We are having issues with oil possibly getting trapped between the finned tubes in a flooded evaporator where seawater goes on the inside of the tubes and ammonia on the outside. The oil is preventing heat exchange to happen. The oil we have been using is mineral oil type Cappella 68. We have in the past manufactured and installed many similar systems with R-22 and finned tubes but never seen this problem, is there something with ammonia and the oil mix that causes the oil to get stuck on the tubes and therefore preventing heat exchange?

Has anybody had any similar prob/ems and if so how did you rectify it?