CN113482835A - Water turbine top cover bolt looseness detection system and design method of detector - Google Patents

Water turbine top cover bolt looseness detection system and design method of detector Download PDF

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Publication number
CN113482835A
CN113482835A CN202110885287.0A CN202110885287A CN113482835A CN 113482835 A CN113482835 A CN 113482835A CN 202110885287 A CN202110885287 A CN 202110885287A CN 113482835 A CN113482835 A CN 113482835A
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bolt
ring surface
top cover
pressure detector
unit
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CN202110885287.0A
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陆国强
赵航
陆鑫洪
石雪慧
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Sanjiang University
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Sanjiang University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B11/00—Parts or details not provided for in, or of interest apart from, the preceding groups, e.g. wear-protection couplings, between turbine and generator
    • F03B11/008—Measuring or testing arrangements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/20—Hydro energy

Abstract

The invention discloses a water turbine top cover bolt looseness detection system and a design method of a detector, wherein the detection system comprises a strain type pressure detector, a wireless transmitter and a diagnosis alarm unit, the strain type pressure detector adopts a gasket type pressure sensor, a shear beam structure is formed at a transition groove position through a gasket body, and forces borne by an inner ring surface and an outer ring surface respectively act on two ends of the shear beam, so that the shear beam is axially deformed, and the bolt load change is linked with the axial displacement deformation; the design method of the detector is based on the physical characteristics of the combined bolt and the assembly requirement of the combined bolt, and simultaneously calculates the size of the gasket body which ensures that no dent is deformed on the flange surface, so that the sensitivity of detecting the looseness of the combined bolt is high, and the feedback is timely; through the wireless transmitter, the diagnosis alarm unit realizes that manual detection and analysis alarm are not needed.

Description

Water turbine top cover bolt looseness detection system and design method of detector
Technical Field
The invention belongs to the technical field of water pump turbine bolt looseness detection, and particularly relates to a water turbine top cover bolt looseness detection system and a design method of a detector.
Background
The water pump turbine is important equipment of a pumped storage power station, the rotating wheel rotates clockwise to operate as the water turbine, the conversion of water energy to mechanical energy is realized, and the water pump turbine is combined with the generator to realize the conversion of mechanical energy to electric energy; the runner rotates anticlockwise to operate as a water pump, and conversion from mechanical energy to water energy is achieved. The water pump turbine unit comprises a seat ring, a top cover, a bottom ring, a water turbine, a water guide bearing, a main shaft seal, a guide vane and a servomotor, wherein the top cover is connected with the seat ring and fixed through 80 handle bolts, the specification is M120 x 6, namely the tooth diameter is 120mm, the tooth pitch is 6mm, and the pre-tightening stress of each handle bolt reaches 525 MPa.
The top cover of the pump turbine is connected with the seat ring, the bolt is stretched manually through the hydraulic stretcher, the elongation is 1.4mm, then the bolt is screwed through the manual driving lever inserted into the driving hole of the nut, and then the bolt is loosened to form bolt pre-tightening. If close the bolt process in the installation, can not reach 1.4mm to the tensile elongation of screw rod, again because the pump turbine has the vibration at the operation in-process, the vertical direction amplitude reaches 200um, and the horizontal direction amplitude reaches 150um, at long-time operation in-process, not hard up phenomenon can appear in the bolt, can break even. If one pump turbine has a plurality of bolts to break, the shafting can cause the unstability, and huge water hammer pressure can cause the machine of lifting and the roof fracture, leads to the serious accident that underground factory building floods, personnel die.
At present, a method for monitoring looseness of a bolt closed by a top cover is characterized in that operation and maintenance personnel of a pumped storage power station mark the bolt through a marking pen, namely, a line is respectively drawn on a screw rod and a nut, whether the line is on the same line or not is regularly observed by naked eyes, and if deviation occurs, the bolt is loosened; since visual observation depends on the technical experience and responsibility of personnel and the problem is found to have time lag, in order to overcome the limitation of visual detection, the following two mechanical detection methods are commonly used in the industry at present:
the method comprises the steps that a sensor is made into a sleeve form, a rear-mounted installation mode is adopted, the sensor is sleeved on a nut, the principle of the sensor is a Hall sensing principle, namely when the nut is loosened and angular displacement reaches 5 degrees or more, the sensor can detect that the bolt is loosened and send an alarm;
and secondly, embedding the optical fiber sensor in an observation hole of the screw, measuring the elongation of the screw based on the fiber grating technology, and sending a change value to background management software after the elongation of the screw is changed.
