Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Methods and Systems for Counting Particles and Sensing Water
TECHNICAL FIELD
The present invention relates to methods and systems that improve the
reliability of
optical particle counters by assessing the presence and/or influence of water.
More particularly,
the present invention relates to methods and systems that optically count
particulates present in
non-aqueous liquids, such as oils, fuels, and other hydrocarbons, while
accounting for the
deleterious effect on accurate particle readings caused by the presence of
water in the non-
aqueous liquids.
BACKGROUND OF THE INVENTION
l~Ton-aqueous liquids, particularly hydrocarbons such as transformer oils,
motor oils,
transmission fluids, and fuels may become contaminated with particulates
during use. These
contaminated liquids cause corrosion, wear, mechanical damage to and/or poor
performance in
the systems in which they are used. Accordingly, it is desirable to detect the
presence and
quantity of particulates present in these systems to determine when the liquid
must be cleaned,
processed or replaced.
Several methods exist for detecting particulates in
liquids, including non-aqueous liquids. In one method, a sample is taken from
the fluid path to a
2 0 testing facility, mixed with a reagent and the quantity of particulates
determined. This method is
inefficient as it requires excess time and often leads to inaccurate results
caused by
contamination during transfer. In another method the liquid is redirected
through a slipstream
where the liquid is filtered for particulates. The quantity of particulates in
the liquid may be
inferred by sensing the change in the pressure drop across the filter. This
method is reactionary
2 5 and is ineffective in accurately counting the particulates present and
maximizing utilization of
the liquid.
In yet another method, a sample is taken, for example, in a
slipstream, and the particulates are counted by an optical particle counter.
This method is
generally highly efficient, and, under the appropriate conditions, extremely
accurate. However,
3 0 counts from optical particle counters are dramatically influenced by the
level of water present in
a non-aqueous liquid. In many instances, erroneous counts are produced by the
presence of
water and the operator has no convenient, real time method to know that the
counts are wrong.
Some conventional solutions solved this problem by using methods, such as
heating, to remove
the water from the non-aqueous liquid to be tested so that a proper count
could be achieved.
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However, this method may adversely affect the non-aqueous liquid and fails to
address the
combinatorial effect of water and particulate contamination on non-aqueous
liquids.
Summary of the Invention
According to one aspect of the invention, systems for sampling a non-aqueous
liquid may
include both an optical particle counter and a water sensor. The optical
particle counter
generates a signal indicative of the number of particles in the non-aqueous
liquid, and the water
sensor generates a signal indicative of the water content of the non-aqueous
liquid.
According to another aspect of the present invention, methods for sampling a
non-
aqueous liquid may include directing a non-aqueous liquid into an optical
particle counter and
sensing the water content of the non-aqueous liquid.
Systems and methods embodying these aspects of the invention thus allow an
operator to
easily determine whether the particle count is suspect due to the water
content of the non-
aqueous liquid. If the water content reaches a level that may negatively
influence the particle
count, the operator knows that the particle count may be unreliable and he may
take appropriate
action.
According to another aspect of the present invention, methods for sampling a
non-
aqueous liquid may include sensing the water content of a non-aqueous liquid.
The methods
may further include directing the non-aqueous liquid to or away from an
optical particle counter
2 0 in response to the water content.
In systems and methods embodying this aspect of the invention, the non-aqueous
liquid
may be directed to the optical particle counter if the water content is below
a value that can
negatively influence the particle count. If the water content reaches a value
where the optical
counter will likely produce an erroneous result, the non-aqueous liquid may be
redirected away
2 5 from the optical particle counter. When the non-aqueous liquid is directed
away from the optical
particle counter, various embodiments provide for alternative particulate
indicators, treatment
units for decreasing the water content, and/or bypass lines.
Description of the Drawings
3 0 Figure I illustrates a system for sampling a non-aqueous liquid.
Figure 2 illustrates another system for sampling a non-aqueous liquid.
Figure 3 illustrates another system for sampling a non-aqueous liquid.
Figure 4 illustrates another system for sampling a non-aqueous liquid.
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Detailed Description of the Invention
Counting particulates and sensing the water content of non-aqueous liquids,
such as
transformer oils, motor oils, transmission fluids, and fuels, may be
accomplished by operatively
coupling corresponding sensors to the non-aqueous liquid in a variety of
locations. For example,
the sensors may be operatively located directly in a main stream of the non-
aqueous liquid or in a
slipstream, e.g., a flow of the non-aqueous liquid through a secondary path.
