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Non-Destructive Testing


In short, non-destructive testing is an inspection, that once completed, does absolutely NO damage to the equipment or object. Also referred to as NDT. This is merely an overview of types of tests. Tests that are normally done when the equipment or material is new. Please refer to the sections that we gave more attention to in the Analysis section of the Industrial portion of this site. The analysis section is more of a common maintenance section.
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Maintenance is normally analyzed and recorded. We tried to this as separate and logically as possible, however, there are a few tests that we left here in testing, but went into broader detail for a better explanation of procedures and practices in the analysis section.



Thermography (IR Infrared) Ultrasonic Magnetic Particle Inspection (MPI) X-Ray (Radiographic) Liquid Dye Penetrant Eddy Current Magnetic Flux Leakage Vibration Analysis


Thermography (IR Infrared)
Infrared (IR) thermography is a technology widely used in non-destructive testing of industrial equipment. Depending on the unit you purchase, it will produce images that help distinguish problematic areas in materials and/or equipment.

IR cameras that have full radiometric capability detect the IR emissions from the equipment or material and provides feedback in the form of images. They can also give a temperature reading of an area selected so you can gather maintenance information for your records.



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Ultrasonic
This type of testing uses electrically generated sound waves to pass through objects to show the operator the potential defects. The obvious benefit to this type is that it can be open access, or an enclosed area. Corona, tracking, or arcing disturbs the surrounding air molecules. The probe picks up on these high frequency sounds and converts them, via heterodyning, into audible ranges.



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Magnetic Particle Inspection (MPI)
This type of test uses magnetic fields and particles to detect flaws in a ferromagnetic material; such as iron, cobalt, nickel; any material that can be magnetized in order to be properly inspected. Typically, these are done with yokes, prods, coils, heads, or a central conductor. What they all have in common is electricity is passed through them generating a magnetic field.

This is used extensively in shipbuilding, aerospace, power generation, structural steel industries, etc.




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X-Ray (Radiographic)
This type of test is an electrically generated x-ray or a gamma-ray from a radiation source. This radiation passes through the object and is recorded on film. This test is widely used to prove crucial welds.

There is also digital radiography which does not use film as the medium, but a digital file that can be viewed on a monitor and can easily be transferred electronically.



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Liquid Dye Penetrant
This type of test can only detect surface issues. It is by far the most popular method of non-destructive testing because it takes minimal training and it is an inexpensive test. This can be used on ferrous, and non-ferrous materials. As a penetrating dye is applied to the surface area to be tested, left on long enough to absorb, but not to dry. Then a developer is used, and the defects can be seen by the inspector.



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Eddy Current
Eddy current tests send an induced current through a conductive probe, at a certain frequency, that when placed near a conductive material that is being tested by means of magnetic coupling, and can magnify disturbances in eddy current circulation. These disturbances are flaws and will be read by measuring the variations in coil impedance. There is surface and tubing inspections.

It can very quickly inspect large areas finding cracks, metal hardness, and coating thicknesses. It will NOT work on plastic or other non conductive materials. Eddy current  is well utilized as a “team” with ultrasonic testing, one as a surface and ultrasonic as a deep penetration.



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Magnetic Flux Leakage

Magnetic Flux leakage uses a magnet to magnetize the conductive material. In between the poles of the magnet, a detector is used to identify leakage in the field. This leakage is accumulated on a chart recording to reveal damaged areas at different depths.

Magnetic Flux leakage is used as a “team” with eddy current sensors to progress the distinction between the defects that are external and internal.


The following is a picture of a tank floor scanning detector. This type of test is specific to large areas that either need to prove degredation or manufacturing flaws.




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Vibration Analysis

(This portion of vibration analysis is for testing only, or commissioning of a manufactured piece or product. For a more in-depth explanation of the maintenance procedures please refer to the Analysis section of the Industrial portion of this site.)

Sometimes it is necessary to load a motor on a pallet and have it tested or analyized for warranty investigations such as failure analysis. If common problems, such as loose bolts, presence of soft foot, or incorrect alignment at commissioning stage are happening, premature failure can easily be avoided by minor alignments to proper specifications and tightening gear.

Vibration is a mechanical condition that can be helpful, or bad for the equipment. For example, a loudspeaker is an example of helpful vibrations, and vibrations due to a misaligned motor can be very destructive.

Testing tolerances at commissioning stage is extremely important to equipment health.  The equipment used in proving these “tolerances” are normally, transducers, vibration meters for maintenance rounds, diagnostic vibration tester, or vibration lasers.