Sunday Nov 18 2018

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Introduction Of NDT Technology

Infrared Thermography

What is it?

Infrared thermography is a science of using infrared technology to detect radiation emitted from an object and convert the radiation energy into temperature reading, then the object image is reproduced into temperature distribution diagram, which called thermagrams.

Infrared thermal imaging device provide the ability to "see" heat radiated from the equipment.  In black-and-white thermograms (pictures of heat), white is hot and black is cold unless stated otherwise.  If the thermograms are in color, usually the white and light red areas are hotter and black and Blue areas are colder.

Infrared science was discovered by a British astronomer, Herschel, in 1800. When dispersing sunlight using a prism, Herschel accidentally found that there was an invisible light on the outside of red light when increases the temperature of an object.

source from:  R.D.Hudson, Jr. "INFRARED SYSTEM ENGINEERING" (John Wiley & Son, 1969)

How does it works?

Infrared thermography inspection should be conducted by certified infrared thermographer using an infrared thermal imaging device.

The thermographer will perform infrared thermography inspection on the related equipment and captures the equipment image in the form of thermal distribution diagram – thermagrams, for further qualitative and quantitative analysis.

Infrared thermography able to locate and measure the exceptional temperature of equipment.  Overheating can cause premature deterioration and costly unplanned failure of your equipment.  With the advance notice, you can pro-actively service this equipment before it creates costly problems.

Maintenance personnel need to prioritize their repair efforts.  So we provide you with a Repair Priority Rating for each exception identified in this report.  This Repair Priority Rating comes from subjective and /or objective ratings.

Subjective Ratings are determined by the owner’s qualified assistant or representative who considers how important the potential problem is to the safe and profitable operation of the system.

When the thermographer provides a quantitative infrared inspection (takes temperatures), the Temperature Severity Ratings should refer to the industrial standard / specification of the related equipment / system, as well as, the application condition of the equipment inspected.

While these repair ratings will help you prioritize your maintenance efforts, you must understand that the failure curves of many electrical and mechanical components are not linear and predictable. Therefore, you should investigate and repair all reported exceptions as soon as possible.  And once repaired, each should be re-inspected i.e. post scan to assure that its temperature is normal and that the potential problem has been corrected. Note that for every problem always inspect for physical damage to determine repair or replacement of the particular component identified.

There are no rules for the assessment of excess temperatures, which are measured on indirectly overheated surfaces. Indirect overheating can be caused by hidden faults, e.g. cracks inside a breaker where the temperature is measured from the outside.

Experience shows that oil insulated transformers and breakers with internal faults where an approximately temperature increase of 10% has been measured on the surface are considerably hotter inside. Very often the faulty parts are severely burnt.


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