基于美国ASME标准的磁粉检测规程.doc

CONTENTS1.Scope2.Qualification of NDE Personnel.3.Procedure4.Magnetizing Equipment and Material5.Surface Preparation6.Examination7.Evaluation8.Demagnetization9.Reexamination for repaired Area and Nonconformity Control10.Post Cleaning11.ReportSUSPENSION CONCENTRATION CALIBRATION RECORD MAGNETIC PARTICLE EXAMINATION INSTRUCTIONMAGNETIC PARTICLE EXAMINATION REPORT1.Scope1.1.This procedure is applied to detect cracks and other discontinuities on or near the surface of ferromagnetic materials, using wet magnetic particle and AC or DC yoke technique with continuous magnetization method1.2.This procedure is applied to welds and materials of ASME Code pressure vessels fabricated according to ASME Code Section Division 1.2.Qualification of NDE Personnel All personnel performing magnetic particle examination shall be qualified and certified in accordance with the requirements of HTs Written Practice for NDE Personnel Training, Examination, Qualification and Certification based on the requirements of“SNT-TC-1A”(Current Code accepted edition) 3.Procedure This procedure shall be supplemented by MAGNETIC PARTICLE EXAMINATION INSTRUCTION which shall be issued to every product to be examined and in which more detail parameters are specified. The Instruction shall be prepared by level ,approved by level NDE examiner,4.Magnetizing Equipment and Materials4.1 Magnetizing equipment4.1.1The magnetizing equipment shown in Table 1 shall be used. Table 1ManufacturerModelFactory No. TypeTechniqueSHE YANGCYE-1 030AC or DCYoke Technique4.1.2.Calibration of Equipment The magnetizing equipment shall be calibrated at least once a year, or whenever the equipment has been damaged. If the equipment has not been in use for a year or more, calibration shall be done prior to first use. The magnetizing equipment shall be calibrated in accordance with the requirements of MAGNETIC PARTICLE EQUIPMENT CALIBRATION PROCEDURE4.2.Magnetic Particle Field Indicator The magnetic particle field indicator shown in fig1 shall be used to demonstrate the direction of magnetic flux4.3 Examination Medium4.3.1Magnetic particle shown in Table 2 shall be used. The color of the particlesshall provide adequate contrast with the surface being examined. If it is notadequate, another color shall be select and redemonstration shall be required 更多资料：无损检测招聘网 中国无损检测论坛 中国焊接论坛 Table 2Manufacturer NameType/color FinenessShanghai MaterialRes. Institute Magnetic SlurryBW-1/Black 300 Mesh4.3.2.Water Vehicles and Suspension Mixing ratio of rater medium magnetic suspension is 11.0-22.0g magnetic slurry per 1000ml water.4.3.3 Concentration of Wet Magnetic particle Suspension The concentration is normally determined by measuring its settling volume through the use of an ASME pear-shape centrifuge tube. Before sampling, run the suspension for at least 30-min. to assure thorough mixing of all particles. Take a 100ml portion of the suspension and allow it to settle approximately 30 min. The volume settling out at the bottom of the tube is indicative of the particle concentration in the bath. Bath concentration shall be form1.2 to 2.4 ml per 100ml vehicles. The calibration shall be performed by MT levelor and reviewed by MT level NDE Examiner. The calibration results shall be recorded on CALIBRATION RECORD FOR SUSPENSION CONCENTRATION. 4.4 Illumination When natural light is not enough for examination and evaluation, adequate illumination is required ensuring adequate sensitivity during the examination and evaluation.5. Surface Preparation5.1 Satisfactory results are usually obtained when the surface is in the as-welded, as-rolled, as-cast, or as-forged conditions. However, surface preparation by grinding or machining may be necessary where surface irregularities could mask indications due to discontinuities.5.2 Prior to magnetic particle examination, the surface to be examined and all adjacent areas within at least 1 in. (25mm) shall be dried and free of all dirt, grease, lint, and scale, welding flux and spatter, oil or other extraneous matter that could interfere with the examination.5.3 Cleaning of the test surface may be accomplished by detergents, organic solvents, or mechanical means.5.4.When coating is left on the areas of the part being examined, all coating shall be removed prior to examination6.Examination Level examiner shall perform magnetic examination in accordance with the requirements of the Instruction, and shall record examination data on the MAGNETIC PARTICLE EXAMINATION REPORT .The temperature of the wet magnetic particle suspension and the surface of the part shall not exceed 135(57.3).6.1 Magnetizing Technique The AC or DC yoke technique shall be applied to detect discontinuities on the surface of the part. Except for materials 1/4 in. or less, AC yokes are superior to detect surface discontinuities.6.2.Method of Examination Examination shall be done by the “wet magnetic particle continuous method; that is, the magnetizing current remains on while the examination medium is being applied and while excess of the examination medium is being removed. The duration of the magnetizing current is typically on the order of 1-3s.6.3 Application of wet magnetic Particles Wet magnetic particle bath shall be applied by sparing, brushing or flowing over the area to be examined during the application of the magnetizing field. Care must be taken to prevent application before removing the magnetic field.6.4 Direction of Magnetization Each area must be magnetized in at least two directions approximately at right angle to each other so that all discontinuities on the surface of part may be detectable (see Fig.2). The indications are not normally obtained