Using a slipstream
for testing is generally preferable, although it is not required, so as to
avoid affecting the main
stream, for example, when sensors malfunction or require routine maintenance.
Alternatively,
the optical particle counter and/or the water sensor may be operatively
coupled to the non-
aqueous liquid in a reservoir or a container, such as a tank or bottle.
Examples of systems for sampling a non-aqueous liquid, including counting
particles and
sensing water content, are illustrated in Figures 1 and 2. The sampling
systems 20, 21 generally
comprise an optical particle counter l and a water sensor 2, which may be
disposed to sample the
non-aqueous liquid in a slipstream 4 that is redirected away from and back
toward a main stream
3. The optical particle counter 1 and the water sensor 2 may be operatively
coupled to the non-
aqueous liquid in series, with the optical particle counter 1 upstream,
preferably closely
upstream, of the water sensor 2, as shown in Figure 1, or with the optical
particle counter
downstream, preferably closely downstream, of the water sensor. Alternatively,
as shown in
Figure 2, the optical particle counter l and the water sensor 2 may be
operatively coupled to the
2 0 non-aqueous liquid in parallel. The water sensor 2 and the optical counter
1 are preferably
placed sufficiently close in proximity that one of these components samples
substantially similar
portions of the non-aqueous liquid, e.g., the same portion of the non-aqueous
liquid, soon after
the other, as shown in Figure l, or at approximately the same time as the
other, as in Figure 2.
The optical particle counter 1 and the water sensor 2 may be implemented as
separate
2 5 components which sample the non-aqueous liquid separately, or they may be
implemented as an
integral unit which senses the number of particles and the water content in a
sample of non-
aqueous liquid at substantially the same time.
A wide variety of optical particle counters may be utilized with embodiments
of the
invention. Optical particle counters are preferred because of their accuracy
and reliability in
3 0 counting particulates present in a liquid. Many conventional optical
particle counters comprise a
chamber for testing a liquid, a light source that produces a beam of light
that is received through
a slit into the chamber and reflected through the liquid, and a measuring
device for measuring the
amount of obscuration or scattering caused in the beam of light. These and
other optical systems
provide particularly accurate counts under appropriate conditions. Optical
particle counters are
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readily available from many companies, including Pacific Scientific, that make
a full line of
optical counters that count particulates with various degrees of accuracy.
Similarly, a wide variety of water sensors may be utilized with embodiments of
the
invention. For example, several water sensors are disclosed in International
Publication No. WO
98/46984, entitled "Methods and Systems for Sensing Water in Liquids",
assigned to Pall
Corporation, and incorporated herein by reference. Water sensors may measure
absolute water
content, relative saturation water content or both. Water sensors may be
implemented in a
variety of ways. For example, many conventional water sensors measure the
change in potential
across a sample of non-aqueous liquid caused by the increase in conductivity
due to the presence
of water. Water sensors may also include temperature sensors to account for
changes in the
water content with temperature variations. Water sensors are readily available
from many
companies, including Vaisala Company and Pall Corporation.
In a preferred mode of operation, a portion of the non-aqueous liquid flowing
in the main
stream 3 may be directed into the slipstream 4, past the optical particle
counter 1 and the water
sensor 2, and back to the main stream 3. The non-aqueous liquid may be
directed past the optical
particle counter before, after or at substantially the same time that the non-
aqueous liquid is
directed past the water sensor, depending, for example, on whether the optical
particle counter is
upstream, downstream, in parallel with, or integrated with the water sensor.
As the non-aqueous
liquid flows past the optical particle counter l, it generates a signal
indicative of the number of
2 0 particles in the non-aqueous liquid. As the non-aqueous liquid flows past
the water sensor, it
generates a signal indicative of the water content of the non-aqueous liquid.
The optical particle counter l and the water sensor 2 may each comprise a
processing
circuit and a display that receive the various signals produced by their
corresponding counting or
sensing implementation and produce a visual indication indicative of the
results, which may then
2 5 be interpreted by an operator. The visual indication may be a readout of
the particle count or the
water content. The water sensor may provide a different visual indication,
e.g., one which
simply indicates one or more water content ranges. With the water sensor 2 and
the optical
particle counter 1 sufficiently close, the operator may conveniently and
reliably utilize the visual
indication of the water sensor to determine the implications of the water
content on the particle
3 0 count. The water sensor thus provides a reliability indicator to determine
if the optical particle
counter is producing a reliable result due to the presence of water in the non-
aqueous liquid. For
many non-aqueous liquids, a higher water content may indicate a less reliable
particle count.
