CN108120574B - Method for monitoring looseness of pipe threaded joint - Google Patents
Method for monitoring looseness of pipe threaded joint Download PDFInfo
- Publication number
- CN108120574B CN108120574B CN201810108140.9A CN201810108140A CN108120574B CN 108120574 B CN108120574 B CN 108120574B CN 201810108140 A CN201810108140 A CN 201810108140A CN 108120574 B CN108120574 B CN 108120574B
- Authority
- CN
- China
- Prior art keywords
- pipe
- threaded
- piezoelectric ceramic
- loosening
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M3/00—Investigating fluid-tightness of structures
- G01M3/40—Investigating fluid-tightness of structures by using electric means, e.g. by observing electric discharges
Abstract
The invention discloses a method for monitoring the looseness of a pipe threaded joint, which is characterized in that piezoelectric ceramic chip sensors are respectively stuck on the surfaces of a threaded pipe and a threaded joint of a pipe thread, firstly, an excitation electric signal is used for exciting one piezoelectric ceramic chip sensor, a piezoelectric stress wave signal generated by the sensor is transmitted through a contact surface between the threaded pipe and the threaded joint in the pipe thread, then, the piezoelectric stress wave signal is captured by the other piezoelectric ceramic chip sensor, converted into an electric signal and collected by an NI signal acquisition card, and the sealing state of the measured pipe thread at the moment is judged and identified by comparing and analyzing the difference between the received signal and the reference value of the received signal in the normal sealing state. The invention applies the piezoelectric ceramic sensor technology, can simply and conveniently realize the monitoring and the identification of the sealing state (loosening and leakage) of the pipe thread, greatly improves the safety of the pipe thread connection, reduces the potential safety hazard and the operation risk, improves the overall economic benefit and generates positive significance.
Description
Technical Field
The invention relates to the technical field of structural health monitoring, relates to threaded connection looseness monitoring, and particularly relates to a method for monitoring looseness of a threaded joint of a pipe.
Background
When the threads of the inner pipe and the outer pipe are combined with each other, the centering and guiding effects are good, the assembly and the disassembly are convenient, and the connecting device can bear larger axial force and torque and is widely applied to the connection of medium-size and small-size pipeline systems. When the pipe thread works, the pipe thread is influenced by various external loads and vibration for a long time, if the pipe thread is not timely and effectively overhauled and maintained, the part of the pipe thread joint is often loosened to cause great damage to the sealing performance of the pipe thread joint, and therefore the problem of how to solve the problem of loosening and leakage of the pipe thread joint in a pipeline with sealing requirements is always concerned by people for a long time.
Piezoelectric ceramics (Lead zirconium Titanate, PZT) has become one of the intelligent materials widely studied and applied in the fields of aerospace, energy, machinery, building structure and the like in recent years due to its specific sensing and actuating functions. The method has the characteristics of quick response, wide frequency range, easiness in cutting, low price and the like, so that the method has great application potential in the aspect of engineering structure monitoring.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for monitoring pipe thread loosening diseases aiming at the blank of the field of pipe thread joint loosening monitoring, and the method can be used for accurately monitoring and identifying the loosening of a pipe thread joint in real time.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a method for monitoring the loosening of a threaded joint for pipes, characterized in that it comprises the following steps:
fixing two piezoelectric ceramic sensors on the surfaces of a threaded joint and a threaded pipe in a surface pasting mode respectively, and performing waterproof insulation treatment on the surfaces of the piezoelectric ceramic sensors;
connecting the two piezoelectric ceramic sensors to a data acquisition card through cables respectively, and then connecting the data acquisition card with a computer analysis terminal;
thirdly, the computer analysis terminal controls the data acquisition card to generate an excitation electric signal with a certain frequency band through a cable, outputs the excitation electric signal through the output end of the data acquisition card, transmits the excitation electric signal to the piezoelectric ceramic sensor serving as a driver through the cable, drives the piezoelectric ceramic sensor to generate mechanical vibration, forms piezoelectric stress waves in the threaded connection of the pipe, and transmits the piezoelectric stress waves along the direction of the pipeline; the other piezoelectric ceramic sensor is used as a receiver, receives piezoelectric stress wave signals transmitted through pipe threaded connection and converts the piezoelectric stress wave signals into electric signals, the electric signals are transmitted to the input end of a data acquisition card through a cable, and the data acquisition card converts the electric signals output by the piezoelectric ceramic sensor used as the receiver into digital signals and transmits the digital signals to a computer analysis terminal;
and step four, under the condition that the normal sealing working state of the pipe thread is defined in a computer analysis system, the measured signal of the piezoelectric ceramic sensor serving as a receiver is used as a reference signal, a recognition characteristic parameter reference value is constructed, then the recognition characteristic parameters of the pipe thread connection measuring signal in different periods under the subsequent service state are monitored, the recognition characteristic parameters and the recognition characteristic parameter reference value are compared and analyzed, the looseness evaluation index of the pipe thread joint is calculated, and the sealing condition of the pipe thread joint is obtained by monitoring the change of the evaluation index.
