CA1143064A - Apparatus and method for measuring the crevice gap clearance in a heat exchanger - Google Patents
Apparatus and method for measuring the crevice gap clearance in a heat exchangerInfo
- Publication number
- CA1143064A CA1143064A CA000363810A CA363810A CA1143064A CA 1143064 A CA1143064 A CA 1143064A CA 000363810 A CA000363810 A CA 000363810A CA 363810 A CA363810 A CA 363810A CA 1143064 A CA1143064 A CA 1143064A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- measuring
- clearance
- acceleration
- tube support
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Monitoring And Testing Of Nuclear Reactors (AREA)
Abstract
APPARATUS AND METHOD FOR MEASURING
THE CREVICE GAP CLEARANCE IN A HEAT EXCHANGER
Abstract of the Disclosure Apparatus and method for measuring the crevice gap clearance between the tubes and tube supports in a heat exchanger includes setting the tube into vibration until it impacts against the tube support plate and determining by accelerometers mounted on the tube the distance the tube has moved.
THE CREVICE GAP CLEARANCE IN A HEAT EXCHANGER
Abstract of the Disclosure Apparatus and method for measuring the crevice gap clearance between the tubes and tube supports in a heat exchanger includes setting the tube into vibration until it impacts against the tube support plate and determining by accelerometers mounted on the tube the distance the tube has moved.
Description
3~6~
Background of the Invention The present invention is directed to an apparatus and method for measuring the crevice gap clearance in a heat exchanger and more particularly for steam generators used in nuclear power plants.
Currently ~any steam generators us~d in nuclear power plants suffer corrosion problems in the gap between a heat exchange tube and a tube support plate. Buildup of these corrosion products has many bad side effects including denting of the tube, or constricting it to a smaller dia-meter which causes cracks and developing leaks. Thus in order to obtain an early warning of the onset of denting, etc. it is desirable to measure the clearance between the tube outer diameter and the tube support plate. Ultrasonic and eddy current techniques have been attempted but have not proved satisfactory.
Moreover, it may also be possible to chemically clean or reverse the buildup of corrosion. Thus a technique for indicating when chemical cleaning should be applied and thereafter measuring the effect of such chemical cleaning is also highly desirable.
Objects and Summary of the Invention It is, therefore, a general object of the present invention to provide a method for measuring the crevice gap clearance in a heat exchanger.
It is a more specific object to provide a method and also apparatus which is specifically applicable to the steam generators of nuclear type power plants.
It is yet another object of the invention to provide a method which is nondestructive in nature.
Background of the Invention The present invention is directed to an apparatus and method for measuring the crevice gap clearance in a heat exchanger and more particularly for steam generators used in nuclear power plants.
Currently ~any steam generators us~d in nuclear power plants suffer corrosion problems in the gap between a heat exchange tube and a tube support plate. Buildup of these corrosion products has many bad side effects including denting of the tube, or constricting it to a smaller dia-meter which causes cracks and developing leaks. Thus in order to obtain an early warning of the onset of denting, etc. it is desirable to measure the clearance between the tube outer diameter and the tube support plate. Ultrasonic and eddy current techniques have been attempted but have not proved satisfactory.
Moreover, it may also be possible to chemically clean or reverse the buildup of corrosion. Thus a technique for indicating when chemical cleaning should be applied and thereafter measuring the effect of such chemical cleaning is also highly desirable.
Objects and Summary of the Invention It is, therefore, a general object of the present invention to provide a method for measuring the crevice gap clearance in a heat exchanger.
It is a more specific object to provide a method and also apparatus which is specifically applicable to the steam generators of nuclear type power plants.
It is yet another object of the invention to provide a method which is nondestructive in nature.
2 '~
.,. - ~ `'~
~ 43q364 ``:`
`':`
In accordance with the above objects there is ;~ provided a method of measuring the crevice gap clearance between a tube and tube support in heat exchangers. The tube is vibrated in proximi~y to the tube s~pport and the acceleration monitored in the tube support region. The clearance is determined from such monitored acceleration.
Alternatively from an apparatus standpoint there is provided an apparatus for measuring the crevice gap clearance between a tube and a tube support in heat ex-changers. An elongated unitary structure is inserted in the ;.~
tube which carries means for setting the tube into vibratory motion in proximity to the tube support and means to sense ,, the acceleration of the vibratory motion. ~leans are also provided for processing the sensed acceleration to determine the clearance.
; Brief Description of the Drawings Figureil is a cross-sectional view illustrating a , steam generator;
Figure 2 is a greatly enlarged cross-sectional detailed view of Figure 1 showing tubes passing through a tube support plate;
Figure 3 is a simplified perspective view il-~' lustrating the present invention;
Figure 4 is a waveform characteristic useful in - 2S understanding the present invention;
Figure 5 is a partially cross-sectional broken away view of apparatus used in practicing the present '` invention;
- Figure 6 is a block diagram embodying the present invention;
.
