USACE / NAVFAC / AFCESA / NASA UFGS-05 05 23.13 10 (November 2008) ----------------------------------- Preparing Activity: USACE Superseding UFGS-05 05 23 13 10 (April 2006) UNIFIED FACILITIES GUIDE SPECIFICATIONS References are in agreement with UMRL dated January 2009 SECTION 05 05 23.13 10 ULTRASONIC INSPECTION OF WELDMENTS 11/08 NOTE: This guide specification covers the requirements for ultrasonic inspections of weldments; including qualifications and procedures. Edit this guide specification for project specific requirements by adding, deleting, or revising text. For bracketed items, choose applicable items(s) or insert appropriate information. Remove information and requirements not required in respective project, whether or not brackets are present. Comments and suggestions on this guide specification are welcome and should be directed to the technical proponent of the specification. A listing of technical proponents, including their organization designation and telephone number, is on the Internet. Recommended changes to a UFGS should be submitted as a Criteria Change Request (CCR). PART 1 GENERAL 1.1 REFERENCES NOTE: This paragraph is used to list the publications cited in the text of the guide specification. The publications are referred to in the text by basic designation only and listed in this paragraph by organization, designation, date, and title. Use the Reference Wizard's Check Reference feature when you add a RID outside of the Section's Reference Article to automatically place the reference in the Reference Article. Also use the Reference Wizard's Check Reference feature to update the issue dates. References not used in the text will automatically be deleted from this section of the project specification when you choose to reconcile references in the publish print process. The publications listed below form a part of this specification to the extent referenced. The publications are referred to within the text by the basic designation only. AMERICAN SOCIETY FOR NONDESTRUCTIVE TESTING (ASNT)ASNT Q&A Bk C(1994) Question and Answer Book C: Ultrasonic Testing Method; (Supplement to Recommended Practice SNT-TC-1A)ASNT RP SNT-TC-1A(2006) Recommended PracticeAMERICAN WELDING SOCIETY (AWS)AWS D1.1/D1.1M(2008) Structural Welding Code - SteelASTM INTERNATIONAL (ASTM)ASTM E 165(2002) Standard Test Method for Liquid Penetrant ExaminationASTM E 709(2008) Standard Guide for Magnetic Particle Examination1.2 DEFINITIONS 1.2.1 A Scan Method of data presentation on a cathode ray tube using rectangular coordinates in which a horizontal base line indicates elapsed time when reading from left to right. A vertical deflection in the base line indicates reflect signal amplitude. 1.2.2 Acoustically Similar Material Material the same as that to be inspected; or another material proven to have acoustical velocity within plus or minus 3 percent and an attenuation within plus or minus 0.009843 dB/mm 0.25 dB/inch of the inspected material for the inspection frequency and wave mode, using the same mode as that to be used for inspection. 1.2.3 Amplitude When referring to an indication in A scan presentation, amplitude is the vertical height of the indication measured from peak-to-peak for radio frequency indications and trace-to-peak for video indications. 1.2.4 Attenuation Dissipation or loss of energy as ultrasonic vibrations travel through the material. Attenuation is caused almost entirely by scattering of the ultrasonic vibrations generated by the search unit. 1.2.5 Attenuation-Correction Controls Circuitry to provide a continuous increase in amplification with respect to time. This circuitry compensates for the reduction in sensitivity with depth as a result of sound beam divergence and its attenuation in material. 1.2.6 Back Reflection or End Reflection Reflection from the opposite side, end, or boundary of the material into which the ultrasonic energy was introduced. 1.2.7 Calibrated Gain Control (Attenuator) Circuitry with which gain can be reduced finite amounts by switching electrical signal attenuation into the circuit. 1.2.8 Calibration Process of comparing an instrument or device with a standard to determine accuracy or produce a scale. 1.2.9 Cathode Ray Tube (CRT) An electron tube in which a controlled beam of electrons from the cathode is used to produce an image on a fluorescent screen at the end of the tube. 1.2.10 Couplant Any material, usually a liquid or semiliquid, used between the search unit and the inspection surface to exclude air and to convey the ultrasonic vibrations between the search unit and the material being inspected. 1.2.11 Damping Control Control that varies the duration of transducer ringing. 1.2.12 Decibel (dB) Units for the logarithmic expression of the ratio of power levels. Power levels can be functions of voltage, current, or impedance, for example. Decibel units having no values of their own are only significant when a reference is stated, as 10 dB above one reference level or 6 dB below another reference level. 1.2.13 Delay Control Means of delaying the pattern obtained on the CRT. 1.2.14 Discontinuity Anything within a material that will cause a detectable interruption in an ultrasonic beam. 1.2.15 Distance-Amplitude Correction Curve Curve showing the relationship between signal amplitude and equal-sized reflecting surfaces at various distances from the transducer. Reference standards are used to obtain such curves. 1.2.16 Dynamic Range Ratio of maximum to minimum size of reflective areas that can be adequately distinguished on the CRT at a constant gain setting. 1.2.17 Effective Depth of Penetration Maximum depth at which the sensitivity is satisfactory for the quality of test desired. 1.2.18 Examination Within the context of this specification, examination is equivalent to the word "inspection." 1.2.19 Gain Control Circuitry designed into the ultrasonic system to vary reflection amplitude. This control is usually calibrated in decibels. It is also called the sensitivity control. 1.2.20 Gross Background displacement of the trace on the CRT from the established baseline due to the gain setting, the characteristics of the test equipment, or the material under examination. 1.2.21 Hertz One complete set of recurrent values of a periodic quantity comprises a cycle. In other words, any one set of periodic variations starting at one condition and returning once to the same condition is a cycle. 1.2.22 Immersion Techniques Test methods in which the part to be tested and the search units are immersed in water or other suitable liquid couplant. A mechanical device is used to firmly hold and direct the wave angle of the search unit. The search unit does not contact the item being inspected. 