Barrel-Dregs, Brulines-Flowmeter Home Truths. (136)

By | October 18, 2010

BRULINES-FLOWMETER HOME TRUTHS

Pot Boy has had a large number of e-mails asking what the very devil is a flow meter and how does it work, seeing as how so very much reliance is placed on the “spy in the cellar” by the Pubcos. Consulting my RAF engineering chum, ironically over a couple of pints of Spitfire (no pun intended I might add), PB got the low down of exactly what happens. All a bit technical I am afraid, but worth the telling!!

The Brulines flow meter installed in virtually all the tied pubs in the land is nothing more than a simple, and cheap, Pelton wheel turbine device and is manufactured by Titan Enterprises of Sherborne, Dorset.(Check out their website www.flowmeters.co.uk).

Pub flow meters are from the 800 series and are described by Titan as a mini turbine. The most popular is the Mini Turbine 824 in the Titan range. How it works is pretty simple. As liquid or gas flows through the meter it impinges on the rotor which has six blades causing it to rotate. Embedded in the rotor are three magnets which links to a powerful sensing device. As the rotor rotates, could be backwards as well as forwards, the magnets move past the stationary sensing device causing a series of voltage pulses, known as the Hall effect principle. By counting the number of pulses generated the volume of whatever has passed through the meter can be quantified.

The pulse frequency, or “k” factor which is pulses per unit volume is produced by calibration which is set when the unit leaves the factory. This has to be rechecked when the meter is installed in the cellar and should be rechecked by a qualified technician at least every six months. The meter cannot distinguish between beer, water or gas because any of the three or a combination makes the rotor move in either direction. Movement of the rotor will generate voltage pulses and measure “units” not distinguishing what made the rotor move in the first place!! Indeed by simply blowing into the meter with very little effort, the rotor can be made to rotate.

The nominal k factor advised by Titan is 1120 pulses per litre or 636 pulses per pint. Independent tests have shown that the Titan 824 had an average k factor of 1600 pulses per litre, substantially different from the factory based calibration. If the meter does not have any external markings it means that the unit would not have been factory calibrated by Titan and that a nominal k factor would not have been provided. Although Titan confirm that the meter components are of moulded construction, the nominal k factor should be able to be applied in the cellar set up by a suitably qualified technician. This is because the tolerances applied during manufacture should make the “setting up” a straightforward process. Independent tests do not seem to support the confidence of the boys at Titan. Don’t forget this is a very cheap piece of kit.

Meters are connected to a central panel in the pub. The panel is connected to a wireless transmitter from which data is sent to Brulines. The precise nature of the data transfer and the times at which it takes place have not been revealed by Titan. At some point in the process, a conversion of the data takes place. Each meter generates a number of pulses as the rotor turns. Using the meter k factor, the pulses can be converted into a volume equivalent, by dividing the number of pulses generated by the k factor. The precise nature of the data conversion is not known. It’s at the conversion point that the errors occur. If there is an error in the k factor, this error will be transferred directly (and with the same magnitude) to the volume figure. The Pubcos treat the resultant data as gospel, set in tablets of stone, and beyond reproach. Here the system and its inherent inaccuracies falls apart.

Phew !! PB needs a lie down in a cool dark cellar after that lot. A good rub down with a cold wet Brulines report might be appropriate !!

Pot Boy.

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