The Liquid Penetrant Dye(LP) process is one of the oldest forms of non-destructive testing. It is widely used due to the ease of the process and because it can be used on almost any material. Liquid Penetrant Dye testing uses capillary action to reveal surface breaks and makes the flaws appear larger. It provides high contrast between background and the indicator, making defects easier to identify.
The Liquid Penetrant Dye process requires a clean surface; it is crucial that there is no water, grease, or any other contaminant that could prevent the penetrant from entering and exposing flaws. Once the Liquid Penetrant Dye is applied, it must be left on the part long enough to allow it to seep into any defects. This time period is known as the “penetrant dwell”, and is determined by the type of penetrant and the material being tested. Optimizing the dwell time requires a thorough understanding of how different types of Penetrant Dye work with different substrates. At the end of the dwell period, the extra penetrant is removed from the surface. This must be done very delicately as not to remove any from the cracks. Afterwards, a thin coating of a substance known as developer is added in order to pull the penetrant to the surface, making it visible under proper lighting conditions. After a few minutes, the part is ready to be inspected for defects.
At Pacific Magnetic & Penetrant, we hold various certifications for dye penetrant inspection, and specialize in the testing of critical components for demanding industries such as Aerospace. We offer several variations, including water washable, lipophilic, and hydrophilic penetrant methods to accommodate a wide range of materials, discontinuity types, and sensitivity requirements. For more information see the table below, or contact us directly.