DE3917856C2 - Measuring device as part of a test facility for filter systems, test facility and test methods - Google Patents

Description

The invention relates to a measuring device as part of a test device for Filter systems, overall a test facility for filter systems, the use such a test facility and test methods for integrity testing various filter systems, with individual elements or a multitude of Filter elements in one housing. Such a measuring device and such The test facility is the German utility model 85 13 372.8 Applicant known. This measuring device is a small format Handy measuring device, which is directly connected to a connecting piece Checking filter system connectable and according to a specified Test program can be activated.

On the other hand, complex measuring devices are already part of a test facility for Filter systems known (DE-PS 31 17 399, DE-OS 33 31 420, DE-OS 36 18 112), with different test parameters via fixed program sequences Keypads can be entered and called up and in an alphanumeric display and Printers can be displayed.

In the company publication Coulter Porometer from Coulter Electronics GmbH, Krefeld, (1986) is a measuring device with which the bubble point determination for filters is feasible, the microprocessor-controlled, menu-driven Device for entering a menu program for performing the test allows specific filter by selecting the pore size range.

With regard to a variety of different filter systems different The design and size of these known measuring devices are, however, with regard to their Ease of use, speed and meaningfulness of the test results in need of improvement.

Important factors influencing the test are often not taken into account. The integrity check of filter systems using automatic, computer Controlled test devices do not always lead to reliable test results, especially if multiple filter systems (multiple filter elements in  housing), or a temperature influence of the measured values has taken place.

In the first case, it can happen that due to the fact that in multiple Systems always the sum of all individual diffusions and the resulting one Pressure drop is detected, despite individual slightly leaky filter elements Overall test is passed, while in the second case, integrity tests at elevated Temperatures are only possible if the Temperature is kept constant during the test.

In addition, the test procedures performed (e.g. pressure maintenance test) indicate in in some cases no clear statement about the integrity of the used Filter elements, so that often not between housing leaks and defective Filter elements can be distinguished.

The integrity test of hydrophobic filter elements poses a particular problem when used as a ventilation filter on sterile tanks or fermenters will.

The necessity here proves to be particularly disturbing Wetting liquid (mostly primary alcohols) after the test by expensive and having to remove lengthy drying processes quantitatively, which almost excludes an "inline" measurement.

Large systems can also be used due to their large input side Do not check the net volume with automatic integrity testers.

The invention is therefore based on the object of a measuring device as part of a Training device for filter systems so that the ease of use also for checking different filter systems and a variety of Filter systems is simplified and the significance of the test results is increased, as well as test methods using the test facility with the Propose measuring device.  

This object is achieved by the main claim and in the solved claims specified features. Beneficial Further developments are specified in the subclaims.

An embodiment of the accompanying invention is based on the accompanying Drawing described in more detail. It shows:

Fig. 1 is a perspective view of the measuring device in connection with a schematically illustrated filter system,

Fig. 2 is a block diagram of the electronics of the measuring device,

Fig. 3 is a block diagram of the pneumatics of the measuring instrument,

Fig. 4 is a block diagram of the process computer and interface,

Fig. 5 is a block diagram of the measuring device in connection with peripheral connectable,

FIG. 6a shows a program selection and function flow diagram of the measuring device,

Fig. 6b shows a functional flow chart for the complete self-test,

Fig. 6c a functional plan for the short self-test,

Fig. 7 shows a test chart for 5 filter elements (filter-candles) in a housing,

Fig. 8 shows another test chart,

Fig. 9 is a test chart from the values of FIG. 7 and 8,

Fig. 10 is a schematic diagram of test apparatus for the differential pressure maintenance / diffusion assay,

Fig plex mode. 11 is a circuit arrangement for a device plug for Multi,

Fig. 12 is a schematic drawing of a test device for hydrophobic filter elements and

Fig. 13 is a schematic diagram for the practical design of a Prüfein direction of a hydrophobic vent filter for a fermenter or the like for an in-line examination.

According to the general drawing Fig. 1 is coupled to the filter system 14 via the pneumatic connection hose 12 connectable measuring device 1 of a splash-proof plastic housing 3, which has an Operation tableau which the input keyboard 2, an LCD Dis play 2 ', a printer device 4 , and has at least part of the electronics inside. The lower housing part essentially takes up the pneumatic direction and has a compressed gas inlet 6 , which is connected via line 5 to a pneumatic source 15 , at least one compressed gas outlet 7 , which is connected via a connecting hose 12 to the filter system 14 , and also has a mains connection 9 , pneumatic lines 10 , a ventilation connection 11 , a connection 19 'for the temperature sensor line 19 , a further connection 7 a for connection to a second pressure sensor 7 b via line 12 ' and at least one serial interface 13 .

