PAGE 2 OF 15 1.0 PURPOSE This Inspection Method describes the methodology for Ultrasonic Examination using manual and semi-automatic techniques by the contact and immersion longitudinal wave method and angle beam methods on wrought materials. This Inspection Method meets the requirements of ASTM A 388, ASME Section V, Article 5 and ASTM E1001using referenced calibration reflectors and an A-scan presentation as a minimum. 2.0 REFERENCES The latest edition of the Standards and References cited were utilized in the current release of this inspection method. Changes to a standard or reference that are determined to affect product quality or services shall be cause for revision of this document. 2.1 ASTM A 388 Standard Practice for Ultrasonic Examination of Steel Forgings 2.2 ASTM E 317 Standard Practice for Evaluating Performance Characteristics of Ultrasonic Pulse- Echo Testing Instruments and Systems without the Use of Electronic Measurement Instruments 2.3 ASTM E 428 Standard Practice for Fabrication and Control of Metal, Other than Aluminum, Reference Blocks Used in Ultrasonic Testing 2.4 ASME Section V, Article 5 Ultrasonic Examination Method for Materials 2.5 ASNT Recommended Practice No. SNT-TC-1A Personnel Qualification and Certification in Nondestructive Testing 2.6 ISO 9712 Non-destructive Testing, Qualification and Certification of NDT Personnel General Principals 2.7 ASTM E 1001 Standard Practice for Detection and Evaluation of Discontinuities by the Immersed Pulse-Echo Ultrasonic Method Using Longitudinal Waves 3.0 PERSONNEL 3.1 All personnel performing examinations in accordance with this specification shall be qualified and certified in accordance with a written practice that complies with ASNT SNT-TC-1 A, or ISO 9712, or equivalent. 3.2 Level I personnel shall be qualified to properly perform specific calibrations, specific nondestructive testing, and specific evaluations for acceptance or rejection determinations under direct supervision from a certified Level II or III and to record the results. Selection of test method or technique and interpretation and evaluation of test results to codes and/or standards shall be performed by Level II or III personnel. 3.3 Level II personnel shall be qualified to set-up and calibrate equipment and to interpret and evaluate results with respect to codes, standards and specifications. Level II personnel shall be able to organize and report results of non-destructive tests and to provide training and guidance to Trainees and Level I personnel. 3.4 Records of certified personnel shall be maintained.
PAGE 3 OF 15 4.0 DEFINITIONS 4.1 Indication Levels (clusters): Five or more indications in a volume representing a 2 inch (50mm) or smaller cube in the forging. 4.2 Individual Indications: Single indications showing a decrease in amplitude as the search unit is moved in any direction from the position of maximum amplitude and which are too small to be considered traveling or planar. 4.3 Planar Indications: Indications shall be considered continuous over a plane if they have a major axis greater than 1 inch (25mm) or twice the major dimension of the transducer, whichever is greater, and do not travel. 4.4 Traveling Indications: Indications whose leading edge moves a distance equivalent to 1 inch (25mm) or more of metal. 4.5 Effective Beam Diameter: That distance through which a search unit can be traversed across a calibration reflector so that the corresponding echo amplitude is at least one half (-6 db) of the maximum amplitude. The effective beam diameter is not a characteristic of the search unit alone, but is dependent on the propagating medium, distance to the discontinuity, reflector geometry, etc. 4.6 Scan Index: The length of the step created by indexing the scan of the search unit over the part, which is continuously scanning in one direction, then stepping in the direction perpendicular to the scan or making a linear advance per rotation (pitch) for rotary scan of cylindrical parts. The allowable scan index should be correlated with the search unit effective beam diameter to ensure full coverage of the part. 4.7 Transfer: A change in scanning gain to compensate for differences in attenuation of the reference standard and the component of material being inspected. 5.0 EQUIPMENT 5.1 General 5.1.1 An ultrasonic pulsed reflection type instrument shall be used for these inspections. The system shall have a minimum capability for examining at frequencies from 1 to 5 MHz for the contact methods except as otherwise noted. Other frequencies may be used if equal or better sensitivity can be obtained. 5.1.2 The instrument shall have basic calibration performed at least every twelve months per ASTM E 317, or whenever maintenance is performed which affects the function of the instrument. 5.1.3 The instrument shall provide linear vertical presentation within +5% for a minimum of 75% of the screen height (sweep line to top of screen). The 5 % linearity referred to is descriptive of the screen presentation amplitude. 5.2 Immersion 5.2.1 The instrument shall have a pulser of sufficient voltage, repetition rate and wave shape to provide total volume coverage at the desired scanning speed as established using calibration reflectors. 5.2.2 For automated immersion examination of parts or material with regular shape and parallel surfaces, such as plate, machined bar stock, and forgings, an audible alarm or recording equipment should be used.
