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Universal Filter
Holding Cell –>
(Shown with open-end
transparent adapter)
Different filter areas and
heights (packed beds)
can be accommodated
Holding Cell –>
(Shown with open-end
transparent adapter)
Different filter areas and
heights (packed beds)
can be accommodated
Applications:
High pressure filtering (w/ all metal parts)
Forward flow testing
Bubble point test
Pressure decay test
Evaluation of flow resistance to gas flow,
from dry to 100%RH flow
Envelope surface area analyzer
Capillary porometer
High pressure filtering (w/ all metal parts)
Forward flow testing
Bubble point test
Pressure decay test
Evaluation of flow resistance to gas flow,
from dry to 100%RH flow
Envelope surface area analyzer
Capillary porometer
Experimental setups using the Universal Filter Holding Cell
| Setup 1. Forward flow testing setup (capillary flow porometers and envelope surface area analyzers data) |
The forward flow testing setup employs the universal filter
holding cell and the HumiSys HF RH generator with pressure
transducer. In its simplest implementation, the rate of dry
flow of gas versus pressure difference across the sample
(filter or packed bed) allows for obtaining the data for gas
flow resistance for filters or determination of envelope
surface area of powders. Additionally, since the relative
humidity can be varied in a programmable way from dry to
fully wet conditions and back, the effect of moisture on the
flow resistance, caking effect, etc. can be studied.
The ability of varying the RH allows for validation of design
of capillary porometers that employ only the dry gas flow.
The experimental observation of different bubble point
pressure versus the rate of pressure buildup can be partially
attributed to drying of one surface of the filter by the dry gas.
The drying of the liquid in the interconnecting pores changes
the flow characteristics. In addition to the dry run, repeated
runs at different moisture levels of the carrier gas can yield
additional characterization data. Using different wetting liquids
and the full RH scan, specific interactions can be evaluated.
holding cell and the HumiSys HF RH generator with pressure
transducer. In its simplest implementation, the rate of dry
flow of gas versus pressure difference across the sample
(filter or packed bed) allows for obtaining the data for gas
flow resistance for filters or determination of envelope
surface area of powders. Additionally, since the relative
humidity can be varied in a programmable way from dry to
fully wet conditions and back, the effect of moisture on the
flow resistance, caking effect, etc. can be studied.
The ability of varying the RH allows for validation of design
of capillary porometers that employ only the dry gas flow.
The experimental observation of different bubble point
pressure versus the rate of pressure buildup can be partially
attributed to drying of one surface of the filter by the dry gas.
The drying of the liquid in the interconnecting pores changes
the flow characteristics. In addition to the dry run, repeated
runs at different moisture levels of the carrier gas can yield
additional characterization data. Using different wetting liquids
and the full RH scan, specific interactions can be evaluated.
| Setup 2. Packed beds and filter testing setup (capillary flow porometers, envelope surface area analyzers, and sorption data) |
The dual RH probes design of the HumiSys HF RH
generator and easy addition of sensors, e.g.
pressure transducer, allows for a simple
implementation of a testing station for packed beds
or filters. Knowing the rate of gas flow and
monitoring the RH probes data at a requested RH
level, the moisture holding capacity of a given
adsorbent can be measured as well as reversibility
of the process under dynamic flow conditions.
Additional experimental data vs. RH can be
obtained compared to envelope surface area
analyzers and capillary porometers.
generator and easy addition of sensors, e.g.
pressure transducer, allows for a simple
implementation of a testing station for packed beds
or filters. Knowing the rate of gas flow and
monitoring the RH probes data at a requested RH
level, the moisture holding capacity of a given
adsorbent can be measured as well as reversibility
of the process under dynamic flow conditions.
Additional experimental data vs. RH can be
obtained compared to envelope surface area
analyzers and capillary porometers.
| Adding Enhanced Bubble Point (active pore size determination) and Pressure Decay methods to the true density and moisture analysis capabilities of the HumiPyc |
The unique design of the HumiPyc - gas (helium nitrogen, air) pycnometer and
its closure of the sample chamber allow for additional usage for testing of
packed beds and filter integrity (bubble point, pressure decay methods). One of
the assemblies depicted on the photo below (with a paper filter inside) has
transparent upper part for visual observation of the bubbles. The outlet from the
chamber can be connected to a flow meter to implement additional capabilities
(forward flow method, capillary porometer).
its closure of the sample chamber allow for additional usage for testing of
packed beds and filter integrity (bubble point, pressure decay methods). One of
the assemblies depicted on the photo below (with a paper filter inside) has
transparent upper part for visual observation of the bubbles. The outlet from the
chamber can be connected to a flow meter to implement additional capabilities
(forward flow method, capillary porometer).
Please contact us at support@instruquest.com
regarding inquiries for any application-specific
requirements of the Bubble Point and Pressure
Decay analyzer.
regarding inquiries for any application-specific
requirements of the Bubble Point and Pressure
Decay analyzer.