Another example of a system for sampling a non-aqueous liquid is shown in Fig.
3. The
system 22 includes an optical particle counter 1 and a water sensor 2 disposed
in a slipstream 4
3 5 of a main stream 3 with the optical particle counter 1 upstream of the
water sensor 2. However,
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the optical particle counter and the water sensor may be operatively coupled
to the non-aqueous
liquid in any other suitable manner, as previously described. For example, the
optical particle
counter and the water sensor may be disposed in the main stream, may be
disposed in series with
the water sensor upstream of the optical particle counter, may be disposed in
parallel or may be
integrated with one another.
The sampling system 22 may further include a processing circuit 5 and a
display 6. The
processing circuit 5 may be coupled to at least one of and preferably both of
the optical particle
counter l and the water sensor 2. The display 6 may be coupled to at least one
of the optical
particle counter l, the water sensor 2, and the processing circuit 5,
preferably at least the
processing circuit 5. In the illustrated embodiment, the processing circuit 5
is shown as a
separate component and it may be implemented in any suitable manner, e.g., as
a general
purpose computer, a microprocessor, a logic array, or any other suitable
processing circuitry.
Similarly, the display 6 is shown as a separate component, and it may be
implemented in any
suitable manner, e.g., as a CRT or a flat panel display andlor one or more
lightable indicators.
However, the processing circuit or the display or both may be integral
components of one
another, the optical particle counter and/or the water sensor. For example,
the processing circuit
and the display may be implemented as a computer with a flat panel or CRT
display and the
computer may be connected to an integral unit comprising the optical particle
counter and the
water sensor. Regardless of how the processing circuit is implemented, the
processing circuit
2 0 may store data received from the optical particle counter and/or the water
sensor so it may be
viewed immediately or at a later time by the operator. The processing circuit
may also download
the data to other processing circuits, e.g., computers for further display or
analysis.
In a preferred mode of operation, a portion of the non-aqueous liquid may be
directed
from the main stream 3 into the slipstream 4, past the optical particle
counter l and the water
2 5 sensor 2, and back to the main stream 3, as previously described. As the
non-aqueous liquid
flows past the optical particle counter l and the water sensor 2, they
respectively generate a
signal indicative of the number of particles in the non-aqueous liquid and a
signal indicative of
the water content of the non-aqueous liquid.
The processing circuit 5 may respond to the signals input from the optical
particle counter
3 0 1 and/or water sensor 2 in a variety of ways. For example, the processing
circuit 5 may receive a
signal indicating water content from the water sensor 2 and a signal
indicating the particle count
from the optical particle counter 1 and then simply generate display signals.
The display signals
may be transferred to the display 6 and result in a readout of the particle
count as determined by
the optical particle counter l and a visual indication of the water content,
e.g., a readout of the
3 5 water content, as determined by the water sensor 2. As disclosed with
respect to the
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embodiments shown in Figures 1 and 2, the water content indication of the
water sensor provides
a reliability indicator for the particle count. If the reliability indicator
indicates that the particle
count is sufficiently unreliable, the operator may simple ignore the count.
Alternatively, the processing circuit 5 may include one or more subcircuits
for further
processing signals input from the optical particle counter 1 and/or the water
sensor 2. For
example, the processing circuit 5 may include a threshold subcircuit which may
store one or
more threshold values. Each threshold value may correspond to a water content
in a given non-
aqueous liquid which calls into question a particle count produced by the
optical particle counter
1. For example, for a given non-aqueous liquid the particle count may be
substantially accurate
below a first predetermined water content value, e.g., below a relative
saturation value of, say, up
to 90% or more; may be somewhat inaccurate between the first predetermined
water content
value and a second predetermined water content value, e.g., between relative
saturation values
of, say, 90% and up to about 100% or more; and may be substantially inaccurate
above the
second predetermined water content value, e.g., above the relative saturation
value of 100%.
Values of 90% and 100% for the first and second predetermined water content
values,
respectively, are merely exemplary. Each predetermined water content value may
vary
depending on factors such as the nature of the non-aqueous liquid and the type
of optical particle
counter and may be determined empirically.
The threshold subcircuit may store the predetermined value(s), e.g., the first
and second
2 0 predetermined values, as the threshold values and may compare them to the
water content signal
received from the water sensor. The threshold subcircuit may be configured in
any suitable
manner for storing the threshold values) and performing the comparison. For
example, the
threshold subcircuit may be implemented as a memory containing a threshold
lookup table, a
comparator for comparing the water content signal with the stored threshold
values, and control
2 5 logic for determining a course of action based on the comparison results.