In the fourth step, the reference signal of the piezoelectric ceramic sensor serving as the receiver in the normal sealing working state of the pipe thread is taken as the acquired signal at the initial stage of the pipe thread installation and use, or the acquired signal is acquired by experiments when the pipe thread is confirmed to be free from loosening and leakage by the detection method in the prior art.
As an improvement, in step four, the characteristic parameter is identified as a direct measurement value or a derivative value that can characterize the signal characteristic.
As an improvement, the identification characteristic parameters comprise one or any combination of a plurality of received signal energy amplitude values, wavelet packet energy values, structure local resonance frequencies, signal fitting regression coefficients, factor analysis coefficients and wavelet packet node coefficients.
As an improvement, the loosening evaluation index comprises a relative change value and/or a relative mean square error of the signal characteristic value of the identification characteristic parameter, and the larger the defined loosening evaluation index is, the more obvious the difference of the service state of the tested pipe threaded joint from the normal sealing state is, namely the greater the possibility of loosening leakage is, the more serious the loosening disease is.
In the first step, epoxy resin is uniformly coated on the surface of the piezoelectric ceramic sensor, and waterproof insulation treatment is carried out.
As an improvement, the data acquisition card is an NI signal acquisition card, the NI signal acquisition card is respectively connected with the two piezoelectric ceramic sensors through a BNC cable, and the NI signal acquisition card is connected with the computer analysis terminal through a USB cable.
As an improvement, the excitation electric signal generated by the computer analysis terminal through the data acquisition card is a sine sweep frequency excitation electric signal.
The invention has the advantages that the piezoelectric ceramic sensor technology is applied to monitoring and identifying the working state (or loosening disease) of the pipe threaded joint, the principle is clear, the cost is low, the operation is simple and easy, the identification is accurate, the long-term online monitoring and identification of the pipe threaded seal working state can be realized, and the positive significance is generated for reducing the loosening leakage disease of the pipe threaded joint, reducing the monitoring and operation maintenance cost of the whole pipeline system, scientifically judging and predicting the service safety and the residual life of the pipe threads, ensuring the safe and efficient operation of the whole pipe threaded system engineering, and maintaining the life and property safety of the majority of people.
In addition, the invention does not need to specially customize the pipe threaded joint to be monitored, and only the piezoelectric ceramic sensor is fixed on the existing pipe threaded joint in a sticking way, thereby being convenient and quick and having low use cost.
Drawings
FIG. 1 is a schematic view of the arrangement of the pipe thread connection and the piezoelectric ceramic sensor of the present invention.
FIG. 2 is a schematic view of the pipe thread loosening state monitoring of the present invention.
FIG. 3 is a schematic comparison of the reduction in thread contact area for a threaded connection of pipes in the sealed and loosened condition;
wherein, fig. 3a is a schematic view of the sealing state of the pipe thread connection, and fig. 3b is a schematic view of the loosening state of the pipe thread connection.
FIG. 4 is a schematic diagram showing the relative position change of two piezoelectric ceramic sensors in the state of sealing and loosening the pipe thread.
In the figure: the system comprises a 1-threaded pipe, a 2-threaded joint, a 3-piezoelectric ceramic sensor, a 4-piezoelectric ceramic sensor, a 5-BNC cable, a 6-NI signal acquisition card, a 7-USB cable and an 8-computer analysis terminal.
