Weld defects observed during visual inspection/pressure tests/NDT, shall be rectified by removing the defective materials by grinding/chipping/machining/flame gouging up tothe sound metal. Adequate steps aretaken so that the above process of defective materials does not penetrate the parent metal to any substantial amount beyond the depth of weld penetration unless cracks or other defects exist in the parent metal. A crack or any other defects like lack of fusion/lack of penetration etc, is removed throughout its length, to ensure that the whole of defect is removed. Material beyond 25 mm of each end is removed
Weld of repaired portion after removal of complete defective material and ensuring by D P Test that the groove profile has reached the sound metal. Rewelding is done following approved welding WPS.
This procedure details penetrant testing method that provides a means for detecting of defects open to the surface such as cracks, porosity, etc through leaks in welds.
ASME Boiler and pressure vessel code section –V –Article 6 shall be followed
Unless otherwise agreed, personnel well experienced and qualified in accordance with ASNT –TC –1A –L –1 shall perform the test under supervision of certified ASNT –TC –1A Level II personnel.
Visible, solvent removable penetrant with non-aqueous wet developer technique shall be used.
5.1. On surfaces in the as-welded condition satisfactory results can usually be obtained. Surface preparation by grinding or machining is necessary when surface irregularities might make the indications and interfere with the effectiveness of the examination.
5.1.1 All the areas of the parts to be tested shall be dry and free from extraneous materials like rust, scales, spatters, grease, oil, and dirt, paint which can interfere and prevent the penetrant from entering discontinuities. The adjacent area up to about25 mm of the surface to be tested shall be cleaned by appropriate cleaning methods. Typical cleaning agents, whomay be used, are detergents, organic solvents deskillingsolution and paint removers. Degreasing and ultrasonic cleaning methods may also be used.
5.1.2 Surface cleaning processes such as shot/sand/grid blasting, liquid homing, emery clothing, and wirebrushing, metal scrapping shall be avoided. These processes tend to close the discontinuities by peening or cold waving the surface of the specimen.
5.2 Surface to be tested shall be thoroughly dried after cleaning. The temperature of the parts to be tested shall be within the range of 16degree to 52 degree Celsius.
5.3 The visible color contrast type penetrant shall be applied uniformly by spraying, brushing, tipping stabbing etc over the surface area of the parts to be tested.
5.3.1 After penetrant application a minimum dwell time of ten to fifteen minutes shall be allowed to ensure proper penetration of the penetrant into the defects.
5.4 Excess penetrant shall be removed by wiping with a lint free material. Then wipe with lint free material lightly wetted with solvent (cleaner) until the remaining traces of the excess penetrant of the surface have been removed. Flushing of surface with excess solvent is prohibited. After removal of excess penetrant as above, the surface shall be allowed to dry by nor5mal evaporation of solvent.
5.5 A thin uniform coat of non-aqueous developer shall be applied on the surface under test by spraying after removal of excess penetrant and drying. The developer shall be agitated thoroughly to ensure proper mixing of powder with the solvent, before application. Proper development time is a very important factor in the interpretation of the indications. If too little time is allowed, indications may not have time to develop. Too much time will cause indications to become blurred or distorted.
6.1 Bleeding out the penetrant reveals mechanical discontinuities at the surface. Localized surface discontinuities, such as surface pits may produce defects indications. Such indications are considered non-relevant. Any indication believed to be non-relevant shall be re-examined to verify whether or non-actual defects are present. Resurface preparations at such areas shall precede the reexamination.
6.2 Linear indications are those indications in which, the length is more than three times the width. Only indications with major dimensions greater than 1.6 mm shall be considered relevant.
6.3 Rounded indications are indications, which are circular or elliptical with the length less than three times the width.
7.1 The criteria specified in the relevant standards shall be referred for acceptance.
7.2 Unless otherwise specified, all surfaces shall be free from
a) Relevant linear indications.
b) Relevant rounded indication > 4.8 mm.
c) Four or more rounded indications in a line separated by 1.6 mm or less (edge to edge).
In case of unacceptable indications, repairs shall be carried where necessary and repaired area tested.
After evaluation of indications the developer and residual traces of penetrate(if any) shall be removed be water spray rinsing.
PT Test report shall contain the details indicated in the enclosed format.