To avoid unnecessary repetitions, the in the schematic drawings, block diagrams, flow diagrams and test diagrams as well as their labels graphically logical links also to the subject of Revelation explained in the description.

The lines indicated in the block diagrams with the designation 19 and 19 'are electrical lines for connecting the electrical components to one another and the lines with the designation 10 are pneumatic lines for connecting the individual construction parts to one another. According to block diagram of Fig. 2, the measuring device 1 comprises a printer 4, a display 2 ', an input keyboard 2, a process computer 17 and a system peripherals interface 18 with a plurality of data outputs to the electro-pneumatic relay valves and various sensors.

An additional hand terminal 16 with connection options to a HOST computer and to device modules is provided for the need to expand and extend the measuring device.

Referring to FIG. 3, the pneumatic part of the measuring device 1 comprises a pressure medium source 15 having a connecting line 5 to a pressure regulator 20, a proportional valve 21, pressure sensor 22, which by internal pneumatic lines 10 as well as an outlet valve V2 and a vent valve V3 are linked, the linked pneumatic components metrologically form a reference volume together with the reference container 23 . The electronics interface 24 is in turn linked via electrical data lines 19 to a liquid sensor 25 and this in turn is linked via a pneumatic line 10 to the output valve V2, the output 7 of which leads to a test container of the filter system or to a device module.

According to FIG. 4, the electronics interface 24 includes sensors 26 and driver 27, 28, 29 for different functions.

The process computer comprises an A / D converter 30 , a D / A converter 31 , a parallel port 32 , a serial port 32 a, a microcomputer 33 , a ROM or Prom as program memory 34 , a RAM / EE Prom data memory 35 and a non-volatile RAM parameter memory 36 (buffered supply), which are linked to one another by data lines 19 . The microcomputer 33 in turn is linked by data lines 19 to the display and control elements and to the device modules and the HOST computer.

The block diagram of FIG. 5 for the peripheral to the actual measuring instrument 1 shows clearly that the instrument 1 for metrological detection of a plurality of filter systems 14 and test containers of different sizes and different characteristics with respect to the filter elements by additional device modules M1 to Mn can be supplemented is where again several filter systems such. B. 1/14 , 2/14 and 3/14 can be assigned to a device module M1 and further filter systems 4/14 to 6/14 can be assigned to a second device module M2, wherein the individual modules M1 to Mn can take over specific functions.

By connecting to a HOST computer 37 , the measuring device 1 can be fed with further data of the device user and user.

The flow chart for the program selection and the functional sequence according to FIG. 6a for the self-test according to FIGS. 6b and 6c, which is understandable due to the labeling and the logical combination, is hereby supplemented as follows. The various test methods for a filter system are test methods known from the prior art documented at the beginning. It is e.g. B. a complete self-test in which the measuring device and filter system are checked for functionality before further tests are carried out. Such tests are usually a pressure maintenance test, a diffusion test, a bubble point test and, according to the invention, a determination of the system volume and the new methods of multiplex measurement, 2-point measurement and the differential pressure maintenance test.

The device has 99 directly selectable, internal devices Program memory for storing test specifications and test parameters under the selected program number. The operator has the option of using a menu program select individual programs directly. After turning on of the device and before the start of the first test sequence automatically a complete self-test while in front of everyone further measurement, a short self-test is carried out.  

During the integrity check of the filter system, a temperature-compensated measurement is carried out via a temperature sensor 38 . The volume is determined by including the reference container 23 , the reference volume being determined from the volume of the pneumatic lines and by the additional reference container 23 .

A device-internal detection checks whether a Residual pressure is present in the system to be replaced Avoid measuring incorrect measurements. Through an automa tables, internal calculation of the maximum allowed Pressure drop based on entered diffusion and test time, as well as the measured system volume constant calculation by the user. Furthermore is an automatic detection of the system volume at the Bubble point measurement given. By linking together Bare device modules in the modular principle is the same timely testing of more than one filter system possible and both for filters of the same pore size and for Filters with different pore sizes. By determination and Printout of a pressure / diffusion curve up to Bubble point is an additional evaluation aid.

