Methods and devices for inspection of pipelines
Systems and methods for inspection of pipelines are disclosed herein. In one embodiment, an electromagnetic acoustic transducer (EMAT) transceiver (TRX) for inspecting a pipe includes a multichannel EMAT transmitter (TX) having multiple collocated transmitter coils. The EMAT TX can generate forward-propagating ultrasound waves and backward-propagating ultrasound waves. The forward-propagating ultrasound waves have higher amplitude than the backward-propagating ultrasound waves. The EMAT TRX also includes a multichannel EMAT receiver (RX) having multiple receiver coils that can receive the ultrasound waves transmitted by the EMAT TX through the pipe.
1. A method of detecting a flaw in a circumference of a pipe, the method comprising:
transmitting, by a multichannel EMAT transmitter (TX), unidirectional waves in the pipe; wherein transmitted ultrasound unidirectional waves comprise a forward-propagating component and a backward-propagating component, wherein the transmitted forward-propagating component is larger than the transmitted backward-propagating component;
receiving, by a multichannel EMAT receiver (RX), the unidirectional waves transmitted by the EMAT TX;
decomposing the unidirectional waves received by the EMAT RX into a forward-propagating component and a backward-propagating component; and
detecting the flaw in the circumference of the pipe based on decomposing the ultrasound waves received by the EMAT RX.
2. The method of claim 1 , further comprising determining a size of the flaw.
3. The method of claim 2 , wherein detecting the flaw in the circumference of the pipe comprises evaluating a ratio of strength of the forward-propagating component and strength of the backward-propagating component.
4. The method of claim 3 , wherein the detecting and sizing the flaw in the circumference of the pipe comprises simultaneously detecting and sizing the flaw in the circumference of the pipe based on the ratio of the strength of the forward-propagating component and the strength of the backward-propagating component.
5. The method of claim 1 , further comprising:
determining a time delay Δt between signals S 1 and S 2 received by individual coils of the EMAT RX by finding a value “a” that satisfies:
min
a
S
1
+
a
×
S
2
such that |a|≤1; and
determining the Δt as:
Δ
t
=
1
2
π
f
cos
-
1
a
where ƒ is a frequency of the unidirectional waves.
6. The method of claim 5 , further comprising using Fast Fourier Transform (FFT) to at least in part determine a time delayed signal S 2 .
7. The method of claim 5 , further comprising summing S 1 and S 2 to determine the forward-propagating component.
8. The method of claim 5 , further comprising subtracting S 2 from S 1 to determine the backward-propagating component.
9. The method of claim 1 , further comprising:
reducing a modal noise by delaying and then adding or subtracting signals received by the EMAT receiver to yield a pair of signals representing forward-propagating and backward-propagating waves, wherein the pair of signals have lower modal noise compared to the signals received by the plurality of multilayered coils of the EMAT receiver.
10. The method of claim 9 , further comprising:
determining a ratio of RMS-es of the forward-propagating waves and backward-propagating waves, the ratio of the RMS-es represents a measure of a side-band suppression.
11. The method of claim 10 , further comprising:
comparing the side-band suppression with pre-calibrated lookup table to obtain a size and a location of the flaw.
12. The method of claim 6 , wherein the EMAT RX and the EMAT TX each comprises at least two coils.
13. The method of claim 1 , wherein the transmitted forward-propagating component is at least four times larger than the transmitted backward-propagating component.