US20020060191A1 - Filter life measurement - Google Patents
Filter life measurement Download PDFInfo
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- US20020060191A1 US20020060191A1 US10/013,673 US1367301A US2002060191A1 US 20020060191 A1 US20020060191 A1 US 20020060191A1 US 1367301 A US1367301 A US 1367301A US 2002060191 A1 US2002060191 A1 US 2002060191A1
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- pressure drop
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- 238000001514 detection method Methods 0.000 claims description 3
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- 238000001914 filtration Methods 0.000 description 4
- 238000009530 blood pressure measurement Methods 0.000 description 3
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Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/0084—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours provided with safety means
- B01D46/0086—Filter condition indicators
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D35/00—Filtering devices having features not specifically covered by groups B01D24/00 - B01D33/00, or for applications not specifically covered by groups B01D24/00 - B01D33/00; Auxiliary devices for filtration; Filter housing constructions
- B01D35/14—Safety devices specially adapted for filtration; Devices for indicating clogging
- B01D35/143—Filter condition indicators
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D37/00—Processes of filtration
- B01D37/04—Controlling the filtration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D37/00—Processes of filtration
- B01D37/04—Controlling the filtration
- B01D37/043—Controlling the filtration by flow measuring
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D37/00—Processes of filtration
- B01D37/04—Controlling the filtration
- B01D37/046—Controlling the filtration by pressure measuring
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/42—Auxiliary equipment or operation thereof
- B01D46/44—Auxiliary equipment or operation thereof controlling filtration
- B01D46/446—Auxiliary equipment or operation thereof controlling filtration by pressure measuring
Definitions
- the invention relates to methods and devices for measuring the remaining useful life of a filter during flow of a particulate-laden fluid through the filter.
- One known method of indicating the end of the useful life of a filter measures the differential pressure of the fluid across the filter as fluid is passed through the filter and particulates are retained by the filter. As the amount of retained particulates increases, the differential pressure increases and, by previous testing, a differential pressure can be determined at which the filter is at the end of its useful life.
- a known device detects the differential pressure across the filter and gives an alarm signal when the previously determined differential pressure is reached.
- This apparatus provides no indication of the rate at which the filter is retaining the particulates and thus no indication of the remaining useful life and does not allow prediction of when the filter will have to be replaced or cleaned.
- Another known device also detects the differential pressure of the fluid across the filter and provides a rough indication of the differential pressure using a light emitting diode bar-graph.
- the number of diodes that are illuminated increases roughly in linear proportion to the increases in differential pressure.
- This apparatus does not readily allow a prediction of when it will be necessary to replace or clean the filter, because the changes in differential pressure are not linearly related to the changes in the remaining useful life of the filter.
- An aspect of the present invention may comprise a method of measuring the remaining useful life of a filter.
- the method may comprise flowing a particulate-laden fluid through the filter, measuring the pressure drop across the filter, outputting measurements of pressure drop to a store, the store holding a set of values indicative of pressure drop and the percentage of remaining useful life of the filter represented by those values.
- the store on receiving a measurement indicative of pressure drop, finding the corresponding stored value indicative of pressure drop, and outputting the value indicative of percentage of remaining useful life represented by the stored value.
- FIG. 1 shows a filter assembly including a filter element mounted in a housing, a differential pressure transducer of the filter assembly being connected to a data processor, and
- FIG. 2 is a graph plotting voltage output from a differential pressure transducer of the kind shown in FIG. 1 against percentage remaining useful life of the filter element of the assembly of FIG. 1.
- the filter assembly comprises a housing 10 defining a chamber 12 having a fluid inlet 13 and a fluid outlet 14 .
- a by-pass valve 33 is provided in a passage connecting the inlet 13 and the outlet 14 and opens to allow direct communication between the inlet 13 and the outlet 14 when excess differential pressure is detected.
- the outlet 14 is continuous with a mounting tube 15 which extends into the chamber 12 .
- a filter element 11 is mounted within the housing 10 and comprises a cylinder of a filter medium 16 which is provided at one end with a first end cap 17 and which is provided at the other end with a second end cap 18 .
- the fluid outlet 14 extends through the second end cap 18 and the by-pass passage leads through the first end cap 17 .
- the filter medium 16 may be any suitable form of media such as a membrane or a depth filter medium.
