U.S. patent application number 16/172870 was filed with the patent office on 2019-05-02 for detection apparatus, detection method, and computer readable medium.
The applicant listed for this patent is Yokogawa Electric Corporation. Invention is credited to Soichiro Konada, Takaaki Matsuda, Norio Tanaka.
Application Number | 20190128288 16/172870 |
Document ID | / |
Family ID | 66243575 |
Filed Date | 2019-05-02 |
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United States Patent
Application |
20190128288 |
Kind Code |
A1 |
Konada; Soichiro ; et
al. |
May 2, 2019 |
DETECTION APPARATUS, DETECTION METHOD, AND COMPUTER READABLE
MEDIUM
Abstract
Easily detecting cavitation to occur in a pump. A detection
apparatus, a detection method, and a program are provided. The
detection apparatus includes: a discharge pressure acquiring unit
to acquire discharge pressure data indicating discharge pressure of
a pump; and a detector to detect occurrence of cavitation in the
pump based on a fluctuation amount of a time waveform of the
discharge pressure data during a target detection period. The
detector may have: a fluctuation amount calculator to calculate the
fluctuation amount of the discharge pressure data during the target
detection period; and a determining unit to determine, in response
to the calculated fluctuation amount becoming the reference
fluctuation amount or more, that cavitation has occurred in the
pump.
Inventors: |
Konada; Soichiro; (Tokyo,
JP) ; Tanaka; Norio; (Tokyo, JP) ; Matsuda;
Takaaki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yokogawa Electric Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
66243575 |
Appl. No.: |
16/172870 |
Filed: |
October 29, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/669 20130101;
F04B 49/08 20130101; F04B 49/065 20130101; F04B 11/00 20130101;
F04D 15/0088 20130101; F04B 2205/04 20130101; F04B 51/00 20130101;
F04B 2205/02 20130101 |
International
Class: |
F04D 29/66 20060101
F04D029/66; F04D 15/00 20060101 F04D015/00; F04B 49/06 20060101
F04B049/06 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2017 |
JP |
2017-211094 |
Claims
1. A detection apparatus comprising: a discharge pressure acquiring
unit to acquire discharge pressure data indicating discharge
pressure of a pump; and a detector to detect occurrence of
cavitation in the pump based on a fluctuation amount of a time
waveform of the discharge pressure data during a target detection
period.
2. The detection apparatus according to claim 1, wherein the
detector has: a fluctuation amount calculator to calculate the
fluctuation amount of the discharge pressure data during the target
detection period; and a determining unit to determine that
cavitation has occurred in the pump, in response to the calculated
fluctuation amount becoming reference fluctuation amount or
more.
3. The detection apparatus according to claim 2, wherein the
fluctuation amount calculator calculates, as the fluctuation
amount, difference between reference pressure data and the
discharge pressure data during the target detection period.
4. The detection apparatus according to claim 3, wherein the
fluctuation amount calculator calculates the difference between the
discharge pressure data during the target detection period and the
reference pressure data for a time length equal to the target
detection period as the fluctuation amount.
5. The detection apparatus according to claim 3, wherein the
fluctuation amount calculator uses the discharge pressure data that
is acquired by the discharge pressure acquiring unit before the
target detection period as the reference pressure data.
6. The detection apparatus according to claim 5, further
comprising: a suction pressure acquiring unit to acquire suction
pressure data showing suction pressure of the pump, wherein the
fluctuation amount calculator uses as the reference pressure data
the discharge pressure data acquired corresponding to timing at
which the suction pressure data changes from a value exceeding a
threshold value to a value equal to or less than the threshold
value.
7. The detection apparatus according to claim 6, wherein the
fluctuation amount calculator uses the discharge pressure data that
is acquired corresponding to a timing at which the suction pressure
data changes from being a positive pressure value to a negative
pressure value as the reference pressure data.
8. The detection apparatus according to claim 6, wherein the
fluctuation amount calculator uses discharge pressure data for a
time length equal to the target detection period immediately before
the timing as the reference pressure data.
9. The detection apparatus according to claim 3, wherein the
fluctuation amount calculator is to, relatively shift the reference
pressure data to the discharge pressure data during the target
detection period, and match a mean value of the reference pressure
data with a mean value of the discharge pressure data during the
target detection period, and calculate, as the fluctuation amount,
difference between the discharge pressure data and the reference
pressure data during the target detection period, of which mean
values are matched.
10. The detection apparatus according to claim 1, further
comprising: a fluctuation amount accumulating unit to calculate a
cumulative value of the fluctuation amount; and a maintenance
managing unit to determine at least one of time to maintain and
time to replace the pump based on the cumulative value of the
fluctuation amount.
11. A detection apparatus comprising: a suction pressure acquiring
unit to acquire suction pressure data indicating suction pressure
of a pump; a discharge pressure acquiring unit to acquire discharge
pressure data indicating discharge pressure of the pump; and a
detector to detect whether cavitation is occurring in the pump
based on the discharge pressure data in response to the suction
pressure data becoming a threshold value or less.
12. The detection apparatus according to claim 11, further
comprising: a predicting unit to predict occurrence of cavitation
in the pump in response to the suction pressure data becoming the
threshold value or less.
13. A detection apparatus comprising: a discharge pressure
acquiring unit to acquire discharge pressure data indicating
discharge pressure of a pump; and a detector to detect occurrence
of cavitation in the pump based on difference between the discharge
pressure data during a target detection period and the discharge
pressure data before the target detection period.
14. A detection method comprising: acquiring discharge pressure
data indicating discharge pressure of a pump; and detecting
occurrence of cavitation in the pump based on a fluctuation amount
of a time waveform of the discharge pressure data during a target
detection period.
15. A computer readable medium to store a program, the program
causing a computer to serve as: a discharge pressure acquiring unit
to acquire discharge pressure data indicating discharge pressure of
a pump; and a detector to detect occurrence of cavitation in the
pump based on a fluctuation amount of a time waveform of the
discharge pressure data during a target detection period.
16. A detection method comprising: acquiring suction pressure data
indicating suction pressure of a pump; acquiring discharge pressure
data indicating discharge pressure of the pump; and detecting
whether cavitation is occurring in the pump based on the discharge
pressure data in response to the suction pressure data becoming a
threshold value or less.
17. A computer readable medium to store a program, the program
causing a computer to serve as: a suction pressure acquiring unit
to acquire suction pressure data indicating suction pressure of a
pump; a discharge pressure acquiring unit to acquire discharge
pressure data indicating discharge pressure of the pump; and a
detector to detect whether cavitation is occurring in the pump
based on the discharge pressure data in response to the suction
pressure data becoming a threshold value or less.
18. A detection method comprising: acquiring discharge pressure
data indicating discharge pressure of a pump; and detecting
occurrence of cavitation in the pump based on difference between
the discharge pressure data during a target detection period and
the discharge pressure data before the target detection period.
19. A computer readable medium to store a program, the program
causing a computer to serve as: a discharge pressure acquiring unit
to acquire discharge pressure data indicating discharge pressure of
a pump; and a detector to detect occurrence of cavitation in the
pump based on difference between the discharge pressure data during
a target detection period and the discharge pressure data before
the target detection period.
Description
[0001] The contents of the following Japanese patent application
are incorporated herein by reference.