The first method has the advantages that the installation is convenient, but because the pretightening force of the top cover seat ring is 525MPa, when the bolt is loosened, the pretightening force can reach dozens of MPa to hundreds of MPa, the screw thread is tightly attached to the nut thread, the screw is displaced in the axial direction, the angular displacement of the screw is very small and is basically less than 5 degrees, and the sensor is difficult to detect.
The second method has the advantages that the axial displacement of the screw can be quantitatively measured, the pretightening force can be converted according to the axial displacement, but for the use of the optical fiber sensor, the premise is that an observation hole needs to be reserved for the screw bolt, and the actual condition is that 80 bolts are reserved for one pump turbine, wherein only 4 bolts are reserved for the observation hole, so that the requirement of monitoring all 80 bolts is difficult to meet.
Disclosure of Invention
In order to solve the problems, the invention provides a water turbine top cover bolt looseness detection system and a design method of a detector.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
a water turbine top cover bolt looseness detecting system comprises a top cover and a seat ring, wherein the top cover and the seat ring are fixedly connected through a plurality of combining bolts and corresponding nuts; wherein, the strain type pressure detector and the handle bolt are arranged in a one-to-one manner; acquiring the pretightening force of each fastening bolt in real time by a strain type pressure detector; the strain type pressure detector is of a gasket type and comprises a gasket body and a strain gauge; the gasket body is sleeved on the handle bolt and positioned between the nut and the flange surface of the top cover; the gasket body sequentially comprises a central hole, an inner ring surface, a transition groove and an outer ring surface from the center to the edge; wherein, the stressed side of the inner ring surface protrudes out of the outer ring surface, and the outer ring surface is connected with the side wall of the inner ring surface; on the non-stressed side of the inner ring surface, the outer ring surface protrudes out of the inner ring surface, and the transition groove is formed between the side wall of the outer ring surface and the side wall of the inner ring surface; the strain gauge is arranged at the bottom of the transition groove; the plurality of strain gauges are uniformly distributed along the circumferential direction of the gasket body;
the wireless transmitter transmits the signal of the strain gauge pressure detector to the diagnosis and alarm unit;
the diagnosis alarm unit is in communication connection with the wireless transmitter and is used for acquiring real-time detection data of the strain type pressure detector through the wireless transmitter, judging the loosening failure condition of the combined bolt according to the real-time detection data, acquiring a loosening failure diagnosis result of the combined bolt and generating an alarm signal when the combined bolt fails.
Further, the upper surface of the inner ring surface is subjected to the pre-tightening force of the fastening bolt; the lower surface of the outer ring surface is subjected to the reaction force of the flange surface of the top cover; under the action of the pretightening force of the bolt and the reaction force of the flange surface of the top cover, the transition groove deforms; the strain gauge is adhered to the bottom of the transition groove, and the plurality of strain gauges are connected through an equal-arm bridge measuring circuit.
Further, the wireless transmitter is connected with the strain gauge pressure detector through an analog signal line; the wireless transmitter comprises a shell and a wireless transmission module; wherein, be provided with magnet on the shell, wireless transmitter passes through magnet is installed on the top cap.
