U.S. patent application number 12/245469 was filed with the patent office on 2009-01-29 for leak characterization apparatuses and methods for fluid storage containers.
This patent application is currently assigned to Matheson Tri-Gas, Inc.. Invention is credited to Stuart Muller, Robert Torres, JR..
Application Number | 20090025455 12/245469 |
Document ID | / |
Family ID | 39168217 |
Filed Date | 2009-01-29 |
United States Patent
Application |
20090025455 |
Kind Code |
A1 |
Muller; Stuart ; et
al. |
January 29, 2009 |
Leak Characterization Apparatuses and Methods for Fluid Storage
Containers
Abstract
According to the invention, an apparatus to characterize leaks
in a fluid storage container is disclosed. The apparatus may
include a valve coupler, a gas manifold and a processor. The valve
coupler may couple the apparatus with a closed valve on the fluid
storage container. The gas manifold may be coupled with the valve
coupler and may include a first branch connected with a gas
monitoring device. The gas monitoring device may scan for a
plurality of gases that may be emitted by the closed valve of the
fluid storage container. The processor may be operable to receive
gas monitoring device data representing masses for one or more of
the plurality of gases detected by the monitor.
Inventors: |
Muller; Stuart; (Rowley,
MA) ; Torres, JR.; Robert; (Parker, CO) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER, EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
Matheson Tri-Gas, Inc.
Longmont
CO
|
Family ID: |
39168217 |
Appl. No.: |
12/245469 |
Filed: |
October 3, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11470868 |
Sep 7, 2006 |
|
|
|
12245469 |
|
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Current U.S.
Class: |
73/49.2 |
Current CPC
Class: |
G01M 3/229 20130101 |
Class at
Publication: |
73/49.2 |
International
Class: |
G01M 3/04 20060101
G01M003/04 |
Claims
1. An apparatus to characterize leaks in a fluid storage container,
the apparatus comprising: a valve coupler to couple the apparatus
with a closed valve on the fluid storage container; a gas manifold
coupled with the valve coupler, wherein the gas manifold comprises
a first branch connected with a gas monitoring device, wherein the
gas monitoring device scans for a plurality of gases that may be
emitted by the closed valve of the fluid storage container; and an
indicator device operable to communicate a leak has been detected
based at in part on gas monitoring device data.
2. The leak characterization apparatus of claim 1, further
comprising a processor operable to receive gas monitoring device
data representing masses for one or more of the plurality of gases
detected by the monitor.
3. The leak characterization apparatus of claim 1, wherein the gas
monitoring device comprises a mass spectrometer that scans a mass
range from about 1 atomic mass unit to about 400 atomic mass
units.
4. The leak characterization apparatus of claim 2, wherein the
processor is operable to generate a mass spectrum from the data
representing masses for one or more of the plurality of gases
detected by the monitor.
5. The leak characterization apparatus of claim 4, wherein the
processor is in communication with a display that can display the
mass spectrum.
6. The leak characterization apparatus of claim 2, wherein the
processor is operable to calculate leak rates for one or more of
the plurality of gases.
7. The leak characterization apparatus of claim 6, wherein the
processor is in communication with a display that can display the
leak rates for the one or more gases.
8. The leak characterization apparatus of claim 7, wherein the leak
rates are displayed in units of cubic centimeters per second.
9. The leak characterization apparatus of claim 1, wherein the gas
manifold further comprises a second branch connected with a
manifold pump to evacuate the manifold, and a third branch
connected with a pressure measuring device to measure the gas
pressure in the manifold.
10. The leak characterization apparatus of claim 1, wherein the
fluid storage container comprises a high-pressure gas cylinder.
11. The leak characterization apparatus of claim 1, wherein the
valve coupler comprises an outlet connector for a compressed gas
valve.
12. A method to characterize a leak in a fluid storage container,
the method comprising: connecting a valve on the fluid storage
container with a leak characterization apparatus comprising a gas
manifold, wherein the manifold is in fluid communication with a
valve coupler that connects with the valve on the container and a
gas monitoring device; evacuating the gas manifold; scanning the
evacuated manifold with the gas monitoring device for a plurality
of gases that may be emitted by the fluid storage container; and
generating leak characterization data about one or more of the
plurality of gases.
13. The leak characterization method of claim 12, wherein the
method further comprises sending the leak characterization data to
a processor operable to calculate leak flow rates for one or more
of the plurality gases.
14. The leak characterization method of claim 13, wherein the
method further comprises displaying the leak flow rates for the one
or more gases on a display in electronic communication with the
processor.
15. The leak characterization method of claim 12, wherein the
method further comprises pressurizing the fluid storage container
with a leak testing fluid before connecting the container with the
leak characterization apparatus.
16. The leak characterization method of claim 15, wherein the leak
testing fluid comprises krypton, neon, xenon, argon, hydrogen,
oxygen, helium, nitrogen, ammonia, arsine, phosphine, silane,
acetylene, a halogen, a hydrogen halide, a boron halide; a hydrogen
chloride, hydrogen bromide, chlorine, tungsten hexafluoride,
hydrogen fluoride, carbon dioxide, nitrous oxide, nitrogen dioxide,
dicholorosilane, trichlorosilane, carbonyl sulfide, sulfur
hexafluoride, phosphine, arsine, disilane, chlorine trifluoride,
boron trichloride, halogenated compounds, hydrocarbons, amines, or
anorganometallic precursors.
17. The leak characterization method of claim 12, wherein the gas
monitoring device scans a mass range from about 1 atomic mass unit
to about 400 atomic mass units.
18. The leak characterization method of claim 12, wherein the leak
characterization data comprises a mass spectrum of the plurality of
gases emitted by the fluid storage container.
19. An apparatus to characterize leaks in a fluid storage
container, the apparatus comprising: a valve coupler to couple the
apparatus with a closed valve on the fluid storage container; a gas
manifold coupled with the valve coupler, wherein the gas manifold
comprises a first branch connected with a gas monitoring device,
wherein the gas monitoring device scans for a plurality of gases
that may be emitted by the closed valve of the fluid storage
container; and an indicator device operable to communicate a leak
has been detected based at in part on gas monitoring device data.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/470,868 filed Sep. 7, 2006, entitled "LEAK
CHARACTERIZATION APPARATUSES AND METHODS FOR FLUID STORAGE
CONTAINERS," the entire disclosure of which is hereby incorporated
by reference, for all purposes, as if fully set forth herein.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to leak detection. More
specifically the invention relates to leak detection for gas
cylinders and valves.
[0003] In the use of packaged gases, conventional practice in many
industrial applications has been to utilize high-pressure cylinders
for storage, transport and dispensing of a wide variety of gases.
In these applications, gas is contained in the cylinder in a
compressed state, to maximize the inventory of the gas available
for dispensing and ultimate use.
[0004] Since pressure of such compressed gases typically greatly
exceeds atmospheric pressure, structural integrity of the gas
package is critical to safety in the use of such packages, since
any leakage from a high-pressure container will quickly spread to
the surrounding environment of the container. Where the gas is
hazardous, e.g., toxic, pyrophoric, or otherwise detrimental to
health or safety of persons exposed to same, or deleterious to the
environment or operability of facilities in the vicinity of the
container, structural integrity of the gas-containment package is
vitally important to user acceptance and commercial success of the
package.
[0005] For these reasons, it has been common practice in the gas
industry to leak test gas packages, such as conventional
high-pressure cylinders, e.g., by methods in which the sealed
high-pressure vessel, or a portion thereof having joints or seams
susceptible to leakage, is submerged in or contacted with liquid to
determine the presence of leaking gas by bubble formation, or by
methods using detectors that are sensitive to the gas of interest,
such as leak-testing the sealed vessels with "gas sniffer" devices
coupled to chemical analyzers.
[0006] In view of the safety and reliability issues involving
packages of high-pressure gases in the semiconductor industry,
efforts have been made in recent years to significantly increase
the safety of gas packaging. This effort has produced sorbent-based
fluid storage and delivery systems, such as those described in U.S.
Pat. No. 5,518,528, in which gas is adsorbed and stored on a
physical adsorbent in a fluid storage and dispensing vessel and is
desorbed from the adsorbent and discharged from the vessel under
dispensing conditions. In these systems, the gas can be stored and
dispensed at sub-atmospheric pressure levels, typically below about
700 ton. Such physical adsorbent-based systems are commercially
available from ATMI, Inc. (Danbury, Conn., USA) and Matheson
Tri-Gas, Inc. (Parsippany, N.J., USA) under the trademarks SDS and
SAGE.
[0007] More recently, an enhanced safety fluid storage and
dispensing system has been developed, in which fluid is contained
in a vessel having a fluid pressure regulator in the interior
volume of the vessel. Such arrangement is effective to permit fluid
to be stored at high pressures, with the regulator being operative
to discharge fluid from the vessel only when it sees a downstream
pressure that is below the set point of the regulator. Such
internally disposed regulator systems are more fully described in
U.S. Pat. Nos. 6,101,816 and 6,089,027, and are commercially
available from ATMI, Inc. (Danbury, Conn., USA) under the trademark
VAC.
[0008] Despite these developments of safer gas packaging, it
remains critical for gas packages to be fabricated without the
occurrence of, or potential for, gas leakage at seams, joints and
fittings. Toward such objective, safe, effective and reproducible
leak-testing is vital to verify that pressurized gas vessels are
leak-free in character, and this is particularly true in the
semiconductor manufacturing industry, where reagent gases may be
extremely toxic and even lethal at low concentrations, in some
instances as low as parts-per-million or even
parts-per-billion.
[0009] In consequence, the art continues to seek improvements in
systems and techniques for determining the presence of leaks in
vessels employed for packaging of gases, and in verifying the
suitability of such vessels for extended leak-free service.
BRIEF DESCRIPTION OF THE INVENTION
[0010] The present invention relates to apparatus and process for
leak-testing of vessels employed for storage and dispensing of
fluids, or of other articles required to be leak-tight in use.
[0011] In one aspect, the invention relates to a system for
leak-testing an article required to be fluid leak-tight in use at a
fluid-contacting region thereof, to determine fluid leakage through
the article to a potential leak-expression region of the article,
such system including a leak-testing fluid held in confinement by
the fluid-contacting region of the article, a vacuum assembly
arranged for establishing a vacuum environment at the potential
leak-expression region of the article, and a leak detector arranged
to detect presence or absence of the leak-testing fluid in the
vacuum environment, to determine fluid leakage through the
article.
[0012] In another aspect, the invention relates to an apparatus for
leak-testing a vessel employed for dispensing of fluid, including
an evacuatable chamber adapted to contain a vessel holding a
leak-testing fluid, e.g., at superatmospheric pressure, a vacuum
system arranged to pump down the evacuatable chamber to establish
vacuum therein, and a leak detector joined in fluid communication
with the evacuatable chamber and operative to detect leakage from
the vessel holding leak-testing fluid into the chamber when pumped
down by the vacuum system.
[0013] In a further aspect, the invention relates to an apparatus
for leak-testing an article required to be fluid-tight in use,
including an evacuatable chamber adapted to contain the article in
an arrangement in which the article confines a leak-testing fluid,
e.g., at superatmospheric pressure, a vacuum system arranged to
pump down the evacuatable chamber to establish vacuum therein, and
a leak detector joined in fluid communication with the evacuatable
chamber and operative to detect leakage of leak-testing fluid from
or through the article under the vacuum established in the
evacuatable chamber when pumped down by the vacuum system.
[0014] A further aspect of the invention relates to a method of
leak-testing an article required to be fluid leak-tight in use at a
fluid-contacting region thereof, to determine fluid leakage through
the article to a potential leak-expression region of the article,
in which the method includes holding a leak-testing fluid in
confinement by the fluid-contacting region of the article,
establishing a vacuum environment at the potential leak-expression
region of the article, and detecting presence or absence of the
leak-testing fluid in the vacuum environment, to determine fluid
leakage through the article.
