Pressfit bushings, tapered bolts and severe metal forming are examples of high residual tensile stresses which can lead to stress cracking. The author explains how and why pipelines fall prey to stress corrosion cracking and then offers tested and proven strategies for preventing, detecting, and monitoring it in order to prevent pipeline failure. Stress corrosion cracking in pipelines begins when small cracks develop on the external surface of buried pipelines. Stress corrosion cracking of pipelines y frank cheng bok. According to the electrochemical theory, this requires a condition along grain boundaries that makes them anodic to the rest of the microstructure so that corrosion propagates selectively along them. Scc results from the formation of cracks due to various factors in combination with the environment surrounding the pipeline that together. When they fail due to stress corrosion cracking, they can wreak environmental havoc. Stress corrosion cracking can be a serious threat to the integrity of natural gas and petroleum pipelines. Stress corrosion cracking scc is the growth of crack formation in a corrosive environment. Integrity managements of pipelines subject to stress. Visualisation of the galvanic effects at welds on carbon steel. Stress corrosion cracking scc is cracking induced by the combined influence of tensile stress and corrosive environments.
Cheng is an internationally recognized authority in corrosion science and engineering in oilgas and pipeline systems. Effect of stress on corrosion at crack tip on pipeline steel in a nearneutral ph. As its name suggests, scc takes the form of a network of cracks that eventually will lead to sudden, catastrophic failure in your tanks. Stakeholder communications stress corrosion fact sheet. We have completed the public inquiry into stress corrosion cracking on canadian oil and gas pipelines in accordance with the boards terms of reference of 6 september 1995. Science and engineering of pipeline stress corrosion cracking. Jun 23, 2015 weixing chen pipeline operation strategies for mitigating the risk of failures caused by stress corrosion cracking and corrosion fatigue. There is also a longstanding debate on the naming of corrosion, which includes a variety of more specific type with names such as sulfide stress corrosion cracking. Starting with the first recognized stress corrosion cracking failure in 1965, the intergranular form of cracking also known as highph scc was investigated to identify the causative agent and the controlling metallurgical, environmental, and stress related factors. Our recent studies have shown that an important factor of main pipelines serviceability loss under their longterm service is the inbulk metal degradation of the pipe. Scc can affect materials in a number of ways, from dry cracking to catastrophic failure. An enormous amount of failures have been attributed to stress corrosion cracking over the last century. Failures due to stresscorrosion cracking scc generally involve several adjacent, parallel, deep cracks that because of their proximity coalesce to form long flaws, which can cause ruptures. Frank chengs research works the university of calgary.
Stress corrosion cracking examples a fracture of the screwed side of a dshackle. The test may not be relevant to stresscorrosion cracking. These cracks are not visible initially, but as time passes, these individual cracks may grow and forms colonies, and many of them join together to form longer cracks. In many cases, problems with stress corrosion cracking scc can be solved by selecting a suitable material. Failures due to stress corrosion cracking scc generally involve several adjacent, parallel, deep cracks that because of their proximity coalesce to form long flaws, which can cause ruptures. Stress corrosion cracking in the necessary condition is to have tensile strength. The original 1997 cepa stress corrosion cracking recommended practices hereafter referred to as the practices were prepared and made public by cepa in response to a the national energy board of canadas public inquiry mh295 into the problem of stress corrosion cracking scc in oil and gas pipelines. Stress corrosion cracking of pipelines cern document server. Stress on aircraft parts may be residual within the part as a result of the production process or externally applied cyclic loading. The great majority of those failures have involved intergranular cracking, but more recently instances of transgranular cracking have been observed.
No matter how well these pipelines are designed, constructed and protected, once in place they are subjected to environmental abuse, external damage, coating disbondments, inherent mill. Recent studies indicate that such multiple flaws cause a local increase in compliance as compared to a single crack that represents the largest of the cracks involved. Identifying stress corrosion cracking is a challenge because the worst damage usually happens below the surface where it remains unseen. Materials that normally provide acceptable resistance in hot chloride service may crack in this test. Stresses that cause environmental cracking arise from residual cold work, welding, grinding, thermal. Nace publication 351032003sg, external stress corrosion cracking of underground pipelines available for download stress corrosion cracking scc for engineers, designers and consultants involved in the design, maintenance, and rehabilitation of underground petroleum including gas, crude oil, and refinery products pipelines.
