CN113236985A

CN113236985A - Fluid pipeline leakage online monitoring and positioning device and control method thereof

Info

Publication number: CN113236985A
Application number: CN202110651326.0A
Authority: CN
Inventors: 白光; 白永强; 姚伟; 张晓峰; 吕良海; 汪彤; 汤仁锋; 吴习驹; 尤雅楠; 肖志诚
Original assignee: Beijing Municipal Institute of Labour Protection
Current assignee: Beijing Municipal Institute of Labour Protection
Priority date: 2021-06-11
Filing date: 2021-06-11
Publication date: 2021-08-10
Anticipated expiration: 2041-06-11
Also published as: CN113236985B

Abstract

An online monitoring and positioning device for fluid pipeline leakage comprises a computer, a data acquisition card and a monitoring device, wherein the monitoring device is arranged on a fluid pipeline divided into a plurality of continuous straight pipe sections through a flange plate, the monitoring device is connected with the data acquisition card, and the data acquisition card is connected with the computer; the fluid pipeline leakage on-line monitoring and positioning control method is based on the fluid pipeline leakage on-line monitoring and positioning device. A device for monitoring and positioning leakage of fluid pipeline on line and a control method thereof are used for monitoring and positioning leakage of single straight pipe section pipeline, a plurality of continuous straight pipe sections and branch pipe sections on line, judging the severity of leakage, and identifying and eliminating pressure fluctuation interference caused by business operation.

Description

Fluid pipeline leakage online monitoring and positioning device and control method thereof

Technical Field

The invention relates to the technical field of signal monitoring and analysis, in particular to an online monitoring device and a control method thereof, and particularly relates to an online monitoring and positioning device for fluid pipeline leakage and a control method thereof.

Background

With the rapid promotion of urbanization in China and the improvement of the living standard of people, pipeline transportation of water, gas, heat, oil and the like is widely applied to various fields of national economy. However, with the increase of service life, the service life of the pipe is longer and longer, and the pipeline often leaks due to corrosion, weld defects, vibration, abrasion, external force damage and the like, so that the normal operation of the pipeline is influenced, and huge potential threats are caused to production safety, social stability, soil, environment, ecology and the like. Therefore, the pipeline leakage is monitored on line in real time, the leakage is found in time and is accurately positioned, and the method is very important for eliminating the potential safety hazard of the pipeline.

However, when the existing pipeline leaks, the leakage point is mostly searched along the line in a manual mode, the experience of leakage detection personnel is emphasized, the accuracy is low, and time and labor are consumed.

Therefore, the problems of the prior art are to be further improved and developed.

Disclosure of Invention

The object of the invention is: in order to solve the problems in the prior art, an object of the present invention is to provide a device and a control method thereof, which can monitor whether a fluid pipeline leaks, and when the fluid pipeline leaks, can quickly and accurately determine the position of the cross section of the pipeline where the leakage point of the pipeline is located, determine the approximate position of the leakage point on the cross section of the pipeline, and calculate the amount of leakage caused by the leakage.

The technical scheme is as follows: in order to solve the technical problems, the technical scheme provides an online monitoring and positioning device for fluid pipeline leakage, which comprises a computer, a data acquisition card and a monitoring device, wherein the monitoring device is arranged on a fluid pipeline divided into a plurality of continuous straight pipe sections through a flange plate, the monitoring device is connected with the data acquisition card, and the data acquisition card is connected with the computer;

the computer is preset with an instantaneous pressure drop threshold value at each monitoring point on the straight pipe section, a time interval threshold value for detecting the negative pressure wave in sequence and a flow velocity fluctuation threshold value;

the monitoring device converts deformation change of the resistance strain gauge group caused by front-back pressure difference and fluid impact into an electric signal to be output, the electric signal is transmitted to the computer through the data acquisition card, the computer judges the leakage position of the fluid pipeline according to the one-to-one correspondence relationship between the electric signal and pressure and fluid flow rate, calculates the leakage amount, sends out a leakage alarm and outputs a leakage report.

Preferably, the data acquisition card transmits the acquired electrical signals to a computer, and the computer obtains a continuous pressure oscillogram and a continuous flow velocity oscillogram in the pipeline at each monitoring device according to the electrical signals acquired by the data acquisition card.

Preferably, three monitoring devices are respectively installed on each divided straight pipe section and are respectively installed at end points and a midpoint of two sides of each straight pipe section.

Preferably, the monitoring device comprises a protective shell, a single chip microcomputer and a resistance strain gauge set, wherein the resistance strain gauge is used for detecting the pressure difference between the front and the back of the fluid pipeline and the deformation change caused by the impact of the fluid, and the single chip microcomputer converts the real-time deformation change of the resistance strain gauge into an electric signal;

the single chip microcomputer and the resistance strain gauge group are arranged in an inner cavity of the protective shell, the resistance strain gauge is connected with the single chip microcomputer through a lead, and the single chip microcomputer is connected with the data acquisition card.

Preferably, the resistance strain gauge groups comprise four groups, the resistance strain gauge groups are respectively arranged in four clamps, and the four clamps are of arc structures with the same radius and the radian of 90 degrees;

the resistance strain gauge group consists of a plurality of same resistance strain gauges, and each resistance strain gauge is connected with the single chip microcomputer through a lead.

Preferably, the arc-shaped inner circle of the fixture is open and provided with a clamping groove, and the clamping groove is used for fixing the resistance strain gauge of the resistance strain gauge set.

Preferably, the protective housing is of an annular structure with an inner cavity, a gap is reserved on the circumference of the inner circle of the protective housing, the resistance strain gauge group is arranged at the gap of the circumference of the inner circle of the protective housing, a single chip microcomputer protective housing is arranged at the top of the circumference of the outer circle of the protective housing, and the single chip microcomputer is fixed in the single chip microcomputer protective housing.

Preferably, the monitoring device further comprises a position control rod, the position control rod is used for controlling the resistance strain gauge set and the fixture to be in a working position/a non-working position, the position control rod is connected with the fixture, and one end, far away from the fixture, of the position control rod protrudes out of the protective shell.

Preferably, the side wall of the protective shell is provided with a flange connecting hole, and the flange connecting hole is used for connecting the monitoring device and the fluid pipeline through a flange plate.

A fluid pipeline leakage on-line monitoring and positioning control method is a control method for carrying out fluid pipeline leakage on-line monitoring and positioning based on a fluid pipeline leakage on-line monitoring and positioning device, and specifically comprises the following steps:

the method comprises the following steps: dividing the fluid pipeline into a plurality of continuous straight pipe sections, and respectively setting monitoring points for the divided straight pipe sections;

step two: presetting an instantaneous pressure drop threshold value, a time interval threshold value for detecting a negative pressure wave successively and a flow velocity fluctuation threshold value at each monitoring point on the straight pipe section;

step three: the monitoring device collects negative pressure waves of each monitoring point of the straight pipe section in real time;

step four: comparing the instantaneous pressure drop value collected at each monitoring point of the straight pipe section and the time interval of successively detecting the negative pressure wave with the corresponding preset threshold values in the step two respectively, judging whether an effective negative pressure wave is detected, if so, performing the step five, and if not, returning to the step three;

step five: the effective negative pressure wave in the fourth step is firstly detected by one monitoring point on the straight pipe section, the time interval of the negative pressure wave detected by the other two monitoring points is compared, and whether the fluid pipeline leaks or not is judged; if the fluid pipeline leaks, performing the step six, and if the fluid pipeline does not leak, returning to the step three;

step six: the computer judges the leakage position, calculates the leakage amount, sends out a leakage alarm and outputs a leakage report.

Preferably, the first step further includes setting monitoring devices at monitoring points of each divided straight pipeline, where the monitoring devices are connected to a data acquisition card, and the data acquisition card transmits acquired electrical signals to a computer to obtain continuous pressure oscillograms and flow velocity oscillograms in the pipeline at each monitoring device.