Further, the wireless transmission module comprises an LoRa communication module and a microcontroller, and the microcontroller controls the LoRa communication module according to the following control method:
step 1, setting a pre-tightening force change alarm threshold value delta F and a strain type pressure detector acquisition time interval T according to requirements1The communication heartbeat interval with the diagnosis alarm unit is T2；
Step 2, recording the data of the pretightening force of the closed bolt at the current moment of the strain type pressure detector, and recording the data as Ft；
Step 3, calculating the pretightening force change value, and recording the pretightening force change value as delta FtThe specific calculation formula is as follows:
ΔFt＝Ft-Ft-1wherein F ist-1The pre-tightening force data of the fastening bolt at the previous moment;
step 4, if delta FtIf the value is larger than or equal to delta F, when the pre-tightening force change alarm threshold value is reached, jumping to the step 5, otherwise, jumping to the step 6;
step 5, immediately starting the LoRa communication module and sending an alarm value delta FtAnd FtTo a diagnostic alarm unit;
step 6, calculating whether the time reaches the acquisition time interval T of the strain type pressure detector1If yes, jumping to the step 7, otherwise, continuing to the step 6;
step 7, calculating whether the time reaches the communication heartbeat interval T2If yes, jumping to the step 8, otherwise, jumping to the step 2;
step 8, immediately starting the LoRa module and sending the load F at the current momenttAnd (5) going to a diagnosis alarm unit, and skipping to the step 1.
Further, the wireless transmitter further comprises a battery, and the battery supplies power to the wireless transmission module and the strain gauge pressure detector.
A design method of a water turbine roof bolt looseness detector comprises the strain type pressure detector; further, the method comprises the following specific steps:
step 1, calculating the initial pretightening force of the closing bolt, and recording the initial pretightening force as F, wherein the unit is T;
step 2, looking up a table to obtain the yield strength of the flange surface of the top cover according to the material of the flange surface of the top cover, and recording the yield strength as P, wherein the unit is MPa;
step 3, calculating the contact between the outer ring surface of the gasket body and the flange surface of the top coverMinimum area, denoted S, in mm2(ii) a The specific formula is as follows:
P＝F/S；
step 4, calculating numerical value standards of the radius of the outer ring surface of the gasket body and the radius of the inner ring surface of the gasket body, wherein the radius of the outer ring surface is set as R, and the unit is mm; the radius of the inner ring surface is set as r, and the unit is mm; the width of the transition groove is set as w, and the unit is mm; the concrete formula is as follows;
S≤π(R2-(r+w)2)；
and 5, determining the values of the radius of the outer ring surface and the radius of the inner ring surface according to the center distance of every two fastening bolts and the distance from the center shaft of the fastening bolt to the edge of the assembly part and the width of the strain gauge in combination with the formula in the step 4, and determining the value of the width of the transition groove.
Further, in step 1, calculating the initial pretightening force of the fastening bolt, setting the initial pretightening force as F, and setting the initial pretightening force as T, wherein the specific calculation formula is as follows:
Figure BDA0003193879710000041
wherein, L is the effective length of closing the bolt, the unit: mm; e is the elastic modulus of the bolt material, unit: n/mm2(ii) a Δ L-elongation value of the closure bolt at initial pretension, unit: mm; a is the cross-sectional area of the fastening bolt, unit: mm is2。
The invention has the following beneficial effects:
firstly, a strain type pressure detector, a wireless transmitter and a diagnosis alarm unit are arranged to realize the looseness detection and alarm of the water turbine top cover bolt, the used strain type pressure detector adopts a gasket type pressure sensor, a shear beam structure is formed at the position of a transition groove through an inner ring surface, a transition groove and an outer ring surface which are arranged on a gasket body and have different protruding directions, the forces applied to the inner ring surface and the outer ring surface are respectively applied to two ends of the shear beam, so that the axial deformation of the shear beam is caused, and the pretightening force change of the bolt is linked with the axial displacement deformation; the strain gauge is axially displaced and deformed to generate a strain effect, so that real-time quantitative detection of the pretightening force is realized; because the strain gauge is arranged at the position of the transition groove, the sensitivity of the strain gauge for generating axial displacement is higher than that of a gasket type pressure sensor with consistent thickness, the sensitivity for detecting the looseness of the fastening bolt is high, and the feedback is timely; through a wireless transmitter, a diagnosis alarm sheet obtains real-time detection data of the strain type pressure detector, automatically obtains a bolt-on loosening failure diagnosis result and generates an alarm signal when failure occurs, and manual detection and analysis alarm are not needed; meanwhile, the strain type pressure detector can quantitatively detect the pretightening force of the bolt, and can detect whether the pretightening force is consistent when the bolt is initially assembled in the water pump turbine unit.