The processing circuit
5 may then generate a display signal indicative of the number of particles in
the non-aqueous
liquid and one or more display signals in accordance with the output of the
threshold subcircuit.
The display 6 may be configured in a variety of ways to provide an indication
of the
particle count and an indication of the water content as a reliability
indicator for the displayed
30 particle count. For example, the display 6 may include several lightable
indicators, e.g., green,
yellow, and red lamps, in addition to a particle count readout. Depending on
the output of the
threshold subcircuit and, in turn, the display signals generated by the
processing circuit 5: (1) the
green lamp may be lit if the water content is in a first reliability range,
i.e., below the first
threshold value, signalling the operator that the displayed particle count is
likely to be
3 5 substantially accurate; (2) the yellow lamp may be lit if the water
content is in a second
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reliability range, i.e., between the first and second threshold values,
signalling the operator that
the displayed particle count is likely to somewhat inaccurate; and (3) the red
lamp may be lit if
the water content is in a third reliability range, i.e., above the second
threshold value, signalling
the operator that the displayed particle count is likely to be substantially
inaccurate. While the
threshold subcircuit and the display have been described in terms of two
threshold values and
three reliability ranges, more or fewer threshold values and reliability
ranges may be provided.
Further, while the reliability ranges have been implemented in the display by
lightable indicators
such as lamps, other visual indications and/or audible indications, such as
alarms, may be used.
In yet another alternative, the processing circuit may include circuitry which
adjusts the
indication of the particle count input from the particle counter 1 in
accordance with the
indication of the water content input from the water sensor 2. For example,
the water content in
a given non-aqueous liquid may falsely increase, or decrease, the particle
count sensed by the
optical particle counter 1. The relationship between the water content and the
excess counts, or
the count shortfall, may be empirically determined for the non-aqueous liquid
and implemented
in the processing circuit 5, e.g., in an adjustment subcircuit. This
implementation may be
configured in a variety of ways, including a lookup table or a logic array. In
any event, the
adjustment subcircuit may operate on the signal input from the optical
particle counter 1 in
accordance with the signal input from the water sensor 2 to provide an
adjusted indication of the
particle count which more accurately represents the true particle count. The
processing circuit 5
2 0 may then generate a display signal in accordance with an adjusted particle
count signal and
transfer the display signal to the display 6. The display 6 may then provide a
readout of the
adjusted particle count. The display 6 may also provide a reliability
indication such as a readout
of the water content or a visual indication of the reliability range. However,
because the
processing circuit 5 has adjusted the sensed particle count in accordance with
the sensed water
2 5 content to provide an adjusted, more accurate particle count, a
reliability indicator may not be
included with the display 6.
Another example of a system for sampling a non-aqueous liquid is shown in
Figure 4.
The sampling system 23 includes an optical particle counter I, a water sensor
2, and a display 6
coupled to a processing circuit 5, as shown in Figure 3. The optical particle
counter 1 and the
3 0 water sensor 2 are disposed in a slipstream 4 of a main stream 3 with the
optical particle counter
1 downstream of the water sensor 2. However, the components of this system may
be
implemented in other suitable configurations and disposed in the non-aqueous
liquid in any other
suitable manner, such as those previously described with respect to the
embodiments of Figures
1-3. For example, the optical particle counter and the water sensor may be
disposed in the main
3 5 stream, may be disposed in series with the water sensor downstream of the
optical particle
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counter, or may be disposed in parallel. However, in this embodiment, the
optical particle
counter and the water sensor are preferably not located at the same point in
the non-aqueous
liquid stream.
The sampling system further includes a valve arrangement coupled to the
processing
circuit 5. The valve arrangement may be implemented in a wide variety of ways.
In the
illustrated embodiment, the valve arrangement comprises first, second, and
third valves 7, 8, 9,
each coupled to the processing circuit ~. The valve arrangement allows the non-
aqueous liquid
to be directed to the optical particle counter 1 or away from the optical
particle counter 1 in
accordance with the water content sensed by the water sensor 2. For example,
the processing
circuit 5 may receive a water content signal input from the water sensor 2 and
determine if the
water content is within or outside of a range in which the optical particle
counter 1 provides a
reliable, accurate particle count. This function may be implemented, for
example, in a threshold
subcircuit similar to the threshold subcircuit previously described. If the
water content is within
the range, the processing circuit 5 may generate a valve control signal which
operates the first
valve 7 to direct the non-aqueous liquid from the water sensor 2 into the
optical particle counter
1. A readout of the particle count and a reliability indicator may then be
displayed on the display
6. If the water content is outside of the range in which the optical particle
counter 1 provides a
reliable, accurate particle count, the processing circuit 5 may generate a
valve control signal
which operates the first valve 7 to direct the non-aqueous liquid away from
the optical particle
2 0 counter 1.
