Field of the Disclosure
[0001] The disclosure is generally related to the field of monitoring systems for machinery,
and more particularly to an improved system and method for monitoring pump cavitation
and for controlling pump operation based on such monitoring.
Background of the Disclosure
[0002] The condition of rotating machinery is often determined using visual inspection techniques
performed by experienced operators. Failure modes such as cracking, leaking, corrosion,
etc. can often be detected by visual inspection before failure is likely. The use
of such manual condition monitoring allows maintenance to be scheduled, or other actions
to be taken, to avoid the consequences of failure before the failure occurs. Intervention
in the early stages of deterioration is usually much more cost effective than undertaking
repairs subsequent to failure. Patent publications
US 5 601 414 A showing a control logic for sensing abnormal pressure conditions by a pressure sensing
device and for modifying pump operation based thereon,
US 6 663 349 B1 showing a pump control system making use of a cavitation system of a cavitation detection
component,
US 2002/123856 A1 showing a cavitation monitoring system with a user alert functionality and
WO 2009/024769 A2 showing a system for improving efficiency of a pump by controlling operation of the
pump provide information useful for understanding the invention.
[0003] One downside to manual monitoring is that typically it is only performed periodically.
Thus, if an adverse condition arises between inspections, machinery failure can occur.
It would be desirable to automate the condition monitoring process to provide a simple
and easy-to-use system that provides constant monitoring of one or more machinery
conditions. Such a system has the potential to enhance operation, reduce downtime
and increase energy efficiency.
Summary of the Disclosure
[0004] A system is disclosed for monitoring and controlling a positive displacement pump
according to claim 1.
[0005] A method is disclosed for monitoring and controlling a positive displacement pump
according to claim 10.
Brief Description of the Drawings
[0006] By way of example, a specific embodiment of the disclosed device will now be described,
with reference to the accompanying drawings:
FIG. 1 is an isometric view of an exemplary pump including a plurality of condition monitoring
sensors mounted thereon;
FIG. 2 is a cross-section view of the pump of FIG. 1, taken along line 2-2 of FIG. 1, illustrating
the position of the plurality of sensors mounted in relation to the pump's power rotor
bore;
FIG. 3 is a schematic of the disclosed system;
FIG. 4 is a cross-section view of an exemplary positive displacement gear pump;
FIG. 5 is a schematic of the system of FIG. 3 expanded to include remote monitoring and control; and
FIG. 6 is an exemplary logic flow illustrating an exemplary method for using the disclosed
system.
Detailed Description
[0007] In positive displacement screw pumps, pressure is developed from the inlet or suction
port of the pump to the outlet or discharge port in stage-to-stage increments. Each
stage is defined as a moving-thread closure or isolated volume formed by the meshing
of pump rotors between the inlet and outlet ends of the pump. Pressure is developed
along the moving-thread closures as liquid progresses through the pump. The number
of closures is usually proportional to the desired level of outlet pressure delivered,
i.e., the greater the pressure, the greater the number of closures necessary. The closures
enable the pump to develop an internal pressure gradient of progressively increasing
pressure increments. Properly applied, a rotary axial-screw pump can be used to pump
a broad range of fluids, from high-viscosity liquids to relatively light fuels or
water/oil emulsions.
[0008] When entrained or dissolved gas exist in solution within the pump, the normal progression
of pressure gradient development can be disrupted, adversely affecting pump performance.
If large quantities of gas become entrained in the pumped liquid, the internal pumping
process may become unsteady and the internal pressure gradient can be lost. The pump
may also vibrate excessively, leading to noise and excessive wear.
[0009] This condition is synonymous with a phenomenon known as "cavitation." Cavitation
usually occurs when the pressure of a fluid drops below its vapor pressure, allowing
gas to escape from the fluid. When the pump exerts increasing pressure on a gaseous
liquid, unstable stage pressures result, leading to collapse of the gas bubbles in
the pump's delivery stage.
[0010] Traditional cavitation detection has been through the ascertaining of audible noise,
reduced flow rate, and/or increased pump vibration. As can be appreciated, by the
time these circumstances can be detected, significant changes in pump operations may
have occurred. As a result, it can be too late to protect the pump from internal damage.
For example, where the pump is unable to develop a normal pressure gradient from suction
to discharge, the total developed pressure may occur in or near the last closure.
This can upset normal hydrodynamic support of the idler rotors, which can lead to
metal-to-metal contact with consequential damage to the pump.
[0011] Knowledgeable application and conservative ratings are traditional protection against
these conditions. However, when pumping liquids with unpredictable characteristics
or uncontrolled gas content, as is often the case, frequent monitoring of pump operations
with attendant labor and other costs is required to maintain normal operation. Traditional
means of detecting cavitation and other operating instabilities have been found particularly
unsuitable where the pump is expected to provide long reliable service at a remote
unattended installation, and under extreme environmental conditions.