Second, wireless transmitter sets up magnet in the shell bottom, through the installation of magnet adsorption, installs convenient characteristics and is favorable to the scene to deploy the use fast.
Third, loRa communication module is with low costs, and the security is high and transport distance is far away, because loRa communication module consumption is bigger, through setting up microcontroller, adopts regularly and bolt load to change the tactics that calculate two standards and carry out wireless transmission work, the rational use electric energy.
And fourthly, the wireless transmission module and the strain type pressure detector are integrally powered by a battery, so that the engineering quantity of field wiring is reduced.
Fifthly, a design method of hydraulic turbine top cap bolt not hard up detector, because the flange face of gasket direct contact top cap, in case the gasket body causes the dent on the flange face of top cap, can influence the accuracy to the detection of axial displacement deformation, influence the sensitivity and the accuracy that detect, this scheme is based on the physical characteristic of closing the bolt and when closing the assembly requirement of bolt, calculate the size of the gasket body that guarantees can not cause the dent deformation on the flange face, accord with the design requirement, guarantee to detect the accuracy, the outward appearance of hydraulic turbine top cap is level and is not influenced its working property.
Drawings
FIG. 1 is a schematic diagram of an assembled strain gauge pressure detector according to the present invention;
FIG. 2 is a schematic cross-sectional view of a strain gauge pressure sensor;
FIG. 3 is a schematic structural diagram of a bottom view of a strain gauge pressure detector;
FIG. 4 is a schematic diagram of a strain gauge pressure sensor connected to a wireless transmitter;
FIG. 5 is a system flow diagram of a water turbine roof bolt loosening detection system;
fig. 6 is a control flow chart of the microcontroller for the LoRa communication module;
description of the symbols:
1. the device comprises a handle bolt, 2 nuts, 3 strain type pressure detectors, 3-1 gasket bodies, 3-1-1 inner ring surfaces, 3-1-2 outer ring surfaces, 3-1-3 center holes, 3-1-4 transition grooves, 3-1-5 lead interfaces, 3-2 strain gauges, 4 flange surfaces of a top cover, 5 wireless transmitters, 5-1 magnets, 6 analog signal wires, F1Pretightening force of the fastening bolt, F2Reaction of the flange face of the top cover.
Detailed Description
Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.
As shown in fig. 1-6, a water turbine roof bolt looseness detection system is used for realizing looseness detection and alarm for water turbine roof bolts; the water turbine comprises a top cover and a seat ring, wherein the top cover and the seat ring are fixedly connected through a plurality of fastening bolts 1 and corresponding nuts 2; water turbine top cap bolt looseness detecting system includes strain gauge pressure detector 3, wireless transmitter and diagnosis alarm unit.
Wherein, the strain type pressure detector 3 and the handle bolt 1 are arranged one-to-one; the strain type pressure detector 3 collects the pretightening force of each fastening bolt 1 in real time; the strain type pressure detector 3 is a gasket type pressure sensor and comprises a gasket body 3-1 and a strain gauge 3-2, wherein the gasket body 3-1 is sleeved on the handle bolt 1 and is positioned between the nut 2 and the flange surface 4 of the top cover; during installation, a gasket body 3-1 of the strain type pressure detector 3 is sleeved on a top cover handle bolt 1, and a nut 2 is sleeved on a screw rod of the handle bolt 1; a gasket body 3-1 which comprises a central hole from the center to the edge in sequence3-1-3 parts of inner ring surface 3-1-1 parts of transition groove 3-1-4 parts of outer ring surface 3-1-2 parts of inner ring surface; the upper surface of the inner ring surface 3-1-1 protrudes out of the upper surface of the outer ring surface 3-1-2, the outer ring surface 3-1-2 is connected with the side wall of the inner ring surface 3-1-1, and the upper surface of the inner ring surface 3-1-1 is subjected to the pretightening force F of the fastening bolt1(ii) a The lower surface of the outer ring surface 3-1-2 protrudes beyond the lower surface of the inner ring surface 3-1-1, and the lower surface of the outer ring surface 3-1-2 is subjected to the reaction force F of the flange surface of the top cover2(ii) a The transition groove 3-1-4 is arranged at the lower side of the gasket body 3-1 and is arranged between the side wall of the outer annular surface 3-1-2 and the side wall of the inner annular surface 3-1-1; the strain gauge 3-2 is arranged at the bottom of the transition groove 3-1-4; the strain gauges are arranged in a plurality and are uniformly distributed along the circumferential direction of the gasket body, preferably, the strain gauge 3-2 is adhered to the bottom of the transition groove in a symmetrical mode, and the problem that the load of the bolt 1 cannot be monitored due to the fact that the bolt 1 is not on the same plane when the bolt 1 is pressed on the inner ring surface 3-1-1 of the gasket body 3-1 is solved; the plurality of strain gauges are connected by adopting an equal arm bridge measuring circuit.