Preferably, the monitoring points arranged on each straight pipe section divided in the step one include three monitoring points which are respectively the end points and the middle points on two sides of each divided straight pipe section.

Preferably, the fourth step specifically includes determining that an effective negative pressure wave is detected if the instantaneous pressure drop value collected at each monitoring point of the straight pipe section is not less than the preset instantaneous pressure drop value threshold value and the time interval of successively detecting negative pressure waves is not greater than the preset time interval threshold value, and determining that an effective negative pressure wave is not detected if the time interval of successively detecting negative pressure waves is not greater than the preset time interval threshold value.

Preferably, the step five of judging whether the fluid pipeline leaks specifically includes:

if the other two monitoring points of the effective negative pressure wave straight pipe section detect that the time intervals of the effective negative pressure waves in the step five are different in sequence, judging that the straight pipe section leaks;

if the effective negative pressure wave straight pipe section is detected, the monitoring point at the end point of the upstream side detects the effective negative pressure wave in the fourth step firstly, and if the monitoring point at the middle point and the monitoring point at the other end point detect the negative pressure wave at the same time interval in sequence, the negative pressure wave is judged not to be generated by the leakage of the straight pipe section; if one end of a monitoring point on the straight pipe section, which detects the negative pressure wave firstly, is connected with a fluid supply source or a user or a pressure regulating device, the negative pressure wave can be judged to be caused by service operation;

when the monitoring points on each side of the subsection node of the adjacent straight pipe section simultaneously detect the effective negative pressure wave in the fifth step, and the other two monitoring points on the adjacent straight pipe section respectively detect the negative pressure wave at the same time interval in sequence, judging that the leakage point is at the subsection node;

preferably, the determining the leakage position and calculating the leakage amount in the sixth step specifically include:

this straight tube section appears leaking: calculating the distance between a leakage point and a monitoring point for detecting the negative pressure wave firstly according to a leakage point positioning formula, further determining the position of the cross section of the pipeline where the leakage point is positioned, judging the approximate position of the leakage point on the cross section of the pipeline by detecting the position of a resistance strain gage of the negative pressure wave firstly, calculating leakage quantity through fully developed flow velocity oscillograms (namely the flow velocity fluctuation value is not more than a preset flow velocity fluctuation threshold value) of two monitoring points at the upper and lower parts of the leakage point, a flow calculation formula and a continuity equation, and judging the severity of the leakage;

if the negative pressure wave is caused by service operation, the computer does not send out a leakage alarm;

leakage points at segment nodes: the position of the resistance strain gauge of the negative pressure wave is detected firstly, the approximate position of the leakage point on the cross section of the pipeline can be judged, the leakage amount is calculated through a flow velocity oscillogram (namely the flow velocity fluctuation value is not more than a preset flow velocity fluctuation threshold value), a flow calculation formula and a continuity equation which are fully developed at the monitoring point on each side of the segmented node, and the severity of the leakage can be judged.

Preferably, in the sixth step, the content of the leakage report output by the computer includes the position of the cross section of the pipeline where the leakage point is located, the approximate orientation of the leakage point on the cross section of the pipeline, and the leakage amount generated by the leakage.

(III) the beneficial effects are as follows: the invention provides a fluid pipeline leakage on-line monitoring and positioning device and a control method thereof, which are used for on-line monitoring and positioning of leakage of a single straight pipe section pipeline, a plurality of continuous straight pipe sections and a branch pipe section, judging the severity of leakage, and identifying and eliminating pressure fluctuation interference caused by business operation.

Drawings

FIG. 1 is a schematic view of a cross-sectional structure of a resistance strain gage set and a fixture in a working position of the monitoring device of the present invention;

FIG. 2 is a schematic view of a section structure of a resistance strain gauge set and a fixture in a non-working position of the monitoring device of the present invention;

FIG. 3 is a schematic view of a first partial cross-sectional structure of the monitoring device of the present invention;

FIG. 4 is a second partial top view (of the interface with the first portion) of the monitoring device of the present invention;

FIG. 5 is a view showing the arc-shaped inner circumference of the clamp of the monitoring device of the present invention;

FIG. 6 is a schematic view of a position control lever of the monitoring device of the present invention;

FIG. 7 is a schematic view of a first embodiment of the present invention;

FIG. 8 is a schematic view of a second embodiment of the present invention;

100-a monitoring device; 101-flange attachment hole; 102-a single chip microcomputer; 103-a gap; 104-a sealing strip; 110-a first portion; 111-a first bolt securing post; 120-a second portion; 121-a second bolt fixing column; 130-single chip protective shell; 141-a first set of resistive strain gauges; 142-a second set of resistive strain gauges; 143-a third resistive strain gage group; 144-a fourth set of resistive strain gauges; 150-position control lever; 151-connecting spring; 152-control button; 1521-control button housing; 1522-tabletting springs; 1523 tabletting; 1524-control press rod; 1525 fixing the working position; 1526-non-working position fixing rod; 160-a fixture; 161-card slot; 162-threading hole; 18-a computer; 19-data acquisition card.

Detailed Description

The present invention will be described in further detail with reference to preferred embodiments, and more details are set forth in the following description in order to provide a thorough understanding of the present invention, but it is apparent that the present invention can be embodied in many other forms different from the description herein and can be similarly generalized and deduced by those skilled in the art based on the practical application without departing from the spirit of the present invention, and therefore, the scope of the present invention should not be limited by the contents of this detailed embodiment.

The drawings are schematic representations of embodiments of the invention, and it is noted that the drawings are intended only as examples and are not drawn to scale and should not be construed as limiting the true scope of the invention.

When the fluid pipeline leaks, the fluid medium is quickly lost from a leakage point under the action of the pressure difference between the inside and the outside of the pipeline, and the fluid density at the leakage part is reduced due to the loss of the fluid medium at the leakage part, so that an instant pressure drop is generated. Due to the continuity of the fluid, the velocity of the fluid in the pipe does not change immediately, but the pressure of the fluid between the leak and the adjacent area is different, which causes the high pressure fluid in the area on both sides of the leak to flow to the low pressure area at the leak, which in turn causes the density and pressure of the fluid in the area adjacent to the leak to decrease. This phenomenon is transmitted in the upstream and downstream directions of the pipeline in sequence, and transient negative pressure waves are generated and propagate from the leakage point to the upstream and downstream along the pipeline and the medium respectively. The negative pressure wave propagates up and down the pipe and the medium, and the instantaneous pressure drop has almost vertical edges.

Based on the strain effect of the resistance strain gauge, the measurement sensitivity and the measurement precision of the resistance strain gauge are high (the minimum strain reading is 1 mu epsilon), the measurement range is wide (1-20000 mu epsilon can be measured), the frequency response is good (the dynamic strain from static state to hundreds of thousands of hertz can be measured), the size of the strain gauge is small, the weight is light (the grid length of the minimum strain gauge can be as short as 0.1 mm), the strain gauge can be used for measuring in various complex environments (such as environment measurement of high temperature, low temperature, high-speed rotation, strong magnetic field and the like), the micro strain generated by the pressure difference between the front and the back of the strain gauge caused by negative pressure waves and the deformation change caused by fluid impact can be effectively captured, and the strain gauge can be converted into an electric signal to be output. Because of the continuity of the fluid, the speed change of the fluid in the pipeline caused by leakage lags behind the pressure change, and the existence of the time difference enables the same group of resistance strain gauges to capture the transient pressure drop and the average flow speed of the cross section after leakage. Based on the propagation directionality of negative pressure waves generated by leakage, the resistance strain gauge groups are arranged along the circumference of the pipeline, the approximate position of a leakage point on the cross section of the pipeline can be judged according to the position of the resistance strain gauge which firstly captures transient pressure drop, and the severity of leakage can be judged according to the change of the flow rate of the cross section before and after leakage.

