How does Scotch Marine Boiler work? | What is Scotch Boiler?

The boilers are most commonly used to generate steam from water. There are multiple types of boilers that are designed according to the nature of the applications. A Scotch boiler (or scotch marine boiler) is a most famous type of fire tube boiler. This article mainly explains the working, types, and components of the scotch marine boiler.

What is a Scotch Marine Boiler?

A Scotch marine boiler is a type of boiler in which the hot flue gases flow through a set of tubes within a tank of water. The scotch boilers are most commonly used on ships.

Scotch Marine boiler

These boilers are most commonly used in marine applications because of their high operational efficiency and compactness. They have the capability to use all types of water. They don’t need external chimney and brick installation.

A scotch boiler is a descendant of the conventional Lancashire boiler. It has multiple furnaces to provide a larger heating surface for a given furnace.

Working of Scotch Marine Boiler

  • First of all, solid fuel (such as coal) is placed onto the grate into the furnace via a fire hole.
  • After fuel introduction, fire is supplied to the fuel through the fire hole, which burns the fuel.
  • As the solid fuel burning process starts, the hot flue gases produce inside the furnace. The produced hot gases are transferred from the furnace to the combustion chamber.
  • In the combustion chamber, the hot gases are used to heat the water; due to that, water converts into steam.
  • The resulted steam is delivered to the steam turbine to produce electricity.
  • Due to the combustion of the fuel, smoke and exhaust gases are produced that are transferred to the chimney.
  • The chimney expels the hot flue gases and smoke to the environment.

Construction of Scotch Marine Boiler

A Scotch marine boiler has a horizontally arranged drum. This drum has a diameter between 2-5 to 3-5 meters. This type of steam boiler can be double-ended steam or single-ended.

The single-ended boiler has a length from 3 to 5 meters. It has one to four furnaces that enter from the boiler’s front side. A double-ended steam boiler has a length from 6 to 5 meters. It contains 2 to 4 furnaces on each end.

The single-ended boiler contains one to four furnaces. Out of these four furnaces, each furnace contains its own combustor. These furnaces usually corrugate for added strength. The combustor has fine flat plates that are very important such as the tube plate, two side plates, backplate, and the top plate.

The Scotch boiler contains multiple horizontal smoke pipes that link the chimney and combustor.  

Read More: Different types of Boilers

Types of Scotch Marine Boiler

The Scotch Marine Boiler has the following major types:

  1. Single-ended Scotch marine boiler
  2. Double-ended Scotch marine boiler

1) Single-ended Scotch Marine Boiler

This type of boiler has a short length. The shell of this boiler has a circular shape and large diameter. The maximum length of a single end boiler is 3.5m. It contains up to four furnaces inserted through the front of the boiler. These boilers are most commonly used on ships in many countries.

Characteristics: –

  • This boiler has a short length.
  • The maximum length of this boiler is 3.5 m.
  • These boilers contain up to four furnaces.

2) Double-ended Scotch Marine Boiler

The conventional double-ended Scottish marine boiler had vertical Galloway tubes installed in the combustor. The purpose of these tubes was to improve the boiler water circulation and reduce the load on the material.

The maximum length of the double-ended boiler is 6.5m. In the case of this boiler, the furnaces are installed at both ends. And each end contains two to four furnaces.

Characteristics: –

  1. This boiler has up to 6.5m in length.
  2. It has furnaces on both ends.

Parts of Scotch Marine Boiler

The scotch boiler has the following major parts:

scotch marine boiler parts

1) Furnace

This is the area below the boiler and above the grate. The furnace is also known as a burner. It uses to combust the coal. The heat produced due to combustion is delivered to the boiler water.  

A single-ended boiler contains up to four burners. It is typically corrugated for strength. In the case of a scotch marine boiler, each furnace contains its own combustor.

2) Combustion Chamber

The combustion chamber or combustor is the area where the combustion of the fuel takes place to produce steam from the boiler water. The combustion chamber installs under the boiler shell. It contains thin plates that need to be supported: tube plate, back plate, side plate and top plate.

Read More: Working of Combustion Chamber

3) Smoke Box

It contains multiple horizontally arranged pipes that connect the combustor to the chimney. As the fuel is burnt in the combustion chamber, it produces smoke. This smoke transfers from the combustion chamber to the chimney through the smoke pipes.

4) Chimney

This part of the scotch marine boiler uses to remove boiler smoke and flue gases. As the smoke and waste gases flow from the combustion chamber to the chimney, the chimney releases them into the environment.

5) Boiler Shell

A steel plate uses for the construction of the boiler shell. This steel is bent into a cylindrical design and welded the parts.

The boiler shell has adequate capacity to hold both water and steam. This also provides safety to the internal components of the boiler. All the compulsory accessories for the boiler fit into the boiler body.

6) Soot Blower

In general, it uses to eliminate soot from the bottom of the boiler’s inner surface. If you don’t remove soot regularly, your boiler performance will also be reduced.

7) Manhole

The manhole is also known as a manway. You can easily find this hole in large boilers and vessels. It uses for the entry of a person to clean or repair the boiler.

8)  Safety valve

It provides basic safety to the boiler. It supplies instructions about the boiler water level, temperature, pressure, etc.

Advantages and Disadvantages of Scotch Marine Boiler

Advantages of Scotch Marine Boiler

  1. This boiler has small in size than other types of boilers.
  2. It has the ability to use all types of water.
  3. It is a very efficient boiler.
  4. The Scotch marine boiler doesn’t need external flues and a brickwork setting.
  5. These boilers are ideal for small power plants.

Disadvantages of Scotch Marine Boiler

  1. It requires more floor area for a given output.
  2. You can’t ea
  3. These boilers generate poor quality steam than the water tube boilers.
  4. These boilers aren’t ideal for large power plants.
  5. It has low steam production rate than the water tube boiler.

Applications of Scotch Marine Boiler

  1. The Scotch marine boilers are most usually used in marine applications due to their high operational efficiency and compactness.
  2. They use on ships.

FAQ Section

Who invented the Scotch boiler?

In the 1870s, James Howden the Scotch boiler to generate high pressures steam.

What is the efficiency of the Scotch Marine boiler?

Hurst Scotch Marine boilers are rated to 81% minimum efficiency.

What are the components of the Scotch Boiler?

The Scotch boiler has the following major components:

  1. Grate
  2. Furnace
  3. Safety valve
  4. Fire hole
  5. Combustion chamber
  6. Shell
  7. Crown sheet
  8. Fire tubes
  9. Air cock
  10. Smokebox
  11. Chimney
Read More
  1. Different types of Fire Tube Boilers
  2. Different types of Boilers
  3. Working of Lamont Boiler
  4. Types of Water Tube Boilers

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