Using the following test examples for filter systems with Multiple assemblies with filter elements are the inventions improvements over test facilities and Test methods according to the state of the art clearly.

example 1 Method for determining individual defective filter candles from a large number of candles in one system (two- or multi-point measurement) - (see FIGS. 7 to 9).

Based on the consideration that the diffusion at in tegren membrane filter cartridges linear to the applied test pressure increases (in the range up to 80% of the bubble point (BP)), with egg  ner defective candle increases disproportionately, however compare the measured values for at least two ver different test pressure gradients the possibility in more subject systems even if the overall test is passed to determine defective filter elements.

The following applies to integral filter elements:

The following applies to multiple systems with individual defective filter elements:

Applying the two equations to the integrity check with two different test pressure gradients results in:

In the event: value 1 = value 2, all filter cartridges are with integrity.

In the event: Value 1 <Value 2 is at least one filter element malfunction.  

Example 2 Temperature compensation of the measured values (see Fig. 1)

All pressure measurements, like those of automatic test devices are carried out according to Gay-Lussac and Boyle- Mariotte depending on temperature.

Integrity tests at non-constant temperatures can therefore lead to erroneous results. Temperature changes during the measurement phase are corrected by a temperature measurement by means of a temperature sensor 38 on or in the filter system 14 during the integrity test and offset against the current pressure values. This makes measurements possible even at elevated and non-constant temperatures.

Example 3 Differential pressure holding test / diffusion test (see Fig. 10)

The pressure drop measured in a filter system 14 reflects the overall tightness of the system. It has so far not been possible to distinguish between housing leaks and defective filter elements 14 '. The inlet pressure is measured in line 12 via pressure sensor 22 in measuring device 1 .

By attaching a second pressure sensor 7 b by means of line 12 'to the outlet 46 of the filter system 14 , with valve VI and outlet valve V3 closed, a distinction can be made between system leaks and defective filter elements 14 ' by comparing the inlet and outlet pressure values or the diffusions calculated therefrom.

Eg:
Calculated diffusion at the input ( 12 ) - calculated diffusion at the output ( 12 ') - real diffusion value of the filter elements 14 '
Calculated diffusion at the inlet <calculated diffusion at the outlet - system leaks on the inlet side
Calculated diffusion at the inlet <calculated diffusion at the outlet = system-side leaks.

Example 4 Method for quasi-parallel multiplex measurement of different filter systems of different sizes and porosity (see Fig. 11)

The entire circuit is housed in an additional module housing 40 and enables the quasi-simultaneous testing of several filter systems of different sizes and porosity through a single test sequence.

Every outgoing test line P1. . . P6 contains a shut-off valve to V1. . . V6, a separate pressure sensor DS1. . . DS6 and a connection for the temperature sensor line TS1. . . TS6.

Another valve V7 is used to vent the system.

A built-in interface 41 takes over the control and transmission of the signals from and to the upstream main unit. In this case, both the main device 1 and an external computer can be used as the measuring device, if the pressure holding test is restricted.

Example 5 Method for inline integrity testing of hydrophobic filter elements without wetting liquid (water pressure test) - (see Fig. 12 and 13)

The conventional integrity check of membrane filter systems using the bubble point and / or diffusion or pressure maintenance test requires the filter elements 14 'to be completely wetted with a suitable liquid.

Accordingly, hydrophobic filters can be made with this method only check if the surface tension of the Benet tion liquid is smaller than that of the fil used termaterials (with PTFE e.g. <25 dynes / cm), otherwise none complete wetting takes place.

In practice, organic solvents such as Ethanol or isopropanol / water mixtures used what especially when using these systems as "sterile air filter "for tank and fermenter ventilation some disadvantages brings with it.

• - On the one hand there is the difficulty, the remaining rivers filter system after the integrity test lengthy and energy-intensive drying in the out built condition - partly under sterile conditions - like who need to completely remove it to an unung to prevent the passage of gas.
• - On the other hand, even the smallest remaining quantities are sufficient Alcohol to a partial hydrophilization and therefore a easier wettability with water (reduction of Water penetration pressure) causing what ver can lead to reduced gas flow rates.

There is also contamination by solvent vapors never be completely excluded.

The procedure described below is based on the be known property of hydrophobic filter systems, water-resistant to have an impact and is based on the high water penetration pressure of this filter.

The pressure value is measured, which is necessary to Push water through a hydrophobic filter.

This material and pore size dependent value is called "Water Penetration Value" labeled and characterized - similar to the boy ble-Point - the largest pores in a filter.