[0012] Referring now to the drawings,
FIGS. 1 and
2 an intelligent cavitation monitoring system 1 mounted to an exemplary pump 2, which
in this embodiment is a screw-pump. The system 1 includes a plurality of pressure
sensors mounted at appropriate locations throughout the pump 2. These sensors include
a suction pressure transducer 4, an interstage pressure transducer 6, and a discharge
pressure transducer 8. The suction and discharge pressure sensors 4, 8 are separated
by a distance "
L" while the suction and interstage pressure sensors 4, 6 are separated by a distance
"
Li". As will be described in more detail later, the suction pressure sensor 4 can provide
a signal representative of the suction pressure "
Ps" to the system 1, the interstage pressure sensor can provide a signal representative
of an interstage pressure "
Pi" to the system 1, and the discharge pressure sensor can provide a signal representative
of the discharge pressure "
Pd" to the system 1. The system 1, in turn, can employ these signals to determine whether
an undesirable cavitation condition exists in the pump 2.
[0013] FIG. 3 shows the system 1 including a controller 28 coupled to the pressure sensors 4, 6,
8 via a communications link 30. Thus, the sensors 4, 6, 8 may send signals to controller
28 representative of pressure conditions at multiple locations within the pump 2,
as previously noted. The controller 28 may have a processor 32 executing instructions
for determining, from the received signals, whether the one or more operating conditions
of the pump 2 are within normal or desired limits. A non-volatile memory 34 may be
associated with the processor 32 for storing program instructions and/or for storing
data received from the sensors. A display 36 may be coupled to the controller 28 for
providing local and/or remote display of information relating to the condition of
the pump 2. An input device 38, such as a keyboard, may be coupled to the controller
28 to allow a user to interact with the system 1.
[0014] The communications link 30 is illustrated as being a hard wired connection. It will
be appreciated, however, that the communications link 30 can be any of a variety of
wireless or hard-wired connections. For example, the communication link 30 can be
a Wi-Fi link, a Bluetooth link, PSTN (Public Switched Telephone Network), a cellular
network such as, for example, a GSM (Global System for Mobile Communications) network
for SMS and packet voice communication, General Packet Radio Service (GPRS) network
for packet data and voice communication, or a wired data network such as, for example,
Ethernet/Internet for TCP/IP, VOIP communication, etc.
[0015] Communications to and from the controller can be via an integrated server that enables
remote access to the controller 28 via the Internet. In addition, data and/or alarms
can be transferred thru one or more of e-mail, Internet, Ethernet, RS-232/422/485,
CANopen, DeviceNet, Profitbus, RF radio, Telephone land line, cellular network and
satellite networks.
[0016] As previously noted, the sensors coupled to the pump 2 can be used to measure a wide
variety of operational characteristics of the pump. These sensors can output signals
to the controller 28 representative of those characteristics, and the controller 28
can process the signals and present outputs to a user. In addition, or alternatively,
the output information can be stored locally and/or remotely. This information can
be used to track and analyze operational characteristics of the pump over time.
[0017] For example, the suction, interstage, and discharge pressure sensors 4, 6, 8 may
provide signals to the controller 28 that the controller can use to determine if an
undesirable cavitation condition exists at one or more locations within the pump 2.
Under normal operation, if a positive displacement pump does not experience cavitation,
or does not have excess gas bubbles passing there through, the discharge pressure
Pd, interstage pressure
Pi and suction pressure
Ps will indicate a certain desired pressure gradient at any given time. If, however,
the pump experiences undesired cavitation, the desired pressure gradient will not
be able to be maintained. In particular, the interstage pressure
Pi may decrease. In addition, if excess gas bubbles pass through the pump, the interstage
pressure
Pi will not only decrease, it will also fluctuate.
[0018] If the location of the interstage pressure sensor 6 is located at
Li distance from the location of the suction pressure sensor 4 (
see FIG. 2), and the distance between the suction pressure sensor 4 and the discharge pressure
sensor 8 is
L, then under normal operation conditions the following relationship exists:

where, as previously noted,
Pi is the interstage pressure;
Ps is the suction pressure;
Pd is the discharge pressure, and
R is a ratio that indicates a severity level of cavitation in the pump 2.
[0019] While
FIG. 2 shows the relative locations of the sensors 4, 6, 8 in relation to an exemplary positive
displacement screw pump 2,
FIG. 4 shows where suction, interstage and discharge pressure sensors 4, 6, 8 may be positioned
in an exemplary positive displacement gear pump 2A. In the gear pump 2A embodiment,
the interstage pressure sensor 6 may again be located at
Li distance from the location of the suction pressure sensor 4, while the distance between
the suction pressure sensor 4 and the discharge pressure sensor 8 may be
L. The previously described ratio
R again applies as a ratio indicating a severity level of cavitation in the pump 2A.
Similar arrangements in other positive displacement pumps can be used such as progressive
cavity pumps, (i.e., rotary vane pumps, internal gear pumps, external gear pumps,
vane, geared screw pumps).
