integrity operating windows
Corrosion-control documents (CCD) are essential inputs into effective mechanical integrity programs and risk-based inspection programs. They are particularly useful for capturing in one document the essential elements of a chemical or refining process that influences corrosion, i.e. materials of construction, process-stream chemistry, operating conditions and damage mechanisms.
The Hendrix Group Inc. has been providing corrosion consulting, corrosion prevention, and corrosion-control services for more than 35 years. Our objectives are:
The Hendrix Group offers proven expertise in developing corrosion-control documents for specific industry applications.
Variations of corrosion-control documentsCorrosion-control documents have been referred to by different acronyms, including Material Operating Envelopes (MOEs); Critical Process Variables (CPVs); Corrosion Manuals; Corrosion Control Documents, Corrosion Circuits, Corrosion Reports, Corrosion Loops, etc. They can be combined in a risk-based inspection program implementation or can be stand-alone documents.
Semi-quantitative, risk-based inspection assessments and the various RBI software tools are very useful for capturing and presenting large amounts of equipment data, for facilitating the structured assignment of risk to equipment, and for setting inspection intervals. However, RBI programs and software are not particularly useful for identifying the damage mechanisms in a unit and do not address upset or startup/shutdown damage mechanisms at all. In fact, one could argue that a typical RBI assessment program is particularly ineffective in reducing risk - and largely a poor use of personnel and money - in the absence of expert input into a unit’s damage mechanism and where those mechanisms are likely to exist.
Download the CCD presentation from the 2011 API Inspection Summit and Expo (PDF).
A corrosion control document:
CCD’s have several uses including:
As an essential component of a CCD, Integrity operating windows (IOW’s) are gaining recognition as a valuable input into a corrosion control document. What are IOWs? The American Petroleum Institute (API) has a new recommended practice in the ballot stage (API RP 584) that discuss the need to establish operating limits that address the controls necessary for process variables that might affect the integrity or reliability of the process unit. An example of an IOW is the establishment of furnace tube temperature limits to avoid premature rupture. At some established limit, say 800F, a furnace tube designed for 775 F would have a shortened service life, so operators would understand the need to maintain control of furnace firing to remain below the 775F limit. That limit of 775F would be an IOW limit for the furnace tubes.
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