Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
  • G01M3/20—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material
  • G01M3/22—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material for pipes, cables or tubes; for pipe joints or seals; for valves; for welds; for containers, e.g. radiators
  • G01M3/222—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material for pipes, cables or tubes; for pipe joints or seals; for valves; for welds; for containers, e.g. radiators for tubes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
  • G01M3/20—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material
  • G01M3/22—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material for pipes, cables or tubes; for pipe joints or seals; for valves; for welds; for containers, e.g. radiators
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
  • G01M3/20—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
  • G01M3/20—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material
  • G01M3/202—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material using mass spectrometer detection systems
  • G01M3/205—Accessories or associated equipment; Pump constructions

Definitions

• the invention relates to a method for distinguishing a test gas emerging from a test gas of interfering gas in the environment of the specimen in the Schnuffel corner search.
• the invention further relates to a corresponding sniffer leak detector.
• a test specimen to be examined for a leak is filled with a test gas, for example helium or CO 2, while being pressurized to a pressure which is greater than the pressure in the external atmosphere surrounding the specimen.
• a test gas for example helium or CO 2
• the test gas then exits the test specimen and can be measured in the external environment of the test specimen.
• the external environment in particular the external specimen surface, is examined with a sniffer probe.
• the sniffer probe has a suction opening for sucking in a gas flow.
• the suction port is connected via a gas line path with a sensor and a gas flow generating gas pump.
• the sensor is designed to detect the beaugaspartial horrs the test gas in the sucked gas stream.
• Theticiangaspartial horrin is the proportion of the pressure of the test gas to the total pressure of the sucked and conveyed gas mixture.
• a typical test gas partial pressure sensor is a gas analyzer, such as a mass spectrometer / mass spectrometer or an infrared radiation absorption cell.
• the atmosphere surrounding the sample may have gas components which correspond to the test gas or which give a measurement signal which corresponds to the measurement signal of the test gas.
• These gas components are referred to herein as interference gas, because they distort the measurement result and interfere with the leak detection.
• the test specimen to be examined may be a heat exchanger filled with CO2 as a refrigerant.
• the CO2 serves as a test gas.
• CO2 in the form of breathing gas may occur to the person conducting the shot probe or as exhaust gas from an internal combustion engine.
• detection of the test gas via the infrared absorption method or mass spectroscopic detection may result in cross-sensitivities to similar or similar gases from the sample environment.
• the invention is based on the object of improving the differentiation of a test gas emerging from a leak in a test specimen from interfering gas in the surroundings of the test specimen during sniffing leak detection.
• test gas leak detector It is known from EP 0 750 738 Bl and DE 4 408 877 A1 in the case of a mass spectrometric test gas leak detector to modulate the gas flow through the gas inlet in order to suppress disturbances of the vacuum pump of the mass spectrometer.
• the described test gas leak detector is designed for vacuum operation and is not suitable as a sniffer leak detector for operation at atmospheric pressure.
• the total pressure of the gas at the gas detector is proportional to the ratio of the gas flow of the pumped gas and the pumping speed.
• the method according to the invention is defined by the features of claim 1.
• the device according to the invention is defined by the features of claim 8.
• the invention is based on the idea of periodically repeatedly varying the current strength of the gas stream sucked through the suction opening into the sniffer probe and thereby keeping the total pressure of the gas sucked in by the sniffer probe at the sensor as constant as possible. Variations of the total pressure of more than 10 percent should be avoided.
• the total pressure of the gas in the vicinity of the specimen in the area of the sniffer probe is approximately atmospheric pressure and the total pressure at the sensor should preferably be set to a value of at least 80 percent of the total pressure in the specimen environment in the area of the sniffer probe. In this area, the relationship between gas flow and gas pressure is approximately linear. With only negligible fluctuations in the total pressure at the sensor of a maximum of 10 percent, there is approximately the relationship described below between the test gas partial pressure measured with the sensor and the test gas concentration in the aspirated gas stream:
• Ppmfgas is the test gas partial pressure measured with the sensor
• Ptotai is the total pressure at the sensor
• Qi_eck is the gas flow through the leak (leak rate)
• QFIUSS is the flow rate of the gas at the sensor
• c 0 is the test gas concentration in the atmosphere surrounding the sample (interfering gas).
• the aspirated gas flow is thus examined as to whether the measured test gas partial pressure has a varying proportion whose mean amplitude is above a threshold value, ie not negligible is, and follows the varying of the sucked gas stream, that is, for example, that the frequency of the varying strigpartialdruckanteils the frequency of the varying current of the sucked gas stream corresponds. If a varying scholargaspartial horranteil is above the threshold, this serves as an indication of a leak in the DUT. The evaluation device then indicates that the device under test has a leak.
