Document ID: chunk:federal_register_of_legislation:F2011C00880:body:0:p4
Version: federal_register_of_legislation:F2011C00880
Segment Type: other
Provision Reference: 
Character Range: 8598–11448

either side of the coil must be inspected at any one time.

(c) The pitch of the turns of the magnetising coil used must be as small as practicable.

       2.4 Magnetic flow method of magnetisation

(a) The pole pieces of permanent magnets or electromagnets used for the magnetic flow method must be adjustable to conform with the surface of the part to be inspected so as to provide an area of contact as large as possible. The area of contact should be not less than the cross sectional area of the smallest component of the magnetic circuit.

(b) To ensure a sufficient flux density for inspection, the surface to be inspected must first be magnetically saturated, as shown by furring. Saturation may be accomplished by adjusting the current through the coil of the electromagnet, in the case of a permanent magnet, adjusting the spacing of the pole pieces. The flux density should then be reduced until furring just disappears.

Note   For guidance, when permanent magnets or electromagnets without provision for varying the pole spacing are used, the pole spacings of magnets of 15 kg and 25 kg lift should not exceed 100 mm and 150 mm respectively.

3 Application of magnetic particles

       3.1 Wet continuous process

       The magnetic particle suspension must be applied to all surfaces of the part which are to be inspected. It must be flowed over the part to produce a smoothly flowing layer and must be applied immediately before and during magnetisation. The application must cease before magnetisation is terminated to avoid washing away lightly held flaw indications.

       3.2 Wet residual process

       After the part has been magnetised to saturation, the magnetic suspension must be applied. The application may be by flow coating but preferably by immersing, gently agitating and gently withdrawing the part from a well-mixed bath.

       3.3 Dry process

       The magnetic particles must be caused to be present as a cloudy suspension in air adjacent to all surfaces to be inspected while the part is being magnetised.

4 Inspection

      4.1 When non-fluorescent magnetic particles have been used, inspection must be undertaken under good conditions of white light illumination, providing an intensity of not less than 1080 lumen m­² or 100 foot candle, at the surface to be inspected, when measured with a Weston Light Meter, Model 703, type 51 or equivalent. Excessive reflection from polished surfaces must be avoided.

      4.2 When fluorescent magnetic particles have been used, parts must be inspected under ultraviolet light in conditions of darkness or near darkness. Inspection lamps must contain a filter to minimise the intensity of visible light and harmful ultraviolet light of wavelength less than 3,000A whilst permitting maximum transmission of ultraviolet light of wavelength approx. 3,650A.