PAGE 4 OF 15 6.0 SEARCH UNITS A. The alarm or recording equipment should be adjustable to allow triggering at any commonly required level of indication amplitude and depth of material. B. To ensure that the alarm gate tracks the inspection area, the gate should lock on the first interface pulse from the test piece rather than on the initial pulse from the system. 5.2.3 Manipulating equipment should adequately support the search tube, containing the search unit, and allow angular adjustments in two mutually perpendicular, vertical planes. A manipulator may be attached between the search tube and search unit to provide the necessary angular adjustments. 5.2.4 Scanning and indexing apparatus should allow for accurate positioning of the search unit and control of the scan and index. Water-path distances should be continuously adjustable. 5.2.5 The container or tank should permit accurate positioning of the search unit, reference blocks, and part or material to be examined. (See Figure 2) 6.1 Contact Method 6.1.1 Search units, having a transducer with a maximum active area of one (1) square inch (650 mm 2 ) with 3/4" (20 mm) minimum to 1-1/8" (30 mm) maximum dimensions shall be used for straight-beam scanning, and search units equipped from 1/2 (13 mm) by 1 inch (25 mm) to 1 inch (25 mm) by 1 inch (25 mm) shall be used for angle-beam scanning. 6.1.2 Search units with other sizes and frequencies may be used for evaluating and locating indications and improving surface contact and noise levels. 6.1.3 For straight-beam examination of ferromagnetic materials, use a nominal 2 1 4- MHz search unit whenever practicable; however, 1 MHz, frequency may be used for coarse grained austenitic materials and long testing distances. In many instances, when examining coarse grained austenitic materials, it may be necessary to use a frequency as low as 0.4 MHz. Other frequencies may be used if desirable to improve resolution, penetrability, or ability to detect flaws. 6.1.4 Dual-element transducers shall be used to inspect those regions of a forging where the presence of a bore, taper, or other feature prevents scanning the near field region scanned using single element transducers from the opposite surface 6.1.5 Dual-element transducers shall be used to inspect areas near the back-wall of forgings where indications caused by noise exceed the reporting requirements of 10.9.1. 6.2 Immersion Method 6.2.1 The search units should be of the immersion type. 6.2.2 Only straight-beam (longitudinal) search units, with flat or focused acoustic lenses, should be used. Generally, round or rectangular search units are used for examination whereas round search units with symmetrical sound beam patterns are used for evaluation. 6.2.3 Nominal frequencies of 2.25 to 15.0 MHz may be used.
PAGE 5 OF 15 7.0 SURFACE PREPARATION 7.1 Surface finish for ultrasonic examination shall normally be 250 RMS or better. The finished surface shall be free of weld splatter, surface roughness or any foreign matter (e. g. oil, grease, dirt, etc) which might interfere with the examination. Where the condition of the surface interferes with the examination, the surface shall be prepared as necessary to permit examination. 7.2 Heavy steel forgings shall be prepared for examination by machining to provide cylindrical surfaces for radial examination in the case of round geometry and the ends shall be machined perpendicular to the axis of the forging for axial examination. Faces of disk and rectangular geometry shall be machined flat and parallel to one another. 8.0 COUPLANT In all cases the couplant used for calibration shall be the couplant used for material examination. 8.1 Contact Method 8.1.1 The couplant shall be non-injurious to the material being examined and shall have sufficient wetting characteristics to allow ultrasonic transmission into the material being examined. Couplants having good wetting characteristics include SAE 20W or 30W motor oil, glycerin, cellulose gel, grease, pine oil, or water. 8.1.2 Couplant used on nickel base alloys shall not contain more than 250 ppm of sulfur. 8.1.3 Couplants used on austenitic stainless steel, or titanium, shall not contain more than 250 ppm of halides (chlorides plus fluorides). 8.2 Immersion Method 9.0 CALIBRATION The water should be clean and de-aerated. Residual suspended particulate matter and air bubbles that collect on the search unit surface should be removed. 9.1 General 9.1.1 Instrument calibration shall be accomplished prior to inspection, utilizing reference standards. If quantitative information is to be obtained, vertical and horizontal linearity shall have been established and checked in accordance with ASTM E 317. 9.1.2 The same contact wedges to be used during the examination shall be used for calibration. 9.1.3 Any instrument control which affects the instrument linearity (e.g., filters, or clipping), shall be in the same position for calibration, calibration check, instrument linearity checks, and examination. For contact or immersion examination, the temperature differential between the calibration block(s) and the examination surface shall be within 25 0 F (14 0 C). Note: The reject control shall not be used.
