Process equipment and piping in chemical and petrochemical plants and petroleum refineries have to be cleaned periodically as part of normal maintenance operations to remove fouling that interferes with process flow, heat transfer, or other operations. Cleaning is also necessary to allow safe personnel entry prior to equipment inspection, repairs, or modifications. Most cleaning operations are expensive and time-consuming and need to be planned, budgeted, and carried out in a timely fashion to ensure minimum interference with normal process or maintenance operations. Certain process equipment and piping may also have to be cleaned prior to being put into service for the first time. Such pre-commission cleaning removes rust, dirt, and other debris that formed or entered during fabrication, shipment, or erection, and that are likely to cause damage after start-up. process equipment and piping in chemical plants, petrochemical plants and petroleum refineries. Practical information and guidance is provided for plant engineers and operators who, from time to time, are charged with planning various cleaning operations that will be carried out either by in-house maintenance personnel or outside cleaning contractors. Sufficient information is given to enable the nonspecialist to either propose cleaning procedures or evaluate cleaning procedures proposed by others. The manual enumerates a multitude of factors that need to be considered before a cleaning operation is started, including timing, alternative methods, costs, manpower requirements, safety concerns, and waste disposal issues.