WO2017216316A1

WO2017216316A1 - A scanning device for filter leakage detection

Info

Publication number: WO2017216316A1
Application number: PCT/EP2017/064719
Authority: WO
Inventors: Hampus ISACSSON
Original assignee: Camfil Ab
Priority date: 2016-06-15
Filing date: 2017-06-15
Publication date: 2017-12-21
Also published as: CN207622931U; CN107525629B; CN107525629A

Abstract

There is provided a scanning device 100 for filter leakage detection, the scanning device comprising at least one scanning arrangement 131a, 131b arranged for scanning a respective filter 122a, 122b. Each scanning arrangement comprises a scan probe 132a, 132b covering the full width of its respective filter surface, and a movement mechanism 133a, 133b which each is operable to displace the scan probe in a direction perpendicular to the scan probe over the filter. The scanning device comprises an elongated rotatable actuator 134 arranged extending in parallel to the scan probe. Each movement mechanism is coupled to the actuator. Thereby a controlled manner of scanning several adjacently arranged filters, particularly in a side access cabinet that is more than one filter deep, from a side access position is provided.

Description

A SCANNING DEVICE FOR FILTER LEAKAGE DETECTION

FIELD OF THE INVENTION

The present invention relates to a scanning device and a movement mechanism for filter leakage detection.

BACKGROUND OF THE INVENTION

In air ventilation systems requiring high efficiency filters such as High- Efficiency Particulate Air (HEPA) filters and other high efficiency filters, it is known to use filter housings in which filter units are secured and effectively mechanically clamped to seal the respective filter units within the filter housing. When utilizing such mechanical clamping mechanisms to seal high efficiency filters, it is a requisite to ensure that any bypass or leakage around the seal is less than the maximum penetration of the filter. It is also a requisite to ensure that the complete filter surface is free from any pinhole leaks or other defects. Techniques for this is described in e.g. ISO 14644-3 section B.6. Similar and even more demanding tests are also prescribed in national standards e.g. in Chinese standards for Bio-safe Exhaust HEPA filtration facilities. Testing may be made either as a single point average after the filter or by scanning close to the filter surface. The former approach demands a sampling to be made more than 20 duct diameters after the filter to ensure that the single sample is completely mixed and the latter, while being preferred and much more accurate, demands access close to the filter surface and the surrounding gaskets. The latter procedure of scanning close to the surface is furthermore virtually impossible if the fan is placed after the filter thus creating a sub pressure. Any access to the filter area will open a passage of air into the duct and decrease or even entirely remove the flow through the filer making the test impossible. A system to allow such scanning is therefore addressed by this invention.

Filter housings with filter frame assemblies and clamping mechanisms as described above are typically used in critical filtration applications like for instance nuclear, pharmaceutical and risk laboratories. Very high safety standards complying with for instance increasingly stringent requirements from bio-safety authorities are thus applied. Periodic retesting or even replacement of the filters is required to meet regulatory demands, and may involve the replacement of a large number of filters on a regular bases. A potential problem with the clamping mechanism of the above type and others is that any mistake made during replacement of the filters in the air ventilation system, e.g. if the filters are not properly positioned, the gasket is not fully functioning, the clamping mechanism are not properly closed etc., could cause leakage of hazardous substances to the surroundings. I addition the filter surface is for some types of HEPA filters very delicate and may be damaged even by a light touch.

For the reasons above it is in some applications a compulsory demand to check that a mounted filter within the filter housing is leak free and conforms to the filtration class. This is done by including a scan probe, by means of which air is collected downstream of the filter and analyzed with respect to the undesired substance, as a part of the filter housing. The scan probe, having an air intake and providing air samples to an analyzer, is moved in a controlled manner at a defined distance close to the filter surface in order to secure a sample from a very small area of the filter at the time. It is a demand to probe a very small area if a leak should be possible to spot as an increase of concentration by the analyzer. Therefore it is desirable to have the probe mounted as close as possible to the filter surface without causing an obstruction of the air flow reaching the probe from the filter.

