Our steam engine is the largest of its kind possibly in the world and represents the final stage of steam power in mills. It is certainly the last steam engine to power a mill during the last miners strike.
It is a twin, horizontal cross compound engine of 2,200 horse power and was manufactured by Yates & Thom of Blackburn in 1923.
The large flywheel or 'rope pulley' in the middle of the engine was connected to smaller rope pulleys in the 'rope race' which in turn, drove shafts on each floor of the mill to run the machinery. This mill also generated it's own electricity.
You can see more pictures of our Engine and where it lives in the Gallery.
Starting the Engine
A Barring Engine is used to turn the Main Engine into it's starting position.
This is where both cranks are in an upright position so that their weight assists the engine to start as the steam valve is opened.
The main engine then takes over and the Barring Engine disengages.
Unfortunately, at present our Barring Engine is away from the mill, being repaired and refurbished. On it's return, we will have some fresh photography of it and hopefully a video of it performing it's job.
HOW OUR STEAM ENGINE WORKS
Stage One - Generate the steam...
A Lancashire boiler is a horizontal, internally fired tube boiler. This boiler can raise steam up to a pressure of 180psi and has a maximum evapourating capacity of 8,500Kg of steam per hour.
This boiler works on the basic principle of heat exchange. It is basically a shell and tube type heat exchanger in which the flue gases flow through the tubes and the water flows through the shell.
The heat is transferred from flu gasses to the water through convection. It is a natural circulation boiler which uses natural current to flow the water inside the boiler.
Flue gases from the grate pass through the boiler tube, along the bottom flue and then up and along the side flues, keeping superheated gases in contact with the boiler for the longest time possible to
extract as much heat into the boiler, then they move into the economiser before finally emerging into the atmosphere via the chimney.
Leigh Spinners had 7 boilers, five in service and two on standby or in maintenance. They consumed nearly 200 tons of coal a week, raising enough steam to power the whole mill.
You can learn more about Lancashire Boilers here.
Stage Two - Improve the economy of the boilers...
If you remember from the boiler description above, the hot waste gases travel towards the chimney but there's still heat in the gas that can be used to improve the economy of the boilers.
This last bit of energy was recovered using an item similar to the picture opposite, the Economiser. These were the size of a large room and consisted of dozens, even hundreds of tubes that are kept
clear of soot and debris by a system of automated scrapers.
Some of the water from the bottom of the Air pumps is fed into the economiser via the pipe labelled "A", bottom right. It then travels up the vertical water tubes into pipe "B", being heated by the
passing hot flue gases as it moves, this heating the water to as close as boiler temperature as possible.
From here it is pumped into the boilers to replace the water that is boiled off in the production of steam.
This does a few things but most importantly, it saves coal as the boilers don't have to heat the water from cold and it also prevents thermal shock to the boilers that could cause them to fail prematurely.
You can learn more about Economisers here.
Stage Three - The Cylinders...
You will have noticed that our engine has two cylinders which are the same in design but one is larger than the other. The smaller of the two is the "HP" or High Pressure cyliner and the larger is
the "LP" or Low Pressure cylinder. They are connected by a large diameter pipe underneath the engine.
Steam leaves the boiler under 180psi pressure and enters the HP in the top left. This forces the piston along the cylinder, expanding as it goes. You can see in the image that the valve bottom right is
also open and this enables the cylinder to exhaust steam from behind the piston.
As the piston reaches the right hand end, the exhaust valve closes as does the left hand inlet valve. At almost the same time, the opposite two valves open, allowing the piston to be driven back
along the cylinder with steam entering the top right and exhausting leaving the bottom left to start the cycle all over again.
The exhausted now lower pressure steam at 60psi travels under the floor of the engine house into the LP cylinder to exactly the same job. Now hered's the clever bit. The reason the LP cylinder
is bigger is so that the lower pressure steam can exert the same amount of force over the LP piston as it did on the HP piston.
You can learn more about HP & LP Cylinders here.
Stage Four - Condenser & Air pumps...
The now depleted steam still has work to do as it leaves the LP cylinder. It travels to the Condenser.
As the steam enters the condenser, it meets a jet of cold water drawn into the system from the cold lodge outside. This instantly collapses the steam back into a liquid.
When water is converted into steam it expands roughly 1,600 times. Imagine an egg cup of water filling a mediam sized van with steam! When it's condensed it has the exact opposite effect, creating
a huge vacuum in it's place. The resulting vacuum is used to suck out any remainging steam from the LP cylinder and also sucks the piston in the opposite direction again, generating even more power
to drive the mill.
As you can imagine, we now have a lot of water with nowhere to go, this is where the Air pump comes in.
These pumps are driven by the engine and draw off the waste water and left over "air" from the collapsed steam in the condenser, maintaining the vacuum and returning the water back to the mill lodge
to cool before being drawn back into the condensers to complete another cycle.
You can learn more about Steam Condensers here.
The history of the steam engine stretches back as far as the first century AD; the first recorded rudimentary steam engine being the Aeolipile described by Greek mathematician Hero of Alexandria.
The first commercial steam-powered device was a water pump, developed in 1698 by Thomas Savery. It received some use in mines, pumping stations and for supplying water wheels used to power textile machinery.
The first commercially successful engine, that could generate power and transmit it to a machine, was the atmospheric engine, invented by Thomas Newcomen around 1712. It was employed for draining mine workings.
The next major step occurred when James Watt developed (1763–1775) an improved version of Newcomen’s engine, with a separate condenser. Boulton and Watt‘s early engines used half as much coal as John Smeaton‘s improved version of Newcomen’s.
Watt proceeded to develop his engine further. This enabled factories to be sited away from rivers, and further accelerated the pace of the Industrial Revolution.
Watt’s patent prevented others from making high pressure and compound engine. In 1800, Richard Trevithick and separately, Oliver Evans in 1801 introduced engines using high-pressure steam. These were much more powerful and could be made small enough for transport applications. Trevithick’s Cornish engines were used in mines and for water supply until the late 19th century.