, ` -3-Figures 7A through 7F are oscilloscope patterns useful in understanding the present invention;
Figuxe 8 is a graph;
Figures 9A and 9B are spectrum analysis plots; and Figure 10 is a lissajous figure.
Detailed Description o~ the the Preferred Embodiments Figure 1 illustrates a typical U-bend steam generator configuration. The primary reactor coolant inlet of heated fluid from the nuclear reactor is at 10 and the outlet is at 11. Three pairs of U-bend tubes 12 are indica-ted which are supported by horizontal plates 13. Feedwater from a condenser enters the generator at 14, is heated by the coolant circulating through the tubes 12, and exits as steam to the turbine at 16. In summary, Figure 1 illustrates a typical saturated steam generator used in nuclear power generation.
Figure 2 illustrates a portion of a support plate 13 having holes 13' through which tubes 12 pass. As discus-sed above corrosion tends to form at these points. Figure 3 illustrates in more graphic form ~igure 2 showing the support plate 13 with a tube 12. However, in accordance with the invention there ls illustrated as mounted within the tube 12 a vibrator 17 along with accelerometers 18. The accelero-meter has an axis of rotation shown as 17' which is perpendi-2~ cular to the tube axis. However, this could alternativelybe parallel to the tube axis. The vibrator 17 includes an eccentric mass 17a which thus forms an eccentric weight shaker which will set tube 12 into vibration when actuated either by an associated electric motor or an air turbine.
Accelerometers 18 are mounted in the tube also and would typically be located at a 9~ angle to each other.
~143~6~
Figure 4 illustrates operation of the invention where when the tube is set into vibration the accelerometer signal amplitude "A" increases until a strike occurs with the support plate 13. At this point by determin2tion of the frequency and the use of t~e accelerometer signal amplitude a crevice gap may be determined by the followin~ equation.
A
Crevice Gap = (2~fS)2 where fs is the strike frequency.
The actual apparatus ~or retaining the vibrator 17 and the accelerometers 18 in a unitary structure is il-lustrated in Figure S. Here there is an elongated bullet-shaped shell 21 which has a diameter smaller than the tube 12 which is basically constructed at its tip 22 of rigid hard rubber or silicon. Mounted at the tip end are the accelerometers 18. In addition, there is eddy current unit 23 which senses the large metal mass of support plate 13 (see Figure 3) to determine when the accelerometers 18 and the vibrator 17 are in proximity to the tube support plate.
In other words, the entire structure 21 is passed into the tube until in proximity to a tube support plate. Alterna-tively, of course, simple measurement techniqùes could be utilized.
Vibrator 17 is illustrated with a motor 24 and, of course, the eccentric mass 17a. Appropriate lead wires indicated at 26 are provided. In addition to retain the unit 21 and the tube at the proper location there are a pair of friction pads 27a,b which are driven against the sides of the tube by a pne~matic cylinder 28.
~L~gL3~6~a Figure 6 illustrates the X and Y accelerometers 18a and l~b and the associated electronics to analyze the output signals of the accelerometers. These include a pair of low pass filters 31a,b which filter out high frequency components caused by the impact of the tube with its tube support. In other words, it is the low frequency components which contain information which is of interest. The outputs of the filters may be applied either to a cathode ray tube 32 and specifically the X and Y inputs to form a lissajous figure or pattern and/or in addition, a spectrum analyzer unit 33. Typical outputs for lissajous figures for a CRT
are illustrated in Figures 7A through 7F with the clearances and frequencies and relative scale of the CRT given. Note that these figures are produced by several repetitions and thus are produced by storage oscilloscope.
Figure 8 is a plot of Figures 7A through 7F and specifically the squares indicating clamped data points. In other words, when these data points were taken an experi-mental tube was clamped at its two ends and allowed to vibrate against a central support plate. The horizontal axis of the graph of Figure 8 illustrates the actual clear-ance between the tube and the tube support plate and the vertical axis is measured clearance in mils. Obviously the 45 line 34 would be the optimum relationship between actual and measured clearance. On an experimental basis the curves of Figures 7A through 7F were plotted along with the diamond-shaped points where a 10 mil clearance was provided at the adjacent supports; the circle is where they were free. The resulting dashed line 36 illustrates the accuracy of the method in that a constant correction could be applied. The ~ L3~6q~
data points of Figure 8 were actually obtained by measuring on the polar coordinate basis Figures 7A through 7F and effectively taking the maximum points.