1.2.23 Indication Visual presentation on the cathode ray screen resulting from a sound beam reflection from a boundary surface or discontinuity. 1.2.24 Initial Pulse Indication Usually called the "initial pulse". A signal on the CRT screen marking the instant at which a voltage impulse is applied to the transmitting crystal. Its rising edge is frequently invisible due to the time lag in the probe shoe and the consequent necessity to ensure coincidence between the time base zero and the instant at which the transmitter pulse actually enters the material under test. 1.2.25 Linearity Property of an instrument revealed by a linear change in reflected signal or displacement. The vertical linearity is determined by plotting the change in ratios of signal amplitude from two adjacent reflections from an area of known size. The horizontal linearity is determined by plotting the distance the signal is displaced along the sweep against the change in material thickness or by noting the spacing of multiple back reflections. 1.2.26 Longitudinal or Compressional Waves Simple compression-rare-fraction waves in which particle motion within a material is linear and in the direction of wave propagation. Also called straight beams, or compressional or normal waves. 1.2.27 Longitudinal Wave Inspection Ultrasonic technique, normally using straight beam methods, in which longitudinal waves are the dominant form. 1.2.28 Mid-Screen Reflection Reflection whose amplitude is equal to one-half the useable screen height on the CRT. 1.2.29 Megahertz (MHz) One million hertz per second frequency. 1.2.30 NDT Level I An NDT Level I individual should be qualified to properly perform specific calibrations, specific NDT, and specific evaluations for acceptance or rejection determinations according to written instructions, and to record results. 1.2.31 NDT Level II An NDT Level II individual should be qualified to set up and calibrate equipment and to interpret and evaluate results with respect to applicable codes, standards, and specifications. 1.2.32 NDT Level III An NDT Level III individual should be capable of establishing techniques and procedures; interpreting codes, standards, specifications, and procedures; and designating the particular NDT methods, techniques, and procedures to be used. 1.2.33 Node Distance a shear wave travels in a straight line from the inspection surface before being reflected by the opposite surface. 1.2.34 Pulse Repetition Rate Number of spaced pulses of sound per second sent into the material being inspected. 1.2.35 Range Control Means of expanding the pattern obtained on the CRT so that any portion of the total distance being tested can be presented. 1.2.36 Reference Reflector Standard reflector 1.52 mm 0.06 inch diameter reference hole in the IIW reference block. Other approved blocks may have a different diameter reflector. 1.2.37 Reflector Boundary, consisting of an opposite side, crack, or separation, or a distinct change in material such as slag or porosity that reflects the ultrasonic energy the same as a mirror reflects light. 1.2.38 Refracted Waves Waves that have undergone change of velocity and direction by passing from one material to another material with different acoustical properties. Refraction will occur wherever the angle of the incident wave to the interface is other than perpendicular. 1.2.39 Rejectable Discontinuity (Defect) Reflector large enough to produce a signal (decibel rating) that exceeds the reject/repair line. 1.2.40 Resolution Ability to clearly distinguish signals obtained from two reflective surfaces with a minimum separation distance. Near-surface resolution is the ability to clearly distinguish a signal from a reflector at a minimum distance under the contact or near surface without interference from the initial pulse signal. Far-surface resolution is the ability to clearly distinguish signals from reflectors displaced at minimum distances from the far or back surface when the sound beam is normal to that back surface. 1.2.41 Ringing Excitation in a transducer due to the application of a short pulse of high voltage. 1.2.42 Scanning Procedure of moving the search unit or units along a test surface to obtain complete inspection of the entire volume of a material being inspected. Preliminary scanning refers to a somewhat common practice of rapidly traversing a weld ultrasonically with a higher instrument gain or sensitivity level than will be used for the evaluation. It gives the operator an estimate of the welding quality and also makes all defects more prominent and less likely to be missed. 1.2.43 Search Unit Device containing a piezoelectric material used for introducing vibrations into a material to be inspected or for receiving the vibrations reflected from the material. The active element of the search unit is defined as the effective transmitting area. Search units are also called transducers or probes. They may be single or dual and contain one or two piezoelectric elements, respectively, for transmission and reception. The single search unit is sometimes enclosed in a transducer wheel or search unit wheel. The search unit may be manually handled and placed in direct contact with the material to be inspected or may be held in a fixture for immersion techniques. 1.2.44 Sensitivity Measure of the ultrasonic equipment's ability to detect discontinuities. Quantitatively, it is the level of amplification of the receiver circuit in the ultrasonic instrument necessary to produce the required indication on the scope from the reference hole in the reference block. Also see "Standard Reference Level." 1.2.45 Shear Waves Waves in which the particles within the material vibrate perpendicularly to the direction in which the wave travels or propagates. Also called transverse waves. 1.2.46 Shear Wave Inspection Inspection technique using shear waves in a material. The search unit is placed at an angle to the contact surface of the material so the resultant refracted sound is a shear wave at an angle to the normal. 1.2.47 Standard Reference Level Mid-screen height reflection when beaming at the 1.52 mm 0.06 inch hole in the primary reference block or the reference hole in the secondary standard. 1.2.48 Surface Waves Waves that propagate along the surface of the material and penetrate it to only about 1/2-wavelength. Also known as Rayleigh waves. 