Power Plant Engineering

What is a Lancashire Boiler? How Does It Work?


A Lancashire Boiler is the best example of a Fire tube Boiler, why? Because the hot flue gas passes through the tubes, which are surrounded by water. As fire is present inside the tube, hence it is called so. In this article, we will cover the parts, accessories, applications, specifications, working principles, advantages, and disadvantages of a Lancashire Boiler.

What is a Lancashire Boiler

In a Lancashire Boiler, the boiler shell is placed horizontally, so it is called a horizontal boiler. Due to the bulky structure, this is also considered a stationary boiler. As the combustion chamber is present inside this boiler, it is called an internally fired boiler. Apart from that, these boilers are low-pressure boilers normally used in the small-scale industry.

The most interesting features of these boilers are it has two large tubes inside them, so it is also a multi-tubular boiler. Here the working pressure and power required are moderate. In this type of boiler water is circulated by natural processes that are produced by the application of heat (not by any external mechanical device like a centrifugal pump), so this is also a naturally circulated boiler.

Lancashire Boiler Diagram


Different Part of Lancashire Boiler

The important parts and components of this boiler are classified into two types which are given below.

Mounting of Lancashire Boiler

Boiler mountings are pre-installed safety devices for which they work smoothly.

  • Grate: It is like a base-like structure in the combustion chamber, where the fuel (solid fuel e.g. coal) is burnt and it is made up of cast iron. There is some space between them so that the air can pass through them. The surface area of the grate where fire takes place is called a grate surface.
  • Manhole: It is provided for inspection, cleaning, and repair of the interior of the Lancashire boiler shell. But the question is why it is named so? Because through this hole, a man entered into this boiler, and he could easily inspect, clean, and repair the integral defects.
  • Damper: This is present at the end of each side of a Lancashire Boiler, to control the flow of hot gases.
  • Fire Bridge: This is provided to deflect the flue gases upward and to prevent the entry of burning coal and ash into the interior parts of the fire tubes of this boiler.
  • Safety Valve: The safety valve is the most important part of Lancashire Boiler fittings. It protects life and property. It prevents explosion due to the excessive internal pressure of steam. It is designed in such a way that it opens automatically to pressure inside the boiler from increasing beyond the safe operating limit. Generally, these are directly mounted on the boiler (in the top portion but in some cases it is located in the front part of a boiler).
  • Pressure Gauge: This indicates the pressure of steam in a Lancashire boiler. It is mounted on the top portion of this boiler. The main purpose of this device is to monitor pressure. Normally Bourdon-type pressure gauge is used in a steam boiler.
  • Feed Check valve: This is the non-return valve which is placed at the end of the delivery pipe of the feedwater pump. It is mounted on a boiler shell slightly below normal water level. The primary function of this valve is that it permits the unidirectional flow of water from the feed pump to the boiler shell.
  • Water Level Indicator: This is an important part of Lancashire Boiler fittings that indicates the level of water in the boiler constantly to an observer. We can say that it is a safety device upon which the correct working of the boiler depends. The lower end of this indicator dipped in water and the upper end with the steam in the boiler. These fittings may be seen In front of the boiler. In case of need, if the water level falls down, water will be pumped by the operator. It is mostly employed in the steam boiler.
  • Blow-off Cock: This is used for periodical cleaning by releasing the mud water and sediments from the bottom of this boiler. Also, it reduces the corrosion property of the material of the boiler shell. This is also used for emptying the boiler whenever the boiler is not in operation.
  • Steam Stop Valve: The main function of the steam stop valve is to shut off or regulate the flow of steam from the Lancashire boiler to the steam pipe or from the steam pipe to the engine respectively. The main body of the steam stop valve is made up of cast steel. The valve and nuts are made up of Brass.

Accessories of Lancashire Boiler

The accessories of this boiler are used to increase its efficiency and are listed below.