Figures 9A and 9B illustrate an alternative to the lissajous pattern technique and are spectrum analysis plots of Figure 7C. This is accon~plished by the spectrum analyzer 33 of Figure 6 and the appropriate dat~ points ~or vertical and horizontal responses are indicated to yield data points similar to those of Figure 8.
Another experimental lissajous pattern is il-lustrated in Figure 10 which is the response of a tube impacting on the center support plate with excitation at 120 Hz with 0.4# force. Here the high frequency components caused by the impact of a tube with the tube support are clearly shown and are filtered out by the appropriate filters 31a,b of Figure 6. It is obvious that the lissajous figures are, of course, necessarily ~ormed by time varying monitored acceleration signals which have a phase difference between them because of their orthogonal displacement.
From an equipment point of view the accelerometers may be of the type sold under the trademark BOLT, BERANEK
and NEW~N Model 501. These accelerometers have a flat frequency response from 2 Hz to 50,000 Hz and the sensitivity of 100 mv per g.
Thus an effective technique for measuring crevice gap has been provided. It is applicable to all types of heat exchangers including condensers and transformer coolers as well as steam generators~
.,. - ~ `'~
~ 43q364 ``:`
`':`
In accordance with the above objects there is ;~ provided a method of measuring the crevice gap clearance between a tube and tube support in heat exchangers. The tube is vibrated in proximi~y to the tube s~pport and the acceleration monitored in the tube support region. The clearance is determined from such monitored acceleration.
Alternatively from an apparatus standpoint there is provided an apparatus for measuring the crevice gap clearance between a tube and a tube support in heat ex-changers. An elongated unitary structure is inserted in the ;.~
tube which carries means for setting the tube into vibratory motion in proximity to the tube support and means to sense ,, the acceleration of the vibratory motion. ~leans are also provided for processing the sensed acceleration to determine the clearance.
; Brief Description of the Drawings Figureil is a cross-sectional view illustrating a , steam generator;
Figure 2 is a greatly enlarged cross-sectional detailed view of Figure 1 showing tubes passing through a tube support plate;
Figure 3 is a simplified perspective view il-~' lustrating the present invention;
Figure 4 is a waveform characteristic useful in - 2S understanding the present invention;
Figure 5 is a partially cross-sectional broken away view of apparatus used in practicing the present '` invention;
- Figure 6 is a block diagram embodying the present invention;
.
, ` -3-Figures 7A through 7F are oscilloscope patterns useful in understanding the present invention;
Figuxe 8 is a graph;
Figures 9A and 9B are spectrum analysis plots; and Figure 10 is a lissajous figure.
Detailed Description o~ the the Preferred Embodiments Figure 1 illustrates a typical U-bend steam generator configuration. The primary reactor coolant inlet of heated fluid from the nuclear reactor is at 10 and the outlet is at 11. Three pairs of U-bend tubes 12 are indica-ted which are supported by horizontal plates 13. Feedwater from a condenser enters the generator at 14, is heated by the coolant circulating through the tubes 12, and exits as steam to the turbine at 16. In summary, Figure 1 illustrates a typical saturated steam generator used in nuclear power generation.
Figure 2 illustrates a portion of a support plate 13 having holes 13' through which tubes 12 pass. As discus-sed above corrosion tends to form at these points. Figure 3 illustrates in more graphic form ~igure 2 showing the support plate 13 with a tube 12. However, in accordance with the invention there ls illustrated as mounted within the tube 12 a vibrator 17 along with accelerometers 18. The accelero-meter has an axis of rotation shown as 17' which is perpendi-2~ cular to the tube axis. However, this could alternativelybe parallel to the tube axis. The vibrator 17 includes an eccentric mass 17a which thus forms an eccentric weight shaker which will set tube 12 into vibration when actuated either by an associated electric motor or an air turbine.
Accelerometers 18 are mounted in the tube also and would typically be located at a 9~ angle to each other.
~143~6~
Figure 4 illustrates operation of the invention where when the tube is set into vibration the accelerometer signal amplitude "A" increases until a strike occurs with the support plate 13. At this point by determin2tion of the frequency and the use of t~e accelerometer signal amplitude a crevice gap may be determined by the followin~ equation.
A
Crevice Gap = (2~fS)2 where fs is the strike frequency.
The actual apparatus ~or retaining the vibrator 17 and the accelerometers 18 in a unitary structure is il-lustrated in Figure S. Here there is an elongated bullet-shaped shell 21 which has a diameter smaller than the tube 12 which is basically constructed at its tip 22 of rigid hard rubber or silicon. Mounted at the tip end are the accelerometers 18. In addition, there is eddy current unit 23 which senses the large metal mass of support plate 13 (see Figure 3) to determine when the accelerometers 18 and the vibrator 17 are in proximity to the tube support plate.