Detailed Description
The embodiments of the present invention will be described in detail with reference to the accompanying drawings and examples:
the two threaded pipes 1 are in pipe thread connection through the threaded joints 2, then the piezoelectric ceramic sensors 3 serving as drivers are fixed on the surfaces of the threaded joints 2 in a surface pasting mode, the piezoelectric ceramic sensors 4 serving as receivers are fixed on the surface of one of the pipe threads 1, epoxy resin is uniformly coated on the surfaces of the two piezoelectric ceramic sensors 3 and 4, and waterproof insulation treatment is carried out;
the two piezoelectric ceramic sensors 3 and 4 are respectively connected to an NI signal acquisition card 6 through a BNC cable 5, and the NI signal acquisition card 6 is connected with a computer analysis terminal 8 through a USB cable 7;
the computer analysis terminal 8 controls the NI signal acquisition card 6 to generate a sine sweep frequency excitation electrical signal with a certain frequency band through the USB cable 7, the sine sweep frequency excitation electrical signal is output through the output end of the NI signal acquisition card 6 and is transmitted to the piezoelectric ceramic sensor 3 through the BNC cable 5, the excitation electrical signal drives the piezoelectric ceramic sensor 3 to generate mechanical vibration, piezoelectric stress waves are formed in the pipe threaded connection and are transmitted along the direction of a pipeline; then, the piezoelectric ceramic sensor 4 receives the piezoelectric stress wave signal transmitted by the pipe thread connection, converts the piezoelectric stress wave signal into an electric signal, transmits the electric signal to the input end of the NI signal acquisition card 6 through the BNC cable 5, and the NI signal acquisition card 6 converts the electric signal output by the piezoelectric ceramic sensor 4 into a digital signal and then transmits the digital signal to the computer analysis terminal 8 through the USB cable 7;
under the condition that the normal sealing working state of the pipe thread is defined in a computer analysis system, a measured signal received by a piezoelectric ceramic sensor 4 serving as a receiver is used as a reference signal, an identification characteristic parameter reference value is constructed, then the identification characteristic parameter of the pipe thread connection measuring signal in different periods is monitored, the identification characteristic parameter and the identification characteristic parameter reference value are compared and analyzed, a loosening judgment index is calculated, and the sealing condition of the pipe thread joint is obtained by monitoring the change of the judgment index. The larger the defined loosening judgment index is, the larger the deviation of the working condition of the threaded connection of the pipe to be detected from the normal sealing state is.
For example, let the energy value of the signal received by the piezoceramic sensor 4 be E, which can be expressed as
Wherein, tsAnd tfSub-tables representing the initial and end times of the received signal, y (t) and fsRespectively representing discrete sample values and a sampling frequency of the received signal.
In this case, the relative change rate R of the received signal energy value, which is an indicator for judging the loosening of the pipe thread, is calculated by the following equation:
wherein E istRepresenting measured signal energy values of the structure, E0The signal energy value which represents the healthy and sealed state of the structure is a reference value. The signal energy value E in the above formula (2) can also be replaced by a wavelet packet energy value and a structure local resonance frequency.
For the wavelet packet node coefficient r of the piezoelectric sensor receiving signal, the looseness evaluation index can be calculated by the variation Relative Mean Square Deviation (RMSD) of the wavelet node coefficient r:
wherein r isiCoefficient of i-th wavelet packet node, r, representing structure measured signali 0And the ith wavelet packet node coefficient of the test signal in the structural health and sealing state is represented, and N represents the number of the wavelet packet node coefficients. The wavelet packet node coefficient r in the formula (3) can also be replaced by a signal fitting regression coefficient and a factor analysis coefficient.
The basic principle of the invention is that two threaded pipes 1 are in threaded connection through a threaded joint 2, when the pipe threads are loosened and leaked, the threaded contact area of the threaded pipes 1 and the threaded joint 2 changes along with the change, the more serious the loosening is, the larger the change of the threaded contact area is compared with the change of a sealing state is, the larger the piezoelectric stress wave excitation signal generated by a piezoelectric ceramic sensor 3 serving as a driver is transmitted and attenuated or changed through the threaded connection of the pipes is, meanwhile, the larger the change of the stress wave signal received by a piezoelectric ceramic sensor 4 serving as a receiver is, the loosening condition of the threaded connection of the pipes can be monitored by monitoring the change of the piezoelectric stress wave signal received by the piezoelectric ceramic sensor 4, and in addition, the loosening of the pipe threads is often accompanied by the relative torsion of the threaded pipes 1 and the threaded joint 2. Therefore, by monitoring and recognizing the changes in the relative positions and the thread contact areas of the threaded pipe 1 and the threaded joint 2 due to the loosening of the pipe threads, the occurrence of the loosening of the pipe threads can be identified, while to some extent, the severity of the occurrence of the loosening is evaluated.
