T.O. 33B-1-12-57contact the remaining penetrant layer. The action stops when the part is withdrawn from the remover, unlike lipophilicemulsifiers that become active only after withdrawal and during drainage. Figure 2-20 illustrates hydrophilic removeraction.Figure 2-20. Action of the Hydrophilic Process.2.5.5.4.3 PreRinse.2.5.5.4.3.1 Description.The clean, preclean, penetrant application and penetrant dwell steps are identical in both the lipophilic and hydrophilicmethods. However, the processes diverge with the pre-rinse step in the hydrophilic method. The part is subjected to aplain water spray following the penetrant dwell when using the hydrophilic method. The mechanical action of thewater spray removes over 80 percent of the excess surface penetrant, leaving only a very thin uniform layer of surfacepenetrant on the part which helps optimize the removal process. It reduces the amount of remover consumed, and inimmersion set-ups, minimizes contamination of remover due to penetrant carry-over. It also reduces remover contacttime since, in general, contact time is about 50 percent less when the pre-rinse step is used. This pre-rinse step cannotbe used in the lipophilic process, as the oil base emulsifier does not tolerate water.2.5.5.4.3.2 Pre-RinseProcedure.The pre-rinse step SHALL be used since it improves the efficiency of the process and minimizes hazardous waste. Thepre-rinse cycle SHALL be a coarse spray of plain water for 30 to 120 seconds, at a pressure as low as practicallypossible, not to exceed 40 psig, with a water temperature of 50°F (10°C) to 100°F (38°C). The objective is to reducethe amount of surface penetrant, while leaving only a thin layer remaining on the part.
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