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GB2489654A - Inspecting tubes using gamma rays - Google Patents

Inspecting tubes using gamma rays Download PDF

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Publication number
GB2489654A
GB2489654A GB1010030.3A GB201010030A GB2489654A GB 2489654 A GB2489654 A GB 2489654A GB 201010030 A GB201010030 A GB 201010030A GB 2489654 A GB2489654 A GB 2489654A
Authority
GB
United Kingdom
Prior art keywords
gamma
source
pipe
gamma rays
detector
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.)
Withdrawn
Application number
GB1010030.3A
Other versions
GB201010030D0 (en
Inventor
Samir Abdul-Majid Alzaidi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to GB1010030.3A priority Critical patent/GB2489654A/en
Publication of GB201010030D0 publication Critical patent/GB201010030D0/en
Publication of GB2489654A publication Critical patent/GB2489654A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
    • G01N23/203—Measuring back scattering
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B15/00—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons
    • G01B15/02—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons for measuring thickness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/005—Investigating fluid-tightness of structures using pigs or moles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
    • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
    • G01M3/20—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material
    • G01M3/22—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material for pipes, cables or tubes; for pipe joints or seals; for valves; for welds; for containers, e.g. radiators
    • G01M3/222—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material for pipes, cables or tubes; for pipe joints or seals; for valves; for welds; for containers, e.g. radiators for tubes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/38—Investigating fluid-tightness of structures by using light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/36—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry
    • G01T1/362—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry with scintillation detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/10—Different kinds of radiation or particles
    • G01N2223/101—Different kinds of radiation or particles electromagnetic radiation
    • G01N2223/1013—Different kinds of radiation or particles electromagnetic radiation gamma
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/60—Specific applications or type of materials
    • G01N2223/628—Specific applications or type of materials tubes, pipes

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Electromagnetism (AREA)
  • Molecular Biology (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Measurement Of Radiation (AREA)
  • Length-Measuring Devices Using Wave Or Particle Radiation (AREA)

Abstract

A method of inspecting the inside of a pipe or tube (5) based on gamma back-scattering which includes introducing a source (4) of gamma rays into the pipe or tube (5) and providing a gamma detector (2) for counting and analyzing the back-scattered gamma rays. The system includes a light pipe or fibre optic cable 1, photomultiplier tube 9 and electronics 10. A gamma shield 3 is placed between the source 4 and detector 2. The shield 3 prevents gamma rays emitted from source 4 reaching the (scintillating) gamma detector 2 directly. Emitted and back-scattered radiation is indicated by arrows 7 and 8, respectively.

