Conventional NDT


Non-destructive Testing (NDT), also known as non-destructive examination (NDE), refers to any testing or inspection method that does not permanently damage or destroy the equipment or material being tested. This is opposed to destructive testing, in which the part being tested is rendered inoperable, or destroyed, during the testing process.

NDT is an incredibly common and important practice in many industries, including oil & gas, petrochemicals, chemical processing, aerospace, and manufacturing. NDT is frequently used to find discontinuities, flaws, or corrosion in materials.

Conventional NDT is comprised of a number of different testing methods, most of which rely on either sound or electromagnetic waves to examine materials.

Sentinel Integrity Solutions offers a wide array of conventional NDT applications for turnaround and on-stream inspection activities, including ultrasonic testing (UT), liquid penetrant inspection (LPI), magnetic particle testing (MPT), positive material identification (PMI), and conventional radiography (RT).



Ultrasonic testing (UT) is a conventional NDT technique that can be used to obtain thickness measurements of materials and detect defects in welds. Ultrasonic testing works by transmitting ultrasonic pulse waves into a material in order to verify if any flaws are present. Once emitted, these waves reflect either off the far wall or off of any cracks or defects that happen to be in its path. The time it takes for the wave to return can be measured to see if there are any defects in the wall. The results of the examination are then displayed on a screen for examination.



Magnetic particle testing (MPT) is a nondestructive examination (NDE) technique that is primarily used for detecting surface and slightly subsurface discontinuities in ferromagnetic materials. This method works by creating a magnetic field around the part to be tested. The field will distort around the surface or near surface cracks, creating what is known as a flux leakage field.

During the inspection, ferrous iron particles with dye are applied to the part. These particles can be either wet or dry. If an area of flux leakage is present, the particles will be attracted to this area and form an indication. Following identification of the affected area, an evaluation will determine if the indication it is relevant or non-relevant.

The magnetic field can be introduced into the test specimen by either direct or indirect magnetization. Direct magnetization occurs when the electric current is passed through the test object and a magnetic field is formed in the material. Indirect occurs when no current is passed through the test specimen, but a magnetic field is applied from the outside source.



Positive Material Identification (PMI) is the process of identifying and analyzing the chemical composition of various metal alloys. Being able to verify the correct metallurgical composition of materials is imperative to running a safe and reliable facility. Introducing parts into an environment in which they are not designed to function can lead to equipment failures and/or process safety incidents.

In the past, installation of incorrect metallurgy has caused catastrophic failures in the refining and petrochemical industry. PMI provides a necessary safeguard against human error and deliberate fraud. Some components may have had their composition either intentionally or accidentally misidentified.

Sentinel Integrity provides highly trained technicians to meet our clients’ PMI needs. We offer two methods of conducting PMI: X-ray Fluorescence (XRF) and Optical Emission Spectroscopy (OES). 




Liquid penetrant testing (LPT) is a nondestructive testing technique for detecting surface defects on both ferromagnetic and non-ferromagnetic materials. The technique works based on capillary action, which is the tendency of a liquid to rise, or saturate. The types of defects that can be found using liquid penetrant testing include, but are but not limited to: cracks, porosity, undercut, overlap fatigue cracks, and hairline cracks.

The two most commonly used penetrant testing techniques are the visible method and the fluorescent method. The visible method relies on a penetrant dye that is usually bright red in color, and can be seen with the naked eye. The fluorescent method uses a penetrant dye that cannot be seen by the naked eye and requires the use of ultraviolet light to enhance the indications. That being said, the fluorescent method tends to be more sensitive and can reveal smaller defects.




Radiography is a type of nondestructive examination technique that uses radiation (either x-rays or gamma rays) to inspect various types of equipment. It sees extensive use in industrial facilities. Radiography works by using a device to emit radiation at a piece of equipment. Some of the radiation passes through the equipment and is captured on the other side. This creates an image that can show signs of possible flaws or damage in the equipment.

There are two main kinds of radiography: conventional radiography and digital radiography.