Corrosion-Related Failures

Corrosion in the oil and gas industry has been acknowledged since the 1920s, and corrosion and other related failures still cost the offshore oil and gas industrial sector hundreds of millions of dollars each year [6]. As per Reference 7, corrosion-related failures constitute over 25% of failures in the oil and gas industrial sector [7]. A study conducted in the 1980s reported the following causes (along with their degree of contribution in percentages) for corrosion-related failure in petroleum-related industries [7,8]  

1 Types of Corrosion or Degradation That Can Cause Failure 

The possible types of corrosion or degradation that can cause failure are as follows [6]  

Commonly used corrosion/condltion monitoring methods. 

Corrosion monitoring of internal surfaces may be performed by using the combination of the following methods [6]  

A liquid pipeline has less stored energy than a gas pipeline, and a rupture does not cause an explosion. However, an explosion can occur on ignition of an explosive product. In the case of a hazardous liquid product pipeline, the environmental impact can be as serious as an explosion. The risk of an oil leak from the Trans-Alaska Pipeline System has continued to be the primary driver for the aggressive corrosion prevention and inspection program maintained by the operator. Of major concern is the risk of oil leakage into water streams and thereby contaminating water supplies. 

Corrosion-induced pipeline failures can result in the following  

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Ion probes. Determining the level of ions in solution also helps to control corrosion. An increase in concentration of specific ions can contribute to scale formation, which can lead to a corrosion-related failure. Ion-selective elec trode measurements can be included, just as pH measurements can, along with other more typical corrosion measurements. Especially in a complete monitoring system, this can add information about the effect of these ions on the material of interest at the process plant conditions. 

Failure analysis. Often, for a corrosion-related failure, data from the probes are examined to look for telltale signs that could have led to detection of the failure. In some cases, evidence can be found that process changes were occurring which led to the failure. This does not mean that the probes should have detected the failure itself. Determination of an imminent corrosion-related failure is not possible, even with the most advanced monitoring system. 

Once the wear of the drillstring and a better control of stress concentration are achieved, it is possible to reduce corrosion-related failure of the drillstem. 

Galante, J. and Rostoker, W., Corrosion Related Failures in Metallic Implants and Experimental Study , Clinical Orthopaedics and Related Research, 86, 237-244 (1972)... 

Polarization probes. Polarization methods other than LPR are also of use in process control and corrosion analysis, but only a few systems are offered commercially. These systems use such polarization techniques as galvanodynamic or potentiodynamic, potentiostatic or galvanostatic, potentiostaircase or galvanostaircase, or cyclic polarization methods. Some systems involving these techniques are, in fact, used regularly in processing plants. These methods are used in situ or in the laboratory to measure corrosion. Polarization probes have been successful in reducing corrosion-related failures in chemical plants. 

The impetus for further developments was the recognition of the economic significance of corrosion phenomenon during the 19th century that led the British Association for the Advancement of Science to sponsor corrosion testing projects such as the corrosion of cast and wrought iron in river and seawater atmospheres in 1837. Early academic interest in corrosion phenomenon (up to the First World War) was followed by industrial interest due to the occurrence of equipment failures. An example of this is the corrosion-related failure of condenser tubes as reported by the Institute of Metals and the British Non-ferrous Metals Research Association in 1911. This initiative led to the development of new corrosion-resistant alloys, and the corrosion related failure of condenser tubes in the Second World War was an insignificant problem. 

Corrosion has a tremendous effect on the environment in the sense corrosion-related failure of oil pipelines or gas pipelines or oil tankers can have very detrimental effect on the environment in the form of water and air pollution, leading to the demise of aquatic life. Corrosion-related accidents can in principle destroy natural fauna or flora since these are irreplaceable. 

According to Trethewey and Chamberlain5 corrosion management is defined to include people along with corrosion control which concerns with the materials used in a particular environment. The corrosion related failure may be due to (i) primary corrosion mechanism and/or (ii) secondary corrosion mechanism as shown below ... 

Corrosion-related failure (32) that occurred in refineries of fhe Union Oil Company of California resulted in a disastrous explosion and fire. An amine absorber pressure vessel rupfured and released large amounts of flammable gases and vapors. The accident resulted in 17 deaths 17 individuals were hospitalized and more than 100 million in damages resulted. 

The most important consideration in the evaluation of corrosion-related failure is safety, that is, whether the failure causes a loss of life or of function or secondary damage that could have adverse effect on operating safety. A critical failure is any failure that could affect adversely the safety of operation of both the equipment and the operating personnel. The term, direct effect, implies certain limitations. The impact of the failure must be immediate if it is to be considered direct. Further, the consequences must result from a single failure and not from a combination of the failure with another that is yet to occur. If a failure has no resultant effect on the system, it cannot by definition have a direct effect on safety. 

The F-16 fighter aircraft crashes and the Aloha incident described earlier are good examples of documented corrosion-related failures. Now we turn our attention to some corrosion-related accidents involving great loss of life. 

Corrosion-related failures constitute over 25% of the failures experienced in the oil and gas industries. More than half of these failures are associated with sweet (COj) and sour (H2S) produced fluids. An analysis of failures assessed during the 2000s in a very limited industrywide survey showed a high degree of damage caused by corrosion and other types of material degradation. 

By any standard of measure, corrosion is a severe and costly problem in the drilling industry. Corrosion costs the oilfield millions of dollars each year, and a large portion of this expense is due to the replacement of steel goods. Other expenses include lost drilling time due to equipment repairs, fishing operations, and extra trips caused by corrosion-related failures. 

Hence, the risk of a corrosion-related failure equals the probability that such a failure will take place multiplied by the consequence of that failure. Consequence is typically measured in hnancial terms—that is, the total cost of a corrosion failure, including the cost of replacement, clean-up, repair, downtime, and so on. 

R. B. Pond and D. A. Shifler, High-temperature corrosion-related failures, in AS MHandbook, Vol. 11, Failure Analysis and Prevention, ASM International, Materials Park, OH,... 

Smart accelerated corrosion testing that accurately predicts performance under a range of exposures, ensuring durability, and early detection of unforeseen corrosion-related failure mechanisms. 

G161-00 Standard Guide for Corrosion-Related Failure Analysis. 

Corrosion-Related Failures in Feedwater Heaters, Electric Power Research Institute, Palo Alto, CA, Final Report CS-3184, July 1983. 

Beavers, J. A. and Koch, G. H., "Review of Corrosion Related Failures in Flue Gas Desulfurization Systems, Corrosion/82, Paper No. 202, NACE, Houston, TX, 1982. 

In the case of pumped wells where tubing, rods, and pump are pulled periodically for maintenance, visual inspection is used to evaluate progress of corrosion. These records together with records of corrosion-related failures of downhole equipment serve as a means of monitoring effectiveness of mitigation procedures. 

Industrial risk assessment is a careful examination of potential hazards that may affect the operation of a system, be it large and complex or relatively simple. These risks may be associated with the risks to the safety and integrity of physical assets, risks to the environment, financial risks from various decisions, and also risks from corrosion or poor corrosion mitigation procedures. Corrosion-related failures may be a major source of risk in many industry sectors. In the offshore oil and gas installations, for example, corrosion can be a life-limiting cause of deterioration by various corrosion damage attacks of plant items. 

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