- the second end cap 18 is provided centrally with an opening 19 which receives the mounting tube 15 so as to mount the filter element 11 within the housing 10 .
- a seal (not shown) is provided between the mounting tube 15 and the perimeter of the opening 19 .
- the measuring device comprises a pressure transducer 20 and a processor 21 .
- the transducer 20 is mounted in the housing 10 and detects the differential pressure between fluid in the inlet 13 and fluid in the outlet 14 .
- the transducer 20 is connected via a cable 22 to the processor 21 .
- the processor 21 has a display 23 , and a data inlet/outlet 25 provided with an RS 232 connector.
- the processor 21 also has a writable memory 26 and an analogue to digital converter 27 .
- the filter element 11 is used to filter a flow of fluid carrying suspended particulates.
- the fluid is pumped through the housing 10 .
- the fluid passes through the inlet 13 into the chamber 12 (as shown by the arrows), where the fluid then passes around the filter element 11 .
- the fluid flows through the filter medium 16 into the interior of the filter element 11 .
- particulates from the fluid are retained by the medium 16 .
- the filtered, particle-depleted fluid passes out from the element 11 through the mounting tube 15 and the outlet 14 as shown by the arrows in FIG. 1.
- the particulates retained by the filter medium 16 reduce the overall permeability of the medium 16 .
- the volume of particulates retained by the medium 16 progressively increases and the overall permeability of the medium 16 progressively decreases.
- the remaining useful life thus decreases correspondingly.
- the differential pressure of the fluid across the medium 16 increases.
- the filter element 11 needs to be replaced or cleaned when the volume of particulates retained by the filter medium 16 reaches a predetermined level such that continued retention is likely to damage the filter medium 16 or is likely to render the filter medium 16 ineffective.
- Some filters are provided with a by-pass controlled by a valve that opens to allow direct fluid communication between the filter inlet 13 and the filter outlet 14 when the differential pressure across the by-pass valve exceeds a predetermined level. At this level, the remaining useful life of the filter material 16 is zero. As indicated above, this level can be related to a particular differential pressure and in this example, the attainment of the particular differential pressure is used to indicate when the filter element 16 has zero remaining useful life (as described below).
- the measuring device 20 , 21 , 22 uses the measured differential pressure to provide an indication of the remaining useful life of the filter medium 16 as determined by the blockage of the filter elements 16 by particulates and indicates the estimated remaining useful life in a way that varies generally linearly during the time that fluid is flowing through the filter (plainly there is no variation in useful life when the filter is not operational—this will occur in a filter used intermittently).
- a differential pressure of, say, 0.04 bar occurs 3 hours into a 10 hours useful life of a filter
- the receipt of a differential pressure signal corresponding to 0.04 bar will result in an indication that 30% of the useful life of the filter element 11 has passed (or that 70% of the useful life remains).
- the pressure transducer 20 detects the differential pressure between the fluid in the inlet 13 and the fluid in the outlet 14 (which, of course, corresponds to the differential pressure of the fluid across the medium 16 ) and generates an analogue signal which varies over time as a function of the differential pressure.
- the signal is passed to the analogue to digital converter 27 of the processor 21 via the cable 22 .
- the analogue to digital converter 27 produces from the analogue signal a sequence of digital signals corresponding to successive instantaneous values of the analogue signal and thus to successive measurements of the differential pressure.
- the processor 21 stores in the memory 26 a set of values of differential pressure and the remaining useful life represented by those values. These are formulated and input into the memory 26 in a manner to be described below. As a digital differential pressure signal is received by the memory 26 , the memory 26 produces the corresponding value of the remaining useful life. Where the received differential pressure signal falls between two stored values, an interpolator 28 generates the corresponding value of the remaining useful life. The interpolation may be linear.
- the measurements are output as digital signals.
- these digital signals are used to produce signals representing percentages indicating the remaining proportion of the useful life of the filter element 16 . For example, when the remaining time value is indicated as 10%, 10% of useful life remains.
- the current percentage of the remaining useful life is shown on the display 23 ; the display 23 being up-dated each time the remaining useful life changes by 1% (or any other suitable interval) to show the new value.
- the processor 21 also has a facility which allows the operator to display, when required, the current instantaneous measurement of the differential pressure. This is achieved by passing the instantaneous signal values from the transducer 20 to a display converter 29 which converts the instantaneous value signals into signals producing the appropriate indication on the display 23 .