PAGE 6 OF 15 9.2 Reference-Block Technique: Straight-Beam Adjust the instrument controls to obtain the required signal amplitude from the flatbottomed hole. A DAC (distance amplitude correction) shall be based on FBH (flat bottom hole) with the metal travel and hole sizes shown below unless otherwise specified. Longer metal travel distance reference blocks of at least 75% of the longest distance shall be utilized when examining thick sections. When the metal travel distance of the product exceeds the longest metal travel distance of the calibration standard, the DAC curve may be extended up to 25% of the distance of the longest calibration standard, so long as the extended portion of the DAC does not fall below 25% of full screen height (See Figure 1A). Instruments with capability of supporting computer program controlled recording of DACs may also be used where the DAC is automatically converted to a horizontal line (See Figure 1B). This is known as time corrected gain (TCG). 9.2.1 The following FBH standards shall be applicable unless otherwise specified by the Quality Plan (QP). Components Other Than Valve and Choke Stems Less than 1-1/2 inch (38.1mm) metal travel 1/16" (1.6 mm) Dia. FBH 1-1/2 (38.1mm) thru 6 inch (152.4mm) metal travel 1/8" (3.2 mm) Dia. FBH Over 6 inch (152.4mm) metal travel All sizes Valve and Choke Stems 1/4" (6.4 mm) Dia. FBH 1/8" (3.2 mm) Dia. FBH (see also Paragraph 9.4.2 for required angle beam technique) 9.2.2 The ultrasonic test instrument shall be adjusted so that the response from the reference hole(s) shall not be less than 25% of the screen height. 9.2.3 Reference blocks shall be manufactured and identified in accordance with the requirements of ASTM E 428. Material used for reference blocks shall be of similar acoustical attenuation as the material to be examined. Acoustical attenuation shall be within +/-25% as defined in ASTM E 428. The grain size, heat treat condition, physical, and chemical composition, surface finish, and manufacturing procedure (rolling, forging, and so forth) are variables to be considered in matching acoustic response. 9.2.4 Area-amplitude blocks, distance amplitude blocks, or a combination including both area and distance amplitude blocks in one set are acceptable. Distanceamplitude blocks are recommended. 9.2.5 The test surface roughness on the calibration standard shall be comparable to, but no better than, the item to be examined. 9.3 Angle Beam Shear Wave Technique for Rings and Hollow Cylindrical Forgings This angle beam technique can only be used to perform the examination from the circumference of rings and hollow cylindrical forgings when the OD to ID ratios is less than 2 and when the axial length is greater than 2 inches (50 mm).
PAGE 7 OF 15 9.3.1 It is preferable to have the calibration notches described for this method in excess material or test material when possible. Where a group of identical forgings is made, one of these forgings may be used as the separate calibration standard. When a separate calibration standard is used, it shall have the same nominal composition, heat treatment, size (O.D.), and thickness as the forging it represents. The test surface finish on the calibration standard shall be comparable but no better than the item to be examined. 9.3.2 A 2.25 MHz, 45 0 angle-beam search unit should be utilized, unless thickness, OD/ID ratio, or other geometric configurations results in failure to achieve calibration. Other frequencies may be used if desirable for better resolution, penetrability, or detectability of flaws. The transducer for the contact method shall be equipped with a wedge or shoe that will result in the beam mode and angle required by the size and shape of the cross section under examination. 9.3.3 Calibrate the instrument for the angle beam examination to obtain an indication amplitude of approximately 75% full screen height from a rectangular or 60 degree "V" notch on the inside diameter. The notch is to be in the axial direction and parallel to the axis of the forging. The ID notch shall be cut to a depth of 3% maximum of the thickness at the time of examination or 1/4 inch (6 mm), whichever is smaller, and its length approximately 1 inch (25 mm). The notch width shall have a maximum width of two times the depth. 9.3.4 At the same instrument setting obtain a reflection from a similar OD notch. Establish the amplitude reference line by drawing a line through the peaks of the first reflections obtained from the ID and OD notches. 9.3.5 When the OD notch cannot be detected when examining the OD surface, perform the examination from both the OD and ID surfaces when practicable (ID not too small). Utilize the ID notch when inspecting from the OD, and the OD notch when inspecting from the ID. For contact method, curve wedges or shoes may be used when necessary and practicable. 9.3.6 Forgings, which cannot be examined axially using a straight beam, in both axial directions, shall be examined with an angle-beam search unit. For axial scanning, use rectangular or 60 V-notches on the ID and OD for the calibration. These notches shall be perpendicular to the axis of the forging and the same dimensions as the axial notch. 9.4 Side Drilled Hole Technique 9.4.1 For materials which require an axial shear wave scan (e.g., PSL-3 and PSL-4 stems), a calibration block with a 1/16" (1.6 mm) side drilled hole, 1" (25 mm) deep shall be used. 9.4.2 Calibrate the instrument to obtain a reflection of approximately 75% of full screen height from the 1/16" (1.6 mm) hole at 1/4 V path. At the same instrument setting obtain a similar reflection from the 1/16" (1.6 mm) hole at 3/4 V path. Draw a line through the peaks of these reflections. This will constitute the shear wave reference line.
