Dominion NDT Services, Inc.

Liquid Penetrant Testing (PT), also referred to as Liquid Penetrate Inspection (LPI) or Dye Penetrant Inspection (DPI), is a widely applied and cost-effective inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics).

This inspection may be performed on ferrous and non-ferrous materials.

Penetrant Testing is used to detect casting, forging, and welding surface defects such as hairline cracks, surface porosity, leaks, and fatigue cracks on new and in-service components.

PT is one of the most widely used and cost-effective Non-Destructive Testing (NDT) methods. Its popularity can be attributed to two main factors: its relative ease of use and its flexibility.

Liquid penetrant inspection can only be used to inspect for flaws that break the surface of the sample. Some of these flaws are listed below:

• Fatigue cracks
• Quench cracks
• Grinding cracks
• Overload and impact fractures
• Porosity
• Laps
• Seams
• Pin holes in welds
• Lack of fusion or braising along the edge of the bond line

Magnetic Particle Inspection (MT) is used for defect detection of surface and near-surface discontinuities in ferrous materials.

Magnetic Testing is fast and relatively easy to apply; surface preparation of the component is not as critical as it is for some other NDT methods making it one of the most widely utilized nondestructive testing methods.

MT uses magnetic fields and small magnetic particles (very fine iron filings) to detect flaws in components.

The only requirement from an inspection-ability standpoint is that the component being inspected must be made of a ferromagnetic material such as iron, nickel, cobalt, or some of their alloys. Ferromagnetic materials are materials that can be magnetized to a level that will allow the inspection to be effective.

This method is used to inspect a variety of products including castings, forgings, and weldments.

Many different industries use magnetic particle inspection to determine a component’s fitness for use.

AWS Certified Welding Inspection API & ASME standards.

Visual Testing (VT) requires:

• line-of-sight contact with the portion of the specimen to be inspected,
• adequate illumination of the test specimen,
• a thorough understanding of the nature and origin of discontinuities and potential defects within the test object,
• and familiarity with the specifications controlling the inspection process.

Visual testing presents several real advantages: simplicity, rapidity, low cost, minimal equipment requirements, and the ability to be performed while the specimen is being used or processed.

Often Visual Inspection eliminates the need for further testing and the associated costs.

This method is used to inspect a variety of product forms including castings, forgings, machined components and weldments.

The structural steel, automotive, petrochemical, power generation, and aerospace industries are a few of the many types of end-users utilizing VT.

Ultrasonic Testing (UT) is completely non-destructive. The test piece does not have to be cut, sectioned, or exposed to damaging chemicals.

Access to only one side is required, unlike measurement with mechanical thickness tools like calipers and micrometers. There are no potential health hazards associated with Ultrasonic Testing, unlike Radiography.

When a test has been properly set up, results are highly reputable and accurate.

How It Is Used

Ultrasonic Testing uses (ultra) sound to detect internal discontinuities.

Ultrasound can be used on almost any material to locate discontinuities from large disbands down to the smallest defects. It can also be used to measure the overall thickness of a material, and the specific depth of a defect.

A common example of an ultrasonic thickness measurement would be to monitor the erosion of pipes and tank walls for integrity.

Radiographic Testing (RT) is a method of non-destructive testing, using both Conventional and Computerized Radiography, where many types of manufactured components can be examined to verify the internal structure and integrity of the specimen tested.

Industrial Radiography can be performed utilizing either X-rays or gamma rays. Both are forms of electromagnetic radiation that can be used in-house, on-site, and in the field.

The difference between various forms of electromagnetic energy is related to the wavelength.

X and gamma rays have the shortest wavelength and this property leads to the ability to penetrate, travel through, and exit various materials such as carbon steel and other metals.