Different concepts of test probes which are moved to scan the filter area have been developed. One kind thereof is an elongated test probe, which extends along the length or width of the filter and is moved back and forth perpendicularly of its longitudinal extension to scan the area in the vicinity of the filter surface by means of some hand or motor driven

mechanism like a cylinder, a power screw etc. A typical elongated test probe is made of a tube with several inlet holes through the tube wall distributed along the length of the test probe, and a central outlet. SUMMARY OF THE INVENTION

It would be advantageous to provide an alternative and improved scanning device and movement mechanism for a scanning device which is robust and cost effective, and which is easily replaced and mounted. Further, it would be advantageous to provide a scanning device which is suitable for filter housings with a plurality of filter units.

To better address this concern, in a first aspect of the invention there is presented a scanning device for filter leakage detection of at least one filter, the scanning device comprising at least one scanning arrangement arranged for scanning a respective filter. Each scanning arrangement comprises a scan probe covering the full width of its respective filter surface, and a movement mechanism which is operable to displace the scan probe in a direction perpendicular to the scan probe over the filter. The scanning device comprises at least one elongated rotatable actuator arranged extending in parallel to the scan probe. Each movement mechanism is coupled to the actuator. If desired a rotatable set of concentrically arranged actuators, e.g. a telescopic actuator, or a set of coupled adjacent actuators arranged along the same longitudinal axis, may be used even if a single rotatable actuator simplifies the construction and is therefore preferred.

The scanning device is advantageously arranged to be able to in a controlled manner scan several adjacently arranged filters, particularly in a side access cabinet that is more than one filter deep, from a side access position. Since each scan probe covers a full width (or length) of each filter unit, preferably including its sealing sections, advantageously the total filter surface area of the filter housing may be scanned in a single sweep. Further, by providing a movement in a perpendicular direction with respect to the longitudinal extension of the scan probes over a moving range, preferably selected to coincide with the height of the filter units, scanning of mixed sized filters with the same scanning speed is provided. As an example, side access cabinets containing one 610 x 610 (mm) (height x width) sized filter unit and one 610 x 305 (mm) sized filter unit will experience the same scanning speed/time for both filter units since the scanning is performed along the same distance, e.g. between the top and bottom of each filter unit. The functionality of the actuator is to provide mechanically linked scan probe movements, controlling a plurality of scanning arrangements with the same actuator. Note that the direction of movement of the scanning probes may alternatively be in a depth direction, i.e. when the filter units are arranged in a ceiling arrangement and the filter units are thus horizontally arranged.

According to an embodiment of the scanning device, the movement mechanism comprises a drive wheel, such as e.g. a pulley, crank shaft, cog wheel, which is connected to the actuator, and a drive element which is driven by the drive wheel.

According to an embodiment of the scanning device, the movement mechanism further comprises a guiding rail arranged for guiding the movement of the scan probe, which is advantageous. By providing a guiding rail for the movement of the scan probe, the tolerance of the movement of the drive element itself is increased without compromising the scanning of the scan probe.

According to an embodiment of the scanning device, the movement mechanism further comprises a sled arranged for moving along the guiding rail, and onto which sled the scan probe is fixated or releasably attached.

The guiding rail and sled advantageously provides lateral stability of the scan probe as it is moved. The guiding rail advantageously provides a fixed predetermined distance between the scan probe and the filter surface.

According to an embodiment of the scanning device, the drive element is arranged extending between an upper- and a lower end position, preferably arranged at a top and a bottom, respectively, of the filter. The scan probe may be attached directly onto the drive element.

According to an embodiment of the scanning device, the gear of the drive wheel is selected to provide a preselected scanning speed. The scanning speed may be selected to provide a preselected scanning speed per one revolution of the actuator. Advantageously, the drive wheel may be exchangeable, and different scanning speeds can be selected, e.g. by changing the drive wheel diameter to provide different gearing of the drive wheel. In a preferred embodiment of the invention, the gear of the drive wheel is selected to provide a scanning speed of 5 cm/s per one revolution of the actuator, which meets the requirement of standard ISO 14644-3 section B.6. The gear ratio of the scan probe movement in a direction perpendicular to the scan probe versus the number of revelations (rpm) by the actuator (e.g. when driven by a crank or a motor) may be selected by connecting a drive wheel in the form of a cogwheel to the actuator (drive shaft) with a preselected number of cogs. This advantageously makes the scanning device easily adoptable to different testing standards advising different linear probe scanning speeds.