The fluid pipeline is divided into continuous straight pipe sections according to a certain principle, so that the propagation speeds of pressure waves are kept consistent in the same straight pipe section, and monitoring devices are arranged at two end points and a middle point of the straight pipe section to capture instantaneous negative pressure wave signals. The leakage positions are different, the propagation distances of the negative pressure waves to upstream and downstream are different, the time of reaching each monitoring point is different, and the positions of the leakage points can be determined according to the time difference of reaching each monitoring point. When the leakage monitoring device normally operates, the pressure in the fluid pipeline is in a fluctuation state, and negative pressure waves can be generated in normal business operations such as pump adjustment, valve adjustment or user taking, so that how to effectively identify the negative pressure waves generated by leakage is the core and difficulty of leakage monitoring and positioning.

There are many methods for identifying negative pressure waves, including correlation analysis, residual analysis, time series analysis, wavelet analysis, and the like. The wavelet analysis method is based on wavelet transform principle, and uses wavelet analysis tool to transform signal, and makes multi-scale analysis on signal. The wavelet transformation can carry out multilayer decomposition and multi-scale analysis on signals in a time domain-frequency domain, has good capability of observing local characteristics of the signals in the time domain and the frequency domain, and can observe pipeline pressure change in detail and highlight abrupt change points (pressure falling edges), so that the wavelet transformation has obvious superiority in negative pressure wave signal processing.

An on-line monitoring and positioning device for fluid pipeline leakage comprises a computer, a data acquisition card and a monitoring device. The monitoring device comprises a protective shell, a single chip microcomputer and a resistance strain gauge group, wherein each resistance strain gauge in the resistance strain gauge group is connected with the single chip microcomputer through a lead, the single chip microcomputer is connected with a data acquisition card, and the data acquisition card is connected with a computer.

The single chip microcomputer and the data acquisition card can be transmitted in a wired mode, and at the moment, the data acquisition card is arranged in regions; the data transmission can also be carried out in a wireless mode, at the moment, the single chip microcomputer comprises a wireless communication module and is used for sending data information monitored by the single chip microcomputer to the data acquisition card, and the data acquisition card comprises a communication unit and is used for receiving monitoring data sent by the wireless communication unit and sending the data information acquired by the data acquisition card to the computer. It should be noted that, when the single chip microcomputer and the data acquisition card transmit data in a wired manner, the communication unit of the data acquisition card is configured to send data information acquired by the data acquisition card to the computer.

The monitoring device converts deformation change of the resistance strain gauge group caused by front-back pressure difference and fluid impact into electric signals to be output, the electric signals are transmitted to the computer through the data acquisition card, and the computer obtains continuous pressure oscillograms and flow velocity oscillograms at monitoring points according to the one-to-one correspondence relationship between the electric signals and pressure and fluid flow velocity.

The computer and the data acquisition card are peripheral equipment, and the monitoring device is connected with two end points and a middle point of the straight pipe section of the fluid pipeline through flange connection holes arranged on the protective shell by using flange plates.

The computer preferably adopts an industrial computer, and the data output by the single chip microcomputer in the protective shell is read by the data acquisition card for analysis and storage, and a leakage report is output and displayed.

The resistance strain gauge group is composed of a plurality of resistance strain gauges with the same size and structure and used for detecting the change of fluid pressure and flow velocity in the fluid pipeline and converting the change of the fluid pressure and flow velocity in the pipeline into resistance change; the single chip microcomputer converts the resistance change of the resistance strain gauge group into fluid pressure or flow velocity data in the pipeline; the computer determines the position of fluid leakage and the amount of fluid leakage in the fluid pipeline according to the pressure or flow rate data of the fluid in the pipeline. The resistance strain gauge comprises a metal resistance strain gauge and a semiconductor strain gauge, and the metal resistance strain gauge comprises a wire-shaped strain gauge and a metal foil-shaped strain gauge.

The resistance strain gauge is a sensitive device for converting strain change on a measured piece into an electric signal, and is one of main components of a piezoresistive strain sensor. The resistance strain gauge comprises a metal resistance strain gauge and a semiconductor strain gauge. The metal resistance strain gauge comprises a wire-shaped strain gauge and a metal foil-shaped strain gauge. The metal resistance strain foil is that the strain foil is tightly adhered on the base body which generates mechanical strain through special adhesive, when the base body is stressed and changes in stress, the resistance strain foil also deforms together, so that the resistance value of the strain foil changes, and the voltage applied on the resistance strain foil changes.

The resistance strain gauge group comprises four groups: the device comprises a first resistance strain gauge group, a second resistance strain gauge group, a third resistance strain gauge group and a fourth resistance strain gauge group, wherein the four resistance strain gauge groups respectively form arc structures with the same radius by a plurality of resistance strain gauges, the radian of the arc structures of the four resistance strain gauge groups is ninety degrees, and when the four resistance strain gauge groups are positioned at a working position, the four resistance strain gauge groups form a circle.

As shown in fig. 1, 2 and 3, the protective casing of the monitoring device is composed of a first part and a second part, the first part and the second part form a circular ring structure with an inner cavity through bolts, and a gap is reserved along the inner circle circumference. The radian of the gap is 360 degrees, and a circle is formed on the inner ring wall of the protective shell of the whole circular ring structure. The joint of the first part and the second part is provided with a sealing gasket, when the first part and the second part are connected through a bolt, the sealing gasket arranged between the first part and the second part is compressed, and the sealing performance of the joint of the first part and the second part is ensured.

The adjacent outer circumferences of the first part and the second part are respectively provided with a first bolt fixing column, the first bolt fixing columns are respectively provided with a corresponding first bolt fixing hole, and a bolt penetrates through the first bolt fixing holes to fix the first part and the second part together to form a circular ring structure with an inner cavity.

The first part and the second part of the protective shell are respectively composed of two shells which are symmetrical to each other, such as: when two mutually symmetrical shells of the first part are spliced together, a semicircular ring structure with an inner cavity and a gap reserved along the circumference of an inner circle is formed; when the two mutually symmetrical shells of the second part are spliced together, a semicircular ring structure with an inner cavity and a gap reserved along the circumference of the inner circle is formed; when the semicircular ring structure formed by the first part and the semicircular ring structure formed by the second part are spliced, a circular ring structure which is provided with an inner cavity and a gap is reserved along the circumference of the inner circle is formed, as shown in fig. 4.

The two symmetrical shells of the first part are oppositely spliced, the adjacent edges of the arc peripheries of the two symmetrical shells of the first part are respectively provided with a second bolt fixing column, the second bolt fixing columns are respectively provided with a second bolt fixing hole correspondingly, and a bolt penetrates through the second bolt fixing holes to fix the two symmetrical shells of the first part together to form a semicircular ring structure with an inner cavity. When the two symmetrical shells of the first part are spliced, a sealing gasket is arranged at the circumferential joint of the peripheries of the two symmetrical shells, and when the two symmetrical shells of the first part are connected, the sealing gasket is compressed. When the two symmetrical shells of the first part are fixedly connected through the bolts, the sealing gaskets between the excircle circumferences of the two symmetrical shells of the first part are compressed, and the airtightness of the inner cavity of the protective shell is ensured. The second bolt fixing columns arranged on the two symmetrical shells of the first part can be two groups or four groups, and are not particularly limited herein, and it should be noted that the second bolt fixing columns are uniformly arranged on the arc peripheries of the two symmetrical shells.

