RUGGED TARGET-ANALYTE PERMEATION TESTING INSTRUMENT EMPLOYING A CONSOLIDATING BLOCK MANIFOLD

Abstract

A target-analyte permeation testing instrument (10) characterized by a block manifold (100) retaining the testing cells (70n) of the instrument (10).

Description

BACKGROUND

Permeation instruments are used to measure the transmission rate of a target analyte, such as oxygen, carbon dioxide or water vapor, through various samples, such as membranes, films, envelopes, bottles, packages, containers, etc. (hereinafter collectively referenced as “test films” for convenience). Typical test films are polymeric packaging films such as those constructed from low density polyethylene (LDPE), high density polyethylene (HDPE), oriented polypropylene (OPP), polyethylene terepthalate (PET), polyvinylidene chrloride (PVTDC), etc. Typically, the film to be tested is positioned within a test chamber to sealing separate the chamber into first and second chambers. The first chamber (commonly referenced as the driving or analyte chamber) is filled with a gas containing a known concentration of the target analyte (commonly referenced as a driving gas). The second chamber (commonly referenced as the sensing chamber) is flushed with an inert gas (commonly referenced as a carrier gas) to remove any target analyte from the cell. A sensor for the target analyte is placed in fluid communication with the sensing chamber for detecting the presence of target analyte that has migrated into the sensing chamber from the driving chamber through the test film. Exemplary permeation instruments for measuring the transmission rate of oxygen (O₂), carbon dioxide (CO₂) and water vapor (H₂O) through test films are commercially available from Mocon, Inc. of Minneapolis, Minn. under the designations OXTRAN, PERMATRAN-C and PERMATRAN-W, respectively.

Permeation instruments are being used more often to measure ever decreasing concentrations of target-analyte, into the ppm or even ppb range, and are therefore extremely sensitive to even minute atmospheric contamination of the fluids used in the instrument. Permeation instruments employ an extensive network of fluid interconnections with numerous valves to achieve the desired choreographed flow of driving and carrier gas through the instrument, especially when the instrument employs a plurality of testing cells in fluid communication with a single common target-analyte sensor. Each fitting in the fluid transfer system of the instrument is a potential source of contamination as atmospheric oxygen, carbon dioxide and water vapor leak around or permeate through the seals on the fittings, especially as the seals on the fittings loosen over time.

Accordingly, a substantial need exists for a permeation instrument capable near elimination of atmospheric-induced contamination of the driving and carrier gases flowing through the instrument throughout the lifespan of the instrument.

SUMMARY OF THE INVENTION

The invention is a target-analyte permeation testing instrument characterized by a block manifold. The instrument has a target-analyte sensor and a plurality of test cells for measuring target-analyte permeation rate of a test film. Each test cell defines a testing chamber and is operable for retaining a test film to sealingly divide the testing chamber into a driving chamber and a sensing chamber. The block manifold is fixed to the plurality of cells and has a plurality of channels in fluid communication with the testing chamber of each cell, a pressurized source of driving gas, a pressurized source of inert gas, and a target-analyte sensor. The plurality of channels are configured and arranged to selectively carry driving gas from the pressurized source of driving gas to the driving chamber of each cell, carry driving gas from the driving chamber of each cell to a driving gas exit port in the manifold, selectively carry inert gas from the pressurized source of inert gas to the sensing chamber of each cell, and selectively carry inert gas from the sensing chamber of each cell to the target-analyte sensor.

