Seal pans, inspection

Olefins Process water stripper A bottom downcomer installed bade-ward caused a restriction between the downcomer bottom and the seal pan walL Qrdic flooding resulted. Ensure adequate inspection even when internal is hard to get at. 

Refinery Stripping tower Bottom seal pan inadv lently blocked off during a revamp in which a rdxnler was replac by steam ii jec-tion. Column qierated, but flooded prematurely. Closely inspect modification areas in the tower following revamps. 

Before closing up a tower, don t neglect to inspect the seal pan to make sure it s free of gloves and dead rats. 

I have a personal dislike of this widely used device. The idea of the vortex breaker is to prevent swirling liquid from conveying vapor into the draw-off nozzle. Sometimes though, trash lost in the tower during a turnaround gets caught on the vortex breaker. Since the draw nozzle typically is located in a sump below the seal pan, it may be hard to inspect. In some cases, it would be best to just cut off the vortex breaker. This is fine if the nozzle exit velocity is less than 3 or 4 ft/s. 

The seal pan itself is also hard to inspect, as it is usually hidden inside the draw-off sump. Corrosion deposits may accumulate in the seal pan and cause the trays above to flood. A small mirror is a good tool to observe these hard to reach locations maintenance folks use this tool all the time. 

Much more importantly, vortex breakers trap rags, gloves, and other trash left in towers during construction or turnarounds. If a draw-off nozzle is equipped with both a downcomer seal pan and a draw-off box, then the draw-off nozzle is difficult, and oftentimes impossible, to inspect. Installing a vortex breaker that is not needed due to low draw-off velocities is just looking for trouble, without any justification. 

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