3 June 2020
by Fred Starr

Fred Starr recollects: Sleep on it – talking about fatigue

Fred Starr on the detrimental impact of fatigue.

Fred Starr
Fred Starr

Have you been, for once, getting enough, over the past two months of home working? Not having to wait till the weekend to satisfy your bodily and mental needs? I am referring to a good night’s rest of course. What else? 

The issue is tackled in the recent and authoritative paperback – Why We Sleep – by the neuroscientist, Professor Mathew Walker. He has been researching the subject, experimentally, for over 30 years. His basic finding is that humankind has to get eight to nine hours sleep. Every night. Anything less is detrimental to health. Catching up doesn’t work. The most disturbing passage in the book mentions someone who, as a result of a brain malfunction, died through an inability to sleep. After several months of hell, the patient looked like a man who had starved to death.

Professor Walker is more than anxious about how modern living impacts on our sleep patterns, and what this does in being able to act sensibly, disrupting both long- and short-term performance. He bewails street and interior lighting, noise from traffic and air conditioning, and late-night TV. But he directs real anger at the unofficial lengthening of the working day, where the perception is that to get to the top, you must be at it all the time.  

Asleep at the wheel 
Although it happened so long ago, in 1966, it was Gerry Francis in his April 2020 letter mentioning thermal fatigue, which brought to mind a quite literal, explosive incident on a steam reformer, when the basic cause was overtiredness. In this context, experiments by Walker on volunteers have revealed just how detrimental a few hours of lost sleep are. 

But turning back to steam reformers, thermal fatigue and creep are long-term modes of failure, eventually showing themselves as the almost imperceptible cracking and bulging of a reformer tube – essentially safe modes of failure. What would be totally unexpected would be a massive blowout, especially if the reformer and tubing were brand new. Amazingly it did happen at one place where I worked.

On my first day there, as I was being shown around, we came past the reformer in question. I saw a massive pile of smashed-up brickwork and piping. ‘What’s this’ I asked. ‘Oh, there was an explosion when we tried to start up the new CRG Process, and the side of the reformer blew out.’ This was said quite casually, perhaps not to put me off. No chance! Me, Fred Starr, veteran of the steel industry!   

Much later, I heard the full story. The blowout was in the early hours of the morning, after the key people had been on the job for 17 hours. By then, the control room was jam-packed with the team from the manufacturers, the Station Engineer and his deputies, shift personnel from the CRG itself, and all the other plants on the site.

Only one thermocouple 
Once one begins to start up a steam reformer, there is really no good place to stop. The pipework has to be swept free of air using nitrogen. Then, very gingerly, hydrogen, at pressure, is admitted, being used to reduce the catalyst in the reformer tubes. This is a tricky time as the reaction is highly exothermic. Once things are under control, a full flow through the tubes can be established, and the burners in the reforming furnace can be turned on to the proper extent.

It didn’t help that the reforming furnace was of the side wall firing design, which was new to everyone. Nevertheless, after hours of ‘shall we do this or shall we do that’ all the burners were lit. Success seemed so close that there was a moral embargo against anyone going home, despite everyone being dog tired and hungry. No one was to be the first to leave.

Instrumentation and control systems, intended for normal running, are not ideal in the start-up phase. The only indication of what temperature the tubes might be reaching was in the outlet header, where there was just one thermocouple. This could only give a sensible reading if there was a good flow of hydrogen. But through over caution and exhaustion of all concerned, there wasn’t. So while the tubes were getting hotter and hotter, the thermocouple was showing nothing.

As tube temperatures zoomed up to 1,200°C, with no flow but with 300psi of pressure inside, a double bang was inevitable. First when the tubes burst, and then when the hydrogen poured into the furnace, causing a modest, but somewhat damaging, gas explosion. Fortunately, no one was injured. However, if you have got anything out of this anecdote, metallurgically or otherwise, why not sleep on it? 

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Fred Starr