According to an embodiment of the scanning device, the drive element is one of a cog belt, a chain, a flat belt, and a string. When the drive element is a cog belt and a drive wheel being a cogwheel a controlled movement of the scan probe is provided, which in turn allows the position of the scan probe to advantageously be calculated by means of a revelation to position calculation.

According to an embodiment of the scanning device, the drive element comprises a reinforced cord, in particular a cord reinforced with steel or Kevlar which improves the mechanical stability of the drive element, e.g. hinders a drive element to stretch over time, thus making a tension

mechanism redundant.

According to an embodiment of the scanning device, the actuator is a drive shaft rotated by means of a crank handle, a motor, a motor device controlled by a scanning equipment (which may comprise a computer, an analyser, and valves), or some other applicable rotating mechanism. This provides an easy to handle system, without having to use long movement rods etc. extending from the filter unit cabinet when the scanning procedure is performed.

According to an embodiment of the scanning device, a range of motion of the scan probe is defined by a first and a second end position, i.e. the scan probe may be moved in a direction perpendicular to its longitudinal extension between the first and second end position, and the actuator is arranged within the range of motion, i.e. the actuator is arranged in parallel to the longitudinal extension of the scan probe, but within the scanning area of the filters thus providing side access of the actuator with respect to the filter housing.

According to an embodiment of the scanning device, at least one scan probe is one of a set of probes seamlessly covering the full length of each filter surface and sealing sections, a multi chamber probe, a tube with several inlet holes through the tube wall distributed along the length of the test probe, and a V-filter scan probe.

According to an embodiment of the scanning device, the actuator comprises a set of concentrically arranged actuators, e.g. a telescopic actuator, or a set of coupled adjacent actuators arranged along the same longitudinal axis

According to an aspect of the inventive concept there is provided a scanning arrangement for filter leakage detection comprising an elongated rotatable actuator, and at least one movement mechanism which is operable to displace a respective elongated scan probe covering the full width of its respective filter surface in a direction perpendicular to the longitudinal direction of the scan probe over the respective filter, and which is connected to the elongated rotatable actuator, which is arranged extending in parallel to the scan probe longitudinal direction. If desired the actuator is a set of rotatable concentrically arranged actuators , e.g. a telescopic actuator, or a set of coupled adjacent actuators arranged along the same longitudinal axis. However, utilising a single rotatable actuator simplifies the construction and is therefore preferred. Different embodiments and advantages of the scanning arrangement are described above with reference to embodiments of the scanning device of the present inventive concept in which such scanning arrangement is employed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail and with reference to the appended drawings in which:

Figs. 1 a and 1 b, are perspective views schematically illustrating a filter housing comprising an embodiment of a scanning device according to the present inventive concept; Fig. 2a and 2b show an exploded perspective view and a perspective view, respectively, of an embodiment of a movement mechanism according to the present inventive concept; and

Figs. 3 - 5 are perspective views illustrating embodiments of the present inventive concept.

DESCRIPTION OF EMBODIMENTS

Referring now to Fig. 1 a and Fig. 1 b, a filter assembly 100 for air filter units comprises a filter housing 1 10 adapted to be mounted in an air ventilation system. The filter housing 1 10 comprises a cabinet 1 1 1 having an upstream air entrance opening 1 15 defined by an air entrance opening frame 1 16, a downstream air exit opening 1 13 defined by an air exit opening frame 1 14, see Fig. 1 b, and located at the air entrance opening 1 15, opposite side walls 1 17, 1 18, which with the spatial orientation shown in Fig. 1 b can be called first and second side walls 1 17, 1 18, and opposite top wall 1 19 and bottom wall 120 extending between and attached with the air entrance opening frame 1 16 and the air exit opening frame 1 14. A door 1 12 is arranged at the first side wall 1 17. The door 1 12 seals the first side wall 1 17 when the door 1 12 is closed.