The bubble point method is a commonly used
technique for determination of the largest pore
(s), so-called active pores, in a given filter
(membrane). Experimentally, the bubble-point
instrument measures the pressure needed to
blow gas (typically air) through the liquid filled
medium. From the theory of capillarity and
using an ideal cylindrical approximation of real
pores the transitional pressure is reported as
the pore diameter by employing this simple
formula:
d = 4σcosθ/p, where
d - (equivalent) pore diameter
σ - surface tension of the liquid
θ - liquid-solid contact angle
p - pressure at the first bubble(s) appearance
The nominator of the equation can be
multiplied by shape/tortuosity factors , e.g. the
ASTM F316-86 method use a capillary
constant of 0.715 value
technique for determination of the largest pore
(s), so-called active pores, in a given filter
(membrane). Experimentally, the bubble-point
instrument measures the pressure needed to
blow gas (typically air) through the liquid filled
medium. From the theory of capillarity and
using an ideal cylindrical approximation of real
pores the transitional pressure is reported as
the pore diameter by employing this simple
formula:
d = 4σcosθ/p, where
d - (equivalent) pore diameter
σ - surface tension of the liquid
θ - liquid-solid contact angle
p - pressure at the first bubble(s) appearance
The nominator of the equation can be
multiplied by shape/tortuosity factors , e.g. the
ASTM F316-86 method use a capillary
constant of 0.715 value
- Pore diameter range from micrometers to millimeters
- Enhanced bubble point method
- Pressure decay (pressure drop) method
- Integration of density, pore analysis, and gas transport properties
- Programmable pressure rate increase
- High performance R&D tool for product testing and development
- Open-design for easy customization to address specific requirements
- Excellent resolution for large pore sizes
- Temperature measurements of the externally located sample holder
- Minimal added cost compared to purchasing of a separate bubble
point or pressure decay tester
- Enhanced bubble point method
- Pressure decay (pressure drop) method
- Integration of density, pore analysis, and gas transport properties
- Programmable pressure rate increase
- High performance R&D tool for product testing and development
- Open-design for easy customization to address specific requirements
- Excellent resolution for large pore sizes
- Temperature measurements of the externally located sample holder
- Minimal added cost compared to purchasing of a separate bubble
point or pressure decay tester
| Despite its conceptual simplicity, the bubble-point test must be implemented properly as the results depend on the rate of pressure increase, detection technique, liquid selection, temperature, and a particular instrumentation design (excluding the properties of the sample in question). Using the computerized and programmable pressure increase rate as well as the software and hardware capabilities of the HumiPyc, the bubble point technique can be enhanced to allow for determination not only the largest pore size but also the consecutive pore sizes that become active when the pressure is increased (very slowly). The example of the pressure value determinations for a filtering material is shown below. |
| Before the bulk flow of gas appears on one side of the wetted sample in form of bubbles while the pressure is raised slowly, the diffusional mode of the gas transport takes place. In the pressure decay or pressure drop test, the pressure is raised to the vicinity of bubble point pressure and the flow of gas is cut off. From the rate of pressure drop versus time and the known initial volume of the gas, additional gas transport properties of the sample can be deduced. After initial fast decay, the pressure level tends to establish a plateau that stays relatively constant and the difference between the pressures on both sides of the sample can be used as another characterization parameter. |
An example of multiple pore sizes determination using slow pressure
increase and high resolution pressure transducer detection technique
increase and high resolution pressure transducer detection technique
Addition of the Bubble Point and Pressure
Decay tests capabilities to the HumiPyc
requires only optional hardware for the sample
holding as the progressive gas dosing, all
hardware, and the high resolution (24-bit) data
acquisition are already a part of the gas
pycnometer. The sample can be measured
inside the temperature-controlled compartment
of the HumiPyc or it can be measured external
to the instrument. The external location of the
sample holding hardware allows for larger
spectrum of samples to be measured and
facilitates visual determination of the onset of
bubbles formation. The increase in gas pressure
can be done manually or automatically and the
experimental data are graphed and recorded.
Considering the vast diversity of samples, their
affinity towards the wetting liquid, and the
pressure spectrum employed, it is
recommended to combine the visual
observations and the automatically obtained
data for the most reliable results of the bubble
point method.
Decay tests capabilities to the HumiPyc
requires only optional hardware for the sample
holding as the progressive gas dosing, all
hardware, and the high resolution (24-bit) data
acquisition are already a part of the gas
pycnometer. The sample can be measured
inside the temperature-controlled compartment
of the HumiPyc or it can be measured external
to the instrument. The external location of the
sample holding hardware allows for larger
spectrum of samples to be measured and
facilitates visual determination of the onset of
bubbles formation. The increase in gas pressure
can be done manually or automatically and the
experimental data are graphed and recorded.
Considering the vast diversity of samples, their
affinity towards the wetting liquid, and the
pressure spectrum employed, it is
recommended to combine the visual
observations and the automatically obtained
data for the most reliable results of the bubble
point method.
An example of bubble point determination and pressure decay test for a
high quality filter using water. For smaller size pores, the very slow
pressure buildup is more essential in correct determination of the bubble
point pressure.
high quality filter using water. For smaller size pores, the very slow
pressure buildup is more essential in correct determination of the bubble
point pressure.
To find out more about HumiPyc capabilities as filter integrity tester,
please read this application note:
Combining the Enhanced Bubble Point and Pressure Decay methods in
characterization of micro-filtration products using the HumiPyc.
please read this application note:
Combining the Enhanced Bubble Point and Pressure Decay methods in
characterization of micro-filtration products using the HumiPyc.
For additional product information and sales inquiries, please contact us at :
E-mail: info@instruquest.com | support@instruquest.com
| Filter Integrity Testing Products |
2004 -2010 Copyright © InstruQuest, Inc. All rights reserved.
Advantages
The Bubble Point Method
The Pressure Decay Test
HumiPyc – Bubble Point and
Pressure Decay Analyzer
Pressure Decay Analyzer
| InstruQuest Inc. Scientific Instruments R&D |
