The use of carbon steel pipelines lined or clad with corrosion resistant alloys (CRAs) is increasing in the oil and gas (O&G) industry. These pipelines combine the mechanical properties of carbon steel with the corrosion resistance of CRAs. Some CRAs such as AISI 316L (UNS 31603) are not pre-qualified according to ANSI/NACE MR0175/ISO 15156 part 3. A note in table A.2 of the standard specifies that AISI 316L (UNS 31603) "shall be free from cold work caused by shaping, forming, cold reducing, tension, expansion, etc. after the final solution annealing and quenching treatment". During installation in the reeling process, these pipes are subjected to cold deformation caused by cycles of compression and tension. Therefore, UNS 31603 liner or clad material must be qualified according to ISO 15156-3. These pipes are additionally welded with girth and longitudinal welds. This paper presents an approach to simulate the effect of the reeling process (cold deformation) during the qualification of UNS 31603 lined and clad pipes. This approach is in line with DNV ST-F101 which refers to DNV RP-F108. Throughout this paper, the methodology is described and the learnings are discussed.
The use of carbon steel pipelines lined or clad with corrosion resistant alloys (CRAs) is increasing in the O&G industry. These pipelines combine the mechanical properties of carbon steel with the corrosion resistance of CRAs. Some CRAs such as AISI 316L (UNS 31603) are not pre-qualified according to ANSI/NACE MR0175/ISO 15156 part 3. The potential for corrosion and cracking of carbon steel in some applications can require a CRA liner/clad layer to resist corrosion but this can introduce the possible risk of stress corrosion cracking of some CRAs.
Stress corrosion cracking (SCC) is caused by the synergetic effect of corrosion and applied stress.1 Stress or pre-strain plays an important role in SCC. The anodic dissolution is facilitated by the enhanced electrochemical activity of metals under stress.2 Applied stress over 80% of the yield strength significantly increases the electrochemical activity of the material, promoting anodic dissolution and SCC. This level of stress can cause stress concentration in presence of surface defects, such as cracks or pits. Therefore, the local anodic dissolution in the defect area is enhanced.3 Furthermore, this stress increases the hydrogen absorption, diffusion and penetration in the defect area, leading to crack tip propagation.4 Carbon steel pipelines lined or clad with AISI 316L (UNS 31603) are commonly employed in the the O&G industry due to the combination of mechanical and corrosion resistant properties.5