when discontinuities are parallel to applied magnetic field.6.5 Examination Coverage All examination shall be conducted with sufficient overlap to assure 100% coverage at the required sensitivity. The examination area shall be marked with line to satisfy 100% coverage as shown in Fig.2.6.6 Magnetizing Current Alternating or direct magnetizing current shall be used to establish part magnetization.6.7 Magnetic Field Strength for Yoke Technique The lifting power relates to the electromagnetic strength of the yoke. Alternating current electromagnetic yoke shall have a lifting power of at least 10lb(44.5N) at the maximum pole spacing that will be used. Direct current electromagnetic yoke shall have a lifting power of at least 40lb(178N) at the maximum pole spacing that will be used.6.8.Evaluation of System Sensitivity When it is necessary to verify the adequacy or direction of the magnetizing field, the magnetic particle field indicator described in Table 2 shall be used by positioning the indicator on the surface to be examined. A suitable flux or field strength is indicated when a clearly defined line of magnetic particles forms across the copper face of the indicator when the magnetic particles are applied simultaneously with the magnetic force. When a clearly defined line of particles is not formed, or is not formed in the desired direction. The magnetizing technique shall be changed or adjusted.7.Evaluation Level or NDE examiner shall observe and evaluate indications in accordance with the acceptance standards of ASME Code, and shall record evaluation result on the MAGNETIC PARTICLE EXAMINATION REPORT7.1.The illumination during observation and evaluation shall satisfy requirement of para. Discontinuities on the surface are indicated by retention of the examination medium. However, localized surface irregularities due to machining marks or other surface conditions may produce false indications.7.3.Broad areas of particle accumulation, which might mask indication from discontinuities, are prohibited, and such areas shall be cleaned and reexamined.7.4 Evaluation of Indications7.4.1 Indications will be revealed by retention of magnetic particles, all such indications are not necessarily imperfections however, since excessive surface roughness, magnetic permeability variations (such as at the edge of heat affected zoned), etc. may produce similar indications.Note: When examine corner welded joints such as nozzle to shell joint, adequate shoes shall be used to fit the shape being examined. The yoke fixed with shoes shall verify the lifting power required in Para.6.6. Fig.2 Max. Pitch and Direction for Yoke Technique. An indication is the evidence of a mechanical imperfection. Only indications, which have any, dimension greater than 1/6 in. shall be considered relevant. (a) A linear indication is one having a length greater than three times the width. (b) A round indication is one of circular or elliptical shape with a length equal to or less than three times its width. (c) Any questionable or doubtful indications shall be reexamined to determine whether or not they are relevant.7.4.2 Acceptance Standards These acceptance standards shall apply unless other more restrictive standards are specified for specific materials or applications within this Division. All surfaces to be examined shall be free of: (a)Relevant linear indications. (b)Relevant rounded indications greater than 3/16in. (c)Four or more relevant rounded indications in a line separated by 1/16in.or less, edge to edge. (d)An indication of an imperfection may be larger than the imperfection that causes it. However, the size of the indication is the basis for acceptance evaluation.8.Demagnetization When residual magnetic forth interfere the subsequent processing or usage, and equipped in the drawings, specification or purchase order, the part or area shall be demagnetized.8.1 Demagnetization Methods8.1.1 Withdrawal from Alternating Current Coil The fastest and most simple technique is to pass the part through a high intensity alternating current coil and then slowly withdraw the part from the field of the coil. A coil of 5000 to10000 ampere-turns is recommended. Line frequency is usually from 50 to 60Hz alternating current because of its inability to penetrate. Alternating-current yokes may be used for local demagnetization by replacing the poles on the surface, moving them around the area, and slowly withdrawing the AC yoke while it is still energized. Care should be exercised to assure that the part is entirely removed from the influence of the coil or AC yoke before the demagnetizing force is discontinued, otherwise the demagnetizer may have the reverse effect of magnetizing the part.8.1.2 Decreasing Alternating Current An alternative technique for part demagnetization is subjecting the part to the field while gradually reducing its strength to a desired level.8.1.3 Reversing Direct Current The part to be demagnetized is subjected to consecutive steps of reversed and reduced direct current magnetization to a desired level (This is the most effective process of demagnetizing large parts in which the alternating current field has insufficient penetration to remove the internal residual magnetization.). this technique requires special equipment for reversing the current while simultaneously reducing it in small increments.8.2 Effectiveness of the Demagnetizing Operation can be indicated by the use of appropriate magnetic field indicators or field strength meters. However, a part may retain a strong residual field after having been circularly magnetized and exhibit little or no external evidence of this field. Therefore, the circular magnetization