The block manifold can include a refillable first water reservoir in selective fluid communication with the source of driving gas and in fluid communication with the driving chamber of each cell, and a second refillable water reservoir in selective fluid communication with the source of inert gas and in fluid communication with the sensing chamber of each cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plumbing diagram of one embodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Nomenclature Table
10       Target-Analyte Permeation Testing Instrument
20A      Test Gas RH Control Valve
20B      Carrier Gas RH Control Valve
30Bwet   Catalyst Chamber in Wet Carrier Gas Line
30Bdry   Catalyst Chamber in Dry Carrier Gas Line
40Awet   Particle Filter in Wet Test Gas Line
40Adry   Particle Filter in Dry Test Gas Line
40Bwet   Particle Filter in Wet Carrier Gas Line
40Bdry   Particle Filter in Dry Carrier Gas Line
50A      Water Reservoir for Test Gas
50B      Water Reservoir for Carrier Gas
60n      Capillary Restrictors
601A     Capillary Restrictor for Test Gas Channel to First
         Test Cell
602A     Capillary Restrictor for Test Gas Channel to Second
         Test Cell
601B     Capillary Restrictor for Carrier Gas Channel to First
         Test Cell
602B     Capillary Restrictor for Carrier Gas Channel to Second
         Test Cell
609B     Capillary Restrictor for Carrier Gas Channel to Rezero
         Valve
70n      Testing Cells
70nA     Driving Chamber of Test Cell n
70nB     Sensing Chamber of Test Cell n
70nAx    Exhaust from Driving Chamber of Test Cell n
701      First Testing Cells
701A     Driving Chamber of First Test Cell
701Ax    Exhaust from Driving Chamber of First Test Cell
701B     Sensing Chamber of First Test Cell
702      Second Testing Cells
702A     Driving Chamber of Second Test Cell
702Ax    Exhaust from Driving Chamber of Second Test Cell
702B     Sensing Chamber of Second Test Cell
80nB     Carrier Gas Sensing Chamber Exit Valve for Testing Cell n
801B     First Test Cell Carrier Gas Exit Valve
801Bx    Exhaust from Sensing Chamber of First Test Cell
802B     Second Test Cell Carrier Gas Exit Valve
802Bx    Exhaust from Sensing Chamber of Second Test Cell
88B      Cell Selector Channel Conditioning Valve
88Bx     Exhaust from Cell Selector Channel Conditioning Valve
89B      Rezero Valve
89Bx     Exhaust from Rezero Valve
100      Block Manifold
101Awet  Test Gas Water Reservoir Inlet Port
101Adry  Test Gas Water Reservoir Bypass Inlet Port
101Bwet  Carrier Gas Water Reservoir Inlet Port
101Bdry  Carrier Gas Water Reservoir Bypass Inlet Port
102      Carrier Gas Outlet Port to Sensor
200      Target-Analyte Sensor
210      Sensor Exhaust Valve
300n     Gas Flow Line n
3000Awet Test Gas Water Reservoir Inlet Line
3000Adry Test Gas Water Reservoir Bypass Inlet Line
3000Bwet Carrier Gas Water Reservoir Inlet Line
3000Bdry Carrier Gas Water Reservoir Bypass Inlet Line
3001Ain  Test Gas First Testing Cell Inlet Line
3001Bin  Carrier Gas First Testing Cell Inlet Line
3002Ain  Test Gas Second Testing Cell Inlet Line
3002Bin  Carrier Gas Second Testing Cell Inlet Line
300nBout Carrier Gas Outlet Line for Testing Cell n
3001Bout Carrier Gas First Testing Cell Outlet Line
3002Bout Carrier Gas Second Testing Cell Outlet Line
3005     Shared Carrier Gas Testing Cell Outlet Line
3009B    Carrier Gas Rezero Line
A        Driving or Test Gas Source
B        Inert or Carrier Gas Source
F        Test Film

DESCRIPTION

Referring generally to FIG. 1, the invention is a target-analyte permeation testing instrument 10 characterized by a block manifold 100, preferably a solid block cast metal manifold 100 into which the appropriate channels and compartments are formed. The instrument 10 has a target-analyte sensor 200 and a plurality of test cells 70_n for measuring target-analyte permeation rate of test films F_n. Each test cell 70_n defines a testing chamber and is operable for retaining a test film F to sealingly divide the testing chamber into a driving chamber 70_nA and a sensing chamber 70_nB. The cells 70_n are secured to the block manifold 100. The block manifold 100 has a plurality of channels 300_n in fluid communication with the testing chamber of each cell 70_n, a pressurized source of driving gas A, a pressurized source of inert gas B, and a target-analyte sensor 200. The plurality of channels 300_n are configured and arranged to selectively carry driving gas from the pressurized source of driving gas A to the driving chamber 70_nA of each cell 70_n, carry driving gas from the driving chamber 70_nA of each cell 70_n to a driving gas exit port 70_nAx in the manifold 100, selectively carry inert gas from the pressurized source of inert gas B to the sensing chamber 70_nB of each cell 70_n, and selectively carry inert gas from the sensing chamber 70_nB of each cell 70_n to a the target-analyte sensor 200.

The block manifold 100 can include a refillable first water reservoir 50A in selective fluid communication with the source of driving gas A and in fluid communication with the driving chamber 70_nA of each cell 70_n, and a second refillable water reservoir 50B in selective fluid communication with the source of inert gas B and in fluid communication with the sensing chamber 70_nB of each cell 70_n.

An exemplary two-cell embodiment of the invention 10 is depicted in FIG. 1. The permeation testing instrument 10 preferably includes humidification systems for each of the test gas and carrier gas, such as described in U.S. Pat. Nos. 7,578,208 and 7,908,936, the disclosures of which are hereby incorporated by reference.