[0015] A still further aspect of the invention relates to a method
of leak-testing a vessel employed for dispensing of fluid,
comprising introducing into the vessel a leak-testing fluid, e.g.,
at superatmospheric pressure, sealing the leak-testing fluid in the
vessel, exposing the sealed vessel to vacuum and measuring leakage
of the leak-testing fluid from the vessel.
[0016] In yet another aspect, the invention relates to an apparatus
for leak-testing a vessel employed for dispensing of fluid,
including: a chamber adapted to (i) contain a vessel having vacuum
therein, and (ii) have a leak-testing fluid introduced therein, to
provide an environment of the leak-testing fluid, surrounding the
vessel in the chamber; a vacuum system arranged to establish the
vacuum in the vessel; and a leak detector arranged for fluid
communication with the vessel having vacuum therein, and operative
to detect leakage into the vessel of leak-testing fluid from the
leak-testing fluid environment surrounding the vessel in the
chamber.
[0017] In another aspect, the invention relates to an apparatus for
leak-testing an article required to be fluid-tight in use,
including: a chamber adapted to contain the article in an
arrangement in which the article confines a vacuum, and the chamber
has a leak-testing fluid introduced therein, so that leak-testing
fluid is present in an environment surrounding the article required
to be leak-tight in use; a vacuum system arranged to establish
vacuum confined by the article; and a leak detector joined in fluid
communication with the vacuum confined by the article and operative
to detect leakage of leak-testing fluid into the vacuum confined by
the article.
[0018] A still further aspect of the invention relates to a method
of leak-testing a vessel employed for dispensing of fluid,
comprising evacuating the vessel to establish vacuum therein,
sealing the vessel, externally exposing the sealed vessel to a
leak-testing fluid, and measuring leakage of the leak-testing fluid
into the vessel.
[0019] In one embodiment, an apparatus to characterize leaks in a
fluid storage container is provided. The apparatus may include a
valve coupler, a gas manifold, and an indicator device. Some
embodiments may also include a processor. The valve coupler may
couple the apparatus with a closed valve on the fluid storage
container. The gas manifold may be coupled with the valve coupler,
where the gas manifold includes a first branch connected with a gas
monitoring device. The gas monitoring device may scan for a
plurality of gases that may be emitted by the closed valve of the
fluid storage container. The indicator device may be operable to
communicate a leak has been detected based at in part on gas
monitoring device data. The processor may be operable to receive
gas monitoring device data representing masses for one or more of
the plurality of gases detected by the monitor.
[0020] In another embodiment, a system to characterize leaks in a
fluid storage container is provided. The system may include an
evacuatable chamber, a gas manifold and an indicator device. Some
embodiments may also include a processor. The evacuatable chamber
may store the fluid storage container. The gas manifold may be
coupled with the evacuatable chamber, where the gas manifold
includes a first branch connected with a gas monitoring device. The
gas monitoring device may scan for a plurality of gases that may be
emitted by the fluid storage container. The indicator device may be
operable to communicate a leak has been detected based at in part
on gas monitoring device data. The processor may be operable to
receive gas monitoring device data representing masses for one or
more of the plurality of gases detected by the monitor.
[0021] In another embodiment, a method to characterize a leak in a
fluid storage container is provided. The method may include a step
of connecting a valve on the fluid storage container with a leak
characterization apparatus. The leak characterization apparatus may
include a gas manifold, where the manifold is in fluid
communication with a valve coupler that connects with the valve on
the container and a gas monitoring device. The method may further
include a step of evacuating the gas manifold. The method may also
include scanning the evacuated manifold with the gas monitoring
device for a plurality of gases that may be emitted by the fluid
storage container. The method may moreover include a step of
generating leak characterization data about one or more of the
plurality of gases.
[0022] In another embodiment, a method to characterize a leak in a
fluid storage container is provided. The method may include a step
of placing the fluid storage container in an evacuatable chamber
fluidly coupled with a gas monitoring device. The method may also
include evacuating the chamber and scanning the chamber with the
gas monitoring device for a plurality of gases that may be emitted
by the fluid storage container. The method may further include a
step of generating leak characterization data about one or more of
the plurality of gases.
[0023] In one embodiment, an apparatus for determining a leak rate
of a gas from a closed valve is provided. The apparatus may include
a vacuum pump, a pressure measuring device, a monitoring device,
and a computer. The vacuum pump may be configured to couple with a
downstream side of the closed valve, wherein the downstream side of
the closed valve is characterized by a pressure, and decrease the
pressure of the downstream side of the closed valve. The pressure
measuring device may be configured to couple with the downstream
side of the closed valve, and determine the pressure of the
downstream side of the closed valve. The monitoring device may be
configured to couple with the downstream side of the closed valve,
and monitor a gas on the downstream side of the closed valve. The
gas may be characterized by a mass of the gas that is emitted from
the closed valve, and the monitoring device may be configured to
determine the mass of the emitted gas. The computer may be
configured to control the vacuum pump based at least in part on the
pressure, and determine the leak rate of the gas based at least in
part on the mass of the emitted gas.
[0024] In another embodiment, an apparatus for determining a leak
rate of a gas from a closed valve is provided. The apparatus may
include a means for decreasing a pressure of a downstream side of
the closed valve, a means for measuring the pressure of the
downstream side of the closed valve, a means for controlling the
means for decreasing the pressure of the downstream side of the
closed valve based at least in part on the pressure, a means for
determining a concentration of a gas on the downstream side of the
closed valve, and a means for determining the leak rate of the gas
based at least in part on the determined concentration of the
gas.
[0025] In another embodiment, a method of determining a leak rate
of a gas from a closed valve is provided. The method may include
decreasing the pressure of a downstream side of the closed valve,
determining the pressure of the downstream side of the closed
valve, monitoring a gas on the downstream side of the closed valve,
wherein the gas is characterized by a concentration and a molecular
mass, and determining the leak rate of the gas based at least in
part on the concentration or the molecular mass.
[0026] In another embodiment, a method to characterize a leak in a
fluid storage container is provided. The method may include placing
the fluid storage container in an evacuatable chamber fluidly
coupled with a gas monitoring device, evacuating the chamber,
introducing a first reactive fluid into the chamber, wherein the
first reactive fluid reacts with a fluid that may be emitted by the
fluid storage container to produce particles, scanning the chamber
with the gas monitoring device for a plurality of gases that may be
emitted by the fluid storage container, evacuating fluid from the
chamber and scanning the evacuated fluid with a particle counter,
and generating leak characterization data about one or more of the
plurality of gases based at least in part on data from the gas
monitoring device and data from the particle counter.
[0027] In another embodiment, a method to characterize a leak in a
fluid storage container is provided. The method may include placing
the fluid storage container in an evacuatable chamber fluidly
coupled with a gas monitoring device, evacuating the chamber,
introducing a reactive fluid into the chamber, wherein the reactive
fluid reacts with a fluid that may be emitted by the fluid storage
container to produce particles, evacuating fluid from the chamber
and scanning the evacuating fluid with a particle counter, and
generating leak characterization data about one or more of the
plurality of gases based at least in part on data from the particle
counter.
[0028] Other aspects, features and embodiments of the invention
will be more fully apparent from the ensuing disclosure and
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The present invention is described in conjunction with the
appended figures:
[0030] FIG. 1 is a schematic view of a leak detection system
according to one embodiment of the present invention;
[0031] FIG. 2 is a schematic view of a leak detection system
according to another embodiment of the present invention;
[0032] FIG. 3 is a schematic representation of a leak testing
system according to yet another embodiment of the invention, as
adapted for automated leak-testing of multiple vessels;
[0033] FIG. 4 is a schematic view of a leak detection system
according to a further embodiment of the present invention;
[0034] FIG. 5 is a schematic view of a leak testing system
according to yet another embodiment of the invention, as adapted
for automated leak-testing of multiple vessels;
[0035] FIG. 6 is a schematic view of an apparatus according to one
embodiment of the invention for determining a leak rate of a gas
from a closed valve;
[0036] FIG. 7 is a block diagram of a method according to one
embodiment of the invention for determining a leak rate of a gas
from a closed valve;
[0037] FIG. 8 is a block diagram of a method according to an
embodiment of the invention for characterizing a leak in a fluid
storage container;
[0038] FIG. 9 is a block diagram of a method according to another
embodiment of the invention for characterizing a leak in a fluid
storage container;
[0039] FIG. 10 is a block diagram of a method according to another
embodiment of the invention for characterizing a leak in a fluid
storage container using both a particle counter and possibly a gas
monitoring device.
[0040] FIG. 11 is a block diagram of an exemplary computer system
capable of being used in at least some portion of the apparatuses
or systems of the present invention, or implementing at least some
portion of the methods of the present invention.
[0041] In the appended figures, similar components and/or features
may have the same numerical reference label. Further, various
components of the same type may be distinguished by following the
reference label by a letter that distinguishes among the similar
components and/or features. If only the first numerical reference
label is used in the specification, the description is applicable
to any one of the similar components and/or features having the
same first numerical reference label irrespective of the letter
suffix.
DETAILED DESCRIPTION OF THE INVENTION
[0042] The ensuing description provides exemplary embodiments only,
and is not intended to limit the scope, applicability or
configuration of the disclosure. Rather, the ensuing description of
the exemplary embodiments will provide those skilled in the art
with an enabling description for implementing an exemplary
embodiment. It being understood that various changes may be made in
the function and arrangement of elements without departing from the
spirit and scope of the invention as set forth in the appended
claims.
[0043] Specific details are given in the following description to
provide a thorough understanding of the embodiments. However, it
will be understood by one of ordinary skill in the art that the
embodiments may be practiced without these specific details. For
example, circuits, systems, networks, processes, and other
components may be shown as components in block diagram form in
order not to obscure the embodiments in unnecessary detail. In
other instances, well-known circuits, processes, algorithms,
structures, and techniques may be shown without unnecessary detail
in order to avoid obscuring the embodiments.
[0044] Also, it is noted that individual embodiments may be
described as a process which is depicted as a flowchart, a flow
diagram, a data flow diagram, a structure diagram, or a block
diagram. Although a flowchart may describe the operations as a
sequential process, many of the operations can be performed in
parallel or concurrently. In addition, the order of the operations
may be re-arranged. A process is terminated when its operations are
completed, but could have additional steps not included in a
figure. A process may correspond to a method, a function, a
procedure, a subroutine, a subprogram, etc. When a process
corresponds to a function, its termination corresponds to a return
of the function to the calling function or the main function.
[0045] The term "machine-readable medium" includes, but is not
limited to portable or fixed storage devices, optical storage
devices, wireless channels and various other mediums capable of
storing, containing or carrying instruction(s) and/or data. A code
segment or machine-executable instructions may represent a
procedure, a function, a subprogram, a program, a routine, a
subroutine, a module, a software package, a class, or any
combination of instructions, data structures, or program
statements. A code segment may be coupled to another code segment
or a hardware circuit by passing and/or receiving information,
data, arguments, parameters, or memory contents. Information,
arguments, parameters, data, etc. may be passed, forwarded, or
transmitted via any suitable means including memory sharing,
message passing, token passing, network transmission, etc.
[0046] Furthermore, embodiments may be implemented by hardware,
software, firmware, middleware, microcode, hardware description
languages, or any combination thereof. When implemented in
software, firmware, middleware or microcode, the program code or
code segments to perform the necessary tasks may be stored in a
machine readable medium. A processor(s) may perform the necessary
tasks.
[0047] The present invention relates to apparatus and process for
leak-testing of vessels employed for storage and dispensing of
fluids, including vessels that are used for holding gases, as well
as vessels that are used for holding pressurized liquids, and
vessels that are used for holding pressurized solid source reagents
that are volatilized in the vessel to yield fluid for
dispensing.
