Scanning method and apparatus

Patent metadata

Field	Value
Publication number	US-9897558-B2
Application number	US-201214355268-A
Country	US
Kind code	B2
Filing date	Nov 2, 2012
Priority date	Nov 2, 2011
Publication date	Feb 20, 2018
Grant date	Feb 20, 2018

Abstract

The invention discloses a scanning method and apparatus suitable for scanning a pipeline or process vessel in which a beam of gamma radiation from a source is emitted through the vessel to be detected by an array of detectors which are each collimated to detect radiation over a narrow angle relative to the width of the emitted radiation beam.

First claim

The invention claimed is:

1. A method of scanning a sub-sea pipeline to detect changes in density between different parts of the sub-sea pipeline, the method comprising:
providing at least one source of gamma radiation and a plurality of detector units configured to detect gamma radiation, each detector unit of the plurality of detector units comprising:
i. a radiation detector comprising a scintillator comprising a scintillating material and having a detecting surface defined by its thickness t and height h, wherein t≦h at the detecting surface and having a depth d perpendicular to the detecting surface at least 2t,
ii. a photodetector configured to detect light emitted by the scintillator in response to gamma radiation, and
iii. a collimator disposed between the scintillator and the at least one source of gamma radiation;

rotating the at least one source of gamma radiation and the plurality of detector units in a radius of rotation around an origin in the sub-sea pipeline;
providing a guiding system to guide said rotating in the radius of rotation around the origin in the sub-sea pipeline, the guiding system being indexed;
causing said at least one source of gamma radiation to emit gamma radiation along a plurality of predetermined radiation paths towards said plurality of detector units, the plurality of predetermined radiation paths passing through at least a portion of said sub-sea pipeline;
measuring a number of photons of gamma radiation detected by each one of said plurality of detector units; and
calculating a density value for each path from the number of photons of gamma radiation detected by each detector unit associated with the respective path.

2. The method according to claim 1 , wherein providing the at least one source of gamma radiation and the plurality of detector units comprises arranging the plurality of detector units in close proximity to each other in the form of an arc having a radius centered on the center of the sub-sea pipeline to be scanned.

3. The method according to claim 1 , wherein providing the at least one source of gamma radiation and the plurality of detector units comprises mounting the at least one source of gamma radiation and the plurality of detector units spaced apart on a support which provides a scanning device such that at least a portion of the sub-sea pipeline to be scanned is located between the at least one source of gamma radiation and the plurality of detector units.

4. The method according to claim 1 , wherein 1 mm≦t≦5 mm, 10 mm≦h≦50 mm, and 25 mm≦d≦75 mm.

5. The method according to claim 1 , wherein a depth of the collimator of each detector unit is in the range 50- 150 mm.

6. The method according to claim 1 , wherein an end of the collimator distal to the scintillator has an opening lying on the plane of a tangent to a circle having the at least one source of gamma radiation as its origin.

7. The method according to claim 1 , wherein the guiding system includes a motor and a mounting part on which the at least one source of gamma radiation and the plurality of detector units are mounted, the motor being configured to cause the at least one source of gamma radiation and the plurality of detector units to rotate.

8. A method of scanning a sub-sea pipeline to detect changes in density between different parts of the sub-sea pipeline, the method comprising:
providing at least one source of gamma radiation and a plurality of detector units configured to detect gamma radiation, each detector unit of the plurality of detector units comprising:
i. a radiation detector comprising a scintillator comprising a scintillating material and having a detecting surface defined by its thickness t and height h, wherein t≦h at the detecting surface and having a depth d perpendicular to the detecting surface at least 2t,
ii. a photodetector configured to detect light emitted by the scintillator in response to gamma radiation, and
iii. a collimator disposed between the scintillator and the at least one source of gamma radiation;

causing said at least one source of gamma radiation to emit gamma radiation along a plurality of predetermined radiation paths towards said plurality of detector units, the plurality of predetermined radiation paths passing through at least a portion of said sub-sea pipeline;
measuring a number of photons of gamma radiation detected by each one of said plurality of detector units; and
calculating a density value for each path from the number of photons of gamma radiation detected by each detector unit associated with the respective path,
wherein the collimator of at least one of the plurality of detector units has a plurality of walls defining a channel with an opening, each wall of the plurality of walls being aligned with a different radius of a circle having the at least one source of gamma radiation as its origin and the opening being aligned to face directly towards the at least one source of gamma radiation.

9. A method of scanning a sub-sea pipeline to detect changes in density between different parts of the sub-sea pipeline, the method comprising:
providing at least one source of gamma radiation and a plurality of detector units configured to detect gamma radiation, each detector unit of the plurality of detector units comprising:
i. a radiation detector comprising a scintillator comprising a scintillating material and having a detecting surface defined by its thickness t and height h, wherein t≦h at the detecting surface and having a depth d perpendicular to the detecting surface at least 2t,
ii. a photodetector configured to detect light emitted by the scintillator in response to gamma radiation, and
iii. a collimator disposed between the scintillator and the at least one source of gamma radiation;

causing said at least one source of gamma radiation to emit gamma radiation along a plurality of predetermined radiation paths towards said plurality of detector units, the plurality of predetermined radiation paths passing through at least a portion of said sub-sea pipeline;
measuring a number of photons of gamma radiation detected by each one of said plurality of detector units; and
calculating a density value for each path from the number of photons of gamma radiation detected by each detector unit associated with the respective path,
wherein providing the at least one source of gamma radiation and the plurality of detector units comprises mounting said photodetector at an angle to an axis of the collimator and the scintillator.

10. An apparatus for scanning a sub-sea pipeline to detect changes in density between different parts of the sub-sea pipeline, the apparatus comprising:
at least one source unit comprising a source of gamma radiation and shielding material configured to restrict an emission of gamma radiation from the at least one source unit;
a plurality of detector units configured to detect said gamma radiation, each said detector unit comprising:
i. a radiation detector comprising a scintillator comprising a scintillating material and having a detecting surface defined by its thickness t and height h, wherein t≦h at the detecting surface and having a depth d perpendicular to the detecting surface at least 2t,
ii. a photodetector configured to detect light emitted by the scintillator in response to gamma radiation, and
iii. a collimator placed between the scintillator and the at least one source unit;

a support, said at least one source unit and said plurality of detector units being mounted on the support in a fixed spaced apart relationship;
a scanning device configured to rotate the at least one source unit and the plurality of detector units around an arc having an origin located between the at least one s

Assignees

• Johnson Matthey Plc
• Pearson Kenneth

Inventors

• Bowdon Christopher
• Featonby Paul David
• Howstan James Stephen
• Jackson Peter
• James Kenneth
• Ronchi Emanuele

Classifications

• G21K1/02

  using diaphragms, collimators · CPC title

• G01T1/164

  Scintigraphy · CPC title

• G01N2223/419

  computed tomograph · CPC title

• G01N9/24 Primary

  by observing the transmission of wave or particle radiation through the material · CPC title

• G01T1/20

  with scintillation detectors · CPC title