Beer inspires flow switching by magnets
A new generation of valves arises from a desire to improve the automatic dispensing
of drinks at the bar. Tom Shelley pulls up a bar stool and assesses the situation
Beer inspires flow switching by magnets
Very low cost and efficient valves can be made by using permanent magnet discs as closure devices.
High electrical efficiency arises because the discs latch onto the valve housing, in both the open and closed positions. They only require the switching solenoid to be energised to change them from one state to the other. They are , therefore, a desirable option in all applications requiring either low current consumption or low heat evolution.
Low heat generation was the reason for their original invention, conceived by semi retired engineer Ron Northedge while sitting in a pub near his home on the island of Jersey.
“The problem with conventional solenoid valves used in an automated pub dispensing system is that they are liable to warm the beer”, he explains. Being a serious engineer, he did not just think or talk about it, but went away, and produced detailed designs and patents and made working prototypes.
His first demonstration units, made in transparent plastic, have 6mm ports, rated flow rates of 4 gals/min at 3 to 4bar pressure and respond in 5.25ms.
The rare earth magnet disc is either attracted to or repelled by the single operating solenoid in order to switch. Refinements include a protrusion on the top surface of the disc, which inserts in a recess above it on opening to act as a dashpot, reducing impact and noise. On closing, shock impact is absorbed by an O-ring.
The valves could be made of a wide range of materials, operating over an equally wide range of flow rates and pressures. On the one hand, designs have been completed for 6 and 10in ball valves, while on the other hand, a major automotive manufacturer is said to have already “expressed a strong interest” in versions capable of switching low volume, high pressure flows as might be found in variable rate shock absorbers and the next generation of fuel injection systems.
The primary interest at the present time, however, remains with leading breweries. Guinness for one, according to the 22 February edition of The Times, wants to be able to serve up a pint of the foaming black stuff in 10s.
It is said that failure to deliver fast is leading to Guinness pumps being covered later in the evening with a towel in some of the more popular bars. Warmed beer, despite being something of a British tradition, is not, apparently, an acceptable price to pay for faster beer, hence Guinness’s interest in the new valve.
Mr Northedge says he has designed a multi-channel beer dispensing system which could deliver to an accuracy of 0.5%. Other identified potential applications include pharmaceuticals, process chemicals and oil and gas. The design is patented world wide.
Commercially available pneumatic valves which use little current, although not nearly as little as the Northedge valve, include the Minimatic Series Electronic Interface valves made by Clippard Instrument Laboratory in Cincinnnati, USA. These are available in the UK from The West Group
The sample device sitting on the editor’s desk requires current to be passed through a solenoid to maintain its alternate position but consumes only 0.67W. The valve element is mounted on a flat spring and complete travel is only 0.18mm. As a result, according to the catalogue, operating time is 5 to 10ms at 105psi (7.3 bar). Flow rate is 0.45scfm (0.21litres/sec) at 25psi (1.7 bar). Design life is more than 100 million cycles and many valves are said to have performed in excess of one billion cycles in service.
The valves are used in biomedical, environmental test equipment, computerised industrial automation and portable systems. The range now includes intrinsically safe valves and a new manifold mounted, normally open version. A free catalogue is available from the UK vendor.
The new magnet valve is simple and low cost
Power consumption is minimal because the magnetic valve disc latches onto the inside of the valve body in both open and closed positions and requires no power to keep it there
The prototype has a 6mm port size, is suitable for beer and similar fluids, and switches state in 5.25ms
The magnet valve can be made in any size, for almost any fluid and for use over a wide range of pressures
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