Pulse FSM (field signature method) for measuring pipe defects

Abstract

The invention provides a method for measuring pipe defects. The method comprises the following steps: pulse excitation is applied to a to-be-measured pipe by current excitation electrodes at two endsof the pipe; measurement electrodes are arranged in the center area of the pipe; signals measured by the measurement electrodes are subjected to DFT (discrete Fourier transform) processing, discrete signals containing various-frequency information can be obtained by decomposition, and defect size can be solved quantitatively by analyzing the discrete signals. The method ensures insensitivity of measurement results to drift of an instrument system; besides, the absolute wall thickness loss can be measured, and measurement errors caused by the temperature difference between a reference plate anda pipe body can be avoided.

Description

technical field [0001] The invention relates to the technical field of on-line monitoring of pipeline defects, in particular to a method for measuring pipeline defects by a pulse field fingerprint method. Background technique [0002] Oil and gas pipelines have been facing the threat of corrosion and other defects for a long time. Using various detection methods to detect in-service pipelines is an important measure to ensure pipeline safety. Currently commonly used nondestructive testing techniques (Nondestructive testing, NTD) include: Ultrasonic thickness measurement (UT), eddy current testing (Eddy current, EC), radiation testing (Radiology), acoustic emission testing (Acoustic emission) , AE) etc. These non-destructive testing techniques have their own advantages, but at the same time there are some shortcomings that cannot be ignored. For example, the effective detection area of ​​ultrasonic thickness measurement technology is very small, and it is prone to missed de...

AI Technical Summary

Problems solved by technology

[0012] ⑴Measurement results are highly susceptible to drift signal interference

It can be seen from the formula (1) that during the service period of the FSM for more than 10 years, the voltage measured each time needs to be compared with the original voltage measured at the beginning of the system installation, and with the aging of components and the external environment Changes, etc., the FSM instrument system will inevitably undergo various drifts, which will eventually have a great adverse effect on the measurement results

figure 2 Shown is the wall thickness loss monitoring data of a certain FSM system in an oil and gas field in Southwest China. Reasonable phenomenon

[0013] ⑵ can only measure the relative wall thickness loss

It can be seen from formula (2) that FSM can only calculate the relative wall thickness loss according to the original wall thickness value, and the processing error of the pipeline or the calibration error of the original wall thickness will bring adverse effects to the calculation of the wall thickness loss.

According to the above, the pipeline part of the FSM has to be protected by a good rubber seal, and generally no failure will occur. However, the probability of damage to the circuit of the FSM instrument is relatively high. After replacing the new circuit, the wall thickness of the pipeline needs to be re-calibrated. And this work is very difficult for buried pipelines or submarine pipelines

[0014] (3) The temperature difference between the pipeline and the reference plate will greatly affect the stability of the monitoring data

Once the temperature sensor fails, the data of the entire FSM system will be destroyed, especially for buried pipelines or submarine pipelines. Due to constant maintenance, this failure is very fatal

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