Stress corrosion cracking in aluminum alloys is characteristically intergranular. He is an internationally recognized authority in corrosion science and engineering of pipelines. Frank cheng, phd, is professor and canada research chair in pipeline engineering at the university of calgary. A cyclical load is critical for crack initiation and growth. National academy of sciences committee for pipeline transportation of diluted bitumen. If you have insulated solid stainless steel equipment operating in the cui temperature range you are likely to eventually experience external chloride stress corrosion cracking ecscc. Stress corrosion cracking of pipelines wiley series in. L51803 failure criterion for stresscorrosion cracking in. Sep 15, 2014 stress corrosion cracking of gas pipelines 3 minute 2014 thesis finalist university of adelaide. There is a free corrosion condition below the coating that results in an environment with a ph around 5 to 7. Nace publication 351032003sg, external stress corrosion. Frank cheng, stress corrosion cracking of pipelines, john wiley, hoboken, nj, 20. What causes stress corrosion cracking in pipelines.
The stress corrosion cracking of the steel was dominated by an anodic dissolution mechanism, while the effect of hydrogen was negligible. Cheng is the author of two books stress corrosion cracking of pipelines. The deposit of corrosion products at the crack tip could protect somewhat from further corrosion. This book skillfully explains the fundamental science and. Frank cheng, phd, is professor and canada research chair in pipeline engineering at the. Stress corrosion cracking of pipelines researchgate. There are field data that indicate that with a decreasing stress ratio there is an increased propensity for cracking. The combined effects of stress and corrosion can cause a special type of failure known as stress corrosion cracking scc. Stress corrosion cracking scc is a type of environmentallyassisted cracking eac, or the formation of cracks caused by various factors combined with the environment surrounding the pipeline. These differences reflect the different passivity of the steel in the environments involved with the two forms of cracking. Corrosion is related to the susceptibility of the material to the environment, while stresses may be residual, external or.
Structural failure due to scc can be very unpredictablefailure could occur after as little as a few hours of exposure, or the equipment could continue to function normally for. Frank cheng schulich school of engineering university of calgary. Stress corrosion cracking of pipelines wiley online books. Mar 15, 20 explains why pipeline stress corrosion cracking happens and how it can be prevented pipelines sit at the heart of the global economy. Aluminum alloys that contain appreciable amounts of soluble alloying elements, primarily copper, magnesium, silicon, and zinc, are susceptible to stresscorrosion cracking scc.
Cheng has published over 115 journal articles dedicated to corrosion, pipeline engineering, and materials science. The risk of stress corrosion cracking scc can be minimized through plant and equipment design. Standard practice for evaluating stresscorrosioncracking. It is generally not well understood, and can, given the right conditions, cause catastrophic failure. Stress corrosion cracking of brittle fracture surface, but it may also occur in high toughness materials. Frank chengs 196 research works with 5191 citations and 10966 reads. Scc is a form of corrosion that occurs in nearly all alloys, including the grades of stainless steel commonly used in brewery equipment types 304, 304l, 316, and 316l. Chloride cracking of austenitic stainless steels 300 series ss is an offshoot of cui, and theres nothing really magical about it.
This is a typical location for residual stress, where metal deformation in construction of the shackle is at a maximum. Stress corrosion cracking of pipelines begins with a brief introduction and then explores general principals of stress corrosion cracking, including two detailed case studies of pipeline failure. Scc is highly chemically specific in that certain alloys are likely to undergo scc only when exposed to a small number of chemical environments. Stress corrosion cracking scc is a fracture process that involves the combined and simultaneous action of a tensile stress and a corrosive environment. Abstract the carbon steel casings of heat recovery steam generators hrsgs in a cogeneration plant were found to have developed cracks that originated on the inside surfaces.
Analysis of electrochemical hydrogen permeation through x65 pipeline steel and its implications on pipeline stress corrosion cracking. Frank cheng schulich school of engineering university. The following notes are for general guidance only and are based on crps knowledge and experience. When they are in good working order, they deliver fuel to meet the evergrowing demand for energy around the world. Stresscorrosion cracking, materials performance and. Stress corrosion cracking scc is a phenomenon experienced from time to time in stainless steels. What is stress corrosion cracking and why does it occur. Frank cheng, 9781118022672, available at book depository with free delivery worldwide. Stress corrosion cracking of gas pipelines 3 minute 2014 thesis finalist university of adelaide. Stress corrosion cracking of pipelines book chemistryviews. Stress corrosion cracking scc stress corrosion cracking is to bear the stress of the alloy in the corrosive environment because of strong expansion of the alternate failure pattern of a generic term.
