X-ray or gamma ray systems or devices – Specific application – Absorption
Patent
1992-05-21
1993-12-07
Church, Craig E.
X-ray or gamma ray systems or devices
Specific application
Absorption
378 58, G01B 1506
Patent
active
052689522
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a measuring apparatus, and a corresponding procedure, for measuring faults in a pipeline and for observing foreign objects occurring in a pipeline.
Problems in maintenance are at present caused in various installations in processing industry, in power plants and equivalent by the job of monitoring the condition of pipelines. Damage to the pipelines is usually only observed after leakage has already occurred, when the losses thereby incurred may be appreciable indeed.
The object of the invention is to eliminate the drawbacks mentioned above. Specifically, the object of the invention is to create a measuring apparatus, and a corresponding measuring procedure, by the aid of which the condition of pipelines can be monitored whenever desired, without interfering with their use in various processes, and with the aid of which faults in the pipelines can be accurately located.
The measuring apparatus of the invention for measuring pipeline faults comprises on one side of the pipe a gamma radiation or x-ray source and on the other side, two detectors located at a distance of each other in the axial direction of the pipe and aligned with the radiation source, and an output device, the radiation source being disposed to direct measuring beams through the walls of the pipe that is being measured, at an angle relative to each other; the detectors being disposed to detect the beams that have traversed the pipe walls; and the output device being disposed to record a signal characterizing the pipe wall thickness.
In the procedure of the invention, there are directed through the pipe walls, two beams enclosing an angle with each other and traversing the pipe; the beams are moved, one trailing the other, relative to the pipe in the measuring direction; the intensities of the beams that have passed through the pipe walls are measured; and the locations of faults in the pipe are determined by comparing the spacing in the measuring direction of the signals obtained from the beams and the spacing of the beams at both traversing points.
The measuring apparatus and measuring procedure of the invention are based on the fact that two collineated radiations which are moved one after the other pass through the pipe wall with a given spacing when entering the pipe, and when they come out through the mantle on the other side of the pipe their spacing is different, preferably greater. Therefore comparison of the results of measurement obtained from different beams enables inferences to be drawn as to on which side of the pipe and at what location is the measured point of observation, such as e.g. a thinned-down area.
The measuring apparatus and the procedure are based on the fact that the radiation which is being used is absorbed by the pipe mantle in greater proportion, the greater the thickness at the traversing point. It is therefore also possible with the apparatus and procedure of the invention to measure obstructions in the pipe, in addition to various instances of corrosion damage and the like.
The pipes that are being measured may be made of reinforced plastic, steel, aluminium, copper, etc., and they may also be lagged with various lagging materials.
The radiation used in the invention is gamma or x-ray radiation. The wavelength of the radiation is on the order of 10.sup.-9 cm (gamma radiation) and 10.sup.-9 to 10.sup.-6 cm (x-rays). Cs 137 is a particularly well suited radiation source for the measurement.
The radiation that has passed through the pipe walls is detected with detectors on the opposite side of the pipe. For detectors one may use any kind of conventional radiation detectors which are fit for detecting the gamma or x-ray radiation in question. The signals from the detectors may be amplified, and the signals may be output by conventional methods known in the art, with a plotter, on film, on magnetic tape, etc.
Preferably, the radiation from the radiation source is accurately aligned with a collimator before and/or after the pipe that is being measured, so that sharp delimiting of the
REFERENCES:
patent: 3158744 (1964-11-01), Bernstein
patent: 4694479 (1987-09-01), Bacskai et al.
patent: 4695729 (1987-09-01), Monno et al.
Patent Abstracts of Japan, vol. 10, No. 169, p. 468, Abstract of JP 61-22239.
Church Craig E.
Valtion teknillinen tutkimuskeskus
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