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Karl Marks, Acuren
Inspection, Inc.
In the Chemical and Petroleum industries, heat exchangers are critical
components in processing operation.
The tubing in heat exchangers is subjected to process chemistry on
both sides. Or, to be more accurate,
on one side they are subjected to process chemistry’s and the other water,
steam air, and even process. The
chemical fluid and heat transfer conditions, contribute to the accelerated
corrosion of tube materials such as erosion, corrosion, thinning, pitting,
cracking, or vibration and/or combinations of the aforementioned
conditions. Most exchangers get overlooked
when it comes time for inspection and so they get cleaned, visually inspected
and hydrostatically tested for leaks usually only during outage periods. While this may be satisfactory for some
equipment owners, it is imperative that these components be examined
periodically and that their integrity is maintained by using NDE techniques which have been proven reliable. The NDE
techniques required for proper maintenance are regularly used to inspect all
conditions since the people responsible for performing the inspection
generally have one or two techniques available. The techniques which are most common and
currently being used in the industry include, but are not limited to Eddy
Current (ET), Remote Field Testing (RFT), External
Reference Remote Field/Near Field Testing (X-RFT/NFT),
and International Rotating Inspection System-Ultrasonic (IRIS). With many materials in use for tubing,
there is not (at the present time) one nondestructive test application that
can be used on every material.
Choosing the correct inspection technique depends on a number of
factors including the size and material of the tubes to be inspected, the
service history and the failure mechanism anticipated. Therefore, in this paper, four of the most
common tubing inspection applications will be discussed, as well as the
theory and practical use of each application, along with the advantages and
disadvantages associated with each test.
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