[0048] The present invention is based on the discovery that the
sensitivity of leak-testing of vessels containing pressurized
leak-testing gas can be increased by many orders of magnitude,
e.g., four or even five orders of magnitude, by subjecting the
vessel being leak-tested to vacuum, and then detecting leakage from
the vessel in vacuo. This increase in sensitivity of the
leak-testing process was completely unexpected. Moreover the level
of gas leakage that is detectable by such method and associated
apparatus is reduced to such low levels that it becomes possible to
qualify vessels in a highly precise manner as being free from leaks
not only at the time of testing, as also as being free of the
probability of later developing leaks, i.e., during the subsequent
storage, transport and use of the vessel.
[0049] Although described specifically hereinafter in reference to
fluid dispensing vessels of a type used in industrial applications
such as semiconductor manufacturing, it will be appreciated that
the apparatus and process of the invention are broadly applicable
to leak testing of any vessels that are susceptible to leakage of
pressurized products, as well as to leak testing of any other
structural articles or elements that are required to be leak-tight
in use, as containing or confining pressurized material(s).
[0050] Further, also the invention is illustratively described
hereinafter as utilizing a helium detector as the leak detector for
leak-testing and qualification of fluid dispensing vessels, it will
be appreciated that a wide variety of other types of detectors can
be employed within the broad scope of practice of the invention,
such as mass spectrometer that is tuned to detect the specific
leak-testing gas of interest, or a flame ionizer analyzer, atomic
emission analyzer, a Fourier Transform-Infrared (FTIR) detector, or
other suitable detector appropriate for the leak-testing gas that
is involved.
[0051] Additionally, although the invention is illustratively
described hereinafter as involving leak-testing of vessels with a
leak-testing fluid, prior to fill of the vessels with chemical
reagent product for subsequent fluid dispensing, it will be
recognized that the invention may be practiced with leak-testing of
the vessel after it is filled with the product of interest. For
example, if the vessel is filled with arsine gas as the product to
be dispensed, the post-fill leak testing can be carried out with a
mass spectrometer that is tuned specifically for detection of
arsine. Alternatively, both pre-fill and post-fill leak testing of
the same vessel can be utilized to increase the level of assurance
that the vessel will not display leaking behavior in post-fill
use.
[0052] In application to a fluid storage and dispensing vessel, the
present invention may be carried out for leak-testing of the vessel
with imposition of vacuum either on the interior volume of the
vessel, so that in-leakage into such interior volume is monitored,
or alternatively, the vacuum may be imposed on the exterior of the
fluid storage and dispensing vessel so that any out-leakage of gas
into the vacuum environment of the vessel is detected.
[0053] The vacuum may be imposed at any suitable sub-atmospheric
pressure level appropriate to the test and the sensitivity of the
detection systems that are employed for determining the existence
of leakage. Typically, it is desired to impose vacuum that is below
100 torr, more preferably below 50 torr, even more preferably below
20 torr and most preferably below 10 torr, the specific level being
readily determinable within the skill of the art for a given
detection system and monitored leakage component.
[0054] When helium is employed as the leak testing gas, a
particularly preferred leak detector is the Alcatel AMS 142 Helium
Leak Detector, commercially available from Alcatel Vacuum
Technology, Paris, France. In low pressure environments, leak rates
down to 10.sup.-10 cc helium/sec are detectable by such leak
detector.
[0055] The vacuum imposed on the structure to be tested for
leak-tightness may be applied by means of a suitable vacuum pump,
cryopump, exposure to getters for chemisorbing gas in the
environment being evacuated, etc.
[0056] The leak detector used in a given application of the
invention may be calibrated using suitable calibrated sources. For
example, in one embodiment of the invention, wherein helium is the
leak-testing gas, calibrated sources providing leak rates of
10.sup.-7, 10.sup.-8 and 10.sup.-9 cc hydrogen/sec can be employed.
The resulting calibration then is employed to ensure accuracy of
the detector, which may for example being capable when properly
calibrated of detecting helium leaks in the 10.sup.-7 to 10.sup.-9
cc helium/sec range.
[0057] The method of the invention may be employed to establish a
pass/fail criterion for leak-tightness and acceptance or rejection
of products of various types. In one embodiment of the invention,
the leak-testing is conducted to determine the existence of leakage
at the neck joint of a gas containment vessel, e.g., at a neck
opening that is threaded to mate with a correspondingly threaded
valve head assembly, e.g., including a dispensing valve and a
manual actuator or automatic actuator for the valve.
[0058] In one embodiment, the present invention takes advantage of
the fact that the sensitivity of leak-testing of vessel can be
increased, by evacuating the vessel being leak-tested so that it
contains vacuum, surrounding the vessel, or a portion thereof
required to be leak-tight in use, with leak testing fluid and then
detecting leakage into the evacuated vessel. Such increase in
sensitivity of the leak-testing process is completely unexpected.
Moreover, the level of gas leakage that is detectable by such
method and associated apparatus is reduced to low levels and it
becomes possible to qualify vessels, as more generally discussed
hereinabove.
[0059] Referring now to the drawings, FIG. 1 is a schematic view of
a leak detection system 10 according to one embodiment of the
present invention. The system 10 as illustrated is being employed
to leak test the structural article 20. Article 20 includes wall
members 22 and 24 that abut one another at the bottom edge of wall
member 22 and the top edge of wall member 24, thereby defining a
seam 26 between the respective wall members. The wall members 22
and 24 in such manner form a wall assembly having a first surface
38 and a second surface 40. The seam 26 of the wall assembly is
secured by weld 28 on the first surface 38 of the wall and by a
weld 30 on the second surface 40.
[0060] In use, the wall assembly of article 20 is employed to
confine a pressurized fluid and is required to be of a leak-tight
character.
[0061] The leak detection system 10 used to test article 20
includes a pressurization enclosure 42 that is shown as being
sealingly engaged with the first surface 38 of the article 20. By
this arrangement, the enclosure 42 defines with the first surface
38 an enclosed volume 44. Joined in flow communication with the
enclosed volume 44 of the enclosure 42 is a leak-testing gas supply
50, which supplies leak-testing gas to the enclosed volume 44 by
means of line 52 interconnecting the leak-testing gas supply 50
with pump 54, with the pump in turn operating to deliver the
leak-testing gas to the enclosed volume 44 in line 56 containing
flow control valve 58 therein. The pressurization enclosure 42 is
provided with a vent line 92 having flow control valve 94
therein.
[0062] The leak detection system 10 further includes a vacuum
enclosure 46 that is shown as being sealingly engaged with the
second surface 40 of the article 20, to form with the second
surface an enclosed volume 48. Joined to the enclosed volume 48 of
the vacuum enclosure 46 is a vacuum pump 66 in line 68 containing
flow control valve 70 therein. Also joined to the enclosed volume
48 of the vacuum enclosure 46 by line 78 is a leak detector 76. The
leak detector 76 is arranged to detect the presence or absence of
the leak-testing gas in the enclosed volume 48 of the vacuum
enclosure 46 and to responsively transmit an output in signal
transmission line 80 to the output display monitor 82, for
graphical outputting of the detection result.
[0063] The leak detection system in the FIG. 1 embodiment includes
a CPU 60 that is coupled to leak-testing gas supply 50 by signal
transmission line 86, to pump 54 by signal transmission line 62, to
flow control valve 58 by signal transmission line 64, to flow
control valve 94 by signal transmission line 96, to vacuum pump 66
by signal transmission line 74, to flow control valve 70 by signal
transmission line 72, and to leak detector 76 by signal
transmission line 84.
[0064] The CPU 60 in the FIG. 1 embodiment can be of any suitable
type, e.g., a general purpose programmable computer, a
microprocessor, a programmable logic controller, or other
processor, which by means of the respective signal transmission
lines 86, 62, 64, 96, 72, 74 and 84 is coupled in signal
transmission relationship to pump 54, leak-testing gas supply 50,
flow control valve 58, flow control valve 94, vacuum pump 66, flow
control valve 70 and leak detector 76. The respective signal
transmission lines enable the CPU 60 to control the operation of
the components coupled thereto, in accordance with a cycle timer
program or in other manner, so that the leak-testing operation is
carried out in an efficient and reproducible manner.
[0065] In operation of the FIG. 1 system, the leak detector can be
calibrated in any suitable manner, such as for example by
connecting line 78 to a calibration standard, e.g., a source of
leak detector calibration gas in a container that releases the
calibration gas at a controlled accurate leak rate, so that the
leak detector can be accurately calibrated by reference thereto.
More than one calibration standard can be employed, to ensure that
the leak detector is appropriately calibrated for subsequent leak
detection operation. As another alternative, a calibration standard
may be installed in the interior volume 48 of vacuum enclosure 46,
and after the enclosure is pumped to establish vacuum in the
enclosure, the leak detector is actuated to detect the leak rate of
the calibration standard, so that the leak detector may be adjusted
for accurate further operation.
[0066] Once the leak detector 76 is calibrated, the CPU by signals
in lines 86, 62, 64 and 96 causes leak testing gas supply 50 to
open for dispensing, flow control valves 58 and 94 to open, and
pump 54 to pump leak testing gas from the supply 50 through line 52
into pressurization chamber 42 and into vent line 92 for purging of
the pressurization chamber. After the pressurization chamber 42 has
been purged of gas other than the leak testing gas, the CPU
transmits a signal in line 96 to close the flow control valve 94.
The flow of leak testing gas into chamber 42 continues until the
chamber is at a predetermined pressure of leak testing gas,
whereupon the CPU 60 transmits a signal in line 64 to shut the flow
control valve 58.
[0067] Contemporaneously (before, during and/or after the
pressurization of the chamber 42 with leak testing gas), the vacuum
pump 66 is actuated by a control signal from CPU 60 in line 74 and
flow control valve 70 is opened by control signal from CPU 60 in
line 72, so that the gas resident in the vacuum chamber 46 is
exhausted from the chamber in line 68 by the action of the vacuum
pump, so that a vacuum condition is established in the vacuum
chamber 46. The vacuum pump upon reaching of the desired vacuum
condition may be shut off by the CPU and the valve 70 closed to
maintain the vacuum condition in the vacuum chamber, or
alternatively the pump 66 may be operated in a back-up mode, to
maintain the vacuum pressure in the chamber 46 at a desired
level.
[0068] With the vacuum condition established in the vacuum chamber
46, the leak detector is actuated by a signal from CPU 60 in line
84, whereby sampling of the vacuum chamber environment is carried
out by flow (diffusion) of gas from the interior volume 48 of the
vacuum chamber 46 to the leak detector 76. The leak detector 76
responsively transmits an output signal in line 80 to the monitor
82 for graphical outputting of the leak testing operation results.
The leak detector can also contain or be associated with alarm or
recorder devices indicating when there is a leakage above the
predetermined threshold for acceptance or rejection of the article
20 as being suitably leak-tight in character, or alternatively as
lacking such leak-tightness. For this purpose, the leak detector
can output a signal to the CPU 60 in line 84 to terminate the
leak-testing, when a defective article 20 is determined to be
unsuitable for its intended fluid containment or fluid confinement
application.
[0069] When the leak testing determination has been made, the CPU
functions to deactuate the leak testing system so that the article
20 can be disengaged from the respective pressurization and vacuum
chambers, e.g., to prepare the system for leak testing of the next
succeeding article to be assessed for leak-tightness.
[0070] It will be appreciated that in lieu of separate leak
detector and vacuum pump components in the system as shown in FIG.
