U.S. patent application number 12/473457 was filed with the patent office on 2010-12-02 for real time pump monitoring.
This patent application is currently assigned to Halliburton Energy Services, Inc.. Invention is credited to David W. Looper, Stanley V. Stephenson, David M. Stribling, Chris N. Taliaferro.
Application Number | 20100300683 12/473457 |
Document ID | / |
Family ID | 42732784 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100300683 |
Kind Code |
A1 |
Looper; David W. ; et
al. |
December 2, 2010 |
Real Time Pump Monitoring
Abstract
A system and method for monitoring operation of a pump are
disclosed herein. The methods and systems make use of acoustic
sensors to collect and analyze data in order to detect cavitation.
The disclosed methods and systems may also be used to detect valve
damage. The pump may be a positive displacement pump that is
employed in a wellbore servicing operation such as pumping a
wellbore servicing fluid into a wellbore.
Inventors: |
Looper; David W.; (Duncan,
OK) ; Taliaferro; Chris N.; (Duncan, OK) ;
Stribling; David M.; (Duncan, OK) ; Stephenson;
Stanley V.; (Duncan, OK) |
Correspondence
Address: |
JOHN W. WUSTENBERG
P.O. BOX 1431
DUNCAN
OK
73536
US
|
Assignee: |
Halliburton Energy Services,
Inc.
Houston
TX
|
Family ID: |
42732784 |
Appl. No.: |
12/473457 |
Filed: |
May 28, 2009 |
Current U.S.
Class: |
166/250.01 |
Current CPC
Class: |
E21B 21/06 20130101;
E21B 47/008 20200501 |
Class at
Publication: |
166/250.01 |
International
Class: |
E21B 47/00 20060101
E21B047/00; E21B 43/00 20060101 E21B043/00 |
Claims
1. A method of servicing a wellbore, comprising: establishing
baseline acoustic data for a pump; pumping a wellbore servicing
fluid into the wellbore with the pump; gathering service acoustic
data for the pump while pumping the wellbore servicing fluid;
comparing the baseline acoustic data to the service acoustic data;
and determining a presence or absence of an abnormal operating
condition of the pump.
2. The method of claim 1 wherein the baseline acoustic data and the
service acoustic data are provided by a knock sensor coupled to the
pump.
3. The method of claim 1 wherein the baseline acoustic data, the
service acoustic data, or both are time domain data.
4. The method of claim 1 further comprising converting the time
domain data to frequency domain data.
5. The method of claim 4 wherein the baseline acoustic data and the
service acoustic data are compared at a frequency range of from
greater than about 0 to about 5000 Hz.
6. The method of claim 5 wherein the comparing further comprises
comparing the magnitude of the service acoustic data to the
baseline acoustic data and determining the presence of an abnormal
operating condition of the pump when the service acoustic data is
at least 50% greater than the service data.
7. The method of claim 6 wherein the service acoustic data and the
baseline acoustic data are measures in g's, are compared at a first
sub-frequency range of from about 2,000 to about 3,000 Hz, and the
abnormal operating condition is identified as cavitation.
8. The method of claim 7 wherein the service acoustic data and the
baseline acoustic compared at a second sub-frequency range of from
about 3,500 to about 4,500 Hz, and the abnormal operating condition
is identified as cavitation.
9. The method of claim 6 wherein the service acoustic data and the
baseline acoustic data are measures in g's, are compared at a first
sub-frequency range of from about 4,500 to about 5,000 Hz, and the
abnormal operating condition is identified as valve leakage.
10. The method of claim 9 wherein the service acoustic data and the
baseline acoustic compared at a second sub-frequency range of from
about 1,750 to about 2,250 Hz, and the abnormal operating condition
is identified as valve leakage.
11. The method of claim 3 wherein the comparing further comprises
comparing the service acoustic data to the baseline acoustic data
and determining the presence of an abnormal operating condition of
the pump when valve bounce is detected upon closing of a suction
valve of the pump.
12. The method of claim 11 wherein the abnormal operating condition
is cavitation.
13. The method of claim 3 wherein the comparing further comprises
comparing the service acoustic data to the baseline acoustic data
and determining as present an abnormal operating condition of the
pump when lag is detected in closure of a valve of the pump.
14. The method of claim 13 wherein the lag is detected in
comparison to an expected valve closure time based upon position of
a plunger in the pump.
15. The method of claim 13 wherein the abnormal operating condition
is cavitation.
16. The method of claim 1 wherein the pump is a positive
displacement pump.
17. The method of claim 2 wherein the pump is a positive
displacement pump fluid end and the knock sensor is mounted
adjacent the fluid end.
18. The method of claim 17 wherein the pump is operated at from
about 100 to about 500 rpm.
19. The method of claim 1 further comprising sounding an alarm upon
determining the presence of an abnormal operating condition.
20. The method of claim 1 further comprising adjusting one or more
pump system parameters upon determining the presence of an abnormal
operating condition.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
BACKGROUND
[0002] 1. Field of the Invention
[0003] This invention relates generally to the field of pumps and
improved systems and methods for monitoring and detecting potential
problems or faults in pumps. More specifically, the invention
relates to methods and systems for real time sensing of cavitation
and/or valve leakage in pumps, for example positive displacement
pumps used in wellbore servicing operations.
[0004] 2. Background of the Invention
[0005] Wellbore servicing systems and equipment may include a
variety of pumps, which require maintenance over time. With
conventional maintenance strategies such as exception-based and
periodic checking, faults developed in pumps have to be detected by
human experts through physical examination and other off-line tests
(e.g., metal wear analysis) during a routine maintenance in order
for corrective action to be taken. Faults that go undetected during
a regular maintenance check-up may lead to catastrophic failure and
unscheduled shutdown of the wellbore service. The probability of an
unscheduled shutdown increases as the time period between
successive maintenance inspections increases. The frequency of
performing maintenance, however, is limited by availability of
man-power and financial resources and hence is not easily
increased. Some maintenance inspections, such as valve, plunger, or
packing inspection may require stopping the process or even
disassembling machinery. The lost production time may cost many
times more than the labor cost involved. There is also a
possibility that the reassembled machine may fail due to an
assembly error or high start up stresses for example. Finally,
periodically replacing components (via routine preventive
maintenance) such as bearings, seals, or valves is costly since the
service life of good components may unnecessarily be cut short.
[0006] Cavitation, leakage and valve damage are common
problems/faults encountered with pumps. In particular, cavitation
can cause accelerated wear and mechanical damage to pump
components, couplings, gear trains, and drive motors. Cavitation is
the formation of vapor bubbles in the inlet flow regime or the
suction zone/stroke of the pump. This condition occurs when local
pressure drops to below the vapor pressure of the liquid being
pumped. These vapor bubbles collapse or implode when they enter a
high pressure zone (e.g., at the discharge valve during the
discharge/power stroke) of the pump causing erosion of and/or
damage to pump components. If a pump runs for an extended period
under cavitation conditions, permanent damage may occur to the pump
structure and accelerated wear and deterioration of pump internal
surfaces and seals may occur. Detection of such conditions before
they become severe or prolonged can help to avoid
cavitation-induced damage to the pump and facilitate extended
wellbore up time. Such detection also can avoid accelerated pump
wear and unexpected failures and further enable a well planned and
cost-effective maintenance routine. Depending on the type of pump,
other problems can occur such as inlet or outlet blockage, leakage
of air into the system due to faulty pump seals or valves, leaky or
damaged valves, internal parts impacting the pump casing, etc.
Consequently, there is a need for improved systems and methods for
monitoring and detecting potential problems or faults in pumps.
BRIEF SUMMARY
[0007] Disclosed herein is a method of servicing a wellbore,
comprising establishing baseline acoustic data for a pump, pumping
a wellbore servicing fluid into the wellbore with the pump,
gathering service acoustic data for the pump while pumping the
wellbore servicing fluid, comparing the baseline acoustic data to
the service acoustic data, and determining a presence or absence of
an abnormal operating condition of the pump.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] For a detailed description of the preferred embodiments of
the invention, reference will now be made to the accompanying
drawings in which:
[0009] FIG. 1 illustrates a block diagram of an embodiment of a
pump system for monitoring and/or detecting pump problems;
[0010] FIG. 2A illustrates a cross-sectional view of positive
displacement pump that may be used with embodiments of the pump
system;
[0011] FIG. 2B illustrates a top view of positive displacement pump
that may be used with embodiments of the pump system;
[0012] FIG. 3 illustrates a flow diagram of an embodiment of a
method of detecting an abnormal operating condition in a pump;
[0013] FIGS. 4A-C are plots of time domain acoustic data measured
by an acoustic sensor for a pump;
[0014] FIG. 5 is a plot of frequency domain acoustic data measured
by an acoustic sensor for a pump;
[0015] FIGS. 6A-C are power spectrums of acoustic data measured by
an acoustic sensor for a pump;
[0016] FIGS. 7A-C are plots of acoustic data measured by an
acoustic sensor from a pump;
[0017] FIGS. 8-11 are plots of g's over a test period of time for a
cavitating pump operating in gears 3-6, respectively; and
[0018] FIGS. 12-15 are plots of g's over a test period of time for
a pump having a leaky valve and operating in gears 3-6,
respectively.
NOTATION AND NOMENCLATURE
[0019] Certain terms are used throughout the following description
and claims to refer to particular system components. This document
does not intend to distinguish between components that differ in
name but not function.
[0020] In the following discussion and in the claims, the terms
"including" and "comprising" are used in an open-ended fashion, and
thus should be interpreted to mean "including, but not limited to .
. . ". Also, the term "couple" or "couples" is intended to mean
either an indirect or direct connection. Thus, if a first device
couples to a second device, that connection may be through a direct
connection, or through an indirect connection via other devices and
connections.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] FIG. 1 is a block diagram of an embodiment of a system 100
for detecting cavitation and/or valve damage in a pump 146. System
100 generally comprises a pump 146 having input 101 and output 111,
an acoustic sensor 102 connected to and/or disposed proximate to
pump 146, an engine 106, and a transmission 108, which may all be
co-located, for example mounted on a trailer and/or housed within
an enclosure 109. In an embodiment, the acoustic sensor 102 is
connected/mounted to or proximate a fluid end of the pump 146.
Acoustic sensor 102 may be coupled via signal 110 to a monitoring
system 121 (e.g., a data acquisition, processing, and/or control
system), which may either be located locally (e.g., integral with)
the pump system 100 or may be located remotely (e.g., distributed)
from system 100. The monitoring system 121 may be integral with
and/or further coupled to (e.g., via signal 112) a control until
120, which may monitor the operation of the system 100 (e.g., pump
146) and provide control signals to the system 100 (e.g., pump 146
and/or component thereof such as engine 106 and/or transmission
108) during the course of an operation performed by system 100
(e.g., a pumping operation such as pumping a wellbore servicing
fluid downhole).
[0022] In an embodiment, pump 146 is a positive displacement pump.
FIGS. 2A and 2B show embodiments of a positive displacement pump,
which may be used as part of the disclosed systems and methods.
FIG. 2A is a cross-sectional view of a portion of an embodiment of
a positive displacement pump 246, which may be used as part of the
disclosed systems and methods. Positive displacement pump 246 may
be operated in a conventional manner. The positive displacement
pump 246 includes an input 298, which receives fluid material from
a fluid source (e.g., a suction line, storage or mix tank,
discharge from a boost pump such as a centrifugal pump, etc.), and
an output 200, which may output fluid material to a discharge
source (e.g., a flowmeter, distribution header, discharge line,
wellhead, etc.). A pressure transducer may be located adjacent the
output 200, so that a component of system 100 (e.g., control unit
120) monitors pressure of the fluid material output from the
positive displacement pump 246.
[0023] As shown in FIG. 2A, the positive displacement pump 246
comprises a fluid end 105 having a suction valve 202 for
controlling the receipt of fluid material through the input 298 and
a discharge valve 204 for controlling the output of fluid material
through the output 200. Also, the positive displacement pump 246
includes a plunger 206 for controlling a pressure in a chamber 208
of the positive displacement pump 246, so that fluid material is
suitably received into the chamber 208 via the input 298 and
suction valve 202 and suitably discharged from the chamber 208 via
the discharge valve 204 and the output 200. In embodiments, the
sensor 102 is directly/indirectly attached to the fluid end 105 of
the pump 246, for example adjacent the input 298 and/or output 200
or on the outer surface or housing of the fluid end.
[0024] As shown in FIG. 2A, the positive displacement pump 246
comprises a power end 103. The plunger 206 is coupled through a
crosshead to a connecting rod 210. The connecting rod 210 is
connected to a crankshaft 212. An engine 106 may be coupled to
crankshaft 212 through a transmission 108 and a drive shaft (as
shown in FIGS. 1 and 2). Through the transmission 108, the engine
106 rotates the drive shaft and, in turn, rotates the crankshaft
212. At a rate of once per 360.degree. rotation of the crankshaft
212, the connecting rod 210 moves the plunger 206 into and out of
the chamber 208, completing a suction and discharge stroke of the
pump.
[0025] Referring to FIG. 2A, a single, representative chamber of a
positive displacement pump is shown. In an embodiment as shown in
FIG. 2B, the positive displacement pump 246 includes two or more
substantially identical chambers, for example three chambers 130
are connected to a common crankshaft 212. The crankshafts of those
portions are connected to one another, yet aligned at 120.degree.
intervals relative to one another. Accordingly, each portion
operates 120.degree. and 240.degree. out-of-phase with the other
two portions, respectively, so that such portions collectively
generate a more uniform rate of flow.
[0026] During operation of pump, as plunger 206 moves away from
valves 202, 204 (i.e., toward the left in FIG. 2A), the pressure
drop or vacuum in chamber 208 causes discharge valve 204 to close
and suction valve 202 to open, allowing fluid to enter chamber 208.
This phase may be known as the "suction stroke." During the
"discharge stroke," plunger 206 moves back towards the valves 202,
204 (i.e., toward the right in FIG. 2A), forcing suction valve 202
to close and discharge valve 204 to open. Fluid may then be forced
from chamber 208 through the open discharge valve 204.
[0027] Without being limited by theory, when insufficient fluid
enters the chamber 208 from suction valve 202, bubbles may be
formed inside chamber 208 (i.e., cavitation occurs). During the
discharge stroke, the presence of the bubbles causes a delay in the
opening of discharge valve 204 because increased pressure is
required to collapse the formed bubbles. The cavitation bubbles can
inflict damage to the inner surfaces of the pump through microjets
and shockwaves (e.g., pressure waves) caused by bubble collapse.
The collapsing bubbles may also cause acoustic vibrations (e.g.,
pressure waves) in the pump chamber 208 and also cause valve
bounce, and the vibrations produced by cavitation and/or valve
bounce may be detected by an acoustic sensor 102 such as without
limitation, a knock sensor, as described herein.
[0028] Acoustic sensor 102 may be any sensor capable of monitoring
or detecting acoustic signals. In one embodiment, acoustic sensor
102 is a commercially available knock sensor such as Bosch.RTM.
Knock Sensor model KS-P. Other examples of acoustic sensors include
without limitation, microphones, sonar, photoacoustic sensors,
acoustic wave sensors, or combinations thereof. As discussed in
more detail herein, the acoustic sensor 102 is effective to detect
energy signals produced by cavitation and/or valve leakage in the
pump. Accordingly, one or more acoustic sensors may be mounted
directly on the pump (e.g., bolted or attached to the pump housing
or outer surface) or indirectly on the pump (e.g., bolted or
magnetically attached to a pump mount or frame). In an embodiment,
the acoustic sensor is mounted adjacent the fluid end of the pump
(e.g., where fluid enters/exists the pump), in contrast to the
power end of the pump (e.g., where the engine/transmission are
connected to the pump). In an embodiment, one or more acoustic
sensors are attached directly/indirectly, adjacent/proximate to the
suction and/or discharge valves on the fluid end of the pump. In
some embodiments, acoustic sensor 102 may comprise a piezoelectric
element. The frequency over which the acoustic sensor is capable of
detecting acoustic energy is referred to as the knock sensor's
frequency response range. In various embodiments, the knock sensor
may have a frequency response range of from about 1 Hz to about
20,000 Hz, alternatively from about 1 Hz to about 10,000 Hz,
alternatively from about 1 Hz to about 5000 Hz, alternatively from
about 100 Hz to about 5000 Hz, alternatively from about 1000 Hz to
about 5000 Hz. In an embodiment, the knock sensor (or other
component of the system 100 such as control unit 120 or monitoring
system 121) may employ one or more filters to alter the frequency
response range of the knock sensor. In an embodiment, the knock
sensor detects acoustic energy falling within the sensor's
frequency response range and provides an output as signal 110 to
data acquisition, processing, and control system 121. For example,
the knock sensor may output a voltage signal (e.g., a millivoltage
signal). In an embodiment, the knock sensor comprises a
piezoelectric element that provides the voltage signal.
[0029] Referring again to FIG. 1, monitoring system 121 may
comprise a computing device or system such as without limitation,
computers, laptops, personal digital assistants, or combinations
thereof having one or more data acquisition, processing, and
control components residing therein in software, firmware, and/or
hardware. Preferably, various of the data acquisition, processing,
and control functions may be integrated into a single device.
However, in other embodiments, data acquisition, data processing,
and control functions may be divided into separate devices. The
monitoring system 121 is capable of transmitting and/or receiving
data to/from various components of the system 100.
[0030] The monitoring system 121 may comprise various components,
such as a processor 115 (a central processor unit, CPU), a memory
117, and a communications unit 160. The processor 115 may comprise
one or more microcontrollers, microprocessors, etc., that are
capable of executing a variety of software components. The memory
117 may comprise various memory portions, where a number of types
of data (e.g., internal data, external data instructions, software
codes, status data, diagnostic data, testing profiles, operating
guidelines, etc.) may be stored. The memory 117 may store various
tables or other database content that could be used by the pump
system 100 to control operations thereof. The memory 117 may
comprise read only memory (ROM), random access memory (RAM) dynamic
random access memory (DRAM), electrically erasable programmable
read-only memory (EEPROM), flash memory, hard drives, removable
drives, etc.
[0031] It is understood that by programming and/or loading
executable instructions onto the monitoring system 121, at least
one of the processor and/or memory are changed, transforming the
monitoring system 121 in part into a particular machine or
apparatus having the novel functionality taught by the present
disclosure. It is fundamental to the electrical engineering and
software engineering arts that functionality that can be
implemented by loading executable software into a computer can be
converted to a hardware implementation by well known design rules.
Decisions between implementing a concept in software versus
hardware typically hinge on considerations of stability of the
design and numbers of units to be produced rather than any issues
involved in translating from the software domain to the hardware
domain. Generally, a design that is still subject to frequent
change may be preferred to be implemented in software, because
re-spinning a hardware implementation is more expensive than
re-spinning a software design. Generally, a design that is stable
that will be produced in large volume may be preferred to be
implemented in hardware, for example in an application specific
integrated circuit (ASIC), because for large production runs the
hardware implementation may be less expensive than the software
implementation. Often a design may be developed and tested in a
software form and later transformed, by well known design rules, to
an equivalent hardware implementation in an application specific
integrated circuit that hardwires the instructions of the software.
In the same manner as a machine controlled by a new ASIC is a
particular machine or apparatus, likewise a computer that has been
programmed and/or loaded with executable instructions may be viewed
as a particular machine or apparatus.
[0032] The communication unit 160 is operable to facilitate
communications with other components of the system 100. In
particular, the communication unit 160 is capable of providing
transmission and reception of electronic signals to and from
acoustic sensor 102 via signal 110 and/or control unit 120 via
signal 112. For example, communication unit 160 may be a wireless
device capable of transmitting and receiving signals to/from
acoustic sensor 102 and/or control unit 120 without the use of
wires. Alternatively, communication unit 160 may be a wired device
capable of transmitting and receiving signals to/from acoustic
sensor 102 and/or control unit 120 using wires. In an embodiment,
monitoring system 121 is a commercially available data acquisition,
processing, and control system such as a Rockwell Automation.RTM.
XM-120 general monitoring device. In an embodiment, the monitoring
system 121 receives an analog input (e.g., a voltage signal) from
the acoustic sensor 102 and may further process the analog input
signal, for example converting the signal from analog to digital
and/or conversion from time domain to frequency domain, e.g., via a
(Fast) Fourier transform (FFT). In an embodiment, the signal from
the acoustic sensor 102 is converted from a voltage signal to a
signal measured in g's via a conversion factor. In an embodiment,
the conversion factor is about 26 mV/g.
[0033] Now referring to FIG. 3, a flowchart of an embodiment of a
method for detecting an abnormal operating condition (e.g.,
cavitation, valve bounce, valve leakage) in a pump is shown. The
method of FIG. 3 may be implemented via the system of FIG. 1. In
block 301, pump 146 may be operated under nominal operating
conditions. Typically, pump 146 during this stage is operating
without cavitation or other defect such a valve bounce or leakage.
During nominal pump operation, the acoustic sensor 102 may
continuously monitor acoustic data from the pump assembly as in
block 303. As used herein, "nominal pump operation" may refer to
pump operation without cavitation, valve damage or other
abnormalities. The system 100 detects abnormalities by acquiring
acoustic data during one or more pump cycles. Preferably, system
100 uses a knock sensor to acquire the acoustic data. However, as
noted above, any suitable acoustic sensor may be used to collect
acoustic data. The acoustic data collected during nominal pump
operation in block 301 may be used to establish a baseline
measurement for a normally operating pump (e.g., non-cavitating) in
block 303, referred to herein as baseline data. In an embodiment, a
baseline measurement of acoustic data is established for nominal
operation of original equipment manufacture (OEM) equipment prior
to or shortly after placing such equipment into service for the
first time or alternatively for nominal operation of
remanufactured, repaired, or overhauled equipment prior to or
shortly after placing such equipment back into service. The
baseline data may be stored in memory 117 for later comparison with
acoustic data collected during real time operation of the pump
while in service (e.g., while operating on a job), referred to
herein as service data.
[0034] Once baseline data has been established, service data may be
further collected or monitored during real-time operation of the
pump in block 305 (for example, during a pumping operation at a
well site such as pumping a wellbore servicing fluid down hole).
Service data may be collected continuously (e.g., whenever the pump
is in operation) or intermittently (upon certain intervals of pump
operation, e.g., time intervals, stroke intervals, volume
intervals, etc.), and may likewise be stored in memory if desired.
The service data may then be compared and/or analyzed to the
baseline data in block 307. Again, the comparison of block 307 may
be carried out in real time during operation of the pump during the
service, or the service data may be stored and compared to the
baseline data subsequent to performance of the pumping service. The
comparison of baseline to service acoustic data is analyzed to
detect indicators of abnormal pump operation (e.g., increased
acoustic magnitude at certain frequencies indicating cavitation,
valve bounce, valve mis-timing, valve leakage, etc.). Several
different analysis techniques (e.g., comparison of time domain
data, frequency domain data, and/or power spectrum data) may be
used when comparing the service data with the baseline data which
will be described in more detail below. Upon analysis of the
acoustic data and detection of abnormal pump operation in block
309, one or more pump, system, and or service/job parameters may be
adjusted in block 313 to correct and/or compensate for the abnormal
condition (e.g., reduce pump cavitation). Examples of pump
parameters that may be adjusted include pump speed, boost pressure,
flow rate, fluid properties, etc., and such parameters may be
adjusted via the control unit 120. Additionally and/or
alternatively, other remedial measures or maintenance may be
performed where pump cavitation or other operating problems are
detected. Following remedial measures or maintenance, further
service data may be collected and monitored by returning to block
310 and/or additional baseline data may be collected by returning
to block 303.
[0035] In an embodiment, the acoustic sensor 102 outputs a voltage
signal to the monitoring system 121, which correlates the voltage
signal to an magnitude measurement such as g's or decibels over
time and establishes baseline and service data using such
measurements to produce time domain data such as that shown in
FIGS. 4A-C. In some embodiments, a given data point may represent
an average of several data readings for a given period of time
(e.g., 1 second), and such points may be represented as a root mean
square of the several data readings for the given period. While
acoustic data may be collected over a wide frequency range (e.g.,
the acoustic sensor's frequency response range of from about 1 Hz
to about 20,000 Hz), analysis need not cover the entire measured or
sampled frequency range, and in some embodiments a frequency
sub-range (e.g., 1,000 to 5,000 Hz) may be analyzed via comparison
of baseline data to service data. The time domain baseline data and
the time domain service data may be compared to determine if
abnormal pump operating conditions exist as described in more
detail herein.
[0036] In addition, acoustic data may be analyzed at specific
frequencies in detecting pump abnormalities. Time domain acoustic
data (e.g., voltage readings converted to energy readings over a
period of time to establish baseline and service data sets) may be
collected using the acoustic sensor. The time domain acoustic data
may then be transformed into frequency domain acoustic data using a
transform algorithm, for example a Fast Fourier Transform (FFT)
algorithm. In some embodiments, the entire measured frequency range
(e.g., the acoustic sensor's frequency response range of from about
1 Hz to about 20,000 Hz) need not be transformed and/or compared,
provided however that in some instances a larger sub-range of the
measured data (e.g., from 1 Hz to 10,000 Hz of the time domain
data) may be needed in order to produce transformed data in the
desired frequency range for analysis (e.g., 1 Hz to 5,000 Hz), as
shown in FIG. 5. The frequency domain baseline data and the
frequency domain service data may be compared to determine if
abnormal pump operating conditions exist as described in more
detail herein.
[0037] Alternatively, the power spectrum may be derived from the
transformed baseline data and the transformed service data over a
given frequency range. Referring to FIGS. 6A-C, the power spectrum
may be represented as a 2-D plot of magnitude (e.g., power) on the
y-axis as a function of frequency on the x-axis. Alternatively, the
power spectrum may be further represented as a 3-D plot of
magnitude (e.g., power) on the y-axis as a function of frequency on
the x-axis and time on the z-axis. The power spectrum of the
baseline data may be compared to the power spectrum of the service
data over a given frequency range to determine if abnormal pump
operating conditions exist as described in more detail herein.
[0038] In an embodiment, baseline and service data (e.g., time
domain, frequency domain, and/or power spectrum data) may be
compared and analyzed to detect one or more indicators of pump
cavitation. For example, indicators of pump cavitation include data
magnitude (e.g., increases in data magnitude), valve bounce (e.g.,
bounce of the discharge valve upon closing), valve lag (e.g., a
time lag in closure of the suction valve), or combinations thereof.
In embodiments, such indicators may be detected by analyzing data
in the time domain and/or the frequency domain as described herein.
Without being limited by theory, one cause of valve bounce may be
the collapse of the cavitation bubbles in the chamber during
cavitation. Accordingly, valve bounce may serve as another
indicator of cavitation. Likewise, an increase in signal magnitude
(e.g., g's) over baseline may indicate that the plunger is slamming
or "hammering" closed upon collapse of bubbles, and thus may
likewise indicate cavitation. FIGS. 4A-C show various indicators of
pump cavitation for data in the time domain collected from a knock
sensor located on the fluid end (FE) of a positive displacement
pump. More specifically, FIG. 4A is time domain baseline data for a
non-cavitating pump, FIG. 4B is time domain service data for a
cavitating pump, and FIG. 4C is an overlay of the data from FIGS.
4A and 4B. Baseline acoustic data (as shown in FIG. 4A for a
non-cavitating pump) and service acoustic data (as shown in FIG. 4B
for a cavitating pump) in the time domain may be collected using an
acoustic sensor, and such data may be analyzed over a given time
period (for example the time period corresponding to one or more
pump cycles).
[0039] In an embodiment, data magnitude is an indicator of abnormal
pump operation (e.g., cavitation). As can be seen by comparing the
scale of the y-axis on the right sides of FIGS. 4A and 4B, the
cavitating pump produces a higher signal magnitude as measured in
g's than the non-cavitating pump. The majority of the data in the
non-cavitating pump is below 2 g's, with only one peak
significantly above 2 g's (i.e., the peak at about 0.225 seconds).
In contrast, the cavitating pump shows numerous peaks over 5 g's,
and several peaks over 10 g's. Thus, in an embodiment, acoustic
data (e.g., time domain data) may be analyzed (e.g., in block 307
of FIG. 3) by comparing baseline data to service data to determine
whether there is an increase in measured magnitude, for example an
increase in decibel level and/or g's. In an embodiment, if the
service data magnitude (or an average thereof such as root mean
square or other curve fit) is from about 2, 3, 4, 5, 6, 7, 8, 9, or
10 g's greater than the baseline data magnitude (or an average
thereof such as root mean square or other curve fit), then the
monitoring system 121 may signal a user (e.g., sound an alarm
and/or send an alarm signal to control unit 120) that abnormal pump
operation (e.g., cavitation) has been detected and one or more pump
system parameters may be altered to implement corrective action. In
another embodiment, if the service decibel level (or an average
thereof such as root mean square or other curve fit) is from about
3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25 or 30 dB greater than the
baseline decibel level or an average thereof such as root mean
square or other curve fit), then the monitoring system 121 may
signal a user (e.g., sound an alarm and/or send an alarm signal to
control unit 120) that abnormal pump operation (e.g., cavitation)
has been detected and one or more pump system parameters may be
altered to implement corrective action. In another embodiment, if
the service data magnitude (or an average thereof such as root mean
square or other curve fit) is from about 50, 100, 150, 200, 250,
300, 350, 400, 450, or 500% greater than the baseline data
magnitude (or an average thereof such as root mean square or other
curve fit), then the monitoring system 121 may signal a user (e.g.,
sound an alarm and/or send an alarm signal to control unit 120)
that abnormal pump operation (e.g., cavitation) has been detected
and one or more pump system parameters may be altered to implement
corrective action.
[0040] In an embodiment, valve bounce is an indicator of abnormal
pump operation (e.g., cavitation). Such normal valve closure and/or
bounce profiles may be established as baseline data as described
previously and then compared to service data to detect undesired
closure and/or bounce profiles that may be indicative of abnormal
pump operation (e.g., cavitation). For example, the service data
may be analyzed for one or more peaks of acoustic energy after a
peak indicating normal valve closing time to detect bounce. More
specifically, FIG. 4A shows the baseline data of a non-cavitating
pump for one pump cycle, whereas FIG. 4B shows the service data of
a cavitating pump for one pump cycle. Valve bounce as labeled in
FIG. 4B is indicated by a second spike or peak in acoustic energy
after the initial peak of energy (the nominal valve closing peak).
As shown in FIG. 4A, the fluid end (FE) discharge valve may bounce
upon closure as denoted on the figure, which is somewhat normal in
non-cavitating operation due to the spring closure bias on the
discharge valve. A similar discharge valve bounce is shown in FIG.
4B as well. However, in a cavitating pump, a valve bounce is
detected upon closing of the suction valve (in contrast to the
normal bounce on closure of the discharge valve), as denoted on
FIG. 4B. No such bounce on closure of the suction valve is
indicated in the non-cavitating pump of FIG. 4A. Thus, these plots
show that bounce on closure of the suction valve is indicative of
cavitation, which without wishing to be limited by theory, may be
due to the volume of fluid being less (e.g., more air present),
such that the spring may slam the valve closed more violently
because the spring is typically sized for the desired operational
rate and density of the liquid (in contrast to air). As such, if
the control unit 120 detects valve bounce (e.g., suction valve
bounce) from acoustic data, it may sound an alarm and/or send a
signal to change one or more pump system parameters in order to
reduce cavitation.
[0041] In an embodiment, valve lag is an indicator of abnormal pump
operation (e.g., cavitation). As used herein, valve lag refers to a
time delay or lag in closure of a valve. Without being limited by
theory, when cavitating the suction valve may close several
milliseconds later than a suction valve during normal
non-cavitating operation, which may be a function of bubble
collapse. Thus, service acoustic data may be compared to baseline
acoustic data to detect valve lag, as shown in FIG. 4C. When
service data from a cavitating pump is overlain with baseline data
from a non-cavitating pump, delays in valve closure (e.g., suction
valve lag, discharge valve lag, or both) are clearly identifiable
as denoted on FIG. 4C. Furthermore, such lag may be measured and/or
detected in comparison to the expected valve closure time based
upon position of the plunger, as indicated for example by a timing
mark located on a mechanical component of the pump such as the cam
shaft. The expected valve closure time is indicated by the start of
the square notch in the plunger position line in FIG. 4C, as so
labeled. As is shown, the non-cavitating pump indicates closure in
close correlation with the expected valve closure time as indicated
by plunger position whereas the cavitating pump shows valve lag
from expected valve closure time. As such, if the control unit 120
detects valve lag from acoustic data, it may sound an alarm and/or
send a signal to change one or more pump system parameters in order
to reduce cavitation.
[0042] In another embodiment, baseline and service time domain
acoustic data can be transformed to corresponding baseline and
service frequency domain acoustic data and comparisons made to
detect pump abnormalities such as cavitation. The transformed
frequency domain acoustic data may be analyzed (e.g., a comparison
of transformed baseline data to transformed service data) at a
frequency ranging from greater than about 0 Hz to about 5,000 Hz,
alternatively from about 1,000 Hz to about 5,000 Hz, alternatively
from about 1,000 Hz to about 4,000 Hz, alternatively from about
2,000 Hz to about 4,000 Hz, alternatively from about 2,500 Hz to
about 3,500 Hz, alternatively from about 2,000 Hz to about 3,000
Hz, alternatively from about 1,750 Hz to about 2,250 Hz,
alternatively about 2000 Hz, alternatively about 3,000 Hz, or
combinations thereof. If spikes in the transformed service data are
detected above the transformed baseline data at the above frequency
ranges, then the pump is operating abnormally, for example
cavitating.
[0043] When analyzing data in the frequency domain, data magnitude
is an indicator of abnormal pump operation (e.g., cavitation). FIG.
5 demonstrates that acoustic sensors (e.g., knock sensors) are
capable of detecting cavitation in a pump. A positive displacement
pump was operated under normal, non-cavitating operating
conditions, as shown by the lower line plotted in FIG. 5. Over a
period of time, fluid flow to the suction end of a positive
displacement pump was gradually decreased in 25% increments until
cavitation resulted. As shown by the upper line plotted in FIG. 5,
cavitation resulted in a first dramatic spike in data magnitude at
from about 1500 to 2500 Hz, or 1750 to 2250 Hz, or about 2000 Hz
and a second dramatic spike at from about 3500 to 5000 Hz, or 4000
to 5000 Hz, or 4500 to 5000 Hz. In an embodiment, the presence of
at least two spikes in data magnitude at two different frequencies
or frequency ranges may indicate abnormal pump operation (e.g.,
cavitation), which is explained in more detail in the Examples.
Again, comparison of plots such as shown in FIG. 5 may use a data
average thereof such as root mean square (RMS as indicated on the
y-axis) or other curve fit or data normalization technique. The
results show that the acoustic sensor is capable of detecting
cavitation in a positive displacement pump as indicated by an
increase in data magnitude (e.g., increase in dB or g's in service
data over baseline data). In some embodiments, the magnitude of
increases in data magnitude in the frequency domain may fall within
the indication ranges for dBs, g's, and percentage increases set
forth previously for data in the time domain. Upon detection of an
magnitude indication of a pump abnormality (e.g., cavitation), the
monitoring system 121 may signal a user (e.g., sound an alarm
and/or send an alarm signal to control unit 120) that abnormal pump
operation (e.g., cavitation) has been detected and one or more pump
system parameters may be altered to implement corrective
action.
[0044] When analyzing data in the frequency domain, data magnitude
as represented by a power spectrum analysis may serve as an
indicator of abnormal pump operation (e.g., cavitation). For
example, the area under the power spectrum curve for the baseline
data (e.g., normal operation) can be compared to the area under the
power spectrum curve for the service data, and an increase in power
spectrum may indicate abnormal pump operation such as cavitation.
In embodiments, the power spectrum for transformed baseline and
service data are compared at a frequency ranging from greater than
about 0 Hz to about 5,000 Hz, alternatively from about 1,000 Hz to
about 5,000 Hz, alternatively from about 1,000 Hz to about 4,000
Hz, alternatively from about 2,000 Hz to about 4,000 Hz,
alternatively from about 2,500 Hz to about 3,500 Hz, alternatively
from about 2,000 Hz to about 3,000 Hz, alternatively from about
1,750 Hz to about 2,250 Hz, alternatively about 2000 Hz,
alternatively about 3,000 Hz, or combinations thereof. FIGS. 6A-C
shows the results of frequency analysis performed of acoustic
energy detected from a cavitating pump using power spectrum area
analysis. In FIG. 6A, acoustic energy was measured over a frequency
range of 0 to 12,000 Hz over the test period. The three-dimensional
waterfall plot in FIG. 6A shows the large increase in acoustic
energy during cavitation at a frequency range of about 2,000 Hz to
about 6,000 Hz. FIG. 6B shows a two-dimensional plot at a
particular point in time during cavitation, as shown by
cross-section line B-B of FIG. 6A. FIG. 6C is another
two-dimensional plot at a particular frequency (e.g., about 4000
Hz) during cavitation, as shown by cross-section line CC of FIG.
6A. FIG. 6C shows a large spike of acoustic energy over baseline
(as measured by the ratio of area under the power spectrum curve
for service data to baseline data) during the time between the
suction valve closing and the discharge valve opening, which is
indicative of pump cavitation and corrective action may be
initiated. In another embodiment, if the ratio of service data
magnitude to baseline data magnitude as represented by area under
the power curve (e.g., integrated area under the power curve for a
given frequency range) is equal to or greater than about 2, 3, 4,
5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, then the monitoring
system 121 may signal a user (e.g., sound an alarm and/or send an
alarm signal to control unit 120) that abnormal pump operation
(e.g., cavitation) has been detected and one or more pump system
parameters may be altered to implement corrective action.
[0045] In another embodiment, valve damage in pump (e.g., a
positive displacement pump) may be detected by using acoustic data
sensed by the acoustic sensor 102. In a pump with a damaged valve,
without being bound by theory, the measured acoustic energy at high
frequencies (e.g., magnitude of the service data) should be
significantly larger than acoustic energy in a normal pump without
a damaged valve (e.g., magnitude of the baseline data).
Accordingly, the magnitude of the acoustic energy from the service
and baseline data may be compared in the time domain (e.g., FIG.
7A), the frequency domain (e.g., FIG. 7B), or both. If the
magnitude of the acoustic energy at certain time and/or frequency
is higher than a predetermined range or threshold, the valve may be
damaged, and an alarm may be sounded and/or a signal may be sent to
change one or more pump system parameters in order to reduce
cavitation. FIG. 7A is a time domain plot comparing the acoustic
energy in g's (top line) of a pump with a damaged suction valve
(e.g., service data) and the acoustic energy in g's (bottom line)
of a pump with a normal suction valve (e.g., baseline data). The
magnitude of acoustic energy measured in a pump with a damaged
valve (or an average thereof such as root mean square or other
curve fit) is noticeably larger than the magnitude of acoustic
energy in a normal pump, as represented by the delta in energy
between the lines (e.g., difference in energy such as dB or g's).
Without being limited by theory, this is likely due to noise or
"hiss" associated with fluid escaping through a leaky valve.
Referring to FIG. 7C, such "hiss" is also demonstrated in the time
domain for a single pump stroke for a pump having a damaged suction
valve (e.g., service data) in comparison to a pump with a normal
suction valve (e.g., baseline data). Such "hiss" may be associated
with pressure placed upon the damaged suction valve when closed
during the discharge stroke of the pump, with fluid escaping
through the damaged portion. In embodiments, "hiss" associated with
valve leakage may be indicated by data magnitude (e.g., increase in
service data energy over baseline energy in dB or g's) during the
discharge and/or suction stroke of the pump, as associated with
suction and/or discharge valve damage, respectively. In an
embodiment, if the service data magnitude (or an average thereof
such as root mean square or other curve fit) is from about 2, 3, 4,
5, 6, 7, 8, 9, or 10 g's greater than the baseline data magnitude
(or an average thereof such as root mean square or other curve
fit), then the monitoring system 121 may signal a user (e.g., sound
an alarm and/or send an alarm signal to control unit 120) that
abnormal pump operation (e.g., valve leakage) has been detected and
one or more pump system parameters may be altered to implement
corrective action. In another embodiment, if the service decibel
level (or an average thereof such as root mean square or other
curve fit) is from about 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25 or 30
dB greater than the baseline decibel level or an average thereof
such as root mean square or other curve fit), then the monitoring
system 121 may signal a user (e.g., sound an alarm and/or send an
alarm signal to control unit 120) that abnormal pump operation
(e.g., valve leakage) has been detected and one or more pump system
parameters may be altered to implement corrective action. In
another embodiment, if the service data magnitude (or an average
thereof such as root mean square or other curve fit) is from about
50, 100, 150, 200, 250, 300, 350, 400, 450, or 500% greater than
the baseline data magnitude (or an average thereof such as root
mean square or other curve fit), then the monitoring system 121 may
signal a user (e.g., sound an alarm and/or send an alarm signal to
control unit 120) that abnormal pump operation (e.g., valve
leakage) has been detected and one or more pump system parameters
may be altered to implement corrective action. Additional
disclosure regarding detection of cavitation and/or valve leakage
is shown in the Examples.
[0046] FIG. 7B is a frequency domain plot showing the frequency
range of acoustic data collected from a pump with a damaged valve
in comparison to a non-damaged valve. There is a significant
increase (from about 6.times. to about 10.times.) in energy as
measured in g's between baseline data and service data at a
frequency of from about 4,500 to 5,000 Hz. Likewise, differences
between service and baseline data at about 1,500 Hz and 3,500 Hz in
FIG. 7B, or in the range of from about 1,750 to about 2,250 Hz as
shown in the Examples, may also indicate valve damage. These
results show that using an acoustic sensor to detect acoustic
energy at certain frequencies is a feasible way of detecting valve
damage in a pump.
[0047] When abnormalities in pump operation (e.g., cavitation) have
been detected by the various techniques described above, control
system 121 may sound an alarm and/or adjust one or more pump
parameters or other operating conditions to reduce or eliminate
cavitations. Examples of pump parameters that may be adjusted
include without limitation, pump speed, pump pressure, boot
pressure, pump temperature, pump flow rate, or combinations
thereof. In an embodiment, properties of the fluid being pumped may
be adjusted, for example density. The pump parameters and/or
operating conditions (collectively, pump system parameters) may be
adjusted automatically by the control system, or they may be
adjusted manually by a user. Likewise, corrective action may be
taken upon detecting valve problems such as valve leakage, valve
bounce, etc. by servicing the pump to replace or repair faulty
valve components (seats, stems, seals, springs, etc.).
[0048] In some embodiments, the pump system and methods disclosed
herein are employed in a wellbore servicing operation. The pump
system may be transported to a well site, for example transported
on a skid or trailer to an onshore well site or transported via
barge or ship to an offshore well site. A wellbore servicing fluid
may be transported to and/or prepared at the well site. In an
embodiment, the wellbore service comprising preparing and placing
downhole one or more wellbore servicing fluids including, but are
not limited to, cement slurries, lost circulation pills, settable
fluids, plugging compositions for plug-and-abandon purposes, gravel
packing fluids, chemical packers, temporary plugs, spacer fluids,
completion fluids, remedial fluids, fracturing fluids, or
combinations thereof. In an embodiment, the wellbore service is a
drilling operation and the servicing fluid is a drilling fluid. In
an embodiment, the wellbore service is a cementing operation and
the servicing fluid is a cementitious fluid (e.g., a cement slurry
for primary and/or secondary cementing operations). In an
embodiment, the wellbore service is a enhanced recovery operation
(e.g., primary and/or secondary fracturing, acidizing, flooding,
etc.) and the servicing fluid is a fracturing fluid (e.g., proppant
slurry), acid fluid, sweeping/flooding fluid (e.g., water/steam),
etc. In an embodiment, the wellbore service is a gravel packing
service and the servicing fluid is a gravel pack fluid. The
wellbore servicing fluid may be pumped into the wellbore during the
service using a pump system as described herein (e.g., positive
displacement pump), and the operation of the pump may be monitored
as described herein to detect cavitation, valve bounce, and/or
valve damage therein. In various embodiments, the wellbore
servicing fluid is pumped with a positive displacement pump
operating at from about 100 to about 500 rpm, alternatively from
about 150 to about 450 rpm, alternatively from about 150 to about
400 rpm, alternatively from about 150 to about 350 rpm,
alternatively from about 150 to about 300 rpm, alternatively from
about 200 to about 350 rpm, alternatively from about 250 to about
350 rpm.
[0049] In an embodiment, the system 100 is employed in a wellbore
servicing operation, wherein pump 146 is a positive displacement
pump pumping a wellbore servicing fluid (e.g., cement slurry,
fracturing fluid, drilling fluid, etc.) down a wellbore, and
wherein the wellbore servicing operation is controlled by the
control unit 120, for example an ACE or ARC Control Unit available
from Halliburton Energy Services. The control unit 120 may and
generate and deliver control signals to pump 146. For example,
control unit 120 may receive automated and/or manual instructions
from a user input and/or may send signals to pump 146 based on
internal calculations, programming, and/or data received from
monitoring system 121 and/or acoustic sensor 102. The control
system 120 is capable of affecting and controlling substantially
all process control variables and functions of the pump system
100.
EXAMPLES
[0050] In the following examples, a three plunger positive
displacement pump of the type shown in FIG. 2 was used to pump
non-potable water. The acoustic sensor used to gather data was
mounted on the suction header adjacent the fluid end. Sensor data
was gathered and analyzed with e-Z Analyst v5.1.35 vibration and
acoustic analysis software from IOtech to provide the plots set
forth in FIGS. 8-15 discussed below. The pump was connected to an
engine and transmission having a plurality of gears (e.g.,
1.sup.st-7.sup.th), allowing the pump to operate at various RPMs
and flow rates (barrels per min) as set forth in the following
Table 1:
TABLE-US-00001 Flow Rate Min. Flow Rate Max. Gear RPM Min. RPM Max.
(BPM) (BPM) 1 57 90.8 2.24 3.57 2 79.4 126.4 3.12 4.97 3 97.1 154.8
3.82 6.09 4 121 192.8 4.76 7.58 5 135.3 215.4 5.32 8.48 6 168.5
268.5 6.63 10.56 7 213.9 340.6 8.41 13.40
Example 1
Cavitation
[0051] While operating the pump in gears 3-6 as set forth in Table
1, data was collected from the knock sensor and plotted in FIGS.
8-11, respectively. The strip charts (i.e., the lower plots so
labeled) in FIGS. 8-11 represent a plot of RMS g's over a test
period of time for operation in gears 3-6, respectively. Within the
test period for a given gear, power spectrum analysis (as
represented by the upper plots so labeled in FIGS. 8-11) was
performed via FFT at various time intervals and plotted as RMS g's
as a function of frequency from 0 to 5000 Hz. During the test
period, pump speed was increased for each gear and cavitation was
induced in the pump by restricting fluid flow to the pump by
partially closing a valve in the suction side flow line to the
pump.
[0052] Referring to FIG. 8, the pump was operated for a test period
of about 150 seconds in gear 3. From about 0 to about 47 seconds of
the test period, the pump was operating in gear 3 at lower rpms
(e.g., about 100 rpm) and with no cavitation, and the strip chart
of FIG. 8 shows low g's of about 0.5 during this period. The upper
plot of FIG. 8A represents a power spectrum analysis taken at about
8 seconds (as indicated by the vertical line at 8 seconds in the
lower plot of FIG. 8A) into the test period and shows two groups of
peaks, labeled first indicator and second indicator. The first
indicator shows a maximum peak at about 0.04 g's and the second
indicator shows a maximum peak at about 0.02 g's.
[0053] From about 47 to about 88 seconds of the test period, the
pump was operating in gear 3 at higher rpms (e.g., about 150 rpm)
and higher overall energy but no cavitation, and the strip chart of
FIG. 8 shows slightly higher g's of from about 0.5 to about 1
during this period. The upper plot of FIG. 8B represents a power
spectrum analysis taken at about 58 seconds into the test period
and shows two groups of peaks, labeled first indicator and second
indicator. The first indicator shows a maximum peak at about 0.08
g's and the second indicator shows a maximum peak at about 0.04
g's.
[0054] From about 88 seconds to about 113 seconds, the pump was
operating in gear 3 at higher rpms (e.g., about 150 rpm) and with
cavitation induced by closing a suction side valve to a 3/4 setting
(i.e., 3/4 way open). The strip chart of FIG. 8 shows much higher
g's of from about 2 to about 3 during this period. The upper plot
of FIG. 8C represents a power spectrum analysis taken at about 100
seconds into the test period and again shows two groups of peaks,
labeled first indicator and second indicator. The first indicator
shows a maximum peak at from about 0.2 to 0.25 g's and the second
indicator shows a maximum peak at from about 0.1 to about 0.15 g's,
and these values in FIG. 8C are much greater (e.g., at least about
1.5, 1.75, 2.0, 2.25, or 2.5 times greater than) when the pump is
cavitating than the corresponding values from FIGS. 8A and 8B taken
in the absence of cavitation. Likewise, as shown in the strip chart
of FIG. 8, pump cavitation is clearly identified by a sharp
increase in g's during the time period of from about 90 seconds to
about 113 seconds while the suction side valve is partially closed.
While the pump is cavitating, the overall g readings of from about
2 to 3 may (or may not) be considered acceptable for the pump
operating at these conditions (e.g., gear, rpm, flow rate, given
fluid, etc.), and thus appropriate cavitation alarm thresholds may
not (or may) be employed for these operating conditions.
[0055] The process described above for operation of the pump in
gear 3 was repeated for gears 4, 5, and 6 as shown in FIGS. 9, 10,
and 11, respectively. Referring to FIG. 9, the pump was operated
for a test period of about 72 seconds in gear 4. From about 0 to
about 18 seconds of the test period, the pump was operating in gear
4 at about 192 rpm and with no cavitation, and the strip chart of
FIG. 9 shows low g's of about 0.5 during this period. The upper
plot of FIG. 9A represents a power spectrum analysis taken at about
6.5 seconds into the test period and shows two groups of peaks,
labeled first indicator and second indicator. The first indicator
shows a maximum peak at about 0.07 g's and the second indicator
shows a maximum peak at about 0.04 g's.
[0056] From about 18 seconds to about 43 seconds, the pump was
operating in gear 4 at about 192 rpm and with cavitation induced by
closing a suction side valve to a 3/4 setting (i.e., 3/4 way open).
The strip chart of FIG. 9 shows much higher g's of from about 3.75
to about 4.25 during this period. The upper plot of FIG. 9B
represents a power spectrum analysis taken at about 25 seconds into
the test period and again shows two groups of peaks, labeled first
indicator and second indicator. The first indicator shows a maximum
peak at from about 0.3 to 0.4 g's (e.g., greater than 0.3 g's,
alternatively greater than 0.35 g's) and the second indicator shows
a maximum peak at from about 0.15 to about 0.25 g's (e.g., greater
than 0.15 g's, alternatively greater than 0.2 g's), and these
values in FIG. 9B are much greater when the pump is cavitating than
the corresponding values from FIG. 9A taken in the absence of
cavitation. Likewise, as shown in the strip chart of FIG. 9, pump
cavitation is clearly identified by a sharp increase in g's from
about 18 seconds to about 43 seconds while the suction side valve
is partially closed. While the pump is cavitating, the overall g
readings of about 4 are more likely to be considered problematic
(e.g., in comparison to the g reading of from about 2 to 3 for gear
3 and FIG. 8) for the pump operating at these conditions (e.g.,
gear, rpm, flow rate, given fluid, etc.), and thus appropriate
cavitation alarm thresholds may be employed for these operating
conditions. Alarm thresholds may be associated with the first and
second indicators (as well as any other indicator described
herein), and may be set in accordance with the peak magnitudes or
data values associated with the indicators. For example, as shown
in FIG. 9B, a first alarm threshold, second alarm threshold, third
alarm threshold, or combinations thereof may be employed. For
example, a first alarm threshold of about 0.3 g's may be set for
the first indicator, a second alarm threshold of about 0.2 g's may
be set for the second indicator, a third alarm threshold of about 4
g's may be set for the time domain data represented on the strip
chart, or combinations thereof.
[0057] Referring to FIG. 10, the pump was operated for a test
period of about 88 seconds in gear 5. From about 0 to about 39
seconds of the test period, the pump was operating in gear 5 at
about 215 rpm and with no cavitation, and the strip chart of FIG.
10 shows low g's of about 0.75 during this period. The upper plot
of FIG. 10A represents a power spectrum analysis taken at about 18
seconds into the test period and shows two groups of peaks, labeled
first indicator and second indicator. The first indicator shows a
maximum peak at about 0.08-0.09 g's and the second indicator shows
a maximum peak at about 0.03-0.04 g's.
[0058] From about 39 seconds to about 55 seconds, the pump was
operating in gear 5 at about 215 rpm and with cavitation induced by
closing a suction side valve to a 3/4 setting (i.e., 3/4 way open).
The strip chart of FIG. 10 shows much higher g's of from about 4 to
about 6 during this period. The upper plot of FIG. 10B represents a
power spectrum analysis taken at about 47 seconds into the test
period and again shows two groups of peaks, labeled first indicator
and second indicator. The first indicator shows a maximum peak at
from about 0.35 to 0.4 g's (e.g., greater than 0.3 g's,
alternatively greater than 0.35 g's) and the second indicator shows
a maximum peak at from about 0.2 to about 0.3 g's (e.g., greater
than 0.2 g's, alternatively greater than 0.25 g's), and these
values in FIG. 10B are much greater when the pump is cavitating
than the corresponding values from FIG. 10A taken in the absence of
cavitation. Likewise, as shown in the strip chart of FIG. 10, pump
cavitation is clearly identified by a sharp increase in g's from
about 39 seconds to about 55 seconds while the suction side valve
is partially closed. While the pump is cavitating, the overall g
readings of from about 4 to about 6 (alternatively, about 5) are
more likely to be considered problematic (e.g., in comparison to
the g reading of from about 2 to 3 for gear 3 and FIG. 8) for the
pump operating at these conditions (e.g., gear, rpm, flow rate,
given fluid, etc.), and thus appropriate cavitation alarm
thresholds may be employed for these operating conditions. For
example, as shown in FIG. 10B, a first alarm threshold, second
alarm threshold, third alarm threshold, or combinations thereof may
be employed. For example, a first alarm threshold of about 0.3 g's
may be set for the first indicator, a second alarm threshold of
about 0.2 g's may be set for the second indicator, a third alarm
threshold of about 4 g's (alternatively, 5 g's) may be set for the
time domain data represented on the strip chart, or combinations
thereof.
[0059] Referring to FIG. 11, the pump was operated for a test
period of about 88 seconds in gear 6. From about 0 to about 37
seconds of the test period, the pump was operating in gear 6 at
about 268 rpm and with no cavitation, and the strip chart of FIG.
11 shows low g's of about 1 during this period. The upper plot of
FIG. 11A represents a power spectrum analysis taken at about 13.5
seconds into the test period and shows two groups of peaks, labeled
first indicator and second indicator. The first indicator shows a
maximum peak at about 0.1 g's and the second indicator shows a
maximum peak at about 0.04-0.05 g's.
[0060] From about 37 seconds to about 42 seconds, the pump was
operating in gear 6 at about 268 rpm and with cavitation induced by
closing a suction side valve to a 3/4 setting (i.e., 3/4 way open).
The strip chart of FIG. 11 shows much higher g's of from about 7 to
about 8 during this period. The upper plot of FIG. 11B represents a
power spectrum analysis taken at about 38 seconds into the test
period and again shows two groups of peaks, labeled first indicator
and second indicator. The first indicator shows a maximum peak at
from about 0.4 to 0.5 g's (e.g., greater than 0.3. 0.35, 0.4, 0.45,
or 5 g's) and the second indicator shows a maximum peak at from
about 0.2 to about 0.3 g's (e.g., greater than 0.2, 0.225, 0.25, or
0.275 g's), and these values in FIG. 11B are much greater when the
pump is cavitating than the corresponding values from FIG. 11A
taken in the absence of cavitation. Likewise, as shown in the strip
chart of FIG. 11, pump cavitation is clearly identified by a sharp
increase in g's from about 37 seconds to about 42 seconds while the
suction side valve is partially closed. While the pump is
cavitating, the overall g readings of from about 7 to about 8
demonstrate severe cavitation and unacceptably high levels of
vibrational energy (as demonstrated by the very brief cavitation
testing time of about 5 seconds) for the pump operating at these
conditions (e.g., gear, rpm, flow rate, given fluid, etc.), and
thus appropriate cavitation alarm thresholds may be employed for
these operating conditions. For example, as shown in FIG. 11B, a
first alarm threshold, second alarm threshold, third alarm
threshold, or combinations thereof may be employed. For example, a
first alarm threshold of about 0.3, 0.4, or 0.5 g's may be set for
the first indicator, a second alarm threshold of about 0.2, 0.225,
0.25, 0.275, or 0.3 g's may be set for the second indicator, a
third alarm threshold of about 4, 5, 6, or 7 g's may be set for the
time domain data represented on the strip chart, or combinations
thereof.
[0061] As shown in FIGS. 8-11, the second indicator as measured in
g's is typically smaller than the first indicator. In some
embodiments, the second indicator as measured in g's is from about
1/2 to about 2/3 the first indicator, alternatively about 1/2 the
first indicator, alternatively about 2/3 the first indicator. The
position (e.g., frequency ranges) of the first and second
indicators as measured in Hz may shift slightly in frequency with
changes in gearing, but the indicators remain clearly present. In
some embodiments, the frequency range of the first indicator may be
from about 2,000 to about 3,000 Hz, alternatively from about 2,250
to about 3,000 Hz, alternatively from about 2,500 to about 3,000
Hz, alternatively from about 2,250 to about 2,750 Hz, alternatively
from about 2,500 to about 2,750 Hz, alternatively about 2,750 Hz.
In some embodiments, the frequency range of the second indicator
may be from about 3,500 to about 4,500 Hz, alternatively from about
3,500 to about 4,250 Hz, alternatively from about 3,500 to about
4,000 Hz, alternatively from about 3,750 to about 4,250 Hz,
alternatively from about 3,750 to about 4,000 Hz, alternatively
about 4,000 Hz. Where multiple peaks are present within a given
frequency range for a given indicator, reference is typically made
to the highest peak within the given frequency range. The frequency
ranges of the first and/or second indicators may be further
correlated with the various values for the first and/or second
alarm thresholds (e.g., a first indicator having a designated
frequency range and a corresponding first alarm threshold having a
designated value). Furthermore, the first and/or second indicators;
the first, second, and/or third alarm thresholds; or combinations
thereof may be further correlated to a given operating gear and/or
rpm range for the pump (e.g., a first indicator having a designated
frequency range and a corresponding first alarm threshold having a
designated value and further corresponding to a pump operating in a
designated gear, rpm range, or flow rate such as those shown in
Table 1). As demonstrated, the indicators of cavitation may show a
multi-fold increase (e.g., equal to or greater than about 1.times.,
1.25.times., 1.5.times., 1.75.times., 2.times., 2.25.times.,
2.5.times., 2.75.times., 3.times., 3.25.times., 3.5.times., 3.75,
or 4.times.) increase as compared to a corresponding indicator of
non-cavitation. Example 1 clearly demonstrates that pump cavitation
can be identified from a number of acoustical energy indicators or
data provided by an acoustical sensor, and that one or more alarms
may be associated with one or more threshold values for such
indicators and/or data.
Example 2
Leaky Suction Valve
[0062] Valve leakage was reproduced by placing a known leaky
suction valve in one of the chambers of the three chamber pump.
While operating the pump in gears 3-6 as set forth in Table 1, data
was collected from the knock sensor and plotted in FIGS. 12-15,
respectively. The strip charts in FIGS. 12-15 represent a plot of
RMS g's over a test period of time for operation in gears 3-6,
respectively. Within the test period for a given gear, power
spectrum analysis (as represented by the upper plots so labeled in
FIGS. 12-15) was performed via FFT at various time intervals and
plotted as RMS g's as a function of frequency from 0 to 5000
Hz.
[0063] Referring to FIG. 12, the pump was operated for a test
period of about 60 seconds in gear 3 at about 150 rpm. The strip
chart of FIG. 12 shows g's ranging from about 3 to about 5
(alternatively, from about 3.5 to about 4.5 g's, alternatively
equal to or greater than about 4 g's) during this period, which may
be associated with the "hiss" of fluid passing through the leaky
suction valve. The upper plot of FIG. 12 shows a power spectrum
analysis taken at about 7 seconds into the test period and shows
two groups of peaks, labeled fourth indicator and fifth indicator.
The fourth indicator shows a maximum peak at about 0.03 to about
0.35 g's (alternatively, equal to or greater than 0.25, 0.275, or
0.3 g's) and the fifth indicator shows a maximum peak at about 0.03
to about 0.35 g's (alternatively, equal to or greater than 0.25,
0.275, or 0.3 g's). FIG. 12 also shows a sixth indicator having a
maximum peak at about 0.225 to about 0.275 g's (alternatively,
equal to or greater than 0.20, 0.225, or 0.25 g's). Alarm
thresholds may be associated with the fourth, fifth, and/or sixth
indicators, and may be set in accordance with the peak magnitudes
associated with the indicators. In this instance, the fourth and
fifth indicators are about equal to each other in magnitude, and
thus the fourth and fifth alarm thresholds may likewise be about
equal to each other (e.g., equal to or greater than 0.25, 0.275, or
0.3 g's). Also in this instance, the sixth indicator/alarm
threshold may be less than the fourth and fifth. Alternatively, the
fourth, fifth, and sixth alarm thresholds may be about equal (e.g.,
equal to or greater than about 0.25 g's).
[0064] Referring to FIG. 13, the pump was operated for a test
period of about 62 seconds in gear 4 at about 190 rpm. The strip
chart of FIG. 13 shows g's ranging from about 3.5 to about 4.5
(alternatively, from about 3.5 to about 4 g's, alternatively equal
to or greater than about 4 g's) during this period, which may be
associated with the "hiss" of fluid passing through the leaky
suction valve. The upper plot of FIG. 13 shows a power spectrum
analysis taken at about 31 seconds into the test period and shows
two groups of peaks, labeled fourth indicator and fifth indicator.
The fourth indicator shows a maximum peak at about 0.03 to about
0.35 g's (alternatively, equal to or greater than 0.25, 0.275, or
0.3 g's) and the fifth indicator shows a maximum peak at about 0.03
to about 0.35 g's (alternatively, equal to or greater than 0.25,
0.275, 0.3, or 0.325 g's). FIG. 13 also shows a sixth indicator
having a maximum peak at about 0.3 to about 0.4 g's (alternatively,
from about 0.3 to about 0.4, alternatively equal to or greater than
0.25, 0.275, 0.3, 0.325, 0.35, or 0.375 g's). Alarm thresholds may
be associated with the fourth, fifth, and/or sixth indicators, and
may be set in accordance with the peak magnitudes associated with
the indicators. In this instance, the fourth, fifth and/or sixth
indicators are about equal to each other in magnitude, and thus the
fourth, fifth, and/or sixth alarm thresholds may likewise be about
equal to each other (e.g., equal to or greater than 0.25, 0.275, or
0.3 g's).
[0065] Referring to FIG. 14, the pump was operated for a test
period of about 64 seconds in gear 5 at about 215 rpm. The strip
chart of FIG. 14 shows g's ranging from about 3.5 to about 4.5
(alternatively, from about 3.5 to about 4 g's, alternatively, from
about 4 to about 4.5 g's, alternatively equal to or greater than
about 4 g's) during this period, which may be associated with the
"hiss" of fluid passing through the leaky suction valve. The upper
plot of FIG. 14 shows a power spectrum analysis taken at about 7
seconds into the test period and shows two groups of peaks, labeled
fourth indicator and fifth indicator. The fourth indicator shows a
maximum peak at about 0.04 to about 0.55 g's (alternatively, equal
to or greater than 0.4, 0.45, 0.5, or 0.55 g's) and the fifth
indicator shows a maximum peak at about 0.03 to about 0.4 g's
(alternatively, equal to or greater than 0.25, 0.3, 0.35, or 0.4
g's). FIG. 14 also shows a sixth indicator having a maximum peak at
about 0.2 to about 0.25 g's (alternatively equal to or greater than
0.2, 0.225, or 0.25 g's). Alarm thresholds may be associated with
the fourth, fifth, and/or sixth indicators, and may be set in
accordance with the peak magnitudes associated with the indicators.
In this instance, the fourth and fifth alarm thresholds may be
about equal to each other (e.g., equal to or greater than 0.3 or
0.35 g's). Also in this instance, the sixth indicator/alarm
threshold is less than the fourth and fifth. Alternatively, the
fourth threshold (e.g., 0.4, 0.45, or 0.5 g's) is greater than the
fifth threshold (e.g., 0.3 or 0.35 g's), which is greater than the
sixth threshold (e.g., 0.2 g's). Alternatively, the fourth, fifth,
and sixth alarm thresholds may be about equal (e.g., equal to or
greater than about 0.2 g's).
[0066] Referring to FIG. 15, the pump was operated for a test
period of about 62 seconds in gear 6 at about 268 rpm. The strip
chart of FIG. 15 shows g's ranging from about 3.5 to about 4.5
(alternatively, from about 3.5 to about 4 g's, alternatively, from
about 4 to about 4.5 g's, alternatively equal to or greater than
about 4 g's) during this period, which may be associated with the
"hiss" of fluid passing through the leaky suction valve. The upper
plot of FIG. 15 shows a power spectrum analysis taken at about 41
seconds into the test period and shows two groups of peaks, labeled
fourth indicator and fifth indicator. The fourth indicator shows a
maximum peak at about 0.25 to about 0.35 g's (alternatively, equal
to or greater than 0.2, 0.25, 0.3, or 0.35 g's) and the fifth
indicator shows a maximum peak at about 0.45 to about 0.55 g's
(alternatively, equal to or greater than 0.3, 0.35, 0.4, 0.45, or
0.5 g's). FIG. 15 also shows a sixth indicator having a maximum
peak at about 0.25 to about 0.3 g's (alternatively equal to or
greater than 0.2, 0.25, 0.275, or 0.3 g's). Alarm thresholds may be
associated with the fourth, fifth, and/or sixth indicators, and may
be set in accordance with the peak magnitudes associated with the
indicators. In this instance, the fourth and sixth alarm thresholds
may be about equal to each other (e.g., equal to or greater than
0.25 or 0.3 g's). Also in this instance, the fifth indicator/alarm
threshold is greater than the fourth and sixth. Alternatively, the
fourth, fifth, and sixth alarm thresholds may be about equal (e.g.,
equal to or greater than about 0.3 g's).
[0067] The strip chart in each of FIGS. 12-15 shows g's ranging
from about 3.5 to about 4.5, and thus a seventh alarm threshold may
be set for this data stream, for example equal to or greater than
about 3.5, 4, or 4.5 g's. The seventh alarm threshold may be used
alone or in combination with any of the other indicators/alarm
thresholds set forth herein to provide an indication of valve
leakage.
[0068] The position (e.g., frequency ranges) of the fourth, fifth,
and/or sixth indicators as measured in Hz may shift slightly in
frequency with changes in gearing, but the indicators remain
clearly present. In some embodiments, the frequency range of the
fourth indicator may be from about 2,500 to about 3,000 Hz,
alternatively from about 2,500 to about 2,750 Hz, alternatively
from about 2,600 to about 2,700 Hz. In some embodiments, the
frequency range of the fifth indicator may be from about 3,500 to
about 4,500 Hz, alternatively from about 3,750 to about 4,250 Hz,
alternatively from about 3,750 to about 4,000 Hz. In some
embodiments, the frequency range of the sixth indicator may be from
about 1,750 to about 2,250 Hz, alternatively from about 1,750 to
about 2,000 Hz, alternatively from about 1,500 to about 2,000 Hz.
Where multiple peaks are present within a given frequency range for
a given indicator, reference is typically made to the highest peak
within the given frequency range. The frequency ranges of the
fourth, fifth and/or sixth indicators may be further correlated
with the various values for the fourth, fifth and/or sixth alarm
thresholds (e.g., a fourth indicator having a designated frequency
range and a corresponding fourth alarm threshold having a
designated value). Furthermore, the fourth, fifth and/or sixth
indicators; the fourth, fifth, and/or sixth alarm thresholds; or
combinations thereof may be further correlated to a given operating
gear and/or rpm range for the pump (e.g., a fourth indicator having
a designated frequency range and a corresponding fourth alarm
threshold having a designated value and further corresponding to a
pump operating in a designated gear, rpm range, or flow rate such
as those shown in Table 1).
[0069] Comparisons can be made between the data collected and
plotted in FIGS. 8-11 for pump cavitation and data collected and
plotted in FIGS. 12-15 for leaky valves, and such comparisons
provide the ability to detect pump cavitation, valve leakage, or
both; distinguish pump cavitation from valve leakage; or
combinations thereof. That is, the various indicators and alarm
thresholds for cavitation as shown in FIGS. 8-11 may be used in a
variety of combinations with the various indicators and alarm
thresholds for valve leakage as shown in FIGS. 12-15. For example,
differences in the intensity of the indicators (e.g., maximum peak
g's of the first and second indicators of FIGS. 8-11 in comparison
to fourth and fifth indicators of FIGS. 12-15) may be used to
distinguish pump cavitation from valve leakage or vice-versa.
Likewise, differences in the frequency band of the indicators
(e.g., Hz band of the first and second indicators of FIGS. 8-11 in
comparison to fourth and fifth indicators of FIGS. 12-15) may be
used to distinguish pump cavitation from valve leakage or
vice-versa. Differences in the relative intensity (e.g., maximum
g's) and/or frequency band (e.g., Hz band) in the indicators (e.g.,
comparing the first indicator to the second indicator of FIGS. 8-11
in view of comparing the fourth indicator to the fifth indicator of
FIGS. 12-15) may also be used to distinguish cavitation from valve
leakage or vice-versa.
[0070] While embodiments of the invention have been shown and
described, modifications thereof can be made by one skilled in the
art without departing from the spirit and teachings of the
invention. The embodiments described herein are exemplary only, and
are not intended to be limiting. Many variations and modifications
of the invention disclosed herein are possible and are within the
scope of the invention. Where numerical ranges or limitations are
expressly stated, such express ranges or limitations should be
understood to include iterative ranges or limitations of like
magnitude falling within the expressly stated ranges or limitations
(e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater
than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a
numerical range with a lower limit, R.sub.L, and an upper limit,
R.sub.U, is disclosed, any number falling within the range is
specifically disclosed. In particular, the following numbers within
the range are specifically disclosed:
R=R.sub.L+k*(R.sub.U-R.sub.L), wherein k is a variable ranging from
1 percent to 100 percent with a 1 percent increment, i.e., k is 1
percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50
percent, 51 percent, 52 percent, . . . 95 percent, 96 percent, 97
percent, 98 percent, 99 percent, or 100 percent. Moreover, any
numerical range defined by two R numbers as defined in the above is
also specifically disclosed. Use of the term "optionally" with
respect to any element of a claim is intended to mean that the
subject element is required, or alternatively, is not required.
Both alternatives are intended to be within the scope of the claim.
Use of broader terms such as comprises, includes, having, etc.
should be understood to provide support for narrower terms such as
consisting of, consisting essentially of, comprised substantially
of, etc.
[0071] Accordingly, the scope of protection is not limited by the
description set out above but is only limited by the claims which
follow, that scope including all equivalents of the subject matter
of the claims. Each and every claim is incorporated into the
specification as an embodiment of the present invention. Thus, the
claims are a further description and are an addition to the
embodiments of the present invention. The discussion of a reference
in the Description of Related Art is not an admission that it is
prior art to the present invention, especially any reference that
may have a publication date after the priority date of this
application. The disclosures of all patents, patent applications,
and publications cited herein are hereby incorporated by reference,
to the extent that they provide exemplary, procedural or other
details supplementary to those set forth herein.
* * * * *