Hudson's Patent Boiler Hudson's Patent Boiler

Boilermaking: a Forgotten Industry

5 min read

The Thomas Hudson and Company Collection

Boilermaking is an under-appreciated branch of engineering but was essential for the Industrial Revolution to happen. Boilers supplied steam to drive the engines that freed-up industry from the need for water power. This meant that an industrialist wanting to build a factory didn’t have to worry about finding a strong enough river to power their machinery.


What is a boiler?

Boilers make steam by heating water in a sealed vessel. When water is turned to steam it expands by more than 1,000 times. This pressure of steam can be used to drive the pistons of a steam engine.

The most common fuel in boilers up until the early 1900s was coal. Later boilers might be fuelled by oil or gas.


There are two main types of boiler

In a fire-tube boiler, the whole vessel is filled with a volume of water that is penetrated by a series of tubes carrying hot gases from the fire. This is the most common type of boiler used to power steam engines;

The water-tube boiler on the other hand has tubes containing the water to be turned to steam.

Improvements in Technology

Steam power was first introduced to Scotland in 1719 with the first Newcomen atmospheric engine north of the border. You can still see its ruined engine house near Saltcoats. A later example of a Newcomen engine is on display in the colliery at Summerlee Museum, where it is on loan from Glasgow Museums. Early boilers were simply metal containers filled with water that were positioned over a hearth.

Innovations in steam technology such as those made by James Watt and Richard Trevithick made increasing demands on boilermakers as higher and higher pressure steam was needed. If the casing of a boiler failed the consequences could be literally explosive.

The earliest steam engines ran on relatively low-pressure steam but by the early 1800s improvements in engineering meant that engines could be run at much higher pressures. High pressure steam engines were pioneered by Richard Trevithick, who built the first steam locomotive. Boilers were needed to supply the steam, and lots of it!

The construction of the Vulcan, Scotland’s first iron boat at Faskine in 1819 shows how skilled Lanarkshire’s boilermakers were, even at that early date. The plates for the Vulcan were rolled at the Calderbank Forge and the boat’s construction mirrors the way boilers were built.

One early form of boiler, used widely in the mid-1800s was the ‘egg-ended boiler’. This was a long horizontal tube with domed ends. The boiler contained water and was mounted on a brick structure containing a firebox and flue that heated the water to produce steam. There is an egg-ended boiler on display at Summerlee Museum: it was found at the works of Thomas Hudson and Co, Coatbridge, where it was being used as a water tank.

As the nineteenth century wore on boilers became more sophisticated. The firebox and flues which previously had been outside the boiler itself began to be incorporated inside the boiler shell. The Cornish Boiler of the early 1800s had a single flue running through it, before the Scot William Fairbairn invented the Lancashire Boiler with two flues in 1844. Later boilers were called ‘multi-flue’ boilers because they directed the hot gases from the furnace through lots of narrow tubes inside the boiler.


Thomas Hudson and Company, a North Lanarkshire Boilermaker

Early boilers were made by blacksmiths but as time went on firms began to specialise in making boilers. One such company was Thomas Hudson and Co of the Sheepford Boiler Works, Coatdyke. They made boilers and girders.

Thomas Hudson came from Kilsyth and founded the company in 1870. Their customers were not just in Scotland, for example they supplied boilers to jute mills in India.


The firm largely stopped making boilers around the end of the First World War but the firm was able to keep going by making perforated plates for coal mine and quarry screens. They mainly sold to National Coal Board areas in Scotland and the north of England. Hudson’s also made dished ends for water tanks. Thomas Hudson died in 1928 but the firm kept going until the 1980s when the closure of most of the remaining coal mines meant there was no longer a market for perforated plates.

Hudson’s is probably unique in that not only has the company archive been preserved but the museum service has a nationally important collection of boiler-making machine tools, largely from when the works was re-equipped in about 1890. This collection is probably unique in the UK.

The collection of machine- and hand-tools is preserved at Summerlee Museum in Coatbridge while the company archive is held by North Lanarkshire Archives at North Lanarkshire Heritage Centre in Motherwell.


How a Boiler was Made at the Sheepford Boiler Works

Cutting and shaping boiler plates

The characteristic curved iron or steel plates of a boiler were made from flat plates that had to be cut to size before being bent into a curve.

Finishing the plate edges

The edges of the boiler plates needed to fit snugly together, whether they were joined with an overlap or the ends butted together. Curving the plates would leave a gap between them unless the edges of the plates were given an angle. It was crucial that the pressure inside the boiler was taken by the plates themselves and not by the rivets so the finishing of the plate edges was very important. This was the job of the plate edge planer.


Bending the plate

It needed a lot of force to bend the boiler plates. This was done by running them though a set of bending rolls. The plate would be heated and run backwards and forwards through the rolls, the angle being changed a little at a time. The plate could be rolled either horizontally or vertically.


Plates or tubes could be fitted together more easily if a lip, or ‘flange’ was put into the edge. This was most easily done by putting the plate into a press which squeezed it onto a ‘die’ that was made to the shape the plate was to become. This forced the plate into the same shape.

Thomas Hudson and Co had a huge hydraulic press in their Sheepford Boiler Works but sadly it was too big and heavy for the museum to rescue.


Making holes for the rivets

The boiler plates would be joined together by rivets that were inserted into holes pre-made in the boiler plates. The holes could be made by either drilling or punching. Drilling was better because there was less risk of weakening the plate.

After the Second World War welding was good enough to replace rivets but by then Hudson’s had long since stopped making boilers.


Riveting the plates together

Rivets were used to join the boiler plates together. Unlike a bolt a rivet is permanent fixing and once it has been fitted can only be removed by destroying the rivet. The rivet consists of a shaft with a head at one end. The shaft is heated up and inserted in ready-prepared holes in the plates to be joined together and the protruding tail end is then hammered flat so that the shaft cannot be withdrawn again. As the rivet cools it contracts, making the join tight.




The kind of boilers that Hudson’s made had quite a simple internal construction. The water was heated by two or three flues running the length of the boiler. These had to be made separately and then inserted into the boiler shell. The flues were supported inside the boiler by rods called ‘boiler stays’.



The boiler would have fittings, usually made of brass fixed the outside. These included valves, inlet and outlet pipes and gauges to show the steam pressure and water levels in the boiler.


Here Robert Adam, the last owner of the company recalls his only meeting with Thomas Hudson

Robert Adam describes some of the firm’s customers

John Finnegan describes how a boiler shell was shaped using plate bending rolls at the Lilybank Boiler Works in Glasgow.  Mr Finnegan worked there after JM Connell in Coatbridge closed down.

Former engineer Daniel Mackay explains how the boiler shell was drilled for riveting.

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