1, the system alternatively can be configured so that the vacuum
pump and leak detector are consolidated in an integrated, unitary
leak detector and vacuum pump assembly. Further, although it is
preferred to introduce the leak-testing fluid into the vessel at
superatmospheric pressure, it will be appreciated that the
leak-testing fluid may alternatively in some applications be
introduced at atmospheric, or even subatmospheric pressure
(although any subatmospheric pressure should be sufficiently above
the vacuum pressure level to increase efficient leak-testing).
[0071] FIG. 2 is a schematic view of a leak detection system
according to another embodiment of the present invention. The
illustrated leak-testing system 110 includes evacuatable chamber
112 including chamber housing 114 circumscribing an enclosed
interior volume 116 between flange elements at lower and upper ends
of the housing. The lower end of the housing is bounded by a flange
assembly including upper flange 124, lower flange 126 and
screw-type mechanical fasteners 128 and 130 interconnecting such
flanges. The upper flange 124 of such assembly may be brazed,
welded, soldered or otherwise secured to the chamber housing 114,
and advantageously is of a same size as the lower flange 126, so as
to facilitate mating and engagement of such flanges to form the
flange assembly.
[0072] In like manner, the chamber housing 114 at its upper end has
a flange 134 secured thereto, and matably engagable with flange
136, so that the respective flanges can be secured in position by
screw-type mechanical fasteners 138 and 140, as shown.
[0073] In the flange assembly including upper flange 134 and lower
flange 136, the upper flange has a port extension 142 secured
thereto. The port extension 142 terminates in a flange that is
matably engaged with a complimentary flange of the conduit 146. By
this arrangement, the respective flanges of the port extension and
conduit form a flange assembly 144. This flange assembly may be
mechanically interlocked in a conventional or otherwise known
manner, e.g., by a collar clamp, or by interconnecting bolt and nut
assemblies, or in other appropriate manner.
[0074] The conduit 146 at its opposite end from the flange assembly
144 is secured to a terminal section 148, such as by welding,
brazing, soldering, bonding, or use of mechanical fasteners. The
terminal section 148 of conduit 146 terminates in a flange that is
matably engageable with a complimentary flange of the port
extension 152, thereby forming a flange assembly 150. Such flange
assembly also can be mechanically interlocked in a conventional or
otherwise known manner, e.g., by a collar clamp, or by
interconnecting bolt and nut assemblies, or in other appropriate
manner.
[0075] The port extension 152 is coupled with leak detector 154.
The leak detector 154 may be of any suitable type, having leak
detection capability for the leak-testing gas that is present in
the vessels being leak-tested.
[0076] The leak detector 154 can be constructed and arranged so
that it has the capability for (i) pumping down to vacuum pressure
levels and (ii) upon achieving a predetermined vacuum pressure,
actuating the leak detection capability of the device. In this
mode, the leak detector may be actuated to pump down the chamber
housing 114 by evacuating gas from the interior volume 116 of the
housing and flowing it through the conduit 146 for discharge to the
ambient environment of the system. After the chamber housing and
conduit 146 have been evacuated to a predetermined pressure, the
detection capability of the leak detector is activated, to sense
and responsively produce an output correlative of the presence or
absence of the leak-testing gas in the vacuum environment of the
vessel being tested.
[0077] Alternatively, the chamber housing may be evacuated for leak
testing by a separate, dedicated vacuum pump, and after the
suitable vacuum level has been established in the environment of
the vessel, communication of the leak detector to the vacuum
environment is effected, so that the detector thereafter can sense
and provide a corresponding output of presence or absence of the
leak-testing gas in the vacuum environment.
[0078] To carry out the leak-testing method in the system of FIG. 1
using the dedicated vacuum pump 164, the system is arranged so that
the chamber housing 114 is coupled in flow relationship by vacuum
line 166 to vacuum pump 164. When the vacuum pump is actuated, the
gas contents of the interior volume 116 of the chamber housing 114
are withdrawn to establish a vacuum condition in such interior
volume, as well as the conduit 146 coupled therewith.
[0079] The leak detector 154 in such arrangement can be arranged to
automatically turn on at the point at which the pump-down of the
chamber housing 114 yields a selected pressure level, e.g., 10
torr, in the housing 114 and conduit 146. Alternatively, the leak
detector can be turned on in accordance with a cycle time program,
so that after a predetermined period of pumping to vacuum level,
the leak detector is actuated to provide an output correlative of
the presence or absence of the leak-testing gas.
[0080] In the arrangement shown in FIG. 2, the vacuum pump 164 is
joined, via signal transmission line 168, to central processing
unit (CPU) 160. The CPU 160 additionally is coupled to leak
detector 154 by signal transmission line 162. The CPU can be of any
suitable type, as for example a general purpose programmable
computer, microprocessor, programmable logic controller, etc.
[0081] A gas package 118 is shown as disposed in the interior
volume 116 of chamber housing 114. Such gas package comprises a
cylindrically-shaped tank having a neck region 120 to which is
joined a valve head assembly 122. The valve head assembly may
include a flow control valve that is manually actuated by a user of
the vessel, or alternatively, the valve head assembly can include a
valve actuator that is automatically actuatable by the CPU or other
control device to effect opening or closing of the valve
therein.
[0082] The vessel for purposes of the leak testing may contain any
suitable type of leak detector gas for which the system is
effective to sense presence or absence of a leak from the vessel.
Examples include, without limitation, rare gases, bulk gases,
krypton, neon, xenon, argon, hydrogen, oxygen, helium, nitrogen,
ammonia, arsine, phosphine, silane, acetylene, a halogen, a
hydrogen halide, a boron halide; a hydrogen chloride, hydrogen
bromide, chlorine, tungsten hexafluoride, hydrogen fluoride, carbon
dioxide, nitrous oxide, nitrogen dioxide, dicholorosilane,
trichlorosilane, carbonyl sulfide, sulfur hexafluoride, phosphine,
arsine, disilane, chlorine trifluoride, boron trichloride,
halogenated compounds, hydrocarbons, amines, or anorganometallic
precursors. Halogenated compounds may include, for example,
CF.sub.4, NF.sub.3, CHClF.sub.2, CClF.sub.2CF.sub.3, CClF.sub.3,
CHCl.sub.2F, CH.sub.2F.sub.2, and CH.sub.3F. Hydrocarbons may
include, for example, butadiene, ethane, ethylene, butane, butene,
isobutane, propane, propylene, methylacetylene-propadiene ("MAP"),
and methylacetylene-propadiene mixtures stabilized with alkane and
alkene hydrocarbons. Amines may include, for example,
triethylamine, dimethylamine and monoethylamine. Organometallic
precursors may include, for example, trimethylgallium,
trimethylaluminum, and trimethylindium. The leak detector gas used
for testing the leak-tightness of the vessel thus may be of any
appropriate type, and may be the same as, or alternatively
different from, the gas or other material that is contained in the
vessel in its normal intended use.
[0083] In one embodiment of the operation of the system
illustratively shown and described with reference to FIG. 2, the
vessel 118 is filled with a leak detection gas, e.g., helium, at
suitable superatmospheric pressure, as for example pressure in a
range of from about 300 to about 2000 pounds per square inch gauge
(psig).
[0084] The vessel 118 after filling with the leak testing gas is
placed in the housing chamber 114. The vacuum pump 164 then is
actuated to withdraw the gas from interior volume 16 of the chamber
housing 114 and conduit 146, until a predetermined pressure is
reached. The leak detector 154 thereupon is actuated to sense gas
leakage from the vessel, as flowing and/or diffusing through
conduit 146 to the leak detector 154.
[0085] Since the housing chamber 114 in the practice of the
invention as illustrated in FIG. 2 is evacuated to remove
atmospheric gases therefrom prior to leak testing, the loss of
sensitivity that has plagued prior art leak detection systems is
eliminated. As a result, the detection limit of the leak testing
operation has been found to be unexpectedly increased in magnitude,
e.g., by a magnitude of 5 times higher than the detection limit
that is achievable when leak testing is conducted in an ambient
environment at atmospheric pressure.
[0086] As a specific example, in an ambient environment at
atmospheric pressure, where helium is being used as the
pressurizing gas for a vessel of the type described in U.S. Pat.
No. 5,518,528, a leak detector can detect leakage only to levels on
the order of about 1.times.10.sup.-6 standard atmospheric-cc/sec
(standard atmospheric-cc/sec being volumetric flow rate of gas at
standard pressure and temperature (1 atmosphere, 25.degree. C.)
conditions; 1 atmospheric cc/sec=1.013 mBar-liter/sec). By
contrast, the system and method of the present invention, utilizing
a vacuum arrangement and leak detector with helium as the
leak-detection gas, can readily achieve leak detection levels as
low as 1.times.10.sup.-11 standard atmospheric-cc/sec. This
represents a five orders of magnitude improvement in the
sensitivity of the leak detection system by the apparatus and
method of the present invention. In addition, the apparatus and
method of the invention as a result of such high sensitivity enable
vessels to be identified that will be susceptible to problematic
leakage in subsequent use.
[0087] The apparatus and method of the present invention thereby
unexpectedly achieve a predictive utility, in the ability to
identify vessels that are likely to develop problematic leakage in
later use. Vessels that have been leak tested by currently
conventional leak test methods and found to be leak-free
nonetheless often develop leaks in the field, a fact that has
frustrated quality assurance efforts to identify and reject such
vessels at the manufacturing facility and/or gas fill site. This
circumstance is due to the fact that many leaks are not detected by
the conventional leak-testing, because they are below the detection
limit of the conventional technique, but such extremely small
leakages nonetheless often increase in magnitude after the shipment
from the factory of the pressurized vessel containing material for
subsequent dispensing, due to subsequent transportation, storage
and installation effects such as vibration, thermal cycling,
etc.
[0088] Generally, it has been determined that compressed gas
cylinders that manifest leakage in the factory or fill site, which
is less than 1.times.10.sup.-8 standard atmospheric-cc/sec., do not
normally manifest detectable leaks in the field. Accordingly, since
the detection limits of the apparatus and method of the invention
are substantially increased in relation to those of the prior art,
to below such leakage level of 1.times.10.sup.-8 standard
atmospheric-cc/sec, the apparatus and method of the invention can
easily detect such "future leakers," thereby dramatically
decreasing the incidence of field leaks in vessels that have
previously been qualified as suitable for pressurized gas
service.
[0089] In general, the method and apparatus of the present
invention are usefully employed to determine leakage levels that
are significantly below those of conventional leak detection
approaches. Current leak detection techniques in the art are able
to detect leakages only down to the level of 1.times.10.sup.-6
standard atmospheric-cc/sec. The present invention thus achieves a
significant advance in the art by its leak detection capability
below the conventional detection limit of 1.times.10.sup.-6
standard atmospheric-cc/sec. The present invention permits the
pass/fail leak rate criterion for acceptance or rejection of fluid
containment products to be at a value in a suitable range
appropriate to the specific products being qualified, e.g., a value
in a range of from 1.times.10.sup.-7 standard atmospheric-cc/sec to
1.times.10.sup.-11 standard atmospheric-cc/sec. In a specific
embodiment, the pass/fail value may be a value in a range of from
1.times.10.sup.-7 standard atmospheric-cc/sec to 1.times.10.sup.-9
standard atmospheric-cc/sec. For fluid dispensing vessels of the
types described in aforementioned U.S. Pat. Nos. 5,518,528,
6,101,816 and 6,089,027, the disclosures of which hereby are
incorporated herein by reference in their entireties, an
appropriate pass/fail value in one embodiment of the invention is
1.times.10.sup.-8 standard atmospheric-cc/sec, which is a detection
value that provides good assurance that leaks will not develop in
subsequent transport, storage and/or use, and at the same time is
not so restrictive that it results in rejection of vessels that
will be appropriately leak-free in such subsequent transport,
storage and/or use.