[0002] NO. 2017-211094 filed in JP on Oct. 31, 2017.
BACKGROUND
1. Technical Field
[0003] The present invention relates to a detection apparatus, a
detection method, and a program.
2. Related Art
[0004] Cavitation may occur to a pump that sucks and discharges
liquid due to the liquid evaporating. Conventionally, a technique
to detect occurrence of such cavitation has been known, in which
frequency analysis is performed on discharge pressure of the pump
(refer to Patent Document 1, for example).
[0005] Patent Document 1: Japanese Patent Application Publication
No. S64-45975.
[0006] However, according to the technique in Patent Document 1, an
arithmetic processing of the frequency analysis can be a large
burden. For example, in a case of a plant including numerous pumps,
i.e., from hundreds to thousands or more pumps, it is possible that
cavitation is treated for each pump. Thus, a technique to
efficiently detect cavitation by performing less arithmetic
processing is desired.
SUMMARY
[0007] A first aspect of the present invention provides a detection
apparatus, a detection method, and a program. The detection
apparatus includes: a discharge pressure acquiring unit to acquire
discharge pressure data indicating discharge pressure of a pump;
and a detector to detect occurrence of cavitation in the pump based
on a fluctuation amount of a time waveform of the discharge
pressure data during a target detection period.
[0008] A second aspect of the present invention provides a
detection apparatus, a detection method, and a program. The
detection apparatus includes: a suction pressure acquiring unit to
acquire suction pressure data indicating suction pressure of a
pump; a discharge pressure acquiring unit to acquire discharge
pressure data indicating discharge pressure of the pump; and a
detector to detect whether cavitation is occurring in the pump
based on the discharge pressure data in response to the suction
pressure data becoming a threshold value or less.
[0009] A third aspect of the present invention provides a detection
apparatus, a detection method, and a program. The detection
apparatus includes: a discharge pressure acquiring unit to acquire
discharge pressure data indicating discharge pressure of a pump;
and a detector to detect occurrence of cavitation in the pump based
on difference between the discharge pressure data during a target
detection period and the discharge pressure data before the target
detection period.
[0010] The summary clause does not necessarily describe all
necessary features of the embodiments of the present invention. The
present invention may also be a sub-combination of the features
described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 illustrates an exemplary configuration of a plant 10
to which a detection apparatus 100 according to the present
embodiment is provided.
[0012] FIG. 2 illustrates an example of suction pressure data and
discharge pressure data acquired by the detection apparatus 100
according to the present embodiment.
[0013] FIG. 3 illustrates an exemplary configuration of the
detection apparatus 100 according to the present embodiment.
[0014] FIG. 4 illustrates an exemplary operation flow of the
detection apparatus 100 according to the present embodiment.
[0015] FIG. 5 illustrates one example of a fluctuation amount of
discharge pressure data calculated by a fluctuation amount
calculator 160 according to the present embodiment.
[0016] FIG. 6 illustrates a modification example of the detection
apparatus 100 according to the present embodiment.
[0017] FIG. 7 illustrates an exemplary configuration of a computer
1200 in which a plurality of aspects of the present invention may
be embodied.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0018] Hereinafter, the present invention will be described with
reference to embodiments of the invention. However, the following
embodiments shall not be construed as limiting the claimed
invention. Also, not all combinations of features described in the
embodiments are essential for means to solve problems provided by
aspects of the invention.
[0019] FIG. 1 illustrates an exemplary configuration of a plant 10
to which a detection apparatus 100 according to the present
embodiment is provided. The plant 10 is a system to control
equipment or the like while supplying liquid to the equipment or
the like by a pump. The plant 10 may be at least a part of a plant
facility, machinery, a production apparatus, power generating
apparatus, or the like. The plant 10 includes equipment 20, a
liquid source 30, a pump 40, a suction pressure gauge 50, a
discharge pressure gauge 60, and a control system 70. Note that, at
least some of the equipment 20, the liquid source 30, the pump 40,
the suction pressure gauge 50, the discharge pressure gauge 60, and
a detection apparatus 100 which are included in the plant 10 may be
plural.
[0020] The equipment 20 is subject to control by the plant 10. The
equipment 20 may be at least a part for plant equipment, machinery,
a production apparatus, power generating apparatus, a storage
apparatus, or the like. The equipment 20 may include an apparatus
supplied with liquid such as water, oil, fuel, coolant, or
chemicals in order to perform processing operation using the
liquid. The equipment 20 may include a plurality of
apparatuses.
[0021] The liquid source 30 stores or supplies the liquid supplied
to the equipment 20. The liquid source 30 may be a tank or the like
to preserve and store the liquid, and may also maintain pressure of
the liquid. The liquid source 30 may also be a well, an oil well,
or the like, which is provided in a region where a resource such as
groundwater or oil field is accumulated or reserved. The liquid
source 30 may also be a river, a pond, a lake, a dam, or the like.
The liquid source 30 may also be a tank to store liquid supplied by
another pump. The liquid source 30 may also be a pipe connected to
a tank or the like.
[0022] The pump 40 supplies the equipment 20 with the liquid of the
liquid source 30. The pump 40 connects between the liquid source 30
and the equipment 20 using a valve, pipe, or the like. FIG. 1
illustrates an example of a moving direction of liquid inside the
pipe with an arrow from the liquid source 30 to the equipment 20.
The pump 40 may be a volute pump having a rotor in a vane shape (an
impeller) or the like. Also, the pump 40 may be a diffuser pump, a
cascade pump, an axial flow pump, a mixed flow pump, a cross flow
pump, or the like. A plurality of pumps 40 may be arranged in the
plant 10.
[0023] The suction pressure gauge 50 is provided between the liquid
source 30 and the pump 40 and measures suction pressure of the pump
40. The discharge pressure gauge 60 is provided between the
equipment 20 and the pump 40 and measures discharge pressure of the
pump 40. Each of the suction pressure gauge 50 and the discharge
pressure gauge 60 is, for example, a differential pressure flow
meter, a pressure transmitter, or the like. The suction pressure
gauge 50 and the discharge pressure gauge 60 may serve as sensors
to detect operation of the pump 40. A suction pressure gauge 50 and
a discharge pressure gauge 60 may be provided to each pump 40. FIG.
1 illustrates an example in which the plant 10 is provided with one
liquid source 30, one pump 40, one suction pressure gauge 50, and
one discharge pressure gauge 60. Note that, at least one of the
suction pressure gauge 50 and the discharge pressure gauge 60 may
be used to control the plant 10.
[0024] The control system 70 controls a part or the whole of the
equipment 20, the pump 40, and the like based on a measurement
result of a measuring instrument such as a sensor provided in a
plant. Also, the control system 70 may control a valve provided in
a pipe or the like, which is provided in a plant. For example, the
control system 70 controls and/or monitors operation of the
equipment 20, the pump 40, the valve, and the like based on
measurement data obtained by measuring the operation of the
equipment 20, and measurement data for pressure, temperature, a
flow rate, storage capacity, or the like of fluid of liquid etc.
that is treated in the plant 10.
[0025] The control system 70 is connected to the equipment 20 or
the like via wireless and/or wired communication equipment, and may
be arranged at a position away from the equipment 20 or the like.