The gasket body forms a shear beam structure by arranging the transition groove, a hydraulic tensiometer is used for stretching a screw rod with the elongation of 1.4mm during installation, then a manual driving lever is inserted into a shifting hole of a nut to screw the nut until the nut is screwed, then the hydraulic tensiometer is removed, so that the upper surface of the gasket body 3-1 is stressed by vertical downward force, namely, the pretightening force F of a closing bolt1(ii) a The lower surface of the gasket body 3-1 is subjected to a vertically upward force, i.e., a reaction force F of the flange face of the top cover2(ii) a Pretightening force F of handle bolt1Reaction force F with flange surface of top cover2Acting on two ends of the shear beam respectively, and generating downward stroke quantity by the inner ring surface 3-1-1, thereby generating axial deformation at the bottom of the transition groove; the strain gauge is adhered to the bottom of the transition groove, so that the strain gauge is axially deformed along with the bottom of the groove, and the calculation formula is as follows:
Figure BDA0003193879710000061
wherein epsilon is the strain generated by the strain gauge; f1The upper surface of the inner ring surface is subjected to the pre-tightening force of the fastening bolt; s1Is the cross-sectional area of the inner ring surface；E1The material elastic modulus of the gasket body;
the characteristics of the strain gauge are as follows: is a sensing element that can convert changes in strain on a mechanical member into changes in resistance; therefore, the strain gauge can convert the strain epsilon into relative resistance change, and then the change of the resistance is converted into the change of voltage through the equal arm bridge measuring circuit, and the specific formula is as follows:
Figure BDA0003193879710000062
wherein U is the output voltage of the equal arm bridge; k is the sensitivity coefficient of the strain gauge; u shapeabIs a potential source of an equal arm bridge measuring circuit.
According to the two calculation formulas, the output voltage U of the equal-arm bridge and the pretightening force F of the tightening bolt can be obtained1A linear relationship therebetween; when the bolt becomes loose, i.e. F1And the output voltage U is reduced, so that the bolt looseness is monitored.
The wireless transmitter 5 transmits signals of the strain type pressure detector 3 to the diagnosis and alarm unit, a lead interface 3-1-5 is arranged on the side wall of the strain type pressure detector 3, and the wireless transmitter 5 is connected with the lead interface 3-1-5 through an analog signal wire 6; a wireless transmitter 5 including a housing and a wireless transmission module; the shell is provided with a magnet 5-1, and the wireless transmitter 5 is installed on the top cover through the magnet 5-1, so that the characteristic of convenient installation is favorable for rapid on-site deployment and use; the wireless transmitter 5 further comprises a battery, and the battery supplies power to the wireless transmission module and the strain type pressure detector; preferably, the signal of the strain type pressure detector is in millivolt level, and the wireless transmitter 5 adopts a constant current source to supply power to the strain type pressure detector, so that noise interference can be reduced, and the resolution of the analog signal can be improved.
