Originally Published MPMN November 2002
Pumps and Valves Highlight Size and Accuracy
Suppliers introduce small and easy to use products
The need to accurately control the transport of gases and fluids is an important consideration in the design of many medical devices. To help meet this requirement, suppliers are constantly introducing new pump and valve technologies that offer OEMs increased functionality. From enhanced reliability and accuracy to smaller size and lower maintenance requirements, these components make it possible to meet almost any manufacturing requirement. Following are a few examples of recent pump and valve developments that may be of particular interest to our readers.
For further information on these and other products, please see the Buyers Guide directory of pump and valve suppliers.
Isolation valve reduces system media volume
|The Model 218 valve from Quality Valve & Components allows OEMs to reduce plumbing lengths and simplify flow-path configuration.|
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An inert two-way isolation valve minimizes space requirements to increase design freedom and limit the required volume of system media. Supplied by Quality Valve & Components, the Model 218 microminiature valve measures 1 in. long by 3/8 in. in diam, and requires no locating pins or other hardware for manifold mounting. "Many of the reagents used by our customers are very expensive," explains sales and marketing director Jason Kellenberger. "This valve's space-saving design allows OEMs to reduce plumbing lengths and simplify flow-path configurations to limit the amount of raw materials required to fill a system." According to Kellenberger, the component features an internal volume of 12 µl.
Offering chemical resistance for transmitting corrosive fluids and gases, the solenoid-operated valve is constructed with a Teflon diaphragm and polyetheretherketone (PEEK) body. The component delivers 35 ml/min of water at a pressure of 10 psi, and is available with a standard 24-V, 1.2-W power configuration. A 24-V, 0.5-W version is also available for continuous-duty applications that experience a maximum temperature rise of 35°C. Potential applications include portable drug dispensers, air samplers, and other handheld medical devices.
Gear pump compensates for wear
|Supplied by Micropump Inc., a gear pump uses a suction shoe to prevent flow from decreasing at high outlet pressures.|
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A gear pump from Micropump Inc. features a suction shoe design that compensates for wear and thermal expansion in continuous-metering applications that require maintaining accuracy over time. Offered in four standard gear sizes, the Series 180 pump uses discharge pressure to keep the suction shoe seated tightly on top of the gears to prevent flow from decreasing at higher outlet pressures. "This design also forces the gears and suction shoe to wear at the same rate, maintaining the same clearances over time," says marketing manager Jim Roberts.
In addition to enhanced durability, the Series 180 pump is constructed with fewer parts than previous models to minimize maintenance requirements. Available with helical gears that accommodate a range of temperatures, the pump provides pulseless flows at rates as low as 1 ml/min. The unit's magnetic drive and single seal keep the fluid securely inside the pump and prevent contamination. Constructed of stainless steel and engineered plastics, the pump is compatible with a variety of chemicals.
Potential applications for the pump include hemodialysis and laboratory equipment. The company can customize the component to meet individual requirements by altering construction materials, gear size, and mounting configurations.
Butterfly valves use solenoids to reduce space requirements
Two- and three-way butterfly valves from Aerodyne Controls employ rotary solenoids and brushless dc motors to reduce space requirements without sacrificing performance. "Because our valves use solenoids to provide isolation and throttling actuation, they're about half the size of valves that use other actuators," says sales manager Steven Pauly. "This design allows OEMs to design their products with much higher flow rates without increasing overall device size," he adds. Other benefits of the solenoid design include the increased reliability that results from a reduction in parts.
The valves are custom produced to customer specifications to meet strict dimensional and functionality requirements. Suited for high-reliability OEM applications, the components are available in diameter sizes of 1 to 4 in. Constructed to increase seal tightness and minimize pressure drop, the valves are available with a control system that modulates flow in response to a control signal. Current requirements can be as low as 28 V depending upon the application.
Solenoid pump suited for microdispensing
Expanding its line of self-priming solenoid-actuated microdispense pumps, Bio-Chem Valve Inc. now offers a unit capable of dispensing 8 to 250 µl of fluid per stroke. Suited for use in reagent dispensers, diluters, and draining devices, the pump features a factory-set output that allows repeatable dispensing rates of up to 200 dispenses per minute. An inert nonmetallic fluid path accommodates high-purity and aggressive fluids. Other product benefits include positive shutoff and low internal volume and power consumption.
As part of the Quick-Change Customization program, the company will modify the pump to meet a customer's application-specific needs. "To participate in the program, a client simply contacts us and tells us how the pump is going to be used," explains marketing coordinator Gary Gaetano. "Based on the application, we can modify the pump's manifold mounting configuration, orifice size, and connection specifications." A choice of plastics is also offered for construction of the pump's wetted parts.
Extended life is key feature of dispense valve
Supplied by Sealant Equipment & Engineering Inc., a tip-seal dispense valve is equipped with severe-duty components to extend unit life. Suited for use with aggressive materials, the 2200-245-series Kiss valve features abrasion-resistant seals and carbide-hardened needle and nozzle assemblies. "This valve doesn't contain a lot of soft goods," explains inside sales coordinator Paul Shafer. "And because it's mostly metal, it can accommodate fluids that range in consistency from water to thick pastes at very high pressures," he says.
In addition to sturdy components, the air-operated Kiss valve also features a nonrestrictive internal design that increases flow rates. According to Shafer, this modification translates into decreased downtime and maintenance costs. Other unit features include a stainless-steel spring that ensures shutoff if air pressure is lost.
Suited for the automated application of adhesives, sealants, silicones, urethanes, and other moisture-sensitive products, the valves can be modified to dispense materials in amounts ranging from beads to sprays. The valve features numerous drill-throughs and locator holes to accommodate manual, fixtured, and robotic applications.
Direct-acting solenoid valve offers high flow rates
A direct-acting solenoid valve from Humphrey Products Inc. offers a flow- rate coefficient of variation of 0.42 in a package that is 19 mm wide. According to company sources, the flow rate of the 315/415-series valve is 35% higher than those of similarly sized poppet valves. "In part, this elevated flow rate is enabled by the valve's patented lip-seal design that uses air pressure within the component to assist the spring in creating a tight seal," says representative Rich McDonnell. "Because it creates a positive seal, this feature also prevents contamination."
Featuring 1/8-in. NPT ports, the 315/415 valve withstands operating pressures to 125 psig. The component is offered with a 5-W coil and a variety of ac and dc voltage options. Designed for both in-line and manifold mounting, the valve is supplied with an optional sandwich speed control that mounts between the valve and the manifold. Potential product applications include oxygen concentrators and nebulizers.
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