[0090] FIG. 3 is a schematic representation of a leak testing
system according to another embodiment of the invention, as adapted
for automated leak-testing of multiple vessels.
[0091] The leak detection system 200 shown in FIG. 3 provides the
capability to automatically leak test multiple vessels, and
includes a multi-vessel test assembly 210, including a support 212
of disk-like form, on which is mounted a series of cylindrical
vacuum chambers 216, 218, 220, 222, 224 and 226. The support 212 is
mounted on a motive structure 214, which may for example further
include tracks, an extendible mechanical arm or other associated
motive structure (not shown in FIG. 3), by which the multi-vessel
test assembly 210 can be translated in the direction indicated by
arrow A, into the vacuum housing 250.
[0092] The vacuum housing 250 includes an enclosure 238 having a
support 240 therein, on which the multi-vessel test assembly 210
reposes, subsequent to its translation into the vacuum housing
250.
[0093] Prior to being translated into the vacuum housing 250, the
multi-vessel test assembly 210 is loaded with the vessels to be
leak-tested. Such loading may be carried out in a manual,
automated, or semi-automated manner.
[0094] FIG. 3 illustratively shows a vessel 232 having a valve head
assembly 236 attached to the neck 234 of the vessel, as it is
inserted into cylindrical vacuum chamber 218 (in the direction
indicated by arrow B).
[0095] The multi-vessel test assembly 210 in one embodiment is
configured with a rotatable carousel that is rotated to permit an
operator or loading machine (not shown) to insert a vessel
pressurized with leak-testing fluid into each of the respective
cylindrical vacuum chambers. After such filling, the multi-vessel
test assembly 210 is translated into the enclosure 250 by the
motive structure 214, and the enclosure is sealed, as for example
by closure of a door, cover or other member of the enclosure. The
enclosure then is pumped down to vacuum level, by means of a vacuum
pumping capability of the leak detector 264 if such leak detector
has integral pumping capability, or alternatively (or additionally)
by means of the vacuum pump 260 joined to housing 250 by evacuation
line 262. In this embodiment, the vacuum pump 260 is controlled by
a central processor unit (CPU) 170 that transmits control signals
to vacuum pump 260 by means of signal transmission line 172.
[0096] When the vacuum pump 260 has operated to effect the
appropriate vacuum condition in the housing 250, each of the
vessels in turn is tested. For this purpose, each of the
cylindrical vacuum chambers 216, 218, 220, 222, 224 and 226 may
have detachable covers that are maintained in a sealed state in all
but one cylindrical chamber, which is opened for the leak-test of
the associated vessel in such vacuum chamber while all other vacuum
chambers are maintained in sealed condition, and with each of the
respective vessels in turn being exposed to vacuum within the
housing 250 and subjected to leak testing.
[0097] For this purpose, the housing 250 may contain a suction head
(not shown) or other structure that selectively engages each of the
vacuum chambers in turn and exposes the vessels therein
sequentially to the vacuum test condition.
[0098] During the exposure to vacuum of a given single vessel, the
leak detector 264 is actuated by the CPU 270, by a control signal
transmitted to the leak detector 264 in transmission line 168, to
actuate the leak detection process.
[0099] As shown in FIG. 2, the CPU may also be coupled in
controlling relationship to motive structure 214 by signal
transmission line 274.
[0100] By this integrated control arrangement the CPU can be
actuated to translate the assembly 210 into the evacuation
enclosure 250 after each of the vacuum chambers 216, 218, 220, 222,
224 and 226 is filled with a pressurized vessel. Once the assembly
of vessels to be leak tested is reposed in the enclosure 250, the
CPU actuates the closure and sealing of the housing 250, and then
actuates the vacuum pump 260 to pump down the enclosure 250 or a
sampling region therein coupled with a given cylindrical vacuum
chamber, to create vacuum conditions suitable for leak testing,
with the CPU concurrently actuating the leak detector 264 so that
the leak detector senses any gas leakage from the vessel being
tested.
[0101] In this manner, the system shown in FIG. 3 is automated to
impose vacuum conditions on the vessel being leak tested and to
detect any leakage event, in a highly efficient and reproducible
manner.
[0102] FIG. 4 is a schematic view of a leak detection system
according to one embodiment of the present invention. The
illustrated leak-testing system 310 includes chamber 312 including
chamber housing 314 circumscribing an enclosed interior volume 316
between flange elements at lower and upper ends of the housing. The
lower end of the housing is bounded by a flange assembly including
upper flange 324, lower flange 326 and screw-type mechanical
fasteners 328 and 330 interconnecting such flanges. The upper
flange 324 of such assembly may be brazed, welded, soldered or
otherwise secured to the chamber housing 314, and advantageously is
of a same size as the lower flange 326, so as to facilitate mating
and engagement of such flanges to form the flange assembly. A fluid
dispensing vessel 318 is contained in the interior volume 316 of
the chamber housing 314, having a neck 320 to which is joined a
valve head 322, joined in turn to the vacuum head 317 to form a
leak-tight fitting through which the interior volume of the vessel
318 can be evacuated by vacuum pumping.
[0103] Joined in flow communication to the chamber housing 314, by
flow line 366 containing flow control valve 369 therein, is a
source 364 of leak-testing fluid. The leak-testing fluid source 364
may be a vessel or container holding the leak-testing fluid at
appropriate pressure, so that it is flowable to the interior volume
316 of the chamber housing 314 to fill the interior volume with an
environment of leak-testing fluid surrounding the vessel to be
tested for leak-tightness.
[0104] The chamber housing 314 at its upper end has a flange 334
secured thereto, and matably engagable with flange 336, so that the
respective flanges can be secured in position by screw-type
mechanical fasteners 338 and 340, as shown.
[0105] In the flange assembly including upper flange 334 and lower
flange 336, the upper flange has a port extension 342 secured
thereto. The port extension 342 terminates in a flange that is
matably engaged with a complimentary flange of the conduit 346. By
this arrangement, the respective flanges of the port extension and
conduit form a flange assembly 344. This flange assembly may be
mechanically interlocked in a conventional or otherwise known
manner, e.g., by a collar clamp, or by interconnecting bolt and nut
assemblies, or in other appropriate manner.
[0106] The port extension 342 is coupled through flanges 334 and
336 with a vacuum head 317, by which the vessel 318 in chamber 312
can be evacuated, as hereinafter more fully described.
[0107] The conduit 346 at its opposite end from the flange assembly
344 is secured to a terminal section 348, such as by welding,
brazing, soldering, bonding, or use of mechanical fasteners. The
terminal section 348 of conduit 346 terminates in a flange that is
matably engageable with a complimentary flange of the port
extension 352, thereby forming a flange assembly 350. Such flange
assembly also can be mechanically interlocked in a conventional or
otherwise known manner, e.g., by a collar clamp, or by
interconnecting bolt and nut assemblies, or in other appropriate
manner.
[0108] The port extension 352 is coupled with leak detector 354.
The leak detector 354 may be of any suitable type, having leak
detection capability for the leak-testing gas that is present in
the vessels being leak-tested.
[0109] The leak detector 354 can be constructed and arranged so
that it has the capability for (i) pumping down to vacuum pressure
levels and (ii) upon achieving a predetermined vacuum pressure,
actuating the leak detection capability of the device. In this
mode, the leak detector may be actuated to pump down the vessel 318
by evacuating gas from the interior volume of the vessel and
flowing it through the vessel valve head 322, vacuum head 317
joined leak-tightly to the vacuum head, and conduit 346, for
discharge to the ambient environment of the system. After the
vessel and conduit 346 have been evacuated to a predetermined
pressure, and sufficient volume of leak-testing fluid has been
flowed into the chamber housing 314 from the source 364 in line 366
(with valve 369 being open), the detection capability of the leak
detector is activated, to sense and responsively produce an output
correlative of the presence or absence of the leak-testing gas in
the vacuum environment in the vessel being tested.
[0110] Alternatively, the vessel may be evacuated for leak testing
by a separate, dedicated vacuum pump, and after the suitable vacuum
level has been established in the interior of the vessel,
communication of the leak detector to the vacuum in the vessel
interior is effected, so that the detector thereafter can sense and
provide a corresponding output of presence or absence of the
leak-testing gas in the interior vacuum environment of the
vessel.
[0111] To carry out the leak-testing method in the system of FIG.
4, leak-testing fluid is flowed into the housing 314 from source
364 in line 366, as described above. When the vacuum pump is
actuated, the gas contents of the interior volume of the vessel 318
are withdrawn to establish a vacuum condition in such interior
volume, as well as the conduit 346 coupled therewith.
[0112] The leak detector 354 in such arrangement can be arranged to
automatically turn on at the point at which the pump-down of the
vessel interior volume yields a selected pressure level, e.g., 10
torr, within the vessel 318 and conduit 346. Alternatively, the
leak detector can be turned on in accordance with a cycle time
program, so that after a predetermined period of pumping to vacuum
level, the leak detector is actuated to provide an output
correlative of the presence or absence of the leak-testing gas
leakage into the vessel.
[0113] In the arrangement shown in FIG. 4, the leak-testing fluid
source 364 is joined, via signal transmission line 368, to central
processing unit (CPU) 360. The CPU 360 additionally is coupled to
leak detector 354 by signal transmission line 362. The CPU can be
of any suitable type, as for example a general purpose programmable
computer, microprocessor, programmable logic controller, etc. for
carrying out the leak-testing operation in accordance with a cycle
time program, or in other automated manner. For example, the flow
control valve 369 may be responsive to the control signal sent to
source 364, so that the fluid is dispensed to the chamber housing
interior volume 316 in a controlled or sequential manner, with
respect to other steps of the leak-testing procedure.
[0114] The vessel for purposes of the leak testing may be
exteriorly exposed to any suitable type of leak detector gas for
which the system is effective to sense presence or absence of a
leak into the vessel. Examples include, without limitation,
hydrogen, oxygen, helium, nitrogen, ammonia, arsine, phosphine,
silane, boron trifluoride, boron trichloride, acetylene, and
chlorine. The leak detector gas used for testing the leak-tightness
of the vessel thus may be of any appropriate type, and may be the
same as, or alternatively different from, the gas or other material
that is contained in the vessel in its normal intended use.
[0115] In one embodiment of the operation of the system
illustratively shown and described with reference to FIG. 4, the
vessel 318 is exposed to a leak detection gas, e.g., helium, at
suitable superatmospheric pressure, as for example pressure in a
range of from about 300 to about 2000 pounds per square inch gauge
(psig).
[0116] The vessel 318 initially is placed in the housing chamber
314 and coupled to the vacuum head 317 at the valve head 322 of the
vessel. The chamber housing then is filled to a desired extent with
the leak-testing fluid from source 364, and valve 366 then is
closed. The vacuum pump in the leak detector 354 then is actuated
to withdraw the gas from the interior volume of the vessel, until a
predetermined vacuum level is reached. The leak detector 354
thereupon is actuated to sense gas leakage into the vessel, as
flowing and/or diffusing through conduit 346 to the leak detector
354.
[0117] Since the vessel is evacuated to remove atmospheric gases
therefrom prior to leak testing, the loss of sensitivity that has
plagued prior art leak detection systems is eliminated. As a
result, the detection limit of the leak testing operation is
increased in magnitude, relative to the detection limit that is
achievable when leak testing is conducted in an ambient environment
at atmospheric pressure.
[0118] The apparatus and method of the invention as a result of
such high sensitivity enable vessels to be identified that will be
susceptible to problematic leakage in subsequent use.