1.2.49 Test Frequency Operating frequency in hertz per second of the search unit during period of activation. Frequency is usually expressed in megacycles per second or megahertz. The latter term has been adopted for international use and is preferred. 1.2.50 Video Form Type of signal presentation on a CRT in which only the upper half of the signal appears. 1.3 SYSTEM DESCRIPTION NOTE: Welded joints to be inspected will be shown on the drawings, stated in other sections, or added to this paragraph. Because accessibility and geometry of the joint are factors in obtaining adequate ultrasonic penetration, the designer should consider these factors in the design of the joint. Drawings or listings in the specifications must clearly indicate which weld joints are to be inspected ultrasonically. Procedures and Methods. Use the pulse echo contact method with an A scan presentation for the ultrasonic inspection of welded joints, except that immersion techniques may be used for some applications when approved by the Contracting Officer. Use the procedures, methods, standards, and description of equipment specified herein for inspection of weldments. The procedure description shall include the following: a. Couplant. b. Search unit characteristics including angle, size, shape, nominal frequency, type designation. c. Method and type of wave. d. Equipment and accessories including manufacturer, model number, date of manufacture, last date of calibration, and the manufacturer's electrical, physical, and performance specifications. e. Decibel (dB) compensation system for distance-amplitude correction. Perform ultrasonic inspections to detect the following defects: a. Cracks or crack-like faults. b. Root defects, including lack of penetration and fusion. c. Lack of fusion between passes on the sidewall. d. Porosity or inclusions and excessive undercutting. 1.3.1 Wave Types The types of waves and the conditions under which they shall be used are specified below: a. Shear Waves. Unless conditions prohibit, use shear waves. A longitudinal wave procedure may be used instead, if approved by the Contracting Officer. Use refracted waves between 40 degrees and 70 degrees except where different angles are indicated in approved procedures, such as for materials less than 13 mm 1/2 inch thick, for materials with sound velocities greater than in steel, when the weldments are not readily accessible, or when existing backing rings or backing strips are not removed. For inspection of weldments containing backing rings or backing strips, adjust the instrument and select the refracted angles in a way to separate the weldment and the backing ring reflections. The search unit angle and the resulting shear wave angle in the material to be inspected shall be established for each application and this information included in the procedure submitted for approval. b. Longitudinal Waves. When conditions prohibit the use of shear waves, longitudinal waves may be used. The procedure shall be specially developed to suit the application and shall have the prior approval of the Contracting Officer. 1.3.2 Changes in Procedure Should application of an approved procedure not provide for good resolution or adequate ultrasonic penetration in the items to be inspected (see paragraph EQUIPMENT QUALIFICATIONS), make changes in procedure or equipment such as frequency, pulse repetition rate, angle of search unit, couplant, or oscilloscope. Adequacy of the new procedure shall be demonstrated to the Contracting Officer. The Government reserves the right to require a change in test equipment during these tests if any of the following test system characteristics fall below the levels listed in paragraph EQUIPMENT QUALIFICATIONS: sensitivity, amplitude and distance linearity, signal-to-noise ratio, entry and back surface resolution and penetration. 1.3.3 Ultrasonic Equipment The ultrasonic equipment shall conform to the requirements listed in AWS D1.1/D1.1M Section Inspection, subsection UT and Part F, with the following exceptions: a. The ultrasonic test instruments shall be able to generate, receive, and to present pulses in the frequency range from 1 to 10 megahertz (MHz). b. Measure the horizontal linearity of the ultrasonic instrument in accordance with paragraph EQUIPMENT QUALIFICATIONS. c. In addition to the resolution test specified in AWS D1.1/D1.1M, subsection Ultrasonic Equipment, both near- and far-surface resolution tests shall be conducted in accordance with the tests specified for these characteristics in the paragraph EQUIPMENT QUALIFICATIONS. 1.4 SUBMITTALS NOTE: Review submittal description (SD) definitions in Section 01 33 00 SUBMITTAL PROCEDURES and edit the following list to reflect only the submittals required for the project. Submittals should be kept to the minimum required for adequate quality control. A “G” following a submittal item indicates that the submittal requires Government approval. Some submittals are already marked with a “G”. Only delete an existing “G” if the submittal item is not complex and can be reviewed through the Contractor’s Quality Control system. Only add a “G” if the submittal is sufficiently important or complex in context of the project. For submittals requiring Government approval on Army projects, a code of up to three characters within the submittal tags may be used following the "G" designation to indicate the approving authority. Codes for Army projects using the Resident Management System (RMS) are: "AE" for Architect-Engineer; "DO" for District Office (Engineering Division or other organization in the District Office); "AO" for Area Office; "RO" for Resident Office; and "PO" for Project Office. Codes following the "G" typically are not used for Navy, Air Force, and NASA projects. Choose the first bracketed item for Navy, Air Force and NASA projects, or choose the second bracketed item for Army projects. Government approval is required for submittals with a "G" designation; submittals not having a "G" designation are for [Contractor Quality Control approval.][information only. When used, a designation following the "G" designation identifies the office that will review the submittal for the Government.] Submit the following in accordance with Section 01 33 00 SUBMITTAL PROCEDURES: _{SD-03 Product Data Ultrasonic Inspection} A standard reference block and working standards as described in paragraph REFERENCE STANDARDS. The procedures to be used for personnel and equipment qualification, equipment calibration, and inspection, at least 30 days prior to their intended use. Approval by the Government will in no way affect the obligation of the Contractor to employ qualified personnel, equipment, and