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New Axially Loaded Full Ring Test Method for Assessment of Susceptibility of Girth Welds and Parent Pipe to Sour Service Cracking

New axially loaded full ring test method which was developed and demonstrated to combine the benefits of retaining a full as-welded pipe pup-piece, permitting single-sided exposure, with the advantage of tensile loading of the complete tubular specimen.

Product Number: 51317--8965-SG
ISBN: 8965 2017 CP
Author: Philip Dent
Publication Date: 2017
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Susceptibility to cracking in sour service is usually determined by testing in laboratory or simulated service environments in compliance with NACE MR0175 / ISO15156. Typically small scale specimens are extracted from sampled material to facilitate uniaxial tensile C-ring or 4-point bend testing to determine resistance to Sulphide Stress Cracking (SSC) or Stress Corrosion Cracking (SCC). Sampling relaxes residual stress and in many cases the specimen is not representative of the material surface condition and microstructure and clearly may not represent material with inhomogeneous properties. This is particularly true for subsea lines installed by reeling as strain history varies around the entire circumference. A full ring test method was developed in the 1980s/1990s which is better able to assess behaviour with hoop stress and is still favoured today (BS 8701) but it does not load the entire specimen. This paper describes a new axially loaded full ring test method which was developed and demonstrated to combine the benefits of retaining a full as-welded pipe pup-piece permitting single-sided exposure with the advantage of tensile loading of the complete tubular specimen.

Key words: Full ring, sulfide stress cracking, SSC, stress-orientated hydrogen-induced cracking ,SOHIC, stress corrosion cracking, SCC, OTI 95 635, BS 8701, sour service, test method, welded pipe, residual stress, reeled pipe, hydrogen-induced cracking, HIC, soft-zone cracking, SZC, fitness-for-purpose.

Susceptibility to cracking in sour service is usually determined by testing in laboratory or simulated service environments in compliance with NACE MR0175 / ISO15156. Typically small scale specimens are extracted from sampled material to facilitate uniaxial tensile C-ring or 4-point bend testing to determine resistance to Sulphide Stress Cracking (SSC) or Stress Corrosion Cracking (SCC). Sampling relaxes residual stress and in many cases the specimen is not representative of the material surface condition and microstructure and clearly may not represent material with inhomogeneous properties. This is particularly true for subsea lines installed by reeling as strain history varies around the entire circumference. A full ring test method was developed in the 1980s/1990s which is better able to assess behaviour with hoop stress and is still favoured today (BS 8701) but it does not load the entire specimen. This paper describes a new axially loaded full ring test method which was developed and demonstrated to combine the benefits of retaining a full as-welded pipe pup-piece permitting single-sided exposure with the advantage of tensile loading of the complete tubular specimen.

Key words: Full ring, sulfide stress cracking, SSC, stress-orientated hydrogen-induced cracking ,SOHIC, stress corrosion cracking, SCC, OTI 95 635, BS 8701, sour service, test method, welded pipe, residual stress, reeled pipe, hydrogen-induced cracking, HIC, soft-zone cracking, SZC, fitness-for-purpose.

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