Description

MEASUREMENT TECHNIQUES
Field of the Invention
This invention relates to measurement techniques and is particularly concerned with a method that involves measuring corrosion and erosion in pipes from inside the pipes.
Figure 2 of the accompanying drawings shows bundles of heat exchanger tubes for which periodic inspection is needed after plant shut down to insure adequate performance of the heat exchangers during operation. If the tubes are not in a very good condition, the chance of failure increases during operation.
Other techniques exist for the measurement of corrosion and erosion within heat exchanger tubes, but the current techniques are not very successful because the tubes need to be cleaned very well from inside before inspection for these techniques to work.
It is an object of the present invention to provide measurement method that can be used successfully for clean pipes or dirty pipes as well as for twisted pipes or for pipes that are out of roundness.
Summary of the Invention
According to the present invention there is provided a method of inspecting the inside of a pipe or tube which includes introducing a source of gamma rays into the pipe or tube and providing a gamma detector for measuring and analyzing the back-scattered gamma rays.
A shield may be disposed between the source of gamma rays and the gamma detector.
Spring means may be provided for biasing the source of gamma rays and the gamma detector towards a wall of the pipe or tube. A rotational and translational movement of the system may be introduced.
In an alternative arrangement, the source of gamma rays comprises radioactive material with which the gamma detector material is coated.
Brief Description of the Drawings
Figure 1 is a schematic view showing the incident and back-scattered radiation of a pipe or tube wall, Figure 2 is a pictorial view showing an array of heat exchanger tubes, Figure 3A is a schematic view showing the carrying out of an inspection procedure, in which the gamma detector that is used is a scintillation detector with a light pipe and a photo-multiplier tube (or an electron multiplier or a photodiode), Figures 3B, 4A, 4B, 5A, 5B, 6A and 6B show alternative procedures, Figure 7 shows the output of a multi-channel analyzer, Figures 8A and 8B depict the possible use of sources of different shapes and sizes, Figures 9A and 9B are schematic views showing the carrying out of an inspection procedure in which the source of gamma rays comprises radioactive material surrounding the gamma detector, and Figure 10 shows the output of an electronic counting system of a multi-channel analyzer used in conjunction with the arrangement shown in Figures 8A, 85, 9A and 9B.
Description of the Preferred Embodiments
Referring to Figure 1 above, when gamma rays are caused to be incident on a pipe wall, attenuation takes place. The magnitude of attenuation depends on the energy of the gamma rays and the atomic number and density of the material. The attenuation to distance x within the wall for a parallel gamma ray beam is proportional to: Exp (-px).
where p is the linear attenuation coefficient of the incident rays.
The portion of intensity is scattered due to Compton interaction. The energy of the scattered radiation is always less than that of the incident rays. Scattering takes place from the inside layers of the wall and undergoes higher attenuation in its path back because its energy is lower than that of the primary incident radiation. Radiation, therefore, undergoes double attenuation. Taking a special case of 180 degrees back-scattered radiation, the back-scattered gamma rays at a distance x undergo attenuation proportional to: Exp (-p'x) where p' is the linear attenuation coefficient of the back- scattered rays. The total attenuation of incident as well as back-scattered radiation at a specific distance will be proportional to: Exp [-p + p) x] The amount of back-scattered radiation from a pipe wall will be proportional to the wall thickness T. Back-scattered radiation increases with thickness, sharply at a small thickness T then reaches saturation at high thicknesses. Saturation depends on the gamma ray energy and the atomic number and density of the wall materials.
These phenomena will be used to measure changes of pipe wall thickness due to corrosion. Moreover, a change in wall material such as deposits will change the intensity of scattered rays and, therefore, can be detected.
Referring to Figure 3A, inspection can be made using the back-scattered gamma rays method for the tube 5. The inspection system consists of a radioactive source 4, a gamma shield 3, a scintillation material (detector) 2, a light pipe or a fiber optic cable 1, a photomultiplier tube (PMT) 9 (or any other electron multiplier or a photodiode) and nuclear electronics 1 0. The scintillation material 2, the light pipe or cable 1 and the PMT 9 should be light-tight. The shield 3 prevents gamma rays emitted from the source 4 reaching the scintillation detector 2 directly.
Gamma rays interact with the pipe wall material in such a way that some will scatter back to the scintillation detector 2. The amount of scattered rays is proportional to the wall thickness. Less scattered radiation means less thickness. If corrosion exists in a region of the pipe, the amount of back-scattered radiation from that region is less compared to that from a non-corroded region. The emitted and back-scattered radiation is indicated by the arrows 7 and 8 in Figure 3A.
Scattered gamma rays produce light in the scintillation detector 2 that is transmitted through the light pipe or fiber optic cable 1 to the PMT 9 and from the PMT 9 to the nuclear electronics 10. The nuclear electronics 10 may or may not involve a multi-channel analyzer (MCA). The output from the nuclear electronics 10 can be in the form of electric pulses or an electric current. The total number of pulses or the magnitude of the current is proportional to the wall thickness. The pulse height distribution can be measured by the nuclear electronics 10. If a multi-channel analyzer is used they will show a wide peak, as shown in Figure 7. The area under the peak gives the total number of pulses. If the output is a current it can be measured by a sensitive ammeter.
The detector 2 scans the pipe or tube 5 using a mechanical scanner. Information on the condition of the pipe or tube 5 can then be found. If a thickness change is associated with a deposit on the pipe wall, this can be detected as the interaction, and accordingly the scattered radiation, will differ.
Different Detection Systems Gamma detectors other than scintillation detectors can be used, for example, gas-filled detectors or solid state semi-conductor detectors. In such cases, the light pipe cable and PMT tubes may not be required. An ordinary detector cable can be used and the counting system need not be light-tight (see Figure 3B). Scattered radiation will produce pulses or current in the detector and the signal is transmitted through the ordinary cable to the nuclear electronics, where it is measured, analyzed and evaluated.
Different Radioactive Sources It is possible to use more than one radioactive source, or to use a radioactive source that emits gamma rays of several different energies for better accuracy in the measurements.
Different Geometries If the pipe or tube is of the twisted type or if its cross-sectional area is not circular, an arrangement like the one shown in Figures 4A and 4B can be used. The inspection system can be made of small diameter and a spring 6 is applied to push the inspection system towards the wall of the pipe or tube so that the device can always be maintained close to the wall regardless of the cross-sectional area of the pipe or tube. As the system provides information on the wall thickness from the region closest to the device, the system can be put in rotational and translational movement in order to get information on other pipe wall regions. Alternatively, more than one inspection system can be used, as shown in Figures 5A and 5B.
An alternative arrangement can also be used in which the shield 3 is put on the surface of the gamma detector and the radioactive source 4 on top of it, as shown in Figures 6A and 6B. The emitted and back-scattered radiation is indicated by the arrows 7 and 8 in Figures 6Aand6B.
It is also possible to make the device without a shield between the source and the gamma detector, as shown in Figures 8A and 8B.
In this case direct as well as the scattered radiation will interact with the gamma detector and will be measured. A pulse type electronic counting system can be used where two sets of gamma rays of different energies that give two peaks will appear. Each peak count can be measured separately, as shown in Figure 10. It is only the counts under the scattered peak that are of interest, and they are proportional to the wall thickness. Sources of different shapes can be used at different spacings from the gamma detector.
Instead of having a source 4 that is physically separated from the scintillation material 2, it is possible to coat the gamma detector with radioactive material 4 as shown in Figures 9A and 9B. Again in this case the gamma detector will respond to both direct and scattered radiation and the spectrum will also be as shown in Figure 10. The emitted and back-scattered radiation is again indicated by the arrows 7 and 8 in Figure 10.

