标准海管UT工艺

ULTRASONIC TESTING PROCEDURE (PIPELINE)ULTRASONIC EQUIPMENTUltrasonic Test Instrumenta) The ultrasonic test instrument shall be the pulse-echo type suitable for use withtransducers oscillating at frequencies between 2 and 6 MHz.b) The instrument’s display shall be an “A” scan rectified video trace. The dynamic range ofthe display shall be such that a difference of 1dB of amplitude can be easily detected on the display.c) The horizontal linearity of the test instrument shall be qualified within 1% over the fullsound path distance to be used in testing.d) The instrument shall also provide a amplifier linearity within 5% of full screen height.e) The instrument shall have a calibrated gain (Attenuation) electrically accurate to withinplus or minus 2dB over a range of not less than 60 dB.f) Each instrument-transducer combination shall be capable of producing a minimum 3/4CRT vertical scale deflection from an echo received from the 4 in. radius curved surface of the IIW calibration block with a minimum of 40 dB amplification in reserve .ProbeProbes as a straight beam probes 0 degree and angle beam probes of 45, 60 and70 degree. The selection of probe shall be in accordance with client specificationand actual WPS ( thickness, welding bevel, etc.)straight beam probea) Straight beam probes shall be round in shape and shall have an active area of not lessthan 12.5 mm in diameter nor more than 25 mm in diameter maximum.b) The frequency shall be between 2 to 5 MHz.c) Probes of other sizes and frequencies may be used provided they are qualified asdescribed in API RP 2X code and approved by client.Angle beam probea) The oscillating element shall be approximately square / or round in shape withdimensions which result in an included beam angle of approximately 15 degrees at 6 dB less than the centerline maximum.b) A probe with a transducer element in size from 8 to 13 mm in width and 9 to 13 mm inheight operating at 2 to 5 MHz shall be mostly used in accordance with the code’s recommendations.c) The probe shall produce a sound beam in the material being tested within 2 degrees ofone of the following proper angles: 45, 60 and 70 degrees.The actual angle shall be checked or verified during calibration for testing and reported on the applicable test report.d) Each probe shall be clearly marked to indicate the frequency of the transducer, nominalangle of reflection and index point. Probes of other sizes and frequencies may be used provided they are qualified as described in API RP 2X and approved by client.e) The resolution of the angle probe shall be evaluated with the instrument controls set atnormal test settings and with indications from the holes brought to midscreen height.Resolution shall be sufficient to distinguish at least the peaks of indications from the three holes.Periodic CalibrationThe instrument shall be periodically checked in accordance with the “Calibration Procedure of Ultrasonic Flaw Detector”.All ultrasonic flaw detectors shall be calibrated by a recognized test authority. CALIBRATION AND REFERENCE BLOCKSIIW and IOW standard blocks shall be used for the calibration of UT instrument.The reference blocks according to XXXXXXCALIBRATION FOR TESTINGa) Manual ultrasonic weld testing shall be performed at a scanning sensitivity of DACreference sensitivity plus 6 dB minimum. All indications that exceed 50% of DAC screen height shall be evaluated.Figure 1. Reference Block for Manual UTb) With the transducer in Position A, maximize ( peak up ) the echo from theinside notch and adjust amplitude to at least 80% of full screen height. Measure the surface distance from the inside notch to the transducer exit point. Surface distance divided by measured wall thickness equals refracted angle tangent.Position the transducer in line with the outside notch at double the distance used to peak upthe inside notch (Position B). Verify that the outside notch echo peak is at or near zero depth reading. This will establish that refracted angle and velocity settings are sufficiently accurate.Figure 2. Establishing Distance, Refracted Angle, and Velocityc) Using two transducers of equal angle and frequency, one transmitting and the otherreceiving, maximize (peak up) the echo received. Measure the surface distance between the transducer exit points. Half the surface distance divided by measured wall thickness equals the refracted angle tangent. Without changing instrument settings, repeat this process on pipe with unknown velocity, refracted angle, and attenuation to determine any differences.Figure 3 Transfer Procedured) The reference level shall be adjusted to compensate for the differences in surfacecharacter and attenuation between the reference block and the material being tested, by means of the double probe technique.A transfer correction shall be performed and recorded once for each welded joint to betested using part of the test surface exhibiting the roughest condition, except for repetitive testing of the same materials, size and configuration, in which case a transfer correction shall be performed at the beginning of every shift by the ultrasonic operator. Calibration surfaces shall closely match that of the test surface to minimize corrections required. PRODUCTION TESTING