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Non Destructive Testing: When Is Liquid Penetrant Testing the Best Method?

calendar Jul. 15, 2020user-iconTXNDT
TXNDT liquid penetrant NDT testing services

The job of an NDT technician is exciting and varied; the requirements of any given project or task may vary vastly, depending on the field, component, or the needs of the client.

Many nondestructive testing technicians revel in the rare variety offered by working in NDT. This unique field empowers technicians to work in industries as diverse as aerospace, renewable energy, and medical imaging, to name a few.

While exciting, the varied expectations of NDT technicians can be distressing. It can be overwhelming as a technician to know just which testing method will be appropriate for each job at any given time.

Today on the blog we answer the FAQ: When is liquid penetrant testing the best NDT method?

Here’s what you need to know.

Liquid Penetrant Testing Basics

While testing methods such as Visual Testing are fairly simple to understand and explain, liquid penetrant testing is a much more sophisticated method of nondestructive testing.

According to TXNDT’s testing disciplines page, “Liquid Penetrant uses the property of capillary action to find surface-breaking discontinuities in a variety of materials. Penetrant testing uses a low viscosity liquid (penetrant) that is applied to the surface of a test piece. Liquid Penetrant Inspection uses this capillary action to allow the penetrant to enter into fissures and voids that are open to the surface. After a dwelling time, the excess penetrant is removed, any remaining penetrant in the voids will flow back out, exposing the indication. There are a variety of techniques included in liquid penetrant testing, each dependent on the type of inspection and the type of flaws a technician is aiming to find.”


If you are debating whether or not to use liquid penetrant testing for a job, there are a number of considerations to make.

While somewhat complex to explain, liquid penetrant testing is actually a fairly simple testing method to implement. For newer NDT technicians, this may be a more reliable method of testing.

Liquid penetrant testing is also an excellent choice of NDT if you are working with a complex component. Regardless of part geometry, this method will yield results and it can be performed on a variety of materials.

Furthermore, liquid penetrant testing is a highly portable testing method if mobility is an important factor in your method-selection process.


In some circumstances, however, liquid penetrant testing may be a less efficient choice than other methods.

It is important to note that liquid penetrant testing is most effective on surface indications only. If a more thorough inspection is required, a different method may be best.

Primarily, careful cleaning before, during, and after testing is crucial to yield effective results. It is also important to fully clean a component after testing, which can be laborious.

Testing must be performed on a fully cleaned component otherwise you risk an obscured indication from testing. Because of this, there is a relatively high possibility of misinterpreting flaws.

Contact TXNDT Today!

Whether it is visual testing, magnetic particle testing, or ultrasonic testing, the best method for inspection must be decided on by a qualified technician, experienced enough to weigh the pros and cons of each method and determine which is the most efficient for the individual job.

At TXNDT, we make sure that each technician we train is fully prepared to enter the workforce. That training includes all of the most important methods, from magnetic particle testing, to liquid penetrant testing, and everything in between.

Since the requirements of an NDT technician can change from job to job, the expert instructors at TXNDT ensure that all prospective technicians are qualified to take on whatever their next job throws at them.

From introductory NDT courses to NDT level 3 certification, we take an active approach to educating all of our students and encourage all prospective technicians to take an active role in their own learning.

If you or your staff are looking for ways to expand your skills and broaden your career opportunities through nondestructive testing courses, consider NDT certification.

But don’t trust just any NDT school. If you’re looking for a top-tier experience, give us a call today at 281-231-0001 or check out our website for more information.