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July 2012 - Internal inspection

Written by Administrator
Sunday, 10 June 2012 16:11

Dear Readers,

We are pleased to publish on our Website a paper by Rich COSTANTINO, Goodrich Aerostructures, which was first published in the June 2012 PRI-NADCAP Non-Destructive Newsletter issue.

This paper is reproduced with the kind permission of the author(s) and the Performance Review Institute. © Performance Review Institute.

We draw your attention on two important points:

• A definition of the terms "endoscope", "borescope", "fibrescope" and "videoscope" (and not "borescope video"), quoted in this text is given in the EN 1330-10:2003 Non-destructive testing - Terminology - Part 10: Terms used in visual testing standard published by the European Committee for Standardization, Brussels, Belgium, 2003.

• The author quotes the"Labino UV Ligh". It is not the name of a specific UV-A source. Labino is a trade mark of the Swedish Company LABINO AB, which manufactures and markets UV sources. Many other manufacturers/suppliers of UV lamps supply as efficient UV-A sources. We do not endorse this choice.

We hope that this paper will be of some interest for you and bring you a top - quality information.

Patrick DUBOSC and Pierre CHEMIN

One of the most difficult forms of inspection utilizing Liquid Penetrant or Magnetic Particle techniques is the ability to evaluate internal surfaces of a product.

We are so familiar grabbing the UV light source, allowing for eye adaptation and beginning the inspection process that we sometimes get over zealous in thinking we can provide for adequate illumination to internal surfaces. Unfortunately, using standard inspection devices on products that have these internal surfaces may not always do the job. With internal surfaces on cylindrical shaped products or areas with passages whereby the standard UV light source cannot be used due to its size, other means of light illumination must be employed. There are items available that can be utilized to assist in this exercise.

Immediately UV borescopes come to mind. These can be quite helpful for small openings and curved surfaces, but can make inspection quite tedious.

Due to the minimized focal viewing area, the length of time for inspection can be quite lengthy as well. Techniques for manipulating this device to attain the proper UV intensity at the work surface, maintaining focus and indexing must be strictly followed for assurance of complete inspection.

UV borescopes are available in fixed diameter and length (rigid) for easy to access (straight) inside diameter sections. Complex parts/structures can be inspected with flexible fiber optic cable with a range of 4 way tip articulation to hone in on the inspection surface.

Various viewing heads such as right angle, bottoming, forward oblique and circumferential are available depending on the internal viewing requirement.

Video borescopes contain a camera that enables images to be viewed and recorded for archiving on a digital video recorder, computer hard drive or memory card. Unfortunately, these types of borescopes are quite costly since these systems can become quite complex compared to straight viewing devices.

Other methods of examination light sources could include UV light guides, pen lights, and even very high intensity external UV lamps such as the “Labino UV Light” where inspection can be performed with the aid of mirrors to reach into the part and examine through a mirror reflection. That said, there may be instances where accessibility is totally unattainable despite equipment at hand.

These limitations to the NDT method employed must be understood through communication from the Level 3 to the engineering organization (customer) who mandated the requirement to have complete understanding that these surfaces may necessitate another form of NDT to allow for 100% inspection. If 100% inspection is not feasible it may call for revision of the engineering drawing requirements showing those areas to be categorized "un-inspectable".

Again, when a requirement to perform FPI or MPI per a given specification does not define specific locations for inspection to be performed, this typically means that all areas of the part are required to be inspected. If this cannot be accomplished, get people involved.

The best way to resolve these issues is to communicate with your colleagues and come to an agreement on how to move forward.

Last Updated ( Sunday, 10 June 2012 16:25 )