PM Task Report 6/16/2010

Component Type: Heat Exchanger - General Tube TypeTask Name: Cleaning

Criticality Critical MinorDuty Cycle High Low High Low High Low High Low

Service Conditions Severe Mild Severe MildCHS CLS CHM CLM MHS MLS MHM MLM2Y AR AR AR AR AR NR NR

Task ObjectiveThe primary objective of Cleaning is to remove corrosion, fouling and scaling material from the inner surface of tubes. This is the only preventive task that prevents corrosion or slows its progression, maintains tube reliability, and extends the life of the tubes. The interval is very dependent on plant conditions.

Task ContentCleaning should include the following: Evaluate the degree and type of performance degradation and the type of fouling. Determine the appropriate cleaning method or process that will provide the best results and limits the damage to the heater heat transfer materials. Current cleaning methods that are available: Metal scrapers Plastic scrapers Nylon brushes Hydrolyzing Chemical cleaning

Principle Failure Location And Causes:The primary objective of Cleaning is to remove corrosion, fouling and scaling material from the inner surface and out of the tubes. This is the only preventive task that actually prevents corrosion or slows its progression, and extends the life of the tubes.

Progression Of Degradation In Time:The corrosion, scaling, and fouling processes of various kinds are all quite common in the industry and sometimes represent chronic conditions, or otherwise initiate randomly, often progressing rapidly.

Support For The Task Interval And Relation To Other Tasks:Critical heat exchangers that run continuously under severe conditions are recommended to be cleaned at each outage. All other categories would be cleaned when the equipment is already out of service, and contingent on the known fouling history. The cleaning would be performed after an Internal Inspection; under favorable conditions it might be limited to the removal of obvious macrofouling such as clams, from the surface of the tube sheet.

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