Claims (10)

  1. Claims:- 1. A method of inspecting the inside of a pipe or tube which includes introducing a source of gamma rays into the pipe or tube and providing a gamma detector for counting and analyzing the back-scattered gamma rays.
  2. 2. A method as claimed in Claim 1, in which a shield is disposed between the source of gamma rays and the gamma detector.
  3. 3. A method as claimed in Claim 1, in which spring means is provided for biasing the source of gamma rays and the gamma detector towards a wall of the pipe or tube.
  4. 4. A method as claimed in Claim 2, in which spring means is provided for biasing the source of gamma rays, the shield and the gamma detector towards a wall of the pipe or tube.
  5. 5. A method as claimed in Claim 1, which includes the use of more than one source of gamma rays and more than one gamma detector.
  6. 6. A method as claimed in Claim 1, which includes moving the source of gamma rays and/or the gamma detector rotationally and/or translation ally.
  7. 7. A method as claimed in Claim 1, in which the source of gamma rays comprises radioactive material with which the gamma detector is coated.
  8. 8. A method of inspecting the inside of a pipe or tube substantially as hereinbefore described.
  9. 9. Apparatus for use in the carrying out of the method claimed in any one of the preceding claims substantially as hereinbefore described with reference to the accompanying drawings.Amendments to the claims have been filed as follows I0 Claims:- 1. A method of inspecting a pipe for corrosion, erosion or deposits which Includes:-a) directing gamma rays onto the pipe, b) providing a scintillation detector for detecting back-scattered gamma radiation from the pipe, and c) transmitting a light signal from the scintillation detector to a photomulitplier.2. A method as claimed in Claim 1, in which a shield is disposed between the source of gamma rays and the scintillation detector.3. A method as claimed in Claim 1, in which spring means is provided for biasing the source of gamma rays and the scintillation *4S*s* * . detector towards a wall of the pipe. 4 *. ** S4. A method as claimed in Claim 2, in which spring means is provided for biasing the source of gamma rays, the shield and the scintillation detector towards a wail of the pipe.5. A method as claimed in Claim I, which includes the use of more than one source of gamma rays and more than one scintillation detector.6. A method as claimed in Claim 1, which includes moving the source of gamma rays and/or the scintillation detector rotationally andior translationaily.7. A method as claimed in Claim 1, in which the source of gamma rays comprises radioactive material with which the scintillation detector is coated.8. A method of inspecting a pipe substantiafly as herein before described.9. Apparatus for use in the carrying out of the method claimed in Claim 1, said apparatus comprisIng a source of gamma rays, a scintillation detector for detecting back-scattered gamma radiation from the pipe, a photomultlplier and a light pipe or a fiber optic cable interconnecting the scintillation detector and the photomultiplier.
  10. 10. Apparatus as claimed in Claim 9 arranged for operation substantially as hereinbefore described with reference to the accompanying drawings. S. . S 4.
GB1010030.3A 2010-06-16 2010-06-16 Inspecting tubes using gamma rays Withdrawn GB2489654A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1010030.3A GB2489654A (en) 2010-06-16 2010-06-16 Inspecting tubes using gamma rays

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Application Number Priority Date Filing Date Title
GB1010030.3A GB2489654A (en) 2010-06-16 2010-06-16 Inspecting tubes using gamma rays

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GB201010030D0 GB201010030D0 (en) 2010-07-21
GB2489654A true GB2489654A (en) 2012-10-10

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Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3060315A (en) * 1955-01-17 1962-10-23 Serge A Scherbatskoy Pipe-line exploration
GB1296320A (en) * 1970-04-17 1972-11-15
US3835324A (en) * 1972-10-04 1974-09-10 O Weigle Pipe weld inspection method and apparatus
US3958120A (en) * 1973-11-12 1976-05-18 Combustion Engineering, Inc. Radiographic inspection of steam generator tubes
EP0098954A1 (en) * 1982-07-12 1984-01-25 Combustion Engineering, Inc. Dual isotope method to radiograph structures in nuclear steam supply systems
GB2151019A (en) * 1983-11-30 1985-07-10 Atomic Energy Authority Uk The inspection of buried pipelines
JPS63175709A (en) * 1987-01-16 1988-07-20 Kubota Ltd Method for measuring tube thickness
FR2652650A1 (en) * 1989-10-04 1991-04-05 Electricite De France Method of gammagraphic inspection of the condition of the wall of the inlet bend of the primary hot water pipe for a pressurised water reactor steam generator
DE19610475C1 (en) * 1996-03-16 1997-06-05 Univ Karlsruhe Device for locating leaks in pipes and in pipe connections esp. sewage, drain and waste water pipes

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3060315A (en) * 1955-01-17 1962-10-23 Serge A Scherbatskoy Pipe-line exploration
GB1296320A (en) * 1970-04-17 1972-11-15
US3835324A (en) * 1972-10-04 1974-09-10 O Weigle Pipe weld inspection method and apparatus
US3958120A (en) * 1973-11-12 1976-05-18 Combustion Engineering, Inc. Radiographic inspection of steam generator tubes
EP0098954A1 (en) * 1982-07-12 1984-01-25 Combustion Engineering, Inc. Dual isotope method to radiograph structures in nuclear steam supply systems
GB2151019A (en) * 1983-11-30 1985-07-10 Atomic Energy Authority Uk The inspection of buried pipelines
JPS63175709A (en) * 1987-01-16 1988-07-20 Kubota Ltd Method for measuring tube thickness
FR2652650A1 (en) * 1989-10-04 1991-04-05 Electricite De France Method of gammagraphic inspection of the condition of the wall of the inlet bend of the primary hot water pipe for a pressurised water reactor steam generator
DE19610475C1 (en) * 1996-03-16 1997-06-05 Univ Karlsruhe Device for locating leaks in pipes and in pipe connections esp. sewage, drain and waste water pipes

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Publication number Publication date
GB201010030D0 (en) 2010-07-21

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