• the test gas concentration in the sucked gas stream is then the (from Interfering gas) test gas concentration Co in the atmosphere surrounding the sample.
• the smallest detectable leak should cause a partial pressure change which is higher than the unavoidable partial pressure variation from the test gas concentration in the surrounding atmosphere.
• the total pressure ptotai of the aspirated gas flow at the sensor should preferably be in the range between 90 and 110 percent of the total pressure in the atmosphere surrounding the test specimen in the region of the sniffer probe.
• This may be atmospheric pressure, that is, the device under test is exposed to the atmosphere and has in its interior a pressure which is above atmospheric pressure, while the sensor of the sniffer leak detector a total pressure in the range of 90 to 110 percent of the atmospheric pressure is maintained, which should also have negligible fluctuations, that is, vary less than 10 percent should .
• the measured signal of the current intensity of the aspirated gas stream can be modulated with a modulation frequency and phase.
• the demodulation of the modulated current signal can be carried out according to the principle of a lock-in amplifier with a defined frequency and phase reference to the modulation of the current signal. Frequency and phase reference means that the demodulation frequency and phase are a multiple of the frequency and the phase of the modulation.
• An additional comparison measurement can be carried out in which the current intensity of the aspirated gas stream is not varied periodically, but is kept constant in order to be able to determine the test gas partial pressure in the atmosphere surrounding the sample.
• the modulation frequency of the modulation of the current intensity of the aspirated gas flow is in the range of 1 Hz - 20 Hz and preferably in the range of 3 Hz - 10 Hz.
• the sniffer leak detector connects a gas line, which may be a gas line, the suction of the sniffer probe, the sensor and a gas pump.
• the sensor is designed to determine the beaugaspartial horrs of the test gas to be detected in the sucked gas stream.
• the gas pump generates the gas pressure necessary for the suction of the gas.
• a control device is designed to repeatedly vary the current intensity of the aspirated gas flow and to avoid fluctuations of the total pressure of the gas at the sensor of more than 10 percent.
• An evaluation device is designed to measure and to determine whether the test gas partial pressure of test gas contained in the aspirated gas stream, has a varying proportion whose average amplitude is above the previously described threshold and which follows the varying of the aspirated gas flow. This may be the case, for example, when the frequency of the varying portion of the test gas partial pressure corresponds to the frequency of the varied gas flow and the phase is in a fixed relationship to the phase of the gas flow modulation.
• the control device is preferably designed to set the total pressure of the aspirated gas flow at the sensor to a value in the range of about 80 percent and preferably in the range between 90-110 percent of the total pressure of the gas in the atmosphere surrounding the sample. In this area, the relationship between gas flow and gas pressure is approximately linear.
• the control device should be designed to determine the leakage gas flow in relation to a calibration with a known test leak.
• variations in the total pressure of the gas at the sensor can be suppressed or reduced by locating the sensor downstream of the gas pump.
• the gas line between intake and sensor may have a throttle.
• the control device may control the delivery rate or speed of the gas pump and / or change the conductance or the flow resistance of the throttle to reduce fluctuations in the gas flow.
• the restrictor may be a capillary, for example having a length in the range of about 2 cm to about 1 m and a maximum diameter of about 5 mm. However, longer capillaries are also conceivable.
• 1 is a schematic representation of a first embodiment
• 2 is a schematic representation of a second embodiment
• FIG. 5 shows a detail from FIG. 4,
• Fig. 7 shows a fifth embodiment
• Fig. 8 shows a sixth embodiment.
• the sniffer leak detector 10 of the three in Figs. 1 to 3 illustrated embodiments are each connected via a gas line 20 in a conventional manner with a sniffer probe 12 with a suction port 14.
• a gas pump 16 is arranged, which generates the atmosphere 23 for sucking in the gas from the surrounding the specimen 21.
• the gas line 20 further connects, in the form of a conventional gas line, the pump 16 to a sensor 18 located immediately downstream of the pump 16.
• the sensor 18 is configured to measure the partial pressure of the test gas in the aspirated gas stream.
• the sensor 18 may be, for example, an infrared absorption cuvette.
• the sensor 18 is configured to detect the test gas partial pressure at approximately atmospheric pressure or at approximately 90-110 percent of the atmospheric pressure.
• the scholargaspartialtik is the proportion of the test gas in the gas mixture of the sucked gas stream.
• the partial pressure of the test gas can not therefore with to be measured by a pressure sensor.
• a pressure sensor measures only the total pressure of a gas mixture.
• the gas line 20 carries the gas flow via an outlet 36 to atmosphere from.
• the gas line 20 may have a throttle 26.
• the throttle 26 may, as shown in Fig. 1 upstream of the gas pump 16 may be arranged.
• a controller 22 is electronically connected to control the gas pump 16.
• the control device 22 may be designed to control the rotational speed of the gas pump 16.
• Fig. 1 shows that the control device 22 may also be connected to the throttle 26 in order to change the conductance of the throttle 26.
• the control device can also be electronically connected to the sensor 18.
• An evaluation device 24 is connected electronically to the sensor 18 in order to process and evaluate the measurement signal.
• the evaluation device 24 is designed to determine whether the test gas partial pressure of the test gas contained in the intake gas flow has a varying proportion.
