U.S. patent application number 12/984145 was filed with the patent office on 2011-04-28 for filter with memory, communication and pressure sensor.
This patent application is currently assigned to MILLIPORE CORPORATION. Invention is credited to Anthony DiLeo, John Dana Hubbard.
Application Number | 20110094951 12/984145 |
Document ID | / |
Family ID | 38326949 |
Filed Date | 2011-04-28 |
United States Patent
Application |
20110094951 |
Kind Code |
A1 |
DiLeo; Anthony ; et
al. |
April 28, 2011 |
FILTER WITH MEMORY, COMMUNICATION AND PRESSURE SENSOR
Abstract
The present invention describes a system and method for
accurately measuring the pressure within a filter housing. A
pressure sensor and a communications device are coupled so as to be
able to measure and transmit the pressure within the filter housing
while in use. This system can comprise a single component,
integrating both the communication device and the pressure sensor.
Alternatively, the system can comprise separate sensor and
transmitter components, in communication with one another. In yet
another embodiment, a storage element can be added to the system,
thereby allowing the device to store a set of pressure values. The
use of this device is beneficial to many applications. For example,
the ability to read pressure values in situ allows integrity tests
to be performed without additional equipment. In addition,
integrity testing for individual filters within multi-filter
configurations is possible.
Inventors: |
DiLeo; Anthony; (Westford,
MA) ; Hubbard; John Dana; (Billerica, MA) |
Assignee: |
MILLIPORE CORPORATION
Billerica
MA
|
Family ID: |
38326949 |
Appl. No.: |
12/984145 |
Filed: |
January 4, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11402438 |
Apr 12, 2006 |
|
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12984145 |
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Current U.S.
Class: |
210/87 ;
210/90 |
Current CPC
Class: |
B01D 2201/291 20130101;
B01D 65/104 20130101; B01D 35/143 20130101; B01D 2313/44 20130101;
B01D 2201/56 20130101; B01D 2201/52 20130101; B01D 61/22 20130101;
B01D 2311/14 20130101; B01D 61/147 20130101; B01D 65/102
20130101 |
Class at
Publication: |
210/87 ;
210/90 |
International
Class: |
B01D 35/14 20060101
B01D035/14; B01D 35/143 20060101 B01D035/143 |
Claims
1. An apparatus for monitoring the pressure within a filter housing
having at least one filtering element, comprising: said filtering
element, a pressure sensor embedded in said filtering element, and
a transmitter, in communication with said sensor.
2. The apparatus of claim 1, further comprising a storage element
adapted to store measurements from said sensor.
3. The apparatus of claim 1, wherein said sensor is selected from
the group consisting of a MEMS device, a piezoelectric device, a
conductive polymer device, an elastomer device, and an ink
device.
4. The apparatus of claim 1, wherein said transmitter utilizes
wireless communication.
5. The apparatus of claim 4, wherein said wireless transmitter
comprises an RFID tag.
6. The apparatus of claim 1, wherein said pressure sensor and said
transmitter are provided in a single enclosure.
7. The apparatus of claim 4, further comprising a wireless
receiver, adapted to receive signals transmitted from said wireless
transmitter.
8. The apparatus of claim 1, wherein said pressure sensor comprises
a differential pressure sensor.
9. A Tangential Flow Filtration (TFF) device comprising at least
one connecting port; a filtering element and at least one sensor
located in at least one of said at least one connecting port.
10. The device of claim 9, wherein said sensor comprises a pressure
sensor.
11. The device of claim 9, wherein said sensor comprises a flow
rate sensor.
12. A Tangential Flow Filtration (TFF) device comprising a
plurality of modules and at least one pressure sensor located
between adjacent ones of said plurality of modules.
13. The device of claim 12, further comprising at least one
additional pressure sensor within a membrane stack in one of said
plurality of modules.
14. The device of claim 12, further comprising a transmitter in
communication with said pressure sensor.
Description
[0001] This application is a divisional application of U.S. patent
application Ser. No. 11/402,438, filed Apr. 12, 2006, the
disclosure of which are incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] The use of RFID tags has become prevalent, especially in the
management of assets, particularly those applications associated
with inventory management. For example, the use of RFID tags
permits the monitoring of the production line and the movement of
assets or components through the supply chain.