- the displayed value can be in any required units, such as psi or bar.
- the display 23 includes a mode indicator 24 that indicates whether the displayed digits 32 are bar, psi or % remaining life.
- these measurements may be output to remote data logging equipment 30 using the data inlet/outlet 25 .
- the processor 21 may be programmed to produce an alarm message on the display 23 on receiving a signal corresponding to a differential pressure indicating that the remaining useful life is zero.
- Alarm messages may also be produced in the absence of a filter medium or on the sensing of a differential pressure above a predetermined level. These may be indicated by the arrows 34 on the display 23 . Alarm messages may be produced at other predetermined stages in the monitoring process.
- An operator can use the displayed remaining time values to predict when replacement or cleaning of the element 11 will be necessary and replace or clean the element 11 as soon as (or before) zero remaining useful life is indicated.
- the measurements of remaining useful life or differential pressure that have been stored in the memory during filtration can be down loaded to a computer 31 for analysis.
- This analysis may involve comparing the useful life of a first filter used in the housing 10 with the useful life of a subsequent filter or filters.
- This down-loading is done using the data inlet/outlet 25 and a suitable interrogating computer 31 using Windows (Trade Mark) based or other suitable software. The same computer is used to programme the processor 21 before filtration is commenced.
- the stored data may be formulated by performing a trial run using a trial filter element corresponding to the element 11 to filter a particulate-laden fluid corresponding to, or corresponding as nearly as possible to, the particulate-laden fluid to be filtered by the filter element 16 .
- the fluid is passed through the trial filter element at a constant rate.
- a pressure transducer of a similar type as the pressure transducer 20 is used to measure the differential pressure across the trial filter element. The elapsed time from the start of the trial run is also noted.
- the trial run is continued until the blockage of the trial filter element by particulates reaches a level at which the trial filter element should be replaced or cleaned.
- the level can be determined empirically by observing at what differential pressure the filter medium is close to damage or inutility and choosing a pressure lower than this by a safety margin.
- the measurements of the differential pressure and the corresponding set of measurements of the remaining useful life so that for each differential pressure measurement an associated remaining useful life figure is calculated.
- This data is recorded on a magnetic disc and input into the memory of the processor 21 using the inlet/outlet 25 and a suitable computer using WINDOWS (TM) based software.
- the processor 21 is thus able, on receiving a measurement of differential pressure from the transducer 20 to produce the corresponding measurement of remaining useful life via the data using interpolation if necessary, as described above.
- Table 1 A first example of such data is shown in Table 1 below.
- FIG. 2 A second example of such data is shown in the graph that is FIG. 2.
- the voltage (v) of a transducer 20 measuring the pressure drop across a filter element 11 as particulate-laden fluid is flowed through the filter element 11 is plotted against the measured percentage of remaining useful life. It will be seen that the relationship is non-linear but that for every voltage representing a differential pressure, it is possible to derive a percentage of remaining useful life.
- a disc may contain data for many different filters and that a disc may be supplied with a new filter.
- the apparatus may be self-calibrating. This is achieved by measuring the differential pressure across the filter element 11 using the differential pressure transducer 20 and simultaneously measuring the time during which the filter is operational. If the filtration is halted at a differential pressure indicating the end of useful life of the filter, the processor can, from this data, derive the stored data needed for the processor 21 to output remaining life data during subsequent filtration operations. The time intervals are determined from the sampling intervals.
- the apparatus described above is best suited for use when the flow-rate of the fluid through the element 11 does not vary with time.
- the processor 21 has an averaging programme and a peak detection programme, one or the other of which may be used when the flow rate is uneven.
- the averaging programme averages a predetermined number of the instantaneous signal values and uses the average value to determine the remaining time value from the stored data.
- the peak detection programme monitors a predetermined number of the instantaneous signal values and uses the highest value to determine the remaining time value from the stored data.
- the apparatus described above has a number of other advantages. For example, a number of different data sets corresponding to a number of alternative pressure detectors or alternative fluids or alternative particle sizes can be formulated for use with the same element.
- the pressure transducer 20 generates a signal which is linearly proportional to the differential pressure.
- the stored data is formulated using values derived from a detector corresponding to the detector 20 any non-linearity will be compensated for by use of the look-up table.