The two symmetrical shells of the second part are oppositely spliced, the adjacent edges of the arc peripheries of the two symmetrical shells of the second part are respectively provided with a second bolt fixing column, the second bolt fixing columns are respectively provided with a second bolt fixing hole correspondingly, and a bolt penetrates through the second bolt fixing holes to fix the two symmetrical shells of the second part together to form a semicircular ring structure with an inner cavity. When the two symmetrical shells of the second part are spliced, a sealing gasket is arranged at the peripheral circumferential joint of the two symmetrical shells, and when the two symmetrical shells of the second part are connected, the sealing gasket is compressed. When the two symmetrical shells of the second part are fixedly connected through the bolts, the sealing gaskets between the excircle circumferences of the two symmetrical shells of the second part are compressed, and the tightness of the inner cavity of the protective shell is ensured. The second bolt fixing columns arranged on the two symmetrical shells of the second part can be two groups or four groups, and are not particularly limited herein, and it should be noted that the second bolt fixing columns are uniformly arranged on the arc peripheries of the two symmetrical shells.

The second bolt fixing columns arranged on the two symmetrical shells of the first part and the second bolt fixing columns arranged on the two symmetrical shells of the second part are optimally symmetrically arranged.

The inner cavity of the protective shell is provided with four groups of fixtures, the four groups of resistance strain gauge groups are respectively arranged in the fixtures, the fixtures are of arc structures matched with the resistance strain gauge groups, the fixtures are provided with clamping grooves, the clamping grooves are formed by a plurality of small clamping grooves, the sizes of the small clamping grooves are matched with the sizes of the resistance strain gauges, and the resistance strain gauges of the resistance strain gauge groups are sequentially arranged in the clamping grooves. The clamping groove is arranged along the arc-shaped middle line of the fixture, the resistance strain gauge is fixed with the fixture through the clamping groove, and the resistance strain gauge can be welded on the inner wall of the fixture, which is not limited specifically; the fixture is further provided with a threading hole along the arc to the center line, and the resistance strain gauge groups are connected with respective circuits through the threading holes, as shown in fig. 5. The thickness of the fixture is consistent with the wall thickness of the pipeline to be measured, when the fixture (the resistance strain gauge set) is in a working position, the fixture is flush with the inner wall and the outer wall of the pipeline, and two sides of the fixture are compressed and sealed by the sealing gaskets.

The resistance strain gauges are selected to have a dimension along the arc of the fixture that is larger than the aperture of the orifice so as to cover the cross section of the negative pressure wave propagation path caused by orifice leakage for determining the approximate orientation of the orifice at the cross section of the conduit, but are preferably not too large to reduce lateral effects. Preferably, the size of the resistance strain gauge (single resistance strain gauge) along the arc direction of the fixture is not less than 20mm or not less than 0.2 times of the diameter of the inner circle circumference of the protective shell, and the value is large.

When the selected resistance strain gauge is used for enabling the resistance strain gauge group and the fixture to be in a working position along the radial dimension of the fixture, the front end of the resistance strain gauge crosses the average flow speed position of the fluid in the pipeline when the flow speed is fully developed so as to detect the average flow speed of the cross section of the pipeline at the monitoring point after leakage occurs after the fluid flow speed is fully developed, but the average flow speed is not too large so as to reduce the influence on fluid flow. Preferably, the resistance strain gauge is not smaller than 0.125 times of the diameter of the inner circle circumference of the protective shell along the radial dimension of the fixture, and is not too large.

The transverse size of the resistance strain gauge is selected to be evenly and fully paved along the arc direction of the fixture.

The selected resistance strain gauge has good elasticity. The resistance strain gauges are sealed by high-temperature-resistant and corrosion-resistant rubber or plastic to block the resistance strain gauges from contacting with fluid in a pipeline to form a closed circuit, and meanwhile, each resistance strain gauge is guaranteed to be not conducted. The thickness of the rubber or plastic wrapped outside the resistance strain gauge is less than 1mm, the thinner the resistance strain gauge is, and the rubber or plastic wrapped outside the resistance strain gauge can be a protective film directly covering the surface of the resistance strain gauge or a protective sleeve, and the resistance strain gauge is not particularly limited.

The threading holes are formed in the positions, opposite to the arc-shaped outer walls of the fixtures, of the resistance strain gauges, after the wires penetrate through the threading holes, the resistance strain gauges are connected with the single chip microcomputer respectively, the arc-shaped inner walls of the fixtures are open, and when the resistance strain gauges are welded and fixed with the fixtures, the threading holes are filled and sealed through tin soldering. The arc-shaped open inner wall of the fixture is matched with the gap of the inner circle circumference of the protective shell, so that the resistance strain gauge group is arranged at the gap of the inner circle circumference of the protective shell when the resistance strain gauge group is in a working position.

The four groups of clamps are completely filled in a gap formed by assembling the protective shell along the circumference of the inner circle when combined, the inner surface and the outer surface of each clamp are flush with the inner surface and the outer surface of the gap, and the interface is tightly pressed and filled by a sealing strip.

The outer arc-shaped wall of the fixture is connected with a position control rod, and the position control rod is used for adjusting the resistance strain gauge group to be in a working position/a non-working position. The position control rod is fixed on one side of the fixture, which is far away from the inner circle circumference of the protective shell, and is positioned in the middle of the fixture, namely at the forty-five degree position of the fixture.

As shown in fig. 6, the position control rod includes a control button and a connection spring, the control button is a hollow cylindrical rod, the control button is fixedly connected with the fixture through the connection spring, one end of the connection spring is connected with the arc-shaped outer wall of the fixture, the other end of the connection spring is connected with the control button, the protection shell is provided with an opening, and one end, far away from the connection spring, of the control button protrudes out of the protection shell through the opening.

The control button comprises a control button shell, a pressing sheet spring, a pressing sheet, a control pressing rod, a working position fixing rod and a non-working position fixing rod. One end of the tablet spring is fixed on the inner wall of the side wall of the control button shell, the tablet spring is far away from one end of the control button shell and connected with the tablet, one side of the control button shell, far away from the tablet spring, is provided with a rod fixing hole, the rod fixing hole comprises a pressure rod fixing hole, a working position rod fixing hole and a non-working position rod fixing hole, the rod fixing hole is located on the same straight line and parallel to the tablet, and the non-working position rod fixing hole is located in the working position rod fixing hole and is kept away from the pressure rod fixing hole. The preforming spring is preferred to include 4 groups, and the preforming spring sets up respectively in the position that corresponds with work position dead lever, non-work position dead lever. The working position fixing rod and the non-working position fixing rod are preferably solid cylinder pressing parts.

One end of the control pressure lever, one end of the working position fixing lever and one end of the non-working position fixing lever are respectively fixed on one side of the pressing sheet far away from the pressing sheet spring, and the other ends of the control pressure lever, the working position fixing lever and the non-working position fixing lever respectively protrude out of the control button shell through the pressure lever fixing hole, the working position lever fixing hole and the non-working position lever fixing hole.

The working position fixing rod and the non-working position fixing rod respectively comprise two cylinder pressing parts, and the working position rod fixing hole corresponds to the working position fixing rod and comprises two holes; the non-working position rod fixing hole corresponds to the non-working position fixing rod and comprises two openings; the direct distance between the two openings of the working position rod fixing hole and the non-working position rod fixing hole is equal to the thickness of the protective shell.

Under the operation of the control pressure rod and the control pressure sheet, the parts of the 2 groups of solid cylindrical pressing parts of the non-working position fixing rods, which extend out of the inner cavity of the position control rod, are respectively clamped on the inner side and the outer side of the protective shell, so that the fixture and the resistance strain gauge group on the fixture are in the non-working position.

Under the operation of the control pressure rod and the control pressure sheet, the parts of the 2 groups of solid cylinder pressing parts of the working position fixing rods, which extend out of the inner cavity of the position control rod, are respectively clamped on the inner side and the outer side of the protective shell, so that the fixture and the resistance strain gauge group on the fixture are positioned at the working position.