The control system 70 may be constructed as an automatic operation
system and/or a maintenance system such as a DCS (Distributed
Control system) and a SCADA (Supervisory Control And Data
Acquisition) system. In this case, the control system 70 may
exchange control data and measurement data with each unit at a
frequency of approximately several Hz to several kHz.
[0026] It is desirable that the above-mentioned plant 10 can
perform control, maintenance, management, or the like of the
equipment 20 as well as the pump 40. For example, cavitation or the
like may occur to the pump 40 and may cause noise, and in some
cases, it results in degradation and/or breakage of the pump 40. It
is desirable for the plant 10 to be able to perform control,
maintenance, management, or the like in order to suppress as much
occurrence of such unstable operation as possible by monitoring the
operation of the pump 40.
[0027] It is known to detect cavitation of the pump 40 in order to
monitor the operation of such pump 40 by: performing numerical
processing such as the Fourier transform on the discharge pressure
data acquired from the discharge pressure gauge 60; and detecting
abnormality on a frequency axis. However, it is difficult to detect
the abnormality on the frequency axis unless the unstable operation
of the pump 40 progresses to the state in which an obvious
fluctuation characteristic of a certain frequency or a certain
frequency band occurs to the discharge pressure data. That is,
temporal difference occurs from the occurrence of cavitation to the
detection of the cavitation, which makes it difficult to deal with
the cavitation in some cases.
[0028] Also, such plant 10 illustrated in FIG. 1 can be a
large-scale control system including from hundreds to thousands or
more of pumps 40. Thus, providing one processing circuit to perform
numerical processing for each pump 40 causes high cost.
Furthermore, since the plant 10 communicates with each unit at a
frequency of approximately several Hz to several kHz, it is
difficult to perform accumulation of data, numerical processing,
analysis of a result, or the like at high speed. Hence, it is
desired for such plant 10 to detect cavitation in real time while
preventing increase in cost, and further to predict occurrence of
cavitation.
[0029] Therefore, the detection apparatus 100 is provided to such
plant 10 to detect cavitation in real time based on temporal
fluctuation of discharge pressure data. The detection apparatus 100
is configured to be applicable to an existing plant 10 or the like,
and can detect cavitation by acquiring the discharge pressure data
or the like. Note that, the detection apparatus 100 may be included
in the control system 70. Also, the detection apparatus 100 may be
included in a measuring instrument such as a sensor provided in the
plant 10. FIG. 1 illustrates an example in which the detection
apparatus 100 is included in the control system 70. First, suction
pressure data and discharge pressure data acquired by the detection
apparatus 100 will be described.
[0030] FIG. 2 illustrates an example of suction pressure data and
discharge pressure data acquired by the detection apparatus 100
according to the present embodiment. In FIG. 2, the horizontal axes
represent the time and vertical axes represent the suction pressure
and the discharge pressure respectively. FIG. 2 is an example to
show change in the suction pressure data and the discharge pressure
data, each of which correspond to approximately the same lapse of
time, by showing each measurement data in approximately the same
time scale. Note that, the suction pressure data is an example of a
measurement result of the suction pressure gauge 50, and the
discharge pressure data is an example of a measurement result of
the discharge pressure gauge 60.
[0031] Along with the operation of the pump 40, the suction
pressure data may show pressure lower than the atmospheric pressure
(negative pressure). FIG. 2 shows an example in which the suction
pressure data gradually decreases and shows pressure lower than the
atmospheric pressure from time t.sub.0 onwards. Accordingly, if the
suction pressure becomes lower than the atmospheric pressure,
cavitation may occur due to pressure of liquid supplied from the
pump 40 to the equipment 20 being equal to or lower than saturated
steam pressure and the liquid evaporating.
[0032] Note that, as shown in FIG. 2, if a noise component is
superimposed on the suction pressure data, the suction pressure
data may show pressure lower than the atmospheric pressure before
time t.sub.0. Therefore, it is desirable that the detection
apparatus 100 performs filtering processing on the suction pressure
data such as averaging, smoothing, noise removing, and/or high
frequency removal. Also, the suction pressure gauge 50 and the
discharge pressure gauge 60 may supply data on which such filtering
processing has been performed.
[0033] The discharge pressure data gradually decreases
corresponding to the gradual decrease of the suction pressure data.
FIG. 2 shows an example in which the gradual decrease in the
suction pressure data continues with the lapse of time, and
unstable fluctuation occurs to the discharge pressure data from
approximately time t.sub.n onwards. Note that, with respect to the
discharge pressure data from time t.sub.n onwards, unstable
fluctuation is occurring and causing the discharge pressure data to
oscillate, and an amplitude value is gradually increasing. Yet the
discharge pressure data is still in a state in which obvious
oscillation of a certain frequency or a certain frequency band is
not occurring. That is, for example, even if the Fourier transform
is performed on the discharge pressure data in period T, i.e., from
time t.sub.n to time t.sub.n+T, amplitude strength of a certain
frequency band may not be the frequency characteristic that is
different compared with a amplitude strength of another band. Thus,
robustness is also required in the detection apparatus 100.
[0034] Hence, if the discharge pressure data is converted to a
frequency axis, cavitation cannot be detected until an obvious
frequency signal occurs with the time further preceding the time
range shown in FIG. 2. The detection apparatus 100 according to the
present embodiment can detect occurrence of cavitation in the time
range illustrated in FIG. 2 based on such time waveforms shown in
FIG. 2. Such detection apparatus 100 will be described next.
[0035] FIG. 3 illustrates an exemplary configuration of the
detection apparatus 100 according to the present embodiment. FIG. 3
illustrates an exemplary configuration of detection apparatus 100
that detects cavitation occurring in the pump 40 based on suction
pressure data and discharge pressure data. Note that, each of the
suction pressure gauge 50, the discharge pressure gauge 60, and the
control system 70 may be connected to the detection apparatus 100
via wired or wireless connection or the like. The detection
apparatus 100 may be connected to them via a network or the like.
The detection apparatus 100 includes a discharge pressure acquiring
unit 110, a suction pressure acquiring unit 120, and a detector
130.
[0036] The discharge pressure acquiring unit 110 acquires discharge
pressure data indicating the discharge pressure of the pump 40. The
discharge pressure acquiring unit 110 may be connected to the
discharge pressure gauge 60 and may receive the discharge pressure
data from the discharge pressure gauge 60. Also, if the discharge
pressure data is stored in an external database or the like, the
discharge pressure acquiring unit 110 may access the database or
the like to acquire the discharge pressure data. Additionally, the
discharge pressure acquiring unit 110 may acquire the discharge
pressure data from the control system 70. The discharge pressure
acquiring unit 110 supplies the detector 130 with the acquired
discharge pressure data.
[0037] The suction pressure acquiring unit 120 acquires the suction
pressure data indicating suction pressure of the pump 40. The
suction pressure acquiring unit 120 may be connected to the suction
pressure gauge 50 and may receive the suction pressure data from
the suction pressure gauge 50. Also, if the suction pressure data
is stored in a database or the like, the suction pressure acquiring
unit 120 may access the database or the like to acquire the suction
pressure data. Additionally, the suction pressure acquiring unit
120 may acquire the suction pressure data from the control system
70. The suction pressure acquiring unit 120 supplies the detector
130 with the acquired suction pressure data.
