6.15.1 Auxiliary boiler and services supplied by steam.

Marine Applications

1.      Tank heating

2.       Marine propulsion

3.       Aux. Eng.

4.       Pumping cargo

5.       Smothering (firefighting)

 

 

Above boiler system normally used for the production of saturated steam needed for various services.

The feed water is pumped directly to the oil-fired boiler which is used as a common steam drum for the oil-fired boiler and the exhaust gas economizer.

Steam supplied from the oil-fired boiler steam drum is send to various consumers and return back to the hot well, where the water passes through several filters. Oil tank heating steam drains first come to an observation tank and then flow to the hot well.

Atmospheric condenser is used to condense excess steam produced by the economizer.

Circulating pumps are used to circulate boiler water from the boiler to the economizer.

Atmospheric condenser control the steam pressure while the economizer is in use.

Because of its simplicity and low cost of capital, the above system is widely used and is often entirely adequate when steam production is viewed as a means of meeting the steam demand for heating services on the ship.

Economizer is a water heater which uses energy in main engine exhaust gas to heat water.

6.15.2 Types of boilers

There are two main types of boilers.

• Fire tube boiler.
• Water tube boiler

The design and arrangement of both types is just the opposite. In water tube boilers, the water passes through the tubes, and the hot gases pass around them, while in fire tube boilers, the hot gases pass through the tubes and the water around them.

 

6.15.2.1 FIRE TUBE:

          A fire-tube boiler is a type of boiler in which hot gases from a fire pass through tubes running through a sealed container of water. The heat of the gases is transferred through the walls of the tubes by thermal conduction, heating the water and ultimately creating steam.

6.15.2.2 WATER TUBE:

 

A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats water in the steam-generating tubes.

These boilers can be built to any steam capacity and pressure, Posses higher efficiency and high capacity to size ratio than fire tube boilers.

 

6.15.2.3 PACKAGE BOILER:

 

The packaged boiler is so called because it comes as a complete package. Once delivered to site, it requires only the steam, water pipe work, fuel supply and electrical connections to be made for it to become operational. Package boilers may be either water tube, fire tube or coil type. Generally, package type boilers are fully automatic.

 

 

6.15.2.4 COMPOSITE BOILER

 

Composite boiler is a boiler where an oil-fired boiler and an economizer is combined into one unit.

Composite boilers are often used in conjunction with diesel machinery, since if the exhaust gas from the engine is low in temperature due to slow running of the engine and reduced power output; the pressure of the boiler can be maintained by means of an oil fired furnace.  Steam supply can also be maintained with this type of boiler when the engines are not in operation.

6.15.3 Typical pressures of steam produced in auxiliary boilers.

Normally marine auxiliary boilers typical steam pressure is about 7 to 15 bars.

 

6.15.4 Auxiliary steam boilers range from simple fire-tube boilers to self-contained fully automated package boilers.

(Explain under previous chapters)

 

6.15.5 Differences between fire tube, water tube and packaged boilers

(Explain under 6.15.2)