NDT for In-service Inspection

Dan kami telah menciptakan besi dengan keadaannya mengandungi kekuatan yang handal serta berbagai faedah lagi bagi manusia dan supaya ternyata pengetahuan Allah tentang orang yang menegak dan mempertahankan agama Allah serta menolong Rasul-Rasul-Nya, padahal balasan baiknya tidak kelihatan (kepadanya); sesungguhnya Allah Maha Kuat, lagi Maha Kuasa. [al-Hadid 25].

and We sent down Iron, in which is (material for) mighty war, as well as many benefits for mankind, that Allah may test who it is that will help, unseen, Him and His Messengers: for Allah is Full of Strength, Exalted in Might (and able to enforce His Will).

Items to be addressed in ISI program

n  Objective, scope and periodicity;

n  Organization and responsibilities;

n  Establishment of a baseline;

n  Establishment of an examination schedule;

n  Specification of methods and techniques to be applied;

n  Qualification of procedures and equipment;

n  Training and qualification of personnel; and

n  Quality assurance considerations

Service Induced Discontinuities

n  Corrosion, Erosion

n  intergranular attack stress corrosion cracking

n  corrosion fatigue

n  Cracks

n  mechanical fatigue

n  thermal fatigue

n  Hydrogen embrittlement

n  Over-stressing

n  Lamellar Tearing

n  Creep rupture

NDT techniques

n  Ultrasonic testing – thickness, crack

n  Magnetic particle testing – crack in ferromagnetic mat’l

n  Penetrant testing – crcak in non ferromagnetic mat’l

n  Eddy current /UT/boroscope for tube inspection

n  Thermography – hot spot

n  Radiography testing - thickness

Advantages of MT and PT

n  Excellent sensitivity to surface discontinuities

n  Good non-fluorescent MT/PT can detect discontinuities of up to 0.5 μm width and 20 μm depth.

n  Good fluorescent MT/PT can detect discontinuities of 0.2 - 0.5 μm width and 5 - 8 μm depth

n  Eddy current testing  ~ 30 μm and Ultrasonic testing 100 μm depth (best condition)

n  The indications appear directly on the test surface

n  Simple method - do not require highly trained personnel

n  Results can be photographed and permanent records can be made

Advanced or special UT

n  Long Range UT for pipeline inspection

n  IRIS – tube inspection (being replaced by eddy current/RFET)

n  C-scan for corrosion mapping

n  TOFD for weld inspection - good for body and root defect but not for surface

n  Phase array - probes are expensive

n  EMAT- for low and high temperature application

Precautions for MT, PT, UT

n  UT couplants, PT & MT materials used on nickel base alloys shall not contain more than 250 ppm of sulfur.

n  UT couplants, PT & MT materials used on austenitic stainless steel or titanium shall not contain more than 250 ppm of halides (chlorides plus fluorides).

Effective NDT

n  trained and qualified personnel – trainer and examiner are independent (ISO17024/ISO9712)

n  Equipment -suitable for intended purpose and calibrated in accordance with a defined program. Calibration traceable to national/international standards

n  procedure for conducting test – should be agreed between inspector and client  (ISO17020/ ASME)

n  system for reporting results (follow minimum content stated in ISO17020/ASME)

n  standard to interpret results: ASME, API, AWS

References

n  ISO 17024: General Requirements for Bodies operating Certification of Persons, 2003

n  ISO 17020: General Criteria for the Operation of Various Types of Bodies Performing Inspection, 1998

n  ISO 9712: NDT – qualification and certification of personnel, 2005

n  ASME V: Article 4 and 5, 2001

n  IAEA-TECDOC-1263: Application of non-destructive testing and in-service inspection to research reactors, 2001

n   Radiography training notes for level 3, IAEA, Feb 1991.

n  Ultrasonic training notes for level 3, IAEA, Mac 1989.

n  Spoerer, Penetrant & Magnetic Particle training notes, 1999

n  http://www.ndt.net