[0038] In response to the suction pressure data becoming a
threshold value or less, the detector 130 detects whether
cavitation is occurring in the pump 40 based on the discharge
pressure data. The detector 130 detects the occurrence of
cavitation in the pump 40 based on, for example, a fluctuation
amount of a time waveform of discharge pressure data during a
target detection period. The detector 130 has a storage unit 140, a
comparator 150, a fluctuation amount calculator 160, and a
determining unit 170.
[0039] The storage unit 140 stores the suction pressure data and
the discharge pressure data. Also, the storage unit 140 may be able
to store data processed by the detection apparatus 100. The storage
unit 140 may store each of intermediate data, a calculated result,
a parameter, and the like. The intermediate data is calculated (or
utilized) by the detection apparatus 100 in a process of generating
a detection result. Also, in response to a request from each unit
in the detection apparatus 100, the storage unit 140 may supply the
stored data to the requesting unit. For example, in response to a
request from the comparator 150, the storage unit 140 supplies the
comparator 150 with the stored suction pressure data.
[0040] The comparator 150 compares the suction pressure data with
the predetermined threshold value. For example, the threshold value
may be a pressure data value corresponding to the atmospheric
pressure. In response to the suction pressure data becoming the
threshold value or less, the comparator 150 notifies the
fluctuation amount calculator 160 of the comparison result. That
is, the comparator 150 may notify the fluctuation amount calculator
160 about the suction pressure data changing from being a positive
pressure value to a negative pressure value.
[0041] The fluctuation amount calculator 160 calculates a
fluctuation amount of the discharge pressure data during the target
detection period. For example, in response to the notification from
the comparator 150, the fluctuation amount calculator 160 reads out
the discharge pressure data from the storage unit 140 and
calculates a fluctuation amount of the discharge pressure data. The
fluctuation amount calculator 160 may set reference pressure data
and may calculate the fluctuation amount of the discharge pressure
data from the difference between the reference pressure data and
the discharge pressure data. Here, the fluctuation amount
calculator 160 uses, for example, the discharge pressure data
acquired by the discharge pressure acquiring unit 110 before the
target detection period as the reference pressure data. The
fluctuation amount calculator 160 supplies the determining unit 170
with the calculated fluctuation amount.
[0042] The determining unit 170 determines, in response to a
fluctuation amount calculated by the fluctuation amount calculator
160 becoming the reference fluctuation amount or more, that
cavitation has occurred in the pump 40. In response to determining
the occurrence of cavitation, the determining unit 170 notifies the
control system 70 of the determination result.
[0043] As described above, the detection apparatus 100 according to
the present embodiment detects occurrence of cavitation based on
the fluctuation amount of the discharge pressure data. More
specific operation of such detection apparatus 100 will be
described next.
[0044] FIG. 4 illustrates an exemplary operation flow of the
detection apparatus 100 according to the present embodiment. The
detection apparatus 100 performs the operation flow illustrated in
FIG. 4 to detect occurrence of cavitation.
[0045] First, the detection apparatus 100 acquires discharge
pressure data and suction pressure data (S410). That is, the
discharge pressure acquiring unit 110 acquires the discharge
pressure data and the suction pressure acquiring unit 120 acquires
the suction pressure data. The pressure data acquired by each of
the discharge pressure acquiring unit 110 and the suction pressure
acquiring unit 120 may be stored in the storage unit 140. The
discharge pressure acquiring unit 110 may acquire pressure data
every time the discharge pressure gauge 60 performs sampling on the
pressure data, and the suction pressure acquiring unit 120 may
acquire pressure data every time the suction pressure gauge 50
performs sampling on the pressure data. Instead of this, they may
collectively acquire the pressure data every time a predetermined
number of times of sampling has been performed.
[0046] Next, the comparator 150 compares the suction pressure data
with a threshold value (S420). For example, if the suction pressure
data exceeds the threshold value (No at S420), the comparator 150
determines that a tendency of cavitation is not detected. In this
case, the detection apparatus 100 returns to S410 and acquires
discharge pressure data and suction pressure data to be sampled
next.
[0047] Note that, if the suction pressure acquiring unit 120
acquires the next suction pressure data and stores it in the
storage unit 140, the previous suction pressure data may be erased.
In this case, the suction pressure acquiring unit 120 may overwrite
the previously acquired suction pressure data stored in the storage
unit 140 with the suction pressure data acquired next.
[0048] Also, the discharge pressure acquiring unit 110 may erase
discharge pressure data before the predetermined period T. For
example, if the next discharge pressure data is acquired at
t.sub.k+1, the discharge pressure acquiring unit 110 erases
discharge pressure data before time t.sub.k-T. In this case, the
discharge pressure acquiring unit 110 may overwrite the discharge
pressure data before time t.sub.k-T, which is stored in the storage
unit 140, with discharge pressure data acquired next at time
t.sub.k+1. Accordingly, if pressure data is acquired at time
t.sub.k, the storage unit 140 at least stores the suction pressure
data and the discharge pressure data acquired at time t.sub.k and
the discharge pressure data acquired from time t.sub.k-T, which is
back in time from time t.sub.k by a period T, to time t.sub.k.
[0049] The discharge pressure acquiring unit 110, the suction
pressure acquiring unit 120, and the comparator 150 repeat
acquiring the pressure data and comparing the suction pressure data
with the threshold value until the suction pressure data becomes
the threshold value or less. Then, if the suction pressure data
becomes the threshold value or less (Yes at S420), the comparator
150 determines that a tendency of cavitation is starting to appear,
and notifies the fluctuation amount calculator 160 of the
comparison result. Here, an example in which the threshold value is
a pressure data value corresponding to the atmospheric pressure,
and the comparator 150 notifies the fluctuation amount calculator
160 about the suction pressure data becoming the threshold value or
less at time t.sub.0 as shown in FIG. 2 is described.
[0050] Next, the fluctuation amount calculator 160 sets reference
pressure data (S430). Here, time t.sub.0-T is back in time from the
time t.sub.0 by a period T. For example, the fluctuation amount
calculator 160 reads out the discharge pressure data acquired from
the storage unit 140 from time t.sub.0-T to time t.sub.0 and sets
the discharge pressure data as reference pressure data. That is,
the fluctuation amount calculator 160 uses as the reference
pressure data the data including the discharge pressure data
acquired corresponding to a timing t.sub.0 at which the suction
pressure data is changed from being a value exceeding the threshold
value to the threshold value or less. In the present example, an
example in which the fluctuation amount calculator 160 uses as
reference pressure data the discharge pressure data acquired from
timing t.sub.0-T to the timing t.sub.0 is described. The timing
t.sub.0-T is back in time from a predetermined period T by the
timing t.sub.0.
[0051] The fluctuation amount calculator 160 may store the
reference pressure data that has been set in the storage unit 140.
Note that, if previous reference pressure data has been stored in
the storage unit 140, the fluctuation amount calculator 160 may
overwrite it with the newest reference pressure data that has been
set.
[0052] Next, the detection apparatus 100 acquires discharge
pressure data and suction pressure data at next sampling time
(S440). That is, the discharge pressure acquiring unit 110 acquires
the discharge pressure data and the suction pressure acquiring unit
120 acquires the suction pressure data. Note that, if it is
immediately after time t.sub.0 elapses, the discharge pressure
acquiring unit 110 and the suction pressure acquiring unit 120 may
continue acquiring the pressure data until a period T elapses,
i.e., until time t.sub.0+T.
