Debasis HIC test evalaution according to NACE TM 0284 -2003 : Evaluation of Pipeline and Pressure Vessel Steels for resistance to HIC, test procedure, test conditions - pH 3( Solution A) or pH 5 (Solution B), dimensions and preparation of test specimens, duration. metallographic evaluation and acceptance criteria have to be agreed between purchaser and supplier - so far as manufactured steel to meet HIC tests. CLR, CTR & CSR values can be either as average of all sections examined or single values out of one section examined. For In-service inspection to detect HIC, EEMUA (Engineering Equipment Material Users' Association) guideline TP -179 is not to accept any defect ( i.e., "Nil" defect at the inner wall) at the inner wall as it is considered that any small defect can hide presence of large sub-surface defect and can lead to erroneous intepretation by NDE operators. Commonly suggested NDE approach for HIC: WFMPT of all inner wall ( if accessibility is not a limitation), MPT of external wall / nozzle re-inforcements, column support welds etc, UT Flaw check, RT - 20% for pipeline welds, Acoustic emission (some users prefer AET). Each NDE approach has its own advantages and dis advantages - depending on the system being examined and the levels of results expected. Some users prefer advanced NDE approach like TOFD, AET, laser difffraction for HIC detection depending on the reliability, reproducibility and interpretation of results. On your question of UTFD - a prior setting of calibration with +6 dB for attenuation loss - from surface roughness, and to detect micro-voids caused by hydrogen (in wet sour) can result in absorbption of ultrasonic energy ( indirectly attenuation loss in UTFD) is the most practical way of doing UTFD. However, fine cracks of HIC - possibly hidden by attachments and "where and what to look" can lead to mis-interpretation in UTFD. This needs special calibrated test procedure and sample for UTFD of the same material + a very experienced UT operator who has knowledge on metallurgical and corrosion mechanism of HIC ( sample for UTFD calibration should have near matching chemical composition and mechanical properties from eavaluting and acceptance criteria of fine cracks of HIC). The user has to judge the criticality level versus crack ratios and also the probability level Risk matrix while using any of the NDE approaches for in-service inspection of pipe line or pressure vessel steel shells or attachments from evaluating HIC and the criticality acceptance criteria. Trust this will be of some help to you C.V.Srinivasan Nishi Engineers Pvt Ltd India Augus 12, 2007 E-mail: nishi@vsnl.com >NACE TM-02-77 gives a method to evaluate HIC tolerance >w.r.t. CLR, CTR & CSR. Normally at pH 3 solution a CLR of >minimu 15% is considered acceptable. Under significantly >severe condition CLR 5% is taken as base line. > >I am not having much hands-on idea about the practical field >evaluation of CLR values . I would like to know from forum >expertise that whether "a" values in evaluating CLR can be >done by conventional UT 6db drop method or is thee any other >method recommended like TOFD etc. for this purpose. > >A discussion/ experience/education share please. >regards