lead screw 23.

Advantageously, as illustrated in Figs 1 and 2, the filter screen 21 and the back-wash outlet 24 can be arranged on an insert part 20 which is releasably fixed on the receiver filter housing part 13. The insert part 20 and the receiver filter housing part 13 then together make up the filter housing 10.

Advantageously, for example in seawater media, the lead screw and/or the cleaning member 22 is made at least partly of a polymer material, particularly a polymer plastic. In other media, for example fresh water, another material may be selected as more appropriate.

In use, the filter screen 21 will catch solid particles or other undesirable components which are to be filtered out from the processed fluid. Over time, the filter screen 23 will be clogged by the caught particles, and the performance of the filter 100 will usually decrease as a result of this. By moving the cleaning member 22 along the filter screen 23, the collected particles can be released and removed from the screen 23, thereby reestablishing a good filter performance. The movement of the cleaning member 22 can be combined with opening the back-wash outlet 24 to remove liquids dense with solids or other components released during the cleaning cycle.

During the cleaning cycle, with the back-wash outlet 24 open, fluid flow from the inlet 11, from the outlet 12, or from both the inlet 11 and the outlet 12 can provide a fluid flow to carry the released solids or other particles out via the back-wash outlet 24.

Advantageously, the cleaning cycle may if required be carried out without shutting down the process flow. This can be achieved by flowing the process fluid to the filter via the inlet 11 in the ordinary manner, keeping the outlet 12 open for discharge of cleaned fluid, while opening the back-wash outlet 24 while moving the cleaning member 22 along the filter screen 23. This provides a partial flow of fluid through the back-wash outlet 24 which provides a means for removing the released particles and debris out of the housing 10. When the cleaning cycle is complete, the back-wash channel 24 is closed.

In one method of effectuating the cleaning cycle, the back-wash outlet 24 may be opened with the cleaning member 22 in its uppermost position (see Fig.3), and be kept open for a given period of time before the cleaning member 22 is moved downwards. This may allow larger particles to flow directly from the inlet side 25 and out the backwash outlet 24 before the cleaning member 22 moves downwards, in order that such particles do not have to pass the gap between the cleaning member 22 and the filter screen 21 when the cleaning member 22 has passed the back-wash outlet 24 (i.e. when it is moving downwards in the orientation shown in Fig.3).

Pressure sensors 10a and 10b may be arranged at the filter housing 10 to identify when the filter is becoming clogged by measuring pressure difference, for example by providing one pressure sensor 10b at the inlet 11 and one pressure sensor 10a at a lower part of the housing 10 and mounted into the outlet side 31.

It will be understood that, although only the functionality of the filter 100 itself has been described here, appropriate valves will be arranged in the overall fluid processing system to provide the desired flow directions. This includes valves controlling the flow through the inlet 11, outlet 12 and back-wash outlet 24.

The cleaning member 22 may be arranged to be in contact with the filter screen 21 during movement along the lead screw 23 for the purpose of cleaning the filter screen 21. For example, the cleaning member 22 may comprise brushes or equivalent means for mechanically cleaning the screen 21.

The cleaning member 22 may be arranged to move adjacent but spaced from the filter screen 21 during movement along the lead screw 23. Cleaning of the filter screen 21 can then be effectuated by means of the cleaning member 22 creating pressure differences and local fluid flow conditions in the vicinity of the screen surface which releases or removes solids or other components which may have accumulated on the screen 21. The released solids or components may then be transported away with the fluid flow exiting the back-wash outlet 24.

The cleaning member 22 may be movable along the whole length of the filter screen 21, or alternatively only along a part of the full length of the filter screen 21. For example, in the embodiment illustrated in Figs 1-3, the regular flow conditions near the inlet 11 may be such that little solids or other components accumulate on the screen 21 in that area, such that cleaning in this part is less necessary.

In an embodiment, illustrated in Fig.5, the cleaning member 22 may comprise inlets or outlets 51 for a cleaning fluid stream. As can be seen from Fig.5, the inlets or outlets 51 can be provided as radial outlets in a disc-shaped cleaning member 22. The inlets or outlets 51 can be provided with a fluid connection 52 fluidly connected to the inlets or outlets 51.

The fluid connection 52 can be connected to a fluid pump (or equivalent pressure supply source having a pressure higher or lower than that of the inlet side 25) such as to provide a fluid flow through the inlets or outlets 51, either by pumping fluid via the fluid connection 52 and out through outlets 51 or by pumping fluid from the fluid connection 52 such as to create suction and fluid flow into the inlets 51 from the inlet side 25.

Advantageously, the fluid connection 52 is provided as a flexible, spiral-shaped pipe arranged about the lead screw 23. It may lead through the housing 10 and to a pump (or equivalent) arranged on the outside of the housing 10, or it may be connected to a pump or pressure source inside the housing 10.

The embodiment in Fig.5 may thus provide further enhanced cleaning effect for the filter by providing an enhanced fluid flow field as the cleaning member 22 moves along the filter screen 21. Advantageously, the embodiment in Fig.5 is provided with suction through inlets 51 such that particles or dirt is withdrawn out of the inlet side via the inlets 51. The fluid connection 52 may, for example, discharge to the back-wash outlet 24. The pressure source for driving the fluid flow through the inlets 51 may also be the backwash outlet 24 or a back-wash pipe connected thereto, if the pressure in that part is sufficiently low to produce a fluid flow through the fluid connection 52 and inlets 51.

The fluid inlets or outlets 51 may be directed such as to produce a fluid flow substantially perpendicular to the longitudinal axis of the lead screw 23. Alternatively, the fluid inlets or outlets 51 may be directed such as to produce a fluid flow which is angled and not perpendicular to the longitudinal axis of the lead screw, such as an upward-directed or downward-directed fluid flow. This may enhance the cleaning effect.

