Boilers are classified by water temperature or steam pressure. They may be further classified by any type of metal utilised in construction (cast iron, steel, or copper), with the kind of fuel or heat element (oil, gas, or electricity), or with the relationship of fire or water towards tubes (i.e., firetube or watertube).
- Low-pressure boilers are the type created to produce steam up to 15 psig or trouble approximately 250°F with pressures up to 160 psig.
- Medium- and high-pressure boilers produce steam above 15 psig or trouble above 160 psig or 250°F or both.
Boilers are generally made out of certain or welded steel. Cast iron boilers (Fig. 1) are constructed of individually cast sections and they are joined together using screws or nuts and tie rods or threaded rivets. The quantity of sections can be varied to provide a range of capacities.
Steel boilers also come in lots of configurations. They are factory-assembled and welded and shipped to be a unit. Fig. 2 illustrates a firetube boiler. The fireplace and flue gases are substantially between water. The merchandise of combustion traverse tubes towards the back then to the front as soon as more to the back before finally exiting in front. This makes it a four-pass boiler. Firetube boilers are manufactured in many other configurations for example:
- External firebox—The firebox just isn't surrounded by water.
- Dry back—Firetubes are directly available from clean-outside at the rear of boiler.
- Scotch-Marine—Employs low tide volume and contains an easy response.
Watertube boilers are steel body boilers for high capacity requirements of greater than two million Btu by the hour (Btu/h). Watertube boilers work with a water-cooled firebox which prolongs everything of furnace walls and refractories.