Paper 2: Pre-Commission Acid Cleaning of Boilers and Heat Exchangers

Until the 1950s it was generally sufficient to clean new boilers or heat exchangers before commissioning by boiling out with alkali to remove traces of oil and grease and by subsequent flushing to remove debris. However, with the great increase in heat transfer ratings in recent years, it is shown that deposits a few thousandths of an inch in thickness can cause high internal tube temperatures which in turn can lead to corrosion of the tube metal. It is therefore obvious that the feed water quality must be very high and that it must be treated to maintain correct conditions in the heat exchanger. It is also essential to ensure that the plant enters service in a meticulously clean condition with the minimum layer of magnetite on the heating surfaces to ensure freedom from attack. The method which would be adopted at the present time to acid clean a new boiler is summarized together with precautions which should be taken. In addition, the necessity for laboratory trials before acid cleaning heat exchangers containing exotic materials is emphasized.