PAGE 8 OF 15 9.5 Transfer Correction 9.5.1 Contact Method: Transfer mechanisms may be used between a given calibration block and specific production material. This correction provides compensation for surface roughness of the test surface of the forgings as compared to the calibration standard to provide a realistic evaluation of discontinuities. A. Position the transducer on the calibration block whose overall length most closely matches the metal travel distance of the article to be tested and establish a reference 75% full screen height (FSH) signal from the back wall. (Note: The calibration block should have an equivalent or slightly less metal travel distance than the article to be inspected.) Record the gain setting in db B. Position the transducer on an indication-free surface of the article to be inspected and establish a back surface reflection. Increase or decrease the gain setting until the signal amplitude obtained from the back reflection of the test article is equivalent to the signal amplitude obtained from the calibration block reference level (75% FSH). Record the gain setting in db. C. The difference (db) in gain setting of step A from step B is the transfer correction factor. This factor is as added (if the reading in B is less than A from above), or subtracted (if the reading in B is greater than A from above) to the original gain setting and becomes the corrected reference sensitivity level or compensated DAC. D. When transfer correction exceeds+ 6dB, the reason shall be considered and additional surface preparation shall be carried out, if applicable. 9.5.2 Immersion Method: A. Centerline Method (See Figure 4) The reference block should be the one with a total length, to the back surface, approximately equal to the thickness of the part to be examined. Place the search unit over the reference block and manipulate for normal incidence, with the water path equal to that to be used in the examination. Position the search unit for maximum flat-bottom hole echo amplitude. Without moving the search unit, adjust the instrument gain so that the first back reflection amplitude is 80% of full screen height. Place the search unit over the material with the same water path and gain setting as above. Read this amplitude. The ratio of these amplitudes is a relative attenuation comparison expressed either in + % or + db. B. Off-Axis Method (See Figure 5) The reference block should be the one with a total length, to the back surface, approximately equal to the thickness of the part to be examined.
PAGE 9 OF 15 9.6 Recalibration The search unit should be placed over the reference block and manipulated for normal incidence, with the water path equal to that to be used in the examination. Position the search unit off axis approximately halfway between the flatbottom hole and the side wall. Without moving the search unit, adjust the instrument gain so that the first back reflection amplitude is 80% of full screen height. Place the search unit over the test piece with the same water path and gain setting as above. Read this amplitude. The ratio of these amplitudes is a relative attenuation comparison, expressed either in + % or + db. The following conditions will require re-calibration during the examination: 9.6.1 Significant changes in section thickness or diameter. 9.6.2 At least once per eight (8) hour shift. 9.6.3 Any change in the transducer, couplant, instrument settings, operator or scanning speed from that used for calibration. 9.6.4 When a loss of 15 % or greater in the gain level is indicated, reestablish the required calibration and reexamine all of the material examined in the preceding calibration period. 9.6.5 When an increase of 15% or greater in the gain level is indicated, reevaluate all recorded indications. 9.6.6 At the completion of the job. 9.6.7 At the discretion of the operator.