A brief theoretical derivation is given here, and from the above analysis it is known that loosening of the pipe thread causes changes in the thread contact area and relative position of the threaded pipe 1 and the threaded joint 2, and therefore a brief theoretical derivation is given here from these two points, respectively.
(1) Loosening induced changes in pipe thread contact area
When the pipe thread loosens as shown in fig. 3In this case, assuming that the threaded joint 2 is held in a fixed position, the threaded pipe 1 is twisted in the loosening direction (here, in the counterclockwise direction) (see fig. 1), and the threaded contact area between the threaded pipe 1 and the threaded joint 2 is reduced. For a pipe thread, the contact area of the threaded pipe 1 with the threaded joint 2 decreases by Δ S for every counterclockwise rotation of the threaded pipe 10This value is determined at the time of shipment of the pipe thread and is dependent only on the geometric parameters of the pipe thread (thread diameter, profile angle, lead, etc.).
Assuming that the threaded pipe 1 is twisted counterclockwise theta when the pipe thread is loosened, the invention only considers the monitoring at the initial stage of the loosening, so the range of the twisting angle is 0 < theta ≦ pi. Then, in such a loose state, the change Δ S in the contact area of the pipe threads can be expressed as:
this formula can be expressed as:
Δ S ∞ θ (0 < θ ≦ π) formula (5)
That is, when the pipe thread is loosened, the amount of change in the thread contact area of the threaded pipe 1 and the threaded joint 2 is proportional to the rotation angle at which the threaded pipe 1 is twisted in the loosening direction.
(2) Loosening induced changes in relative position of pipe threads
According to the embodiment of the present invention described above, the piezoelectric ceramic sensor 4 as a receiver is attached to the surface of the threaded pipe 1, and the piezoelectric ceramic sensor 3 as an actuator is attached to the surface of the threaded joint 2. In the sealed state of the pipe thread, the two sensors 3 and 4 are aligned along the length of the threaded pipe 1, as shown in FIG. 4, and have an initial relative distance L0. When the pipe thread loosens, namely the threaded pipe 1 rotates theta along the counterclockwise direction, the position of the piezoelectric ceramic sensor 3 is kept unchanged, and the piezoelectric ceramic sensor 4 rotates theta along with the threaded pipe 1, and the final position is shown in fig. 4.
Assuming that the threaded pipe 1 rotates once in the counterclockwise direction, it follows the length of the threaded pipe 1Twisted outwards by a length Δ l0This value is determined at the time of production of the pipe thread, and is likewise dependent only on the geometric parameters of the pipe thread (thread diameter, profile angle, lead, etc.). When the threaded pipe 1 is rotated counterclockwise by θ, the threaded pipe 1 is twisted outward in the length direction by a length Δ l, which can be expressed as:
at the same time, as the threaded pipe 1 rotates, the piezoceramic sensor 4 is also displaced along the circumferential direction of the threaded pipe 1. Assuming that the radius of the threaded pipe 1 is R, when it is rotated counterclockwise by θ, the amount of positional change of the piezoceramic sensor 4 in the circumferential direction of the threaded pipe 1 is θ R. As shown in fig. 4, the relative distance L between the two piezoceramic sensors 3, 4 in the loose state at this time can be expressed as:
therefore, when the pipe thread is loosened, the relative positional change amount Δ L of the two piezoelectric ceramic sensors 3, 4 can be expressed as:
the above formula (8) can also be expressed as:
delta L ^ theta (0 < theta ≦ pi) formula (9)
That is, when the thread of the pipe is loosened, the relative position change amount of the piezoelectric ceramic sensor 3 adhered to the surface of the threaded joint 2 and the piezoelectric ceramic sensor 4 adhered to the surface of the threaded pipe 1 has a positive correlation with the rotation angle of the threaded pipe 1 twisted in the loosening direction.
