Spiral wound plastic tanks: a quarter of a century—not out!

Seamus QuinnThe following is an edited version of an interview with Chem Resist’s Chairman, Seamus Quinn, which appeared recently in ABC Magazine:

Back in the dark ages of the early 1990s, most British manufacturers still used welded sheet techniques for the majority of their storage tanks. But then, spiral-wound tanks produced on mandrels—a relatively unknown technology at the time—took hold and went from strength to strength; and Chem Resist was one of the innovators of this new technique.

“Swapping notes with other European manufacturers was the lightbulb moment,” recalls Quinn; who at the time was sitting as a technical expert on the European Standards committee tasked with developing a standard for Thermoplastic Tank design, and who went on to pioneer the technology in the UK. “The odd thing was that spiral wound techniques were supposed to be the mainstay of the standard, but it was clear straight away that the UK were going to be left behind making tanks out of welded sheets.”

The observation gave Quinn an idea: to introduce and develop spiral wound methods in the UK. In 1992, recognising it would represent a step change for British manufacturers, he set about putting the technique on firm footings. For three years, Chem Resist worked in partnership with Cambridge University to identify the best technique for spiral winding thermoplastic cylinders. In parallel, the West Yorkshire-based company put in place a dedicated industrial facility for their manufacture, along with the extrusion and winding equipment that would allow it to produce cylinders up to 3m in diameter and with wall thicknesses of over 75mm: a crucial factor, made possible by the development work.

“In the early days most tanks were polypropylene, which was the industry’s material of choice back then,” Quinn remembers, “but that changed with time, and these days most tanks are produced in High Density Polyethylene (PE100-RC), with Polypropylene generally reserved for high temperature applications.” 

For the first time, there was an alternative to GRP construction where chemical tanks of volumes between 20,000 and 130,000 litres were required. As thermoplastic tanks became more popular, and the adoption of the BS EN 12573 design standard increased engineers’ confidence in the technology, requests grew for larger vessels. These days tanks are commonly being manufactured with volumes approaching 150,000 litres and dimensions of the order of 4.3m diameter and 150mm thickness.

The possibility of designing and manufacturing such heavy gauge tanks in polypropylene and HDPE means that these tanks can be used safely for high-temperature-reaction applications, such as sulphuric acid dilution: a unique Chem Resist technology. As a result, the volume of corrosive chemicals stored in these types of tanks now runs into millions of metres cubed, and the units are being exported to every lead-acid battery manufacturing area of the world.

What advice does Quinn have for manufacturers in the future? “I can summarise it in two words,” he says bluntly: “invest and export.” And Chem Resist has practised this mantra. Its UK operation has been underpinned by a ten-year planned investment programme that has seen new buildings, extruders, and stainless steel formers put in to extend the tank range.

We might be the oldest manufacturer of spiral wound tanks, but there’ll be no downward spirals on my watch!” jokes Quinn about the company’s latest project: installing a new 11,000m3 fabrication hall to improve work flow and meet increasing demand. And he’s right, the future looks bright for manufacturers in this segment: as a workhorse of chemical storage, new markets for spiral wound tanks are developing all the time. And with a more competitive pound, exporting is more attractive than it has been for a number of years.

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