Ultrasonic Thickness Procedure Pulse-Echo Thickness Gage TABLE OF CONTENTS. 1.0 Introduction Reference Documents Summary of Practice 2

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1 Page: 1 of 6 TABLE OF CONTENTS SECTION PAGE NO. 1.0 Introduction Reference Documents Summary of Practice Significance & Use Apparatus Calibration & Adjustment of Apparatus Precision & Accuracy Special Precautions Personnel Qualifications & Certification Reports & Documentation 6

2 Page: 2 of INTRODUCTION 1.1 This practice provides guidelines for measuring the thickness of materials using the contact pulseecho method. 1.2 This practice is applicable to any material which ultrasonic waves propagate at a constant velocity throughout the part, and from which back reflection can be obtained and resolved. 2.0 REFERENCE DOCUMENTS A copy of reference documents shall be maintained. In case of conflict between these documents and customer drawings, the requirements of the customer drawings shall have precedence. All documents shall be in accordance with the latest accepted codes and addenda. 2.1 Easton Engineering & Inspection PLLC EEI-QA-10 EEI-QC-10 Quality Assurance Manual Quality Control Manual 2.2 ASTM International Standards ASTM E 317 ASTM E Standard Practice for Evaluating Performance Characteristics of Ultrasonic Pulse-Echo Testing Instruments and Systems Without the Use of Electronic Measurement Instruments. Standard Practice for Measuring Thickness by Manual Ultrasonic Pulse- Echo Contact Method. 2.3 American Society of Nondestructive Testing (ASNT) SNT-TC-1A (2011) ASNT Qualification and Certification of Nondestructive Testing Personnel Nondestructive Testing Handbook 2.4 Panametrics Instruction Manuals; 26DL Plus / 36 DL Plus / 37 DL Plus 3.0 SUMMARY OF PRACTICE 3.1 Thickness (T) when measured by the pulse-echo ultrasonic method is a product of the velocity of sound in the material and one half the transit time(round trip) through the material. T = Vt 2 where: T = thickness V = velocity t = transit time 3.2 The pulse-echo ultrasonic instrument measures the transit time of the ultrasonic pulse through the part. 3.3 The velocity in the material under test is a function of the physical properties of the material. It is usually assumed to be a constant for a given class of materials. Its approximate value can be obtained from Table 1 in the Panametrics Instruction Manual, App. I or from the Handbook of Nondestructive Testing, or it can be determined empirically. 3.4 One or more reference blocks are required having known velocity, or of the same material to be tested, and having thicknesses accurately measured and in the range of thicknesses to be

3 Page: 3 of 6 measured. It is generally desirable that the thickness be round numbers rather than miscellaneous odd values. One block should have a thickness value near the maximum of the range of interest and another near the minimum thickness. 4.0 SIGNIFICANCE & USE 4.1 The techniques described provide indirect measurement of thickness of sections of material. Measurements are made from one side of the object, without requiring access to the rear surface. 4.2 Ultrasonic thickness measurements are used extensively on basic shapes and products of many materials, on precision machined parts, and to determine wall thinning in process equipment caused by corrosion and/or erosion. 5.0 APPARATUS 5.1 Instruments Ultrasonic Thickness Gages: Panametrics 26DL / 36DLP / 37DLP The Panametrics Model 26DL / 36DL / 37DL Plus Ultrasonic Thickness gage operates on the dual transducer pulse-echo principle, timing the reflection of high frequency sound waves from the far wall of the test piece. The gage uses a dual transducer with separate transmitting and receiving piezoelectric elements or a single transducer with one transmitting and receiving piezoelectric element. Calibration The accuracy of measurements are only as good as the accuracy and care with which the gage has been calibrated. There are no internal calibration adjustments in the 26DL / 36DL / 37DL Plus. However, it is essential that the velocity and zero calibrations described in Section 6 be performed whenever the test material or transducer is changed. Periodic checks with samples of known thicknesses are recommended to verify that the gage is operating properly. Calibration must be performed prior to, at least once during, and immediately after the completion of an examination. 6.0 CALIBRATION & ADJUSTMENT OF APPARATUS Sound velocity in all materials changes with temperature. For maximum accuracy the calibration block should be at approximately the same temperature as the samples to be measured. 6.1 Velocity and Zero Calibration The material Velocity and Zero Calibration procedures may be combined using a thick and a thin calibration block of the same material. Step 1: Update the transducer Zero Compensation by wiping the transducer face and pressing the [ZERO] key. Step 2: Couple the transducer to the thick calibration block. Step 3: Press the [CAL] key. Step 4: When the thickness reading is stable, press the [VEL] key. Step 5: Remove the transducer and enter the thickness of the thick block using the numeric keypad. Step 6: Couple the transducer to the thin block and press the [CAL] key. Step 7: When the reading is stable, press the [ZERO] key.