The top and bottom walls could serve as side walls as well, with a different mounting of the filter housing 1 10 in the air ventilation system.

Therefore, in this application, the spatial references are related to the air stream through the filter housing, i.e. the upstream and downstream references. The first and second side walls 1 17, 1 18 extend between the air entrance opening frame 1 16 and the air exit opening frame 1 14, as well as between the top wall 1 19 and the front opening frame 1 16, with which they are connected.

The door 1 12 is arranged to selectively seal a filter access port 121 configured to facilitate mounting (and removal) of filter units 122a, 122b, which are shown in a mounted state in Fig. 1 b, into the filter housing 1 10. Mounting includes receiving and clamping the filter units to sealingly engage with a face (e.g. on a flange) of the air entrance opening frame 1 16 (not shown in detail). The door 1 12 is coupled to the cabinet 1 1 1 by hinges 123. The door includes a seal (not visible) that engages a face of the first side wall 1 17 when the door 1 12 is in a closed position, thus sealing the filter access port.

Referring now to Fig. 1 b, an embodiment of a scanning device 130 according to the present invention is disposed downstream of the filter units 122a, 122b in the inner volume of the cabinet 1 1 1 . (A cover with an exhaust sealingly engaged with the exit opening frame 1 14 is left out in the figures for sake of simplicity.) The scanning device 130 is configured having two separate scanning arrangements 131 a, 131 b, each positioned at a respective filter unit 122a, 122b. This arrangement makes it possible to reach close to each of the filters frame and surface in order to achieve the desired special (spatial) resolution of leak detection. Each scanning arrangement has an elongated scan probe 132a, 132b, and an associated movement mechanism 133a, 133b which is operable to displace its respective scan probe 132a and 132b in a direction perpendicular to the longitudinal extension of the scan probe 132a, 132b between two end positions, marked A and B in the Fig. 1 b, at a top and a bottom, respectively, of their respective filter units 122a, 122b. Since each scan probe 132a, 132b of the scanning arrangements 131 a, 131 b covers the full distance necessary to scan its respective filter unit 122a, 122b, i.e. the width of the filter unit area plus optionally the sealing area thereof, movement in only one direction perpendicular to the scan probe 132a, 132b is required to cover sanning of the whole filter surface. The range of movement in the direction perpendicular to the scan probes 132a, 132b is defined by the first end position A at the top wall 1 19 and the second end position B at the bottom wall 120 of the housing, or alternatively the range of movement may be defined as the distance between an upper- and a lower end position arranged at a top and a bottom, respectively, of the filter area.

Each respective movement mechanism 133a, 133b extends perpendicularly to the longitudinal extension of the scan probes between the inner surfaces of the top wall 1 19 and bottom wall 120. An embodiment of a movement mechanism will be explained in further detail below with reference to Fig. 2. Referring still to Fig. 1 a and 1 b, an elongated and rotatable actuator (or a set of actuators) is arranged extending in a direction parallel to the scan probes 132a, 132b within the filter housing 1 1 1 , and here the movement mechanisms 133a and 133b are coupled to the same actuator 134. If desired a set of concentrically arranged rotatable actuators may be used even if a single rotatable actuator simplifies the construction and is therefore preferred. The actuator 134 is further connected, via an air sealed penetration 140 arranged in the first side wall 1 17, to a rotation mechanism, which here is a crank 135 which is operable from outside of the cabinet 1 1 1 . Other applicable rotatable driving means to rotate the actuator includes e.g. a motor, or a motor device controlled by a scanning equipment.

According to an embodiment of the inventive concept the actuator is arranged/positioned within an area covered by the range of motion of the scan probe(s), i.e. positioned between the first and second end positions A, B.