procedures, and to perform the inspection as specified. _{SD-06 Test Reports} Reports containing the following information: a. Identification and Location of Inspected Item: Name and place of the inspected item, the person performing the inspection, and the date of inspection. b. Detail of Inspections: Details of methods, types of waves used, search units, frequencies, inspection equipment identification, and calibration data with enough information to permit duplication of the inspection at a later date. c. Response in Calibration: The response from the DSC or SC block used in calibration and for acceptance/rejection in terms of the response from the 1.524 mm 0.06 inch reference hole in the standard IIW block (primary standard). d. Identification of Unacceptable Areas: Locations, dimensions, types, and area of unacceptable defects and discontinuities giving reflections over 50 percent of the reject/repair line. These may be noted on a sketch or marked-up drawing. e. Record of Repair Areas: A record of repaired areas shall be furnished as well as test results for the repaired areas. 1.5 QUALITY ASSURANCE 1.5.1 Personnel Qualification The three levels of responsibility associated with _{ultrasonic inspection} are defined in ASNT RP SNT-TC-1A. For qualification to perform ultrasonic inspection, personnel shall be certified under ASNT RP SNT-TC-1A and ASNT Q&A Bk C within a period of 1 year before the date of contract. Other qualification or certification may be accepted at the Contracting Officer's discretion. Personnel with only an operator or inspector trainee certification will not be considered qualified to pass judgement on the acceptability of inspected items, but may work under the direct supervision of a qualified ultrasonic inspector. Qualified ultrasonic inspectors shall be able to judge the acceptability of the item in accordance with paragraph ACCEPTANCE/REJECTION LIMITS. 1.5.2 Examinations If the Contracting Officer doubts an individual's ability as an operator, inspector, or supervisor, recertify the individual in accordance with ASNT RP SNT-TC-1A. At the option of the Government, the Contracting Officer may participate in administering the examination and in evaluating the results. 1.5.3 Reference Standards Use reference standards to calibrate the inspection equipment, test its operating condition, and record the sensitivity or response of the equipment during the inspection in accordance with paragraph EQUIPMENT QUALIFICATION. The standards shall comprise a standard reference block and reference specimens as noted below. a. Provide the standard reference block or primary standard consisting of the IIW block in AWS D1.1/D1.1M , Section Inspection, subsection Reference Standards. Also use the standard reference block in any reinspection on the same basis as the original inspection, even though the reinspection is to be performed by other ultrasonic instruments and accessories. b. As an option, use other recognized working standards detailed with the IIW block in AWS D1.1/D1.1M such as the Sensitivity Calibration (SC) block. However, such blocks shall be referenced to the IIW block as noted in paragraph SENSITIVITY CALIBRATION. Include details of their use in the procedure description submitted to the Contracting Officer. These blocks are the secondary standards. They shall be of acoustically similar material to the welds to be inspected. The secondary standards shall be suited for the applicable tests specified in paragraph EQUIPMENT QUALIFICATIONS and shall be used as follows, except where the IIW block is specifically required: a. To assure adequate penetration of the base material. b. To provide a secondary field standard. c. To calibrate the equipment and establish the standard reference level. 1.5.4 Resolution Test Block NOTE: The test block referred to here is the Netherlands version of the International Institute of Welding type of reference block. Furnish a resolution test block in accordance with the details shown in AWS D1.1/D1.1M Section Inspection, subsection Ultrasonic Equipment. 1.5.5 Equipment Qualifications Evaluate the ultrasonic instrument and accessories on their arrival at the jobsite, immediately prior to the start of inspection. Evaluate them using the Contractor's furnished primary standard and they shall meet or exceed the requirements listed in paragraphs below. Equipment that does not meet these requirements shall not be used in the inspection. a. Requalifications. Requalify the equipment after normal use at intervals not to exceed 40 hours, except as noted, and immediately after maintenance or repair or when the Contracting Officer considers its operation questionable. b. Longitudinal Wave System: 1). Vertical Amplitude Linearity. Two adjacent reflections of different amplitudes obtained through the thickness of the primary or secondary standard shall vary in the same proportion as the amplitude of the first reflection is increased in discrete 2-dB increments between 20 percent and 80 percent to full screen height. For each gain setting, the amplitude of each reflection shall vary by the same factor, within plus or minus 5 percent. Requalification is required monthly or as otherwise stated. 2). Horizontal Linearity. The first three multiple reflections obtained through the thickness of the primary or secondary standard shall be equally spaced, within plus or minus 5 percent, when spread over 90 percent of the sweep length. Requalification is required monthly or as otherwise stated. 3). Near-Surface Resolution. Excessive ringing that appears on the CRT to the right of the sound entry point shall not exceed a 13 mm 1/2 inch equivalent distance in steel with the search unit placed on the 100 mm 4 inch edge of the IIW (primary) block and positioned for maximum amplitude reflection from the 1.524 mm 0.06 inch reference hole of the primary standard. The reference reflector shall be set to mid-screen and the gain shall be increased 20 dB. The reference hole located at least 13 mm 1/2 inch from one edge of the AW DSC or SC secondary standard shall be used similarly. Acceptability will be on the same basis as in the primary standard. 