The wireless transmission module comprises an LoRa communication module and a microcontroller, the LoRa communication module is low in cost, high in safety and long in transmission distance, and due to the fact that the power consumption of the LoRa communication module is large, the microcontroller is arranged, and the wireless transmission module performs wireless transmission work by adopting a timing and bolt load change calculation dual-standard strategy, so that electric energy is reasonably used; the control method of the microcontroller to the LoRa communication module is as follows:
step 1, setting a pre-tightening force change alarm threshold value delta F and a strain type pressure detector acquisition time interval T according to requirements1The communication heartbeat interval with the diagnosis alarm unit is T2。
Step 2, recording the data of the pretightening force of the closed bolt at the current moment of the strain type pressure detector, and recording the data as Ft。
Step 3, calculating the pretightening force change value, and recording the pretightening force change value as delta FtThe specific calculation formula is as follows:
ΔFt＝Ft-Ft-1wherein F ist-1The data of the pretightening force of the fastening bolt at the previous moment.
Step 4, if delta FtIf the value is larger than or equal to delta F, the step 5 is skipped when the pre-tightening force change alarm threshold value is reached, otherwise, the step 6 is skipped.
Step 5, immediately starting the LoRa communication module and sending an alarm value delta FtAnd FtTo a diagnostic alarm unit.
Step 6, calculating whether the time reaches the acquisition time interval T of the strain type pressure detector1And if so, jumping to the step 7, otherwise, continuing to the step 6.
Step 7, calculating whether the time reaches the communication heartbeat interval T2And if so, skipping to the step 8, otherwise, skipping to the step 2.
Step 8, immediately starting the LoRa module and sending the load F at the current momenttAnd (5) going to a diagnosis alarm unit, and skipping to the step 1.
The flow of the water turbine top cover bolt looseness detection system is as follows: the strain type pressure detector sends analog voltage to the wireless transmission module through an analog signal wire, a signal amplifying circuit is arranged in the wireless transmission module, the wireless transmission module is connected with a signal conditioning circuit after signal amplification, and finally the signal conditioning circuit is input to an A/D conversion module in the microcontroller, analog voltage digitization is realized after A/D conversion, and finally the analog voltage digitization is sent to a diagnosis and alarm unit through a LoRa antenna; the looseness to hydraulic turbine top cap bolt has been realized detecting and reporting to the police, and strain type pressure detector can quantitative detection bolt pretightning force simultaneously, can detect whether 80 of water pump turbine unit closes the pretightning force unanimous when the bolt is first installed, need not artifical detection and analysis warning.
The strain type pressure detector adopts a gasket type pressure sensor, and in order to ensure the sensitivity and accuracy of detection, the bottom of the transition groove generates axial deformation change which is generated by the change of bolt pretightening force; the gasket body is directly contacted with the flange surface of the top cover, so that once the gasket body dents on the flange surface of the top cover, the accuracy of the detection of axial displacement deformation can be influenced; the invention discloses a design method of a water turbine top cover bolt looseness detector, which is used for calculating the size of a gasket body which ensures that no dent deformation is caused on a flange surface, meeting the design requirement and ensuring the detection accuracy, and the appearance of a water turbine top cover is smooth and does not influence the working performance of the water turbine top cover, and comprises the following specific steps:
step 1, calculating the initial pretightening force of the closing bolt, and recording the initial pretightening force as F, wherein the unit is T; the specific calculation formula is as follows:
Figure BDA0003193879710000081
wherein, L is the effective length of closing the bolt, the unit: mm; e is the elastic modulus of the bolt material, unit: n/mm2(ii) a Elongation value of the fastening bolt at initial pretension of delta L, unit: mm; a is the cross-sectional area of the fastening bolt, unit: mm is2(ii) a According to the numerical values in the concrete pump turbine model, Δ L is 1.4mm, the effective length L of the joint bolt is 583mm, the elastic modulus E of the joint bolt material 34Cr2Ni2Mo is 221000, and the effective diameter of the joint bolt is 112mm, so that F is 522.6T.
And 2, looking up a table to obtain the yield strength of the flange surface of the top cover, which is recorded as P and has the unit of MPa, according to the material of the flange surface of the top cover, wherein the material of the flange surface is Q345B according to the numerical value in the specific water pump turbine model, and the yield strength P is 285 MPa.