[0003] To further illustrate this concept, a manufacturing entity
may adhere RFID tags to components as they enter the production
facility. These components are then inserted into the production
flow, forming sub-assemblies in combination with other components,
and finally resulting in a finished product. The use of RFID tags
allows the personnel within the manufacturing entity to track the
movement of the specific component throughout the manufacturing
process. It also allows the entity to be able to identify the
specific components that comprise any particular assembly or
finished product.
[0004] In addition, the use of RFID tags has also been advocated
within the drug and pharmaceutical industries. In February 2004,
the United States Federal and Drug Administration issued a report
advocating the use of RFID tags to label and monitor drugs. This is
an attempt to provide pedigree and to limit the infiltration of
counterfeit prescription drugs into the market and to
consumers.
[0005] Since their introduction, RFID tags have been used in many
applications, such as to identify and provide information for
process control in filter products. U.S. Pat. No. 5,674,381, issued
to Den Dekker in 1997, discloses the use of "electronic labels" in
conjunction with filtering apparatus and replaceable filter
assemblies. Specifically, the patent discloses a filter having an
electronic label that has a read/write memory and an associated
filtering apparatus that has readout means responsive to the label.
The electronic label is adapted to count and store the actual
operating hours of the replaceable filter. The filtering apparatus
is adapted to allow use or refusal of the filter, based on this
real-time number. The patent also discloses that the electronic
label can be used to store identification information about the
replaceable filter.
[0006] A patent application by Baker et al, published in 2005 as
U.S. Patent Application Publication No. US2005/0205658, discloses a
process equipment tracking system. This system includes the use of
RFID tags in conjunction with process equipment. The RFID tag is
described as capable of storing "at least one trackable event".
These trackable events are enumerated as cleaning dates, and batch
process dates. The publication also discloses an RFID reader that
is connectable to a PC or an internet, where a process equipment
database exists. This database contains multiple trackable events
and can supply information useful in determining "a service life of
the process equipment based on the accumulated data". The
application includes the use of this type of system with a variety
of process equipment, such as valves, pumps, filters, and
ultraviolet lamps.
[0007] Another patent application, filed by Jornitz et al and
published in 2004 as U.S. Patent Application Publication No.
2004/0256328, discloses a device and method for monitoring the
integrity of filtering installations. This publication describes
the use of filters containing an onboard memory chip and
communications device, in conjunction with a filter housing. The
filter housing acts as a monitoring and integrity tester. That
application also discloses a set of steps to be used to insure the
integrity of the filtering elements used in multi-round housings.
These steps include querying the memory element to verify the type
of filter that is being used, its limit data, and its production
release data.
[0008] Patent No. 6,936,160, issued to Moscaritolo in 2005,
describes a wireless MEMS sensing device, for use with filtering
elements. Moscaritolo describes a MEMS device, having at least two
different sensors in a single assembly package. The patent
discloses use of this MEMS device in the end cap of a filter,
preferably for measuring differential pressure of a fluid, thereby
allowing it to monitor the operating conditions within the housing.
Related patents also describe the use of this MEMS device to
estimate and predict a filter's life.
[0009] Despite the improvements that have occurred through the use
of RFID tags, there are additional areas that have not been
satisfactorily addressed. For example, there are a number of
applications, such as in-situ filter integrity testing and filter
life monitoring via transmembrane pressure changes, in which real
time monitoring of the pressure at various points within the filter
housing would be extremely beneficial.
SUMMARY OF THE INVENTION
[0010] The shortcomings of the prior art are overcome by the
present invention, which describes a system and method for
accurately measuring the pressure and/or flow at various points
within a filter housing. In one embodiment, a sensor, capable of
measuring the pressure at a specific point is used. In a second
embodiment, a differential pressure sensor, capable of measuring
the difference in pressure between two points, is employed. In a
third embodiment, a gas flow meter is incorporated into the nose of
a filter for directly measuring the flow of gas through that point
in the filter. Similarly, a differential pressure sensor or a
liquid flow sensor can be incorporated in a TFF module to measure
the flow of critical fluids, like cleaning fluids, within a system.
These sensors are in communication with a communications device so
that the combination is able to measure and transmit the pressure
measurement, while the filter is in use. This system can comprise a
single component, integrating both the communication device and the
pressure sensor. Alternatively, the system can comprise separate
sensor and transmitter components, in communication with one
another. The transmitter component can utilize either wired or
wireless communication. In yet another embodiment, a storage
element can be added to the system, thereby allowing the device to
store a set of pressure values.
[0011] The use of this device is beneficial to many applications.