• the evaluation device 24 can check whether the varying proportion of the test gas partial pressure has an average amplitude which is above a threshold value.
• the evaluation device 24 can determine whether the varying proportion of educatial horrins follows the variation of the sucked gas stream. This is the case when the frequency of the varying strigpartialdruckanteils corresponds to the frequency of the gas flow varied or a multiple of this frequency.
• the evaluation device 24 may be connected to the control device 22.
• the controller 22 varies the current of the aspirated gas stream by varying the pump speed. This can take the form of a modulation, for example according to the principle of the lock-in amplifier respectively.
• the evaluation device 24 can perform an adjustment of the frequency of a varying strigtial horres with the modulation frequency of the sucked gas stream.
• the evaluation device 24 is also designed to determine the leakage flow of a known leak with a known leak rate as part of a calibration.
• the control device 22 of the first exemplary embodiment is additionally designed to set the total pressure of the aspirated gas flow in the region of the sensor 18 to at least approximately 90-110 percent of the total pressure of the gas in the atmosphere 23 surrounding the test object 21.
• the relationship between gas flow and gas pressure in this pressure range is approximately linear.
• the setting of the total pressure of the sucked gas flow at the sensor 18 can be effected via a control of the rotational speed of the gas pump 16 and / or via a control of the conductance of the throttle 26.
• the exemplary embodiments relate to sensors arranged directly downstream of the gas pump 16. In this arrangement, fluctuations in the total pressure of the gas at the sensor 18 are reduced. Alternatively, however, it is also possible to arrange the sensor 18 upstream of the gas pump 16, that is, between Schuffle probe 12 and gas pump 16.
• FIG. 2 differs from the exemplary embodiment according to FIG. 1 in that upstream of the gas pump 16, a valve 28 which can be controlled via the control device 22 is provided in order to change the line cross-section of the gas line path 20.
• the controllable valve 28 is disposed between the throttle 26 and the gas pump 16.
• the third embodiment differs from the second embodiment in that a bypass 30 bridges the gas line 20 between the sniffer probe 12 and the gas pump 16 and in particular the throttle 26.
• the bypass 30 is provided with a throttle 34 whose conductance is much greater than the conductance of the throttle 26.
• the bypass line 30 has a controllable valve 32, which is electronically connected to the control device 22 for its control. As the conductance of the valve 32 increases, the gas flow in the bridged gas passage 20 is reduced. In reducing the conductance of the valve 32, the gas flow in the bridged gas passage 20 is increased. In this way, with the help of the control device
• the current intensity of the sucked gas flow can be varied.
• the throttle 26 may be a capillary whose length is in the range of about 2 cm to about 10 cm and whose diameter is at most about 5 mm.
• Fign. 4 and 5 is the resulting gas flow in sccn (standard cubic centimeters per minute, cm 3 / min) on the vertical axis (ordinate) above the pressure in mbar (milibar) on the horizontal axis (abscissa) for different diameters of the capillary shaped throttle 26 applied.
• the applied on the horizontal axis pressure P 2 is the pressure P 2 within the gas line 20 downstream of the gas pump 16 in the region of the sensor 18.
• atmospheric pressure is understood to mean a pressure which can be in the range from about 900 mbar to about 1100.
• FIG. 4 shows the course of the gas flows occurring for different diameters d of the capillary of the throttle 26 in the range between 0 mbar and 1000 mbar.
• the length of the capillary is 5 cm.
• FIG. 5 shows the courses according to FIG. 4 in the pressure range between 950 and 1015 mbar. From Fig. 5 it can be seen that the relationship between gas flow and gas pressure is approximately linear when the pressure is at least 950 mbar. Therefore, it is advantageous according to the invention if the total pressure of the aspirated gas flow at the sensor 18 is set to a value in the range between approximately 90% and 110% of the total pressure in the surroundings of the test object 21. Of particular importance is in principle that the total pressure change is negligible and thus causes a large flow change.
• the flux changes by a factor of 2 from 100 sccn to 50 sccn.
• This aspect is different from the applications in the vacuum range, as described for example in DE 4408877 AI / EP 7050738 Bl. If the pressure Pi at the location of the sensor 18 is very low, such as in vacuum leak detectors, a change in pressure, for example from 0.1 mbar to 50 mbar, affects the gas flow only slightly.
• a typical leak in the test piece 21 can cause a leakage flow of gas from 1 ⁇ ⁇ 10 4 mbar l / s.
• the flow or current of the aspirated gas flow is modulated in the range between 120 sccm and 12 sccm with a modulation frequency of 6 Hz.
• the total pressure fluctuates with the modulation frequency between 1000 mbar and 950 mbar.
• the environmental concentration Co may be 400 ppm.
• the total pressure fluctuation of 50 mbar is comparatively high. Nevertheless, the partial pressure fluctuation caused by the total pressure fluctuation is small and thus negligible compared to the varying proportion of the partial pressure resulting from the flow modulation. In practice, the fluctuation of the total pressure is still significantly less than 50 mbar.
• the embodiment of FIG. 6 differs from the embodiment of FIG. 1 in that the gas pump 16 is not disposed between the throttle 26 and the sensor 18 in the gas passage 20, but in the gas passage 20 between the sniffer probe 12 and the throttle 26, that is, up
• FIG. 7 differs from the embodiment of FIG. 2 in that the gas pump 16 is not disposed between the valve 28 and the sensor 18, but also as in the embodiment of FIG. 6 upstream of the throttle 26th