[0053] Next, the comparator 150 compares the suction pressure data
with a threshold value (S450). If the comparison result shows that
the suction pressure data exceeds the threshold value (Yes at
S450), the detection apparatus 100 may determine that a tendency of
cavitation has disappeared and a normal operation state has been
restored, and return to S410. In this case, the comparator 150 may
erase information about the reference pressure data from the
storage unit 140.
[0054] Note that, it is desirable that the threshold value used for
comparison by the comparator 150 at S450 is different from the
threshold value used at S420. For example, if the threshold value
used at S420 is a first threshold value, a second threshold value
used at S450 is larger than the first threshold value by a
predetermined value. That is, in order to reduce effect of noise or
the like that is superimposed on the suction pressure data, the
comparator 150 may perform comparison having hysteresis. For
example, the second threshold value is obtained by adding
acceptable magnitude of noise or the like to the first threshold
value.
[0055] If the suction pressure data is the threshold value or less
(No at S450), the comparator 150 may determine that the tendency of
cavitation is continuing and notify the fluctuation amount
calculator 160 of this fact.
[0056] Next, the fluctuation amount calculator 160 calculates a
fluctuation amount of discharge pressure data (S460). The
fluctuation amount calculator 160 sets as a target detection period
a period from timing t.sub.2-T to timing t.sub.2. This t.sub.2 is
the latest detection timing of the discharge pressure data acquired
by the discharge pressure acquiring unit 110 at S440, and this
timing t.sub.2-T is back in time from the timing t.sub.2 by a
predetermined period T. Note that, if the discharge pressure
acquiring unit 110 continues acquiring the pressure data until time
t.sub.0+T, the fluctuation amount calculator 160 may set the target
detection period as a period from time t.sub.0 to time
t.sub.0+T.
[0057] Then, the fluctuation amount calculator 160 calculates as a
fluctuation amount difference between reference pressure data and
discharge pressure data during the target detection period.
Accordingly, the fluctuation amount calculator 160 may calculate as
a fluctuation amount difference between discharge pressure data
during the target detection period and reference pressure data in a
time length T having equal length as the target detection period.
For example, the fluctuation amount calculator 160 relatively
shifts time axes of the discharge pressure data and the reference
pressure data, and calculates difference between the discharge
pressure data and the reference pressure data corresponding to each
time.
[0058] The fluctuation amount calculator 160 may set a value
obtained by summing up (integrating) the difference between the
discharge pressure data and the reference pressure data as a
fluctuation amount. Also, the fluctuation amount calculator 160 may
set a value obtained by summing up absolute values of the
difference between the discharge pressure data and the reference
pressure data as a fluctuation amount. If no change occurs to the
discharge pressure data in the target detection period, or if the
change is relatively small, the fluctuation amount calculated by
the fluctuation amount calculator 160 is a value no larger than
difference in integrated value of noise. For example, with respect
to the target detection period from time t.sub.m to time t.sub.m+T
in FIG. 2, change is not occurring in the discharge pressure data
to the extent that occurrence of cavitation is recognized. That is,
the difference between the discharge pressure data in the target
detection period and the reference pressure data from time
t.sub.0-T to time t.sub.0 is no larger than the noise level.
[0059] Next, the determining unit 170 compares the fluctuation
amount calculated by the fluctuation amount calculator 160 with a
reference fluctuation amount (S470). Here, the reference
fluctuation amount may be predetermined based on a fluctuation
amount of the discharge pressure data to detect. Also, the
reference fluctuation amount may be no larger than a value obtained
by integrating a value of noise accepted by the discharge pressure
data by the number of times of sampling during the period T. For
example, if a fluctuation amount is less than the reference
fluctuation amount (No at S470) as shown in the target detection
period from time t.sub.m to time t.sub.m+T, the detection apparatus
100 returns to S440 and acquires the next discharge pressure data
and suction pressure data.
[0060] The discharge pressure acquiring unit 110, the suction
pressure acquiring unit 120, and the detector 130 compare the
fluctuation amount of the discharge pressure data in the next
target period with the reference fluctuation amount in the next
target period. Note that, the next target period may be from timing
back in time from a next sampling timing of the pressure data by a
period T to the sampling timing. That is, the next target period
may be shifted from the last target period by one period of
sampling timing.
[0061] Instead of this, the next target period may be shifted by N
times of periods of sampling timing compared with the last target
period (N is an integer of two or more). In this case, at S440, the
discharge pressure acquiring unit 110 and the suction pressure
acquiring unit 120 acquire results obtained by sampling the
pressure data for N times. Note that, it is desirable that a period
in which N times of sampling is performed is shorter than the
period T.
[0062] The discharge pressure acquiring unit 110, the suction
pressure acquiring unit 120, and the detector 130 repeat operation
from S440 to S470 until the fluctuation amount of the discharge
pressure data for the next target period becomes the reference
fluctuation amount or more (or until it is determined Yes at S450).
Then, if the fluctuation amount of the discharge pressure data
becomes the reference fluctuation amount or more (Yes at S470), the
determining unit 170 determines that the cavitation has occurred
(S480).
[0063] For example, since change is occurring to the discharge
pressure data to the extent that occurrence of cavitation is
recognized in the target detection period from time t.sub.n to time
t.sub.n+T in FIG. 2, the fluctuation amount of the discharge
pressure data becomes the reference fluctuation amount or more. In
this case, the determining unit 170 determines that cavitation has
occurred, and notifies the control system 70 of this fact. As
described above, the fluctuation amount calculator 160 according to
the present embodiment uses as reference pressure data, which is
the data during the normal operation of the pump 40, discharge
pressure data of time length T having equal length as a target
detection period immediately before the timing at which the suction
pressure data changes from being a positive pressure value to a
negative pressure value. A fluctuation amount of discharge pressure
data based on such reference pressure data and the discharge
pressure data in the target period will be described next.
[0064] FIG. 5 illustrates one example of a fluctuation amount of
discharge pressure data calculated by a fluctuation amount
calculator 160 according to the present embodiment. In FIG. 5, the
horizontal axis represents the time and the vertical axis
represents the discharge pressure. FIG. 5 shows an example in which
the fluctuation amount calculator 160 relatively shifts time axes
of the discharge pressure data and reference pressure data. That
is, FIG. 5 shows an example in which start timing and end timing of
the discharge pressure data and the reference pressure data are set
to time t.sub.01, and time t.sub.02 respectively. Note that, time
t.sub.02 is forward in time from time t.sub.01 by time T.
[0065] Here, the fluctuation amount calculator 160 may adjust
offset of the discharge pressure data and the reference pressure
data. For example, the fluctuation amount calculator 160 may
relatively shift the reference pressure data to the discharge
pressure data during the target detection period such that a mean
value of the reference pressure data matches a mean value of the
discharge pressure data during the target detection period. Also,
the fluctuation amount calculator 160 may perform a filtering
processing such as a high-pass filter to remove direct current
components. Additionally, the suction pressure gauge 50 and the
discharge pressure gauge 60 may supply data on which filtering
processing has been performed.