[0119] The apparatus and method of the present invention thereby
unexpectedly achieve a predictive utility, in the ability to
identify vessels that are likely to develop problematic leakage in
later use. Vessels that have been leak tested by currently
conventional leak test methods and found to be leak-free
nonetheless often develop leaks in the field, a fact that has
frustrated quality assurance efforts to identify and reject such
vessels at the manufacturing facility and/or gas fill site. This
circumstance is due to the fact that many leaks are not detected by
the conventional leak-testing, because they are below the detection
limit of the conventional technique, but such extremely small
leakages nonetheless often increase in magnitude after the shipment
from the factory of the pressurized vessel containing material for
subsequent dispensing, due to subsequent transportation, storage
and installation effects such as vibration, thermal cycling,
etc.
[0120] Generally, it has been determined that compressed gas
cylinders that manifest leakage in the factory or fill site, which
is less than 1.times.10.sup.-8 standard atmospheric-cc/sec., do not
normally manifest detectable leaks in the field. Accordingly, since
the detection limits of the apparatus and method of the invention
are substantially increased in relation to those of the prior art,
to below such leakage level of 1.times.10.sup.-8 standard
atmospheric-cc/sec, the apparatus and method of the invention can
easily detect such "future leakers," thereby dramatically
decreasing the incidence of field leaks in vessels that have
previously been qualified as suitable for pressurized gas
service.
[0121] In general, the method and apparatus of the present
invention are usefully employed to determine leakage levels that
are significantly below those of conventional leak detection
approaches. Current leak detection techniques in the art are able
to detect leakages only down to the level of 1.times.10.sup.-6
standard atmospheric-cc/sec. The present invention thus achieves a
significant advance in the art by its leak detection capability
below the conventional detection limit of 1.times.10.sup.-6
standard atmospheric-cc/sec. The present invention permits the
pass/fail leak rate criterion for acceptance or rejection of fluid
containment products to be at a value in a suitable range
appropriate to the specific products being qualified, e.g., a value
in a range of from 1.times.10.sup.-7 standard atmospheric-cc/sec to
1.times.10.sup.-11 standard atmospheric-cc/sec. In a specific
embodiment, the pass/fail value may be a value in a range of from
1.times.10.sup.-7 standard atmospheric-cc/sec to 1.times.10.sup.-9
standard atmospheric-cc/sec. For fluid dispensing vessels of the
types described in aforementioned U.S. Pat. Nos. 5,518,528,
6,101,816 and 6,089,027, the disclosures of which hereby are
incorporated herein by reference in their entireties, an
appropriate pass/fail value in one embodiment of the invention is
1.times.10.sup.-8 standard atmospheric-cc/sec, which is a detection
value that provides good assurance that leaks will not develop in
subsequent transport, storage and/or use, and at the same time is
not so restrictive that it results in rejection of vessels that
will be appropriately leak-free in such subsequent transport,
storage and/or use.
[0122] In operation of the FIG. 4 system, the leak detector can be
calibrated in any suitable manner, such as for example by a
calibration standard, e.g., a source of leak detector calibration
gas in a container that releases the calibration gas at a
controlled accurate leak rate, so that the leak detector can be
accurately calibrated by reference thereto. More than one
calibration standard can be employed, to ensure that the leak
detector is appropriately calibrated for subsequent leak detection
operation.
[0123] It will be appreciated that in lieu of an arrangement in
which the vacuum pump and leak detector are consolidated in an
integrated, unitary leak detector and vacuum pump assembly as shown
in FIG. 4, separate leak detector and vacuum pump components can
alternatively be employed in the system.
[0124] FIG. 5 is a schematic representation of a leak testing
system according to another embodiment of the invention, as adapted
for automated leak-testing of multiple vessels.
[0125] The leak detection system 400 shown in FIG. 5 provides the
capability to automatically leak test multiple vessels, and
includes a multi-vessel test assembly 410, including a support 412
of disk-like form, on which is mounted a series of cylindrical
chambers 416, 418, 420, 422, 424 and 426. The support 412 is
mounted on a motive structure 414, which may for example further
include tracks, an extendible mechanical arm or other associated
motive structure (not shown in FIG. 5), by which the multi-vessel
test assembly 410 can be translated in the direction indicated by
arrow A, into the housing 450.
[0126] The housing 450 includes an enclosure 438 having a support
440 therein, on which the multi-vessel test assembly 410 reposes,
subsequent to its translation into the housing 450. The housing
also includes a vacuum head 490, which is joined to vacuum and leak
detection line 492, whereby the multiple vessels can be evacuated
to suitable vacuum levels by action of the pump 460, joined by pump
line 462 to the vacuum and leak detection line 492. The vacuum and
leak detection line 492 is also joined to the leak detection line
466 associated with leak detector 464.
[0127] Prior to being translated into the vacuum housing 450, the
multi-vessel test assembly 410 is loaded with the vessels to be
leak-tested. Such loading may be carried out in a manual,
automated, or semi-automated manner.
[0128] FIG. 5 illustratively shows a vessel 432 having a valve head
assembly 436 attached to the neck 434 of the vessel, as it is
inserted into cylindrical chamber 418 (in the direction indicated
by arrow B).
[0129] The multi-vessel test assembly 410 in one embodiment is
configured with a rotatable carousel that is rotated to permit an
operator or loading machine (not shown) to insert a vessel into
each of the respective cylindrical chambers. After such filling,
the multi-vessel test assembly 410 is translated into the enclosure
450 by the motive structure 414, and the enclosure is sealed, as
for example by closure of a door, cover or other member of the
enclosure. The enclosure then is filled with leak-testing gas from
source 494 thereof, as joined to the enclosure 450 by feed line 496
containing flow control valve 498 therein, and the vessels are
connected to the vacuum head 490 and the vacuum pump is actuated to
pump the vessels down to vacuum level, by means of the vacuum pump
460 joined to vacuum and leak detection line 492 in housing 450 via
the evacuation line 462. In this embodiment, the vacuum pump 460 is
controlled by a central processor unit (CPU) 470 that transmits
control signals to vacuum pump 460 by means of signal transmission
line 472.
[0130] When the vacuum pump 460 has operated to effect the
appropriate vacuum condition in the vessels in housing 450, each of
the vessels in turn is tested in the respective cylindrical chamber
416, 418, 420, 422, 424 and 426.
[0131] During the exposure to vacuum of a given single vessel, the
leak detector 464 is actuated by the CPU 470, by a control signal
transmitted to the leak detector 464 in transmission line 468, to
actuate the leak detection process.
[0132] As shown in FIG. 5, the CPU may also be coupled in
controlling relationship to motive structure 414 by signal
transmission line 474.
[0133] By this integrated control arrangement the CPU can be
actuated to translate the assembly 410 into the evacuation
enclosure 450 after each of the chambers 416, 418, 420, 422, 424
and 426 is filled with a pressurized vessel. Once the assembly of
vessels to be leak tested is reposed in the enclosure 450, the CPU
actuates the closure and sealing of the housing 450, and the
enclosure is filled with leak-testing fluid from source 494, and
then the CPU 470 actuates the vacuum pump 460 to pump down the
vessels in the enclosure 450, to create vacuum conditions suitable
for leak testing, following which the CPU actuates the leak
detector 464 so that the leak detector senses any gas leakage into
the vessel being tested.
[0134] In this manner, the system shown in FIG. 5 is automated to
impose vacuum conditions on the vessel being leak tested and to
detect any leakage event, in a highly efficient and reproducible
manner.
[0135] It will be appreciated that the apparatus and method of the
invention may be utilized in respect of any structures, structural
members, packaging, vessels, fluid containment devices, etc. that
must maintain leak-tightness in use.
[0136] The advantages and features of the invention are further
illustrated with reference to the following example, which is not
to be construed as in any way limiting the scope of the invention
but rather as illustrative of one embodiment of the invention in a
specific application thereof.
EXAMPLE 1
[0137] Inboard helium leak checking of SDS3 or 2.2L VAC cylinders
(ATMI, Inc., Danbury, Conn., USA) is carried out by the following
procedure.
[0138] A system of the type shown schematically in FIG. 2 is
employed. The leak detector is an Alcatel ASM 142 helium leak
detector which displays leak rate and system vacuum. The leak
detector is actuated by switching the main power toggle switch to
the "ON" position. The leak detector will then automatically begin
start-up checks and then perform a self-calibration.
[0139] When the leak detector successfully completes start-up and
calibration procedures, an audible message will announce the system
is ready for testing and the leak detector display will indicate,
"Ready for Testing". At this point the cycle button is depressed to
initiate a test.
[0140] The inboard test port of the helium leak detector is
connected by a stainless steel bellows line to the inlet of the
leak test chamber. The leak detector is calibrated with a certified
helium leak rate using a calibrated leak standard that is sealed in
the test chamber after the leak test valve is opened.
[0141] After sealing the test chamber with the test chamber flange,
the "cycle" button on the Alcatel ASM 142 is depressed to initiate
the chamber calibration test. After successful pump down of the
system, the helium reading is observed on the leak detector
display. After a stable reading is achieved, the chamber
calibration leak test reading is determined to be within 5% of the
stated certified calibration. After calibration of the chamber, the
cycle button on the leak detector is pressed to vent the leak
chamber to atmospheric pressure. The flange bolts on the chamber
then are loosened and the chamber flange is removed. Next, the
helium certified leak standard is removed from the chamber, and the
leak valve is closed.
[0142] The cylinder leak testing then is conducted according to the
following test procedure:
[0143] Step 1: Pressurize the cylinder to be tested with 300 PSIG
of 100% ultra-high purity helium. Place the helium filled cylinder
to be tested into the leak test chamber and seal the inlet opening
flange.
[0144] Step 2: Initiate the leak test cycle by depressing the
"cycle" button on the leak detector. The leak detector will proceed
to pump down the leak test chamber until a sufficient vacuum is
reached for leak testing.
[0145] Step 3: After the leak detector commences helium leak
detection, wait five minutes for the helium signal to
stabilize.
[0146] Step 4: Observe the magnitude of the leak by viewing leak
detector display. A helium signal greater than
1.013.times.10.sup.-8 mbar-1/sec is considered a leak. Record the
leak test result next to the serial number tested on the cylinder
lot traveler. If the cylinder fails the leak test it may be
retested. In the case of a retest, the chamber is vented by
pressing the cycle button on the leak detector and then a second
test is performed as before. If the cylinder fails to meet the leak
test requirements on the second test, the cylinder is rejected and
is removed from the lot of acceptable cylinders.
[0147] Step 5: Upon completion of the leak check the leak test
chamber is vented by depressing the "cycle" button on the leak
detector. The cylinder may be safely removed and another cylinder
tested.
EXAMPLE 2
[0148] A valved empty cylinder is connected to an Alcatel ASM-142
helium leak detector. The unit has a helium sensitivity that can be
related to a minimum leak rate detection limit of 1.times.10.sup.-9
cc He/sec when gas is introduced into the unit. The unit obtains
the sample by subjecting the feed line to a vacuum and drawing in
the sample. The feed line is connected to the cylinder, so that the
entire cylinder is subjected to the vacuum capability of
1.times.10.sup.-6 ton. While subject to a vacuum, helium gas is
introduced in a controlled manner to various potential leak points
or threaded connections on the external valve (helium gas is
free-flowed over the test area). The vacuum in the cylinder draws
in the helium through any leak sites, and the unit detects and
measures the helium strength of entry. The strength of entry can be
equated to a leak rate. By controlling the helium gas exposure to
the valve, a specific leak rate can be assigned to each valve
component area measured.
[0149] In another embodiment of the invention, an apparatus to
characterize leaks in a fluid storage container is provided. The
apparatus may include a valve coupler and a gas manifold. Some
embodiments may also include a processor. The valve coupler may
couple the apparatus with a closed valve on the fluid storage
container. The gas manifold may be coupled with the valve coupler,
where the gas manifold includes a first branch connected with a gas
monitoring device. The gas monitoring device may scan for a
plurality of gases that may be emitted by the closed valve of the
fluid storage container. The processor may be operable to receive
gas monitoring device data representing masses for one or more of
the plurality of gases detected by the monitor.