  • Air Preheater: In simple words, we can say that this mechanical device recovers the heat from the boiler’s hot flue gas which is exhausted out through the chimney. It means there is no heat loss. In this way, the efficiency of the Lancashire Boiler increases.
  • Economizer: This is nothing but a heat exchanger that is placed in the exhaust area of a Lancashire Boiler to produce saturated steam or moist/wet steam. Also, it raises the temperature of the boiler feedwater, lowering the energy input, and reducing the firing rates needed for the boiler output.
  • Superheater: The main purpose of the superheater is to increase the temperature of saturated steam without raising its pressure. The Lancashire boiler utilizes both sensible heat as well as latent heat to convert water into steam while the superheater utilizes only sensible heat to superheat the steam in order to increase its enthalpy and thermal efficiency of the boiler.

Application of Lancashire Boiler

Generally, these boilers are used in the following industries that are given below.

  • Sugar Mills
  • Paper Mills
  • Textile Industry
  • Chemical Industry
  • Tyre Industry
  • Breweries Industry
  • This boiler is also used in the Locomotive and Marine Industries. It is also used to drive the Steam Turbine.

Specification of Lancashire Boiler

These data may slightly vary according to the Boiler Manufacturing Companies.

  • The diameter of the boiler shell ranges from 1.74 to 2.75 m.
  • The length of the boiler shell ranges from 7.25 to 9 m
  • The operating/working pressure ranges from 7 to 16 bar (maximum)
  • The steam generation capacity- 8500 Kg/h
  • The boiler tube diameter (external) – 6.25 cm
  • The slop of boiler shell- 1: 250
  • The overall efficiency of a Lancashire Boiler- 80 -90%

Working of Lancashire Boiler

This boiler consists of a horizontal cylindrical shell filled with water surrounding two large fire tubes. The cylindrical shell is placed over Brickwork which creates several channels for the flow of hot flue gases. The solid fuel e.g. coal is provided through the fire door which is burnt over the grate at the front end of each fire tube. A small Brick Arch is provided at the end of the grate. Why? Because it deflects the flue gases upward and prevents the entry of burning coal and ash into the interior parts of the fire tubes.

If we look closer to the Boiler then we can see that it is a conical shape at the rear end which increases the velocity of the hot flue gases. Then the flue gases are allowed to move downward channel towards the front end of the fire tube to discharge into the atmosphere through the chimney. There are Dampers at the end of each side channel to control the flow of hot gases and regulate the combustion rate and steam generation rate.

The feed check valve is used to feed water uniformly to the boiler Shell. When the boiler is heated adequately water is converted into steam by absorbing the heat from the surface of the flue tube. Now this steam is stored in the upper portion of the boiler shell, where the Anti-priming pipe separates water from the steam and the Steam stop valve receives the dry steam for various purposes.

Advantage of Lancashire Boiler

The advantages of a Lancashire boiler are given below.

  • The construction of this boiler is very simple and cost-effective.
  • It can generate a large amount of heat because it has a larger heating surface area.
  • The consumption of electricity is less, as this is a naturally circulated boiler.
  • The heating surface area per unit volume of the boiler is large.
  • The inspection and maintenance of this boiler are very easy.
  • The fluctuation in load can be met easily by this boiler due to a large reservoir.
  • An operator can easily operate this boiler.

Disadvantage of Lancashire Boiler

The disadvantages of a Lancashire boiler are given below.

  • Generally, it requires a large area due to its bulky structure and brickwork.
  • It required more time to generate steam because of two larger tubes.
  • It can’t be used in Large-scale industries, as it is a low-pressure boiler.
  • The response to pressure build-up in this boiler is less.
  • It has a small steam generation rate.
  • The chances of leakage are higher in the joint section.
  • Due to the smaller number of tubes, the amount of heat loss is high, which passes through the chimney.

This is all about “Lancashire Boiler“. Thanks for giving your valuable time. If you have any doubts related to this boiler please don’t hesitate, to ask in the comments section below. If you have any prior experience related to this boiler and know more about it, please share it with us. We promise that we will solve your doubts as soon as possible. And if you really like this article, don’t forget to share it with your colleagues and friends. Good Luck.

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