Liquid penetrant inspection (LPI) is a cost-effective and non-destructive way of locating surface defects such as cracks, porosity, laps, seams, and other surface irregularities. Using dye penetrant inspection, you can determine whether ferrous, nonferrous, or non-porous materials (metals, plastics, ceramics) meet the required quality standards.

For finding faults on materials’ surfaces, liquid penetrant inspection (LPI), also called dye penetrant inspection (DPI)/penetrant testing (PT), was invented in the early 1940s. The essence of the test has not changed over the years, even though there are many ways to conduct it.

In this article, we’ll focus on liquid penetrant inspection and its advantages.

What Is Liquid Penetrant Testing?

Liquid penetrant testing is a non-destructive material assessment process that involves spreading a thin liquid dye across the material’s surface, followed by applying a developer to examine for flaws such as cracks. It’s a standard method for inspecting welds, pipelines, bars, and other materials for flaws.

It’s often used to inspect castings, forgings, and weldments for flaws. ATH NDT works with a wide range of industries, including aerospace, power generation, petrochemicals, and oil and gas, and we can conduct dye penetrant inspections on-site or in authorized laboratories.

Factors To Consider Before Liquid Penetrant Testing

A wide range of penetrant materials are available, and their selection is typically influenced by the test’s needed sensitivity level, the equipment available at the test site, and other factors:

  • There are two liquid penetrants: visible dye (colored red) and fluorescent dye (colored green-yellow).
  • Sensitivity ratings for fluorescent penetrants range from one to four, with four being the most sensitive for detecting the slightest faults.
  • Penetrants can be washed away with water, removed with a solvent, or treated with a lipophilic (oil-based) or hydrophilic emulsifier (water-based).

Process of Liquid Penetrant Testing

The testing process can be divided into the following steps:

  1. Pre-cleaning
  2. Penetrant application
  3. Penetrant dwell time
  4. Penetrant removal
  5. Developer application
  6. Developer dwell time
  7. Inspection
  8. Post-cleaning

Benefits of Liquid Penetrant Testing

Here are the significant advantages of liquid penetrant testing:

  • An exceptional sense of surface irregularities
  • Complex parts can be easily inspected.
  • Inspections can be performed quickly and cheaply on significant components and materials.
  • Inspections can be conducted on various material types (metallic, nonmetallic, magnetic, and conductive).
  • The part surface displays a graphical representation of the fault.
  • With aerosol spray cans, the process is portable, convenient, and affordable.
  • Flaw indications can offer information about the size, shape, and depth of the flaw.
  • This is a simple, quick, and relatively painless process.

Professional Liquid Penetrant Testing Service Provider

Our highly qualified experts at ATH NDT Limited have a minimum of Level II in PCN, ASNT, or NAS410 and have extensive liquid penetrant inspection expertise.

We can provide you with a quick response, round-the-clock testing, and a regional collection and delivery service if you choose ATH NDT Limited for dye penetrant examination. In today’s highly regulated markets, we can provide the inspection service that ensures your products or equipment fit the purpose and fulfill national and international standards.