[0020] Once the locations of the pressure measuring components are determined, a target
cavitation severity level
RT is also determined, using the following relationship:

[0021] It will be appreciated that if the interstage pressure sensor 6 is positioned half
way between the suction pressure sensor 4 and the discharge pressure sensor 8, then
RT will be 0.5 or 50%. In such a case, when the system is in operation, an actual cavitation
severity level
Ra can be determined by:

[0022] If the suction pressure
Ps is assumed to be 0, or if the suction pressure
Ps is much smaller than the interstage pressure
Pi and the discharge pressure
Pd, (i.e. 5% or less of the discharge pressure), then the actual cavitation severity
level
Ra can be simplified to:

[0023] This simplified relationship only utilizes two pressure measuring components, one
for measuring discharge pressure (
Pd), and the other is used for measuring interstage pressure (
Pi).
[0024] As previously noted, when a pump 2 cavitates, or gas bubbles pass thru the pump,
the pressure gradient between suction and discharge can no longer be maintained, and
interstage pressure
Pi will always decrease. Therefore, a decreasing actual cavitation severity level
Ra will be observed where the cavitation condition continues to deteriorate. The disclosed
system 1 enables a user to input an application based cavitation severity level
Ru, which is smaller than system's target level
RT. The actual cavitation severity level
Ra is then compared to the application based cavitation severity level
Ru, and if
Ra is determined to be lower than the defined
Ru level, the system identifies the cavitation level as being at an unacceptable level
for the application. The lower the
Ru value, the more severe the cavitation a pump is allowed to experience. In some embodiments,
Ru may be selected to be a value that corresponds to a cavitation level that involves
no obvious noises and/or vibration.
[0025] The system 1 acquires the pressure signals from the sensors 4, 6, 8 and converts
them to digital values for further computation. The actual system's cavitation severity
ratio
Ra can then be calculated according to formula (3) or (4). In some embodiments, multiple
samples may be obtained for a given sampling cycle to obtain an average reading to
make sure the value is stable and substantially free of the effects of pressure fluctuation
caused by gear teeth or screw ridges. The value
Ra can then be compared with target level
RT as well as the user input cavitation severity level
Ru.
[0026] In some embodiments, the speed of the pump 2 may be automatically adjusted based
on this comparison. Thus, pump speed 2 may be automatically increased or decreased
based on the calculated actual severity level
Ra. For example, if
Ra is equal to, or within a predetermined range of, the user's application based severity
level
Ru, then a current operation condition of the pump can be maintained. In some embodiments,
this range may be about 5%. This is because even if the severity level indicates that
the pump 2 is cavitating, the level of cavitation has been determined by the user
to be acceptable for the particular application.
[0027] If, however,
Ra is determined to be larger than user's application based level
Ru, the speed of the pump 2 may be increased until
Ra is equal to, or within a predetermined range of, the user's application based level
Ru. Alternatively, if
Ra is smaller than user's application based level
Ru, the speed of the pump may be decreased until
Ra is equal to, or within a predetermined range of, the user's application based level
Ru. In some embodiments, this range may be about 5%.
[0028] The user may also choose to change pump speed or to stop the pump 2 based on
Ru,
RT and the calculated value for
Ra. For example, the user may configure the system 1 so that the pump is stopped whenever
Ra is less than application based level
Ru. Other predetermined stop levels may also be used.
[0029] In some embodiments, an absolute lower limit of the cavitation severity level
RL can be defined in order to prevent the pump from cavitation damage. Thus,
RL may be defined to correspond to a cavitation level at which noise and/or vibration
may cause damage to the pump. Thus, the application based severity level
Ru will typically be between
RL and
RT. As such, whenever calculated actual severity level
Ra is below
RL, the pump will be stopped to prevent further damage.
[0030] The system 1 may store a plurality of historical actual level
Ra values in memory 34. A standard deviation
RSTD of these historical levels can be calculated to determine if changes in the historical
levels exceed a certain amount
RB. This value
RB can be used as an indicator that gas bubbles are passing through the pump 2. The
value of
RB can be user adjustable based on the particular application. In use, if a calculated
standard deviation
RSTD exceeds the predetermined value for
RB, the user can choose from a variety of action, increasing pump speed, deceasing pump
speed, or stopping the pump.
[0031] Ra and other system information can also be sent out for external use, controls, and/or
making other decisions. In some embodiments, this information can be used to increase
or decrease pump flow rate, or to prompt a user to modify
Ra or another system parameter. This data can also be used for long term operational
and maintenance trending purposes, which can be used to predict and/or optimize maintenance
schedules. The data can also be used to identify fluid characteristic changes or process
changes that may be causing the pump to cavitate.
