HP Editorial Comment: The silent assassin: Corrosion
This months special report focuses on corrosion. Often, uncontrolled corrosion undermines the mechanical integrity of process equipment and infrastructure. It is often identified as the root cau..
This month’s special report focuses on corrosion. Often, uncontrolled corrosion undermines the mechanical integrity of process equipment and infrastructure. It is often identified as the root cause for near-miss and serious accidents in the hydrocarbon processing industry (HPI). Failures attributed to corrosion can occur over time or in days.
Corrosion occurs either in a uniform manner or a localized event. Many factors must come together to degrade process equipment, instrumentation, piping and infrastructure.
The industry fully understands that plant assets are very vulnerable to this silent mechanical-integrity assassin. The American Petroleum Institute Recommended Practice 571 (API RP 571), Damage Mechanisms Affecting Fixed Equipment in the Refining Industry, provides background information on damage that can occur to equipment in the refining process. API RP 571 lists over 60 damage mechanisms, with 25 being corrosion-damage mechanisms and 11 of those specific to refining operations.
Rust never sleeps. Corrosion is an expensive condition related to rust and other oxidization mechanisms. According to Marsh & McLennan’s The 100 Largest Losses, 1972–2011, Large Property Damage Losses in the Hydrocarbon Industry, 22nd Ed., the five-year losses in the refining sector have been increasing since 1977. The refining industry had accident/damage losses approaching $2 billion between 2007 to 2011. Piping failures or leaks due to corrosion or incorrect metallurgy, along with startup and shutdown events, were the significant causes for these losses.
The European Commission’s Joint Research Centre (JRC) operates an incident database called European Major Accident Report System (eMARS); it lists 137 major refinery accidents occurring in EU countries since 1984. About 20% of these accidents are attributed to corrosion as the root cause for the failure.
According to a study by the JRC, risk management programs (RMPs) were a factor in managing corrosion. In reviewing the history of corrosion-related accidents, RMPs were not conducted or were insufficient in identifying corrosion hazards. The study also found related inadequacies in the safety management processes:
Inadequate risk analysis at the design stage
Insufficient risk analysis and failure to conduct the management of change (MOC) review before implementing a process change
Failure to identify or address process risks in planning inspections
Poor identification of hazards and risks for other purposes such as repairs and establishing detection and mitigation systems.
MOC problems resulted in many corrosion-related events. Any change in process/operating conditions and new equipment without proper MOC reviews can lead to new corrosion risks.
Refining operations bring together fluids that are corrosive and can oxidize surfaces; they include water, acidic compounds and gases and crude oil. These corrosive fluids are handled under high temperatures and pressures; all promoting oxidation of metal surfaces unless mitigation efforts are maintained.
According to the JRC report, hydrotreating and crude distillation units have the highest corrosion–related incident rates. Ammonia and sulfur compounds with water and steam are the main corrosion-promoting actors.
Corrosion will always be a risk for the HPI. How organizations develop and maintain their RMPs and management of plant assets will impact the value of future losses. Best practices in maintenance and inspection and adherences to proper operating procedures can provide the best insurance. HP
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