Liquid Penetrant Method

General

 The complexity and expense of today's machines, equipment, and tools dictate the use of fabrication and testing procedures that will ensure maximum reliability.

Nondestructive testing (testing without destroying) provides many of these procedures. Of the number of nondestructive testing procedures available, liquid penetrant testing – of which this course is concerned – is one of the most widely used.

Purpose

The purpose of this course is to provide the fundamental knowledge of liquid penetrant testing required by quality assurance and test personnel to enable them to:

ascertain that the proper test technique, or combination of techniques, is used to assure the quality of the finished product

interpret, evaluate, and make a sound decision as to the results of the test

 recognize those areas of exhibiting doubtful test results that require either retest or assistance in interpretation and evaluation

Industrial Applications Of Liquid Penetrant Testing

Because of the basic characteristics of liquid penetrant testing, it is used to test a variety of both metallic and nonmetallic materials such as welds, forgings, castings, plastics, and ceramics, etc.

Since liquid penetrant testing is capable of economically revealing surface discontinuities (variations in material composition) in a variety of dissimilar materials, it is one of the most effective tools available to quality assurance personnel.

Testing Philosophy

Personnel

It is imperative that personnel responsible for liquid penetrant testing be trained and highly qualified with a technical understanding of the test equipment and materials, the item under test (specimen), and the test procedures.

Quality assurance personnel must be equally qualified. To make optimum use of liquid penetrant testing, personnel conducting tests must continually keep abreast of new developments. There is no substitute for knowledge.

Testing Criteria

Modern manufacturing procedures dictate that faulty articles be discovered as early in the manufacturing process as possible. This means that each item must be tested individually before it is required to perform in a subassembly and that each subassembly be tested before it is required to perform in an assembly, etc.

 This building–block approach requires that test processes be selected and test procedures be generated at the lowest level in the manufacturing process in order that the highest reliability may be obtained with lowest cost.

Test Procedures

Approved procedures for liquid penetrant testing are formulated from analysis of the test specimen or article, review of its past history, experience on like or similar specimens, and information available concerning discontinuities in similar articles.

It is the responsibility of personnel conducting or checking tests to ensure that test procedures are adequately performed, and that the test objective is accomplished.

  Procedures found to be incorrect or inadequate must be brought to the attention of responsible supervision for correction and incorporation into a revised procedure.

Test Objective

1. 

The objective of liquid penetrant testing is to ensure maximum reliability by providing a means of:

a.

Obtaining a visual image related to a discontinuity on the surface of the specimen under test.

b.

Disclosing the nature of the discontinuity without impairing the material.

c.

Separating acceptable and unacceptable material in accordance with predetermined standards.

2. 

No test is successfully completed until an evaluation of the test results is made. Evaluation of test procedures and results requires understanding of the test objective as well as a knowledge of the material from which the test article is made. It also requires a knowledge of the manufacturing processes that were involved.

For more information :
                            ndt@kiccnet.com