[0066] The fluctuation amount calculator 160 may calculate, as a
fluctuation amount, difference between reference pressure data and
discharge pressure data during the target detection period, which
have a corresponding mean value. In FIG. 5, areas illustrated with
oblique lines are an example of difference between the discharge
pressure data and the reference pressure data. As shown in FIG. 5,
the difference between the discharge pressure data and the
reference pressure data may have difference larger than noise in an
initial stage of cavitation in which change occurs to the discharge
pressure data in the target detection period.
[0067] That is, by using a time waveform of the discharge pressure
data, the detection apparatus 100 according to the present
embodiment can detect occurrence of cavitation even before obvious
oscillation of a certain frequency or a frequency band occurs. Note
that, pressure data acquired from a plant 10 under a normal
operation state may also pulse. For example, if liquid flowing
through the pump 40 is mixture, pulsation may occur to the pressure
data in response to the mixture ratio changing. Also, pulsation may
occur to the pressure data depending on environmental change or the
like of the plant 10. As described above, a fluctuation width of
certain degree of range may be seen even in the pressure data in a
normal state. Therefore, by making the period of the reference
pressure data approximately the same as the period T in the target
detection period in such manner described with respect to the
present embodiment, effect of the fluctuation width can be
reduced.
[0068] Also, because the detection apparatus 100 does not perform
numerical processing such as the Fourier transform, low cost can be
achieved without using a complicated circuit, a high-performance
CPU, or the like. Additionally, because the detection apparatus 100
subsequently compares next data while erasing unnecessary previous
data, storage capacity for data can be reduced.
[0069] Note that, the detection apparatus 100 according to the
present embodiment is described with the example in which it
compares time waveforms of the reference pressure data and the
discharge pressure data having the same time length as described in
FIG. 5. However, this is not the sole example. The detection
apparatus 100 may use reference pressure data having a time length
shorter than that of the time waveform of discharge pressure data
in the target period. In this case, the fluctuation amount
calculator 160 may calculate each difference between a mean value
of the reference pressure data and individual piece of data of
discharge pressure data in the target period.
[0070] Also, the fluctuation amount calculator 160 may use as the
reference pressure data one piece of discharge pressure data that
is acquired corresponding to a timing t.sub.0 at which the suction
pressure data is changed from being a value exceeding the threshold
value to a value of the threshold value or less. That is, the
fluctuation amount calculator 160 may use as the reference pressure
data the discharge pressure data that is acquired corresponding to
a timing at which the suction pressure data changes from being a
positive pressure value to a negative pressure value. In this case,
the fluctuation amount calculator 160 may calculate each difference
between one sample of the reference pressure data and individual
piece of data of discharge pressure data in the target period.
[0071] As described above, it is desirable that the detection
apparatus 100 uses as reference pressure data the discharge
pressure data of a period, time, or the like that is closer to the
timing t.sub.0 at which the suction pressure data changes from
being a value exceeding the threshold value to a value equal to or
less than the threshold value. In this way, temporal difference
between the reference pressure data and the discharge pressure data
in the target detection period can be shorter in time. That is,
even if pulse occurs to pressure data, fluctuation widths of
fluctuation to occur to reference pressure data and discharge
pressure data of a target detection period can be approximately the
same, and thus effect of the pulse can be reduced.
[0072] Although it is described that the above-mentioned detection
apparatus 100 according to the present embodiment can detect
occurrence of cavitation, it is not limited thereto. The detection
apparatus 100 may further predict occurrence of cavitation. Also,
the detection apparatus 100 may provide information about
maintenance and management of the pump 40. Such detection apparatus
100 will be described next.
[0073] FIG. 6 illustrates a modification example of the detection
apparatus 100 according to the present embodiment. With respect to
the detection apparatus 100 of the present modification example,
approximately the same operation as the operation of detection
apparatus 100 according to the present embodiment illustrated in
FIG. 3 is illustrated with the same reference numeral, and
description thereof is omitted. A detector 130 of the detection
apparatus 100 of the present modification example further has a
predicting unit 210, a fluctuation amount accumulating unit 220,
and a maintenance managing unit 230.
[0074] In response to the suction pressure data becoming the
threshold value or less, the predicting unit 210 predicts
occurrence of cavitation of the pump 40. In this case, in response
to the suction pressure data becoming the threshold value or less,
the comparator 150 notifies the fluctuation amount calculator 160
and the predicting unit 210 of the comparison result. The
predicting unit 210 predicts occurrence of cavitation in response
to, for example, the suction pressure data changing from being a
positive pressure value to a negative pressure value.
[0075] As described in FIG. 2, before the cavitation occurs, the
suction pressure data is gradually decreased towards a negative
pressure value. Hence, the predicting unit 210 can predict
cavitation to occur in the future depending on whether the suction
pressure data has changed to the negative pressure value. In this
way, the control system 70 can perform control of preventing
occurrence of the cavitation, preparation for performing control on
cavitation, and the like before the cavitation occurs. Hence, not
only the control system 70 can reduce occurrence of cavitation but
also rapidly handle cavitation when it occurs.
[0076] Note that, in the present embodiment, an example in which
the threshold value is set as a value corresponding to the
atmospheric pressure is described. However, this is not the sole
example. Because a value of suction pressure data for determining a
tendency of cavitation may vary depending on a type,
characteristic, individual difference of the pump 40, design of the
control system 70, or the like, the threshold value may be
predetermined corresponding to them. Also, different threshold
value may be set by the comparator 150 from a threshold value used
in a case of determining whether to notify fluctuation amount
calculator 160, to a threshold value used in a case of determining
whether to notify the predicting unit 210.
[0077] The fluctuation amount accumulating unit 220 calculates a
cumulative value of a fluctuation amount of the discharge pressure
data. The fluctuation amount accumulating unit 220 may receive a
fluctuation amount calculated by the fluctuation amount calculator
160 to calculate the cumulative value. Also, the fluctuation amount
accumulating unit 220 may calculate the cumulative value every time
cavitation occurs. Additionally, the fluctuation amount
accumulating unit 220 may count frequency of occurrence of
cavitation, duration of the cavitation, or the like. The
fluctuation amount accumulating unit 220 may store the accumulated
information about the cavitation in the storage unit 140.
[0078] Based on the cumulative value of fluctuation amount of the
discharge pressure data, the frequency of cavitation, the duration
of the cavitation, and/or the like, the maintenance managing unit
230 determines at least one of a time to maintain and time to
replace the pump 40. Because the cavitation occurring in the pump
40 caused damage to the pump 40, it is considered that the
cavitation affects life time of the pump 40. Because a fluctuation
amount of the discharge pressure data corresponds to amplitude
strength of oscillation of the cavitation, it can be utilized as an
indicator of the damage the pump 40 has received. Hence, by
accumulating and recording the fluctuation amount of the discharge
pressure data, inspection timing and replacement timing of the pump
40 can be determined.
[0079] The maintenance managing unit 230 may determine the
inspection timing and the replacement timing of the pump 40 by, for
example, comparing the cumulative value of the fluctuation amount
of the discharge pressure data with a predetermined threshold value
or the like. In response to the cumulative value becoming the
threshold value or more, the maintenance managing unit 230 may
notify the control system 70 of the inspection timing and/or the
replacement timing. Note that, the maintenance managing unit 230
may set a different value from a threshold value to determine the
inspection timing to a threshold value to determine the replacement
timing. Also, the maintenance managing unit 230 may predetermine
the threshold value based on data regarding an actual malfunction
occurred in the pump 40, life time of the pump 40, and the
like.