- RS 232 serial data transmission line
- the signal generated by the transducer 20 may be a sequence of discrete signals, each being related by a function to corresponding instantaneous values of the differential pressure.
- the transducer 20 itself could produce digital signals and in this case the digital-to-analogue converter would be omitted.
- the transducer 20 may be provided with a thermal lockout device that prevents actuation due to viscosity effects of the fluid.
- the stored data could correlate differential pressure measurements with values of elapsed time.
- the processor 21 would then contain data relating the elapsed time to the remaining time.
- the stored data could relate differential pressure measurements to indications of the remaining useful life of the filter medium 16 other than the blockage of the medium by particulates.
- the look-up table could relate signal values to the weight of particles retained by the medium 16 .
- the display 23 would then indicate remaining useful life based on the weight of particles retained by the filter element.
- the flow parameter measured need not be differential pressure. It could, for example, be simply inlet or outlet pressure.
Abstract
A method of measuring the remaining useful life of a filter may comprise flowing a particulate-laden fluid through a filter, measuring values indicative of pressure drop across the filter, and outputting the values to a store. The store may hold a set of values indicative of pressure drop and the percentage of remaining useful life of the filter represented by those values. On receiving a measurement indicative of pressure drop, the store may find the corresponding stored value indicative of pressure drop and output the value indicative of percentage of remaining useful life represented by the stored value.
Description
- This application is a continuation application of U.S. patent application Ser. No. 09/381,169, filed Dec. 6, 1999, which claims the benefit of WO 98/42425, filed Mar. 17, 1998, which was published in the English language under PCT Article 21(2), and United Kingdom Application No. 9705818.4, filed Mar. 20, 1997, which are all incorporated herein by reference.
- The invention relates to methods and devices for measuring the remaining useful life of a filter during flow of a particulate-laden fluid through the filter.
- As a particulate-laden fluid passes through a filter, the particulates are retained in the filter. It is generally desirable to change or clean a filter element of the filter before it becomes completely blocked with particulates as further clogging could lead to excessive differential pressures within the filter. The point at which such a change or cleaning is desirable is called the end of the useful life of the filter.
- One known method of indicating the end of the useful life of a filter measures the differential pressure of the fluid across the filter as fluid is passed through the filter and particulates are retained by the filter. As the amount of retained particulates increases, the differential pressure increases and, by previous testing, a differential pressure can be determined at which the filter is at the end of its useful life.
- A known device detects the differential pressure across the filter and gives an alarm signal when the previously determined differential pressure is reached. This apparatus provides no indication of the rate at which the filter is retaining the particulates and thus no indication of the remaining useful life and does not allow prediction of when the filter will have to be replaced or cleaned.
- Another known device also detects the differential pressure of the fluid across the filter and provides a rough indication of the differential pressure using a light emitting diode bar-graph. The number of diodes that are illuminated increases roughly in linear proportion to the increases in differential pressure. This apparatus does not readily allow a prediction of when it will be necessary to replace or clean the filter, because the changes in differential pressure are not linearly related to the changes in the remaining useful life of the filter.
- An aspect of the present invention may comprise a method of measuring the remaining useful life of a filter. The method may comprise flowing a particulate-laden fluid through the filter, measuring the pressure drop across the filter, outputting measurements of pressure drop to a store, the store holding a set of values indicative of pressure drop and the percentage of remaining useful life of the filter represented by those values. The store on receiving a measurement indicative of pressure drop, finding the corresponding stored value indicative of pressure drop, and outputting the value indicative of percentage of remaining useful life represented by the stored value.
- The following is a more detailed description, by way of example, of an embodiment of the invention, reference being made to the accompanying drawings in which:
- FIG. 1 shows a filter assembly including a filter element mounted in a housing, a differential pressure transducer of the filter assembly being connected to a data processor, and
- FIG. 2 is a graph plotting voltage output from a differential pressure transducer of the kind shown in FIG. 1 against percentage remaining useful life of the filter element of the assembly of FIG. 1.
