Dye Penetrant Testing DPI

Whether in house using our penetrant line or out on site Flawed can carry out Penetrant inspection in-line with qualified procedures.

Our technicians are qualified to at least PCN Level 2.

We offer all forms of penetrant inspection including both colour contrast and fluorescent consumables.

We have a history of successful work for many clients on ranging projects including Nuclear, Petrochemical, shipbuilding ad more.

Learn About Penetrant Testing, What is it?

Dye penetrant inspection, also commonly referred to as liquid penetrant inspection or penetrant testing, is a popular nondestructive testing (NDT) and evaluation technique used to detect surface flaws on components used in the aerospace, power generation, military, construction and manufacturing industries, among others. This NDT technique can even be used in geology and archaeology because it is gentle on a variety of materials.

Dye penetrant inspection can be applied to many different materials and substances including but not limited to metals, ceramics, plastics, glass and rubber. Because the penetrant or dye is intended to seep and soak into surface defects, this form of inspection is best reserved for non-porous objects. The inspection should be performed by properly trained and qualified inspectors upon a flat and clean surface in a carefully controlled environment to obtain the best results.

Penetrant testing highlights flaws that are open to the surface of the object being tested, defects that are often too small, too slight or too difficult to see during a routine visual inspection. The types of surface flaws that can be detected with dye penetrant inspection include hairline cracks, pitting, leaks, unintended porosity, fatigue, scratches, pin holes, seams and lack of fusion along welds or bonds.

Dye penetrant inspection can be performed with fluorescent dye or “visible dye,” the latter of which is typically red in color (so it will contrast sharply with the white developer that is applied after the dye). This type of inspection can be conducted inside a dedicated inspection facility or out in the field, which allows for greater flexibility when testing operational components that are currently in service. In addition to portability and convenience, another reason why liquid penetrant inspection is so popular is it can be used on items as small as bearings that fit in your hand or as large as power plant turbines. The dye or penetrant can be sprayed on when testing the surface of a large object.

Penetrant testing is great for machined surfaces, pipework, casting, forging and welding. Some common welding defects that can be revealed using dye penetrant inspection include undercuts, underfills, slag inclusions, tungsten inclusions, pin holes and more. Penetrant testing can locate fatigue flaws at connection points between components, grinding cracks, impact fractures, unintended seams, and other problems.

Dye penetrant inspection begins with a cleaning to remove contaminants that might generate false positive results. For example, the metal smearing that can occur during machining or grinding must be removed; other substances that must be removed include paint, oils, finishes, dirt, dust and grit. Next the dye or penetrant is applied and allowed to soak in for 5 to 30 minutes, a time period referred to as “dwell time.” (If surface flaws are minuscule, a longer dwell time might be required for the dye to penetrate properly.)

Next, excess dye is cleaned off and a liquid or powder developer is applied. The developer creates a light or white background which makes the dyed defects easier to spot. The dye is said to “bleed out” as the developer draws the dye forward. At this stage the inspector will document any flaws and note their size, position, orientation and type. When the inspection is completed, the object is cleaned to remove any traces of developer or penetrant.

Although this form of nondestructive testing has many advantages, it is not appropriate for all situations. When product or component defects are located deeper within and do not reach the surface of the item being inspected, another form of nondestructive evaluation is required. Also, it is important to select a penetrant and a developer that is appropriate for the specific type of material being inspected to avoid accidental damage and to generate accurate results.

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