Step 3, calculating the outside of the gasket bodyThe minimum contact area of the ring surface and the flange surface of the top cover is marked as S and the unit is mm2(ii) a The specific formula is as follows:
p is F/S; substituting specific values to obtain S-17970 mm2。
Step 4, calculating the radius of the outer ring surface of the gasket body, the numerical value of the radius of the inner ring surface of the gasket body and the numerical value standard of the width of the transition groove, wherein the radius of the outer ring surface is set as R, and the unit is mm; the radius of the inner ring surface is set as r, and the unit is mm; the width of the transition groove is set as w, and the unit is mm; the concrete formula is as follows:
S≤π(R2-(r+w)2)。
and 5, determining the values of the radius of the outer ring surface and the radius of the inner ring surface according to the center distance of every two fastening bolts and the distance from the center shaft of the fastening bolt to the edge of the assembly part and the width of the strain gauge in combination with the formula in the step 4, and determining the value of the width of the transition groove.
In the embodiment, the gasket body is made of 40Cr alloy steel, and a table look-up shows that the yield strength of the 40Cr alloy steel is 800MPa, and because the gasket needs to bear the initial pre-tightening force of 522.6T, the downward stroke quantity generated by the inner ring surface 3-1-1 when the initial pre-tightening force is borne can be determined according to the values of the radius of the outer ring surface, the radius of the inner ring surface and the width of the transition groove, and is marked as D; the distance from the bottom surface of the inner ring surface to the flange surface of the top cover is greater than D; the height of the top surface of the inner ring surface protruding out of the top surface of the outer ring surface is equal to the distance from the bottom surface of the inner ring surface to the flange surface of the top cover.
The above-mentioned embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention, and any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention; accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (7)

1. A water turbine top cover bolt looseness detecting system is characterized in that the water turbine top cover bolt looseness detecting system comprises a strain type pressure detector, a wireless transmitter and a diagnosis and alarm unit, wherein the water turbine comprises a top cover and a seat ring, and the top cover and the seat ring are fixedly connected through a plurality of handle bolts and corresponding nuts; wherein, the strain type pressure detector and the handle bolt are arranged in a one-to-one manner; acquiring the pretightening force of each fastening bolt in real time by a strain type pressure detector; the strain type pressure detector is of a gasket type and comprises a gasket body and a strain gauge; the gasket body is sleeved on the handle bolt and positioned between the nut and the flange surface of the top cover; the gasket body sequentially comprises a central hole, an inner ring surface, a transition groove and an outer ring surface from the center to the edge; wherein, the stressed side of the inner ring surface protrudes out of the outer ring surface, and the outer ring surface is connected with the side wall of the inner ring surface; on the non-stressed side of the inner ring surface, the outer ring surface protrudes out of the inner ring surface, and the transition groove is formed between the side wall of the outer ring surface and the side wall of the inner ring surface; the strain gauge is arranged at the bottom of the transition groove; the plurality of strain gauges are uniformly distributed along the circumferential direction of the gasket body;
the wireless transmitter transmits the signal of the strain gauge pressure detector to the diagnosis and alarm unit;
the diagnosis alarm unit is in communication connection with the wireless transmitter and is used for acquiring real-time detection data of the strain type pressure detector through the wireless transmitter, judging the loosening failure condition of the combined bolt according to the real-time detection data, acquiring a loosening failure diagnosis result of the combined bolt and generating an alarm signal when the combined bolt fails.
2. The water turbine roof bolt looseness detection system of claim 1, wherein an upper surface of said inner ring surface is subjected to a pretension force of a fastening bolt; the lower surface of the outer ring surface is subjected to the reaction force of the flange surface of the top cover; under the action of the pretightening force of the bolt and the reaction force of the flange surface of the top cover, the transition groove deforms; the strain gauge is adhered to the bottom of the transition groove, and the plurality of strain gauges are connected through an equal-arm bridge measuring circuit.
3. The water turbine roof bolt looseness detection system of claim 1, wherein said wireless transmitter is connected to said strain gauge pressure detector by an analog signal line; the wireless transmitter comprises a shell and a wireless transmission module; wherein, be provided with magnet on the shell, wireless transmitter passes through magnet is installed on the top cap.
4. The water turbine roof bolt looseness detection system of claim 3, wherein the wireless transmission module comprises a LoRa communication module and a microcontroller, and the control method of the LoRa communication module by the microcontroller is as follows:
step 1, setting a pre-tightening force change alarm threshold value delta F and a strain type pressure detector acquisition time interval T according to requirements1The communication heartbeat interval with the diagnosis alarm unit is T2；
Step 2, recording the data of the pretightening force of the closed bolt at the current moment of the strain type pressure detector, and recording the data as Ft；
Step 3, calculating the pretightening force change value, and recording the pretightening force change value as delta FtThe specific calculation formula is as follows:
ΔFt＝Ft-Ft-1wherein F ist-1The pre-tightening force data of the fastening bolt at the previous moment;
step 4, if delta FtIf the value is larger than or equal to delta F, when the pre-tightening force change alarm threshold value is reached, jumping to the step 5, otherwise, jumping to the step 6;
step 5, immediately starting the LoRa communication module and sending an alarm value delta FtAnd FtTo a diagnostic alarm unit;
step 6, calculating whether the time reaches the acquisition time interval T of the strain type pressure detector1If yes, jumping to the step 7, otherwise, continuing to the step 6;
step 7, calculating whether the time reaches the communication heartbeat interval T2If yes, skipping to step 8, otherwise skipping to step2；
Step 8, immediately starting the LoRa module and sending the load F at the current momenttAnd (5) going to a diagnosis alarm unit, and skipping to the step 1.
5. The hydraulic turbine roof bolt looseness detection system of claim 3, wherein said wireless transmitter further comprises a battery, said battery powering said wireless transmission module and said strain gauge pressure detector.
6. A design method of a water turbine head bolt looseness detector, the water turbine head bolt looseness detector comprising the strain type pressure detector of claim 1; the method is characterized by comprising the following specific steps:
step 1, calculating the initial pretightening force of the closing bolt, and recording the initial pretightening force as F, wherein the unit is T;
step 2, looking up a table to obtain the yield strength of the flange surface of the top cover according to the material of the flange surface of the top cover, and recording the yield strength as P, wherein the unit is MPa;
step 3, calculating the minimum contact area of the outer ring surface of the gasket body and the flange surface of the top cover, and recording the minimum contact area as S, wherein the unit is mm2(ii) a The specific formula is as follows:
P＝F/S；
step 4, calculating numerical value standards of the radius of the outer ring surface of the gasket body and the radius of the inner ring surface of the gasket body, wherein the radius of the outer ring surface is set as R, and the unit is mm; the radius of the inner ring surface is set as r, and the unit is mm; the width of the transition groove is set as w, and the unit is mm; the concrete formula is as follows;
S≤π(R2-(r+w)2)；
and 5, determining the values of the radius of the outer ring surface and the radius of the inner ring surface according to the center distance of every two fastening bolts and the distance from the center shaft of the fastening bolt to the edge of the assembly part and the width of the strain gauge in combination with the formula in the step 4, and determining the value of the width of the transition groove.
7. The design method of the water turbine roof bolt looseness detector of claim 6, wherein in the step 1, the initial pretightening force of the fastening bolt is calculated and set to be F, the unit is T, and the specific calculation formula is as follows:
Figure FDA0003193879700000021
wherein, L is the effective length of closing the bolt, the unit: mm; e is the elastic modulus of the bolt material, unit: n/mm2(ii) a Δ L-elongation value of the closure bolt at initial pretension, unit: mm; a is the cross-sectional area of the fastening bolt, unit: mm is2。
CN202110885287.0A 2021-08-03 2021-08-03 Water turbine top cover bolt looseness detection system and design method of detector Withdrawn CN113482835A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114659773A (en) * 2022-03-21 2022-06-24 华能西藏雅鲁藏布江水电开发投资有限公司 Machine set top cover bolt fracture monitoring method and monitoring system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114659773A (en) * 2022-03-21 2022-06-24 华能西藏雅鲁藏布江水电开发投资有限公司 Machine set top cover bolt fracture monitoring method and monitoring system

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Application publication date: 20211008