[0080] As described above, the detection apparatus 100 according to
the modification example can not only detect cavitation but also
perform prediction of cavitation, and maintenance and management of
the pump 40 at low cost. Note that, the detection apparatus 100 may
only perform the prediction of cavitation or may only perform
maintenance and management of the pump 40.
[0081] With regard to the detection apparatus 100 according to the
present embodiment described above, an example in which calculation
of the fluctuation amount of the discharge pressure data is started
in response to the suction pressure data becoming the threshold
value or less is described. In this way, the detection apparatus
100 can be prevented from performing calculation or the like in
vain in a range in which the suction pressure data is a normal
value, and can prevent power consumption from increasing. Also,
because the detection apparatus 100 can reduce amount of
calculation, even if it is implemented on the control system 70, it
can be prevented from affecting the control system 70 as a load.
Additionally, even if the detection apparatus 100 is included in a
measuring instrument such as a sensor provided in the plant 10, it
can be prevented from affecting operation thereof as a load.
Furthermore, because the detection apparatus 100 does not perform
detection of cavitation in a range in which the suction pressure
data is a normal value, frequency of erroneous detection caused by
noise or the like can be reduced.
[0082] Note that, the detection apparatus 100 is not even limited
to comparing time waveforms, if considering such reduced power
consumption and reduced frequency of the erroneous detection. For
example, in response to the suction pressure data becoming the
threshold value or less, the detection apparatus 100 may perform
frequency analysis for the discharge pressure data. In this case,
the fluctuation amount calculator 160 may perform the Fourier
transform on the discharge pressure data. Also, with respect to a
frequency characteristic of the discharge pressure data, the
determining unit 170 may determine whether abnormality has been
occurring in a certain wavelength or a certain band. The
determining unit 170 determines occurrence of abnormality by using,
for example, a predetermined threshold value for the certain
wavelength or the certain band. Accordingly, because the detection
apparatus 100 starts the frequency analysis if tendency of
cavitation is seen, it can reduce amount of calculation.
[0083] Accordingly, if the detector 130 performs the frequency
analysis, the operation flow shown in FIG. 4 may be modified as
follows. In S430, in response to the suction pressure data becoming
the threshold value or less, the fluctuation amount calculator 160
sets the frequency characteristic of the reference pressure data.
That is, the discharge pressure data acquired from time t.sub.0-T
to time t.sub.0 is read out from the storage unit 140 and the
Fourier transform (FFT, for example) is performed thereon to set it
as the reference data.
[0084] Also, in S460, if it is determined that the tendency of
cavitation is continuing, the fluctuation amount calculator 160
calculates a frequency characteristic of the discharge pressure
data in the target detection period. Then, the fluctuation amount
calculator 160 calculates difference between the frequency
characteristic in the target detection period and the reference
data on the frequency axis. Accordingly, in S470, the determining
unit 170 can determine occurrence of abnormality depending on
whether the certain wavelength or the certain band of the frequency
characteristic of difference has exceeded the threshold value.
[0085] Instead of this, the operation flow illustrated in FIG. 4
may be modified as follows. In S460, the fluctuation amount
calculator 160 performs frequency conversion on waveform data
indicating difference between reference pressure data and discharge
pressure data during the target detection period. Accordingly, in
S470, the determining unit 170 can determine occurrence of
abnormality depending on whether the certain wavelength or the
certain band of the frequency characteristic of difference has
exceeded the threshold value.
[0086] Although it is described that the above-mentioned detection
apparatus 100 according to the present embodiment detects
cavitation by using suction pressure data and discharge pressure
data, it is not limited thereto. If in a case such as the power
consumption or the like of the plant 10 is saved, such calculation
for the fluctuation amount of the discharge pressure data may
continue in the range in which the suction pressure data is a
normal value. That is, the detection apparatus 100 may detect
cavitation by only using the discharge pressure data.
[0087] For example, the detection apparatus 100 may perform
calculation for the fluctuation amount of the discharge pressure
data regardless of the change of the suction pressure data. In this
case, the detection apparatus 100 may not have the suction pressure
acquiring unit 120 and the comparator 150. In this case, the
detector 130 detects occurrence of cavitation in the pump 40 based
on a fluctuation amount of discharge pressure data during a target
detection period. The detector 130 uses as reference pressure data
the discharge pressure data acquired in a case in which operation
of the pump 40 and/or the detection apparatus 100 is started, for
example.
[0088] Also, the detector 130 may use as the reference pressure
data the discharge pressure data acquired in a case in which the
pump 40 is performing normal operation in advance. Also, the
detector 130 may use as the reference pressure data a predetermined
value such as a design value, an empirical value, or the like.
[0089] Accordingly, if the detection apparatus 100 performs
calculation for the fluctuation amount of the discharge pressure
data regardless of the change of the suction pressure data, the
operation flow shown in FIG. 4 may be modified as follows. That is,
operation in S420 and S450 regarding the suction pressure data are
not performed. Also, with respect to the acquiring of the pressure
data in S410 and S440, it may be sufficient if the discharge
pressure acquiring unit 110 acquires the discharge pressure data.
In this way, based on a time waveform of the discharge pressure
data, the detection apparatus 100 can detect occurrence of
cavitation.
[0090] Accordingly, the detector 130 may detect occurrence of
cavitation in the pump based on difference between discharge
pressure data during a target detection period and discharge
pressure data before the target detection period.
[0091] Note that, in this case, the detector 130 may detect
occurrence of cavitation in the pump based on, for example,
difference between discharge pressure data during a target
detection period and discharge pressure data immediately before the
target detection period.
[0092] Because the fluctuation amount of the discharge pressure
data gradually increases and gets worse after occurrence of
cavitation, the detection apparatus 100 can detect the occurrence
of cavitation by comparing temporally preceding discharge pressure
data with temporally succeeding discharge pressure data. In this
case, the operation flow illustrated in FIG. 4 may be further
modified as follows. That is, in S470, if the fluctuation amount is
less than the reference fluctuation amount (No at S470), return to
S430 instead of S440, and set the discharge pressure data in the
target period as the reference pressure data. Then, the discharge
pressure data for the next target period is acquired (S440).
[0093] In this way, the detection apparatus 100 can compare the
temporally preceding discharge pressure data with the temporally
succeeding discharge pressure data without using the suction
pressure data, and can detect occurrence of cavitation. That is,
the detection apparatus 100 can detect occurrence of cavitation
while having simpler configuration. Also, the detection apparatus
100 can detect change in real time cavitation.
[0094] Note that, if considering the detection of such change in
real time cavitation, the detection apparatus 100 is not limited to
detecting occurrence of cavitation by comparing the difference of
time waveforms with the reference fluctuation amount. For example,
the detection apparatus 100 may detect cavitation by performing
frequency conversion on the difference between discharge pressure
data during the target detection period and the discharge pressure
data before the target detection period.
