Mary, Bess, Anne and Vic. Steelmen the world over know their names.

The naming of blast furnaces is a comparative rarity, in fact. The Appleby-Frodingham ironworks in the north Lincolnshire town of Scunthorpe is an exceptional place in other ways too, since this is where the sintering of iron ore was perfected. The eastern skyline of the town is dominated by the Four Queens, in their iconic file.

The first two furnaces at the northern end of the site date from 1939. When the third and fourth were added in 1954, this elder pair became Mary and Bess. Victoria was and is the southernmost, rising with Anne from a common cast-house structure. These two are the biggest. Operating at her full capacity, Vicky can produce over a million tonnes of liquid iron in a year.

There is no workplace on earth quite like the cast-house of a blast furnace. Thirty miles west of here, the claustrophobic blackness of the coalpit was familiar to thousands. Thirty miles to the east, the trawlermen set out to dare the lashing grey hell of wintry seas. Here between, the hell-pit is almost literal.

It’s the 4th of November, 1975. The time is just after one in the morning.

Hot Metal

Few people guess what molten iron is like. They expect something like the familiar depiction of lava, angry red and viscous. In reality, the metal is a blistering yellow-white, too bright to look at. And it flows with the mobility of water, only with seven times the density.

When the tap-hole is opened, it streams down the runner and thunders into the ladle below with an energy that demands respect.

01.05 am

Below the cast-house floor, the diesel loco and its two torpedo ladles draw into position.

Torpedos are a comparatively recent development at Scunthorpe. They were introduced just over two years ago, as part of the Anchor project that built Europe’s biggest basic oxygen melting shop, three kilometres away down the line. Before then, iron was shipped in bucket-like Jumbo ladles, open-topped and as high as they were wide.

The torpedo is instead a horizontal contraption, with about the size and aspect ratio of a railway carriage. It’s a thick-walled refractory-lined cylinder, capable of holding 250 tonnes of liquid iron. The iron is poured in through a narrow aperture in the centre at the top. This port, less than a metre diameter, is the only opening, a feature designed to conserve heat.

The runner spout is set in position by crane.

It needs a crane, since the spout weighs nearly a tonne. In a few minutes time when the cast begins, molten iron will rush down the channel known as the runner and the spout will direct it into the torpedo mouth.

Vicky is in her seventh campaign since her original blowing in. After three years of operation or so, the lining of a blast furnace needs to be replaced, and the furnace is taken out of use for several months to carry out this work. The latest campaign began in May 1974, and the condition of the furnace is generally good, except that there has been a spate of cooling water leaks in recent weeks.

Blast furnaces need a lot of cooling, and not only to the casing itself. The air-blast that drives combustion is preheated to around 1000 degrees C using stoves, and enters the furnace via a girth-ring of around thirty large nozzles called tuyeres. The tuyeres incorporate cast copper cooling jackets and each one is fed with pressurised water at around ten litres per second flow. In two weeks during September there had been half a dozen tuyere cooler failures, probably exacerbated by a recently-adopted maintenance practice of replacing worn copper blanking plugs with steel ones.

There are no signs of leaks on this shift, however.

The tap hole drill is moved into position, in readiness to begin the cast.

Water and Iron

It’s well known by painful experience that these two do not mix. The degree of danger, though, is strongly dependent on which phase is on top. If liquid iron is poured onto water, or even on to a wet surface, the chilling effect can lead to the formation of a solidified crust under which pressure builds as the water flashes off to steam. The crust may then fail explosively, flinging out hot metal.

Water on top or iron is not so dangerous, because the steam is not then entrapped. Water spraying can be safely used for the cooling of cast iron pigs, for example, in order to induce their solidification. Even if there is a water leak during casting from a blast furnace, therefore, and even if a large flow of water enters the runner, then the explosion risk will be minimal once the iron stream has been staunched. Any water pouring onto the top of a partly filled ladle will flash off.

There is a problem with this piece of empirical knowledge, though. It has been proved on the old, open-top ladle type. It has never yet been tested through a high water flow into a laden torpedo.

01.25 am

The cast begins without any problems. Iron begins to build up in the first torpedo.

How a Blast Furnace Works

The blast furnace converts iron ore (comprising various phases of iron oxide) into liquid iron, at the same time separating out silaceous material and other impurities in a slag. The furnace consists of a cylinder some twenty to thirty metres in height, flaring out to a maximum diameter just above the tuyere level and narrowing in again to a hearth which collects the molten iron at the base. The furnace is charged at the top with a mixture of pulverised ore, coke and flux (commonly dolomitic limestone). These components of the burden have usually been combined and roasted in order to fuse them into a permeable sinter.

