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Exposing 10 Common Misunderstandings about Penetrant Testing

We reveal common penetrant inspection misperceptions we’ve seen in the field in recent years

The liquid penetrant method of nondestructive testing has been used since the 1940’s. But even after being used by generations of NDT professionals, there are still some common areas of confusion or misunderstanding.

Here we set the record straight on 10 misperceptions we’ve seen in the field in recent years.

 

1. The highest sensitivity penetrant is the best penetrant for my application

The best penetrant for an application is the one that finds the right indications with the least amount of money and time. Sometimes this means not using the highest sensitivity penetrant.

While it is true that a higher sensitivity penetrant will produce indications for very small discontinuities, a higher sensitivity penetrant will probably not give you the best inspection results if you only need to find medium discontinuities since you will see far more indications than are relevant to the inspection.

To start selecting a penetrant, review any governing specifications and work procedures for required sensitivity levels.

Take into consideration the surface finish and configuration of the part.

A high sensitivity level fluorescent penetrant is appropriate for smooth, highly machined surfaces. However, a high sensitivity level fluorescent penetrant may leave excessive fluorescent background on a rough cast part, making inspection difficult. 

A lower sensitivity fluorescent penetrant is a better choice for rough surfaces.

 

2. A penetrant indication is a discontinuity

A penetrant indication is the visual results or response of the penetrant test which must be interpreted to determine its relevance.

Penetrant indications must be evaluated by a qualified inspector to determine if they are nonrelevant or relevant.

Nonrelevant indications may be present on parts because of inherent surface roughness or seams. Fingerprints or fibers may also cause nonrelevant indications.

Relevant indications are the result of a discontinuity, or interruption in the physical structure of an object, and are evaluated according to acceptance criteria. After evaluation, the part is accepted as is, reworked or discarded.

 

3. Water washable penetrants are water based

Some water washable penetrants are water based. However, this is not always the case. A penetrant can be water washable and not contain water.

Water-washable penetrants contain surfactants which allow the penetrant to be easily removed from the part surface with water rinsing, regardless of if they are water-based or oil-based.

 

4. Penetrants are only used on nonferrous metals

Penetrants can be used to inspect ferrous and nonferrous metals.

Penetrant inspection will find discontinuities open to the surface on ferrous and nonferrous metals.

Penetrant testing should not be done on porous surfaces, as the pores will act as discontinuities to trap penetrant and prevent accurate inspection.

 

5. Penetrant will be able to penetrate a discontinuity that contains water

Penetrant cannot seep into a discontinuity if it is already filled with water or other liquid.

Likewise, penetrant will not displace or penetrate through paint, particulate, oil or grease.

This is one of the reasons why an important prerequisite for a valid penetrant inspection is to start with properly cleaned and dried parts.

 

6. Tanks and an inspection booth are required for penetrant inspection

Penetrant inspection is easy to adapt to different environments and job sites.

Penetrant inspection systems with stationary tanks and booths are commonly seen in production environments. However, both fluorescent and visible dye penetrants are available in aerosol cans and kits for convenience and portability.

 

Check out our Penetrant Process Guide for a visual reference outlining each step in the various penetrant inspection methods and to learn 5 tips for penetrant testing

 

7. Penetrant is all that is needed to perform a penetrant inspection

At a minimum, penetrant and developer are required to perform a water washable penetrant inspection.

Additional products such as cleaner/removers and emulsifiers are required for solvent removable and post emulsifiable penetrant inspections.

 

8. Special lighting is required for penetrant inspection

Fluorescent penetrants do require inspection in a darkened area with specification compliant UV lighting. The UV lights may be mounted or hand-held for flexibility and portability.

Visible dye penetrants only require adequate white light, typically 100 foot candles minimum, for inspection.

 

9. Penetrant inspection should be the final check in a manufacturing process

Penetrant inspection is useful immediately after any manufacturing process which is known to cause discontinuities. This allows parts to be reworked or discarded earlier in the manufacturing process, which saves time and cost.

Penetrant inspection may sometimes be performed more than once during the manufacture of a part.

The placement of each penetrant inspection process should be optimized to locate manufacturing-induced discontinuities and reduce the amount of scrap or rework done later in the manufacturing process.

 

10. Penetrant inspection can take place at any point in the manufacturing process

As discussed, it is important to perform penetrant inspection after manufacturing operations likely to cause discontinuities open to the surface in parts.

However, care must be taken to perform penetrant inspection prior to mechanical operations that will smear the metal surface. Machining operations such as shot blasting, peening or grinding may close surface discontinuities, which can prevent subsequent penetrant inspections from finding these discontinuities.

Penetrant inspection should take place before machining operations like shot blasting, peening or grinding unless chemical etching can be used between these operations and the penetrant testing to reliably expose the discontinuities.

 

What other common misunderstandings or mistakes have you seen? 
Share your knowledge in the comments section below.

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Why AINDT?

American Institute of Nondestructive TestingThe American Institute of Nondestructive Testing not only offers training for exciting, high-demand careers with competitive salaries—we offer blended learning, which the U.S. Department of Education has found to be the most effective method of learning. AINDT's blended learning program combines flexible, affordable instruction as well as hands-on training to complete your course. Best of all, our online courses offer the ultimate flexibility. You can study, watch video lectures, and even complete quizzes on your iPad, iPhone, and Android devices! Instructors are able to teach active learning courses over the internet, and students can work at home on other assignments at their own pace, which helps stimulate self-directed learning. Instructors are free to offer more individualized assistance to those who need it, rather than being in a large lecture hall. AINDT's blended learning is designed to ensure success. Are YOU ready for an exciting new direction? Call AINDT for details today. Instructors are on hand waiting to speak with you! (855) 313-0325.

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Non-Destructive Testing and Inspection Market by Technique, Service, Vertical, and Geography

Non-Destructive Testing and Inspection Market by Technique, Service, Vertical, and Geography - Global Forecast to 2022
Source: Research and Markets, June 2016
http://www.researchandmarkets.com/publication/m8ung6o/3750332

"The Non-Destructive Testing (NDT) Market is Expected to Reach USD 11.39 Billion by 2022 at a CAGR of 8.30% Between 2016 and 2022"

"The non-destructive testing (NDT) and inspection market size was valued at USD 6.46 Billion in 2015 and is expected to increase to USD 11.39 Billion by 2022, at a CAGR of 8.30% between 2016 and 2022. The base year considered for the study is 2015 and the forecast period is between 2016 and 2022. This report provides a detailed analysis of the non-destructive inspection market based on technique, method, service, vertical, and geography. The demand for NDT is increasing all over the world due to regulations by governments for improving the overall safety of industrial assets, workforce, and the surrounding environment. Non-destructive testing is a process to test defects or discontinuities in materials, components, or assemblies without destroying its serviceability."

Click Here to read and evaluate this Global Forecast to 2022.

If you have questions regarding non-destructive testing or our complete Nondestructive Testing Certificate Program contact an AINDT Instructor today 855-313-0325.

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AINDT Difference

AINDT DifferenceNot all technical vocational schools are alike. AINDT offers the best of online vocational training, affordability, and hands-on training to get you certified in a rewarding new career. Non-destructive testing is a crucial field that is necessary in so many aspects of our daily lives, and offers a wide variety of industries to choose from including:

  • Aerospace
  • Aviation
  • Auto and boat racing
  • Construction
  • Manufacturing
  • Oil and gas development
  • Amusement parks
  • Railroad
  • Alternative energy—nuclear, wind, solar

The list is continually growing, and a career with AINDT offers you a rewarding, high-paying career in a needed industry that will never become obsolete. How many jobs can say that? Call today 855-313-0325 and speak with an instructor about vocational training with AINDT. Your exciting new career awaits!

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Research and Hard Work Land Dream Career

Recent American Institute of Nondestructive Testing (AINDT) shared his experience of finding a job after completing the program.

I’m writing to thank everyone at AINDT! I just accepted a job offer from a large NDT company in my area and I’m starting soon. I’m excited to start my NDT career and I couldn’t have done it without you guys. I was impressed during my hands-on training with how many students were getting calls from employers. I had calls and an interview during class and now after 3 interviews, I just got the job of my choice. It’s only 9 days after completing class and I was on vacation with no phone or email for 5 of those days! I did a lot of research before choosing NDT for my career path and then researched my NDT training options before choosing AINDT. I believe that there is no comparable program in the market today. AINDT is the best bang-for-the-buck in terms of return on investment in education. I worked hard, but still I can’t believe the opportunities that are now open to me based on the relative low cost and time investment at AINDT. I’ll make more in the next year than many college graduates with 4 years of education and massive student loans. Thanks again!

Rick Price

If you want to find out if a career in NDT is right for you, call and talk to an AINDT Instructor today!

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Non-Destructive Testing Equipment & Services Market Analysis & Global Forecast 2013-2020

Research and Markets: Non-Destructive Testing Equipment & Services Market Analysis & Global Forecast 2013-2020: GE Measurement & Control, Olympus, Nikon Metrology, Mistras & Zetec Dominates the $6.8 Billion Industry

Source: Press Release: Research and Markets – Wed, Jan 28, 2015 15:16 GMT

The American Institute of Nondestructive Testing (Baxter, MN) is following the global forecast for 2013-2020 from Research and Markets. There has been an addition in data that affects the global non-destructive testing market.

Here is an excerpt of the article:
"The demand for the NDT equipment used in inspections and quality has observed a significant growth and is expected to grow due to the increasing importance for quality control among industry players across various industry verticals. North America holds the largest market size in the NDT equipment due to increasing use of Non-Destructive Testing (NDT) in maintaining and inspecting the aging infrastructure and strict safety regulations implemented by the U.S. government which forces manufacturers to regularly engage in inspection activities."

Read the entire article here.

If you are interested in finding out more about nondestructive testing (NDT) and how you could start a career in NDT, call and talk to an AINDT instructor today!

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AINDT Adds the GE USM GO to it's training facility

b2ap3_thumbnail_USM-GO.jpgThe American Institute of NonDestructive Testing has added the GE USM GO to it's training facility. USM Go is setting new standards in flaw detection instrumentation. The new ultrasonic Go platform from GE's Inspection Technologies business combines a thickness gauge and a flaw detector in one single lightweight instrument. 

USM Go offers a wide range of applications: 

  • Weld Inspection
  • Inspection of Forgings and Castings
  • Inspection of Rails
  • Inspection of Composites

For more information about the GE USM Go device, visit www.gesensinginspection.com.

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