It was shown in corresponding series examinations however, that with a multiple test repeat the Pore structure z. B. the PTFE material at high WPV (<3.0 bar) gradually changed and the pore size slightly increases (pore dilation).

This method can also be used for liquid filters filtration should not always be used, as the rest vapors of the filter medium (e.g. solvents), which u. U. diffuse into the plastic parts of the filter elements, strongly influence the water penetration value.

Based on the water penetration pressure value of hydrophobic membranes, according to FIG. 12, after filling the filtration system 14 with water via the inlet 45, a transmembrane test pressure of approx. 70-80% of the water penetration pressure value is applied, and after a suitable stabilization time of 2-3 minutes, the pressure supply via the line 12 , 43 , 42 blocked and then the inlet pressure drop in the system caused by water penetration over a certain period of time (3-5 minutes) is measured. A sight glass 43 with buffer volume in the test line (compressed air) 12 , 42 enables the level in the filter system 14 to be checked. Excess water in the line 42 and sight glass 43 can be removed via the drain valve V5.

Fig. 13 shows schematically a practical test arrangement for inline testing of hydrophobic ventilation filters using the example of a fermenter ventilation. The same applies to the sterile ventilation of large containers. The test sequence takes place e.g. B. as follows:

Practical test execution

Depending on whether the integrity test before or after the steam Sterilization is to be avoided a drop in performance during subsequent commissioning took a certain order in the workflow hold.

Method A

• - integrity test
• - sterilization
• - Cooling phase 1 with compressed air
• - Commissioning of the plant

Method B

• - sterilization
• - Cooling down phase 2 with H2O
• - integrity test
• - steaming
• - Cooling phase 1 with compressed air
• - Commissioning of the plant

Description of the individual work steps business

When installing the air filter unit 14 , the "preferred" direction of filtration must be observed. The following generally applies to ventilation and exhaust:

• - Filtration with higher differential pressure in filtration direction
• - Filtration with lower differential pressure against the Filtration direction

Valve positions:
V1 closed
V2 closed
V3 opened
V4 closed
V5 closed
V6 opened
V7 closed
VP pressure setting: 3.5 bar

sterilization

The air filter unit must be sterilized - separately from the fermenter 44 or sterile tank - by inline vaporization.

For this:

• 1. Pull the measuring device hose 12 off the sight glass 43 .
• 2. Open steam supply V2.
  Valve positions:
  V1 closed
  V2 opened
  V3 closed
  V4 throttled
  V5 throttled
  V6 closed
  V7 throttled
  VP pressure setting: approx. 0.9 bar
• 3. Inline steaming: 30 min. With P inlet = 1.1 bar; P output = 1 bar
• 4. Steaming conditions: see relevant guidelines.

Cooling phase 1 with compressed air

The cooling phase 1 after steam sterilization is used faster system cooling and removed at the same time Residual moisture from the system. This makes a lei waste due to condensation film formation on the hydro phobic membrane effectively avoided.

• 1. Close the steam supply V2 and at the same time open the compressed air supply V3!
  Valve positions:
  V1 closed
  V2 opened
  V3 closed
  V4 throttled
  V5 throttled
  V6 closed
  V7 throttled
  VP pressure setting: approx. 0.9 bar
• 2. Plant for 15 minutes with compressed air at PE = 0.05 - 0.1 bar above Cool the VP pressure (Δp = 0.05 - 0.1 bar).

Cooling down phase 2 with H ₂ O (Only with integrity test after sterilization)

Cooling down phase 2 is used for forced cooling of the system after steam sterilization and before the integrity test.

• 1. Close the steam supply. Wait until the steam pressure drops to 0, then open the water supply.
  Valve positions:
  V1 throttled
  V2 closed
  V3 closed
  V4 opened
  V5 opened
  V6 closed
  V7 opened
  VP pressure setting: 0.9 bar
• 2. Plant at Δp = 0.3 - 0.5 bar from room temperature cool.
• 3. Empty the sight glass via V5 with the V4 open.

Steaming (Only after integrity test with previous Sterilization)

The sterile air filter system is right after the water pressure maintenance test put into operation, so there are reasons additionally reduced flow rates (condensate film formation on the membrane). By briefly steaming and on closing "blowing through" with compressed air (cooling phase 1) the formation of condensate film is effectively avoided.