For example, the ability to monitor transmembrane pressure across
each filter individually in a multiple filter configuration
improves the reliability and validity of an integrity test. This
also allows the integrity of each filtering element to be
individually determined in situ. The ability to monitor the
transmembrane pressure within the filter housing also enables the
plugging of multi-layer filters to be monitored, allowing the life
of the filter to be estimated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a representative embodiment of the present
invention;
[0013] FIG. 2 is a representative embodiment of the present
invention as used in a multi-element filter configuration;
[0014] FIG. 3 is a first representative embodiment of the present
invention as used to perform in situ integrity testing within
multi-element filter configurations;
[0015] FIG. 4 is a second representative embodiment of the present
invention as used to perform in situ integrity testing within
multi-element filter configurations; and
[0016] FIG. 5 is a representative embodiment of the present
invention as used to perform in situ integrity testing of
tangential flow filters.
DETAILED DESCRIPTION OF THE INVENTION
[0017] FIG. 1 illustrates a representative filtering system in
accordance with the present invention. The filter element 10 is
enclosed with a housing 20. The filter element can be simply a
porous material, such as pleated paper or PVDF (Polyvinylidene
fluoride) membrane. In an alternative embodiment, shown in FIG. 2,
multiple filter elements 10 are enclosed within one housing 20.
Alternatively, the filter element may comprise a frame, such as of
plastic, and a porous material. Located in close proximity of,
preferably affixed to, and most preferably embedded in, the end cap
of filter element 10 is a pressure sensor 30. This sensor 30 is
capable of generating an output, which varies as a function of the
pressure of the surrounding environment. In another embodiment, the
sensor is a differential sensor, whereby its output is a function
of the difference is pressure between two areas. This output can be
in the form of an analog voltage or current, or can be a digital
value or pulse. In the preferred embodiment, the output varies
linearly with the pressure, however this is not a requirement. Any
output having a known relationship, such as logarithmic or
exponential, to the surrounding pressure, can be employed. In such
a situation, a transformation of the output can be performed to
determine the actual measured pressure.
[0018] The pressure sensor 30 is preferably a differential sensor,
and is mounted on, or preferably embedded in, the end cap of the
filter element 10. The sensor is positioned such that it is capable
of measuring both the upstream and downstream pressure. In some
applications, the temperature of the filter element may exceed
145.degree. C., therefore a sensor that is stable at these
temperatures should be employed. Similarly, a transmitter capable
of withstanding this temperature should be employed. Finally, the
temperature with the housing 20 may cycle from lower temperatures
to higher temperatures and back, therefore the pressure sensor
should be able to withstand temperature cycling.
[0019] There are multiple embodiments of this pressure sensor. For
example, this sensor can be constructed using
micro-electro-mechanical system (MEMS) technology, a piezoelectric
element, a conductive or resistive polymer, including elastomers
and inks, or a transducer. While a differential pressure sensor is
preferred, since it is the difference between the upstream pressure
and the downstream pressure that is of interest, separate pressure
sensors, one on either side of the filter, may also be employed.
These examples are intended to be illustrative of some of the types
of sensors that can be used; this is not intended to be an
exhaustive list of all such suitable pressure sensors.
[0020] The pressure sensor 30 is in communication with a
transmitter 40, which can be either wired or wireless. Mechanisms
for transmitting wireless signals outside the housing have been
disclosed and are known in the art. United States Patent
Application Publication 2004/0256328 describes the use of an
antenna to relay information between transponders located on the
filter housing to a monitoring and test unit external to the
housing.
[0021] For flow measuring applications, such as those shown in FIG.
3, the pressure sensor 30 may optionally be combined with a
restriction orifice to achieve the sensitivity needed for the
application. This orifice or venturi restriction device is
typically used to measure liquid flow, but it may also be used to
measure gas flow when higher sensitivity than can be achieved by
measurement within the dimensions of the main flow path, like the
core of a filter, is required. For example, the flow rate typically
experienced during diffusion is 10 cc/min. In contrast, the flow
rate during convection is 500 cc/min to 1000 cc/min.
