Dye Penetrant Inspection Procedure

This article provides you with a example dye penetrant inspection procedure. This procedure contains water washable process with both visible and fluorescent systems.

SCOPE

This  procedure establishes the general requirements of Penetrant Testing of ferrous and non-ferrous components (essentially non-porous) and welds by Water Washable Process, Visible and Fluorescent Penetrant Systems and are to be followed by NDT personnel Third Party.

PURPOSE:                    

Ø  The requirements are intended to detect discontinuities that are open to test-surface and free from contaminants by interpreting the surface indications and evaluating them in accordance with the applicable referenced codes, standards or specifications by certified NDT personnel qualified in PT to Level II.

Ø  Customer’s approved specific Inspection/Evaluation manuals have also to be followed strictly, if available and applicable.

Ø  Any conflicts between any points of this procedure and the referenced documents or job specifications of customer shall be resolved (if given in writing) by the appointed ASNT NDT Level III or the Divisional Manager (NDT) or his authorised representative.

Ø  Where special circumstances require unique techniques of Penetrant Testing by Water Washable Process, specific technique sheets shall be attached as Annex: IV etc., with the written approval of NDT Level III.

SUMMARY OF TEST METHOD & WATER WASHABLE PENETRANTS         

Ø  A liquid penetrant which may be a visible or a fluorescent material is applied evenly over the surface being examined and allowed to enter open discontinuities.  After a suitable dwell time, the excess surface penetrant is removed.  A developer is applied to draw the entrapped penetrant out of the discontinuity and stain the developer.  The test surface is then examined to determine the presence or absence of indications.

Note: Caution - Fluorescent penetrant examination shall not follow a visible penetrant examination because visible dyes may cause deterioration or quenching of fluorescent dyes.

Ø  Processing parameters, such as surface precleaning, penetration time and excess penetrant removal methods, are determined by the specific materials used, the nature of the part under examination, (that is, size, shape, surface condition, alloy) and type of discontinuities expected.

Ø  Liquid penetrant examination methods indicate the presence, location and, to a limited extent, the nature and magnitude of the detected discontinuities.  Each of the various methods has been designed for specific uses such as critical service items, volume of parts,  portability or localised areas of examination.  The method selected will depend accordingly on the service requirements.

Ø  Water-Washable Penetrants are designed to be directly water-washable from the surface of the test part, after a suitable penetrant dwell time.  Because the emulsifier is “built-in” to the water-washable penetrant, it is extremely important to exercise proper process control in removal of excess surface penetrant to ensure against overwashing.  Water-washable penetrants can be washed out of discontinuities if the rinsing step is too long or too vigorous.  Some penetrants are less resistant to overwashing than others.

Ø  Post-Emulsifiable penetrants with lipophilic and hydrophilic emulsifiers are not included in this procedure.