Double evaporation boilers

• A double evaporation boiler uses two independent systems for steam generation and therefore avoids any contamination between the primary and secondary feedwater.
• The primary circuit is in effect a conventional watertube boiler which provides steam to the heating coils of a steam-to-steam generator, which is the secondary system.
• The main reason for the adoption of this design of boilers is to allow use of modern high efficiency watertube boilers witghout fear of damage through contamination by cargo or fuel oils.The basic design consists of a D-Type boiler design upon which is mounted a Steam/Steam generator drum.
• The steam generated by the main boiler heats water in the Steam/Steam generator which produces steam requirements.
• The primary drum is initially filled with high quality feed water and suitably dosed.
• The  main  reasonfor  the  adoption  of  double  evaporation  boilers  in  tankers are  concerned  of  damage  caused  by  oil  and  sulphur  which  enters  the  feed  systems  through  leaky  steam  heating  coils  used  for  heating  the  oil  in  cargo  tanks.