In summary, when the pipe thread loosens, the thread contact area of the threaded pipe 1 and the threaded joint 2 decreases, and the relative positions of the two piezoceramic sensors 3 and 4 also increase. The propagation rule of piezoelectric stress wave signals generated by the piezoelectric ceramic sensor in the structure is known, the energy attenuation degree of the received signals is inversely proportional to the contact area between the structures, the larger the contact area is, the smaller the attenuation of the stress waves after the stress waves are propagated through the contact surface is, namely, the received energy is larger, and conversely, the contact area is reduced, so the received energy is also reduced. Meanwhile, the relative distance between the signal receiving position and the signal source is also directly related to the energy attenuation degree of the received signal, and the closer the receiver is to the signal source, the larger the received energy is, and the smaller the received energy is otherwise. Therefore, by monitoring the attenuation degree of the energy propagation of the piezoelectric stress wave signal in the pipe threaded connection, the change of the thread contact area and the relative position of the threaded pipe 1 and the threaded joint 2 can be indirectly reflected. When the pipe thread is not changed, the pipe thread is indicated to be well sealed, no loosening leakage occurs, otherwise, the pipe thread is indicated to be loosened, and therefore the monitoring and discrimination of the sealing state of the pipe thread connection are achieved. The method provided by the invention has the advantages of simple principle and easy operation, and can accurately monitor and identify the tiny loosening change of the pipe thread in real time.
When the pipe thread connection is loosened, the relative position between the threaded pipe and the threaded joint and the thread contact area are changed, meanwhile, the energy attenuation degree of a piezoelectric stress wave signal passing through an actual contact surface in the structure propagation process is inversely proportional to the contact area and is in direct proportion to the relative distance between the receiver and a signal source, and the monitoring and the identification of the pipe thread sealing state can be simply and efficiently realized by comparing the energy of the actually received signal with the relative size of a reference value in the pipe thread sealing state, so that the safety of the pipe thread connection is improved, the potential safety hazard and the operation risk are reduced, the overall economic benefit is improved, and the positive significance is generated.
Claims (7)
1. A method of monitoring loosening of a threaded joint for pipes, the method comprising the steps of:
fixing two piezoelectric ceramic sensors on the surfaces of a threaded joint and a threaded pipe in a surface pasting mode respectively, and performing waterproof insulation treatment on the surfaces of the piezoelectric ceramic sensors;
connecting the two piezoelectric ceramic sensors to a data acquisition card through cables respectively, and then connecting the data acquisition card with a computer analysis terminal;
step three, the computer analysis terminal controls the data acquisition card to generate an excitation electric signal with a certain frequency band through a cable, the excitation electric signal is output through the output end of the data acquisition card and is transmitted to the piezoelectric ceramic sensor serving as a driver through the cable, the excitation electric signal drives the piezoelectric ceramic sensor to generate mechanical vibration, a piezoelectric stress wave is formed in the threaded connection of the pipes and is transmitted along the direction of the pipeline; the other piezoelectric ceramic sensor is used as a receiver, receives piezoelectric stress wave signals transmitted through pipe threaded connection and converts the piezoelectric stress wave signals into electric signals, the electric signals are transmitted to the input end of a data acquisition card through a cable, and the data acquisition card converts the electric signals output by the piezoelectric ceramic sensor used as the receiver into digital signals and transmits the digital signals to a computer analysis terminal;
step four, defining a normal sealing working state of the pipe thread in a computer analysis system, using a signal measured by a piezoelectric ceramic sensor as a receiver as a reference signal, constructing a recognition characteristic parameter reference value, then monitoring recognition characteristic parameters of pipe thread connection measurement signals in different periods in a subsequent service state, comparing and analyzing the recognition characteristic parameters with the recognition characteristic parameter reference value, calculating a loosening judgment index of the pipe thread joint, and obtaining the sealing condition of the pipe thread joint by monitoring the change of the judgment index;
the loosening judgment index comprises a relative change value and/or a change relative mean square error of the signal characteristic value of the identification characteristic parameter, and the larger the defined loosening judgment index is, the more obvious the difference of the service state of the tested pipe threaded joint from the normal sealing state is, namely the larger the possibility of loosening and leakage is, the more serious the loosening disease is;
