REMOVAL OF OIL FILMS FROM STAINLESS-STEEL TUBES

The removal of oil films from the inner surface of a stainless steel t ube cell using aqueous cleaning solutions was studied. The two oils us ed in the cleaning experiments, Sunquench 1042 and heavy mineral oil, contained P-32 labeled tributylphosphate (TBP) as a radioactive tracer . The beta(-) particles emitted from the radioactive TBP were detected by a CaF2 scintillator and used as a measure of the amount of oil rem aining in the tube cell. Cleaning experiments performed at different f low rates, surface treatment, and surfactant concentrations indicated that initially the oil films were removed rapidly. At the end of the e xperiments, the oil removal rate reduced significantly, eventually bec oming negligible. The stainless steel morphology affected oil removal significantly, and the rougher tube tended to retard the oil removal. The rate and extent of the decontamination were significantly increase d in the presence of sodium dodecyl sulfate, a nonionic surfactant. Ex perimental data were compared to a hydrodynamic model based on the rem oval of a liquid contaminant from a solid surface by an immiscible flu id. The model deviated from the experimental data due to the presence of instabilities at the oil-water interface.