4 Page: 4 of 6 Step 8: Remove the transducer and enter the thickness of the thin block using the numeric keypad. Step 9: Press the [MEAS] key to complete the calibration and go to the Measure mode. NOTE: The above Velocity and Zero Calibration may be achieved by performing the operation in reverse, i.e. CAL ZERO first, followed by CAL VEL. ERROR NOTE: If the gage long-beeps and displays Calibration Error Message before returning to the Measure mode, then an error has been made in the calibration procedure and the velocity will not be changed. The most likely problem is that the thickness value entered was too large. Pressing [2 nd F], [6] (STATUS) will give additional information about the error condition. 6.2 Material Velocity Calibration when Material Sound Velocity is known When preparing to measure a different material, of known sound velocity, the velocity may be entered directly without doing the CAL VEL procedures discussed above. Step 1: From the Measure mode press the [VEL] key. The current velocity will be displayed. Step 2: The new velocity may be entered using the numeric keys. An entry error may be corrected by pressing numeral [0] three times, then entering the correct value. Step 3: Press the [MEAS] key to complete the entry and return to the Measure mode. NOTE: If the gage is turned off before the [MEAS] key is pressed, the velocity will not be updated to the new value but instead will retain the current value. 6.3 Material Velocity Calibration when Material Sound Velocity is unknown To do the Material Velocity Calibration, a calibration block made from the material to be measured must be used. The block should be as thick as the thickest section to be measured and have smooth front and back surfaces that are parallel to each other. The thickness of the block must be known exactly. Step 1: Update the Transducer Zero Compensation by wiping the transducer face and pressing the [ZERO] key. Step 2: Couple the transducer to the block. Press the [CAL] key. Step 3: When the thickness reading is stable, press the [VEL] key. Step 4: Remove the transducer and enter the thickness of the standard using the numeric keys. NOTE: An entry error may be corrected by pressing the numeral [0] key three times, then entering the correct value. Step 5: Press the [MEAS] key to complete the calibration and return to the Measure mode. NOTE: If the gage is turned off before pressing the [MEAS] key, the velocity will not be updated to the new value but instead will retain its previous current value. ERROR NOTE: If the gage long-beeps and displays Calibration Error Message before returning to the Measure mode, then an error has been made in the calibration procedure and the velocity will not be changed. The most likely problem is that the thickness value entered was too large. Pressing [2 nd F], [6] (STATUS) will give additional information about the error condition.

5 Page: 5 of 6 The [VEL] key may be pressed following Velocity Calibration (or at any time from the measure mode) in order to read and record the material velocity for this particular material. This velocity may be entered directly from the keyboard in the future when measuring to this material, without using the test block. 7.0 PRECISION & ACCURACY SPECIAL PRECAUTIONS 7.1 Ultrasonic thickness gages may also be used effectively with rough surface conditions. In this case, only the first returned echo, such as from the bottom of a pit, is used in the measurement. Generally a localized scanning search is made to detect the minimum remaining wall. 7.2 Material Properties The instrument should be calibrated on a material having the same acoustic velocity and attenuation as the material to be measured. Where possible, calibration should be confirmed by direct dimensional measurement of the material to be examined. 7.3 Scanning The maximum speed of scanning should depend on material conditions, type of equipment, and operator capabilities. 7.4 Geometry: Highest accuracy can be obtained from materials with parallel or concentric surfaces. In many cases, it is possible to obtain measurements from materials with nonparallel surfaces. However, the accuracy of the reading may be limited and the reading obtained is generally that of the thinnest portion of the section being interrogated by the sound beam at a given instant Relatively small diameter curves often require special techniques and equipment. When small diameters are to be measured, special procedures including additional specimens may be required to ensure accuracy of setup and readout. 7.5 High-temperature materials, up to about 540 C (1000 F), can be measured with specially designed instruments with high temperature compensation, search unit assemblies, and couplants. Normalization of apparent thickness reading for elevated temperatures is required. A rule of thumb often used is as follows: The apparent thickness reading obtained from steel walls having elevated temperatures is high (too thick) by a factor of about 1% per 55 C (100 F). Thus, if the instrument was calibrated on a piece of similar material at 20 C (68 F), and if the reading was obtained with a surface temperature of 460 C (860 F), the apparent reading should be reduced by 8%. This correction is an average one for many types of steel. Other corrections would have to be determined empirically for other materials. 7.6 Echo-to-Echo measurement is a feature which allows the 36 and 37DL Plus gage to measure the remaining wall thickness of painted metal while ignoring the coating thickness. The mode of measurement may be easily changed between the normal total wall thickness mode and the Echoto-Echo mode by pressing [2nd F] [ZOOM]. Echo-to-Echo measurements utilize either the same dual transducers that are used for normal measurements or a single element delay line transducer. The name of this measurement mode refers to the fact that when in the Echo-to-Echo mode, the 36 and 37DL Plus measures from one back wall echo to the next back wall echo. The time interval between these echoes does not include the time through any paint, resin, or organic coating which may be present. The waveform display indicates the exact pair of echoes which are used to determine the thickness. All measurement, display, and data logger functions can be used with the Echo-to-Echo mode. Note that uncoated wall thickness measurements can also be made in the Echo-to-Echo mode, so 1t is not necessary to switch between modes when both coated and uncoated areas must be measured. When dual transducers are used in the Echo-to-Echo mode, it is generally not

6 Page: 6 of 6 necessary to set any gates or thresholds, however special blanking gates can be set if the application requires it. Additionally, when the single element transducer is used, the Extended Blank may be set to skip the paint/metal interface echo. 8.0 PERSONNEL QUALIFICATIONS & CERTIFICATION 8.1 Personnel performing inspection with the Method shall be qualified and certified in accordance with SNT-TC-1A (2011) as specified by EEI-QC Records of personnel certifications shall be maintained on file by Easton Engineering & Inspection and are available upon request. 9.0 REPORTS & DOCUMENTATION 7.5 Inspection procedure Type of instrument Calibration blocks, size, and material Size, frequency, and type of search unit Scanning method. 7.6 Results Maximum and minimum thickness measurements Location of measurements. 7.7 Personnel data, certification level. 7.8 Records shall be retained for a minimum of three years.