when a piezoelectric stress wave excitation signal generated by a piezoelectric ceramic sensor serving as a driver is transmitted and attenuated or changed more greatly through pipe thread connection, and meanwhile, the stress wave signal received by the piezoelectric ceramic sensor serving as a receiver is changed more greatly, the pipe thread connection loosening condition can be monitored by monitoring the piezoelectric stress wave signal change received by the piezoelectric ceramic sensor, the pipe thread loosening is that the threaded pipe and the threaded joint are twisted relatively, the occurrence of the pipe thread loosening can be identified by monitoring and identifying the change of the relative position and the thread contact area of the threaded pipe and the threaded joint caused by the pipe thread loosening, and the severity of the loosening is evaluated; the relative position of the threaded pipe and the threaded joint and the change in the thread contact area versus the relative twist angle are as follows:
loosening induced changes in pipe thread contact area
When the pipe thread loosens, if the threaded joint keeps fixed position, the threaded pipe twists along the loosening direction, and the contact area of the threaded pipe and the threaded joint is reduced; for a pipe thread, the contact area of the threaded pipe with the threaded joint is reduced by deltas for each revolution of the threaded pipe in the counter-clockwise direction0The value is determined when the pipe thread leaves a factory;
when the pipe thread is loosened, the threaded pipe is twisted counterclockwise theta, and only the monitoring of the initial loosening stage is considered, so that the range of the twisting angle is 0 & lt theta & lt pi; then, in such a loose state, the change Δ S in the contact area of the pipe threads is expressed as:
equation (4) is expressed as:
Δ S ∞ θ (0 < θ ≦ π) formula (5)
When the pipe thread is loosened, the change quantity of the thread contact area of the threaded pipe and the threaded joint is in direct proportion to the turning angle of the threaded pipe twisted along the loosening direction;
loosening induced changes in relative position of pipe threads
Sticking a piezoelectric ceramic sensor as a receiver on the surface of the threaded pipe, and sticking a piezoelectric ceramic sensor as a driver on the surface of the threaded joint; in the state of sealing the pipe thread, the two sensors are positioned on the same straight line along the length direction of the threaded pipe, and the initial relative distance is L0(ii) a When the pipe thread loosens, namely the threaded pipe rotates theta along the counterclockwise direction, the position of the piezoelectric ceramic sensor on the surface of the threaded joint is kept unchanged, and the piezoelectric ceramic sensor on the surface of the threaded pipe rotates theta along with the threaded pipe;
assuming that the threaded pipe is twisted outwards along the length direction of the threaded pipe by a length delta l every time the threaded pipe rotates by one circle along the counterclockwise direction0(ii) a Then when the threaded pipe is rotated counterclockwise by θ, the threaded pipe is twisted outward in the length direction by a length Δ l, which is expressed as:
meanwhile, along with the rotation of the threaded pipe, the position of the piezoelectric ceramic sensor is also changed along the circumferential direction of the threaded pipe; if the radius of the threaded pipe is R, when the threaded pipe rotates anticlockwise theta, the position change quantity of the piezoelectric ceramic sensor along the circumferential direction of the threaded pipe is theta R; the relative distance L of the two piezoceramic sensors in the loose state is represented as follows:
therefore, when the pipe thread is loosened, the relative position change amount Δ L of the two piezoelectric ceramic sensors is expressed as:
the above formula (8) is expressed as:
delta L ^ theta (0 < theta ≦ pi) formula (9)
When the pipe thread is loosened, the relative position change quantity of the piezoelectric ceramic sensor adhered to the surface of the threaded joint and the piezoelectric ceramic sensor adhered to the surface of the threaded pipe is in positive correlation with the rotation angle of the threaded pipe twisted along the loosening direction.
2. A monitoring method for loosening of a threaded joint for pipes according to claim 1, characterized in that: and in the fourth step, the pipe thread is used as a reference signal of a piezoelectric ceramic sensor of the receiver in a normal sealing working state, and a collected signal at the initial stage of putting into use after the pipe thread is installed is taken, or a signal collected by an experiment is carried out when the pipe thread is confirmed not to be loosened and leaked by a detection method in the prior art.
3. A monitoring method for loosening of a threaded joint for pipes according to claim 1 or 2, characterized in that: in step four, the characteristic parameter is identified as a direct measurement value or a derivative value that can characterize the signal characteristic.
4. A monitoring method for loosening of a threaded joint for pipes according to claim 3, characterized in that: the identification characteristic parameters comprise one or any combination of energy amplitude of received signals, wavelet packet energy value, structure local resonance frequency, signal fitting regression coefficient, factor analysis coefficient and wavelet packet node coefficient.
