10th May 2024

Demolition Chief Lifts Lid on Precision Engineering Required in Removing the Last of Redcar Blast Furnace

Removing the remains of a Teesside icon is no easy feat – particularly when it weighs thousands of tonnes. Robyn Rushforth is at the helm of the firm tasked with removing the final remnants of the Redcar Blast Furnace. He explains how science, precision engineering and decades of knowledge will go into safely breaking down the remaining blast furnace iron.

At its peak, the Redcar Blast Furnace produced 10,000 tonnes of iron a day and employed hundreds of people.

Its final blowdown after a brief re-dawn marked a sad moment for Teesside in 2015.

And its successful demolition in late 2022 and subsequent clearance was bittersweet.

A new dawn at the site is now emerging via Teesworks and the bp-led Net Zero Teesside project and Net Zero Teesside Power to sit on land a stone’s throw from where the blast furnace once roared.

However, there is still some work to be done.

When the gargantuan task of ensuring the Blast Furnace was safely blown down was completed in quick time, work afterwards to mothball the furnace with what is known as a “salamander tap” wasn’t carried out.

This tap would have drained the last liquid iron from the furnace hearth.

Instead, a great lump of huge weight cooled and solidified. It remains in place almost nine years later.

Robyn Rushforth, and his firm Precision Demolition Ltd, working in conjunction with Thompsons of Prudhoe have been tasked with working out how to remove these final remains – as well as some of the towering ladle pots still sitting among what if left of the Lackenby BOS plant.

A technique called thermal lancing – where workers wrapped in metal protective suits would bore holes in iron – was the past method used to demolish and remove remnant blast furnaces.

“You’d get a lot of sparks and a lot of brown smoke from the various oxides of nitrogen – there were environmental issues and improvement in how we manage health and safety make this unacceptable now,” explained Robyn.

Large holes created in the iron were then filled with explosives and the iron was ripped apart in a “crude and uncontrolled” fashion.

Precision Demolition will use extremely precise charges tested on material and minutely shaped to break down the ladle pots and what is left of the Blast Furnace.

Robyn said: “We’re going to fire these shaped charges to make holes in the big Iron ingots – where we have a bit of an unknown is these charges have been tested in military applications to show they will punch through a certain amount of steel armour plate.

“What we don’t know is how much harder the armour plate is than the iron, and also once these things have punched through, how much energy they’ve got left.

“This is where we’re on completely new ground.”

A testing regime with trials will help determine precisely how deep the existing charges will penetrate the iron.

Depending on the results, either these off the shelf charges will be utilised or bespoke charges developed to make the necessary holes.

Robyn added: “There is science which goes into this, and very complex modelling software used in the explosives industry to predict what the charges will do.

“But we are on new ground – and when you’re computer modelling, you’re looking at previous results and extrapolating a design into that.

“I don’t want people to think we’re making it up as we go along, but this is what research and development is all about. It determines precisely what we can achieve.”

Shaped charges are very precise pieces of equipment. The ones planned to be used are about 80mm in diameter and feature a copper cone. Explosive sits behind the cone – and when fired, the copper cone inverts into a jet of copper which punches a hole in the iron ingot.

The metallurgy of the copper, distance from the target material, the type of explosive behind it and the way it’s filled are all variables the team must take into consideration to ensure a successful demolition.

“By doing the trials work, we will find out what depth and diameter hole we can create and the volume of explosives we can get in it,” explained Robyn.

“When we move forward into the doing of the job, the idea is we will fire multiple explosive shaped charges to make a series of holes that are relatively close together.

“We will then fill those holes with explosive and we are hoping to use a liquid explosive to get maximum weight of charge which will run into all the nooks and crannies.”

Beyond the forces generated by the ignition of the explosives themselves, the crucial aid to the demolition work is the interaction and effect by the shockwaves generated.

Robyn added: “You get a shockwave, the shockwaves hit one another, create tensile forces which then pull and break the iron.

“You’re working using the colliding shockwaves – we’re not just using expanding gas to push the metal away. We’re creating a shockwave and a shatter effect.

“It’s what is done in quarries – that’s why blasting in quarries creates a pile of really small stones, rather than a big mound of boulders.”

Mr Rushforth has more than 30 years of experience in explosive demolition.

He began his career at the Royal Ordnance Factories, in Waltham Abbey – the home of gunpowder production in England since the 17th Century.

After serving his apprenticeship as the Royal Ordnance morphed to BAE Systems, and studying linear shaped charges, Robyn moved into civil demolition.

He added: “I worked from a variety of companies between 1989 and 2007 – when I made the break and decided to focus exclusively on explosive demolition.

“I joined in a partnership with a very experienced structural and explosives engineer. He subsequently retired and I now own and run PDC.”

His career has seen him bring down gas holders, power stations, chimneys and boilers – with Precision Demolition taking on jobs during the Teesworks demolition programme.

He added: “It’s interesting because it’s all very well someone giving you a drawing showing you how something was built, but how something is now after being modified over the years, or stood derelict for seven years with a salty sea breeze corroding it, is often very different.

“Normally, when we’re working on structures, there’s been a winding down or shutting down, whereas an awful lot just stopped at the former steelworks.

“Things could have been done differently but they weren’t – that presents a unique set of problems – and unique solutions to solve those problems.

“The science which goes into this is something constantly being developed.”

Robyn has data sets running back to demolition in the 1970s. It’s this rich seam of information on pressure and distances which helps inform modern day modelling and the shaping of charges for demolition.

He added: “Sometimes you’re going beyond the data batch you have available at the moment. We’re trying to expand that data and move into the realms we’re not absolutely sure about to substantiate the model and build on it.

“We’re pushing the learning a little bit more – we’re looking at using existing charges in a different manner, and potentially enhancing them by changing their geometry or filling material.”

The demolition of the ladle pots and remains of the blast furnace will take place in the coming months.

Martin Corney, Teesworks CEO, said: “The Teesworks demolition programme has been one of the largest the UK has ever seen – and it’s been a true team effort from start to finish.

“The original masterplan envisaged it would take at least five years to complete the programme. The explosive programme was done in two years, and this has saved the taxpayer millions of pounds.

“The demolition of the blast furnace brought mixed emotions in all of us, but the expertise provided here and across the site is paving the way for us to breathe new life into Teesworks bring in the dawn of a new era.

“The programme has opened the door to us remediating hundreds of acres of land and has helped us bring more good jobs through new green energy projects ever closer.”

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