Specifically, when the resistance strain gauge of the monitoring device is located at a working position, the part of the working position fixing rod, which extends out of the control button shell, and the cylinder pressing piece adjacent to the control pressing rod is arranged on one side of the outer wall of the protective shell, the part of the working position fixing rod, which extends out of the control button shell, and is far away from the cylinder pressing piece of the control pressing rod is arranged on one side of the inner wall of the protective shell, and at the moment, the two cylinder pressing pieces of the working position fixing rod are respectively arranged on the inner side and the outer side of the protective shell, so that the resistance strain gauge set is fixed at the working position. At the moment, the fixture enters the gap of the inner circle circumference of the protective shell, and the fixture is fixed in the gap, so that the fixture is prevented from swinging to influence the monitoring of the fluid pressure by the resistance strain gauge group. When the resistance strain gauge of the monitoring device is in a non-working position, the part, extending out of the control button shell, of the cylinder pressing piece of the non-working position fixing rod adjacent to the working position fixing rod is arranged on one side of the outer wall of the protective shell, the part, extending out of the control button shell, of the cylinder pressing piece of the non-working position fixing rod far away from the working position fixing rod is arranged on one side of the inner wall of the protective shell, and at the moment, the resistance strain gauge group is fixed in the non-working position by respectively arranging the two cylinder pressing pieces of the non-working position fixing rod on the inner side and the outer side of the protective shell. When the position of the resistance strain gauge group needs to be adjusted, the cylinder pressing piece of the working position fixing rod and the non-working position fixing rod is controlled to protrude out of the part of the control button shell by applying pressure to the control pressure rod and enter/be parallel to the control button shell.

When the fixture is in a non-working position, the fixture and the resistance strain gauge group are positioned in the inner cavity of the protective shell; when the fixture is in a working position, the fixture and the resistance strain gauge group are positioned at an inner circle circumferential gap of the protective shell, so that the resistance strain gauge is in contact with fluid in the pipeline.

The resistance strain gauge group is positioned at a working position, deformation change caused by front and back pressure difference and fluid impact is converted into an electric signal and is output to the computer, and the computer obtains a continuous pressure waveform diagram and a continuous flow velocity waveform diagram at a monitoring point according to the one-to-one correspondence relationship between the electric signal and pressure and fluid flow velocity.

In the processes of storage, transportation and installation, the resistance strain gauge group and the fixture are in a non-working position, so that the protection effect is achieved. After the installation is finished and before the pipeline is started, the resistance strain gauge group and the clamp are located at a working position, and the clamp and the sealing material are completely filled in a reserved inner circle circumferential gap of the protective shell so as to prevent fluid from entering an inner cavity of the monitoring device to cause damage.

The first part of the protective shell is provided with a single chip microcomputer protective shell, the single chip microcomputer protective shell is fixed in the middle point position of the outer wall of the first part, and as shown in figures 1 and 2, the single chip microcomputer is fixed in the single chip microcomputer protective shell. The protective housing with singlechip protective housing junction reserve has the through wires hole, the singlechip is connected respectively the wire of resistance foil gage, pass the through wires hole with the resistance foil gage is connected. The protection sleeve is a hollow short cylinder made of flexible materials. The conductive wire is fixedly laid in an inner cavity 14 formed after the protective shell is assembled. The single chip microcomputer protection shell and the first part of the protection shell are integrated, namely the single chip microcomputer protection shell and the first part of the protection shell are composed of two symmetrical shells.

The single chip microcomputer protective shell is far away from one end of the protective shell, a threading hole is reserved in the end, and the single chip microcomputer is connected with the data acquisition card through the threading hole.

When the monitoring device is installed in a fluid conduit, the housing portion of the single-chip microcomputer is preferably located vertically above the fluid conduit for later maintenance, and may be oriented in any other than vertically downward orientation.

The protection shell is provided with a flange connecting hole, the flange connecting hole is filled by a protection plug, a sealing gasket is arranged between the protection shell of the monitoring device and a flange disc of the pipeline to be tested, the monitoring device is connected with the fluid pipeline through the flange disc during installation and compresses the sealing gasket, and the inner circumference inner surface of the inner circle of the protection shell is flush with the inner surface of the fluid pipeline. The flange connecting hole is matched with the specification of the flange plate used by the pipeline to be tested, and no specific limitation is made here.

The protective shell and the resistance strain gauge clamp of the monitoring device can be made of seamless steel pipes, cast iron pipes, PE pipes and the like, and it is required to be noted that the material and the strength of the protective shell and the resistance strain gauge clamp of the monitoring device are not lower than those of the fluid pipeline body to be detected.

A fluid pipeline leakage on-line monitoring and positioning control method is a control method for carrying out fluid pipeline leakage on-line monitoring and positioning based on the fluid pipeline leakage on-line monitoring and positioning device, and specifically comprises the following steps:

The first step further comprises the step of respectively arranging monitoring devices on monitoring points of each divided section of straight pipeline, wherein the monitoring devices are respectively connected with a data acquisition card, and the data acquisition card transmits acquired electric signals to a computer to obtain continuous pressure oscillograms and flow velocity oscillograms in the pipeline at each monitoring device.

The monitoring points arranged on each divided straight pipeline section comprise three monitoring points which are respectively the end points and the middle points on the two sides of each divided straight pipeline section. The monitoring devices are respectively arranged at the end points and the middle point of two sides of each straight pipe section, so that micro-strain generated by the pressure difference between the front and the back of the resistance strain gauge caused by negative pressure waves and deformation change caused by fluid impact can be effectively captured, converted into electric signals and output, and the electric signals are input into a computer through a data acquisition card. Because of the continuity of the fluid, the speed change of the fluid in the pipeline caused by the negative pressure wave lags behind the pressure change, and the continuous pressure waveform diagram and the continuous flow velocity waveform diagram detected by each resistance strain gauge are formed through the processing and analysis of the electric signals by the computer.

Before the monitoring device is installed and arranged, detailed basic data and operation working condition parameters of a fluid pipeline system are obtained, the fluid pipeline system is divided into a plurality of continuous straight pipe sections according to a certain principle, and the pipe section division nodes generally comprise a supply source, a user, a pressure regulating device, a sectional valve, a branch pipe position, an elbow position and the like. The same pipe material, pipe diameter, temperature, pressure and constraint conditions are required to be arranged along the same straight pipe section, so that the propagation speed of the negative pressure wave is kept consistent in the same straight pipe section, and the system error caused by the calculation of the propagation speed is eliminated.

The fourth step specifically comprises the steps that if the instantaneous pressure drop value collected at each monitoring point of the straight pipe section is not smaller than a preset instantaneous pressure drop value threshold value, and the time interval of successively detecting the negative pressure waves is not larger than a preset time interval threshold value, an effective negative pressure wave is judged to be detected, and if not, an effective negative pressure wave is judged not to be detected;

judging whether the fluid pipeline leaks in the fifth step specifically comprises the following steps:

if the effective negative pressure wave straight pipe section is detected, the effective negative pressure wave in the fourth step is firstly detected by the monitoring point at the end point at the upstream side, and if the effective negative pressure wave straight pipe section is detected, the negative pressure wave is detected by the monitoring points at the middle point and the other end point in sequence at the same time interval (the time interval for detecting the negative pressure wave from the upstream end point to the middle point is the same as the time interval for detecting the negative pressure wave from the middle point to the downstream point), the negative pressure wave is judged not to be generated by the leakage of the straight pipe section; if one end of a monitoring point on the straight pipe section, which detects the negative pressure wave firstly, is connected with a fluid supply source or a user or a pressure regulating device, the negative pressure wave can be judged to be caused by service operation;

judging the leakage position and calculating the leakage amount in the sixth step specifically comprise:

In the sixth step, the content of the leakage report output by the computer comprises the position of the cross section of the pipeline where the leakage point is located, the approximate direction of the leakage point on the cross section of the pipeline and the leakage amount generated by the leakage.

