Materials Performance

AUG 2017

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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61 NACE INTERNATIONAL: VOL. 56, NO. 8 MATERIALS PERFORMANCE AUGUST 2017 — A rem edi al a c tion , w hi ch can reduce the incumbent corrosion rate and thereby prolong the fea- ture's remaining life (e.g., optimiz- ing an incumbent chemical treat- ment; enhancing dehydration for a wet gas process; or improving con- trol of pertinent operation and process parameters such as f low rat es, t emp eratures, and pres- sure s, in a c c ord an c e w ith th e required design specifications). This can delay the occurrence of failure for the foreseeable future. — Repair or replacement (e.g., clamp- ing, wrapping, or removing the failed/at-risk item and installing a new one) if it is too late for a reme- dial action to reduce the existing corrosion rate or lessen the corro- sivity of the environment. The Failure Prediction Component Predicting the occurrence of a failure requires the ability to foresee where, when, and how a failure is likely to happen with a great degree of confidence. Predicting Where a Failure Will Occur To predict the location of a probable failure, several things should be deter - mined as accurately as possible. First, the existing alloy systems and the prevailing (internal and external) environmental con- ditions should be evaluated to determine whether any deterioration mechanisms (i .e., corrosion , erosion-corrosion , and cracking) are possible, even if they have not been observed, identified, or experienced before. Once all such locations, components, or features have been determined, the next step is to perform a failure risk assessment (FRA) to determine which locations or components have the greatest failure risk. Furthermore, to more accurately deter - mine the location of future failures, any specific components or features that are more susceptible to a particular deteriora- tion mechanism vis-à-vis other compo- nents in their immediate proximity should be identified. For example, in reservoirs that produce sand or in production systems that contain any sort of hard, solid particles, erosion and erosion-corrosion can affect bends, el b ow s, an d t e e j un ction s m ore th an straight pipework spools and even the asso ciat ed transfer pip elin es. Anoth er example is systems that are contaminated with bacteria. The lower portions of hori- zontal components are far more suscepti- ble to microbiologically influenced corro- sion than the upper portions of the same components. Additionally, the magnitude of the deterioration rate (i.e., the corrosion rate or the crack propagation rate) and its relationship to a component's remaining life can be used as another indicator for d et erminin g th e lo cation of pro b abl e failure(s). Predicting When a Failure Will Occur The time of a component failure can be predicted by using either the pertinent cor- rosion rate or the remaining life data. The following information can be used individ- ually or combined (where applicable) to carry out such predictions: • Wall thickness inspection data by ultrasonic testing • Corrosion monitoring and fluid sam- pling data • Intelligent pigging data analysis • Dissolved oxygen concentration data • Wall thickness data via radiography Predicting How a Failure Will Occur Knowing the prevailing and pertinent deterioration mechanisms (i.e., corrosion, corrosion cracking, or erosion-corrosion) can help establish how a component is going to fail. The next step is to determine whether the indicated deterioration mechanism(s) is going to produce a failure via: • A pinhole (due to pitting or localized corrosion) • A rupture (due to uniform corrosion, corrosion cracking, or erosion-corro- sion) • A crack (due to corrosion cracking) The Failure Prevention Component Corrosion failure prevention could be carried out by implementing a remedial action that results in the reduction of the incumbent corrosion rate, thereby prolong- ing a component's remaining life; a repair/ FIGURE 1 The two components of the corrosion failure preemption process and their associated parameters.

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