4). Far-Surface Resolution. Verify this property of the equipment by the method detailed in AWS D1.1/D1.1M, Section Inspection, subsection Calibration of the Ultrasonic Unit with the IIW or other Approved Calibration Blocks. In addition, the trailing edge of the third reflection shall return to the sweep line and be clearly discernible. c. Angle Wave System: 1). Vertical (Amplitude) Linearity. Two adjacent multiple reflections from the 1.524 mm 0.06 inch reference hole in the primary standard shall vary in the same proportion as the amplitude of the first reflection in discrete 2-dB increments between 20 percent and 80 percent of full screen height. For each gain setting, the amplitude of each adjacent reflection shall vary within plus or minus 5 percent. For testing with the AWS SC or AWS DSC secondary standard, the same criteria shall apply. For the SC block, place the transducer on the longitudinal surface contiguous with the sound entry point lines, whereas the 100 mm 4 inch longitudinal surface of the DSC block shall be used for the same purpose. Requalification is required monthly, or as otherwise stated. 2). Horizontal Linearity (Angle Wave}. The first three multiple echoes, obtained from the 1.524 mm 0.06 inch reference hole of the primary standard or from the reference hole in a secondary standard with the transducer positioned at a minimum of 25 mm 1 inch sound path distance, shall be equally spaced plus or minus 5 percent when spread over 90 percent of the sweep length. The gain shall be adjusted to give a mid-screen height first reflection. Requalification is required monthly or as otherwise stated. 3). Near-Surface Resolution (Angle Wave). Position he search unit for maximum amplitude using the primary or secondary standard as in the horizontal linearity test. The gain shall be adjusted to give a mid-screen height first reflection and then shall be increased 20 dB. Excessive ringing that appears on the CRT to the right of the sound entry point shall not exceed 13 mm 1/2 inch equivalent distance in steel. 4). Far-Surface Resolution (Angle Wave). The equipment shall delineate the three resolution holes in the resolution block appropriate for the angle of the transducer to be used in the inspection. 5). Signal-to-Noise Ratio. With the search unit located as in the horizontal linearity test, the gain shall be set to obtain an 80 percent full screen height first reflection. The reference reflection-to-noise-amplitude ratio shall not be less than 10 to 1. 6). Exit Point. Place the search unit on the graduated scale on the 300 mm 12 inch edge of the primary standard and beam the ultrasound toward the curved edge of the block. The gain shall be set for a mid-screen first reflection. The search unit shall be moved back and forth until the first reflection is maximized. The index line on the side of the search unit shall be within 1.6 mm 1/16 inch of the mid-point of the graduated scale in either direction. Requalification is required after 40 hours or as otherwise stated. 7). Transducer Angle. Set the established exit point of the probe over the applicable angle index line scribed on the 200 mm 8 inch or 300 mm 12 inch edge, as appropriate, of the primary standard. The gain shall be set to obtain a mid-screen first reflection from the 50 mm plexiglass-lined hole for search units up to 70 percent with the search unit placed on the 200 mm 8 inch edge. Test search units of large angles that have been approved specifically by the Contracting Officer from the 300 mm 12 inch edge using the 1.524 mm 0.06 inch reference hole. The search unit shall be moved back and forth to maximize the first reflection. When the material to be inspected is not acoustically similar to the primary standard, the inspection angle shall be within plus or minus 2 degrees of the angle specified in the approved procedure. Requalification is required after 40 hours or as otherwise stated. PART 2 PRODUCTS (Not Applicable) PART 3 EXECUTION 3.1 PREPARATION OF MATERIALS FOR INSPECTION Surfaces shall be free from the following: 3.1.1 Weld Spatter Spattering or any roughness that interferes with free movement of the search unit or impairs transmission of the ultrasonic vibrations. 3.1.2 Irregularities Those which could mask or be confused with defect indications. 3.1.3 Weld Backing Strips Remove strips that are not to remain in place and eliminate all sharp edges and valleys by grinding or other mechanical means. 3.1.4 Dirt Remove all loose scale, rust, paint, and dirt from the coupling surface. 3.2 SENSITIVITY CALIBRATION Perform sensitivity calibration immediately after a change of operators and at least every 30 minutes thereafter as testing proceeds. Recalibration will be required after any power interruption, including a change of source, when the equipment is suspected of being in error, or after relocation of the jobsite. The 30-minute and relocation calibrations may coincide. Allow the instrument to warm up before calibration is attempted. Adjust the instrument range and delay controls to display signals from the reference hole in the primary (IIW block) or secondary standard (DSC or SC block or both) on the viewing screen for the range of distances to be inspected. 3.2.1 Calibration Procedure Calibrate the test instrument as described below. 3.2.1.1 Longitudinal Wave In calibrating with the primary standard, position the transducer on the 100 mm 4 inch edge for maximum reflection from the 1.524 mm 0.06 inch reference hole. Adjust the gain so that the first reflection is at 50 percent full scale. The top of that indication shall be marked on the CRT with a wax pencil or by other means. This establishes the standard reference level. A point at 80 percent of the standard reference level shall be calculated and marked. This locates the reject/repair line. If a secondary standard is to be used in the inspection, the reject/repair line shall be established similarly. For the DSC block, the transducer shall be positioned on the 100 mm 4 inch long surface and with the SC degrees sound entry point lines. Adjustment for loss of signal due to distance shall be compensated for as noted above. 3.2.1.2 Angle Wave In calibrating with either the primary or secondary standard, position the transducer on the same surfaces as in the case of the longitudinal wave system but over the sound entry point lines appropriate for the angle of the transducer to be used in the inspection. Adjust the gain to give a first reflection that is 50 percent of full-scale response. The top of that indication shall be marked with a wax pencil or by other means. This establishes the standard reference level. A point at 80 percent of the standard reference level shall be calculated and marked. This locates the reject/repair line. Loss of signal shall be compensated as noted. 