[0150] In some embodiments, the valve coupler may include an outlet
connector for a compressed gas valve and/or the fluid storage
container may include a high pressure gas cylinder. In these or
other embodiments, the gas manifold may also include a second
branch connected with a manifold pump to evacuate the manifold. The
gas manifold may also have a third branch connected with a pressure
measuring device to measure the gas pressure in the manifold. In
some embodiments the gas monitoring device may include a mass
spectrometer that scans a mass range from about 1 atomic mass unit
to about 400 atomic mass units.
[0151] In some embodiments the processor may perform other
functions. For example, the processor may be operable to generate a
mass spectrum from the data representing masses for one or more of
the plurality of gases detected by the monitor. In some of these
embodiments, the processor may be in communication with a display
that may be able to display the mass spectrum. In some embodiments,
the processor may be operable to calculate leak rates for one or
more of the plurality of gases. In some of these embodiments, the
processor may be in communication with a display that can display
the leak rates for one or more gases. The leak rates may possibly
be displayed in units of cubic centimeters per second.
[0152] In another embodiment of the invention, a system to
characterize leaks in a fluid storage container is provided. The
system may include an evacuatable chamber and a gas manifold. Some
embodiments may also include a processor. The evacuatable chamber
may store the fluid storage container. The gas manifold may be
coupled with the evacuatable chamber, where the gas manifold
includes a first branch connected with a gas monitoring device. The
gas monitoring device may scan for a plurality of gases that may be
emitted by the fluid storage container. The processor may be
operable to receive gas monitoring device data representing masses
for one or more of the plurality of gases detected by the
monitor.
[0153] In some embodiments, the evacuatable chamber may be coupled
with a chamber vacuum pump to evacuate gases from the chamber. In
these and other embodiments, the evacuatable chamber may be coupled
with a chamber pressure monitor to measure and display gas pressure
in the chamber. In some embodiments, the gas manifold may also
include a second branch connected with a manifold pump to evacuate
the manifold. The gas manifold may also have a third branch
connected with a pressure measuring device to measure the gas
pressure in the manifold. In some of these embodiments, the gas
monitoring device may include a mass spectrometer that scans a mass
range from about 1 atomic mass unit to about 400 atomic mass
units.
[0154] In another embodiment of the invention, a method to
characterize a leak in a fluid storage container is provided. The
method may include a step of connecting a valve on the fluid
storage container with a leak characterization apparatus. The leak
characterization apparatus may include a gas manifold, where the
manifold is in fluid communication with a valve coupler that
connects with the valve on the container and a gas monitoring
device. The method may further include a step of evacuating the gas
manifold. The method may also include scanning the evacuated
manifold with the gas monitoring device for a plurality of gases
that may be emitted by the fluid storage container. The method may
moreover include a step of generating leak characterization data
about one or more of the plurality of gases. The monitoring device
may scan a mass range from about 1 atomic mass unit to about 400
atomic mass units. The characterization data may include a mass
spectrum of the plurality of gases emitted by the fluid storage
container.
[0155] In some embodiments, the method may also include sending
leak characterization data to a processor operable to calculate
leak flow rates for the one or more gases on a display in
electronic communication with the processor. In these or other
embodiments, the method may further include displaying the leak
flow rates for the one or more gases on a display in electronic
communication with the processor. In some embodiments, the method
may moreover include pressurizing the fluid storage container with
a leak testing fluid before connecting the container with the leak
characterization apparatus. The leak testing fluid may be
compressed air, hydrogen, oxygen, helium, nitrogen, ammonia,
arsine, phosphine, silane, acetylene, a halogen, a hydrogen halide,
or a boron halide.
[0156] In another embodiment of the invention, a method to
characterize a leak in a fluid storage container is provided. The
method may include a step of placing the fluid storage container in
an evacuatable chamber fluidly coupled with a gas monitoring
device. The gas monitoring device may scan a mass range from about
1 atomic mass unit to about 400 atomic mass units. The method may
also include evacuating the chamber and scanning the chamber with
the gas monitoring device for a plurality of gases that may be
emitted by the fluid storage container. The method may further
include a step of generating leak characterization data about one
or more of the plurality of gases. The characterization data may
include a mass spectrum of the plurality of gases emitted by the
fluid storage container.
[0157] In some embodiments, the method may further include sending
the leak characterization data to a processor operable to calculate
leak flow rates for one or more of the plurality of gases. In these
embodiments, the method may also include displaying the leak flow
rates for the one or more gases on a display in electronic
communication with the processor. In certain embodiments, the
method may also include pressurizing the fluid storage container
with a leak testing fluid before placing the container in the
evacuatable chamber.
[0158] In another embodiment of the invention, an apparatus for
determining a leak rate of a gas from a closed valve is provided.
The apparatus may include a vacuum pump, a pressure measuring
device, a monitoring device, and a computer.
[0159] The vacuum pump may be configured to couple with a
downstream side of the closed valve, wherein the downstream side of
the closed valve is characterized by a pressure, and decrease the
pressure of the downstream side of the closed valve. In some
embodiments, the closed valve may have an upstream side
characterized by the presence of the gas in a high pressure
state.
[0160] The pressure measuring device may be configured to couple
with the downstream side of the closed valve, and determine the
pressure of the downstream side of the closed valve. The pressure
measuring device may, in some embodiments, be a manometer
configured to communicate with the computer.
[0161] The monitoring device may be configured to couple with the
downstream side of the closed valve, and monitor a gas on the
downstream side of the closed valve. The monitoring device may, in
some embodiments, be a mass spectrometer configured to communicate
with the computer. The gas may be characterized by a mass of the
gas that is emitted from the closed valve, and the monitoring
device may be configured to determine the mass of the emitted gas.
The emitted gas may include atoms or molecules that can be detected
by the monitoring device.
[0162] In some embodiments, the monitoring device may further be
configured to couple with a calibration gas leak source having a
certain leak rate. The monitoring device may monitor a calibration
gas from the calibration gas leak source, where the calibration gas
is characterized by a mass of gas. The monitoring device may then
determine the mass of the calibration gas. In these or other
embodiments, the computer may further be configured to store a
value representative of the certain leak rate, where the value is
based at least in part on the mass of the calibration gas.
[0163] The computer may be configured to control the vacuum pump
based at least in part on the pressure, and determine the leak rate
of the gas based at least in part on the concentration of the
emitted gas. Determining the leak rate of the gas may include
comparing the concentration of the emitted gas to at least one
stored value representative of at least one certain leak rate. In
some embodiments, determining the leak rate may be further based at
least in part on the pressure of the downstream side of the closed
valve. The computer may also be configured to report to a user the
determined leak rate of the gas in units of cubic centimeters per
second.
[0164] In some embodiments, the apparatus may also include an
evacuation pump. In various embodiments, the evacuation pump may be
configured to decrease the pressure of the downstream side of the
closed valve to about 1 Torr, and the vacuum pump may be configured
to decrease the pressure of the downstream side of the closed valve
to less than about 1 Torr.
[0165] In some embodiments, the computer may further be configured
to control the evacuation pump based at least in part on the
determination of the pressure of the downstream side of the closed
valve. Controlling the evacuation pump and the vacuum pump based at
least in part on the determination of the pressure of the
downstream side of the closed valve may include activating the
evacuation pump until the pressure of the downstream side of the
valve is decreased to about 1 Torr, then deactivating the
evacuation pump and activating the vacuum pump.
[0166] In another embodiment of the invention, another apparatus
for determining a leak rate of a gas from a closed valve is
provided. The apparatus may include a means for decreasing a
pressure of a downstream side of the closed valve; a means for
measuring the pressure of the downstream side of the closed valve;
a means for controlling the means for decreasing the pressure of
the downstream side of the closed valve based at least in part on
the pressure; a means for determining the concentration of a gas on
the downstream side of the closed valve; and a means for
determining the leak rate of the gas based at least in part on the
determined concentration.
[0167] In some embodiments, the apparatus may also include a means
for storing at least one value representative of at least one
certain leak rate. In these and other embodiments, the means for
determining the leak rate may include means for comparing the
determined concentration to the at least one stored value
representative of the at least one certain leak rate. In some
embodiments, the means for determining the leak rate of the gas may
further be based at least in part on the pressure of the downstream
side of the closed valve. Some embodiments may also include a means
for reporting to a user the determined leak rate of the gas in
units of cubic centimeters per second.
[0168] In another embodiment of the invention a method of
determining a leak rate of a gas from a closed valve is provided.
The method may include decreasing the pressure of a downstream side
of the closed valve; determining the pressure of the downstream
side of the closed valve; monitoring a gas on the downstream side
of the closed valve, wherein the gas is characterized by a
concentration and a molecular mass; and determining the leak rate
of the gas based at least in part on the concentration or the
molecular mass of the gas.
[0169] In some embodiments the method may also include storing at
least one value representative of at least one certain leak rate,
and determining the leak rate of the gas may include comparing the
mass of the particles to the at least one stored value
representative of the at least one certain leak rate. Determining
the leak rate of the gas in these or other embodiments may also be
based at least in part on the pressure of the downstream side of
the closed valve. Some of the methods of the inventions may further
include reporting to a user the determined leak rate of the gas in
units of cubic centimeters per second.
[0170] In another embodiment, a method to characterize a leak in a
fluid storage container is provided. The method may include placing
the fluid storage container in an evacuatable chamber fluidly
coupled with a gas monitoring device, evacuating the chamber,
introducing a first reactive fluid into the chamber, wherein the
first reactive fluid reacts with a fluid that may be emitted by the
fluid storage container to produce particles, scanning the chamber
with the gas monitoring device for a plurality of gases that may be
emitted by the fluid storage container, evacuating fluid from the
chamber and scanning the evacuated fluid with a particle counter,
and generating leak characterization data about one or more of the
plurality of gases based at least in part on data from the gas
monitoring device and data from the particle counter.
[0171] In some embodiments, the first reactive fluid may include
oxygen, and the particles may be oxides created by the reaction of
the oxygen with the fluid leaking from the fluid storage container.
Other reactive fluids, known in the art, may also be used as the
first reactive fluid to make particles with the leaking fluid. In
some embodiments, the first reactive fluid may be selected
specifically for it's reactivity to the subject fluid held within
the container to be tested. In some embodiments, the method may
further include introducing a second reactive fluid to the
particles, wherein the second reactive fluid may bond with the
particles to make at least a portion of the particles larger. The
second reactive fluid may be any fluid known in the art for
enlarging the size of a particle, and in some instances may be
selected for it's compatibility with the particles that will be
produced by the leaking fluid and the first reactive fluid. Larger
particles may allow less sensitive particle counters to be employed
to produce the same overall system accuracy, or increase the
overall system accuracy given a certain particle counter.
[0172] In another embodiment, another method to characterize a leak
in a fluid storage container is provided. The method may include
placing the fluid storage container in an evacuatable chamber
fluidly coupled with a gas monitoring device, evacuating the
chamber, introducing a first reactive fluid into the chamber,
wherein the first reactive fluid reacts with a fluid that may be
emitted by the fluid storage container to produce particles,
evacuating fluid from the chamber and scanning the evacuating fluid
with a particle counter, and generating leak characterization data
about one or more of the plurality of gases based at least in part
on data from the particle counter. In some embodiments, a second
reactive fluid may also be introduced as discussed above.
[0173] FIG. 6 shows an apparatus 600 for characterizing leaks in a
fluid storage container, possibly including determining a leak rate
of a gas from a closed valve 605. Though valve 605 is shown coupled
with a gas cylinder 610, valve 605 may be coupled to other storage
devices, flow devices, and/or other systems in other embodiments.
