22 Feb Building the Bessemer Converter
Back in the 19th Century, bridges, buildings and any structural work could only be made with wrought or cast iron. Almost any machinery parts could only be made from cast iron too. The world was waiting for an alternative. Steel offered the solution, but the methods available for processing iron to steel were time-consuming, very expensive and only produced tiny quantities of steel. And then along came Henry Bessemer.
Born in 1813 in Charlton in Bedfordshire and the son of the owner of a small engineering business that made iron bars and girders, young Henry became convinced that there could be a more efficient way to convert iron to steel. His major discovery was that unwanted materials were removed, not by the heat of the fire, but by being absorbed into the oxygen in the air. The hotter you could get the pot, the easier it was to keep the iron as a liquid and the easier it was to remove the impurities.
His huge breakthrough came when he invented a vessel, that he later described as a converter which had an open top and allowed you to force air in through the bottom. The vessel was filled with molten iron and air pushed through it to chemically react with the unwanted materials. This drove the carbon out of the iron and allowed the waste slag to be easily removed from the top of the liquid. The flames from the top of the converter reached as high as 10 metres and the steelmaker knew that when the flames died down, the conversion was complete. All of this alchemy happened without the use of additional fuel, so was incredibly efficient and cost effective.
How the Bessemer Conversion Process Works
- Charging – The Converter is filled with molten Pig Iron from another furnace.
- The Blow – The converter is now turned to the upright position and air is forced up through the molten iron causing all of the unwanted materials to be burned off, creating pure steel.
- Tapping – The converter is now tipped back to its original position and the steel is poured firstly into a ladle and then into the different sized ingots.
The Bessemer Efficiency
The completed converter could make 30 tons of raw steel in 30 minutes and brought the market price for steel down from £80 per ton to nearer £10 per ton. Steel was suddenly a viable material for building and machinery.
The technology was still used throughout the world until the last ‘blow’ back in 1974 when the last remaining Bessemer Converter was transferred to the Kelham Island Museum where it still stands today. Along with Sir Richard Arkwright, Sir Henry Bessemer, who was knighted in 1879, was perhaps the unsung hero of the Industrial Revolution and not only did he revolutionise steel production in the UK, he also allowed Japan to build their own industrial revolution too.
1993, enter stage left, a Japanese museum, who wanted a model of the Bessemer Converter to take pride of place in their new industrial display. The brief was that it had to be built using technology available in the day and with methods and materials available to the teams of the 1850’s. Enter stage right, Garmendale tasked with building a quarter scale model of the original Bessemer Converter. rest assured, the team at Garmendale, absolutely love this type of challenge. Three months later the project was complete and we kept a mini-diary of how the project went.
So, here’s the build of our own model for our Japanese customer from start to finish.
When we look back at all of the rides, models, and unusual engineering challenges that Garmendale have taken on and won over the years, we look back at the Bessemer Converter as one of our favourites and a turning point in our business confidence. We were one of the few people who could have taken the build on and we delivered.
Garmendale Engineering have been designing, manufacturing, maintaining and refurbishing rides, trains, and gating systems in theme parks and attractions across the world since 1982.