In other words, the entire structure 21 is passed into the tube until in proximity to a tube support plate. Alterna-tively, of course, simple measurement techniqùes could be utilized.
Vibrator 17 is illustrated with a motor 24 and, of course, the eccentric mass 17a. Appropriate lead wires indicated at 26 are provided. In addition to retain the unit 21 and the tube at the proper location there are a pair of friction pads 27a,b which are driven against the sides of the tube by a pne~matic cylinder 28.
~L~gL3~6~a Figure 6 illustrates the X and Y accelerometers 18a and l~b and the associated electronics to analyze the output signals of the accelerometers. These include a pair of low pass filters 31a,b which filter out high frequency components caused by the impact of the tube with its tube support. In other words, it is the low frequency components which contain information which is of interest. The outputs of the filters may be applied either to a cathode ray tube 32 and specifically the X and Y inputs to form a lissajous figure or pattern and/or in addition, a spectrum analyzer unit 33. Typical outputs for lissajous figures for a CRT
are illustrated in Figures 7A through 7F with the clearances and frequencies and relative scale of the CRT given. Note that these figures are produced by several repetitions and thus are produced by storage oscilloscope.
Figure 8 is a plot of Figures 7A through 7F and specifically the squares indicating clamped data points. In other words, when these data points were taken an experi-mental tube was clamped at its two ends and allowed to vibrate against a central support plate. The horizontal axis of the graph of Figure 8 illustrates the actual clear-ance between the tube and the tube support plate and the vertical axis is measured clearance in mils. Obviously the 45 line 34 would be the optimum relationship between actual and measured clearance. On an experimental basis the curves of Figures 7A through 7F were plotted along with the diamond-shaped points where a 10 mil clearance was provided at the adjacent supports; the circle is where they were free. The resulting dashed line 36 illustrates the accuracy of the method in that a constant correction could be applied. The ~ L3~6q~
data points of Figure 8 were actually obtained by measuring on the polar coordinate basis Figures 7A through 7F and effectively taking the maximum points.
Figures 9A and 9B illustrate an alternative to the lissajous pattern technique and are spectrum analysis plots of Figure 7C. This is accon~plished by the spectrum analyzer 33 of Figure 6 and the appropriate dat~ points ~or vertical and horizontal responses are indicated to yield data points similar to those of Figure 8.
Another experimental lissajous pattern is il-lustrated in Figure 10 which is the response of a tube impacting on the center support plate with excitation at 120 Hz with 0.4# force. Here the high frequency components caused by the impact of a tube with the tube support are clearly shown and are filtered out by the appropriate filters 31a,b of Figure 6. It is obvious that the lissajous figures are, of course, necessarily ~ormed by time varying monitored acceleration signals which have a phase difference between them because of their orthogonal displacement.
From an equipment point of view the accelerometers may be of the type sold under the trademark BOLT, BERANEK
and NEW~N Model 501. These accelerometers have a flat frequency response from 2 Hz to 50,000 Hz and the sensitivity of 100 mv per g.
Thus an effective technique for measuring crevice gap has been provided. It is applicable to all types of heat exchangers including condensers and transformer coolers as well as steam generators~
Claims (5)
1. A method of measuring the crevice gap clearance between a tube and a tube support in heat exchangers and the like comprising the following steps: vibrating such tube in proximity to said tube support; monitoring the acceleration of such tube in the tube support region; and determining from such monitored acceleration said clearance.
2. A method as in Claim 1 where said determination is made by the step of processing two time varying monitored acceleration signals having a phase difference and forming a lissajous pattern.
3. A method as in Claim 1 where said determination is made by a spectral analysis of said monitored acceler-ation.
4. Apparatus for measuring the crevice gap clear-ance between a tube and a tube support in heat exchangers and the like comprising: an elongated unitary structure insertable in such tube and carrying means for setting such tube into vibratory motion in proximity to said tube support and carrying means for sensing the acceleration of such vibratory motion; and means for processing said sensed acceleration to determine said clearance.
5. Apparatus as in Claim 4 together with eddy current sensor carried by said unitary structure for sensing the proximity to said tube support.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000363810A CA1143064A (en) | 1980-10-31 | 1980-10-31 | Apparatus and method for measuring the crevice gap clearance in a heat exchanger |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000363810A CA1143064A (en) | 1980-10-31 | 1980-10-31 | Apparatus and method for measuring the crevice gap clearance in a heat exchanger |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1143064A true CA1143064A (en) | 1983-03-15 |
Family
ID=4118325
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000363810A Expired CA1143064A (en) | 1980-10-31 | 1980-10-31 | Apparatus and method for measuring the crevice gap clearance in a heat exchanger |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1143064A (en) |
-
1980
- 1980-10-31 CA CA000363810A patent/CA1143064A/en not_active Expired
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