PROCEDURESurface PreparationThe surfaces of welds and base metal shall be prepared as follows:a) Contact surfaces shall be free of weld spatter and any condition that might interfere withfree movement of the search unit or impair coupling of ultrasonic vibrations to and from the material examined. When the correction factor has been determined and used see par. 6.3.b) Finished weld surfaces shall be adequate to prevent interference with interpretation ofthe examination.c) Surfaces of the calibration reference blocks shall be of a similar finish to the part underexamination.Couplanta) A couplant material shall be used between the search unit and the test material. Thecouplant shall be either glycerin on cellulose gum and water mixture of a suitable consistently. A wetting agent may be added if needed. Light machine oil may be used for couplant on calibration blocks.b) Components may be tested using the same or different couplant as that used forsensitivity calibration.Scanning ProcedureStraight Beam Technique and Scanninga) At the time of test and prior to angle beam scanning of the weld, the entire base metalthrough which sound will pass during angle beam testing (determined by maximum surface distance required from the weld for the required skip distance) shall be scanned for laminar reflectors or inclusions which might interfere with the examination. If any area of base metal exhibits total loss of back reflection, or if an indication equal to or greater than the original back reflection height is located in a position that will interfere with the normal weld scanning procedure, its size, location, and depth from the face shall be determined and reported separately to Company.b) Where conditions are found to interfere with angle beam testing, other NDT methodsshall be employed.Angle Beam Technique and ScanningA) Generala) The technician shall be given the following information before weld testing iscommenced, and choice of angle(s) of refraction for scanning weld body sidewalk and reinforcement shall depend on the following factors:∙Type of ferritic steel.∙Groove type used.∙Characteristics and orientation of defects likely to occur i.e., the welding process (WPS) ∙Type of weld joint configuration to be tested i.e., the applicable range of diameter, thickness and local dihedral angle.b) A ccurate profiles shall be taken with wire type profile gauges or, if joint angle is acute, asuitably pliable material able to maintain its shape under normal conditions.B) Scanning Techniquea) Scanning may be in any pattern which results in full coverage of the root of the weld, thebody of the weld, and both side fusion lines and base metal heat affected zones.b) Scanning shall generally be performed at a gain setting 6dB above the ReferenceSensitivity Level for the maximum sound path. Evaluation of indications shall be done with the gain control at the Reference Level.C) Selection of Probesa) The nominal frequency shall be 2 to 5 MHz, unless variables, such as fabrication materialgrain structure require the use of other frequencies to assure adequate penetration or better resolution.b) Indications found in the root areas of groove welds in butt joints and along the fusion faceof all welds shall be further evaluated with either 70, 60, or 45 deg. angles, whichever is nearest to being perpendicular to the expected fusion face.D) Scanning PatternsFor girth welds, scanning for volumetric examination shall be carried out from both sides of the weld on the same surface.Indication InvestigationThe indications shall be investigated by maximising the echoes by rotating the probes and by using different angle probes with DAC curves. All indications exceeding 20% of the reference curve shall be investigated with and all indications exceeding 50% shall be reported. Investigation shall be performed to the extent that the operator can determine the shape and location o f the indication. For dimensional evaluation, either the “6 dB-drop”method or time of flight or maximum amplitude method shall be used.DISCONTINUITY EVALUATIONGenerala) Once a reflector has been found by scanning, it shall be carefully evaluated to determinethe following characteristics, as required for application of the Acceptance Criteria and for Reporting:∙Location from an established reference point.∙Location within the weld cross section.∙Sizes - i.e., length along the weld axis and width (height dimension) as seen in the weld cross section, or amplitude relative to reference level.∙Type and Orientation - i.e., classify as linear, planar or spherical reflectors. If planar, the orientation of the plane relative to the brace or chord side fusion boundaries.b) Discontinuities shall be evaluated by use of a combination of Beam Boundary andAmplitude Techniques.Defect Size DeterminationThe following technique shall apply to determine the defect size.a) The length of the discontinuity shall be obtained by recording the location along thelength of weld as determined by 50% of Reference Level (6dB drop) for each end of the reflector.b) The width (height) of the discontinuity shall be determined by 20dB drop (10%intentensity of the maximum echo) technique.Acceptance StandardAcceptance criteria are as Client’s Specification and xx code (根据实际要求)。