Valve 605 may be coupled with a tubing system 615. Tubing system
615 may be any system known in the art for connecting together
fluid utilizing, management, and/or monitoring equipment, including
a valve coupler, gas manifold, or evacuatable chamber. Tubing
system 615 may be coupled to various other components including an
evacuation pump 620, a vacuum pump 625, a monitoring device 630, a
calibration gas leak source 640, and a pressure measuring device
645 (also referred to herein as a chamber pressure monitor). In
some embodiments, pressure measuring device 645 may be a manometer.
In these or other embodiments, monitoring device 630 may include a
mass spectrometer. The upstream side of valve 605, in this example,
is the inside of gas cylinder 610. The downstream side of valve
605, in this example, is the inside of tubing system 615.
[0174] Remotely controlled valves 611, 621, 631, 641 may
selectively isolate various components coupled with the tubing
system. The valves may, for example, be pneumatic or electronically
controlled solenoid valves. In other embodiments, remotely
controlled valves 611, 621, 631, 641 may be manually controlled.
Also shown in FIG. 6 is a vacuum sentry valve 655. Vacuum sentry
valve 655 may prevent oil and/or other material from evacuation
pump 620 from contaminating other system components should
evacuation pump 620 fail during operations causing pressure to
rapidly increase in tubing system 615.
[0175] Apparatus 600 may also include a computer 650. The computer
may be any processor known in the art and may be in communication
with various components of apparatus 600, including evacuation pump
620, monitoring device 630, pressure measuring device 645 and
remotely controlled valves 611, 621, 631, 641. Though in FIG. 6,
computer 650 is shown as a laptop computer, in some embodiments,
computer 650 may be another type of device such as a notebook
computer, desktop computer, or handheld computer.
[0176] In use, a user may couple calibration gas leak source 640
which contains gas `A,` to tubing system 615. The user may then
instruct computer 650 to initiate the calibration process for gas
`A.` In response, computer 650 may open remote valves 621, 631 and
close remote valves 611,641. Evacuation pump 620 may be activated,
and may decrease the pressure of tubing system 615 to about 1 Torr,
or possibly lower. Gas `A` may flow to monitoring device 630. The
gas may contain particles, which may be atoms and/or molecules, and
monitoring device 630 may determine the mass of the particles of
the calibration gas. Computer 650 may thereafter store a value
representative of the leak rate corresponding to calibration leak
source 640 which may be based at least in part on the mass of the
particles of the calibration gas.
[0177] In this example, if gas cylinder 610 contains gas `A,` the
user may wish to determine if, and how much, closed valve 605 is
leaking. The user may couple valve 605 to tubing system 615. The
user may instruct computer 650 to begin testing for a leak of gas
`A.`Computer 650 may then open remote valves 611, 621 and close
remote valves 631, 641. Computer 650 may then instruct evacuation
pump 620 to decrease the pressure of tubing system 615 on the
downstream side of valve 605 to about 1 Torr. The computer may
receive a measurement of the pressure inside tubing system 615 from
pressure measuring device 645. Once the pressure of the downstream
side is at some predetermined pressure, for example about 1 Torr or
less, computer 650 may close remote valve 621 and open remote valve
631. Embodiments may also include evacuating the pressure of tubing
system 615 to about 1 mTorr or less. Computer 650 or monitoring
device 630 may then instruct vacuum pump 625 to continue to
decrease the pressure of tubing system 615. In some embodiments
discussed herein, the evacuation pump and/or the vacuum pump may be
referred to as a manifold pump.
[0178] When the pressure of either at least some portion of tubing
system 615, or a detector cell inside monitoring device 630 is
reduced to a threshold level, for example to about 10.sup.-5 to
about 10.sup.-9 Torr, the monitoring device 630 may start scanning
for gases in the tubing system 615. This gas may be gas `A,` and
originate from a leak in closed valve 605. Monitoring device 630
may determine the mass of particles of Gas `A` in tubing system 615
and report the mass to computer 650. Computer 650 may, based
possibly in part on the stored value and the pressure in tubing
system 615, determine a leak rate. The leak rate may be reported to
user, possibly in cubic centimeters per second. In these or other
embodiments, computer 650 may generate a mass spectrum from data
produced by monitoring device 630. The mass spectrum may represent
masses for one or more of a plurality of gases detected by
monitoring device 630.
[0179] If a user desires to test leaks for different types of
gases, the system may be calibrated using different calibration
leak sources containing the different gases. The computer may store
values for each of these sources and allow a user to test for these
types of gases, or possibly other types of gases by interpolating
or extrapolating from stored values for calibrated gases. Apparatus
600 may also include, in some embodiments, a particle counter 660
to count particles created by reactions and bonding occurring
between the subject gas in the gas cylinder and other fluids,
possibly those introduced into tubing system 615 for that express
purpose as discussed above. Particle counter 660 may be located
elsewhere in the apparatus, but is shown in this exemplary
embodiment as being between valve 631 and monitoring device 630.
Similarly, particle counters may be employed in other embodiments
of the invention, including those shown in FIG. 1, FIG. 2 and FIG.
3.
[0180] FIG. 7 shows a block diagram of a method 700 according to
one embodiment of the invention for determining a leak rate of a
gas from a closed valve. At block 710, after a calibration process
is run for a certain gas, a value is stored which is representative
of a certain leak rate for the gas. At block 720, the pressure of
the downstream side of a closed valve is decreased. At block 730,
the pressure of the downstream side of the closed valve is
determined. If the pressure is at a predetermined level, or
possibly lower, the gas is monitored at block 740. A concentration
of gas is determined at block 750. At block 760, the leak rate is
determined, possibly by, at block 765, comparing the determined
concentration of gas to the stored value for the gas determined
during the calibration process. This leak rate may possibly be
reported to a user in cubic centimeters per second.
[0181] FIG. 8 shows a block diagram of a method 800 according to
another embodiment of the invention for characterizing a leak in a
fluid storage container. At block 810, the method may include a
step of pressurizing the fluid storage container with a leak
testing fluid before connecting the container with the leak
characterization apparatus. The leak testing fluid may be
compressed air, hydrogen, oxygen, helium, nitrogen, ammonia,
arsine, phosphine, silane, acetylene, a halogen, a hydrogen halide,
or a boron halide. At block 820, the method may include a step of
connecting a valve on the fluid storage container with a leak
characterization apparatus. The leak characterization apparatus may
include a gas manifold, where the manifold is in fluid
communication with a valve coupler that connects with the valve on
the container and a gas monitoring device.
[0182] At block 830, the method may include a step of evacuating
the gas manifold. At block 840, the method may include a step of
scanning the evacuated manifold with the gas monitoring device for
a plurality of gases that may be emitted by the fluid storage
container. The monitoring device may scan a mass range from about 1
atomic mass unit to about 400 atomic mass units. At block 850, the
method may include a step of generating leak characterization data
about one or more of the plurality of gases. The characterization
data may include a mass spectrum of the plurality of gases emitted
by the fluid storage container. At block 860, the method may
include a step of sending leak characterization data to a processor
operable to calculate leak flow rates for the one or more gases on
a display in electronic communication with the processor. At block
865, the method may further include displaying the leak flow rates
for the one or more gases on a display in electronic communication
with the processor.
[0183] FIG. 9 shows a block diagram of a method 900 according to
another embodiment of the invention for characterizing a leak in a
fluid storage container. At block 910, the method may include a
step of pressurizing the fluid storage container with a leak
testing fluid before placing the container in the evacuatable
chamber. At block 920, the method may include a step of placing the
fluid storage container in an evacuatable chamber fluidly coupled
with a gas monitoring device. The gas monitoring device may scan a
mass range from about 1 atomic mass unit to about 400 atomic mass
units. At block 930, the method may also include a step of
evacuating the chamber.
[0184] At block 940, the method may include a step of scanning the
chamber with the gas monitoring device for a plurality of gases
that may be emitted by the fluid storage container. At block 950,
the method may include a step of generating leak characterization
data about one or more of the plurality of gases. The
characterization data may include a mass spectrum of the plurality
of gases emitted by the fluid storage container. At block 960, the
method may include sending the leak characterization data to a
processor operable to calculate leak flow rates for one or more of
the plurality of gases. At block 965, the method may include
displaying the leak flow rates for the one or more gases on a
display in electronic communication with the processor.
[0185] FIG. 10 shows a block diagram of a method 1000 according to
another embodiment of the invention for characterizing a leak in a
fluid storage container. At block 1010, the method may include
placing a fluid storage container in a chamber. At block 1020, the
method may include evacuating the chamber. At block 1030, the
method may include introducing a first reactive fluid into the
chamber. At block 1040, the method may include scanning the chamber
with a gas monitoring device as in other methods discussed above.
At block 1050, the method may include evacuating the chamber and
scanning the evacuating fluid with a particle counter as discussed
above. At block 1060, the method may include generating leak
characterization data based at least in part on data from the
particle counter. In some embodiments, the method may also include
generating leak characterization data based further in part on data
from the gas monitoring device.
[0186] FIG. 11 is a block diagram illustrating an exemplary
computer system 1100 in which embodiments of the present invention
may be implemented. This example illustrates a computer system 1100
such as may be used, in whole, in part, or with various
modifications, to provide the at least some of the functions of the
pressure measuring device, the monitoring device, the particle
counter, the computer, and/or other components of the invention
such as those discussed above. For example, various functions of
the monitoring device may be controlled by the computer system
1100, including, merely by way of example, determining the
concentration of gases, etc.
[0187] The computer system 1100 is shown comprising hardware
elements that may be electrically coupled via a bus 1190. The
hardware elements may include one or more central processing units
1110, one or more input devices 1120 (e.g., a mouse, a keyboard,
etc.), and one or more output devices 1130 (e.g., a display device,
a printer, etc.). The computer system 1100 may also include one or
more storage device 1140. By way of example, storage device(s) 1140
may be disk drives, optical storage devices, solid-state storage
device such as a random access memory ("RAM") and/or a read-only
memory ("ROM"), which can be programmable, flash-updateable and/or
the like.
[0188] The computer system 1100 may additionally include a
computer-readable storage media reader 1150, a communications
system 1160 (e.g., a modem, a network card (wireless or wired), an
infra-red communication device, Blutetooth.TM. device, cellular
communication device, etc.), and working memory 1180, which may
include RAM and ROM devices as described above. In some
embodiments, the computer system 1100 may also include a processing
acceleration unit 1170, which can include a digital signal
processor, a special-purpose processor and/or the like.
[0189] The computer-readable storage media reader 1150 can further
be connected to a computer-readable storage medium, together (and,
optionally, in combination with storage device(s) 1140)
comprehensively representing remote, local, fixed, and/or removable
storage devices plus storage media for temporarily and/or more
permanently containing computer-readable information. The
communications system 1160 may permit data to be exchanged with a
network, system, computer and/or other component described
above.
[0190] The computer system 1100 may also comprise software
elements, shown as being currently located within a working memory
1180, including an operating system 1184 and/or other code 1188. It
should be appreciated that alternate embodiments of a computer
system 1100 may have numerous variations from that described above.
For example, customized hardware might also be used and/or
particular elements might be implemented in hardware, software
(including portable software, such as applets), or both.
Furthermore, connection to other computing devices such as network
input/output and data acquisition devices may also occur.
[0191] Software of computer system 1100 may include code 1188 for
implementing any or all of the function of the various elements of
the architecture as described herein. For example, software, stored
on and/or executed by a computer system such as system 1100, can
provide the functions of the pressure measuring device, the
monitoring device, the particle counter, the computer, and/or other
components of the invention such as those discussed above. Methods
implementable by software on some of these components have been
discussed above in more detail.
[0192] The invention has now been described in detail for the
purposes of clarity and understanding. However, it will be
appreciated that certain changes and modifications may be practiced
within the scope of the appended claims.
* * * * *