[0022] FIG. 4 shows the use of flow rate sensors 70, instead of
pressure sensors. There are multiple embodiments of direct flow
rate measuring sensors. In gas flow measuring applications, flow
measurement is typically determined by monitoring changes in
temperature. These devices can be based upon an anemometer within
which a current is passed and the anemometer wire heated. The
anemometer is cooled due to the gas flow and this is measured as a
current change in the sensor. Alternately, a slip stream of gas is
passed through a narrow capillary within which are two thermal
coils, one pulses heat into the flowing gas the other detects the
time for the temperature pulse to reach it. This is correlated to
total gas flow by properly designing the capillary to mail gas flow
tube diameters. Other methods of measuring flow rate are known in
the art, and are within the scope of the invention, as this list is
not meant to be exhaustive. The location of the flow rate sensor is
important, as certain locations within the filter housing are not
subjected to the full flow. For example, a flow rate sensor near
the end cap of the filter element would experience very little
flow, especially as compared to one near the open end of the filter
element.
[0023] A transmitter 40 is also located near, or integrated with,
the sensor 30. In one embodiment, the transmitter 40 and the
pressure sensor 30 are encapsulated in a single integrated
component. Alternatively, the transmitter 40 and the sensor 30 can
be separated, and in communication with each other, such as via
electrical signals. Various types of communication are possible,
such as wired and wireless. Various wireless communication devices
are possible, although the use of an RFID tag is preferred. An
active RFID tag allows regular communication with the reader.
Alternatively, a passive RFID tag can be used, whereby the energy
to transmit and sense the temperature is obtained from the
electromagnetic field transmitted by the RFID reader.
[0024] Optionally, a storage element 50 can be used in conjunction
with the transmitter 40 and the pressure sensor 30. This storage
element 50, which is preferably a random access memory (RAM) or
FLASH EPROM device, can be used to store a set of pressure
readings, such as may be generated by regular sampling of the
sensor.
[0025] This allows the rate at which the transmitter 40 sends data
to be different from the rate at which the pressure is sampled. For
example, the pressure may be sampled 10 times per second, while the
data is transmitted only once per second.
[0026] A wireless receiver, 60, optionally located outside the
filter housing 20, is used to communicate with the wireless
transmitter. In the preferred embodiment, an RFID reader or base
station is used. The reader can be configured such that it queries
the transmitter at regular intervals. Alternatively, the reader can
be manually operated so that readings are made when requested by
the equipment operator. In another embodiment, the wireless
receiver 60 also includes a storage element. This reduces the
complexity required of the device within the housing. In this
embodiment, the wireless receiver queries the wireless
transmitter/pressure sensor at preferably regular intervals. It
receives from the wireless transmitter the current pressure sensor
measurement as determined at that time. The wireless receiver 60
then stores this value in its storage element. The capacity of the
storage element can vary, and can be determined based on a variety
of factors. These include, but are not limited to, the rate at
which measurements are received, the rate at which the stored data
is processed, and the frequency with which this storage element is
in communication with its outside environment.
[0027] As an example, consider a filter element having a wireless
transmitter 40, such as an RFID tag, coupled with a pressure sensor
30. In this embodiment, the RFID tag is passive, that is, it only
sends data upon receipt of a query from the wireless receiver, or
base station. Upon receipt of that query, the transmitter transmits
the value currently available from the pressure sensor 30. In one
scenario, the wireless receiver, which is coupled to a computing
device, such as a computer, then stores these values, optionally
with an associated timestamp, such as in a log file. In a different
scenario, if the wireless receiver is separated from the computer,
the receiver will need to store a number of pressure measurements
internally, until such time as it is connected to the main
computing and/or storage device. In this case, a storage element
needs to be integrated with the receiver.
[0028] In another embodiment, a wireless transmitter and receiver
are not used; rather, the output of the pressure sensor is hard
wired to the outside of the housing.
[0029] Having defined the physical structure of the present
invention, there are a number of applications in which it is
beneficial. The following is meant to illustrate some of those
applications, however it is not intended as a recitation of all
such applications.
[0030] In one embodiment, the present invention is used in
conjunction with in situ Integrity Testing. This process allows the
operator to certify the integrity of the filters within the filter
housing at the customer site without additional equipment.
Specifically, a gas, typically air, is pressurized to a
predetermined pressure upstream of a liquid wetted filter contained
within an air tight housing. The pressure within the housing will
decay over time as a result of diffusional and potentially
convective flow of gas through the filter. The rate of pressure
decay is used to establish the integrity of the filter element. In
one embodiment, as shown in FIG. 3, a differential pressure sensor
is preferably positioned in the nose of the filter. This sensor,
preferably in combination with an orifice or venture is able to
measure the gas flow through the filter via the venturi effect. As
mentioned above, preferably an orifice is positioned in the nose of
the filter 10 such that the pressure drop, such as at 10 cc/min, is
measurable with a high degree of accuracy. This orifice is
preferably removable and only needs to be placed in the flow path
during this integrity test. In a second embodiment, as shown in
FIG. 4, a gas flow measuring device, such as an anemometer or mass
flow device, is employed to measure the gas flow directly.
