Document ID: chunk:federal_register_of_legislation:F2007L04654:body:0:p3
Version: federal_register_of_legislation:F2007L04654
Segment Type: other
Provision Reference: 
Character Range: 5653–8463

metal parts; or

(b) when the roughness of the surface to be inspected is such as to negate the greater sensitivity of fluorescent penetrants.

       2.2When the flaws located are small fatigue or stress corrosion cracks, or cracks which are 'tight' by reason of imposed or residual compressional stresses, fluorescent penetrant systems (Groups 4, 5, 6 or 7) must normally be used. The sensitivity of the system used must be, when the surface condition permits, equal to, or better than, that of a Group 6 system.

       2.3Post emulsification systems (Groups 2, 5 or 6) must not be used on surfaces which contain abrupt changes of section which would retain excess surface penetrant of varying depth.

       2.4The choice of method of developer must be based on the necessity to provide a thin even coating of developer over the surface to be inspected. Liquid suspended developers must not be used when the surface to be inspected contains abrupt changes of section (e.g. threads, splines, keyways or any abrupt concavity) at which the developer powder will be retained in excessive quantity. In such cases, dry developer powder must be used in conjunction with a fluorescent penetrant.

       2.5Only sulphur and chlorine free penetrant systems must be used on titanium and nickel based alloys.

Appendix II

This Appendix constitutes an approved dye penetrate process.

1 Surface preparation

       1.1Before application of penetrant, parts should be dry and clean. Every precaution must be taken to ensure that any flaws present will be free from foreign materials which would prevent the entry of penetrant or react with the penetrant in a manner detrimental to its efficiency.

Note   Strong acids such as chromic acid used in anodising and strong alkalis as used in some paint or carbon removers will reduce the fluorescent properties of dyes.

       1.2Where there is a danger of moisture being retained within flaws, the part must be thoroughly dried by heating to a temperature of not less than 70C nor more than 110C. The time at temperature must be not less than 40 minutes at 70C or 5 minutes at 110C.

       1.3Trichlorethylene vapour degreasing must be used to clean parts where possible. Where this is not possible, parts must be cleaned using solvent sufficiently volatile at ambient temperature to minimise the danger of cleaning fluid remaining in a flaw, e.g. kerosene or gasoline must not be used.

       1.4Cleaning of parts should not be undertaken by mechanical means which cause surface openings to be sealed (e.g. shot or glass bead peening, sand blasting etc.). If such mechanical treatment is unavoidable, it should be followed by a light cutting action such as that provided by hand sanding with sharp "wet and dry" papers, well‑lubricated with cleaning solvent of a