The reduction reaction and the melting of the iron require high temperatures, with the coke providing both the fuel for combustion and the reducing agent. Liquid iron descends through the burden and collects in the hearth, where it is typically drawn off at intervals of about six hours by breaking out a clay-plugged taphole. A liquid slag of lower density floats on the iron, containing much of the silicon, phosphorus and sulphur present in the original ore. Traces of these elements, as well as an excess of carbon, remain in solution in the iron, but can be brought to controlled levels in refining at the steelplant. The slag is tapped off at intervals through notches above the taphole.

The typical tapping temperature is around 1600 degrees C. Only the tapping is periodic: the charging process is continuous, and once stopped cannot be restarted without costly repair and months of lost production. Allowing the iron to solidify, or chilling to occur to a degree that encourages concretion on the walls, is economically catastrophic. For this reason, the air-blast that maintains combustion is suspended only with reluctance and then only for short periods, and fine judgement between protecting the asset and avoidance of accident is sometimes needed.

02.00 am

The first ladle is full with some 175 tonnes of iron. The iron notch is isolated while the loco pulls forward to present the second torpedo, and the metal flow is restored. Everything remains normal around the furnace. The loco is decoupled and moves to an adjacent furnace to shuttle more ladles.

Flixborough

Until eighteenth months ago, the Borough of Scunthorpe had an exemplary industrial safety record, in spite of there being several highly energetic and potentially explosive plants within its boundaries. The copybook was blotted by what was then Britain’s most expensive ever accident, at Nypro’s Flixborough plant some seven miles away on the Trent bank, on 1st June, 1974. Designed to manufacture caprolactam for processing into nylon, the plant’s safety was compromised by a jury-rigged main temporarily joining two reactor vessels. The resulting blast killed 28 men, flattened surrounding houses and set a fire that burned for ten days.

The letters of congratulation to the town council, sent to mark the inception of the new Health and Safety Executive just three months previously, didn’t read so well after that. Now Scunthorpe’s record was about to switch from one of the safest industrial towns in Britain to the most blighted.

02.15 am

An alarm has sounded in the cast-house control cabin, indicating excessive heating somewhere among the exterior equipment of the furnace. An inspection identifies a burndown in the blowpipe of the No.3 tuyere, the pipework that directs the pressurised and preheated air from the stoves to the tuyere itself. Flames are soon visible in the area and a crack opens, allowing a jet of hot blast air to escape. It plays tangentially along the furnace wall, and projects a shower of debris some five metres forward of the furnace. Without the pressure of the blast to contain it, material from within the furnace is forced back through the tuyere by the weight of the burden, where it is drawn into the jet and sprays out like the paint from an airbrush.

This is a dangerous situation, but not a critical one. The foreman gives the instruction to reduce the blast pressure. The furnace keeper attempts to play a hose onto the damaged pipe, with the intent of freezing the leaking debris and effecting a temporary seal. Getting close to such a leak is far too dangerous to be risked, however, since the escaping jet could change direction in a moment and would incinerate anyone in its path. The burndown worsens, and a cooler leak on the adjacent No.2 tuyere is detected. Now the furnace is going to have to come off blast altogether to replace the damaged tuyere stocks, and completing the cast and removing as much molten metal and slag from the furnace as possible becomes a matter of necessity and expediency.

Birmingham University

He woke in the night and knew he’d heard a bang. They were common enough from the direction of the steelworks, whenever slag was tipped onto wet ground. This must have been a big one, since sleep disturbance was usually confined to the summer months with the bedroom windows open. Or maybe he was sleeping fitfully anyway, in anticipation of tomorrow’s interview. A few hours later, he was on an early train, lost in thought and oblivious to any news that might have been breaking at that hour.

It was his very first university interview, at Birmingham where he hoped to study physics. It went well enough, but at the end the Head of Department asked a question in hushed tones. He’d noted that the candidate was to be sponsored by British Steel, and that the resume described work experience on the Scunthorpe ironworks. The young man hadn’t heard the news, but his reaction to it was one of shock. The academic, now very grave, invited him to use the telephone and stepped discreetly from the room.

02.30 am

The ironworks shift manager is now in the cast-house and takes control of the recovery from the emergency. There is a persistent and unquantifiable flow of water from the No.2 tuyere cooler passing down the runner and away over the spout. Steam is copious and is filling the void below the floor where the ladles are.