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Examining Or Testing Airtightness (AREA)
• Sampling And Sample Adjustment (AREA)
• Other Investigation Or Analysis Of Materials By Electrical Means (AREA)

Priority Applications (9)

Applications Claiming Priority (2)

Publications (1)

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ID=63720695

Family Applications (1)

Country Status (9)

Families Citing this family (4)

Citations (7)

Family Cites Families (13)

• 2017
  • 2017-09-29 DE DE102017217374.2A patent/DE102017217374A1/de not_active Withdrawn
• 2018
  • 2018-09-28 CN CN201880062820.XA patent/CN111183344B/zh active Active
  • 2018-09-28 JP JP2020517997A patent/JP7150013B2/ja active Active
  • 2018-09-28 US US18/073,708 patent/USRE50099E1/en active Active
  • 2018-09-28 EP EP18780098.2A patent/EP3688438B1/de active Active
  • 2018-09-28 US US16/651,021 patent/US11199467B2/en not_active Ceased
  • 2018-09-28 CA CA3076439A patent/CA3076439A1/en active Pending
  • 2018-09-28 WO PCT/EP2018/076401 patent/WO2019063761A1/de not_active Ceased
  • 2018-09-28 MX MX2020003307A patent/MX2020003307A/es unknown
  • 2018-09-28 BR BR112020006319-3A patent/BR112020006319B1/pt active IP Right Grant

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