Nortech Advanced NDT

Also referred to as Magnetic Particle Inspection, this method is for the detection of surface and sub-surface defects in ferrous materials. They make use of an externally applied magnetic field or electric current through the material, and the principle that the magnetic flux will leave the part at the area of the flaw. As it does not require a high-degree of surface preparation, performing magnetic particle inspection is relatively fast and simple. This has resulted in MPI becoming one of the more commonly utilized NDT techniques.

The presence of a surface or near surface flaw (void) in the material causes distortion in the magnetic flux through it, which in turn causes leakage of the magnetic fields at the flaw. This deformation of the magnetic field is not limited to the immediate locality of the defect but extends for a considerable distance; even through the surface and into the air if the magnetism is intense enough. Thus, the size of the distortion is much larger than that of the defect and is made visible at the surface of the part by means of the tiny particles that are attracted to the leakage fields.

The method can be applied to any metals which can be strongly magnetized such as irons and ferritic steels - though typically not applicable to austenitic steels.

HOW MPI IS CARRIED OUT

There are two primary variations of the process - Dry Magnetic Particle Testing  and Wet Magnetic Particle Testing.  In either case, the process is initiated by running a magnetic current through the part. If there are any cracks or defects, this will interrupt the magnetic flow of current and will cause spreading. A resulting “flux leakage field” will form at the site of the damage.

The next step involves spreading metal particles over the part. If there are any flaws on or near the surface, the flux leakage field will attach particles to the area of damage. This step allows for a visible indication of the approximate dimension of the damage.

ADVANTAGES OF MPI

There are a number of benefits of employing MPI compared to other non-destructive testing methods. For one, it is easily transportable, relatively inexpensive, and does not possess any intensive pre-cleaning requirements. Additionally, MPI is ideal for detecting minuscule, shallow surface cracks and it will quickly permeate through thin coatings. Lastly, it can be applied to wide range of test material of various shape and dimension.

Guided wave examination (GWUT), also referred to as Guided Wave Testing (GWUT), has become a standard NDT method for inspecting pipework. The method allows for volumetric examination of piping systems whether the line is insulated, buried, as cased road or railway crossings, high line, river or bridge crossings, or configured as offshore pipeline risers without having to access the entire piping system. Usually, guided wave ultrasonic testing is well-suited for inspecting long sections of pipework. GWUT is a screening tool which detects cross sectional changes in the wall thickness of the system being examined. Data is typically analyzed on site to determine if complimentary inspections are required.

GWUT will detect the following:

• internal & external corrosion
• internal & external cracking
• corrosion under supports/clamps
• corrosion under insulation
• erosion in elbows
• soil air interface corrosion
• girth welds, attachments & clamps

PERFORMING A GUIDED WAVE EXAMINATION

A removable transducer ring is wrapped around the circumference of the pipe that can be located at a distance from the target inspection area. Force is then applied to the transducer to acquire a solid coupling. Signals are generated and then received by advanced computer hardware. The resulting data can be interpreted by a trained inspector.

ULTRAWAVE LRT SYSTEM

Nortech Advanced NDT uses the UltraWave LRT system which uses uses low-frequency ultrasonic waves to scan pipe from 2” to 60” in diameter with ranges up to 300’ on either side of the GWUT collar. We are able to locate areas of concern without having to access the entire system. Ultrawave LRT is ideal to screen pipes and pipelines that are in current service, as well as inspect difficult to access pipes from a single inspection point. 

Examination can be performed on in-service systems with full volumetric examination of the pipe. Ultrawave LRT is capable of detecting variance in wall thickness and providing critical information regarding the circumferential extent through focusing. The UltraWave LRT system is able to give a precise location for further inspection based on initial signal response as well advanced synthetic focusing algorithms & active focusing. Minimal time & space is required to set up the system.


Various factors impact the distance in which inspection can be carried out. These include pipe configuration, soil conditions, environment, fluid inside of the line as well as the coating used.