There is no cause for panic. Situations like this, though not frequent, are within the experience of every member of the furnace crew and just have to be negotiated carefully, without undue risk to the safety of the men. Things are under control, but there is no safe approach to the iron notch area, so the taphole cannot be sealed. Fortunately, the natural end of the cast is approaching.

The pressure in the bustle main is now low enough for the whole furnace to be taken off-blast. The foreman telephones traffic control to return the loco.

Queens’ Approach

The memorial plaque was made, of course, of iron from the Queen Victoria furnace. You can see it up there on Prospect Avenue, still diligently cleaned, and lit at all times. There is dignity and calm in this place, a haven amid what will always be a truly terrible environment. The towering furnaces, and the tempest of energy they contain, might once have distracted us from the humanity of the enterprise. We might have overlooked the men like us who work here, but never after this.

02.45 am

The furnace has been successfully brought off-blast, and the flow of iron in the runner has all but ceased. A sense of relief begins to return because the danger is now receding, but there is still work to be done, and fast. Men are preparing to effect repairs to the damaged tuyere stocks even as the shunter below kicks out the wooden scotches that chock the torpedo bogie in position on the rails.

The shunter returns to his cab, and acknowledges the signal to pull away. The couplings tighten. It is 2.47 am.

The Next Day

The loco and the ladles, all derailed, remain where they came to rest, some five metres away from the chocking position. The cast-house floor above has substantially disappeared, as have substantial parts of adjacent structures. The exterior cast-house wall has been demolished, and the windows of the control cabin have gone. The remaining floor area is strewn with fused slag and iron and broken bricks and glass.

The human debris has been removed, but in places there is still a boot or a glove. Everything is covered with a thin plating of iron. The smell is horrible.

I would have loved to have seen him, just to put my mind at ease, but there was nothing to identify. It was just a wallet and some keys.

The Inquiry

The statistics are simple.

Four men killed outright. Seven others died later in hospital as a result of their injuries.

Ninety tons of iron thrown from the ladle, some half of which entered the cast-house area.

The runner spout recovered from the cast-house roof.

In the confines of a torpedo ladle, water on the surface of molten iron is not safe after all. When applied in high volume over several minutes, a chilled crust forms atop the iron bath. Boiling is slowed by the insulating effects of this crust, and incoming water soon now fills the void above. If the ladle is moved, the crust may fracture, bringing a large volume of molten iron and water into sudden contact in a confined space. There is evidence in this case that water flowed under the still largely intact crust, and that steam pressure then lifted this crust to block the mouth and effectively seal the torpedo. A catastrophic escalation of pressure is believed to have ensued, with the crust finally bursting explosively a few seconds later.

The steel plug in the No.2 tuyere cooler was found to be badly corroded. It also underwent significantly different thermal expansion from the surrounding copper, when subjected to forced cooling through the attempts to contain the burndown at the No.3 position. For both these reasons, the original copper component would have stood a better chance of constraining the leak, perhaps to a degree that would have prevented the disaster. The inquiry recommended that the practice of replacement using steel plugs be suspended with immediate effect. It further proposed that some easily-actuated means of diverting water flow away from the torpedo mouth should be designed and implemented in the spout area.

Notwithstanding these recommendations, the direct cause of the accident was found to be the moving of the locomotive. There would probably have been no explosion if the torpedo had been left to freeze. The decisions taken by the men present were nonetheless rational and blameless. All their experience to that time suggested that the ladle could be safely moved away from the still-flowing water stream, and that leaving it in place was a more dangerous and ultimately very costly alternative.

The Queen Victoria Blast Furnace Disaster provides a telling case study for a particular kind of industrial hazard, and the inquiry report concludes with an observation that explains it. Wherever and whenever the introduction of new technology is considered, it's imperative that the established norms of operational safety are reviewed. A safe method for dealing with water in a Jumbo ladle turned out to be unsafe with the new torpedos. The risk could have been foreseen based on existing knowledge if the scenario had been analysed. A tragedy occurred because nobody realised the need to do so.

Eulogy

There were 23 men in the direct vicinity when the explosion occurred. I only knew a couple of them, and those just slightly, beforehand. One of these was an exact contemporary and had been a school football rival. He was the last to die.

Of the survivors, the number who were both able and minded to return to work at British Steel was six, I believe. I later met and got to know a couple of these. I worked part of my graduate training around the blast furnaces, and I admit to being subdued and frightened when I first went there.

The spirit soon comes out, though. There is something irrepressible and heroic about blastfurnacemen. Today, I feel proud to have spent a little time among them.

Iron, and the men who make it, will always be special.