3.2.2 Calibration of the Secondary Standards After adjusting the first reflection from the reference hole in the secondary standard to 50 percent full-scale response for a sheer or longitudinal wave inspection, a maximized reflection from the 1.524 mm 0.06 inch reference hole in the primary standard shall be obtained without changing the gain setting. Readjust the gain setting to obtain a 50 percent full-scale reflection and the readjusted setting shall be recorded as required by paragraph SUBMITTALS, to provide a basis for recalibration when the secondary standard is unavailable. 3.2.3 Equipment With a Calibrated Gain Control (Attenuator) When a calibrated gain control attenuator is used, position the transducer for a maximum reflection from the reference hole in the secondary standard representing approximately 1/2 the longest inspection distance. This reflection shall be adjusted to mid-scale by varying the gain control accordingly. The difference in decibels between this amplitude and the signal obtained from the first, second, and longest distance reflection obtainable on the secondary standard shall be measured. The differences shall be recorded and plotted on a curve to determine the necessary correction to the amplitude at the various inspection distances. A level of 80 percent of the primary level obtained from the corrected signal heights, is equivalent to the reject/repair line. 3.2.4 Equipment With Electronic Distance Compensation Circuitry If the difference in amplitude between the first reflection and the reflection obtained from the maximum inspection distance is 1 dB or less, the instrument may be used as is. If not, the procedure used for equipment with a calibrated decibel control shall be used to determine the necessary correction to the reflections obtained at the various inspection distances. This characteristic of the equipment shall be re-examined on a monthly basis or as otherwise stated in paragraph EQUIPMENT QUALIFICATIONS, and correction factors shall be modified accordingly. 3.2.5 Longitudinal Wave Distance-Amplitude Correction Curve A distance-amplitude correction curve may be used instead of the calibrated gain control or the electronic circuitry for either the shear or longitudinal wave system as described below: a. A shear wave distance-amplitude correction curve shall be constructed and drawn on the face of the cathode ray tube (CRT) for inspection of weldments in excess of 38 mm 1-1/2 inch thick when the design of the test equipment permits. The reference hole in the secondary standard [SC] [or] [DSC] shall be used to construct the distance-amplitude correction curve for a minimum of three node points, 1, 2, and 3. The sensitivity of the instrument shall be adjusted to produce 50 percent full-scale response for the maximized primary reflection and the reject/repair line shall be constructed at 80 percent of the established distance-amplitude curve. b. A longitudinal wave distance-amplitude correction curve shall be constructed and drawn on the face of the CRT when longitudinal waves are to be used in the inspection for material thicknesses exceeding 25 mm 1 inch, if design of the test equipment permits. The reference hole in the secondary standard shall be used. Instrument sensitivity shall be adjusted to 50 percent full-scale of the maximized response from the reference hole at 1/2 maximum inspection distance. A reject/repair line shall be constructed at 80 percent of the established distance-amplitude curve. The reflection amplitudes to define this curve shall be taken from the faces of the secondary sensitivity standards which are 25 mm 1 inch, 50 mm 2 inch, and 1/2 maximum inspection distance, and the longest distance obtainable from the secondary standard, respectively, from the reference hole. When a correction curve cannot be drawn on the face of the CRT, one of the distance-amplitude correction methods noted above and submitted under the procedure description shall be applied. 3.2.6 Longitudinal Wave Inspections Using Immersion Technique Use the reference hole in a secondary standard for each different inspection distance. Repair/reject limits shall be established by immersing both the search unit and secondary standard in the liquid bath in which the inspection is to be conducted. Use the procedure noted below: a. Direct the longitudinal waves from the search unit toward the face of the secondary standard closest to the reference hole. b. Position the search unit for maximum response. The amplitude of reflection shall be adjusted to 50 percent full-scale. The top of that indication shall be marked on the CRT with a wax pencil or by other means. This establishes the standard reference level. A point at 80 percent of the standard reference level shall be calculated and marked. This locates the reject/repair point. The above shall be repeated for each different surface-to-hole distance to establish the reject/repair line. c. With the gain at the same setting and the primary standard and search unit in air, a maximized reflection shall be obtained from the 1.524 mm 0.06 inch reference hole in the primary standard (IIW). Then, this gain setting shall be readjusted to obtain a 50 percent full-scale reflection. The readjusted setting shall be recorded as required by paragraph SUBMITTALS to provide a basis for recalibration when the secondary standard is unavailable. 3.3 INSPECTION PROCEDURE NOTE: When necessary, the designer will indicate on the drawing the area to be examined, the contact surface, and if welds are to be inspected from one or both sides. When possible, examine all welds from both sides of the weld and from one surface. If complete inspection cannot be accomplished from one surface, inspection shall be made from another surface that is part of the same joint. Preliminary scanning techniques using an increased instrument gain shall be used to locate possible defects. When possible, gain shall be increased to a minimum of twice (6 dB) the reference level setting. Final acceptance or rejection shall be evaluated with the equipment properly calibrated and the gain control set at the reference level. Use the reject/repair line to evaluate quality of the weld. If a periodic calibration check shows that the equipment is not operating properly or that the system's sensitivity has decreased more than 20 percent (2 dB) from the established sensitivity level, all welds inspected since the prior calibration shall be reexamined. If penetration of the shear waves is questionable, the angle search unit shall be placed in position on one side of the weldment with the waves directed through the weldment. A disconnected angle search unit, plastic or metal wedge or disk, or any good reflector shall be placed in the wave path of the search unit on the far side of the weld to reflect the sound. When good reflections cannot be obtained by either shear or longitudinal waves, modify the procedures. 