With reference now to Fig. 2a, a scanning arrangement 131 , according to an embodiment of the invention, comprises a movement mechanism 133 which comprises a drive wheel 135 which is arranged to receive and engage with the actuator 134 (not shown in Fig. 2), such that when the actuator 134 is rotated, the drive wheel 135 rotates. A drive element 136 is suspended between a first and a second end wheel 137, 138. The first and second end wheels may be cog wheels or free wheels. The first end wheel 137 is arranged in a suspension support element 139 which is fixated to a first end portion 157 of a support rail 154. The suspension support element 139 is arranged for being fixated with applicable fastening means, e.g. screws, rivets, quick connectors etc. (not shown) at the top wall 1 19 inside the housing 1 1 1 . A corresponding arrangement is provided for the second end wheel 138, which is arranged in a suspension support element 140 which is fixated to a second end portion 158 of the support rail 154. The suspension support element 140 is further arranged for being fixated with applicable fastening means, e.g. screws, rivets, quick connectors etc. (not shown) at the bottom wall 120 inside the housing 1 1 1 . The drive element 136 is perpendicularly arranged with respect to the actuator and the scan probe 132. The drive element 136 is further engaged with the drive wheel 135, which rotates as the actuator is rotated and thus drives the drive element 136. The guiding rail 154 is here an elongated metal profile with a first side 155 and a second side 156 and the opposite first and second end portions 157, 158. To stabilize the drive wheel 135 and limit the lateral movement of the drive element 136, a support structure 143 which is basically U-shaped with supporting flanges keeping the drive element in place, and providing a base for mounting the drive wheel 135, and optionally mounting of guiding wheels 142. The support structure 143 is attached to the second side 156 of the guiding rail 154, and the drive element 136 is suspended circumferentially about the guiding rail 154 in its longitudinal direction, see Fig. 2b, which illustrates how the end wheels 137, 138 and the guiding rail 154 provides a guiding track 144 for the drive element 136, which is further engaged with the drive wheel 135, via the guiding wheels 142. A sled 141 is attached to the driving element 136 on a portion of the driving element which is arranged on the first side 155 of the guiding rail 154. The sled 141 and the guiding rail 154 are provided with complementary tracks 160, 161 (mutullay receiving) such that the sled 141 follows the guiding rail 154 as the drive element 136 is put in motion by the actuator/drive wheel 134/135. Alternatively, the scan probe 132 may be attached directly on the drive element.

According to an embodiment, the drive wheel 135 is a cog wheel and the drive element 136 is a cog belt. In this exemplifying embodiment the actuator is a circular profile drive shaft which is received by and engages with the cogwheel 135, such that when the actuator is rotated the cog wheel drives the cog belt 136. Other shapes of the actuator profile are applicable, e.g. square, cogged etc.. As illustrated in Fig. 2b, the scan probe 132 is connected to the sled 141 which is arranged on the guiding rail 154. The sled 141 carries the scan probe 132. The drive element, cog belt 136, is further suspended around the upper and the lower end position cogwheel, 137 and 138, which are arranged having a predefined diameter. The diameter of the upper and lower end position cogwheel 137, 138 is selected to enable the probe sled to move to the extreme top end and bottom end of the filter, thus enabling scanning of the entire filter surface in one scan cycle.

The cog belt may be reinforced by a steel or Kevlar cord to hinder the cog belt to stretch over time, thus making a tension mechanism redundant.

The scanning device according to the present invention is suitable to implement using quick connectors to make the device easily detached and remounted e.g. if service is needed or to be retrofitted into an existing filter unit cabinet.

According to an embodiment of the invention, the gear of the drive wheel is selected to provide a preselected scanning speed. In an embodiment of the scanning device, the actuator is a crank shaft and the gear of the drive wheel and the crank is selected to provide a scan speed of 5 cm/s. For a typical filter unit size of 60 cm in height, the scanning takes 12 s and the crank has to be revolved 12 times.

With reference now to Fig. 3 a scanning device 230 according to the invention is arranged in a filter house 200 with a cabinet 21 1 arranged for fitting three adjacently arranged filter units (not present in the Figure). The scanning device 230 has a similar arrangement as described above for the embodiment shown in Fig. 1 but it here comprises three adjacently arranged movement mechanisms 231 a, 231 b, and 231 c which all are engaged with a common actuator 234 which extends in parallel with the scan probes 132a, 132b, 132c of each movement mechanism. Each scan probe 132a, 132b, 132c is here adapted to scan a filter unit of the same width and height. In an alternative embodiment, adjacently arranged scan probes are adapted to scan filter units of different width but with the same height.

