REVISION : 0 / PROCEDURE / PAGE : 2 OF 20
PROCEDURE FOR
MAGNETIC PARTICLE EXAMINATION ON
ON FERROMAGNETIC MATERIAL
as per
AWS D1.1
0 / 01 JULY 2001
REV. NO. / DATE / APPROVED BY :
NDT Level 3 / APPROVED BY : / APPROVED BY :
PROCEDURE FOR
MAGNETIC PARTICLE TESTING IN FERROMAGNETIC MATERIAL
(AWS D1.1)
TABLE OF CONTENTS
Description Page No.
1.0 Scope 4 of 20
2.0 Definition 4 of 20
3.0 Personnel Qualification 5 of 20
4.0 Equipment 5 of 20
4.1 Magnetizing Equipment
4.2 Magnetic Particles
4.2.1 Dry Particles
4.2.2 Wet Particles
4.2.3 Florescent Particles
4.3 Contrast Aids
4.4 Calibration Blocks
4.5 Flux Indicator
4.6 Black Light
4.7 Centrifuge Tube
TABLE OF CONTENTS CONT’D
Description Page No.
5.0 Equipment Checks and Calibration 8 of 20
5.1 Yoke Magnetizing Force
5.2 Induced Magnetic Field Strength and Direction
5.3 Black Light
5.4 Concentration of Wet Magnetic Particles
6.0 Testing Procedure 10 of 20
6.1 Surface Preparation
6.2 Testing Coverage
6.3 Magnetization
6.4 Particles Application
7.0 Viewing 11 of 20
8.0 Evaluation of Indications 12 of 20
9.0 Acceptance / Rejection Criteria 12 of 20
9.1 Statically Loaded Structure (AWS D1.1 Section 8.15)
9.2 Dynamically Loaded Structure (AWS D1.1 Section 9.25)
9.3 Tubular Structure (AWS D1.1 Section 10.17)
10.0 Reports 14 of 20
1.0 SCOPE
1.1 This procedure describes the method for Magnetic Particle Testing to be employed by the company Ltd.
1.2 This procedure is intended for the inspection of ferromagnetic material, low alloy carbon steel and non-austenitic alloy steels only.
1.3 This test may begin immediately after the completed welds have been cooled to ambient temperature. Testing for ASTM A514 and A517 steel shall be performed not less than 48 hours after completion of welds.
1.4 This procedure is written in accordance with the requirements of AWS D1.1 (1992 edition), of Section 6 and ASTM E709.
2.0 DEFINITION
a. Client Company or organization . .
b. NDT Non Destructive Testing
c. ASNT The American Society for Non Destructive Testing
e. PCN Personnel Certification for Non Destructive Testing
f. CSWIP Certification Scheme for Weld Inspection Personnel
3.0 PERSONNEL QUALIFICATION
3.1 All technicians that conduct Magnetic Particle Testing in accordance with this procedure shall be qualified in Magnetic Particle Testing Level II or Level III to a nationally recognised certification scheme.
3.2 Any one of the following nationally recognized certification schemes may be used for the purpose of qualification and certification of Ultrasonic Testing technician:
a. ASNT (in accordance with the company’s Written Practice).
c. PCN / CSWIP
4.0 EQUIPMENT
4.1 Magnetizing Equipment
4.1.1 A Magnaflux Y-7 AC Yoke or its equivalent shall be used for the magnetizing equipment.
4.1.2 The yoke shall capable of lifting a 4.5 kg weight of plate made of the same material to be inspected with the poles set at the pole spacing to be used..
4.2 Magnetic Particle
The finely distributed ferromagnetic particles used for the examination shall meet the following requirements.
4.2.1 Dry Particles
4.2.1.1 If dry particles are used the colour of the particles (dry powder) shall provide adequate contrast with the surface being examined.
4.2.1.2 The powder shall be applied by lightly dusting a small quantity over the surface and then removing the excess with a gentle air stream The air stream shall be controlled that it does not disturb or remove lightly held powder patterns.
4.2.1.3 In order to recognized the broad, fizzy, lightly held powder patterns produced by subsurface discontinuities, it is essential to observe carefully the formation of indications while the powder is being applied and also while the excess is being removed.
4.2.1.4 Adequate lighting shall be provided for easy observation of the indications.
4.2.1.5 Dry magnetic particle examination shall not be performed if the surface temperature of the part exceeds 315°C.
4.2.2 Wet Particles
4.2.2.1 If wet particles are used the colour of the particles shall provide adequate contrast with the surface being examined. The particle shall be suspended in a suitable liquid medium.
