Saturday 24 December 2016

The Story of the Whirlpool by H Ranulph Hudston

Not coming from an engineering background at times I find myself simply in awe of engineering innovations. Brewing engineering of course, I couldn't give a monkey's about steam engines or bridges or whatnot. In particular, the elegant simplicity of whirlpools strikes me as a true marvel: cloudy wort is pumped in tangentially, trub and hop debris settle in the middle, bright wort is run off. If I had to come up with a trub separation system I'd probably think of some filtration system that would get horribly clogged in a matter of seconds.

In fact prior to the invention of whirlpools settling tanks were used with work run off by a float pipe, as H Ranulph Hudston recounts in The Story of the Whirlpool*. Which just goes to show I'm no engineer. Hudston was inspired to invent the whirlpool by none less than Albert Einstein and a cup of tea:
"He observed that when he stirred his tea, the errant leaves in his cup immediately migrated to the centre where they settled, the larger leaves being in the middle of the pile. He pondered the phenomenon, decided why the leaves overcame the centrifugal force of the swirling liquid, and produced the mathematical picture of the forces exerted and currents produced in the teacup. No practical use was made of this readily observable phenomenon, at least in the brewing industry, until the year 1960, when it was introduced by the author into Molson's Brewery, Montreal."
Trub in wort
 Wort was fed into the settling tanks over an umbrella to aerate it. When the pipe was moved to the side of the tank to avoid it Hudston noticed that the trub was more compact and there was a small clear peripheral band around the bottom of the tank. Further adjustments were made so the incoming wort went in a circular path:
"The result was a definite heaping of the trub in the centre of the tank and the formation of a distinct wide band, clear of trub, around the bottom. On the next brew, the wort was drawn from this bare area through a conveniently located outlet at the edge of the bottom. The wort ran clear for the entire brew; therefore the use of the float pipe was abandoned."
The brewery were also using a centrifuge to clarify the wort, but trials showed that more wort was produced using the whirlpool, so it took over. Hudston gave a talk on the principles and use of the Whirlpool tank at a Master Brewers Association of the Americas convention in 1960, and their use quickly spread around the world.

* The Story of the Whirlpool. H.R. Hudston. MBAA TQ vol. 6, no. (3), 1969, pp. 164-167

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