Pipeline failure and maintenance-2
Release time:
2024-03-26
How to check and diagnose the pipeline?
(1) Inspection of inner surface of pipe
1) Leakage flux method: the N-pole and S-pole of the magnetic body are in contact with the surface of the pipe wall to be tested, and the pipe wall forms the magnetic circuit. The slider loaded with the flux density sensor slides along the inner surface of the tube. When the slider moves to the corrosion place, the change of the leakage flux density can be measured by the sensor. This method is commonly used in engineering, but the degree of contact between the sensor and the pipe wall directly affects the measurement accuracy, so it needs to be further improved.
2) Ultrasonic method: in the pipeline conveying liquid shown by the principle of ultrasonic detection of corrosion on the inner and outer surfaces of the pipe, the ultrasonic wave emitted by the ultrasonic transmitter at a fixed position returns to the receiver at the interface between the transmitter and liquid, the interface between the liquid and the pipe wall, and the interface between the pipe wall and air. The reflected wave T and s can be observed on the receiving screen respectively And B. In this way, the wall thickness, the corrosion position and depth of the outer pipe wall can be directly measured by the travel speed and travel time of the reflected wave. The distance between the ultrasonic transmitter and the inner surface can be measured by water, so that the size and position of the corrosion holes on the inner surface of the steel pipe can be measured.
Generally, the two methods are used together.
The above two methods mainly use the propagation of ultrasonic wave in water, oil and pipe wall to measure the location and size of corrosion holes. Because the attachment of pipe wall has a great attenuation effect on ultrasonic wave, it brings some errors to the measurement.
3) Eddy current method: a weak current is applied in a pair of primary coils, and eddy current is generated on the inner surface of the wall (tube wall) by electromagnetic induction. The secondary coils placed between primary coils are used to receive eddy current signals. When the eddy current signal passes through the pipeline, there is no waveform distortion in the normal part of the pipeline, but there is waveform distortion in the defect part. According to the current pulse, the defect position and corrosion condition can be determined. This measurement is not affected by wall attachment.
4) Camera method: This is a method to directly observe the inner surface of the tube. Place the camera on the slider, which is pushed by compressed air to slide in the tube. Flash photography can be carried out after each distance. In addition, the device is also provided with a ranging roller. In this way, the corrosion state of the pipe wall can be determined by the camera negative, and the defect position can be determined by the position sensor and the distance measuring roller.
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