According to the continuous pressure oscillogram of the corresponding point in the pipeline collected by each point monitoring device under the normal stable operation condition of the fluid pipeline system, the instantaneous pressure drop threshold value of each point in the pipeline corresponding to each point of each point monitoring device under the stable operation condition is set, the threshold value is higher than the maximum pressure drop fluctuation value of each point under the normal stable operation condition, the smaller the difference value between the two is, the higher the requirements on the performances of a resistance strain gauge, a single chip microcomputer and a data acquisition card and the precision of pressure fluctuation signals processed by a computer are, the larger the calculated amount is, and the more accurate monitoring and positioning of pipeline leakage can be realized. The time interval threshold value of the negative pressure wave detected by the other two monitoring devices on the same straight pipe section relative to the first monitoring device detecting the negative pressure wave is preset, and the setting of the threshold value is related to the propagation speed of the negative pressure wave in the straight pipe section, the flow speed and the flow direction of the medium and the length of the straight pipe section.

And according to pressure fluctuation signals input into the computer by the three monitoring devices on the straight pipe section through the data acquisition card, forming a continuous oscillogram, and calculating the sequence and time interval of the negative pressure waves detected by the three monitoring devices based on a preset instantaneous pressure drop threshold and a preset time interval threshold, wherein the sequence and time interval are used for judging whether the negative pressure waves come from the pipe section or the direction of the pipe section dividing node.

The criterion for detecting the effective negative pressure wave is that the instantaneous pressure drops in the pipeline detected by the three monitoring devices on the straight pipe section are not less than a preset instantaneous pressure drop threshold value, and the time intervals for sequentially detecting the negative pressure wave are not more than a preset time interval threshold value. Because the three monitoring devices are respectively arranged at the end points and the middle point of the two sides of the straight pipe section, the direction of the negative pressure wave from the pipe section or the division node of the pipe section can be judged according to the position of the first monitoring device for detecting the negative pressure wave and the time interval of the other two monitoring devices for detecting the same negative pressure wave in sequence.

When the instantaneous pressure drop in the pipeline at one monitoring device of the straight pipeline sections is not less than a set pressure drop threshold value, negative pressure waves are detected, and the other two monitoring devices detect the negative pressure waves at different time intervals relative to the first monitoring device for detecting the negative pressure waves, namely the instantaneous pressure drops in the pipeline at two positions are not less than the set pressure drop threshold value, and the time intervals are not greater than the set time interval threshold value, the straight pipeline section can be judged to leak, the distance from a leakage point to the monitoring device for detecting the negative pressure waves at first can be calculated according to a leakage point positioning formula, the position of the section where the leakage point is located is further determined, and the approximate position of the leakage point on the cross section of the pipeline is judged by detecting the position of a resistance strain gauge of the negative pressure waves at first.

When a monitoring device at one end point of the straight pipe section detects a negative pressure wave firstly, and monitoring devices at the middle point and the other end point detect the negative pressure wave at the same time interval in sequence, the negative pressure wave can be judged not to be generated by leakage of the pipe section; if one end of the monitoring device, which detects the negative pressure wave on the straight pipe section first, is connected with a supply source or a user or a pressure regulating device, it can be determined that the negative pressure wave is caused by service operation.

If one end of the monitoring device, which detects the negative pressure wave firstly, on the straight pipe section is connected with other straight pipe sections, the leakage point position can be determined jointly according to the sequence and the time difference of the negative pressure wave detected by the three monitoring devices arranged on all the adjacent pipe sections of the straight pipe section. When the monitoring devices on the sides of the subsection nodes of the adjacent straight pipe sections detect the negative pressure waves at the same time, and the other two monitoring devices on all the adjacent straight pipe sections detect the negative pressure waves at the same time interval in sequence, the leakage point is judged to be at the subsection node.

After the leakage is confirmed and the leakage point position is determined, after the flow velocity of the fluid in the straight pipe section to be leaked is fully developed, the computer gives sectional flow velocity oscillograms of two monitoring devices before and after the leakage point to obtain the average flow velocity of two sections, and the leakage amount is calculated through a flow calculation formula and a continuity equation to judge the severity of the leakage.

Two embodiments of the present invention are further described below with reference to fig. 7 and 8:

first embodiment, as shown in figure 7, this embodiment relates to a fluid conduit system having a single straight section.

On the straight pipe section 20, two ends and a middle point are respectively provided with three

monitoring devices

201, 202 and 203, and the distance between the monitoring devices is marked as L. The three monitoring devices are connected with a computer 18 through a data acquisition card 19, pressure fluctuation signals and cross section flow velocity signals at corresponding monitoring points in the pipeline are input into the computer 18, and continuous pressure waveform diagrams and flow velocity waveform diagrams corresponding to each resistance strain gauge are formed.

On the computer 18, according to the pressure oscillogram of three monitoring devices in the pipeline under the normal and stable operation condition, analyzing and obtaining the maximum instantaneous pressure drop in the pipeline of each monitoring point, so as to set the instantaneous pressure drop threshold value P of each monitoring point₂₀₁₀、P_2020、P₂₀₃₀And are all larger than the maximum instantaneous pressure drop under the normal and stable operation working condition in the pipeline of the corresponding monitoring point. Analyzing to obtain the maximum flow velocity fluctuation value in the pipeline of each monitoring point according to the flow velocity oscillogram of three monitoring devices in the pipeline under the normal and stable operation condition, and setting the flow velocity fluctuation threshold value V of each monitoring point₂₀₁₀、V_2020、V₂₀₃₀And the flow velocity fluctuation value is not larger than the maximum flow velocity fluctuation value under the normal and stable operation condition in the pipeline of the corresponding monitoring point.

The propagation speed of the negative pressure wave in the fluid is far greater than the flow speed of the common fluid, for example, the propagation speed a of the negative pressure wave in the water is about 1200-1400 m/s, and the flow speed v of the water in the heat supply pipeline is generally not greater than 3m/s, so that the influence of the fluid speed and direction on the propagation of the negative pressure wave is small and can be ignored. Presetting a time interval threshold value delta t₂₀>L/a. The propagation speed of the negative pressure wave in the fluid depends on the volume elastic coefficient and density of the fluid medium, the elastic modulus of the pipe and the constraint condition of the straight pipe section, and can be calculated, or an empirical value with relatively low propagation speed in the negative pressure wave fluid can be adopted, for example, the propagation speed in water is a =1200 m/s.

As shown in FIG. 7, if at any time on the straight pipe section 20, the monitoring device 202 will exhibit an instantaneous pressure drop P corresponding to the pressure waveform inside the pipe at the monitoring point₂₀₂₁≥P₂₀₂₀At intervals of time Δ t₂₀₁Then, the monitoring device 203 corresponds to the instantaneous pressure drop P presented by the pressure oscillogram in the pipeline of the monitoring point₂₀₃₁≥P₂₀₃₀Is further spaced by a time Δ t₂₀₂Then, the monitoring device 201 corresponds to the instantaneous pressure drop P presented by the pressure oscillogram in the pipeline at the monitoring point₂₀₁₁≥P₂₀₁₀And Δ t₂₀₁≤Δt₂₀And Δ t₂₀₂≤Δt₂₀Accordingly, the computer 18 will determine that a leak has occurred in the straight tube section 20 and will provide the distance X from the leak point 200 to the corresponding monitoring point of the monitoring device 202, and the leak point location calculation formula is as follows.

（1）

And by first detecting the position of the resistive strain gage of the negative pressure wave, the approximate orientation of the leak point in the cross section of the pipe is given. When the flow velocity oscillograms in the pipelines at the monitoring points corresponding to the

monitoring devices

202 and 203 tend to be stable, that is, the flow velocity fluctuation values at the two points are not greater than the set flow velocity fluctuation threshold value, the flow velocity in the pipeline is fully developed after the straight pipe section 20 is judged to be leaked, and the computer 18 reads the section average flow velocity value V in the pipeline at the monitoring points corresponding to the

monitoring devices

202 and 203 at the moment_202、V₂₀₃The leakage amount calculation formula is as follows:

（2）

wherein A is₂₀Is the cross-sectional area of the straight tube section 20.