[0031] For multi-round systems, multiple pressure sensors can be
introduced, so as to be able to determine the diffusion rate for
each individual filtering element. Currently, systems where
multiple filters are used in parallel are difficult to test. In
this situation, the specifications are multiplied by the number of
filters in the housing. Therefore, the ability to detect defects is
significantly reduced, because the errors are also multiplied.
Additionally, if a defect is found, it is not easily discernible
which filter was defective and each would need to be tested
individually. The use of pressure or flow sensors in each filter
improves the sensitivity of the test and allows each filter to be
independently tested. In addition, the preferred bubblepoint
integrity test, which measures gas flow over a broad range of
increasing pressures, can be measured on each filter individually;
a test protocol which is not possible currently.
[0032] In one embodiment, a plastic filter housing is utilized,
allowing the wireless transmitter to transmit pressure data through
the housing at any time.
[0033] The present invention also enables the monitoring of
transmembrane pressure. This monitoring of transmembrane pressure
has several benefits and applications. For example, the preferred
start up procedure for microfiltration (MF) filters is to ramp the
operating pressure, rather than opening to full operating pressure
immediately. This approach avoids air locks within the filter and
increases the filter's useful life. Internal pressure sensors can
be utilized to monitor the pressure within the housing and thus,
affect the proper ramp of operating pressure. In the preferred
embodiment, a differential pressure sensor is located in the end
cap of each filtering element, thereby allowing both the upstream
and downstream pressure to be observed. In one embodiment, the
pressure readings are transmitted via an RFID tag through the
plastic housing to an external wireless receiver.
[0034] Once the assembly has reached its operating pressure, the
internal pressure sensors allow continued monitoring of the
filters. For example, plugging of the filter will lead to a
reduction in flow rate and thus a corresponding reduction in
pressure on the downstream side of the filter. Based on the rate at
which the transmembrane pressure changes, an estimate of the useful
life of the filter can be made. If the pressure is sampled on a
continuous basis, any aberrant pressure fluctuations are observable
and these can be accounted for in estimating the remaining useful
life of the filter.
[0035] The above procedure is also applicable to multi-element
filter arrangements. In the preferred embodiment, a pressure sensor
is used to measure the upstream and downstream pressure of each
filtering element by affixing the sensor to the end cap of each
filter. The pressure measurements allow the operator to understand
better the operation of each filter within the filter housing
individually. For example, if a pressure drop were detected between
the upstream and downstream sides of a filtering element, it
typically would indicate a plugging or fouling of that element. As
explained above, the rate at which the transmembrane pressure
changes allows an estimation of useful filter life to be made.
Similarly, if the pressure across each filter is sampled on a
continuous basis, any aberrant pressure fluctuations are observable
and these can be accounted for in estimating the remaining useful
life of that particular filter.
[0036] Additionally, the present invention may be used to monitor
specific operating parameters, such as transmembrane pressure, in
tangential flow filtration (TFF) devices. These devices are
typically used in milti-filter, module, configurations.
Traditionally, the pressure drops between modules in TFF devices
are not monitored. This monitoring can be performed by introducing
pressure sensors between modules, as shown in FIG. 5. By monitoring
the pressure drop between modules, the flow rate can be estimated.
This flow rate can help determine that all modules are operating as
designed, especially during cleaning. The cleaning operation can be
verified when the individual membrane flux is recovered in each
module individually. Additionally, pressure sensors can be employed
within the membrane stacks in a module to monitor the transmembrane
pressure or the transchannel pressure to ensure even flow access to
each channel and to ensure that the module flux is uniform across
the module. Additionally, by monitoring the pressure at various
points within the housing, it is possible to determine internal
flows. Once this is known, this information can be then used to
regulate the flow within the channels so as to ensure that the
entire module is used in a uniform manner. Finally, the integrity
of a TFF module as measured by a diffusion test, can be determined
for each module individually by measuring the gas flow in the
outlet port of each module. The pressure measurements recorded by
the pressure sensors are transmitted outside the filter housing
through the use of the transmitter.
* * * * *