3.3.1 Test Frequency The test frequency for ferrous materials shall be as specified in AWS D1.1/D1.1M, Section Inspection, subsection Ultrasonic Equipment, except for thicknesses below 13 mm 1/2 inch, frequencies between 2.25 and 5 MHz may be used to obtain increased sensitivity. For materials that are difficult to penetrate, any frequency within the operating range of the equipment may be used. The effective depth of penetration and sound beam divergency shall be demonstrated to the Contracting Officer. 3.3.2 Couplants NOTE: The designer will prohibit the use of any couplant considered injurious to the item to be inspected. Edit the following paragraphs as applicable. The choice of couplant is optional with the Contractor, except as follows: a. The couplant shall be the same as that used for equipment qualification and calibration. b. Couplants that may corrode the reference standards and material being tested or leave objectionable residues shall not be used. c. Oils shall not be used in systems intended to handle liquid oxygen. d. Couplants shall be of the proper viscosity to give good coupling for the surface roughness. 3.3.3 Shear Wave Inspection Perform shear wave inspection as follows: Place the search unit on the contact surface at a distance from the weld equal to that used when calibrating the equipment. 3.3.4 Longitudinal Flaws To detect longitudinal flaws, the search unit shall be slowly moved toward and away from the weld far enough to cover its entire cross section, approximately 90 degrees to the weld centerline. The search unit shall be radially oscillated to the left and right, covering an angle of approximately 30 degrees. During the foregoing movement, the search unit shall be continually advanced parallel to the weld centerline. The rate of movement shall depend on the operator's ability to clearly see and identify all reflections. The amount of movement shall be calculated to ensure that the inspection distance will be great enough to traverse the weld. [For plate thicknesses 50 mm 2 inches and greater with an unmachined stainless steel overlay covering the welded joint, the inspection distance shall range from a minimum of one thickness (T) or the first node back from the near fusion line to a distance exceeding T plus 2/3, the maximum width of the weld deposit at the surface. Repeat the inspection from the other side of the weld on the same surface if accessible or if not, from another surface that is part of the same joint as indicated above. The surface of the weld metal in the joint shall be ground smooth and blended with the base metal.] 3.3.5 Transverse Flaws To detect transverse flaws when the welded surface is ground flush, the search unit shall be moved along the welded surface in each direction parallel to the centerline of the weld metal with the wave radiating parallel to the weld centerline. To detect transverse flaws when the welded surface is not ground flush, the search unit shall be moved parallel to the weld in each direction, on the adjacent base metal at the top of the weld, with the wave directed at an angle of 30 degrees to the weld centerline. 3.3.6 Longitudinal Wave Inspection This inspection shall be made as follows: a. The search unit shall be placed on the contact surface with the wave directed in a straight line through any intervening base metal and through the weldment. b. The search unit shall then be moved slowly in a direction parallel to the weld centerline and zigzagged across an area equivalent to the welded thickness to make sure that waves penetrate the entire welded cross section. c. The rate of movement shall be dependent on the operator's ability to clearly see and identify all reflections. 3.4 GENERAL ACCEPTANCE/REJECTION REQUIREMENTS NOTE: The designer will designate whether ultrasonic inspection will take precedence over radiography or will be used to supplement radiography when both methods of inspection are to be used. The designer will delete portions in brackets when they do not apply or remove brackets when they do. Evaluate discontinuities only when the ultrasonic equipment is calibrated properly. If discontinuities are detected, direct the sound beam to maximize the signal amplitude. To determine the length of a discontinuity, the search unit shall be moved parallel to the discontinuity axis in both directions from the position of maximum signal amplitude. One-half the amplitude or a 6-dB increase in sensitivity from a point at which the discontinuity signal drops rapidly to the baseline shall be defined as the extremity of the discontinuity. At this point, the scanning surface shall be marked at the position indicated by the center of the transducer. This shall be repeated to determine the other extremity. The length of the discontinuity shall be defined as the distance between these two marks. a. For discontinuities with signal amplitudes exceeding full screen height, 50 percent of full screen shall be considered half-peak amplitude. At this point, the scanning surface shall be marked at the position indicated by the center of the transducer. This shall be repeated to determine the other extremity. The length of the discontinuity shall be defined as the distance between these two marks. b. The maximum signal amplitude, length, depth, and position within the inspection zone shall be determined and reported for discontinuities yielding a signal amplitude equal to or exceeding the reject/repair line. The minimum recordable length of a discontinuity shall be 3 mm 1/8 inch. When evaluating welds joining two members with different thicknesses at the weld, the thickness T shall be the lesser of the two thicknesses. c. The criteria for acceptance or rejection based on ultrasonic inspection will supplement a visual inspection. The sizes and surface conditions of the welds shall conform to the requirements indicated on the applicable plans and drawings and other sections of the specification. When ultrasonic inspection is used along with radiography, the limits specified under paragraph REFERENCE STANDARDS shall [be the primary standard] [supplement the radiographic standards]. 