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Solenoid valve rated for ten million cycles
Diaphragm combines chemical inertness, high-cycle life, enabling its use in human genome research
By Design News Staff -- Design News, December 16, 2002
Fairfield, N.J. — As human genome research shifts into high gear, engineers are increasingly searching for components with exceptionally high cycle-life to meet the "stop and drop" motion requirements of genomic equipment. Now, a new two-way solenoid valve reportedly meets those needs.
Known as the Oligo Valve, it combines a reliability rating of 10 million cycles with the chemical inertness needed for biotech applications. In doing so, it fills a growing void in this arena, where parts can be subjected to millions of cycles in a matter of weeks.
The Oligo valve accomplishes that by employing a perfluorelastomer diaphragm with a proprietary shape. The diaphragm's shape is critical, say engineers, because it enables the valve to combine the long cycle-life and chemical inertness features, which ordinarily don't go hand-in-hand.
"By nature, inert materials are prone to short lives," notes Aman Sharafi, product engineering supervisor for Parker Hannifin Corp.'s General Valve Operation. "The inherent characteristic of those materials is that they don't have much elasticity. Stretching them creates tensile stresses, causing them to get harder and eventually fail."
Parker's new diaphragm solves that problem, engineers say, because it all but eliminates the tensile stresses that cause failure. The company's engineers say they haven't changed the diaphragm's overall cross-sectional area in a significant way, but by moving material into key locations, they've provided a form of stress relief.
"When the diaphragm in this valve moves up and down, it doesn't stretch," Sharafi says. "By eliminating the stretching, we've eliminated the mechanical stresses that cause failure."
Parker Hannifin engineers say that the ability to combine the two "incompatible characteristics" is a key for bio-analytical equipment, which often must handle fluids that are chemically aggressive. By employing the inert perfluoroelastomer in the new Oligo valve, they claim they have prevented the potential swelling and cracking that occurs in diaphragms made from non-inert materials.
Furthermore, the engineers say that the valve's elimination of tensile stresses is particularly well-suited for biotech instruments, which must often "move, stop, and drop" chemical contents at extraordinarily high rates, across grid arrays calling for hundreds, or even thousands, of stops. Such performance requirements would quickly wear out ordinary rubber diaphragms, they claim.
Sharafi says that the Oligo valve is already being used in biotech and analytical equipment applications such as chromatography and spectroscopy, as well as in DNA/oligonucleotide synthesis equipment. The valve's diaphragm is said to be particularly applicable in synthesis of oligonucleotides, which have an aggressive chemistry and a low coefficient of friction. There, it serves well, not only because of its inertness, but also because it meets the high cycle-life requirements.
"Some of our customers demand 24-hour-a-day, seven-day-a-week performance," Sharafi says. "They want their solenoid valves to last for millions of cycles."
For more information on solenoid valves from Parker Hannifin Corp., General Valve Operation (www.pneutronics.com), enter 550 at www.designnews.com/info.
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