Other Cleaning, Washing, Steaming, and Purging Operations

Other Cleaning, Washing, Steaming, and Purging Operations 

Cleaning, washing, steaming-out and purging of equipment, vessels, and pipelines in preparation for maintenance can create problems. Often equipment cleaning does not attract much attention and is frequently carried out by individuals with the least amount of technical training. A few problems that have been reported will follow. 

A similar incident involving steam condensation was reported in the Hazard of Water in Refinery Process Systems [6], where the caption on a photo of a badly damaged tank states, A vacuum vent and one open hatchway was not enough to prevent damage when steam condensed and pulled in the top two courses of this 35 ft. diameter by 21 ft. high wash tank.  

In another tank collapse incident, a tank containing a solution of ammonia and water was being emptied and cleaned. After employees emptied the tank of liquid ammonia, they added water to rinse the vessel. While the water was being added the sides of the tank were sucked in. The ammonia vapor remaining in the tank dissolved in the water so rapidly that air could not enter through the vent to prevent the collapse. [8] 

Calculations were made. Engineers figured that a vent of about 30 inches (76 cm) in diameter would have prevented the destructive vacuum from collapsing the tank during the ammonia absorption incident. A giant-sized vent was impractical for this installation, hence they concluded that water should be added slowly through a restrictive orifice. [8] 

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Other cleaning, washing, steaming, and purging operations... 

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