All dwell times should be kept to a minimum and shall be not more than 2 min unless a longer time is qualified on a specific part. If meters have not been in use for one year or more, calibration shall be done before being used. If the penetrant is applied by spraying using compressed-air-type apparatus, filters shall be placed on the upstream side near the air inlet to preclude contamination of the penetrant by oil, water, dirt, or sediment that may have collected in the lines.
The minimum penetration time shall be as required in Table T or as qualified by demonstration for specific applications. The maximum dwell time shall not exceed 2 hr or as qualified by demonstration for specific applications. With color contrast penetrants, only a wet developer shall be used.
With fluorescent penetrants, a wet or dry developer may be used. Dry developer shall be applied only to a dry surface by a soft brush, hand powder bulb, powder gun, or other means, provided the powder is dusted evenly over the entire surface being examined.
Excess solvent removable penetrants shall be removed by wiping with a clean, dry, lint-free cloth or absorbent paper, repeating the operation until most traces of penetrant have been removed.
The remaining traces shall be removed by wiping the surface with cloth or absorbent paper, lightly moistened with solvent. To minimize removal of penetrant from discontinuities, care shall be taken to avoid the use of excess solvent.
Prior to applying suspension type wet developer to the surface, the developer must be thoroughly agitated to ensure adequate dispersion of suspended particles. Aqueous developer may be applied to either a wet or dry surface. It shall be applied by dipping, brushing, spraying, or other means, provided a thin coating is obtained over the entire surface being examined.
Blotting is not permitted. Nonaqueous developers shall be applied by spraying, except where safety or restricted access preclude it. Under such conditions, developer may be applied by brushing. For waterwashable or post-emulsifiable penetrants, the developer shall be applied to a dry surface.
For solvent removable penetrants, the developer may be applied as soon as practical after excess penetrant removal. Drying shall be by normal evaporation. Developing time for final interpretation begins immediately after the application of a dry developer or as soon as a wet developer coating is dry. The developer shall be applied as soon as possible after penetrant removal; the time interval shall not exceed that established in the procedure.
Insufficient coating thickness may not draw the penetrant out of discontinuities; conversely, excessive coating thickness may mask indications. Final interpretation shall be made not less than 10 min nor more than 60 min after the requirements of T If bleed-out does not alter the examination results, longer periods are permitted.
If the surface to be examined is large enough to preclude complete examination within the prescribed or established time, the examination shall be performed in increments.
The type of discontinuities are difficult to evaluate if the penetrant diffuses excessively into the developer. If this condition occurs, close observation of the formation of indication s during application of the developer may assist in characterizing and determining the extent of the indication s.
With a color contrast penetrant, the developer forms a reasonably uniform white coating. Surface discontinuities are indicated by bleed-out of the penetrant which is normally a deep red color that stains the developer. Indications with a light pink color may indicate excessive cleaning.
Inadequate cleaning may leave an excessive background making interpretation difficult. Illumination natural or supplemental white light of the examination surface is required for the evaluation of indications. The minimum light intensity shall be fc 1 lx. The light intensity, natural or supplemental white light source, shall be measured with a white light meter prior to the evaluation of indications or a verified light source shall be used.
Verification of light sources is required to be demonstrated only one time, documented, and maintained on file. With fluorescent penetrants, the process is essentially the same as in T The examination shall be performed as follows: a It shall be performed in a darkened area with a maximum ambient white light level of 2 fc Glasses or lenses worn by examiners shall not be photosensitive. Cracked or broken reflectors, filters, glasses, or lenses shall be replaced immediately.
Nonrejectable indications shall be recorded as specified by the referencing Code Section. Rejectable indications shall be recorded. As a minimum, the type of indications linear or rounded , location and extent length or diameter or aligned shall be recorded.
The total chlorine and fluorine content shall not exceed 0. This Appendix contains requirements for the control of contaminant content for all liquid penetrant materials used on nickel base alloys, austenitic stainless steels, and titanium. The chlorine content shall not exceed 0. Alternatively, the material may be decomposed in accordance with SD and analyzed in accordance with SD The sulfur content shall not exceed 0. The indications of cracks shall be compared as described in III A liquid penetrant comparator block shall be made as follows.
At the center of each face, an area approximately 1 in. The specimen shall then be immediately quenched in cold water, which produces a network of fine cracks on each face. After cooling, the block shall be cut in half. Two comparator blocks with closely matched crack patterns may be used.
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