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PRCI Report 191
- Environmental Sensitive Cracking (Low pH SCC) of Hi-Pressure Pipelines
- Report / Survey by Pipeline Research Council International, 08/01/1990
- Publisher: PRCI
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L51623e
Battelle Memorial Institute
Need: A review of the "Field Failure Investigations" files indicates that four modes of environment sensitive failure of pipelines are recognized. These are: - Fatigue or corrosion fatigue - usually associated with cyclic loading during the shipping of joints; - Hydrogen-related cracking -mostly associated with the existence of hard spots in the pipe; - Intergranular stress corrosion cracking - due to the generation of a relatively high pH (9-10), somewhat concentrated, carbonate-bicarbonate solution; and - Transgranular stress corrosion cracking - due to the presence of a relatively low pH (6-7), dilute aqueous environment.
Benefit: This is a review of the current situation relating to transgranular environment sensitive cracking of the type experienced on TransCanada Pipelines, by comparison with the commoner intergranular cracking experienced on many systems. It is probable that the cracking experience by TransCanada is not unique. Quite apart from the crack paths, there are other significant differences between the conditions in which the two types of cracking occur, particularly in relation to the environments involved, and sufficiently so to indicate that the mechanisms of cracking are different. The circumstances in which the two types of environment form are discussed. If the creation of a reliable model for practical application to transgranular cracking is to be achieved, there is need for data relating to the effects of stressing conditions upon the crack nucleation and growth rates of such cracks and of the circumstances in which these cracks coalesce.
Result: It is probable that the transgranular stress corrosion cracking experience in pipelines of the TCPL system has been experienced on some other lines. Although there are some similarities in the characteristics of cracking by carbonate-bicarbonate solution and those thought to be responsible for cracking on the TCPL lines, the differences are so significant that it must be doubtful that these different instances of cracking have the same origins. While it is possible to speculate on the circumstances in which the two types of environment form, there is a need for better understanding of those circumstances if better predictability of their occurrence is to be achieved. If the modeling of cracking by low pH solutions in a form suitable for practical application is to be achieved, there is a pressing need for data relating to the effects of stressing conditions upon cracking by such environments, including information on crack nucleation and growth rates and the distribution of cracks that result in crack coalescence.
Battelle Memorial Institute
Need: A review of the "Field Failure Investigations" files indicates that four modes of environment sensitive failure of pipelines are recognized. These are: - Fatigue or corrosion fatigue - usually associated with cyclic loading during the shipping of joints; - Hydrogen-related cracking -mostly associated with the existence of hard spots in the pipe; - Intergranular stress corrosion cracking - due to the generation of a relatively high pH (9-10), somewhat concentrated, carbonate-bicarbonate solution; and - Transgranular stress corrosion cracking - due to the presence of a relatively low pH (6-7), dilute aqueous environment.
Benefit: This is a review of the current situation relating to transgranular environment sensitive cracking of the type experienced on TransCanada Pipelines, by comparison with the commoner intergranular cracking experienced on many systems. It is probable that the cracking experience by TransCanada is not unique. Quite apart from the crack paths, there are other significant differences between the conditions in which the two types of cracking occur, particularly in relation to the environments involved, and sufficiently so to indicate that the mechanisms of cracking are different. The circumstances in which the two types of environment form are discussed. If the creation of a reliable model for practical application to transgranular cracking is to be achieved, there is need for data relating to the effects of stressing conditions upon the crack nucleation and growth rates of such cracks and of the circumstances in which these cracks coalesce.
Result: It is probable that the transgranular stress corrosion cracking experience in pipelines of the TCPL system has been experienced on some other lines. Although there are some similarities in the characteristics of cracking by carbonate-bicarbonate solution and those thought to be responsible for cracking on the TCPL lines, the differences are so significant that it must be doubtful that these different instances of cracking have the same origins. While it is possible to speculate on the circumstances in which the two types of environment form, there is a need for better understanding of those circumstances if better predictability of their occurrence is to be achieved. If the modeling of cracking by low pH solutions in a form suitable for practical application is to be achieved, there is a pressing need for data relating to the effects of stressing conditions upon cracking by such environments, including information on crack nucleation and growth rates and the distribution of cracks that result in crack coalescence.
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