A Look at Liquid Penetrant Testing and Alternatives
Liquid penetrant testing (LPT), also known as liquid penetrant inspection (LPI) and dye penetrant inspection (DPI), is the most commonly used non destructive testing method to check for defects in non-porous materials. It’s also one of the oldest and simplest surface inspection techniques. Essentially, this testing method leverages capillary action or liquid’s ability to flow into narrow, clean spaces unaided or opposed by external forces (e.g. gravity). Leveraging capillary action allows LPT to detect surface-breaking defects. Let's take a closer look at LPT:
How LPT Works and Why it’s Commonly Used
Liquid penetrant testing works by emitting a coloured or fluorescent dye from flaws within a non-porous surface. The testing process unfolds in the following steps:
· An item is thoroughly cleaned
· Liquid penetrant is applied and given time to soak in or “dwell”
· Excess liquid is wiped off and a developer is applied, aided by the capillary action
· A visual inspection utilizes ultraviolet light to reveal defects
LPT is one of the most non destructive testing techniques because it’s flexible and easy to use.
Not to mention, the method can be used to effectively detect defects on plastic, glass, metal, rubber, and ceramic surfaces.
Disadvantages of LPT
Although LPT is one of the most effective techniques for detecting defects on surfaces, it also has some drawbacks. For example:
· LPT only reveals flaws that break the surface of an item
· The technique doesn't provide any information on a defect’s severity or complexity
· The initial clean-up stage can be time consuming, as any contaminants can disrupt the results
· Chemicals used during the process are toxic and must be carefully disposed of
· It’s simply a screening tool that must be accompanied by more advanced techniques
Alternative Solutions to LPT
While LPT is an effective method of testing for a wide variety of applications, it may not be the best suited for detecting defects in every situation. For some jobs, alternative or more advanced tests are needed. The two most common alternatives to LPT are Eddy Current Testing (ECT) and Eddy Current Array (ECA).
· ECT is a method that utilizes electromagnetic current from copper wire to detect and describe surface-breaking, near-surface, and far-surface flaws. The technique offers quick results, thus saving time and money. With this testing, surface prep and chemical waste are not needed
· ECA is even more advanced than ECT, as it uses coils arranged in rows to cover a larger area. Covering a larger area produces an even faster scan and offers greater detection capabilities.
If you're looking to find a form of non destructive testing that will provide you with the data you need in a timely and cost-effective manner, contact us to discuss your project's unique requirements.