Figs. 4 and 5 show yet two embodiment of a scanning device 330 and 430 according to the invention when arranged in a filter house 300 and 400 with a cabinet 31 1 and 41 1 , respectively, arranged for fitting four adjacently arranged filter units and one single filter unit, respectively.

In the scanning device 330 shown in Fig. 4, four movement

mechanisms 331 a, 331 b, 331 c, 331 d are positioned at a respective filter unit (not present in the Figure). Two actuators 334a and 334b extend in parallel with the scan probes 332a, 332b, 332c, 332d of each respective movement mechanism 331 a, 331 b, 331 c, 331d. Crank handles 335a and 335b are arranged at an outer side of the housing 31 1 , and are thus made accessible for activating scanning of filter units when mounted in the filter housing). Each scan probe 332a, 332b, 332c is here adapted to scan a filter unit of the same width and height. In an alternative embodiment, adjacently arranged scan probes are adapted to scan filter units of different width but with the same height.

Furthermore, it would be understood by the person skilled in the art what features of the different embodiments can be combined although not explicitly written above.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1 . A scanning device for filter leakage detection of at least one filter, the scanning device comprising at least one scanning arrangement arranged for scanning a respective filter,

each scanning arrangement comprising:

a scan probe covering the full width of its respective filter surface; and

a movement mechanism which is operable to displace the scan probe in a direction perpendicular to the scan probe over the filter, said scanning device comprising at least one elongated rotatable actuator for activating said movement mechanism arranged extending in parallel to the scan probe, and wherein each movement mechanism is coupled to said actuator.

2. A scanning device according to claim 1 , wherein said movement mechanism comprises a drive wheel which is connected to said actuator, and a drive element driven by said drive wheel.

3. A scanning device according to claim 1 or claim 2, wherein said movement mechanism further comprises a guiding rail arranged for guiding the movement of the scan probe.

4. A scanning device according to claim 3, wherein said movement mechanism further comprises a sled arranged for moving along said guiding rail, and onto which sled said scan probe is attached.

5. A scanning device according to any of claim 2 to claim 4, wherein said drive element is arranged extending between an upper- and a lower end position arranged at a top and a bottom, respectively, of said filter.

6. A scanning device according to any of claim 2 to claim 5, wherein the gear of the drive wheel is selected to provide a preselected scanning speed.

7. A scanning device according to any of claim 2 to claim 6, wherein said drive element is one of a cog belt, a chain, a flat belt, and a string.

8. A scanning device according to any of claim 2 to claim 7, wherein said drive element comprises a reinforced cord, in particular a cord of steel or Kevlar.

9. A scanning device according to any preceding claim, wherein said actuator is a drive shaft rotated by means of a crank handle, a motor, a motor device controlled by a scanning equipment.

10. A scanning device according to any preceding claim, wherein a range of motion of said scan probe is defined by a first and a second end position, and wherein said actuator is arranged within said range of motion.

1 1 . A scanning device according to any preceding claim, wherein at least one scan probe is one of a set of probes seamlessly covering the full length of each filter surface and sealing sections, a multi chamber probe, a tube with several inlet holes through the tube wall distributed along the length of the test probe, and a V-filter scan probe.

12. A scanning device according to any preceding claim, wherein said actuator comprises a set of concentrically arranged actuators, a telescopic actuator, or a set of coupled adjacent actuators arranged along the same longitudinal axis.

13. A scanning arrangement for filter leakage detection of at least one filter comprising:

an elongated rotatable actuator; and

at least one movement mechanism which is operable to displace a respective elongated scan probe covering the full width of a respective filter surface in a direction perpendicular to longitudinal direction of the scan probe over the respective filter; and which is connected to and activated by said elongated rotatable actuator, which is arranged extending in parallel to the scan probe longitudinal direction.

14. A filter housing comprising a scanning device according to any of claim 1 to claim 12 or a scanning arrangement according to claim 13.