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5) Measuring the amount of beer in a keg without opening it:
Two large brewers, Mc Mullen and Sons and Bass Charrington wanted to accurately measure this for stocktaking purposes and for returned kegs. In the UK alcohol attracts a high duty (or tax), for this reason if many kegs are returned containing beer the contents must be known if the duty is to be accurately reclaimed, with many thousands of kegs being returned daily this can be a substantial amount.
For many years a highly experienced person with a special stick would tap the side of the keg and be able to give a pretty good answer as to the contents, however, the Inland Revenue required better accuracy, so a calibrated dip stick was used for many more years. This method was fine for returned beer but for stocktaking, in a pub cellar, opening the keg and inserting the dip stick caused beer contamination!
We spent many long hours exploring possibilities for a small hand held instrument (unfortunately we had to perform tests using water not beer!), initially we considered weighing the keg by tilting the keg and resting it's rim on scales but the floor needed to be perfectly flat and level, this could not be assumed down in an old cellar. We then realised that as the keg had a tube down the centre of it, almost to the bottom, we could pump bottled gas down this tube until it bubbled out into the beer and then measure the pressure difference between the top of the keg and the bottom of this tube (the hydrostatic pressure) this pressure could then be directly displayed on a digital display calibrated to read pints, gallons or litres. A small prototype was designed, tested and submitted to the customer for evaluation.
The customer was satisfied and has had many hundreds produced for them.
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