Here are the types of boilers:
I. Auxiliary Boilers
These boilers are typically used for auxiliary purposes and include various designs:
- Scotch Boiler
- Historically, this has been the most common multi-tubular cylindrical or tank boiler used at sea for auxiliary purposes.
- Its main components include a cylindrical shell containing the furnaces.
- Typically, two furnaces are fitted for boiler shell diameters up to 4 meters, and three for larger diameters.
- The fuel is burned in water-cooled furnaces, and hot gases then enter the combustion chamber for steam generation.
- It is considered a strong and robust type, capable of operating with poor quality feed water.
- Internal access is provided by a manhole in the top of the shell.
- Cochran Smoke Tube Boiler
- This is a typical vertical tank boiler suitable for auxiliary purposes, designed to produce relatively small amounts of low-pressure steam.
- It features a hemispherical crown.
- Combustion products pass from the furnace into a combustion chamber lined with refractory material, and then through smoke tubes at the front of the boiler.
- These boilers can be operated with either solid or liquid fuels, though oil firing is invariably used in sea-going vessels. It can also be adapted for use as an exhaust gas boiler.
- Clarkson Thimble Tube Boiler
- This type of boiler generates steam by heating a series of horizontally tapered thimble tubes externally.
- Its basic form consists of an outer shell enclosing a cylindrical furnace, with the thimble tubes positioned inside.
- The design can be either riveted or welded construction and often includes a corrugated furnace.
- Spanner Vertical Smoke Tube Boiler
- This is a vertical tank boiler composed of an outer shell and a cylindrical furnace, with vertical smoke tubes connecting to a cylindrical smokebox at the top.
- Early versions used riveted construction, but later designs are all-welded.
- Aalborg Q9 Auxiliary Water Tube Boiler
- This is a vertical water tube boiler designed for auxiliary purposes, offering a compact design, a good evaporation rate, and flexible output.
- Fuel is burned in water walls, receiving radiant heat from the furnace.
- It utilizes positive water circulation, with heated tubes provided by external downcomers. Stays are fitted in the steam drum and annular water space to support flat surfaces.
- Forced Circulation Boiler
- A general type of auxiliary boiler where water is actively circulated. These boilers often serve as steam receivers for exhaust gas systems and can be modified for waste incineration.
- Compared to tank-type boilers, they are considered safer and more responsive to intermittent steam demands due to the smaller volume of water they contain.
- Package Boiler
- These are relatively small, self-contained units typically mounted on a single bedplate. They are used when there are small, intermittent steam demands.
- They commonly include one or two cylindrical water-cooled furnaces.
- Dual Pressure Boiler
- Used in some marine auxiliary systems, this boiler supplies low-pressure saturated steam to a separate steam generator.
- The primary system often uses distilled water to prevent contamination of the secondary system.
- A safety valve is fitted to the steam generator to lift at the normal working pressure of the secondary system.
- Composite Boilers
- These boilers are designed to generate steam using either the main engine exhaust gases or by burning oil in the boiler furnace.
- A common design is the vertical, single-pass smoke tube type.
- Exhaust Gas Boilers
- These are heat exchangers installed in the main engine uptake to recover heat from exhaust gases and produce steam. They can sometimes be combined with an oil-fired water tube boiler.
II. Water Tube Boilers
Water tube boilers are characterized by higher efficiencies and steam temperatures, and include various specific designs:
- General Characteristics of Water Tube Boilers
- They are more efficient heat exchangers, consisting of a large number of small diameter tubes.
- They have a lower overall weight and require less refractory material, allowing for rapid steam raising.
- Their layout enables efficient combustion and allows the boiler shape to be adapted to available space.
- They typically consist of a steam drum, one or more water drums, and various headers interconnected by numerous tubes.
- Babcock and Wilcox Header Boiler
- A single-pass design with water walls fitted at the sides of the furnace and generating tubes connecting to a steam drum.
- Foster Wheeler D-type Boiler
- Features two drums: a larger steam drum and a smaller water drum. A water-cooled furnace is located on one side, with water walls and external downcomers.
- Foster Wheeler Controlled Superheat Boiler
- This is a two-furnace type boiler where the superheat temperature can be controlled by adjusting tube sizes and the position of the superheater.
- Babcock and Wilcox Selectable Superheat Boiler
- Equipped with cyclone steam separators in the steam drum, which can be arranged in a fore-and-aft position. Water walls are fitted to the roof, side, and rear walls of the furnace.
- Foster Wheeler ESD.1 Boiler
- Similar to the D-type, it has two drums and a water-cooled furnace positioned on one side. It utilizes close-pitched 50 mm diameter water walls and multi-loop superheaters with mild steel elements, expanded and bell-mouthed into headers.
- Foster Wheeler ESD.11 Boiler
- An evolution of the ESD.1, this boiler also has two drums and a water-cooled furnace positioned to one side. It features a split gas passage with dampers to regulate gas flow.
- Foster Wheeler ESD.111 Boiler
- This design includes two drums and a fully water-cooled furnace. Final superheat temperature control is achieved via a water-cooled attemperator mounted in the steam drum.
- A variant, referred to as an ESD.111 type (radiant heat) boiler, generates steam primarily through water walls, without relying on banks of generating tubes, to absorb high radiant heat.
- Combustion Engineering VSM 9 Boiler
- This boiler consists of two drums (a steam drum and a water drum) and a bank of 32 mm diameter generating tubes. The furnace is located on one side, and hot combustion gases pass over screen tubes to the superheater.