Published on 18-Feb-2020

Alternative Methods for Liquid Penetrant Testing

Alternative Methods for Liquid Penetrant Testing

Table of Content


There are many non-destructive testing techniques. They’re not all suited to every type of application.

For example, electromagnetic testing techniques don’t work on most composite materials, while X-rays and computed tomography are perfect.

Similarly, ultrasounds are very versatile but require direct contact and appropriate coupling with the surface under test, which is not always possible.

What is Liquid Penetrant Testing?

One of the most common, low-cost solutions (and one of the oldest) to Non-destructive Testing challenges is liquid penetrant testing (PT), also known as liquid penetrant inspection (LPI) and Dye Penetrant Inspection (DPI).

The NDT Technique leverages capillary action—the ability of a liquid to flow into narrow spaces without the assistance of, or even in opposition to, external forces like gravity—to detect surface-breaking defects.

After applying the penetrant and letting it dwell for a certain period of time, the excess is removed and a developer is applied.

The developer draws the penetrant from surface-breaking defects where it seeped, revealing their presence.