Boilers / boilers are closed vessels where burning heat is flowed into the water until hot water is formed or steam is a work energy. Water is a useful and inexpensive medium for delivering heat to a process. Hot water or steam at certain pressures and temperatures have energy values ​​which are then used to drain heat in the form of heat energy into a process. If the water boils to steam, the volume will increase by about 1600 times, producing energy that resembles explosive gunpowder, so the boiler system is equipment that must be managed and maintained very well. 

• Fire tube boiler In a fire pipe boiler, the fluid flowing in the pipe is a flame gas (the result of combustion), which carries heat energy, which immediately transfers it to the boiler water through the heating field. The purpose of these fire pipes is to facilitate the distribution of heat (heat) to the boiler water. Fire / gas smoke flows in the pipe while water / steam outside the pipe Drum serves for the place of water and steam, besides that the drum is also a place for heating. The heating field is located inside the drum, so the area of ​​the heater that can be made is limited.
• Water pipe boiler (water tube boiler) In the water pipe boiler, the fluid flowing in the pipe is water, heat energy is transferred from the outside of the pipe (ie the kitchen space) to the kettle water.

How it works: 
The ignition process occurs outside the pipe. The heat produced is used to heat a pipe containing water. The feed water was previously conditioned first through Ecomonizer. The resulting steam is then collected first in a steam drum until it matches. After going through the secondary superheater and primary superheater stages, steam is released into the main distribution pipe. 

• The level of efficiency of heat produced is quite high.
• Less tolerant of the quality of water produced from a water treatment plant. So that water must be conditioned on minerals and other substances that are soluble in water.
• This boiler is used for the needs of very high steam pressures such as in power plants.
• Using fuel oil, and gas for boiler water tubes that are assembled from the factory.
• Using solid fuel for boiler water tubes that are not assembled at the factory

2. Based on the usage, the kettle can be classified as:

1. Stationary boiler or fixed kettle.
2. Car boiler (mobile boiler), moving kettle or portable boiler.

Which includes a car kettle, is a kettle that is installed on a mobile foundation, such as a locomotive boiler, car booth and a long kettle and others that seem to include a marine boiler.

3. Based on the furnace positition, steam boiler 4. Based on the number of boilers, this boiler is classified as:

1. Single boiler with a single tube (single tube steam boiler).
2. Kettle with double aisle (multi tube steam boiler).

5. Depending on the shell lid shaft, the kettle is classified as:

1. Upright boiler (vertical steam boiler), like the Cochrane kettle, Clarkson kettle and others like it
2. Horizontal steam boiler, such as cornish, Lancashire, Scotch and others.

6. According to the shape and location of the pipe, steam boilers are classified as:

1. Kettle with straight, bent and grooved pipes (straight, bent and sinous tubing heating surfaces).
2. Kettle with flat-sloping and upright sloping pipes (horizontal, inclined or vertical tubular heating surface)

7. According to the water circulation system, steam boilers are classified as:

1. Natural circulation steam boiler.
2. Kettle with forced circulation (forced circulation steam boiler). 

1. Boiler with natural fuel.
2. Boiler with artificial fuel.
3. Steam boiler with electric kitchen.
4. Steam boiler with nuclear energy.