At this point, the computer 18 issues a leak alarm and outputs a leak report containing the location of the cross-section of the pipe where the leak is located, the approximate orientation of the leak in the cross-section of the pipe, and the amount of leak that results from the leak.

As shown in FIG. 7, if at any time on the straight pipe section 20, the monitoring device 201 corresponds to the instantaneous pressure drop P presented by the pressure waveform diagram in the pipeline at the monitoring point₂₀₁₂≥P₂₀₁₀At intervals of time Δ t₂₀₃Then, monitoring deviceSetting 202 the instantaneous pressure drop P presented by the pressure wave form diagram in the pipeline corresponding to the monitoring point₂₀₂₂≥P₂₀₂₀Is further spaced by a time Δ t₂₀₄Then, the monitoring device 203 corresponds to the instantaneous pressure drop P presented by the pressure oscillogram in the pipeline of the monitoring point₂₀₃₂≥P₂₀₃₀And Δ t₂₀₃=Δt₂₀₄≤Δt₅₀Accordingly, the computer 18 will determine that the negative pressure wave is from the service operation of the supply source 1 and will not issue a leak alarm.

As shown in FIG. 7, if at any time on the straight pipe section 20, the monitoring device 203 will exhibit an instantaneous pressure drop P corresponding to the pressure waveform inside the pipeline at the monitoring point₂₀₃₃≥P₂₀₃₀At intervals of time Δ t₂₀₅Thereafter, the monitoring device 202 responds to the instantaneous pressure drop P exhibited by the pressure waveform in the pipeline at the monitoring point₂₀₂₃≥P₂₀₂₀Is further spaced by a time Δ t₂₀₆Then, the monitoring device 201 corresponds to the instantaneous pressure drop P presented by the pressure oscillogram in the pipeline at the monitoring point₂₀₁₃≥P₂₀₁₀And Δ t₂₀₅=Δt₂₀₆≤Δt₂₀Accordingly, the computer 18 will determine that the negative pressure wave is from the business operation of the user 1 and will not issue a leak alarm.

As shown in fig. 7, if at a certain time, the instantaneous pressure drop presented by the pressure waveform diagram of a monitoring point corresponding to a certain monitoring device on the straight pipe section 20 is not less than the set instantaneous pressure drop threshold, and the pressure waveform diagram of one or two monitoring points corresponding to the other two monitoring devices is not presented within the set time interval threshold and is not less than the set instantaneous pressure drop threshold, so that the computer 18 determines that the detected negative pressure wave is an invalid pressure fluctuation signal, and does not give a leakage alarm.

Example two, as shown in fig. 8, this embodiment relates to a fluid conduit system of a single supply source, multiple users, a branch pipe, and multiple straight pipe sections, and the fluid medium flows from the supply source 2 to the users 2 and 3.

According to the straight pipe section dividing principle of the invention, the fluid pipeline system shown in FIG. 6 is divided into the straight pipe section 30, the straight pipe section 40, the straight pipe section 50 and the straight pipe section 60 which respectively have the same pipe material, pipe diameter, temperature, pressure and constraint condition by taking the supply source 3, the tee joint 30-40-50, the elbow 50-60, the user 2 and the user 3 as nodes.

Monitoring devices are respectively arranged at two end points and a middle point of the straight pipe section 30, the straight pipe section 40, the straight pipe section 50 and the straight pipe section 60, and the monitoring devices arranged at the middle node are arranged at equal intervals relative to the node.

On the straight pipe section 30, near the supply source 2 and the tee joints 30-40-50 and at the middle point,

monitoring devices

301, 302 and 303 are respectively arranged, and the distance between the monitoring devices is marked as L^/. The three monitoring devices are connected with a computer 18 through a data acquisition card 19, pressure fluctuation signals and cross section flow velocity signals at corresponding monitoring points in the pipeline are input into the computer 18, and continuous pressure waveform diagrams and flow velocity waveform diagrams corresponding to each resistance strain gauge are formed.

Three

monitoring devices

401, 402 and 403 are respectively arranged on the straight pipe section 40, close to the user 2, the tee joints 30-40-50 and the middle point, and the distance between the monitoring devices is marked as L^//. The three monitoring devices are connected with a computer 18 through a data acquisition card 19, pressure fluctuation signals and cross section flow velocity signals at corresponding monitoring points in the pipeline are input into the computer 18, and continuous pressure waveform diagrams and flow velocity waveform diagrams corresponding to each resistance strain gauge are formed.

Three

monitoring devices

501, 502 and 503 are respectively arranged on the straight pipe section 50, the tee joints 30-40-50, the elbows 50-60 and the middle points, and the distance between the monitoring devices is marked as L^///. The three monitoring devices are connected with a computer 18 through a data acquisition card 19, pressure fluctuation signals and cross section flow velocity signals at corresponding monitoring points in the pipeline are input into the computer 18, and continuous pressure waveform diagrams and flow velocity waveform diagrams corresponding to each resistance strain gauge are formed.

Three

monitoring devices

601, 602 and 603 are respectively arranged on the straight pipe section 60, near the user 3, the elbows 50-60 and at the middle point, and the distance between the monitoring devices is marked as L^////. The three monitoring devices are connected with a computer 18 through a data acquisition card 19, pressure fluctuation signals and cross section flow velocity signals at corresponding monitoring points in the pipeline are input into the computer 18, and continuous pressure waveform diagrams and flow velocity waveform diagrams corresponding to each resistance strain gauge are formed.

On the computer 18, according to the pressure oscillogram of three monitoring devices in the pipeline under the normal and stable operation condition, analyzing and obtaining the maximum instantaneous pressure drop in the pipeline of each monitoring point, so as to set the instantaneous pressure drop threshold value P of each monitoring point₃₀₁₀、P_3020、P₃₀₃₀，P₄₀₁₀、P_4020、P₄₀₃₀，P₅₀₁₀、P_5020、P₅₀₃₀，P₆₀₁₀、P_6020、P₆₀₃₀And are all larger than the maximum instantaneous pressure drop under the normal and stable operation working condition in the pipeline of the corresponding monitoring point. Analyzing to obtain the maximum flow velocity fluctuation value in the pipeline of each monitoring point according to the flow velocity oscillogram of three monitoring devices in the pipeline under the normal and stable operation condition, and setting the flow velocity fluctuation threshold value V of each monitoring point₃₀₁₀、V_3020、V₃₀₃₀，V₄₀₁₀、V_4020、V₄₀₃₀，V₅₀₁₀、V_5020、V₅₀₃₀，V₆₀₁₀、V_6020、V₆₀₃₀And the flow velocity fluctuation value is not larger than the maximum flow velocity fluctuation value under the normal and stable operation condition in the pipeline of the corresponding monitoring point.

The propagation speed of the negative pressure wave in the fluid is far greater than the flow speed of the common fluid, for example, the propagation speed a of the negative pressure wave in the water is about 1200-1400 m/s, and the flow speed v of the water in the heat supply pipeline is generally not greater than 3m/s, so that the influence of the fluid speed and direction on the propagation of the negative pressure wave is small and can be ignored. The time interval threshold of each straight pipe section is set. The propagation speed of the negative pressure wave in the fluid depends on the volume elastic coefficient and density of the fluid medium, the elastic modulus of the pipe and the constraint condition of the straight pipe section, and can be calculated, or an empirical value with relatively low propagation speed in the negative pressure wave fluid can be adopted, for example, the propagation speed in water is a =1200 m/s.