[0032] FIG. 5 shows an embodiment of the system 1 that facilitates remote access of measured and/or
calculated parameters. As shown, the system 1 includes pump 2 with a plurality of
sensors coupled to a controller 28 via a plurality of individual communications links
30. The controller 28 includes a local display 36 and keyboard 38. In the illustrated
embodiment, the display and keyboard are combined into a touch screen format, which
can include one or more "hard" keys, as well as one or more "soft" keys. The controller
28 of this embodiment is coupled to a modem 40 which enables a remote computer 42
to access the controller 28. The remote computer 42 may be used to display identical
information to that displayed locally at the controller 28. The modem 40 may enable
the controller 28 to promulgate e-mail, text messages, and pager signals to alert
a user about the condition of the pump 2 being monitored. In some embodiments, one
or more aspect of the operation of the pump 2 may also be controlled via the remote
computer 42.
[0033] FIG. 6 illustrates an exemplary logic flow describing a method for monitoring cavitation
in a positive displacement pump 2 and for controlling pump operation based on such
monitoring. The method begins at step 100. At step 110, a plurality of samples of
discharge pressure are obtained, and an average discharge pressure
Pd value is determined. The number of samples, or sampling rate, can be determined based
on the number teeth (or number of screw ridges) (T) of the pump screw(s) or gears,
and an actual operating speed (V) (rpm) of the pump. In some embodiments, the sampling
rate is selected to be larger than the frequency of pulses caused by the passing teeth
(or screw ridges), which in one embodiment is calculated according to the formula:
T*V/60 (Hz). At step 120, a plurality of samples of interstage pressure are obtained,
and an average interstage pressure value
Pi is determined. At step 130, a plurality of samples of suction pressure are obtained,
and an average suction pressure value
Ps is determined. At step 140, an actual cavitation severity level
Ra is determined. In one embodiment,
Ra is determined according to formula (3) or (4). At step 150, a target cavitation severity
level
RT is determined. In one embodiment,
RT is determined according to formula (2). At step 160, stored values of an application
cavitation severity level
Ru and a cavitation severity low limit
RL are read from memory. In one embodiment,
Ru and
RL are input by a user depending upon a particular application of the pump. At step
170, a determination is made as to whether control is enabled. When control is enabled,
whenever the actual cavitation severity level
Ra drops below the application based cavitation severity level
Ru, the system will change the pump speed, and will then determine whether the cavitation
condition improves (i.e., whether
Ra raises above
Ru). Often, the pump speed will be reduced in order to improve the pump operation. When
control is not enabled, the system will simply generate alarms when the actual cavitation
severity level
Ra drops below the application based cavitation severity level
Ru. If control is not enabled, then at step 180, the sampled and calculated values from
steps 110-150 are stored in memory and are sent through communication ports for alarm
notification purposes. The method then returns to step 110. If control is determined
to be enabled, then at step 190, a determination is made as to whether
Ra is less than
RL. If
Ra is less than
RL, then at step 200 the pump 2 is stopped. The method then proceeds to step 180, where
the sampled and calculated values from steps 110-150 are stored in memory and are
sent through communication ports. The method then returns to step 110. If, however,
at step 190 it is determined that
Ra is not less than
RL, then at step 210 a determination is made as to whether
Ra is less than
Ru. If
Ra is less than
Ru, then at step 220, pump operating speed is decreased. The rate of the speed reduction
can be predetermined and/or adjustable by the user, and at the next iteration of the
control loop, the system will repeat the evaluation. At step 230, the value of
Ra is stored in memory, and a number "N" of most recently stored values of
Ra are read from memory. In one embodiment, the number "N" is determined according to
the formula: T*V/60, where "T" is the number of pump screw teeth or ridges, and "V"
is the operating speed of the pump in RPM. At step 240, a standard deviation of the
read values of
Ra is calculated to determine
Rstd. At step 250, a stored value of bubble and gas standard level
RB is read from memory. In one embodiment, the value of
RB is input by a user depending upon a particular application of the pump. At step 260,
a determination is made as to whether
RSTD is greater than
RB. If it is determined that
RSTD is not greater than
RB, then the method proceeds to step 180, where the sampled and calculated values from
steps 110-150, and 230-250 are stored in memory and are also sent through communication
ports. The method then returns to step 110. If, however, at step 260 it is determined
that
RSTD is not greater than
RB, then at step 270 air or gas bubbles are determined to be passing through the pump,
and an operational characteristic of the pump is automatically adjusted. The operational
characteristic can include changing pump speed or stopping the pump. The method then
proceeds to step 180, where the sampled and calculated values from steps 110-150,
and 230-250 are stored in memory and are also sent through communication ports. The
method then returns to step 110. If, at step 210, it is determined that Ra is not
less than
Ru, then at step 280, pump operating speed is increased. The method then proceeds to
step 230 in the manner previously described.
[0034] Some embodiments of the disclosed device may be implemented, for example, using a
storage medium, a computer-readable medium or an article of manufacture which may
store an instruction or a set of instructions that, if executed by a machine, may
cause the machine to perform a method and/or operations in accordance with embodiments
of the disclosure. Such a machine may include, for example, any suitable processing
platform, computing platform, computing device, processing device, computing system,
processing system, computer, processor, or the like, and may be implemented using
any suitable combination of hardware and/or software. The computer-readable medium
or article may include, for example, any suitable type of memory unit, memory device,
memory article, memory medium, storage device, storage article, storage medium and/or
storage unit, for example, memory (including non-transitory memory), removable or
non-removable media, erasable or non-erasable media, writeable or re-writeable media,
digital or analog media, hard disk, floppy disk, Compact Disk Read Only Memory (CD-ROM),
Compact Disk Recordable (CD-R), Compact Disk Rewriteable (CD-RW), optical disk, magnetic
media, magneto-optical media, removable memory cards or disks, various types of Digital
Versatile Disk (DVD), a tape, a cassette, or the like. The instructions may include
any suitable type of code, such as source code, compiled code, interpreted code, executable
code, static code, dynamic code, encrypted code, and the like, implemented using any
suitable high-level, low-level, object-oriented, visual, compiled and/or interpreted
programming language.
[0035] Based on the foregoing information, it will be readily understood by those persons
skilled in the art that the present invention is susceptible of broad utility and
application. Accordingly, while the present invention has been described herein in
detail in relation to its preferred embodiment, it is to be understood that this disclosure
is only illustrative and exemplary of the present invention and is made merely for
the purpose of providing a full and enabling disclosure of the invention. The foregoing
disclosure is not intended to be construed to limit the present invention or otherwise
exclude any other embodiments, adaptations, variations, modifications or equivalent
arrangements; the present invention being limited only by the claims appended hereto.
Although specific terms are employed herein, they are used in a generic and descriptive
sense only and not for the purpose of limitation.
1. A system (1) for monitoring and controlling a positive displacement pump (2), comprising:
a plurality of pressure sensors mounted to the positive displacement pump, the plurality
of pressure sensors (4, 6, 8) comprising at least first (4), second (6) and third
pressure sensors (8), wherein the first pressure sensor (4) is separated from the
second pressure sensor (6) by a first distance (Li) and the first pressure sensor
(4) is separated from the third pressure sensor (6) by a second distance (L); and
a controller (28) for receiving input signals (Ps, Pi, Pd) from the plurality of pressure
sensors (4, 6, 8), and for processing said input signals (Ps, Pi, Pd) to obtain a
cavitation severity ratio, the cavitation severity ratio comprising a ratio of the
difference between a measured interstage pressure of the pump (2) and a measured suction
pressure of the pump (2) and the difference between a measured discharge pressure
of the pump (2) and a measured suction pressure of the pump (2);
the controller (28) being characterised in that it is further configured to adjust an operating speed of the pump (2) based on a
comparison of the cavitation severity ratio to a predefined application based severity
level and a target cavitation severity level, the application based severity level
being set by a user and the target cavitation severity level being based on a ratio
between the first distance (Li) and the second distance (L).
2. The system (1) of claim 1, wherein when the cavitation severity ratio is within a
predetermined range of the application based severity level, a current operating speed
of the pump (2) is maintained.
3. The system (1) of claim 1, wherein when the cavitation severity ratio is greater than
the application based severity level, a speed of the pump (2) is increased until the
cavitation severity ratio is within a predetermined range of the application based
severity level.
4. The system (1) of claim 1, wherein when the cavitation severity ratio is less than
the application based severity level, a speed of the pump (2) is decreased until the
cavitation severity ratio is within a predetermined range of the application based
severity level.
5. The system (1) of claim 1, wherein when the cavitation severity ratio is less than
an application based severity level limit, the pump is stopped.
6. The system (1) of claim 1, wherein the cavitation severity ratio
Ra is obtained according to the formula:

where
Pi is the measured interstage pressure of the pump,
Ps is the measured suction pressure of the pump, and
Pd is the measured discharge pressure of the pump.
7. The system (1) of claim 1, the controller (28) further configured to store a plurality
of discrete values of cavitation severity ratio over time, and to obtain a standard
deviation of the plurality of discrete values to determine if a change in the plurality
of discrete values exceeds a predetermined limit.
8. The system (1) of claim 7, wherein when the change in the plurality of discrete values
exceeds the predetermined limit, the controller (28) is configured to provide an indication
to a user that gas bubbles are present in the pump cavity.
9. The system (1) of claim 8, wherein in response to the indication, the controller (28)
is configured to receive a user input to change an operating condition of the pump
(2).
10. A method for monitoring and controlling a positive displacement pump (2), comprising:
obtaining a plurality of signals (Ps, Pi, Pd) representative of pressures at a plurality
of locations in the positive displacement pump (2);
processing the plurality of signals (Ps, Pi, Pd) to obtain a cavitation severity ratio,
the cavitation severity ratio comprising a ratio of the difference between a measured
interstage pressure of the pump (2) and a measured suction pressure of the pump (2)
and the difference between a measured discharge pressure of the pump (2) and a measured
suction pressure of the pump (2); and being characterised in that
adjusting an operating speed of the positive displacement pump (2) is based on a comparison
of the cavitation severity ratio to a predefined application based severity level
and a target cavitation severity level, the application based severity level being
set by a user and the target cavitation severity level being based on a ratio of distances
between the plurality of locations.
11. The method of claim 10, further comprising maintaining a current operating speed of
the pump (2) when the cavitation severity ratio is within a predetermined range of
the application based severity level.
12. The method of claim 10, wherein when the cavitation severity ratio is greater than
the application based severity level, the method comprises increasing a speed of the
pump (2) until the cavitation severity ratio is within a predetermined range of the
application based severity level.
13. The method of claim 10, wherein when the cavitation severity ratio is less than the
application based severity level, the method comprises decreasing a speed of the pump
(2) until the cavitation severity ratio is within a predetermined range of the application
based severity level.
14. The method of claim 10, wherein when the cavitation severity ratio is less than an
application based severity limit, the method comprises stopping the pump (2).
1. System (1) zum Überwachen und Steuern einer Verdrängungspumpe (2), umfassend:
eine Vielzahl von Drucksensoren, die an der Verdrängungspumpe montiert sind, wobei
die Vielzahl von Drucksensoren (4, 6, 8) mindestens erste (4), zweite (6) und dritte
Drucksensoren (8) umfasst, wobei der erste Drucksensor (4) von dem zweiten Drucksensor
(6) durch einen ersten Abstand (Li) getrennt ist und der erste Drucksensor (4) von
dem dritten Drucksensor (6) durch einen zweiten Abstand (L) getrennt ist; und
eine Steuerung (28) zum Empfangen von Eingangssignalen (Ps, Pi, Pd) von der Vielzahl
von Drucksensoren (4, 6, 8) und zum Verarbeiten der Eingangssignale (Ps, Pi, Pd),
um ein Kavitationsausmaßverhältnis zu erhalten, wobei das Kavitationsausmaßverhältnis
ein Verhältnis der Differenz zwischen einem gemessenen Zwischendruck der Pumpe (2)
und einem gemessenen Ansaugdruck der Pumpe (2) und der Differenz zwischen einem gemessenen
Entladedruck der Pumpe (2) und einem gemessenen Ansaugdruck der Pumpe (2) umfasst;
wobei die Steuerung (28) dadurch gekennzeichnet ist, dass sie
weiter konfiguriert ist, eine Betriebsgeschwindigkeit der Pumpe (2) basierend auf
einem Vergleich des Kavitationsausmaßverhältnisses mit einem vordefinierten anwendungsbasierten
Ausmaßgrad und einem Zielkavitationsausmaßgrad anzupassen, wobei der anwendungsbasierte
Ausmaßgrad von einem Anwender eingestellt wird und der Zielkavitationsausmaßgrad auf
einem Verhältnis zwischen dem ersten Abstand (Li) und dem zweiten Abstand (L) basiert.
2. System (1) nach Anspruch 1, wobei, wenn das Kavitationsausmaßverhältnis innerhalb
einer vorgegebenen Spanne des anwendungsbasierten Ausmaßgrads ist, eine aktuelle Betriebsgeschwindigkeit
der Pumpe (2) beibehalten wird.
3. System (1) nach Anspruch 1, wobei, wenn das Kavitationsausmaßverhältnis größer als
der anwendungsbasierte Ausmaßgrad ist, eine Geschwindigkeit der Pumpe (2) erhöht wird,
bis das Kavitationsausmaßverhältnis innerhalb einer vorgegebenen Spanne des anwendungsbasierten
Ausmaßgrads ist.
4. System (1) nach Anspruch 1, wobei, wenn das Kavitationsausmaßverhältnis kleiner als
der anwendungsbasierte Ausmaßgrad ist, eine Geschwindigkeit der Pumpe (2) verringert
wird, bis das Kavitationsausmaßverhältnis innerhalb einer vorgegebenen Spanne des
anwendungsbasierten Ausmaßgrads ist.
5. System (1) nach Anspruch 1, wobei, wenn das Kavitationsausmaßverhältnis kleiner als
eine anwendungsbasierte Ausmaßgradgrenze ist, die Pumpe gestoppt wird.
6. System (1) nach Anspruch 1, wobei das Kavitationsausmaßverhältnis
Ra gemäß der Formel erhalten wird:

wo
Pi der gemessene Zwischendruck der Pumpe ist,
Ps der gemessene Ansaugdruck der Pumpe ist und
Pd der gemessene Entladedruck der Pumpe ist.
7. System (1) nach Anspruch 1, wobei die Steuerung (28) weiter konfiguriert ist, eine
Vielzahl von diskreten Werten von Kavitätsausmaßverhältnis über die Zeit zu speichern
und eine Standardabweichung der Vielzahl von diskreten Werten zu erhalten, um zu ermitteln,
ob eine Änderung in der Vielzahl von diskreten Werten eine vorgegebene Grenze überschreitet.
8. System (1) nach Anspruch 7, wobei, wenn die Änderung in der Vielzahl von diskreten
Werten die vorgegebene Grenze überschreitet, die Steuerung (28) konfiguriert ist,
eine Anzeige an einen Anwender bereitzustellen, dass Gasblasen in der Pumpenkavität
vorhanden sind.
9. System (1) nach Anspruch 8, wobei in Antwort auf die Anzeige die Steuerung (28) konfiguriert
wird, einen Anwendereingang zu empfangen, um einen Betriebszustand der Pumpe (2) zu
ändern.
10. Verfahren zum Überwachen und Steuern einer Verdrängungspumpe (2), umfassend:
Erhalten einer Vielzahl von Signalen (Ps, Pi, Pd), die Drücke bei einer Vielzahl von
Stellen in der Verdrängungspumpe (2) darstellen;
Verarbeiten der Vielzahl von Signalen (Ps, Pi, Pd), um ein Kavitätsausmaßverhältnis
zu erhalten, wobei das Kavitätsausmaßverhältnis ein Verhältnis der Differenz zwischen
einem gemessenen Zwischendruck der Pumpe (2) und einem gemessenen Ansaugdruck der
Pumpe (2) und der Differenz zwischen einem gemessenen Entladedruck der Pumpe (2) und
einem gemessenen Ansaugdruck der Pumpe (2) umfasst; und dadurch gekennzeichnet ist, dass,
Anpassen einer Betriebsgeschwindigkeit der Verdrängungspumpe (2) auf einem Vergleich
des Kavitationsausmaßverhältnisses mit einem vordefinierten anwendungsbasierten Ausmaßgrad
und einem Zielkavitationsausmaßgrad basiert, wobei der anwendungsbasierte Ausmaßgrad
von einem Anwender eingestellt wird und der Zielkavitationsausmaßgrad auf einem Verhältnis
von Abständen zwischen der Vielzahl von Stellen basiert.
11. Verfahren nach Anspruch 10, weiter umfassend Beibehalten einer Betriebsgeschwindigkeit
der Pumpe (2), wenn das Kavitätsausmaßverhältnis innerhalb einer vorgegebenen Spanne
des anwendungsbasierten Ausmaßgrads ist.
12. Verfahren nach Anspruch 10, wobei, wenn das Kavitätsausmaßverhältnis größer als der
anwendungsbasierte Ausmaßgrad ist, das Verfahren umfasst, eine Geschwindigkeit der
Pumpe (2) zu erhöhen, bis das Kavitätsausmaßverhältnis innerhalb einer vorgegebenen
Spanne des anwendungsbasierten Ausmaßgrads ist.
13. Verfahren nach Anspruch 10, wobei, wenn das Kavitätsausmaßverhältnis kleiner als der
anwendungsbasierte Ausmaßgrad ist, das Verfahren umfasst, eine Geschwindigkeit der
Pumpe (2) zu verringern, bis das Kavitätsausmaßverhältnis innerhalb einer vorgegebenen
Spanne des anwendungsbasierten Ausmaßgrads ist.
14. Verfahren nach Anspruch 10, wobei, wenn das Kavitätsausmaßverhältnis kleiner als eine
anwendungsbasierte Ausmaßgrenze ist, das Verfahren umfasst, die Pumpe (2) zu stoppen.
1. Système (1) pour la surveillance et la commande d'une pompe volumétrique (2) comprenant
:
une pluralité de capteurs de pression montés sur la pompe volumétrique, la pluralité
de capteurs de pression (4, 6, 8) comprenant au moins des premier (4), deuxième (6)
et troisième capteurs de pression (8), dans lequel le premier capteur de pression
(4) est séparé du deuxième capteur de pression (6) d'une première distance (Li) et
le premier capteur de pression (4) est séparé du troisième capteur de pression (6)
d'une seconde distance (L) ; et
un dispositif de commande (28) pour la réception de signaux d'entrée (Ps, Pi, Pd)
de la pluralité de capteurs de pression (4, 6, 8), et pour le traitement desdits signaux
d'entrée (Ps, Pi, Pd) afin d'obtenir un rapport de sévérité de cavitation, le rapport
de sévérité de cavitation comprenant un rapport de la différence entre une pression
interétage mesurée de la pompe (2) et une pression d'aspiration mesurée de la pompe
(2) et la différence entre une pression de décharge mesurée de la pompe (2) et une
pression d'aspiration mesurée de la pompe (2) ;
le dispositif de commande (28) étant caractérisé en ce qu'il est
en outre configuré pour ajuster une vitesse opérationnelle de la pompe (2) sur la
base d'une comparaison du rapport de sévérité de cavitation avec un niveau de sévérité
basé sur l'application prédéfini et un niveau de sévérité de cavitation cible, le
niveau de sévérité basé sur l'application étant réglé par un utilisateur et le niveau
de sévérité de cavitation cible étant basé sur un rapport entre la première distance
(Li) et la seconde distance (L).