Embodiments as described herein thus provide a system and method suitable for automatic or semi-automatic cleaning of a filter system for cleaning of dirt particles generated on the filter insert without opening the filter. Pressure differences and/or mechanical cleaning during the cleaning cycle will cause particles accumulated at the filter screen to be removed and dumped through at least one separate back-wash pipe caused by temporarily opening of at least one back-wash valve.

A cleaning cycle can be arranged to start automatically as a function of a measured pressure difference between the sensors 10a,b. Such change in pressure can indicate a clogged filter screen, whereby in response a cleaning cycle can be initiated. The backwash outlet 24 and back-wash valve can be connected to a dumping line to let particles and debris from the filter screen escape.

Advantageously, embodiments as described herein can allow the filter to be designed smaller and more location friendly without losing effect.

A corresponding computer with software for process control can be utilised for controlling the various valves and other process components, as well as controlling the start of the cleaning cycle.

Advantageously, by providing an effective and accurate cleaning method, a higher overall operational efficiency of the filter can be obtained, for example in view of reduced pressure losses and reduced energy usage during the cleaning process.

Advantageously, the cleaning member 22 is a disc connected to a self-reversing helical screw by a follower blade in a nut, enabling the disc to move up and down along the filter surface causing the dirty liquid to be sucked through the back-wash outlet by the opening of the back-wash valve and thereby causing the passage of the dirty liquid only through the back wash outlet by the opening of the back wash valve.

The motor 26 may, for example, be an electric, pneumatic or hydraulic motor enabling the rotation of the lead screw 23.

The filter screen 21 may be a cylindrical screen wherein the inlet side 25 is defined on the inside of the screen 21 and the outlet side 31 is defined on the outside of the screen 21.

Advantageously, according to embodiments as described herein, the required service space can be reduced due to the compact design of the filter 100. This makes it easier to install the filter 100 at narrow places, for example onboard a ship or other limited spaces.

The lead screw 23 and/or the nut mechanism on the disc / cleaning member 22 can preferable be constructed of thermoplastic materials which are less susceptible to corrosion in water and have higher resistance to chemicals. This can replace expensive materials like titan and duplex stainless steel, while being able to withstand operation in corrosive fluids.

Optionally, if required the filter screen 21 and/or the lead screw 23 and/or the nut mechanism on the disc / cleaning member 22 can be made of a metal, for example if the filter 100 is required to handle high-temperature fluids.

Advantageously, according to embodiments described herein, the cleaning process can be accurately controlled due to the possibility of precise rotation control by the motor 26, for example using an electrical drive.

The principles and embodiments described herein may be suitable for use with various types of filters, for example Bernoulli-type filters, filters employing vacuum suction of the filter inserts and filters using brushes to clean the filter insert.

The invention is not limited by the embodiments described above; reference should be had to the appended claims.

Claims

1. A filter (100) having:

a filter housing (10) having a fluid inlet (11) and a fluid outlet (12);

an elongate filter screen (21) arranged in the filter housing (10) between the fluid inlet (11) and the fluid outlet (12);

a cleaning member (22) movable relative to and adjacent the filter screen (21); and

a back-wash outlet (24) arranged at an inlet side (25) of the filter screen (21); wherein the cleaning member (22) is movable axially along a lead screw (23) arranged in the filter housing (10) by means of rotation of the lead screw (23) by a drive motor (26), characterized in that

the filter screen (21) has a circular cross-section and the cleaning member (22) is a disc arranged inside the filter screen (21), the cleaning member (22) being arranged to move adjacent but spaced from the filter screen (21) during movement along the lead screw (23).

2. A filter (100) according to the preceding claim, wherein the filter screen (21) and the back wash outlet (24) is arranged on an insert part (20) which is releasably fixed on a receiver filter housing part (13), the insert part (20) and the receiver filter housing part (13) together making up the filter housing (10).

3. A filter (100) according to any preceding claim, wherein the filter screen (21) is elongate and arranged about the cleaning member (22).

4. A filter (100) according to the preceding claim, wherein the lead screw (23) is arranged co-axially inside the filter screen (21).

5. A filter (100) according to any preceding claim, wherein the lead screw (23) has a helical lead face (41) operable to engage a follower protrusion (42) arranged on the cleaning member (22) and move the cleaning member (22) axially along the lead screw (23).

6. A filter (100) according to the preceding claim, wherein the lead face (41) is arranged to reverse the movement of the cleaning member (22) when the cleaning member (22) has reached an end position (27) of a pre-determined cleaning stroke.

7. A filter (100) according to the preceding claim, wherein the follower protrusion (42) has a first orientation for moving the cleaning member (22) in a first direction along the lead screw (23) and a second orientation for moving the cleaning member (22) in a second, opposite direction along the lead screw (23), and whereby the lead face is arranged to change the orientation from the first orientation to the second orientation upon the cleaning member (22) reaching the end position (27).

8. A filter (100) according to any preceding claim, wherein the lead screw is made at least partly of a polymer material.

9. A filter (100) according to any preceding claim, wherein the cleaning member (22) comprises a plurality of fluid inlets or outlets (51) connected to a pressure source via a fluid connection (52).

10. A filter (100) according to the preceding claim, wherein the fluid inlets or outlets (51) are distributed around a peripheral part of the cleaning member (22).

11. A filter (100) according to any of the two preceding claims, wherein the fluid connection (52) is a flexible pipe arranged helically about the lead screw (23).

12. A filter (100) according to any preceding claim, wherein the cleaning member (22) is made at least partly of a polymer material.

13. A filter (100) according to claim 8 or 12, wherein the polymer material is a polymer plastic.