• 1. Empty the system.
  Valve positions:
  V1 closed
  V2 closed
  V3 throttled
  V4 closed
  V5 throttled
  V6 closed
  V7 throttled
  VP pressure setting: 0.9 bar
• 2. Steaming over 5 minutes at 121 degrees C = 1 bar at the outlet.
  Valve positions:
  V1 closed
  V2 opened
  V3 closed
  V4 throttled
  V5 throttled
  V6 closed
  V7 throttled
  VP pressure setting: 0.9 bar
• 3. Initiate cooling phase 1.

Conducting the integrity test (water pressure holding test)

• 1. Fill the filter system 14 with water until water is visible in the glass 43 .
  Valve positions:
  V1 opened
  V2 closed
  V3 closed
  V4 opened
  V5 closed
  V6 closed
  V7 closed
  VP pressure setting: 0.9 bar
• 2. Drain residual water in sight glass 43 via V5.
• 3. Connect measuring device 1 .
• 4. Carry out an integrity test with the following test parameters:
  Test pressure: 2.5 bar (for 0.2 my filter) 1.5 bar (for 0.45 my filter)
  Stabilization time: 2-3 min
  Test time: 2-5 min.
  Valve positions:
  V1 closed
  V2 closed
  V3 closed
  V4 closed
  V5 closed
  V6 closed
  V7 closed
  VP pressure setting: 0.9 bar
• 5. Disconnect measuring device connection 12 after the test.

Determination of the limit data

The present physical laws at Exposure to hydrophobic membranes with water theoretically a pure yes / no statement in the evaluation expect the test results.

Corresponding laboratory tests have shown, however, that in practice - due to the high sensitivity of the measurement method on the one hand and the often unavoidable low Residual leakages in the system on the other hand - a limit value fixed laying is absolutely necessary.

This determination must be in accordance with the deposition performance of the filters (e.g. Bacteria Challenge test) and consider possible borderline cases.

The significance of this test method is that of the Compare diffusion tests, provided by the manufacturer corresponding comparison tests the correlation between Test result and the ability to separate (Bacteria challenge Test) has been ensured.  

The test method according to the invention for hydrophobic filter elements offers the following advantages over the conventional integrity test:

• 1. No wetting of the filter matrix, therefore no separate Drying in drying cabinet necessary.
• 2. High sensitivity, even with multiple systems, because the compressible, input-side net volume on one Minimum remains reduced, and so does the smallest Un tightness can still be reliably detected.
• 3. Possibility of measuring the integrity of large multiple sys systems with automatic test equipment.
• 4. Clear, reproducible test statement through high Test print.
• 5. No contamination from solvent vapors.
• 6. Better system tightness against water instead Compressed air.
• 7. Easier detection and localization of case Leakage through visual water leakage.
• 8. Possibility of the "in-situ" test without removing the filter apparatus.
• 9. By replacing alcohol with water as test fluids the otherwise necessary explosion protection is eliminated.

The possible uses of the measuring device and the measuring this extends methods.

Claims (19)

1. Measuring device as part of a test facility for filter systems, in which

• a) the filter system to be tested has at least one filter housing with an inlet and an outlet for fluid, between which at least one fluid-permeable filter element is arranged to separate,
• b) the measuring device with a power storage connection in a housing has a microprocessor-controlled, electrical integrated circuit with input, arithmetic and storage elements for test parameters and display and storage elements for measured values,
• c) they communicate with an electro-pneumatic control device which has an electromechanical pressure detection device for gas pressures, the pressure detection elements of which are connected via gas lines on the one hand to at least one fluid space of the filter housing which is separated from the filter element and on the other hand are connected to a gas source via controllable gas valves and
• d) the measuring device includes operating means, measuring means, storage means, computing means and circuit means with which the individual test parameters for the test method for bubble point determination, for the pressure maintenance test, for the diffusion test, for the system self-test and, if appropriate, further tests each as a menu program in the The measuring device can be entered and processed in such a way that only those parameters that are absolutely necessary for the selected test method are determined, additional parameters can be selected and called up individually or in blocks by input.