5. A monitoring method for loosening of a threaded joint for pipes according to claim 1, characterized in that: in the first step, epoxy resin is uniformly coated on the surface of the piezoelectric ceramic sensor, and waterproof insulation treatment is carried out.
6. A monitoring method for loosening of a threaded joint for pipes according to claim 1, characterized in that: the data acquisition card is an NI signal acquisition card, the NI signal acquisition card is respectively connected with the two piezoelectric ceramic sensors through a BNC cable, and the NI signal acquisition card is connected with the computer analysis terminal through a USB cable.
7. A monitoring method for loosening of a threaded joint for pipes according to claim 1, characterized in that: and the computer analysis terminal generates an excitation electric signal through the data acquisition card, wherein the excitation electric signal is a sine sweep frequency excitation electric signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810108140.9A CN108120574B (en) | 2018-02-02 | 2018-02-02 | Method for monitoring looseness of pipe threaded joint |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810108140.9A CN108120574B (en) | 2018-02-02 | 2018-02-02 | Method for monitoring looseness of pipe threaded joint |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108120574A CN108120574A (en) | 2018-06-05 |
| CN108120574B true CN108120574B (en) | 2022-05-13 |
Family
ID=62233716
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810108140.9A Active CN108120574B (en) | 2018-02-02 | 2018-02-02 | Method for monitoring looseness of pipe threaded joint |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108120574B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR102164817B1 (en) * | 2019-12-05 | 2020-10-13 | 주식회사 나노켐 | Separation inspecting apparatus for flue |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106909733A (en) * | 2017-02-23 | 2017-06-30 | 长沙理工大学 | A kind of steel truss bridge key member high-strength bolt health status monitoring method |
-
2018
- 2018-02-02 CN CN201810108140.9A patent/CN108120574B/en active Active
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106909733A (en) * | 2017-02-23 | 2017-06-30 | 长沙理工大学 | A kind of steel truss bridge key member high-strength bolt health status monitoring method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN108120574A (en) | 2018-06-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108181064B (en) | Pipe thread loosening monitoring method based on piezoelectric impedance method | |
| US10578503B2 (en) | System and methods for strain detection in a coupling | |
| US10472947B2 (en) | Deformation measurement method and apparatus | |
| US7698949B2 (en) | Active washers for monitoring bolted joints | |
| US9030206B2 (en) | Method and apparatus for characterizing process control equipment coupling integrity | |
| CN109520666B (en) | Nondestructive monitoring method for pressure inside pipeline | |
| CN108981988A (en) | A kind of clip loosening detection device and detection method based on optical fiber grating sensing | |
| CN102121860A (en) | Corrugated diaphragm type pipe external pressure sensor, oil-water well casing external pressure monitoring device and method | |
| CN108120574B (en) | Method for monitoring looseness of pipe threaded joint | |
| KR20110108484A (en) | Measurement method and system for the torsion of the structure using strain sensors | |
| CN106706241A (en) | Initiative self-checking device and method for wind turbine blade damage | |
| CN103411713B (en) | Wide range is based on the reinforcing steel corrosion monitoring sensor of fiber grating sensing technology | |
| CN110954259A (en) | Gasket sensor based on optical fiber microbend loss | |
| CN207779647U (en) | A kind of monitoring device loosened for pipe screw joint | |
| CN109239189A (en) | High-temperature pipe supersonic guide-wave based on functionally graded material monitors system and method | |
| CN206369617U (en) | A kind of pneumatic equipment bladess damage active self-checking unit | |
| CN103499458A (en) | Variable-scale-distance test method for damage representation of engineering structure | |
| CN207779648U (en) | A kind of pipe screw thread loosening monitoring device based on Piezoelectric Impedance method | |
| CN215110827U (en) | Electric valve and torque and stroke measuring system of actuator thereof | |
| CN206563625U (en) | A kind of built-in cable tension sensor | |
| Wu et al. | Electromechanical impedance instrumented wearable piezoelectric ring-type sensor for bolted connection monitoring | |
| CN215952838U (en) | Calibration device | |
| CN112683957A (en) | Engineering structure health monitoring device and method | |
| CN112781775A (en) | Calibration device and method for torque and stroke measurement system of valve and actuator thereof | |
| CN111998916A (en) | Oil conservator oil level measuring device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |