JPH0688758A - Multi-channel type bolt axial force control system - Google Patents

Abstract

PURPOSE:To embody a control system in which operation can be easily done and the measuring accuracy is high by leaving measuring probes to be fitted during bolt axial force measurement by realizing multi-channel. CONSTITUTION:The title is provided with measuring probes 20 fitted on a plurality of bolts 14 and a bolt axial force measuring instrument 40 that sends an input electric signal to the probe 20 and measures the length of the bolt 14 based on the transmitted signal and its corresponded output electric signal of the probe 20 thereafter. Further, it is also provided with a channel selector 30 prepared between the instrument 40 and respective probes 20, by which the instrument 40 can be optionally connected with one of a plurality of measuring probes 20 and the connecting one probe can be changed successively, and a computer 50 that is connected with the instrument 40 and calculates the elongation of the bolt 14 based on the difference of bolt axial force measured values before and after tightening the bolt 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel type bolt axial force management system for measuring and controlling the bolt axial force of a bolt fastening portion in various machines or equipment.

[0002]

2. Description of the Related Art In general, bolt fastening is frequently used to fasten constituent members of various machines and equipments, and these bolt fastening parts are provided with fastening parts for maintaining performance and ensuring safety. Some require bolt axial force management. For example, the flange joints of relatively high-pressure and high-temperature equipment in oil refineries, oil refinery plants, and general chemical plants, manholes of towers and tanks, nozzles, flange joints of heat exchangers or pipes, etc. . Further, it is necessary to control the bolt axial force at the bolt fastening portion also in important parts such as nuclear power equipment, various vehicles, aircraft, and steel structures such as bridges.

As a conventional method for controlling the bolt axial force of this type, for example, a bolt elongation measuring method in which a micrometer or the like is applied to the end portion of the bolt to measure the elongation, or a nut for estimating the elongation of the bolt from the rotation angle of the nut The rotation method is known, but in the former, the amount of elongation of the bolt is very small, and in the latter, it is difficult to set the reference point, so that the accuracy is poor and the working efficiency is low. Also, for large bolts, a control method is adopted in which tension is applied to the bolt from both ends with a nut tensioner, and this tension is removed after rotating the nut, but it requires an expensive device and is troublesome to handle. There was a drawback of this. For example, a nut tightening torque T (T = torque coefficient K × bolt diameter d ×
There is a method of controlling the bolt axial force F) with a torque meter or the like. This management method is based on the idea that the bolt axial force will be constant if the torque is kept constant, but in reality, even if the tightening torque is constant, the deterioration state of the fastening place and the bolt and nut There has been a problem that the bolt axial force varies depending on the deterioration state.

If the above-mentioned problems occur, the dangerous substance, flammable substance, toxic substance, etc. may be leaked due to insufficient tightening force, or the device may be deteriorated or damaged by vibration or the like. Over tightening may damage the equipment. Therefore, recently, as a relatively preferable bolt axial force management system, a system using an ultrasonic axial force meter which measures the elongation of the bolt with high accuracy by ultrasonic waves has been adopted.
This system catches the reflected echo reflected from the other end of the ultrasonic pulse from one end of the bolt with the measuring probe attached to this one end and takes it into the bolt axial force meter. By measuring the difference in propagation time, the elongation of the bolt is measured.

[0005]

However, even in such a bolt axial force management system utilizing ultrasonic waves, since the measuring probe is replaced every time the bolt axial force is measured, the following will be given. There was such a problem. (A) The bolt length as the display value of the ultrasonic axial force meter varies considerably depending on the displacement of the measuring position, especially in the case of a large diameter bolt. This is due to variations in finishing accuracy of the bolt end surface, variation in parallelism between both end surfaces, and difference in ultrasonic path.Therefore, in the method of replacing the measurement probe before and after tightening the bolt, the initial length was measured. There is a high possibility that the positions will be different, and highly accurate measurements cannot be expected.

(B) It is necessary to apply a contact medium (coupling agent: glycerin, water, oil, grease, etc.) having good acoustic characteristics when the ultrasonic waves are incident on the object to be measured (volt). However, if the degree of adhesion (thickness) of this coupling changes due to the pressing force on the bolt end surface of the measurement probe, etc., the measured display value will differ, and if the measurement probe is replaced before and after tightening, the measurement accuracy will decrease. Will end up.

(C) From the above-mentioned point, a certain degree of skill is required for measurement of actual equipment and facilities, which hinders easy control of bolt axial force. (D) When a plurality of bolts are used to fasten at one place like a flange fastening part, tightening one of the plurality of bolts affects the bolt axial force of the other bolt, so When the axial force is measured, it becomes necessary to repeatedly collect data and tighten the bolt again, and workability is poor.

Therefore, in the present invention, by making the measuring system multi-channel, when measuring the bolt axial force of a plurality of bolts, each measuring probe is left attached from the start of tightening the bolts to the end of the measurement. The purpose is to provide a bolt axial force management system that is easy to work with and that can measure the bolt axial force of multiple bolts with high accuracy. The purpose is to further improve the measurement accuracy by pressing the end face.

[0009]

In order to achieve the above object, the invention according to claim 1 is attached to a plurality of bolts provided in a predetermined fastening portion, respectively, and mechanical vibration is generated according to an input electric signal. And transmits the mechanical vibration to one end of the bolt, converts the ultrasonic waves reflected at the other end of the bolt into an electric signal and outputs the electric signal, and transmits the input electric signal to the measurement probe. A bolt shaft force meter for measuring the length of a bolt based on the transmitted electric signal and an electric signal output from the corresponding measurement probe, and a bolt shaft interposed between the bolt shaft force meter and each measurement probe. The force meter is connected to any one of a plurality of measuring probes, and the channel switching device capable of sequentially switching the connected one measuring probe and the bolt axial force meter are connected to each other. A measuring means for calculating the elongation of the bolt based on the difference between the measured values of the bolt axial force meter before and after the tightening, and the invention according to claim 2 is characterized in that Is attached to the bolt via a predetermined attachment jig, and the attachment jig elastically connects the holding portion that holds the measurement probe, the screw portion that is screwed to the screw of the bolt, and the holding portion and the screw portion. And a connecting portion for connecting to.

[0010]

According to the first aspect of the present invention, the bolt axis force meter is connected to one of the plurality of measuring probes by the channel switch, and the connected one is sequentially switched. The output electric signals of the measuring probe of 1 are sequentially captured by the bolt axial force meter. Therefore, the elongations of a plurality of bolts can be measured at the same time, and each measuring probe can be left attached from the start of bolt tightening to the end of measurement. As a result, the measurement work is facilitated, the elongations of the plurality of bolts are measured with high accuracy, and highly accurate bolt axial force management becomes possible.

According to the second aspect of the present invention, the holding portion for holding the measuring probe and the screwing portion for screwing with the screw of the bolt are elastically connected by the connecting portion, and the measuring probe is fixed to the end surface of the bolt with a constant pressing force. Is pressed by. Therefore, the mounting state of the measurement probe on each bolt becomes stable, and the measurement accuracy is further improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 and 2 are views showing an embodiment of a multi-channel type bolt axial force management system according to the invention described in claims 1 and 2. First, the configuration will be described.

In FIGS. 1 and 2, 10 is a predetermined fastening portion,
For example, a flange fastening portion, and this flange fastening portion 10
Are flanges 11 and 12 provided at opposite ends of two pipes (not shown), a packing (not shown), and a plurality of sets of bolts 14 and nuts 15 for fastening the flanges 11 and 12 with the packing sandwiched therebetween (Fig. Only two sets are shown on behalf of).

Reference numeral 20 denotes a plurality of measuring probes respectively attached to the plurality of bolts 14 via a predetermined coupling agent 21 (for example, glycerin, water, oil or grease is used). Each measurement probe 20 is configured to include a known piezoelectric element section (not shown), and converts an input electric signal (measurement pulse) to this piezoelectric element section into mechanical vibration by the piezo effect and connects it to one end of the bolt 14. While the ultrasonic waves are incident, the ultrasonic waves reflected at the other end of the bolt 14 can be converted into an electric signal and output to the outside.

The measuring probe 20 is attached to the bolt 14 via a predetermined attaching jig 23, respectively.
The mounting jig 23 has a bottomed cylindrical holding portion 23a for accommodating and holding the measurement probe 20, and three claw-shaped screwing portions 23b screwed onto the screw 14a of the bolt 14. The attachment jig 23 is made of an elastic material such as a leaf spring and has a holding portion.
The connecting portion 23c for connecting the 23a and the screwing portion 23b has a holding portion 23.
The measuring probe 20 is pressed against one end surface of the bolt 14 with a predetermined pressing force by elastically connecting the a and the screwed portion 23b.

The connection cables 20a of the plurality of measuring probes 20 are respectively connected to corresponding ones of the plurality of channel terminal portions 30a of the channel switching device 30, and the output terminals of the channel switching device 30 are publicly known. It is connected to the ultrasonic type bolt axial force meter 40. Although not shown, the channel switch 30 includes, for example, a known multiplexer and an amplification correction circuit that prevents a decrease in signal strength, and has a plurality of input terminal portions 30a and one output terminal 30.
b. The channel switcher 30 is configured to select an arbitrary one of the input terminal portions 30a and connect it to the output terminal 30b, and to sequentially switch the connected input terminals under a predetermined condition. That is, a channel switch 30 is interposed between the plurality of measuring probes 20 corresponding to the plurality of bolts 14 and the bolt axial force meter 40, and the channel switch 30 allows any one of the plurality of bolts to be selected.
One measuring probe 20 and the bolt axial force meter 40 are connected, and one connected measuring probe 20 is sequentially connected to the other measuring probe 20 (for example, those adjacent to the flanges 11 and 12 in the circumferential direction). It can be switched. In addition to the multi-channel mode described above, the channel switch 30 has a mode in which only a specific measuring probe 20 is selected and connected to the bolt axial force meter 40 in a one-to-one manner.

Although the bolt axial force meter 40 is not shown in detail,
A measurement that measures the length of the bolt 14 based on a transmission circuit that transmits a measurement pulse as the input electric signal to the measurement probe 20 and the output electric signal (measurement information) of the transmission pulse and the corresponding measurement probe 20. And a circuit.
The length measurement by this measuring circuit is based on the idea that the bolt length L = (sonic velocity in the bolt material) x (pulse reciprocating time / 2). The bolt length L1 before tightening the nut and the bolt after tightening the nut By detecting the length L2 using ultrasonic waves, the elongation of the bolt ΔL = (L2-L1) × (predetermined coefficient) is calculated, and the strain ε of the bolt (the above-mentioned elongation ΔL / initial length L). The stress σ (longitudinal elastic modulus E × strain ε) and bolt axial force F (F = stress σ of bolt × cross-sectional area A of bolt) corresponding to are calculated. The elongation ΔL
The predetermined coefficient for calculating is to correct the influence of the change in sound velocity during measurement before and after tightening.

Reference numeral 50 is a computer connected to the bolt axial force meter 40. The computer 50 is a CP (not shown)
It has a U, a ROM, a RAM, an input / output interface circuit, an auxiliary storage device, and the like, and stores the measurement data in R according to a predetermined control program stored in advance in the ROM.
The value of the stored data is stored in a predetermined file in the AM and the auxiliary storage device, and the value of the stored data is subtracted from the value of the measured data after tightening to correct the temperature and the stress load, and the elongation ΔL of the bolt 14 and the target tightening force. Etc. are calculated. That is, the computer 50 calculates the elongation ΔL of the bolt 14 based on the difference in the measured length of the bolt axial force meter 40 before and after tightening the bolt 14 by tightening the nut 15, and calculates the bolt ΔL of the bolt 14. It is a calculation means for calculating the axial force F.
A printer 60 is connected to the computer 50, and a report document regarding bolt axial force management can be created based on the measurement data processed by the computer 50.

Next, the operation will be described. First, a predetermined key input operation is performed on the computer 50 to start a calculation menu of the optimum tightening force for the bolt tightening location, and the computer 50 causes the predetermined tightening range (stress σ, elongation ΔL, gasket surface pressure) of the bolt 14 to be started. ) Etc. are calculated, and a file for entering measurement data is created.
Next, the target tightening force (bolt elongation ΔL, bolt stress σ, estimated torque T) is determined based on the above calculation result.

Next, when the automatic bolt measurement menu is activated, necessary data is written in the measurement data entry file, and the measurement data entry file is displayed on the CRT display 51, for example. The current elongation (zero) or length of the bolt 14 is displayed with. Then, it is attached to one end surface of the bolt 14 by the attachment jig 23 via the coupling agent 21. At this time, the mounting jig 23 has three claw-shaped threaded portions on the screw 14a of the bolt 14.
By screwing 23b, it is connected to the bolt 14, and the measuring probe 20 is pressed against one end surface of the bolt 14 with a predetermined pressing force.

Measuring probes 20 are respectively attached to the plurality of bolts 14.
Then, the switch (not shown) of the bolt axial force meter 40 is turned on. Then, in this ON state, the bolt axial force meter 40 always generates the measuring pulse at regular intervals. At this time, if the channel switch 30 is in the channel fixing mode, only a specific channel is connected to the bolt axial force meter 40. Therefore, an input electric signal is applied to one measurement probe 20 through the channel switch 30, the measurement probe 20 generates mechanical vibration, and an ultrasonic wave is incident on one end of the bolt 14, and its reflection echo is generated. For example, the bolt axial force meter 40 measures the bolt length from the time difference between the measurement pulse and its reflection echo,
The data is taken into the computer 50, processed, and displayed on the CRT display 51.

On the other hand, when the channel switch 30 is in the multi-channel mode, the terminals of all the channels of the input terminal section 30a are output at a constant time interval (interval) by the signal of the timer circuit attached to the CPU. The connection is sequentially switched to. Therefore, an input electric signal is applied to any one of the measuring probes 20 via the channel switching device 30, and the one measuring probe 20 is sequentially switched, and the switched one measuring probe 20 mechanically changes to the bolt 14. Vibration is incident, the lengths of the plurality of bolts 14 are simultaneously measured from the time difference between the measurement pulse and its reflection echo, and the measurement data are taken into the computer 50, processed, and displayed on the CRT display 51.

In such a state, the computer
50 is the length L before tightening the measured data taken in by bolts.
The measured value of 1 is stored in the file for entering the measured data. As a result, the bolt length L1 before tightening the bolt
The length measurement is completed. Next, the nut 15 is rotated in the tightening direction with a tightening tool such as a spanner, and
14 is tightened.

Next, the bolt length L2 after tightening is measured by the same procedure as described above, and the measured data is loaded into the computer 50. Next, the elongation ΔL of the bolt 14 is calculated based on the values of the bolt length L1 before tightening the nut and the bolt length L2 after tightening the nut, and each measurement is connected to the bolt axial force meter 40 at regular intervals, for example. Corresponding to the signal from the probe 20, the elongation of each bolt 14 is displayed at regular intervals in the form of a pie chart on the CRT display. By monitoring the amount of elongation on the display 51, the stress σ applied to the bolt 14 and the bolt axial force F are managed.

As described above, in the present embodiment, the channel switch 30 sequentially connects the bolt axial force meter 40 to any one of the plurality of measuring probes 20, and the output of the plurality of measuring probes 20 is switched by this channel switching. The electrical signals are sequentially taken into the bolt axial force meter 40 and the elongations of the plurality of bolts 14 are simultaneously measured. Therefore, each measuring probe 20 can be left attached to the bolt 14 from the start of tightening the bolt 14 to the end of the measurement, and the measuring probe can be replaced with another bolt or detached and reinstalled before and after tightening as before. Therefore, the efficiency of the measurement work is significantly improved. Further, since there is no displacement of the mounting position of the measuring probe 20 before and after tightening, the bolt axial force of the plurality of bolts 14 can be measured with high accuracy.

Further, in this embodiment, the mounting jig 23 for holding the measuring probe 20 is such that the holding portion of the measuring probe 20 and the screwed portion to the bolt 14 are elastically connected. The measurement probes 20 are pressed against the bolt end faces with a constant pressing force, the mounting state of the measurement probes 20 on the bolts 14 becomes extremely stable, and the measurement accuracy is improved.

In this embodiment, the elongation of the bolt 14 is monitored to control the bolt axial force. However, the bolt strain and bolt axial force are directly calculated and displayed to perform similar axial force management. You can also Further, in the present embodiment, the nuts 15 are provided at both ends of the bolt 14, but it goes without saying that a combination of a bolt with a bolt head and a nut screwed at one end thereof may be used.

[0028]

According to the first aspect of the invention, the channel switching unit sequentially switches the bolt axial force meter to one of the plurality of measuring probes and connects the same, and the output of the plurality of measuring probes is switched by this channel switching. Since it is possible to capture electrical signals sequentially into the bolt axial force meter, it is possible to measure the elongation of multiple bolts at the same time and leave each measurement probe attached before and after tightening the bolts. It is possible to improve the accuracy of bolt axial force management while facilitating.

According to the second aspect of the present invention, since the mounting jig is such that the holding portion of the measuring probe and the screwing portion to the bolt are elastically connected by the connecting portion, the measuring probe is fixed. The end face of the bolt can be pressed by the pressing force of, and the attachment state of the measurement probe to each bolt can be stabilized, and the measurement accuracy can be further improved.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a multi-channel type bolt axial force management system according to the present invention.

2A and 2B are diagrams showing a configuration of a measurement probe mounting jig of one embodiment, FIG. 2A is a vertical cross-sectional view thereof, and FIG.

[Explanation of symbols]

 10 Flange fastening part (predetermined fastening part) 11, 12 Flange 14 Bolt 15 Nut 20 Measuring probe 30 Channel changer 40 Bolt axial force meter 50 Computer (calculation means)

Claims (2)

[Claims] 1. A plurality of bolts mounted on a predetermined fastening portion, respectively, which generate mechanical vibrations in response to an input electric signal to inject the mechanical vibrations into one end of the bolts, A plurality of measuring probes that convert the ultrasonic waves reflected at the ends into electric signals and output the electric signals, and transmit the input electric signals to the measuring probes, and output the electric signals that have been transmitted and the output electric signals of the corresponding measuring probes. A bolt axial force meter that measures the length of the bolt based on it, and is installed between the bolt axial force meter and each measuring probe, and while connecting the bolt axial force meter to any one of multiple measuring probes, It is connected to a channel switching device that can sequentially switch one of the connected measurement probes and a bolt axial force meter, and the voltameter is determined by the difference between the measured values of the bolt axial force meter before and after tightening the bolt. Multichannel bolt axial force management system characterized by comprising: a calculating means, the calculating the elongation. 2. The measurement probe is attached to a bolt via a predetermined attachment jig, and the attachment jig has a holding portion for holding the measurement probe, a screwing portion screwed with a screw of the bolt, and a holding portion. The multi-channel bolt axial force management system according to claim 1, further comprising a connecting portion that elastically connects the portion and the screwed portion.