Correct and effective corrosion monitoring strategies should be used as a proactive tool to assist with operating a plant more effectively, thereby prolonging its life and gaining optimum throughput. It also enables continuous monitoring of actual corrosion rates, allowing for timely preventative action if a variance is observed.
Current corrosion inspection and monitoring typically requires planned periodic shutdowns to inspect equipment. Scheduled shutdowns are costly in terms of productivity losses, restart energy and material costs. Unscheduled shutdowns are disruptive and often quite expensive. Internal corrosion failures result in costly cross contaminations of product and process streams. External corrosion leaks put process fluids into the plant environment and can create significant safety hazards.
Corrosion monitoring systems vary significantly in complexity, from simple coupon exposures or hand held data loggers to fully integrated plant process surveillance units with remote data access and data management capabilities. Experience has shown that the potential cost savings resulting from the implementation of corrosion monitoring programs generally increase with the sophistication level (and cost) of the monitoring system. Corrosion monitoring is more complex than the monitoring of most other process parameters because:
There are a number of different types of corrosion
Corrosion may be uniform over an area or concentrated in very small areas (Pitting)
General corrosion rates may vary substantially, even over relatively short distances
There is no single measurement technique that will detect all of these various conditions
It is therefore helpful to have previous history or even a rough estimate of the types of corrosion problems to be investigated. It is also advisable to use several complementary techniques rather than rely on a single monitoring method. Real time monitoring of pipelines, vessels and other static equipment enables a near instantaneous appraisal of the corrosivity of produced and transported fluids.
On-line nature monitoring means that corrosion information is immediately available to the operator. If corrosion activity increases as a result of process non-conformities, the corrosion information can be viewed alongside process variables (including chemical injection data) such that cause-and-effect can be determined and rapid action can be taken to overcome the problem. Effectiveness of remedial action or treatment can be similarly proven.
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