2. Système (1) selon la revendication 1, dans lequel lorsque le rapport de sévérité de
cavitation est dans une plage prédéterminée du niveau de sévérité basé sur l'application,
une vitesse opérationnelle actuelle de la pompe (2) est maintenue.
3. Système (1) selon la revendication 1, dans lequel lorsque le rapport de sévérité de
cavitation est supérieur au niveau de sévérité basé sur l'application, une vitesse
de la pompe (2) est augmentée jusqu'à ce que le rapport de sévérité de cavitation
soit dans une plage prédéterminée du niveau de sévérité basé sur l'application.
4. Système (1) selon la revendication 1, dans lequel lorsque le rapport de sévérité de
cavitation est inférieur au niveau de sévérité basé sur l'application, une vitesse
de la pompe (2) est diminuée jusqu'à ce que le rapport de sévérité de cavitation soit
dans une plage prédéterminée du niveau de sévérité basé sur l'application.
5. Système (1) selon la revendication 1, dans lequel lorsque le rapport de sévérité de
cavitation est inférieur à une limite de niveau de sévérité basé sur l'application,
la pompe est arrêtée.
6. Système (1) selon la revendication 1, dans lequel le rapport de sévérité de cavitation
Ra est obtenu selon la formule :

où
Pi est la pression interétage mesurée de la pompe,
Ps est la pression d'aspiration mesurée de la pompe, et Pd est la pression de décharge
mesurée de la pompe.
7. Système (1) selon la revendication 1, le dispositif de commande (28) étant en outre
configuré pour stocker une pluralité de valeurs discrètes de rapport de sévérité de
cavitation dans le temps, et pour obtenir une déviation standard de la pluralité de
valeurs discrètes pour déterminer si un changement dans la pluralité de valeurs discrètes
excède une limite prédéterminée.
8. Système (1) selon la revendication 7, dans lequel lorsque le changement dans la pluralité
de valeurs discrètes excède la limite prédéterminée, le dispositif de commande (28)
est configuré pour fournir une indication à un utilisateur sur la présence de bulles
de gaz dans la cavité de pompe.
9. Système (1) selon la revendication 8, dans lequel en réponse à l'indication, le dispositif
de commande (28) est configuré pour recevoir une entrée utilisateur afin de changer
une condition opérationnelle de la pompe (2).
10. Procédé de surveillance et de commande d'une pompe volumétrique (2), comprenant :
l'obtention d'une pluralité de signaux (Ps, Pi, Pd) représentatifs de pressions à
une pluralité d'emplacements dans la pompe volumétrique (2) ;
le traitement de la pluralité de signaux (Ps, Pi, Pd) pour obtenir un rapport de sévérité
de cavitation, le rapport de sévérité de cavitation comprenant un rapport de la différence
entre une pression interétage mesurée de la pompe (2) et une pression d'aspiration
mesurée de la pompe (2) et la différence entre une pression de décharge mesurée de
la pompe (2) et une pression d'aspiration mesurée de la pompe (2) ; et étant caractérisé en ce que
l'ajustement d'une vitesse opérationnelle de la pompe volumétrique (2) est basé sur
une comparaison du rapport de sévérité de cavitation à un niveau de sévérité basé
sur l'application et un niveau de sévérité de cavitation cible, le niveau de sévérité
basé sur l'application étant réglé par un utilisateur et le niveau de sévérité de
cavitation cible étant basé sur un rapport de distances entre la pluralité d'emplacements.
11. Procédé selon la revendication 10, comprenant en outre le maintien d'une vitesse opérationnelle
actuelle de la pompe (2) lorsque le rapport de sévérité de cavitation est dans une
plage prédéterminée du niveau de sévérité basé sur l'application.
12. Procédé selon la revendication 10, dans lequel lorsque le rapport de sévérité de cavitation
est supérieur au niveau de sévérité basé sur l'application, le procédé comprend l'augmentation
d'une vitesse de la pompe (2) jusqu'à ce que le rapport de sévérité de cavitation
soit dans une plage prédéterminée du niveau de sévérité basé sur l'application.
13. Procédé selon la revendication 10, dans lequel lorsque le rapport de sévérité de cavitation
est inférieur au niveau de sévérité basé sur l'application, le procédé comprend la
diminution d'une vitesse de la pompe (2) jusqu'à ce que le rapport de sévérité de
cavitation soit dans une plage prédéterminée du niveau de sévérité basé sur l'application.
14. Procédé selon la revendication 10, dans lequel lorsque le rapport de sévérité de cavitation
est inférieur à une limite de sévérité basée sur l'application, le procédé comprend
l'arrêt de la pompe (2).