4.2.2.2 Either pre-packed aerosol can wet particles or own prepared wet particle (a suitable dry magnetic particles mixed with a suitable liquid) may be used.`
4.2.2.3 The test medium shall be applied by either flowing or spraying it over the surface. The spraying force shall be smooth that it does not disturb or remove weakly formed indication.
4.2.2.4 The temperature of the wet particle suspension and the surface of the part shall not exceed 55°C.
4.2.3 Florescent Particles
4.2.3.1 If florescent particles are used, the examination shall be conducted in a darkened area using filtered black light.
4.3 Contrast Aids
4.3.1 For color contrast particles, the ability to see magnetic cracks indications depends on the contrast between the color of the ink and the background. To improve the efficiency of the process the specimen shall be given a preliminary coat of white paint of an approved type to present a high contrast background to any black magnetic ink indicating the presence of the defects.
4.3.2 The contrast paint shall of a type which can be applied by aerosol can spray to give a thin, even coating and is quick drying. Propriety brands of Titanium Dioxide paint shall be utilised whenever possible.
4.4 Calibration Block
4.4.1 A 4.5 kg calibration block shall be used to test the strength of magnetising force of the yoke.
4.4.2 The block shall be made from the same material as the object to be inspected.
4.5 Flux Indicator
4.5.1 The strength and direction of induced magnetic field in the test material shall be check using flux indicator.
4.5.2 Any one of the following flux indicators may be used for this purposes.
a. ASME Magnetic Field Indicator, or
b. Burmah Castrol Magnetic Flux Indicator
4.6 Black Light
4.6.1 Black Light shall be used whenever florescent magnetic particle is used.
4.7 Centrifuge Tube
4.7.1 When magnetic particle bath is prepared at working site by mixing magnetic particle powder and a suitable liquid the bath shall be tested for concentration.
4.7.2 Centrifuge tube or flask shall be used to conduct the test.
5.0 EQUIPMENT CHECKS AND CALIBRATION
5.1 Yoke Magnetizing Force
5.1.1 The magnetizing force of yokes shall be calibrated annually or after any repair or overhaul. This shall be made by measuring the yoke’s lifting power. All calibration results shall be recorded and a calibration certificate issued.
5.1.2 Daily verification shall be carried out to ensure that the calibration criteria have been maintained. Test shall be conducted at the beginning and end of each shift.
5.1.3 The yoke must be capable of lifting and holding a 4.5 kg calibration block during magnetization at the maximum poles spacing to be used for inspection.
5.1.4 Yoke that fail to lift the calibration block shall not be used for inspection.
5.2 Induced Magnetic Field Strength and Direction
5.2.1 It may be necessary to check or demonstrate the presence and direction of magnaflux in the test object during Magnetic Particle Testing.
5.2.2 This test shall be conducted at the beginning and on test object to be tested on each Magnetic Particle Testing.
5.2.3 This shall be done using either Burmah Castrol Magnetic Flux Indicator or by using ASME Magnetic Field Indicator.
5.3 Black Light
5.3.1 The black light intensity at the surface under examination shall be measured at least once every 8 hours and whenever the work location us changed, using a meter which is sensitive to light in the ultraviolet spectrum and centered on 365 mano-meters (nm) or 3650 Angstrom (A).
5.3.2 The black light intensity at the examination surface, 380mm from the face of the light lens filter shall not be less than 800mW/cm2
5.3.3 The black light shall be turned on and allowed to warm up to at least 5 minutes prior to use.
5.4 Concentration of Wet Magnetic Particles
5.4.1 For own prepared wet magnetic particles, the concentration is normally checked by the use of a spear shaped centrifuge tube.
5.4.2 The test shall be conducted at the beginning of each test and every four (4) hours thereafter during testing.
5.4.3 A 100 ml portion of the test-medium is taken and allowed to settle for 30 minutes. The volume settling out at the bottom of the tube is indicate of the particle concentration.
5.4.4 The recommended concentration from a 100ml sample for fluorescent particles is between 0.1 and 0.5 ml inclusive and for non- florescent particles is between 1.2 and 2.4 ml inclusive.
6.0 TESTING PROCEDURE
6.1 Surface Preparation
6.1.1 Satisfactory results are usually obtained when the surfaces are in ; 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.