It is the least for the short transverse direction. The resistance of metals to stress corrosion cracking is always less when tension is applied in a transverse direction. Feb 22, 2001 stress corrosion cracking scc defined. The sides of intergranular stress corrosion cracks show little evidence of lateral corrosion, whereas transgranular cracks are characterized by appreciable lateral corrosion of the crack walls, as is apparent from fig. Explains why pipeline stress corrosion cracking happens and how it can be prevented pipelines sit at the heart of the global economy. Stress corrosion cracking scc is a progressive fracturing that occurs in metals as a result of the combined influence of tensile stress and a corrosive environment. For the susceptibility to stress corrosion cracking, the directional variation can be appreciable and must be considered in the design of the fabricated hardware. Pdf stress corrosion cracking of pipelines alexander.
Stress corrosion cracking industrial metallurgists. Frank cheng, richard norsworthy, pipeline coatings, nace. Environmental cracking refers to a corrosion cracking caused by a combination of conditions that can specifically result in one of the following form of corrosion damage. Your tanks are the core of your brewery, so it is important to understand what scc is, what causes it, and what to do when your tanks suffer from this type of damage. It can lead to unexpected sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. Stress corrosion cracking of gas pipelines 3 minute 2014. Stress corrosion cracking in a brewery paul mueller company. Mar 15, 20 stress corrosion cracking of pipelines by y.
There is also a longstanding debate on the naming of corrosion, which includes a variety of more specific type with names such as sulfide stress corrosion cracking, hydrogenassisted stress corrosion cracking. Stress corrosion cracking of pipelines wiley series in corrosion kindle edition by cheng, y. Scc occurs when the tensile stress and a specific environment are able to cause failure by their combined action, but are insufficient to cause failure by either one acting alone. Stress corrosion cracking scc of pipelines, from the soil side, was first recognised over three decades ago j and has now been experienced in several countries throughout the world.
The hrsgs receive hot exhaust gases from the primary gas turbines gts. We are now pleased to make our report to the board pursuant to section 15 of the. This arises under specific circumstances for a given alloy. Potentialph diagram which demonstrates the regimes for intergranular and transgranular scc at 24 c in solutions containing different amounts of co2. Stress corrosion cracking scc can slowly destroy your brewery equipment without warning. Kop stress corrosion cracking of pipelines av y frank cheng pa. No matter how well these pipelines are designed, constructed and protected, once in place they are subjected to environmental abuse, external damage, coating disbondments, inherent mill defects, soil movementsinstability and third party damage. Jul 16, 2011 there is a free corrosion condition below the coating that results in an environment with a ph around 5 to 7. Use features like bookmarks, note taking and highlighting while reading stress corrosion cracking of pipelines wiley series in corrosion. Frank cheng is a professor and canada research chair in pipeline engineering. Corrosionpedia what is stress corrosion cracking scc.
Explains why pipeline stress corrosion cracking happens and how it can be prevented pipelines sit at the heart of the gl. His research is to advance the mechanistic understanding of material corrosion and degradation in oilgas and pipeline systems, and to develop effective techniques for assessment, prevention and prediction of pipeline failures, as well as for improvement of asset integrity. Scc occurs as a result of a combination between corrosion and tensile stress. For the susceptibility to stresscorrosion cracking, the directional variation can be appreciable and must be considered in the design of the fabricated hardware. Download it once and read it on your kindle device, pc, phones or tablets. Scc results from the formation of cracks due to various factors in combination with the environment surrounding the pipeline that together reduces the pressurecarrying capability of the pipe. It is especially important to avoid any mechanical tensile stress concentration, which will occur at sharp edges and notches. Stresscorrosion cracking scc is a term used to describe service failures in engineering materials that occur by slow, environmentally induced crack propagation. Stress corrosion cracking scc of an aircraft component.
Stress corrosion cracking of pipelines y frank cheng. Tensile stresses may be directly applied residual, and the problem is often very complex. Stress corrosion cracking facts and how to reduce the risk. The applied load stress increased the corrosion rate at the crack tip, contributing to crack propagation. Stress corrosion cracking in pipelines sciencedirect. Weixing chen pipeline operation strategies for mitigating the risk of failures caused by stress corrosion cracking and corrosion fatigue.
An extensive failure analysis shows how many service failures occurred in the industry and what kind of alloys and stresses led to initiation and propagation of stress corrosion cracks which caused these service failures. Explains why pipeline stress corrosion cracking happens and how it can be. Cheng is an internationally recognized authority in corrosion science. Frank, 1969 stress corrosion cracking of pipelines y.
Stress corrosion cracking scc of pipelines, including hydrogen. Stress corrosion cracking of gas pipeline steels of different strength. Stress corrosion cracking of gas pipeline steels of. Stress corrosion cracking how is stress corrosion cracking. The appearance of the fracture face is crystalline, although some rusting has taken place since the fracture. Use features like bookmarks, note taking and highlighting while reading stress corrosion cracking of pipelines wiley.