A source of dry test gas A fluidly communicates with a first humidification system that includes a wet line 300₀A_wet in fluid communication with a water reservoir 50A and a dry line 300₀A_dry that bypasses the water reservoir 50A. A test gas RH control valve 20A controls flow of test gas through the wet line 300₀A_wet and dry line 300₀A_dry according to a duty cycle for achieving the desired humidification level of the test gas.

The test gas wet line 300₀A_wet enters the block manifold 100 at inlet port 101A_wet. The test gas dry line 300₀A_dry enters the block manifold 100 at inlet port 101A_dry.

Upon exiting the water reservoir 50A, humidified test gas in the wet line 300₀A_wet is combined with dry test gas in the dry line 300₀A_dry and the combined test gas directed by test gas inlet lines 300₁A and 300₂A to the driving chambers 70₁A and 70₂A in the first testing cell 70₁ and second testing cell 70₂ respectively. Test gas flows through and exits each of the driving chambers 70₁A and 70₂A through an outlet port (unnumbered) and is vented from the block manifold at vent ports 70₁Ax and 70₂Ax respectively.

Particle filters 40A_wet and 40A_dry are preferably provided in the test gas wet line 300₀A_wet and test gas dry line 300₀A_dry respectively, for removing any entrained particulate matter from the test gas before it enters the block manifold 100.

In a similar fashion, a source of dry carrier gas B fluidly communicates with a second humidification system that includes a wet line 300₀B_wet in fluid communication with a water reservoir 50B and a dry line 300₀B_dry that bypasses the water reservoir 50B. A carrier gas RH control valve 20B controls flow of carrier gas through the wet line 300₀B_wet and dry line 300₀B_dry according to a duty cycle for achieving the desired humidification level of the carrier gas.

The carrier gas wet line 300₀B_wet enters the block manifold 100 at inlet port 101B_wet. The carrier gas dry line 300₀B_dry enters the block manifold 100 at inlet port 101B_dry.

Upon exiting the water reservoir 50B, humidified carrier gas in the wet line 300₀B_wet is combined with dry carrier gas in the dry line 300₀B_dry and the combined carrier gas directed by carrier gas inlet lines 300₁B and 300₂B to the sensing chambers 70₁B and 70₂B in the first testing cell 70₁ and second testing cell 70₂ respectively. Carrier gas flows through and exits each of the sensing chambers 70₁B and 70₂B through an outlet port (unnumbered) and is directed by dedicated outlet channels 300₁B_out and 300₂B_out respectively, to a common channel 300₅ in fluid communication with a target-analyte sensor 200 located external to the block manifold 100.

Common channel 300₅ exits the block manifold 100 at outlet port 102.

Particle filters 40B_wet and 40B_dry are preferably provided in the carrier gas wet line 300₀B_wet and carrier gas dry line 300₀B_dry respectively, for removing any entrained particulate matter from the carrier gas before it enters the block manifold 100.

Target-analyte catalytic converters 30B_wet and 30B_dry are preferably provided in the carrier gas wet line 300₀B_wet and carrier gas dry line 300₀B_dry respectively, for converting any target-analyte in the carrier gas (e.g., O₂) to a molecular species (e.g., H₂O when the target analyte is O₂) that will not be detected by the target-analyte sensor 200.

Capillary restrictors 60₁A, 60₂A, 60₁B and 60₂B are preferably provided in the test gas inlet lines 300₁A and 300₂A, and carrier gas inlet lines 300₁B and 300₂B respectively, for facilitating a consistent and equal flow of gas into the driving chambers 70₁A and 70₂A of the testing cells 70₁ and 70₂, and the sensing chambers 70₁B and 70₂B of the testing cells 70₁ and 70₂ respectively. The capillary restrictors 60_n are preferably side mounted onto the block manifold 100.

Valves 80₁B and 80₂B are provided in the dedicated outlet channels 300₁B_out and 300₂B_out respectively, for selectively and mutually exclusively allowing passage of carrier gas, containing any target-analyte that has permeated through the test film F, from each of the sensing chambers 70₁B and 70₂B into sensing engagement with the sensor 200. When closed, the valves 80₁B and 80₂B vent carrier gas, containing any target-analyte that has permeated through the test film F, to atmosphere through vent ports 80₁Bx and 80₂Bx in the manifold 100. The valves 80_nB are preferably side mounted onto the block manifold 100.