3.4.1 Investigation of Questionable Indications NOTE: This paragraph will be deleted if Class I and Class II in paragraph ACCEPTANCE/REJECTION LIMITS are deleted. An indication considered doubtful shall be brought to the attention of the Contracting Officer and, at the Contractor's option, the weld shall be repaired or investigated further. Indications detected within 10 mm 3/8 inch of accessible surfaces shall be investigated further using liquid penetrant in accordance with ASTM E 165 or magnetic particle methods in accordance with ASTM E 709, as applicable, to determine if the surface is penetrated. Failure to locate the flaws by one of these methods shall necessitate further investigation by the other. For nonmagnetic materials, only dye penetrant inspection is required. Other questionable defects shall be further investigated using modifications of the inspection procedure. 3.4.2 Inspection of Repairs All repairs shall undergo the same inspection procedure that originally revealed the discontinuities. Before acceptance, the welds shall meet the standards required for the original weld. 3.5 ACCEPTANCE/REJECTION LIMITS NOTE: These limits cover different types of joint configurations and provide for differing levels of acceptance standards. The designer will delete those paragraphs that do not apply for a particular project. If more than one class of weld is required for a project, the contract drawings will be annotated or a table will be provided in this section to clearly indicate the acceptance standard that applies to each joint. Class I includes items such as vessels for cryogenic fluids and American Society of Mechanical Engineers (ASME), Boiler and Pressure Vessel Code, Section IV. Class II includes pressure vessels constructed to the requirements of the ASME Boiler and Pressure Vessel Code, Section III, Subsection NC and Section VIII, or dynamically loaded items such as bridges and turbine cases. Class III includes statically loaded structures such as buildings, storage tanks for petroleum, oil, and lubricants (POL), and water storage tanks. Accept or reject welds by ultrasonic indication in accordance with the following: 3.5.1 Full Penetration Butt Joints and Corner Joints 3.5.1.1 Class I Reject welds on the basis of the following: a. Any evidence of a crack, including any revealed by dye penetrant or magnetic particle in accordance with paragraph GENERAL ACCEPTANCE/ REJECTION REQUIREMENTS. b. Any indication of a discontinuity such as excessive undercutting, lack of fusion, incomplete penetration, inclusions, or porosity which individually or collectively produce reflections equal to or greater than the established reject/repair line. c. Any discontinuity with a reflection equal to or exceeding 25 percent of the reject/repair line, up to and including the reject/repair line, shall be rejected where the discontinuity length exceeds 1/2 T or 25 mm 1 inch. d. Adjacent discontinuities separated by sound metal with the dimension less than twice the length of the longest discontinuity shall be considered a single discontinuity. The maximum distance between the outer extremities of any two such discontinuities or the sum of their lengths, whichever is greater, shall not exceed the limits specified. e. If the total cumulative length of the discontinuities in any 300 mm 12 inches of weld length exceeds T, that weld length shall be rejected. 3.5.1.2 Class II Reject welds on the basis of the following: a. Any evidence of a crack, including those revealed by dye penetrant or magnetic particle inspection in accordance with paragraph GENERAL ACCEPTANCE/REJECTION REQUIREMENTS. b. Any discontinuity with a reflection exceeding the established reject/repair line and with a length exceeding 6 mm 1/4 inch. Adjacent discontinuities separated by sound metal with the dimension less than twice the length of the longest discontinuity shall be considered a single discontinuity. c. Any discontinuity with a reflection greater than or equal to or 50 percent of the reject/repair line, up to and including the reject/repair line, shall be rejected if the discontinuity length exceeds T. In no case shall any single discontinuity length exceed 38 mm 1-1/2 inches. d. Adjacent discontinuities separated by sound metal with the dimension less than twice the length of the longest discontinuity shall be considered a single discontinuity. The maximum distance between the outer extremities of any two adjacent discontinuities or the sum of their lengths, whichever is greater, shall not exceed the length as specified above. e. If the total cumulative length of discontinuities in any 300 mm 12 inches of weld length exceeds 2 T, that weld length shall be rejected. 3.5.1.3 Class III Reject welds on the basis of the following: a. Any discontinuity with a reflection exceeding the established reject/repair line and with a length exceeding 13 mm 1/2 inch. Adjacent discontinuities separated by sound metal with a dimension less than twice the length of the longest discontinuity shall be considered a single discontinuity. b. Any discontinuity with a reflection greater than or equal to 50 percent of the reject/repair line, or with the level 8 dB more than the reject/repair line, and with a length (L) exceeding 50 mm 2 inches or LT, whichever is greater. c. If the total cumulative length of discontinuities in any 300 mm 12 inches of weld length exceeds 75 mm 3 inches or 2 T, whichever is greater, that weld length shall be rejected. 3.5.2 Full Penetration Tee Joints Full Penetration Tee Joints (for Incomplete Root Penetration): Any discontinuity with the reflection exceeding the established reject/repair line of the applicable class shall be rejected. Any discontinuity with a reflection exceeding 25 percent of the established reject/repair line, up to and including the reject/repair line, shall be rejected if its length exceeds 1/2 T in a direction transverse to the axis of the weld or LT parallel to the axis for all classes. If the total cumulative length of discontinuities in any 300 mm 12 inches of weld length exceeds the limits of the applicable class, that weld length shall be rejected. 3.5.3 Partial and Full Penetration Tee Joints Partial and Full Penetration Tee Joint Boundaries: The depth of weld penetration and weld cross section width at the through member surface shall be as indicated by applicable plans or drawings. Limits of discontinuities shall be as specified in preceding paragraphs. 3.5.4 Tee Joint Discontinuities Tee joint discontinuities extending into the through member shall be rejected if [reflection exceeds the established reject/repair line.] [reflection amplitude is in the range of minus 6 dB of the reject/repair line and the discontinuity extends more than 1.6 mm 1/16 inch or more into the through plate.] [the total cumulative length of discontinuities in any 300 mm 12 inches of weld length exceeds 100 mm 4 inches].