When the non-aqueous liquid is directed away from the optical particle counter
l, it may
be directed along a wide variety of suitable alternative flow paths. For
example, the sampling
system may include a treatment unit 10 which operates to decrease the water
content in the non-
aqueous liquid. The treatment unit may be implemented in a wide variety of
suitable ways,
2 5 including as a coalescing and/or separating assembly or a heater. The
processing circuit 5 may
generate a valve control signal which operates the second valve 6 to direct
non-aqueous liquid
into the treatment unit 10. Once the water content of the non-aqueous liquid
has been decreased,
the non-aqueous liquid may be directed back to the optical particle counter 1
to obtain a more
accurate particle count. The non-aqueous liquid may pass directly from an
output of the
3 0 treatment unit 10 to the optical particle counter 1. The optical particle
counter 1 may then
provide a signal indicative of a particle count to the processing circuit 5
which then may be
displayed on the display 6. However, because the particle count sensed by the
optical particle
counter 1 is based on a non-aqueous liquid having a lower water content than
that sensed by the
water sensor 2, the reliability indicator shown on the display 6 may be
disabled. Alternatively, a
3 5 second water sensor (not shown) may be operatively coupled to the non-
aqueous liquid flow path
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between the treatment unit and the optical particle counter and may be coupled
to the processing
circuit. Consequently, when the processing circuit directs the non-aqueous
liquid through the
treatment unit, past the second water sensor, and to the optical particle
counter, it may display
the count indicated by the optical particle counter and the water content
indicated by the second
water sensor.
Alternatively, or additionally, when the non-aqueous liquid is directed away
from the
optical particle counter 1, it may simply be directed to a bypass line which
returns the non-
aqueous liquid to the main stream 4. For example, the processing circuit 5 may
generate valve
control signals which operate the second and third valves 8, 9 to direct the
non-aqueous liquid
through a bypass line 14 coupled to the slipstream 4 and hence the main stream
3. The
processing circuit 5 and the display 6 may be configured in any suitable
manner which provides
an indication that the optical particle counter is being bypassed.
As yet another alternative. or addition, when the non-aqueous liquid is
directed away
from the optical particle counter it may be directed to another particulate
indicator 11, for
example, any particulate indicator other than an optical particle counter
which is less sensitive to
water content. Preferably, the particulate indicator 11 includes a porous
medium, such as a
porous mesh, through which the non-aqueous liquid flows. A fluid flow
characteristic, such as
differential pressure across the porous medium, is sensed to provide an
indication of the quantity
of particulates in the non-aqueous liquid. The particulate indicator 11 may
generate a signal
2 0 indicative of the quantity of particulates sensed and the signal may be
provided to the processing
circuit 5. The processing circuit 5, in turn, may display the particulate
indication on the display
6, with or without the reliability indicator. From the particulate indicator
11, the non-aqueous
liquid may be returned to the main stream 3.
The sampling system 23 shown in Figure 4 may operate independently of any main
2 5 system controller or it may operate in conjunction with a main system
controller. For example,
the processing circuit 5 may be coupled to a system controller 12 to provide a
variety of data and
instructions between them. For example, the processing circuit 5 may relay the
water content
signal provided by the water sensor 2, the particle count signal generated by
the optical particle
counter 1, and/or the particulate signal generated by the particulate
indicator 11 to the system
3 0 controller 12. Depending on the value of the signals, the system
controller 12 may then control
the main system in a variety of ways. For example, if the water content or the
particulate content
as indicated by the water sensor 2, the optical particle counter 1 or the
particulate indicator 11 is
unusually high, the system controller may shut off the main stream 3, e.g., by
operating a main
valve 13 accordingly.
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Various aspects of the invention have been described with respect to many
embodiments.
However, the invention is not limited to these embodiments. For example, one
or more of the
features of any of these embodiments may be combined with one or more of the
features of the
other embodiments without departing from the scope of the invention. Further,
one or more of
5 the features of any of these embodiments may be modified or omitted without
departing from the
scope of the invention. Accordingly, the various aspects of the invention
include any and all
methods and systems encompassed within the spirit and scope of the invention
as defined by the
following claims.