- Referring to FIG. 1, the filter assembly comprises a
housing 10 defining achamber 12 having afluid inlet 13 and afluid outlet 14. A by-pass valve 33 is provided in a passage connecting theinlet 13 and theoutlet 14 and opens to allow direct communication between theinlet 13 and theoutlet 14 when excess differential pressure is detected. Theoutlet 14 is continuous with amounting tube 15 which extends into thechamber 12. Afilter element 11 is mounted within thehousing 10 and comprises a cylinder of afilter medium 16 which is provided at one end with afirst end cap 17 and which is provided at the other end with asecond end cap 18. Thefluid outlet 14 extends through thesecond end cap 18 and the by-pass passage leads through thefirst end cap 17. Thefilter medium 16 may be any suitable form of media such as a membrane or a depth filter medium. Thesecond end cap 18 is provided centrally with an opening 19 which receives themounting tube 15 so as to mount thefilter element 11 within thehousing 10. A seal (not shown) is provided between themounting tube 15 and the perimeter of theopening 19. - The measuring device comprises a
pressure transducer 20 and aprocessor 21. Thetransducer 20 is mounted in thehousing 10 and detects the differential pressure between fluid in theinlet 13 and fluid in theoutlet 14. Thetransducer 20 is connected via acable 22 to theprocessor 21. - The
processor 21 has adisplay 23, and a data inlet/outlet 25 provided with an RS 232 connector. Theprocessor 21 also has awritable memory 26 and an analogue to digital converter 27. - The
filter element 11 is used to filter a flow of fluid carrying suspended particulates. The fluid is pumped through thehousing 10. The fluid passes through theinlet 13 into the chamber 12 (as shown by the arrows), where the fluid then passes around thefilter element 11. The fluid flows through thefilter medium 16 into the interior of thefilter element 11. During the passage of the fluid through thefilter medium 16, particulates from the fluid are retained by themedium 16. The filtered, particle-depleted fluid passes out from theelement 11 through themounting tube 15 and theoutlet 14 as shown by the arrows in FIG. 1. - The particulates retained by the
filter medium 16 reduce the overall permeability of themedium 16. As more fluid passes through themedium 16, the volume of particulates retained by themedium 16 progressively increases and the overall permeability of themedium 16 progressively decreases. The remaining useful life thus decreases correspondingly. At the same time, the differential pressure of the fluid across themedium 16 increases. - The
filter element 11 needs to be replaced or cleaned when the volume of particulates retained by thefilter medium 16 reaches a predetermined level such that continued retention is likely to damage thefilter medium 16 or is likely to render thefilter medium 16 ineffective. Some filters are provided with a by-pass controlled by a valve that opens to allow direct fluid communication between thefilter inlet 13 and thefilter outlet 14 when the differential pressure across the by-pass valve exceeds a predetermined level. At this level, the remaining useful life of thefilter material 16 is zero. As indicated above, this level can be related to a particular differential pressure and in this example, the attainment of the particular differential pressure is used to indicate when thefilter element 16 has zero remaining useful life (as described below). - The
measuring device filter medium 16 as determined by the blockage of thefilter elements 16 by particulates and indicates the estimated remaining useful life in a way that varies generally linearly during the time that fluid is flowing through the filter (plainly there is no variation in useful life when the filter is not operational—this will occur in a filter used intermittently). Thus, if a differential pressure of, say, 0.04 bar occurs 3 hours into a 10 hours useful life of a filter, the receipt of a differential pressure signal corresponding to 0.04 bar will result in an indication that 30% of the useful life of thefilter element 11 has passed (or that 70% of the useful life remains). - The
pressure transducer 20 detects the differential pressure between the fluid in theinlet 13 and the fluid in the outlet 14 (which, of course, corresponds to the differential pressure of the fluid across the medium 16) and generates an analogue signal which varies over time as a function of the differential pressure. The signal is passed to the analogue to digital converter 27 of theprocessor 21 via thecable 22. The analogue to digital converter 27 produces from the analogue signal a sequence of digital signals corresponding to successive instantaneous values of the analogue signal and thus to successive measurements of the differential pressure. - The
processor 21 stores in the memory 26 a set of values of differential pressure and the remaining useful life represented by those values. These are formulated and input into thememory 26 in a manner to be described below. As a digital differential pressure signal is received by thememory 26, thememory 26 produces the corresponding value of the remaining useful life. Where the received differential pressure signal falls between two stored values, aninterpolator 28 generates the corresponding value of the remaining useful life. The interpolation may be linear. - The measurements are output as digital signals. In this example, these digital signals are used to produce signals representing percentages indicating the remaining proportion of the useful life of the
filter element 16. For example, when the remaining time value is indicated as 10%, 10% of useful life remains. - The current percentage of the remaining useful life is shown on the
display 23; thedisplay 23 being up-dated each time the remaining useful life changes by 1% (or any other suitable interval) to show the new value. Theprocessor 21 also has a facility which allows the operator to display, when required, the current instantaneous measurement of the differential pressure. This is achieved by passing the instantaneous signal values from thetransducer 20 to adisplay converter 29 which converts the instantaneous value signals into signals producing the appropriate indication on thedisplay 23. The displayed value can be in any required units, such as psi or bar. As seen in FIG. 1, thedisplay 23 includes amode indicator 24 that indicates whether the displayeddigits 32 are bar, psi or % remaining life. - The measurements of the remaining useful life or the corresponding instantaneous values of the differential pressure are stored in the memory.
- If it is desired to monitor the measurements of the remaining useful life or the differential pressure values remotely from the measuring device, these measurements may be output to remote
data logging equipment 30 using the data inlet/outlet 25. - The
processor 21 may be programmed to produce an alarm message on thedisplay 23 on receiving a signal corresponding to a differential pressure indicating that the remaining useful life is zero. Alarm messages may also be produced in the absence of a filter medium or on the sensing of a differential pressure above a predetermined level. These may be indicated by thearrows 34 on thedisplay 23. Alarm messages may be produced at other predetermined stages in the monitoring process. - An operator can use the displayed remaining time values to predict when replacement or cleaning of the
element 11 will be necessary and replace or clean theelement 11 as soon as (or before) zero remaining useful life is indicated. - If required, the measurements of remaining useful life or differential pressure that have been stored in the memory during filtration can be down loaded to a
computer 31 for analysis. This analysis may involve comparing the useful life of a first filter used in thehousing 10 with the useful life of a subsequent filter or filters. This down-loading is done using the data inlet/outlet 25 and a suitable interrogatingcomputer 31 using Windows (Trade Mark) based or other suitable software. The same computer is used to programme theprocessor 21 before filtration is commenced. - The stored data may be formulated by performing a trial run using a trial filter element corresponding to the
element 11 to filter a particulate-laden fluid corresponding to, or corresponding as nearly as possible to, the particulate-laden fluid to be filtered by thefilter element 16. The fluid is passed through the trial filter element at a constant rate. A pressure transducer of a similar type as thepressure transducer 20 is used to measure the differential pressure across the trial filter element. The elapsed time from the start of the trial run is also noted. - During this trial, the temperature of the fluid is monitored and the instantaneous values of the signal are corrected for any variation in temperature.
- The trial run is continued until the blockage of the trial filter element by particulates reaches a level at which the trial filter element should be replaced or cleaned. The level can be determined empirically by observing at what differential pressure the filter medium is close to damage or inutility and choosing a pressure lower than this by a safety margin.
- After the trial run, the measurements of the differential pressure and the corresponding set of measurements of the remaining useful life so that for each differential pressure measurement an associated remaining useful life figure is calculated. This data is recorded on a magnetic disc and input into the memory of the
processor 21 using the inlet/outlet 25 and a suitable computer using WINDOWS (TM) based software. Theprocessor 21 is thus able, on receiving a measurement of differential pressure from thetransducer 20 to produce the corresponding measurement of remaining useful life via the data using interpolation if necessary, as described above. A first example of such data is shown in Table 1 below.TABLE I Differential Elapsed Useful Remaining Pressure (Bar) Life (%) Useful Life (%) 0 0 100 0.01 10 90 0.02 20 80 0.04 30 70 0.08 40 60 0.16 50 50 0.32 60 40 0.64 70 30 1.28 80 20 2.56 90 10 5.12 100 0 - A second example of such data is shown in the graph that is FIG. 2. In this graph, the voltage (v) of a
transducer 20 measuring the pressure drop across afilter element 11 as particulate-laden fluid is flowed through thefilter element 11 is plotted against the measured percentage of remaining useful life. It will be seen that the relationship is non-linear but that for every voltage representing a differential pressure, it is possible to derive a percentage of remaining useful life. - It will be appreciated that a disc may contain data for many different filters and that a disc may be supplied with a new filter.
- It will also be appreciated that the apparatus may be self-calibrating. This is achieved by measuring the differential pressure across the
filter element 11 using thedifferential pressure transducer 20 and simultaneously measuring the time during which the filter is operational. If the filtration is halted at a differential pressure indicating the end of useful life of the filter, the processor can, from this data, derive the stored data needed for theprocessor 21 to output remaining life data during subsequent filtration operations. The time intervals are determined from the sampling intervals. - The apparatus described above is best suited for use when the flow-rate of the fluid through the
element 11 does not vary with time. However, theprocessor 21 has an averaging programme and a peak detection programme, one or the other of which may be used when the flow rate is uneven. The averaging programme averages a predetermined number of the instantaneous signal values and uses the average value to determine the remaining time value from the stored data. The peak detection programme monitors a predetermined number of the instantaneous signal values and uses the highest value to determine the remaining time value from the stored data. - In addition to allowing the operator to predict with greater accuracy when the
filter element 11 will need replacing or cleaning, the apparatus described above has a number of other advantages. For example, a number of different data sets corresponding to a number of alternative pressure detectors or alternative fluids or alternative particle sizes can be formulated for use with the same element. - Additionally, it is not necessary that the
pressure transducer 20 generates a signal which is linearly proportional to the differential pressure. As the stored data is formulated using values derived from a detector corresponding to thedetector 20 any non-linearity will be compensated for by use of the look-up table. - Up to eight monitors of the type described above may be connected together to a single serial data transmission line (RS232) for remote system control and data acquisition.
- It will be appreciated that the device and the method described above may be varied. For example, the signal generated by the
transducer 20 may be a sequence of discrete signals, each being related by a function to corresponding instantaneous values of the differential pressure. Thetransducer 20 itself could produce digital signals and in this case the digital-to-analogue converter would be omitted. Thetransducer 20 may be provided with a thermal lockout device that prevents actuation due to viscosity effects of the fluid. - The stored data could correlate differential pressure measurements with values of elapsed time. The
processor 21 would then contain data relating the elapsed time to the remaining time. - The stored data could relate differential pressure measurements to indications of the remaining useful life of the
filter medium 16 other than the blockage of the medium by particulates. For example, the look-up table could relate signal values to the weight of particles retained by the medium 16. Thedisplay 23 would then indicate remaining useful life based on the weight of particles retained by the filter element. The flow parameter measured need not be differential pressure. It could, for example, be simply inlet or outlet pressure. - It will be appreciated that the techniques described above are not limited to use in filters. Other measurements that vary non-linearly may be transformed to a linear measurement using these techniques and the scope of the invention encompasses such wider uses.
Claims (7)
1. A method of measuring the remaining useful life of a filter comprising:
flowing a particulate-laden fluid through the filter,
measuring values indicative of pressure drop across the filter,
outputting the values to a store, the store holding a set of values indicative of pressure drop and the percentage of remaining useful life of the filter represented by those values, the store on receiving a measurement indicative of pressure drop, finding the corresponding stored value indicative of pressure drop, and outputting the value indicative of percentage of remaining useful life represented by the stored value.
2. The method according to claim 1 , wherein measuring the pressure drop across the filter includes generating signals related to pressure drop across the filter.
3. The method according to claim 1 , further comprising displaying values of percentage of remaining useful life in accordance with the value output by the store.
4. The method according to claim 1 , wherein the store holding a set of values includes the store holding a set of values corresponding to more than one alternative pressure detectors or more than one alternative fluids or more than one alternative particle sizes formulated for use with the filter.
5. The method according to claim 1 , wherein the store holding the set of values includes the store holding a plurality of sets of values each relating to a different filter.
6. The method according to claim 1 , wherein the store holding a set of values comprises holding a set of values in a computer, disc, or other digital storage device.
7. The method according to claim 1 , wherein the store receiving the measurement indicative of pressure drop includes applying averaging/peak detection techniques to the measurement indicative of pressure drop to modify the measurement before finding the corresponding stored value indicative of pressure drop, and outputting the value indicative of percentage of remaining useful life represented by the stored value.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/013,673 US20020060191A1 (en) | 1997-03-20 | 2001-12-13 | Filter life measurement |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9705818.4 | 1997-03-20 | ||
GB9705818A GB2323310B (en) | 1997-03-20 | 1997-03-20 | Filter life measurement |
US09/381,169 US6334959B1 (en) | 1997-03-20 | 1998-03-17 | Filter life measurement |
US10/013,673 US20020060191A1 (en) | 1997-03-20 | 2001-12-13 | Filter life measurement |
Related Parent Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1998/000788 Continuation WO1998042425A1 (en) | 1997-03-20 | 1998-03-17 | Filter life measurement |
US09/381,169 Continuation US6334959B1 (en) | 1997-03-20 | 1998-03-17 | Filter life measurement |
Publications (1)
Publication Number | Publication Date |
---|---|
US20020060191A1 true US20020060191A1 (en) | 2002-05-23 |
Family
ID=10809597
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/381,169 Expired - Fee Related US6334959B1 (en) | 1997-03-20 | 1998-03-17 | Filter life measurement |
US10/013,673 Abandoned US20020060191A1 (en) | 1997-03-20 | 2001-12-13 | Filter life measurement |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/381,169 Expired - Fee Related US6334959B1 (en) | 1997-03-20 | 1998-03-17 | Filter life measurement |
Country Status (8)
Country | Link |
---|---|
US (2) | US6334959B1 (en) |
EP (1) | EP0975408A1 (en) |
JP (1) | JP2001518187A (en) |
AU (1) | AU733171B2 (en) |
CA (1) | CA2284564A1 (en) |
GB (1) | GB2323310B (en) |
NO (1) | NO994468L (en) |
WO (1) | WO1998042425A1 (en) |
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US20110054811A1 (en) * | 2009-08-31 | 2011-03-03 | Snecma | Monitoring a filter used for filtering a fluid in an aircraft engine |
US20110127206A1 (en) * | 2008-08-04 | 2011-06-02 | Ulrich Meyer-Blumenroth | Filtration system having fluid couplings |
US20110154242A1 (en) * | 2009-12-21 | 2011-06-23 | Jed Babbington Stevens | Flow differential pressure module |
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- 1998-03-17 EP EP98910869A patent/EP0975408A1/en not_active Withdrawn
- 1998-03-17 WO PCT/GB1998/000788 patent/WO1998042425A1/en not_active Application Discontinuation
- 1998-03-17 JP JP54444898A patent/JP2001518187A/en active Pending
- 1998-03-17 US US09/381,169 patent/US6334959B1/en not_active Expired - Fee Related
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WO2004037383A1 (en) * | 2002-10-18 | 2004-05-06 | Pti Technologies, Inc. | Prognostic health monitoring of fluidic systems using mems (micro-electromechanical systems) |
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US8352200B2 (en) | 2009-08-31 | 2013-01-08 | Snecma | Monitoring a filter used for filtering a fluid in an aircraft engine |
FR2949352A1 (en) * | 2009-08-31 | 2011-03-04 | Snecma | MONITORING A FILTER FOR FILTERING A FLUID IN AN AIRCRAFT ENGINE |
US20110054811A1 (en) * | 2009-08-31 | 2011-03-03 | Snecma | Monitoring a filter used for filtering a fluid in an aircraft engine |
US20110154242A1 (en) * | 2009-12-21 | 2011-06-23 | Jed Babbington Stevens | Flow differential pressure module |
US20170296965A1 (en) * | 2016-04-13 | 2017-10-19 | Carleton Life Support Systems Inc. | On-board inert gas generating system prognostic health monitoring |
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US11850538B2 (en) | 2018-12-11 | 2023-12-26 | Yamashin-Filter Corp. | Filter life predicting apparatus |
Also Published As
Publication number | Publication date |
---|---|
AU6509598A (en) | 1998-10-20 |
EP0975408A1 (en) | 2000-02-02 |
GB2323310B (en) | 2001-04-18 |
GB2323310A (en) | 1998-09-23 |
AU733171B2 (en) | 2001-05-10 |
NO994468L (en) | 1999-11-03 |
GB9705818D0 (en) | 1997-05-07 |
CA2284564A1 (en) | 1998-10-01 |
NO994468D0 (en) | 1999-09-15 |
US6334959B1 (en) | 2002-01-01 |
JP2001518187A (en) | 2001-10-09 |
WO1998042425A1 (en) | 1998-10-01 |
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