Fred Starr recollects – including the kitchen sink

Materials World magazine
,
7 Apr 2015

Including the kitchen sink

Fred Starr recollects..

In retirement, there are ways to keep mind and body active. The other day, looking into the back of a builder’s truck, I caught sight of some cast-iron gas pipes that were in remarkably good condition. Usually they are eaten through by bacteria of the Desulfovibrio desulfuricans type. In the worst cases, it leaves nothing but a shell of graphite and rust, only looking like the original pipe. 

D. desulfuricans just loves the sulphate and pyrites in London clay and, providing the conditions are anaerobic, it will eventually chew up buried iron. The heap of broken up pipes wasn’t, in fact, a good example of this form of corrosion. The pipes had probably been scrapped as part of the replacement of the UK’s 90,000km (somewhat dodgy) gas distribution system in preparation for the rather overdue hydrogen economy.

What caught my eye was a late example of a bell and spigot joint, an arrangement that goes back to the first days of the gas industry. The end of one length of pipe is made oversize (the bell), in which the adjacent pipe is plugged or spigotted. The joint was sealed by packing with jute, after which molten lead was run into the gap between the two ends of pipe. The lead was then supposed to be caulked (hammered) to ensure a good fit.

The modern version uses a rubber ring rather than jute packing and, as pictured above, a cast-iron ring is screwed into the gap, forcing the rubber into place. Bell and spigot joints have a certain freedom, allowing each length of pipe to respond to local ground movement – essential for a brittle material such as cast iron.

Crazy as it may seem, the old-fashioned lead-yarn joint worked. Throughout the world, it was the basis for gas distribution for more than 150 years. Quite fortuitously, gas from coal contained oily vapours and was wet, causing the jute to swell. All was well until the arrival of the modern gas-making processes, which were free from water vapour and tars. The jute dried out and the gas leak became phenomenal. It was whispered among those in the know that the leakage rate was a few per cent of gas throughput – the same sort of level as our profits! An immediate fix was to fog the gas with a spray of ethylene glycol, which kept the joints wet and reasonably tight.

But there was a much better solution in the offing – and here we look to the kitchen sink for having been in the vanguard of materials technology. People of my vintage will recall how in the 1950s, an enamelled sheet steel bowl was used when doing the washing up. Even when new, they looked and sounded dreadful, often being chipped when bought. After a couple of months, the white vitreous enamel – really only a glass – would break off, revealing patches of the black oxide undercoat. Not much later, the steel itself would begin to rust.

Polyethylene, a serendipitous discovery by Imperial Chemical Industries (ICI), was on the top-secret list all through the Second World War, when it was used in airborne radar. Following the end of the war, new markets were sought. Edmond Williams, who had been in the original research team, suggested washing up bowls to his bosses. But he had to fight to get his way. ‘Too soft. No temperature resistance,’ they argued. But within three years of the polyethylene bowl going on sale, the enamelled version disappeared completely. It is reckoned to be the fastest-ever substitution of one product by another.

The early bowls tended to crack, but the market was so huge that it was worth putting money into getting the product right, which made it even more appealing for use in the UK. So, when British Gas began to look for something better than cast iron, it was ICI that was able to supply a well-engineered material that was superior to its main rival, PVC. Polyethylene’s combination of strength, flexibility, immunity from corrosion and its ability to be welded made it ideal for distributing gas around town. The material is flexible enough to refurbish existing gas mains without ripping up miles of highway. Just dig a short trench, smash open a length of cast-iron pipe and then thread in the polyethylene replacement. That probably accounts for the bits of pipe in the truck. 

It was a success story for two great organisations, which showed themselves at their best. And, in the spirit of one hand washing the other, British Gas supplied ICI with natural gas to make polyethylene and we bought their product. I wonder what happened to either?