2. Measuring device according to claim 1, characterized in that means are provided for carrying out the system self-test, which identify, classify the filter system to be tested ( 14 ) and calibrate the measuring device ( 1 ) on the basis of the determined real measurement data. 3. Measuring device according to claim 1 and 2, characterized in that means are provided for carrying out the system self-test which carry out a comparison between the programmed test data and the operating pressure, the test pressure, the maximum bubble point and the results and / or recommendations in a user-friendly manner Show device display ( 2 '). 4. Measuring device according to claim 1 to 3, characterized in that means for internal device detection for existing residual pressure in the filter system ( 14 ) and the pneumatic system communicating therewith are available. 5. Measuring device according to claim 1 to 4, characterized in that means are provided, the automatic, internal calculation of the maximum allowed pressure drop based on entered diffusion values and test time as well as the measured system volume. 6. Measuring device according to claim 1 to 5, characterized in that means are provided, the automatic detection of the system volume carry out. 7. Measuring device according to claim 1 to 6, characterized in that for quasi-simultaneous checking of a plurality of filter systems, the measuring device ( 1 ) is supplemented by linked device modules (M1-Mn) which can be controlled by the main measuring device ( 1 ) according to the program. 8. Measuring device according to claim 1 to 7, characterized in that the additional modules (M1-Mn) have means for the simultaneous checking of filter systems ( 1/14 - 6/14 ) with filter elements of both the same pore size and filter elements of different pore size. 9. Measuring device according to claim 1 to 8, characterized in that the Measurement data acquisition by means of a printed document up to a pressure / diffusion curve to the bubble point as an additional evaluation aid for the Integrity check includes.   10. Measuring device according to claim 1 to 9, characterized in that the preselectable memory programs, test sequences and device functions can be called up by additional devices which can be connected to the measuring device ( 1 ) and / or device modules (M1-Mn). 11. Measuring device according to claim 1 to 10, characterized in that the measuring device for pressure measurement in the filter and pneumatic system is assigned at least one temperature sensor ( 38 ) for a temperature-compensated pressure measurement, the temperature sensor ( 38 ) on or in the filter system ( 14 ) is arranged. 12. Measuring device according to claim 11, characterized in that a first pressure sensor ( 22 ) in the pneumatic part of the measuring device ( 1 ) and a for the pressure measurement to carry out a differential pressure maintenance test or a differential diffusion test to differentiate between actual trans membrane diffusions and system leaks further pressure sensor (DS) are arranged at the output of the filter system ( 14 ) and are linked to the evaluation electronics. 13. Measuring device according to claim 8, characterized in that for quasi-parallel multiplex measurement of different filter systems of the same and / or different size and porosity, a module with a module housing ( 40 ), a test line assigned to each filter system (P1... P6) with a shut-off valve (V1. .. V6), a separate pressure sensor (DS1... DS6) and a connection for the temperature sensor line (TS1... TS6), with a further valve (V7) serving to vent the entire system and a built-in interface ( 41 ) the control and transmission of the signals from and to the upstream main measuring device ( 1 ) or a computer. 14. Measuring device according to claim 1 to 13, characterized in that a bidirectional interface for external control or query by HOST-Rech ner and is intended for additional device modules. 15. Measuring device according to claim 1 to 14, characterized in that a backflow of liquid into the measuring device is excluded by a liquid sensor ( 25 ) at the pneumatic output. 16. Test device for filter systems with a filter system ( 14 ) and a measuring device ( 1 ) according to claims 1 to 13. 17. Test method for determining individual or more defective filter elements ( 14 ') from a plurality of filter elements in a filter system ( 14 ) using a test device with a measuring device with the features a) -c) in claim 1, wherein the filter system to be tested ( 14 ), which is equipped with filter elements ( 14 ') wetted by a liquid test medium, is subjected to temperature-compensating at least two different test pressure gradients in a short time sequence after a short pressure stabilization phase, the measured values are compared in the measuring device ( 1 ) and from the Measured values of the quotient from total diffusion and pressure are formed and compared with target values. 18. Test method for carrying out a pressure maintenance test or diffusion test of a filter system ( 14 ), in particular with a plurality of filter elements ( 14 ') in a filter system ( 14 ) which is equipped with filter elements ( 14 ') wetted by a liquid test medium, using A test device with a measuring device with the features a) -c) in claim 1, characterized in that to differentiate between housing leaks on the one hand and defective filter elements ( 14 ') on the other hand, a pressure measurement is carried out both on the input side and on the output side and a comparison of the input values with the output values he follows. 19. Test method for the in-line integrity check hydrophobic filter elements in filter systems without wetting liquid, using a test device with a measuring device having the features a) -c) in claim 1, wherein the one or more hydrophobic filter (s) element (s) receiving the filter system (14) filled with water on the inlet side and then a pressure gradient of approximately 70% to 80% of the water penetration value typical for the filter elements is applied and after a stabilization phase the pressure drop in the filter system ( 14 ) is determined.