The time interval threshold for the straight pipe section 30 is denoted as Δ t₃₀> L^/A, the time interval threshold of the straight pipe section 40 is recorded as delta t₄₀> L^//A, the time interval threshold of the straight pipe section 50 is recorded as delta t₅₀> L^///A, the time interval threshold of the straight pipe section 60 is recorded as delta t₆₀> L^/////a。

If at any time, the straight pipe section 40 is monitored, as shown in FIG. 8The device 402 responds to the instantaneous pressure drop P exhibited by the pressure waveform profile within the pipeline at the point of monitoring₄₀₂₁≥P₄₀₂₀At intervals of time Δ t₄₀₁Then, the monitoring device 401 corresponds to the instantaneous pressure drop P displayed by the pressure oscillogram in the pipeline at the monitoring point₄₀₁₁≥P₄₀₁₀Is further spaced by a time Δ t₄₀₂Then, the monitoring device 403 corresponds to the instantaneous pressure drop P presented by the pressure oscillogram in the pipeline at the monitoring point₄₀₃₁≥P₄₀₃₀And Δ t₄₀₁≤Δt₄₀And Δ t₄₀₂≤Δt₄₀Based thereon, the computer 18 will determine that a leak has occurred in the straight tube section 40 and will provide a distance X from the leak 400 to the corresponding monitoring point of the monitoring device 402^/The leak point location calculation formula is as follows.

（3）

And by first detecting the position of the resistive strain gage of the negative pressure wave, the approximate orientation of the leak point in the cross section of the pipe is given. When the flow velocity oscillograms in the pipelines of the monitoring points corresponding to the

monitoring devices

401 and 402 tend to be stable, that is, the flow velocity fluctuation values at the two points are not more than the set flow velocity fluctuation threshold value, the flow velocity in the pipeline is fully developed after the straight pipe section 40 is judged to leak, and the computer 18 reads out the average section flow velocity value V in the pipeline of the monitoring points corresponding to the

monitoring devices

401 and 402 at the moment_401、V₄₀₂The leakage amount calculation formula is as follows:

（4）

wherein A is₄₀Is the cross-sectional area of the straight tube section 40.

As shown in FIG. 8, if at any time, the monitoring device 403 on the straight pipe section 40 corresponds to the pressure waveform inside the pipeline at the monitoring pointExhibiting a transient pressure drop P₄₀₃₂≥P₄₀₃₀At intervals of time Δ t₄₀₃Thereafter, the monitoring device 402 corresponds to the instantaneous pressure drop P exhibited by the pressure waveform in the pipeline at the monitoring point₄₀₂₂≥P₄₀₂₀Is further spaced by a time Δ t₄₀₄Then, the monitoring device 401 corresponds to the instantaneous pressure drop P displayed by the pressure oscillogram in the pipeline at the monitoring point₄₀₁₂≥P₄₀₁₀And Δ t₄₀₃=Δt₄₀₄≤Δt₄₀Accordingly, the computer 18 will determine that the negative pressure wave is from the service operation of the user 2 and will not issue a leak alarm.

As shown in FIG. 8, if at any time, the monitoring device 303 on the straight pipe section 30 corresponds to the instantaneous pressure drop P presented by the pressure wave pattern in the pipeline at the monitoring point₃₀₃₁≥P₃₀₃₀The instantaneous pressure drop P displayed by the monitoring device 401 on the straight pipe section 40 corresponding to the pressure oscillogram in the pipeline at the monitoring point₄₀₁₃≥P₄₀₁₀The instantaneous pressure drop P displayed by the monitoring device 501 on the straight pipe section 50 corresponding to the pressure oscillogram in the pipeline at the monitoring point₅₀₁₁≥P₅₀₁₀(ii) a Then, the other two monitoring devices of the straight pipe section 30, the straight pipe section 40 and the straight pipe section 50 detect the negative pressure wave successively at the same time interval respectively, and accordingly the computer judges that the tee joints 30-40-50 leak. The computer gives the approximate orientation of the leak point in the cross-section of the pipe by first detecting where the resistive strain gage of the negative pressure wave is located. When the flow velocity oscillograms in the pipelines of the monitoring points corresponding to the

monitoring devices

303, 401 and 501 tend to be stable, that is, the flow velocity fluctuation values at the three points are not more than the set flow velocity fluctuation threshold value, the flow velocity in the pipelines is fully developed after the tee joints 30-40-50 are judged to leak, and the computer 18 reads the average flow velocity value V of the cross sections in the pipelines of the

monitoring devices

303, 401 and 501 corresponding to the monitoring points at the moment_303、V^/ ₄₀₁、V₅₀₁The leakage amount calculation formula is as follows:

（5）

wherein A is₃₀Is a straight pipe section 30 with a cross-sectional area A₄₀Is a cross-sectional area, A, of the straight tube section 40₅₀Is the cross-sectional area of the straight tube section 50.

An on-line monitoring and positioning device for leakage of a fluid pipeline and a control method thereof can monitor whether the fluid pipeline leaks on line and judge the approximate position of a leakage point on the cross section of the pipeline and the severity of the leakage. The online monitoring and positioning system is suitable for online monitoring and positioning of leakage of a single straight pipe section, is also suitable for online monitoring and positioning of leakage of a plurality of continuous straight pipe sections and pipe sections with branch lines, can identify and eliminate pressure fluctuation interference caused by business operation, and can effectively improve online monitoring and positioning levels of leakage of fluid pipelines such as water, gas, heat, oil and the like by popularization and application.

The above description is provided for the purpose of illustrating the preferred embodiments of the present invention and will assist those skilled in the art in more fully understanding the technical solutions of the present invention. However, these examples are merely illustrative, and the embodiments of the present invention are not to be considered as being limited to the description of these examples. For those skilled in the art to which the invention pertains, several simple deductions and changes can be made without departing from the inventive concept, and all should be considered as falling within the protection scope of the invention.

Claims

1. The device is characterized by comprising a computer, a data acquisition card and a monitoring device, wherein the monitoring device is arranged on a fluid pipeline divided into a plurality of continuous straight pipe sections through a flange plate, the monitoring device is connected with the data acquisition card, and the data acquisition card is connected with the computer;

2. The device according to claim 1, wherein the electrical signals collected by the data acquisition card are transmitted to a computer, and the computer obtains a continuous pressure waveform diagram and a continuous flow velocity waveform diagram in the pipeline at each monitoring device according to the collected electrical signals.

3. The device for on-line monitoring and positioning the leakage of the fluid pipeline as claimed in claim 1, wherein three monitoring devices are respectively installed on each divided straight pipeline section and are respectively installed at the end points and the middle point of the two sides of each straight pipeline section.

4. The fluid pipeline leakage online monitoring and positioning device according to claim 1, wherein the monitoring device comprises a protective casing, a single chip microcomputer and a resistance strain gauge set, the resistance strain gauge is used for detecting deformation changes caused by pressure difference between the front and the back of the fluid pipeline and fluid impact, and the single chip microcomputer converts the real-time deformation changes of the resistance strain gauge into electrical signals;

5. The fluid pipeline leakage online monitoring and positioning device as claimed in claim 4, wherein the resistance strain gauge groups comprise four groups, the resistance strain gauge groups are respectively arranged in four clamps, and the four clamps are arc-shaped structures with the same radius and the radian of 90 degrees;

6. The device for on-line monitoring and positioning of fluid pipeline leakage as claimed in claim 4, wherein the protective casing is an annular structure with an inner cavity, the resistance strain gauge set is arranged in the inner cavity of the protective casing, a single chip microcomputer protective casing is arranged on the top of the outer circumference of the protective casing, and the single chip microcomputer is fixed in the single chip microcomputer protective casing.

7. The device as claimed in claim 4, wherein the side wall of the protective casing is provided with a flange connecting hole, and the flange connecting hole is used for connecting the monitoring device and the fluid pipeline through a flange.

8. A fluid pipeline leakage on-line monitoring and positioning control method is a control method for carrying out fluid pipeline leakage on-line monitoring and positioning based on a fluid pipeline leakage on-line monitoring and positioning device, and specifically comprises the following steps: