Transcript
OmniScan MX2 Training Program Introduction to Phased Array Using the OmniScan MX2
Part 3 Please send questions and comments to: PhasedArray PhasedArraySupport@olympu
[email protected] sndt.com
Introduction Introduction to to Phased Array Using Using the OmniScan OmniScan MX2 Part 3 - Overview Overview
Supporting documentation for the training program comes primarily from the MX2 software manuals and the Olympus reference manuals below. Modern phased array systems like the MX2 do not require an advanced knowledge of mathematics or acoustic theory and the training program focuses on practical explanations and real world application examples for the working inspector. Supporting theory, mathematical formulas, and more advanced PA concepts can be found in the books below available from the ONDT web site. These manuals can be downloaded at http://www.olympus-ims.com
Introduction Introduction to to Phased Array Using Using the OmniScan OmniScan MX2 Part 3 - Overview Overview
Supporting documentation for the training program comes primarily from the MX2 software manuals and the Olympus reference manuals below. Modern phased array systems like the MX2 do not require an advanced knowledge of mathematics or acoustic theory and the training program focuses on practical explanations and real world application examples for the working inspector. Supporting theory, mathematical formulas, and more advanced PA concepts can be found in the books below available from the ONDT web site. These manuals can be downloaded at http://www.olympus-ims.com
Introduction Introduction to to Phased Array Using Using the OmniScan OmniScan MX2 Part 3 - Review
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Introduction Introduction to to Phased Array Using Using the OmniScan OmniScan MX2 Part 3 - Velocity Velocity
The velocities of the wedge and component material are two of many parameters that must be be known to the the part and group group set up wizard wizard prior to the formation formation of the focal laws. No velocity correction can be made without recreating the focal laws. Like conventional UT, velocity is directly related to beam angle. (Snell’s law) When the velocity of the material or wedge is other than what was input into the group set up wizard the result is that the beam angle is not what it is supposed to be and cannot cannot be corrected. corrected. (The 70 degree beam beam is really really 68 degrees) degrees) A material velocity tolerance error of no more than 20m per second must be entered into the the calculator calculator to maintain a refracted steering steering angle within within +\- 1 degrees.
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Introduction Introduction to to Phased Array Using Using the OmniScan OmniScan MX2 Part 3 - Velocity Velocity
The velocity parameter can be set in the OmniScan MX2 software in 2 places: 1. The part\weld part\weld set up wizard by selecting material with with a fixed velocity from the database. (Probe\Part>Part>Material) (Probe\Part>Part>Material) 2. The UT>Genera UT>Generall sub menu menu by entering entering a custom custom velocit velocity y value. value.
Modifying the velocity will remove any calibration that has been completed in the wizards because the focal laws must be rebuilt. Using the velocity calibration wizard will also automatically populate the value.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity
The preferred method for obtaining the velocity in the group set up wizard is to select the material from a fixed database using a default value. When the material velocity is unknown, the MX2 has a velocity calibration wizard that measures the velocity of a component based on two fixed reflectors at known positions. (Side drilled hole, radius or back wall) Use of the velocity calibration wizard for shear wave inspection is only beneficial if a suitable calibration block made of the exact same material has been manufactured. This a common practice in pipeline jobs but rarely available for typical ASME, API, AWS, and similar inspections.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity
For one degree angle accuracy in carbon steel the velocity input to the group set up wizard (Calculator) must be within +\- 20 meters\second. If measuring velocity on a calibration block, 1 degree angle accuracy is only achieved when the sound path measurement is +\- .1mm of the actual value Only precision measurements to this tolerance made on a block of the exact same material will result in velocity accuracy better than a default value taken from the MX2 database.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity
The MX2 velocity calibration wizard has 3 options for measuring the velocity of a component that are compatible with both shear and longitudinal beams. 1. Radius. (Angle beam on sound path radius) 2. Depth (Angle beam on side drilled hole) 3. Thickness (0 degree on component back wall)
All three options require 2 reflectors at known positions. All three options will achieve best results when used with one A-scan or focal law. Angle beam is not recommended due to angle error. Prior to entering the velocity wizard, program at least one single focal law appropriate for the calibration type or install a conventional UT probe.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 – Gate Mode
Gate mode is set in the Gate\Alarms>Gate>Parameters>Mode sub menu and determines the point in the gate that is used for the readings and C-scan data. There are 3 measure options for position Cscan and thickness or time of flight related readings: – – –
There are 2 peak options for amplitude Cscan and related readings: – –
A. First crossing\edge. B. First Peak Position. C. Maximum Peak Position.
D. First Peak Amplitude. E. Maximum Peak Amplitude.
The relative peak and measure mode will be displayed in the reading box when applicable. �
Introduction to Phased Array Using the OmniScan MX2 Part 3 - Readings
The readings are relative to the selected A-scan in the group and based on the gate configuration for either peak or leading edge options. The volumetric readings are available for gate A and gate B. Gate A readings are boxed in red and gate B readings are boxed in green. The full list of available readings and definitions is found in the MX2 software users manual or online help index.
PA VIA
DA SA
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RA
Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity
Select Wizard>Calibration>Type Ultrasound> Mode Velocity>Start. Select Echo Type Thickness> and enter the values for thickness 1 and 2. Select Next.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity
If using a phased array probe, select the focal law used for the measurement. Adjust the gain for a signal and ensure that neither target 1 or 2 is saturated. Adjust the range over the targets. Excessive range will result in reduced accuracy due to UT axis resolution based on a fixed point quantity. (MX2 default is 320) Select Next.
1st backwall at 25mm
2nd backwall at 50mm
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity
Set the gate A start, width, and threshold over thickness 1. Select Get Position. The time of flight position of thickness 1 is recorded.
1st backwall at 25mm
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity
Set the gate A start, width, and threshold over thickness 2. Select Get Position. The time of flight position of thickness 2 is recorded and the MX2 will calculate the velocity.
2nd backwall at 50mm
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity
Observe the calculated velocity and ensure it is close to the expected value. Select Accept. The velocity is now set for the active group based on the wizard results.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity
The OmniScan MX2 user interface displays a status indicator for velocity.
A green V indicates that the current velocity in this group was the result of a measurement made through the velocity calibration wizard. A green V is not an indicator that the velocity is within tolerance and has no relevance to code or procedure compliance. When a velocity other than that in the MX2 database is required, it is normal practice to measure it one time with a conventional probe and enter it manually for future inspections. It is normal and acceptable for inspection .Ops files that have been calibrated for sensitivity and TCG to have a red V indicating no velocity wizard calibration was performed.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity Question: If the material velocity for the component is unknown and no calibration block of the exact same material exits, what is the benefit of performing the OmniScan MX2 velocity wizard calibration on an IIW block? Answer: There is no benefit. Measuring the velocity of the IIW block does nothing to improve the accuracy of the inspection because it is not made of the same material as the component. Without the calibration block on the left (Or similar design) made of the exact same material, the MX2 database is just as likely to be correct as a measurement made from a similar but different component like an IIW block. This function does not calibrate the instrument, it measures the component velocity. This is the same principle for conventional UT as well and not unique to phased array inspection.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Velocity Question: What is the affect on focal law creation using a wrong or inaccurate material velocity in the part and setup group wizards? Answer: The result is angle, focus, and wedge delay calculation error. Only wedge delay error can be fixed with the calibration process. Angle and focus error cannot. Slight angle error due to minor material velocity errors is normal and affects phased arrays similarly as a a single element probe. This is typical of conventional UT and can be measured using a standard IIW calibration block. IIW block angle verification is covered in detail in a later section.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Wedge Delay
After completion of the group set up wizard move the probe across the calibration block visualizing a side drilled hole at a known depth. (20mm below) If the hole indication is consistent and at the same depth for all focal laws the wedge delay is validated to the satisfaction of ASME, AWS, API and similar codes, a wedge delay wizard correction is not necessary, and ALL the below parameters will have been verified:
20mm SDH
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Wedge velocity. Wedge angle. Probe element height and position. Material velocity.
Introduction to Phased Array Using the OmniScan MX2 Part 3 - Wedge Delay
If the SDH depth changes across the focal laws, it is an indication that one or more of the parameters input into the group wizard were incorrect or out of tolerance resulting in refracted angle error. An incorrect or out of tolerance material velocity error is the most likely parameter to cause this. If the SDH is at a consistent depth that is a little short or long the wedge delay wizard can make the correction. The wedge delay calibration wizard will not correct angle error or velocity error.
Correct wedge delay
Angle or velocity error
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Introduction to Phased Array Using the OmniScan MX2 Part 3 – Wedge Delay
The wedge delay calibration wizard is designed to measure and offset the sound propagation between the probe and the exit point of the focal law in the wedge. (54.97usec below)
The function is exactly the same as conventional UT with the exception that all the variables are available to mathematically calculate it when exiting the setup group wizard and the function is performed on many A-scans or focal laws at the same time instead of just one.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Overview
When the wedge delay is set correctly, 0mm on the A-scan corresponds to the exit point of the wedge. The sound path propagation through the wedge is delayed out of the A-scan. Every focal law has a different wedge delay due to the different angles and exit point on the wedge. Inaccurate wizard input for wedge and probe parameters or failure to calibrate the wedge delay when needed results in inaccurate time of flight and depth readings. (SA and DA)
0mm
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Wedge Delay
Inputting the wedge, probe, and component parameters correctly into the group set up wizard is the most accurate means of arriving at the correct wedge delay. Use of the wedge delay wizard on a new or unworn wedge that was input correctly into the group set up wizard will not improve the reading accuracy and is a common source of problems and inaccurate inspection results. Mechanical handling errors and errors due to side drilled holes being measured at different angles often reduce the accuracy of wedge delay compared to the calculator results. The wedge delay wizard will not correct angle error or velocity error, only wedge height as pictured below.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Wedge Delay
The MX2 has wedge delay wizard options for both sound path radius and true depth side drilled hole (SDH) calibrations. The preferred and most accurate method is the sound path radius calibration because it is not dependent on angle trigonometry and can be performed over a longer sound path typical of the IIW block below. The true depth wedge delay calibration requires a trigonometry calculation that includes the angle. When the 70 degree is actually 69 it corrupts the wedge delay calculation when performed on SDHs in true depth mode. The calibration block must be of the same material (Same velocity) as the inspection.
True depth SDH
Sound path radius
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Wedge Delay
The wedge delay wizard will change the UT mode for the range and display based on the type of calibration reflector that is selected in the wizard. If using a standard IIW block, select the UT mode for either true depth or sound path and adjust the range as follows prior to entering the wizard:
True depth SDH
Sound path radius
50mm radius e l a c s h t a p d n u o S
e l a c s h t p e d e u r T
100mm radius
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15mm SDH
Introduction to Phased Array Using the OmniScan MX2 Part 3 - Wedge Delay
Be aware of the selected gate measurement mode. (Peaks or edges) Changing the gate measurement modes after calibration will affect the readings. The MX2 default is Peaks. Enter the wedge delay calibration wizard by selecting Wizard>Calibration>Type Ultrasound>Mode Wedge Delay>All Angles. Select start. Peak Mode
Edge Mode
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Wedge Delay
Select Echo Type>Radius. Enter the radius sound path distance. (50 or 100mm if using standard IIW) Select Next.
Radius reflector
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Wedge Delay
Set the position of gate A to cover the radius (Pictured below) or true depth calibration reflector. The vertical axis of the calibration window is represented by the gate start and width. Set the threshold of gate A to 10% amplitude. Select Next.
100mm radius
h t d i w e t a G
Focal laws and probe movement
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Wedge Delay
Select Clear Envelope and move the probe across the calibration block passing each focal law through the 100mm radius maximum amplitude position. The white envelope trace represents the position in mm for the maximum amplitude signal for each focal law. Prior to calibration the 57 degree focal law is reading 104mm in sound path. The calibration wizard will correct each focal law to 100mm sound path by modifying the the beam delay that was originally calculated by the group set up wizard. (UT Settings>Beam>Beam Delay) Select Calibrate.
57 degree focal law
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Wedge Delay
After selecting calibrate, move the probe over the block again passing each focal law through the 100mm radius maximum amplitude position to verify that the wedge delay was modified correctly. If the wedge delay calibration was successful the new white envelope trace will be contained within the tolerance window indicating all focal laws are detecting the 100mm radius +/- 1mm. Calibrate can be selected repeatedly improving the calibration until the white envelope trace is contained within the +/- 1mm tolerance. Select Accept and a green W is displayed in the MX2 indication area indicating that the wedge delay has been modified by the calibration wizard.
55 degree focal law
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Amplitude
The A-scan is the data view from which all other views are based. The B-scan S-scan, and C-scab convert amplitude to color coded pixels based on the 2D views. The C-scan can be configured for an amplitude or position 2D representation of the A-scan data. The ruler to the right displays the MX2 default amplitude color palette. 0 -100% amplitude vs. a scaled color palette typical of amplitude based acceptance criteria.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
The MX2 sensitivity calibration wizard is designed to equalize the amplitude of all A-scans or focal laws in the group on one calibration target. Typically an ID\OD notch or side drilled hole in a reference block. This function is also called ACG by the ASME codes. (Angle corrected gain) In conventional UT, sensitivity calibration is achieved by manually adjusting the gain until the reflected signal is at a predetermined amplitude, typically 80%. The function of the sensitivity wizard is to record the amplitude of every A-scan or focal law on the calibration target and automatically adjust the focal law gain offsets to the desired amplitude, typically 80%.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
Prior to sensitivity calibration lower angles will detect the target at a higher amplitude than the higher angles due to a longer sound path and more attenuation. Without sensitivity calibration defects can be missed and all focal laws cannot be used for code required amplitude based acceptance criteria such as ASME section V and similar.
�� 25.7 Total dB (No sensitivity calibration)
25.7 Total dB (No sensitivity calibration)
Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
In the examples below, the MX2 general gain of 24.1dB is applied to all focal laws in the group. After completion of the sensitivity calibration wizard each focal law applies a calibrated gain offset that is added to the general gain to achieve the required sensitivity, typically 80% amplitude.
24.1 dB + 1.6 dB = 25.7 Total dB
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24.1 dB + 9.2 dB = 33.3 Total dB
Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
The target used for sensitivity calibration should be in the general range of the area of interest for the inspection and specified in the work procedure. A general rule of thumb for weld inspection is to use the closest calibration target available that is at least 1.5 times the skip thickness in true depth. SDH selection for sensitivity calibration that is too shallow or too deep results in poor inspection results and may impede TCG construction.
m m 0 2
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
After completing the group setup wizard process, position the probe so that the calibration target can be seen in the S-scan. (15mm SDH from IIW as pictured below)
Ensure that the range is sufficient for the target on all focal laws. (45-70 degrees)
Enter the wizard to calibrate the S-scan for sensitivity (ACG) by selecting Wizard>Calibration>Type Ultrasound>Mode Sensitivity>All Angles. Select start.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
Enter the reference amplitude. (default 80%) All focal laws will be adjusted to this amplitude by addition of a focal law gain offset after sensitivity wizard completion. Enter tolerance. The tolerance is a visual indicator for amplitude verification after the sensitivity calibration correction. In the example below a tolerance of 5% on an 80% calibration would place the window from 77.5% to 82.5%.
Select Next.
5% tolerance window Amplitude envelope
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
Select the last focal law to be calibrated for sensitivity. When there are no obstructions from corners or adjacent calibration targets the entire sector scan can be calibrated at one time. Excluding a portion of the S-scan as pictured to the right will allow the calibration to be completed in sections where the gate can be repositioned to avoid interference from corners of the block or adjacent calibration targets if necessary. Select Next.
Focal law 45-70
Focal law 45-60
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Focal law 61-70
Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
Set the start and width of gate A to ensure that the calibration target can be detected by all focal laws in the S-scan. Set the gate A threshold as low as possible to ensure the last focal law can be detected. Gate thresholds below approximately 10% may have an amplitude error beyond the tolerance when the focal law gain offset is calculated to correct to 80%. Select Next.
Gate A A e t a G
Gate A
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
Gain compensation is a tool that is used to ease calibration. Use of gain compensation will allow a wider sector (50-65 degrees vs. 45-70 degrees) and will also allow calibration on a target with a longer sound path. When gain compensation is selected in the example below, a 2dB per usec correction is added to each focal law in addition to the 14dB of general gain. The longer the sound path to the calibration target, the more gain is added. (70 degrees receives more gain than 45 degrees) The MX2 default is 2dB\usec for sector scans and .2dB\usec for linear angle and can be manually adjusted. Select Apply and select Next.
2dB 2dB 2dB
2dB
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2dB
Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
Move the probe across the calibration block with consistent pressure and coupling. As the calibration target travels through the gate of each focal law the green envelope records the maximum amplitude detected. The MX2 will calculate the required gain offset in dB for each focal law to correct to 80%. Focal laws with amplitude over 80% but less than 100% will receive a negative gain offset. Do not select Calibrate yet. Continue to next slide.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
The green envelope should be smooth and consistent without any radical changes in amplitude between focal laws. No focal law can be higher than 100% amplitude and the lowest focal law must be higher than approximately 10% amplitude prior to selecting calibrate. This ratio equates to approximately 20dB. The highest and lowest focal laws must be within approx. 20dB of each other for the sensitivity wizard to function. If the amplitude envelope cannot be completed with a <100% and >10% ratio the angular range of the S-scan must be reduced. (Reduce S-scan from 30-75 degrees to 45-70 degrees) The longer the sound path and/or smaller the calibration target, the greater dB difference between the first and last focal laws of an S-scan calibration. If the green envelope was not created properly select clear envelope and repeat the probe movement. Select Calibrate. After sensitivity calibration a focal law offset is created in UT>Beam>GainOffset for every focal law.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
Successful sensitivity calibration of the S-scan is visualized by repeating the probe movement over the calibration block with all focal laws corrected to 80% amplitude within the tolerance. If any focal law is over 100% after calibration the complete process must be repeated by selecting Restart. Saturated focal laws cannot be corrected. Calibrate may be selected repeatedly until all laws are within tolerance. Select Accept when satisfactory and a green S will appear in the MX2 indication area indicating the sensitivity was completed.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
The MX2 sensitivity calibration wizard can be performed on all laws as in the previous section and can also interpolate the curve for the S-scan calibration based on 2 or 3 focal laws. When 2 or 3 focal laws are selected the wizard will record the amplitude value of only the selected focal laws to make a linear interpolation of the focal law gain offsets for the remaining laws. In other words, if the focal law gain offset of 2 or 3 focal laws is known based on real readings, the focal law gain offset of the remaining laws can be predicted with a linear interpolation. This feature is most accurate when the first and last focal laws of the Sscan are selected.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
Select either 2 or 3 for the quantity of focal laws to be used for the calibration. Enter the focal laws or angles that will be used. In this example we are using 3 focal laws representing the first, middle, and last focal laws of the S-scan. (45, 55, and 70 degrees in the example below)
Select Next.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - Sensitivity
Move the probe to peak the selected focal laws for maximum amplitude and verify that each of the three has been corrected within the tolerance. Select Accept. The software corrects all the focal law gain offsets for the S-scan to 80% amplitude with a linear interpolation based on the three readings at 45, 55, and 70 degrees. The MX2 indication area will display a green Si indicating the calibration was performed using an interpolation of 2 or 3 focal laws.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - TCG
What is the affect on a one line S-scan inspection without a TCG calibration? – –
It is impossible to set the inspection sensitivity where flaws are detected at a similar amplitude throughout the weld volume and flaws are missed or are detected over sensitive. The C-scan on the left was acquired with a TCG calibration and the C-scan on the right with only a sensitivity calibration. Both the color and amplitude for the TCG C-scan is consistent and flaws appearing at different positions in the weld will be detected similarly.
The ease at which flaws are detected, characterized, and sized in analysis is directly related to the quality of the sensitivity and TCG calibrations.
45-70 degree S-scan with TCG
45-70 degree S-scan without TCG
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - TCG
What is the difference between a TCG (Time corrected Gain) and DAC (Distance amplitude correction) with regard to the inspection results? – No difference. They are designed to arrive at the same defect rate and sizing. This is the same as conventional UT and a TCG is preferred over a DAC because it is compatible with an amplitude color palette for the full range. What is the difference between a TCG and DAC with regard to code compliance? – No difference. DAC and TCG are synonymous with respect to code compliance and where one is specified either may be used. The result of a DAC is the same but dependent on visualizing the A-scan, not the color palette.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - TCG
Set the start and width of gate A to ensure that the calibration target can be detected by all focal laws in the S-scan. Set the gate A threshold as low as possible to ensure the last focal law can be detected. Gate thresholds below approximately 10% may have an amplitude error beyond the tolerance when the focal law gain offset is calculated to correct to 80%. Select Next.
Gate A A e t a G
Gate A
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - TCG
Move the probe across the calibration block again with the same pressure and couplant to ensure that every focal law for this TCG point was corrected to 80%. Select next point and repeat the process for successive TCG points until complete. If after adding a point it is unable to be verified within the tolerance window select cancel point and repeat the process for that point. Upon completion of the last TCG point select accept TCG.
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - TCG
What is the total gain applied to the 60 degree focal law on the fourth TCG point at 25mm?
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Introduction to Phased Array Using the OmniScan MX2 Part 3 - TCG
What is the total gain applied to the 60 degree focal law on the fourth TCG point for 25mm side drilled hole? – Completion of the normal sensitivity and TCG wizard calibration process will result in the following: General gain (37.7dB) + focal law gain offset (0.1dB) + TCG point 4 (8.1dB) = 45.9dB UT>General>Gain
UT>General>Beam>Gain Offset
Sizing>Curve Setup>Current Law>Point 4> TCG Gain
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