PAGE 10 OF 15 10.0 TESTING 10.1 As far as practical, the entire volume of each part shall be examined after heat treatment for mechanical properties, excluding any post weld heat treatment, but prior to drilling, cutting, tapering, or machining contours that limit effective interpretation of the examination results. Because of local configurations it may not be possible to examine some sections. 10.2 Materials shall be scanned from 2 perpendicular directions where possible. Scanning speed shall not exceed a rate of 6 inches (152 mm) per second for contact testing. For semi-automated scanning, adjust scanning speed or instrument repetition rate, or both, to permit detection of the smallest calibration reflector referenced in the specification and to allow visual detection or recording/alarming device to function. At no time shall the scanning speed or index rate exceed the speed or index at which an acceptable calibration was made. 10.3 For rings and hollow cylindrical forgings (see 9.3) scans shall be performed in both the circumferential and the longitudinal directions. The longitudinal scan shall be performed in both directions. For the circumferential scan direction, the scan shall be performed in both the clockwise and counter-clockwise direction. 10.4 To assure complete coverage of the forging volume, index the search unit with at least 15% overlap with each pass. 10.5 Scanning shall be performed at a gain setting at least two times (+6 db) the primary reference level. Background noise levels caused by material composition or processing greater than 50 % of the recordable level will be reported. 10.6 During examination the back reflection shall be monitored where possible for any significant reduction in amplitude. Reduction in back reflection may indicate not only the presence of a discontinuity, but also non-parallel front and back surfaces, or local variations of attenuation in the forging. In the case of an area showing 50% or more loss of back reflection where the back reflection can be monitored, further surface conditioning shall be accomplished to help determine whether the loss of back reflection is caused by surface conditioning or other factors. 10.7 For those areas of a particular part where it is not possible to conduct the ultrasonic straight beam examination from two perpendicular surfaces (excluding radius locations) an additional ultrasonic examination from other accessible surfaces will be required. The additional ultrasonic examination shall be a straight beam or an angle beam shear (transverse) wave technique. Note that the angle beam technique can only be used when the OD to ID ratio is less than 2, and when the axial length is greater than 2 inches (50 mm). NOTE: High sensitivity levels are not usually employed when inspecting austenitic steel forgings due to attendant high level of noise or hash caused by coarse grain structure. 10.8 Evaluation The operator shall investigate all indications above the visible noise level to determine cause. All indications shall be evaluated with the gain setting at the calibration reference level.
PAGE 11 OF 15 10.9 Recording Record all indications which do not meet the acceptance criteria required for the material. Additionally indications identified below shall be recorded. 10.9.1 Straight Beam Examination: A. Indications equal to or exceeding 100% of the reference amplitude. B. Length of indications which are planar, traveling, or clustered. Determine the location of the edges and the major and minor axes using the halfamplitude (6dB drop) technique. C. Variation in depth or planar area, or both, of traveling indications. D. Volume occupied by indication levels and the amplitude range. 10.9.2 Angle- Beam Examination: 11.0 DOCUMENTATION A. Indications equal to or exceeding 50% of the indication from the reference line. B. Indications where an amplitude reference line cannot be generated, record indications equal to or exceeding 50% of the reference notch. C. Length of indications which are linear, planar, traveling, or clustered. Determine the location of the edges and the major and minor axes using the half-amplitude (6dB drop) technique. 11.1 Following completion of examination, an Ultrasonic Examination Report shall be prepared to include the following information: 11.1.1 Identification of the items examined (Part Number, Revision level, Serial Number, Purchase Order, Sales Order, Production Order, Lot Number, and company, if other than Cameron, as applicable). 11.1.2 All recordable indications. 11.1.3 The location of recordable indications. A drawing shall be used showing the physical outline of the forging including dimensions of all areas, if any, not inspected due to geometric configuration, the item identification number and the axial, radial and circumferential distribution of recordable ultrasonic indications. 11.1.4 The specification or Inspection Method and revision to which the examination was performed as well as the acceptance criteria, method, couplant, transducer size, transducer type, transducer frequency, beam angle, mode of transmission, surface preparation, calibration block, instrument reference level gain etc. 11.1.5 The Ultrasonic Instrument (including serial number) 11.1.6 The inspector's signature and level of certification in accordance with requirements described in Section 3.0. 11.1.7 Date examination was performed. 11.1.8 The names and employers of any witnesses to the examination.
PAGE 12 OF 15 FIGURE 1 A FIGURE 1 B DAC vs. TCG SCREEN SHOT
PAGE 13 OF 15 FIGURE 2 Basic Immersion Setup FIGURE 3 Typical Distance-Amplitude Curve
PAGE 14 OF 15 FIGURE 4 FIGURE 5
PAGE 15 OF 15 TABLE 1 Distance Amplitude Reference Block-Metal Path Increments, in. (mm) TABLE 2 Reference Block-Metal path Selection in Near Field