the one that is use in marine industry?
A main boiler is used to drive the ships engines. Auxiliary boilers are used to drive generators and make drinking water and in very old ships drive steam powered machinery like winches and cranes.
main boiler is used for propulsion while auxiliary boiler is used for things like heating of HFO, purifier operation, and hotel needs of the ship such as supplying hot water to the galley.
A main boiler is exactly what it says, THE MAIN BOILER. It is the boiler that is used on an every day or regular basis. An auxilliary boiler is a BACK UP BOILER that may be used when or if there is a problem with the main boiler or the main boiler needs to be put out of service for annual maintenance, cleaning of the tubes or yearly inspection.
one is always used and the other isnt
