The vertical two drum water tube boiler used normally on ships is top-fired and equipped with a steam atomising burner. As the burner, the local control panel and all relevant boiler mountings are mounted on top of the boiler, this can easily be operated and monitored from the burner platform.

The principal drawing of a typical auxiliary boiler is shown in figure below. The steam drum is cylindrical with two flat plates of equal thickness. Because of the internal pressure, the flat plates are mutually connected by vertical solid stays. The steam drum is furnished with the necessary internal fittings to ensure an even distribution of the feed water, of the circulation water from the exhaust boiler and to ensure a sufficient dryness of steam.

The burner cone in the furnace opening are an integrated part and accordingly no refractory are provided in the top of the furnace room. Manholes are conveniently placed in both drums and inside the drums enough space is available for inspection and maintenance. The water drum is designed similar to the steam drum. The drum size gives optimal space for the heating coil and easy access for inspection.

As standard the auxiliary boiler is prepared for tack welding along the foundation of the boiler shell. Some boilers may, however, be provided with four support feet instead, one as fixed foot and the others with the possibility of thermal expansion.

Both the furnace and the generating tube bank are located asymmetrically and are separated by the screen wall. Besides the screen wall the furnace consists of gas tight polygon shaped membrane walls. The generating tube bank consists of vertical pin-tubes arranged in a staggered configuration. To avoid any risk of vibration problems supports are arranged.

The flue gas passes through the deflected tubes at the bottom of the screen wall, up through the generating tube bank and out through the smoke outlet box. An effective circulation in the boiler is achieved bye means of down comers. The bottom tube plate is first covered with coat of insulation refractory and above with castable refractory. Access to the furnace is possible through the access door at the bottom of the furnace. Inspection of the generating tubes is also possible through the inspection door at the bottom of the furnace.

Inspection of the burner flame is possible through the two inspection holes arranged in two heights on the furnace panel wall.

Reference:

‘MISSION™ OL boiler Manual’ by Aalborg Industries