ASME标准磁粉探伤规程

ASME标准磁粉检测通用工艺规程

POE0702-CAL-ST-01

Calculation

For In-Place Strength Analysis For Submarine Pipelines

Rev. B

Employer : SONILS LDA

Engineer : SCOTT WILSON LTD, UK

Contractor : CHINA HARBOUR ENGINEERING CO., LTD.

Subcontractor: PETRO-OFFSHORE ENGINEERING

Issue Status

CONTENTS

1. GENERAL (3)

2. PERSONNEL (3)

3. DE S CRIPTION OF METHOD (3)

4. MAGNETIZATION EQUIPMENT AND CALIBRATION (3)

5. EXAMINATION MEDIUM (4)

6. MAGNETIZATION PROCEDUR E (5)

7. MAGNETIC FIELD STRENGTH (5)

8. EXAMINATION REQUIREMENTS (5)

POE0702-CAL-ST-01

1. GENERAL

1.1 This procedure is applied to the magnetic particle examination of ferromagnetic materials and welds for ASME Code items.

1.2 The magnetic particle examination method is suitable for detecting cracks and other discontinuities on or near the surface in ferromagnetic materials.

1.3 This procedure is applied to wet continuous magnetization by yoke, which shall only be applied to detect discontinuities that are open to the surface of the part.

1.4 This procedure shall be demonstrated to the satisfaction of the AI prior to implementation.

2. PERSONNEL

2.1 The NDE personnel who engage in magnetic particle examination shall be qualified and certified according to NJBST Co.,Ltd.’s “Written Practice for NDE Personnel Training, Examination, Qualification & Certification”(No.:QCD-011).

3. DESCRIPTION OF METHOD

3.1 In principle, the magnetic particle examination method involves magnetizing an area to be examined, and applying ferromagnetic particles to the surface. The particles will form patterms on the surface where cracks or other discontinuties cause distortions in the normal magnetic field. These patterns a re usually characteristic of the type of discontinuity that is detected.

3.2 The sensitivity of the magnetic particle examination is greatest for surface discontinuities and diminishes rapidly with increasing depth of discontinuities below the surface. Therefore, this method can only be used for detecting the discontinuities on or near the surface of the material or parts to be tested.

4. MAGNETIZATION EQUIPMENT AND CALIBRATION

4.1 The MT equipment to be used is Yoke, with Type CDX-4.

4.2 Calibration of Equipment

4.2.1 Frequency of calibration:

Each Magnetizing Equipment with an ammeter shall be calibrated at least once a year，or whenever the equipment has been subjected to a major electric repair, periodic overhaul or damage. If equipment has not been in use for a year or more, calibratioon shall be done prior to first use.

4.2.2 Calibration for lifting power of the Yoke

The lifting power will be calibrated with the methods of lifting a standard weight cake. Each alternating-current electromagnetic yoke shall have a lifting power of at least 10lb (44N). at the maximum pole spacing. Each direct-current electromagnetic yoke shall have a lifting power of at least 40lb (177N). at the maximum pole spacing.

5. EXAMINATION MEDIUM

5.1 The examination medium shall be the finely dividedferromagnetic particles which have high permeability and low retentivity. The size and shape of the magnetic particles shall be suitable for forming magnetic particle indications.

5.2 The black magnetic particles HK-1-400or 350, made by yixin Citong Co Ltd., shall be used.

5.3 The fluid medium for the magnetic suspension fluid shall be transformer oil, smelless kerosene or water. The temperature of the wet particle suspension and the surface of the part shall not exceed 1350F (570C).

5.4 Concentration of wet magnetic particle suspensions

5.4.1 The initial bath concentration of suspended magnetic particles should be

as specified of as recommended by the manufacturer and should be

checked by settling volume measurements and maintained at the

specified concentration on a daily basis. If the concentration is not

maintained properly, test results can vary greatly.

5.4.2 The bath concentration shall be maintained within 1.2 to 2.4 ml per 100ml of vehicle for nonfluorescent particles unless otherwise specified by the particle manufacturer.

5.4.3 Bath concentration is normally determined by measuring its setting volume through the use of an ASTM Pear-shaped centrifuge tube with a 1.5-ml stem (0.1-ml divisions )for nonfluorescent suspensions. Before sampling, run the suspension through the recirculating system for at least 30-min to assure thorough mixing of all particles which could have settled on the sump screen and along the sides or bottom of the tank. Take a 100-mL portion of the suspension from the hose or nozzle and allow it to settle for approximately 30 min. The volume settling out at the bottom of the tube is indicative of the particle concentration in the bath. If the bath concentration is low in particle content, add a sufficient amount of particle materials to obtain the desired concentration. If the suspension is high in particle content, add sufficient vehicle to obtain the desired concentration.

5.4.4 If the settled particles appear to be loose agglomerates rather than a solid

layer, take a second sample. If still agglomerated, the particles may have become magnetized, replace the suspension.

6. MAGNETIZATION PROCEDURE

6.1 Yoke Technique

6.1.1 The direct, alternating current electromagnetic yokes or permanent magnet

yokes shall be used for localized magnetization to form a longitudinal magnetic field.

6.1.2 The alternating current electromagnetic yoke shall have a lifting power of at least 10 lb. (4.5kg) at maximum pole spacing. The direct current electromagnetic yoke shall have a lifting power of at least 40 lb. (18.1kg) at the maximum pole spacing.

6.1.3 The field strength of yokes can be empirically determined by measuring its

lifting power.

6.1.4 Direction of magnetization: At least two separate examinations shall be carried out on each area. The second examination shall be with the lines of magnetic flux approximately perpendicular to those used for the first examination in that area.

6.1.5 The area to be examined shall be restricted to the area which is equal to 1/4 maximum pole spacing on both sides of the line through two poles. The pole spacing shall at least have 1in. (25mm) overlap each time.

7. MAGNETIC FIELD STRENGTH

7.1 The special carbon steel / copper plate type field indicator is used to verify that an adequate field strength and direction for the surface of part is obtained. If the clear magnetic particle pattern is shown on the copper plate side of the field indicator, it indicates that adequate field strength is obtained.

8. EXAMINATION REQUIREMENTS

8.1 Surface Preparation

8.1.1 Satisfactory results are usually obtained 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.

8.1.2 Prior to magnetic particle examination, the surface to be examined and all adjacent areas within at least 1in.(25mm) shall be dry and free of all dirt, grease, lint, scale, welding flux and spatter, oil, or other extraneous matter that could interfere with the examination.

8.1.3 Cleaning may be accomplished using detergents, organic solvents, descaling solution, paint removers, vapor degreasing, sand or grit blasting, or ultrasonic cleaning methods.

8.1.4 If coatings are left on the part in the area being examined, it must be demonstrated that indications can be detected through the existing maximum coating thickness applied. When AC yoke technique is used, the demonstration must be in accordance with Mandatory AppendixⅠof Article 7 of ASME Code SectionⅤ.

8.2 Unless specified on the drawings or other technical documentation, the magnetic particle examination shall be carried out on the parts with finished surface