6.1.2 Prior to magnetic particle examination, the surface to be examined and all adjacent areas within at least 1 inch (25 mm) 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.
6.1.3 If coating are left on the part in the area being examined, it must be demonstrated that indications can be detected through the maximum coating thickness, either the coating shall be removed.
6.1.4 Cleaning may be accomplished using detergents, organic solvents, descaling solutions, paint removers, vapor degreasing, sand or grit blasting or ultrasonic cleaning methods.
6.1.5 For non-florescent a quick drying contrast paint may be used at areas where insufficient contrast between background and magnetic particles exist.
6.2 Testing Coverage
6.2.1 Testing object requiring Magnetic Particle Testing shall be tested for their full area unless partial or spot testing is specified by Client.
6.2.2 The surface shall be examined visually prior to any examination as to determine the suitability of the testing technique to be employed.
6.2.3 Two separate examinations shall be performed in each area with the lines of magnetic flux during which the second examination to be approximately 90° to those of the first examination.
6.3 Magnetization
6.3.1 The magnetization shall be included by a continuous magnetization of Alternating Current Electro-Magnetic Yoke.
6.3.2 The minimum poles spacing shall be 100 mm and the maximum spacing shall be 200mm.
6.3.3 However, the time for each magnetization shall not be to long to avoid over heating of the yoke.
6.4 Particles Application
6.4.1 The Ferromagnetic Particles shall be lightly dusted or sprayed on the work piece whilst the Magmetic Flux is being induced.
6.4.2 Sufficient time shall be allowed for indications to “Build Up” before evaluation.
7.0 VIEWING
7.1 Each entire surface under examination shall be viewed before proceeding to the next stage in the testing procedure and viewing shall be carried out after each excitation. Magnification of detail maybe obtained by the use of low-power magnifier. Care shall be taken to ensure that Magnetic indications have been inspected and recorded.
7.2 When viewing using color contrast inks or powder the area under examination shall be illuminated by daylight or artificial light to a level of not less than 500 lux. As guide this would be achieved by using either an 80 watt florescent tube at a distance of approximately 1 meter or a 100 watt pearl lamp at a distance of about 0.2 meter.
7.3 Viewing shall be such that the glare is avoided during inspection.
7.4 When using fluorescent inks or powders, the area under examination shall be darkened and the inspection of the test surface shall be carried out under black light conditions. The minimum light level shall be 800 mW/cm2 and shall be checked at least once during a work period.
7.5 Prior to viewing at least 5 minutes shall be allowed for the black light source to warm up and for the inspector eyes to become dark adapted.
8.0 EVALUATION OF INDICATIONS
8.1 Indications obtained in or adjacent area shall be evaluated in accordance with requirements of the referencing code section and will include linear inclusions and cracks of any length.
8.2 Care should be taken to avoid evaluation of false indications and/or non relevant indications.
9.0 ACCEPTANCE / REJECTION CRITERIA
Each discontinuity shall be accepted or rejected in accordance with Statically Loaded Structure (AWS D1.1 Section 8.15), Dynamically Loaded Structures (AWS D1.1 Section 9.25), or Tubular Structure (AWS D1.1 Section 10.17) whichever is applicable.
9.1 Statically Loaded Structure (AWS D1.1 Section 8.15)
9.1.1 The area shall have no cracks
9.1.2 Thorough fusion shall exist between adjacent layers of metals.
9.1.3 All crates shall be filled to the full cross section of welds, except for the ends of intermittent fillet welds outside their affective length.
9.1.4 For material less than 25.4mm thick, undercut shall not exceed 1mm, except that a maximum of 1.6mm is permitted for an accumulated length of 50mm in any 305mm.
9.1.5 For material equal to or greater than 25.4m thick, undercut shall not exceed 1.6mm length of weld.
9.1.6 The sum of diameter of visible piping porosity 1mm or greater in fillet welds shall not exceed 10mm in any 25.4mm and shall not exceed 19mm in any 305mm length of welds.
9.1.7 Complete joint penetration groove welds in butt joints transverse to the direction of computed tensile stress shall have no visible piping porosity.
9.1.8 For all other groove welds the sum of diameters of visible piping porosity 1mm or greater in fillet welds shall not exceed 10mm in any 25.4mm and shall not exceed 19mm in any 305mm length of welds.
9.2 Dynamically Loaded Structure (AWS D1.1 Section 9.25)
9.2.1 The area shall have no cracks.