Magnetic Particle examination of Welds (MT)



MT Should carried out as per article 7 of ASME Sec. V.

MT examination shall be performed in accordance with the written procedure certified by Manufacturer to be in accordance with the requirements of T-150 of ASME Sec. V

NDE personnel shall have a vision, with correction if necessary, to enable reading a Jeager type.2 standard chart at a distance of not less than 12” and shall be capable of distinguishing and differentiating contrast between colors used. This requirement shall be checked annually. Personnel shall be competent and duly certified in PT Techniques.
Evaluation of Indications (MT)

 Indications will be revealed by retention of magnetic particles in the orientation of the possible defects. All such indications are not necessarily imperfections. However, since excessive surface roughness, magnetic permeability variations (Such as at the edge of heat affected zone (HAZ) )etc., may also produce similar indications.

An indication is the evidence of a mechanical imperfection. Indications which have dimensions greater than 1/16” are considered Relevant

A linear indication is one having a length greater than three times its width.
A rounded indication is one of circular or elliptical shape with a length equal to, or less than three times its width.

Any questionable or doubtful indications shall be re-examined whether or not they are relevant.

Acceptance standards (MT)

These acceptance standards shall apply unless otherwise more restrictive standards are specified for specific material or applications as specified in the PO Specifications.
All surfaces shall be free of

Relevant linear indications;

Relevant rounded indications greater than 3/16”

Four or more relevant indications in a line separated by 1/16” or less, edge to edge
An indication of an imperfection may be longer than the imperfection that causes it; however, the size of the indication is the basis for the acceptance evaluation.



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