[0095] In this case, the fluctuation amount calculator 160 may
calculate the difference between the discharge pressure data in the
target detection period and the reference pressure data before
performing the Fourier transform on the difference. With respect to
a frequency characteristic calculated by the fluctuation amount
calculator 160, the determining unit 170 may determine whether
abnormality has been occurring in a certain wavelength or a certain
band. The determining unit 170 determines occurrence of abnormality
by using, for example, a predetermined threshold value for the
certain wavelength or the certain band. This operation can be
realized by further modifying S460 and S470.
[0096] With respect to the detection apparatus 100 according to the
present embodiment described above, an example in which the
pressure data is acquired from a pressure gauge such as the suction
pressure gauge 50 and the discharge pressure gauge 60 is described.
In addition to this, the detection apparatus 100 may also acquire
fault information or the like of the pressure gauge from the
suction pressure gauge 50 and/or the discharge pressure gauge 60.
If a malfunction or the like is occurring to the pressure gauge, it
is difficult to accurately detect occurrence of cavitation. Thus,
if fault information or the like for the pressure gauge is
acquired, the detection apparatus 100 may not perform the detection
of cavitation. Instead of this, the detection apparatus 100 may add
the fault information to a detection result of cavitation and
notify the control system 70.
[0097] An example in which the detection apparatus 100 according to
the present embodiment described above is provided to the plant 10
is described. Note that, the plant 10 is an example of a system
utilizing the pump 40 to transfer liquid. The system to which the
detection apparatus 100 is provided is not limited to the plant 10.
Cavitation may occur to a pump 40 as long as it is for transferring
liquid. Thus, the cavitation may be detected by providing the
detection apparatus 100 to a system, an apparatus, or equipment
using the pump 40, or the site or the like of use of the pump
40.
[0098] FIG. 7 illustrates an exemplary configuration of a computer
1200 in which a plurality of aspects of the present invention may
be fully or partially embodied. A program installed in the computer
1200 can make the computer 1200 function as an operation which is
associated with the apparatus according to the embodiment of the
present invention, or one or more "unit(s)" of the apparatus, or
can make the computer 1200 perform the operation or the one or more
"unit(s)", and/or can make the computer 1200 perform processes
according to the embodiment of the present invention or steps of
the processes. Such programs may be executed by a CPU 1212 so that
the computer 1200 performs particular operations associated with
some or all of blocks in the flowchart and the block diagrams
according to the present specification.
[0099] The computer 1200 according to the present embodiment
includes a CPU 1212, a RAM 1214, a graphics controller 1216, and a
display device 1218, and these are connected to each other by a
host controller 1210. The computer 1200 also includes input/output
units such as a communication interface 1222, a hard disk drive
1224, a DVD-ROM drive 1226 and an IC card drive, which are
connected to the host controller 1210 via an input/output
controller 1220. The computer also includes legacy input/output
units such as a ROM 1230 and a keyboard 1242, these are connected
to the input/output controller 1220 via an input/output chip
1240.
[0100] The CPU 1212 operates according to programs stored in the
ROM 1230 and the RAM 1214, and thereby controls each unit. The
graphics controller 1216 acquires image data generated by the CPU
1212 on a frame buffer or the like provided in the RAM 1214 or in
the graphics controller 1216 itself, and makes the image data to be
displayed on the display device 1218.
[0101] The communication interface 1222 communicates with other
electronic devices via a network. The hard disk drive 1224 stores
programs and data used by the CPU 1212 within the computer 1200.
The DVD-ROM drive 1226 reads the programs or the data from the
DVD-ROM 1201, and provides the hard disk drive 1224 with the
programs or the data via the RAM 1214. The IC card drive reads
programs and data from the IC card, and/or writes programs and data
into the IC card.
[0102] The ROM 1230 stores therein a boot program etc. executed by
the computer 1200 at the time of activation, and/or a program that
depend on the hardware of the computer 1200. The input/output chip
1240 may also connect various input/output units to the
input/output controller 1220 via a parallel port, a serial port, a
keyboard port, a mouse port etc.
[0103] A program is provided by computer readable storage medium
such as the DVD-ROM 1201 or the IC card. The program is read out
from the computer readable storage medium, installed into the hard
disk drive 1224, RAM 1214 or ROM 1230, which are also examples of
computer readable storage medium, and executed by the CPU 1212. The
information processing described in these programs is read out by
the computer 1200, resulting in cooperation between a program and
the above-mentioned various types of hardware resources. An
apparatus or method may be constituted by realizing the operation
or processing of information, according to the usage of the
computer 1200.
[0104] For example, when communication is performed between the
computer 1200 and an external device, the CPU 1212 may execute a
communication program loaded onto the RAM 1214 to instruct
communication processing to the communication interface 1222, based
on the processing described in the communication program. The
communication interface 1222, under control of the CPU 1212, reads
transmission data stored on a transmission buffering region
provided in a recording medium such as the RAM 1214, the hard disk
drive 1224, the DVD-ROM 1201, or the IC card, and transmits the
read transmission data to a network or writes reception data
received from a network to a reception buffering region or the like
provided on the recording medium.
[0105] Additionally, the CPU 1212 may cause all or a necessary
portion of a file or a database to be read into the RAM 1214, the
file or the database having been stored in an external recording
medium such as the hard disk drive 1224, the DVD-ROM drive 1226
(DVD-ROM 1201), the IC card, etc., and perform various types of
processing on the data on the RAM 1214. The CPU 1212 may then write
back the processed data to the external recording medium.
[0106] Various types of information, such as various types of
programs, data, tables, and databases may be stored in the
recording medium for information processing. The CPU 1212 may
perform, on the read-out data from the RAM 1214, various types of
processing which includes various types of operations, information
processing; conditional judging, conditional branch, unconditional
branch, information search/replace etc., as described throughout
the present disclosure and designated by an instruction sequence of
the program, and write backs the result to the RAM 1214. Also, the
CPU 1212 may search for information in a file, a database etc. in
the recording medium. For example, when a plurality of entries,
each of them having an attribute value of a first attribute
associated with an attribute value of a second attribute are stored
in the recording medium, the CPU 1212 may search for, from among
the plurality of entries, an entry where the attribute value of the
first attribute matches a designated condition, may read the
attribute value of the second attribute stored in the entry, and
thereby may acquire the attribute value of the second attribute
associated with the first attribute that satisfies a predetermined
condition.
[0107] The above-explained program or software modules may be
stored in the computer readable storage medium on or near the
computer 1200. Also, a recording medium such as a hard disk or a
RAM provided in a server system connected to a dedicated
communication network or the Internet can be used as the computer
readable storage media, and thereby provide the programs to the
computer 1200 via network.
[0108] While the embodiments of the present invention have been
described, the technical scope of the invention is not limited to
the above described embodiments. It is apparent to persons skilled
in the art that various alterations and improvements can be added
to the above-described embodiments. It is also apparent from the
scope of the claims that the embodiments added with such
alterations or improvements can be included in the technical scope
of the invention.
[0109] The operations, procedures, steps, and stages of each
process performed by an apparatus, system, program, and method
shown in the claims, embodiments, or diagrams can be performed in
any order as long as the order is not indicated by "prior to,"
"before," or the like and as long as the output from a previous
process is not used in a later process. Even if the process flow is
described using phrases such as "first" or "next" in the claims,
embodiments, or diagrams, it does not necessarily mean that the
process must be performed in this order.
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