The instrument 10 depicted in FIG. 1 includes an optional channel conditioning feature. Permeation testing instruments 10 employ a very low mass flow through rate through the gas flow lines 300n of the instrument 10 to limit the creation of any pressure differentials in the instrument 10 that could impact humidification of the test and/or carrier gases or create a pressure-induced driving force across a test film F. This low mass flow rate through the instrument 10 imposes a significant time delay between measurements from different testing cells 70_n as both the “stale” carrier gas contained in the length of the testing cell outlet line 300_nB_out for the upcoming testing cell 70_n to be measured and the “inapplicable” carrier gas contained in the length of the shared outlet line 300₅ from the previously measured testing cell 70_n is flushed from the lines and replaced with fresh carrier gas, containing any target-analyte that has permeated through the test film F, from the upcoming testing cell 70_n. A channel conditioning feature employs a cell selector channel conditioning valve 88B in the shared outlet line 300₅ for allowing, in coordination with opening and closing of valves 80_nB for the upcoming and previous testing cells 70_n, for advanced venting of “stale” carrier gas contained in the length of the outlet line 300_nB_out for the upcoming testing cell 70_n. The cell selector channel conditioning valve 88B is operable as between a flow-through state, in which carrier gas is directed to the sensor 200, and a vent state, in which carrier gas is vented to atmosphere through a vent port 88Bx in the block manifold 100. The cell selector channel conditioning valve 88B is preferably side mounted to the block manifold 100.

The instrument 10 depicted in FIG. 1 includes an optional rezero feature. Rezero is a method of measuring residual target-analyte contained in the carrier gas during performance of testing that includes the steps of bypassing the test cell(s) 70_n and directly measuring the carrier gas target-analyte level, which is then subtracted from the measured transmission rate of the target-analyte level for each sample.

The rezero feature includes a rezero line 300₉B upstream from the testing cells 70_n for bypassing the testing cells 70_n and carrying carrier gas directly to the sensor 200. A rezero valve 89B is provided in the rezero line 300₉B for selectively directing carrier gas to the sensor 200 or venting carrier gas from the block manifold 100 at vent port 89Bx. The rezero valve 89B is preferably side mounted to the block manifold 100.

A capillary restrictor 60₉B is preferably provided in the carrier gas rezero line 300₉B for facilitating a consistent and equal flow of carrier gas into the sensing chambers 70₁B and 70₂B of the testing cells 70₁ and 70₂ respectively. The capillary restrictor 60₉B is, as with the other capillary restrictors, preferably side mounted onto the block manifold 100.

The sensor 200 is selected to measure the appropriate target-analyte (e.g., oxygen (O₂), carbon dioxide (CO₂) or water vapor (H₂O)). Selection of a suitable sensor 200 is well within the knowledge and expertise of a person having routine skill in the art. The sensor 200 is preferably a coulox sensor and is equipped with an exhaust valve 210 for preventing atmospheric contamination of the sensor when there is no flow of carrier gas to the sensor 200.

Claims

1. A target-analyte permeation testing instrument for measuring target-analyte permeation rate of a test film in test cell, the instrument having a target-analyte sensor and a plurality of test cells each defining a testing chamber with each test cell operable for retaining a test film to sealingly divide the testing chamber into a driving chamber and a sensing chamber, the target-analyte permeation testing instrument characterized by a block manifold (-) fixed to the plurality of cells, and (-) having a plurality of channels in fluid communication with the testing chamber of each cell, a pressurized source of driving gas, a pressurized source of inert gas, and the target-analyte sensor, wherein the plurality of channels are configured and arranged to (i) selectively carry driving gas from the pressurized source of driving gas to the driving chamber of each cell, (ii) carry driving gas from the driving chamber of each cell to a driving gas exit port in the manifold, (iii) selectively carry inert gas from the pressurized source of inert gas to the sensing chamber of each cell, and (iv) selectively carry inert gas from the sensing chamber of each cell to the target-analyte sensor.

2. The target-analyte permeation testing instrument of claim 1 wherein the block manifold further includes a refillable first water reservoir in selective fluid communication with the source of driving gas and in fluid communication with the driving chamber of each cell, and a second refillable water reservoir in selective fluid communication with the source of inert gas and in fluid communication with the sensing chamber of each cell.

3. The target-analyte permeation testing instrument of claim 1 wherein the block manifold is constructed from a single unitary metal block.

4. The target-analyte permeation testing instrument of claim 1 wherein the channels in fluid communication with the pressurized source of driving gas and the driving chamber of each cell are in fluid communication with at least one block mounted valve operable for effecting selective delivery of driving gas to the driving chambers of the cells.

5. The target-analyte permeation testing instrument of claim 1 wherein the channels in fluid communication with the pressurized source of inert gas and the sensing chamber of each cell are in fluid communication with at least one block mounted valve operable for effecting selective delivery of inert gas to the sensing chambers of the cells.

6. The target-analyte permeation testing instrument of claim 1 wherein the channels in fluid communication with the sensing chamber of each cell and the target-analyte sensor are in fluid communication with at least one block mounted valve operable for effecting selective delivery of inert gas from the sensing chambers of the cells to the target-analyte sensor.