Originally Published MPMN November 2006

PRODUCT UPDATE

Controlling the Elements

Technological advances allow pumps and valves to easily manipulate flow and pressure of air, gas, and fluids

Pumps and valves are found in many different medical devices and manufacturing operations. By using new designs and strong materials, manufacturers are making pumps and valves last longer. These components also feature small sizes and dispense volumes, high flow rates, new connection options, and low power consumption. This article covers recent advances in pumps and valves.

Materials Make the Difference in Pump Performance

The wetted parts of a pump must be compatible with the medium being pumped. Selecting the right material keeps a pump working properly while reducing corrosion and providing chemical resistance. For example, highly acidic fluids can corrode stainless-steel pumps. However, materials such as Hastelloy, titanium, and some thermoplastics can be used in pumps that will be exposed to harsh chemicals and fluids.

KNF Neuberger Inc. (Trenton, NJ) supplies pumps for use in applications requiring high corrosion resistance or low outgassing. The company offers miniature air and gas diaphragm pumps with Type 316- stainless-steel or aluminum head plates. Pumps can be custom coated with PVDF for added corrosion resistance. PTFE is used to make pumps suitable for use with aggressive chemicals, such as sulfuric acid. A choice of dc, ironless core, and long-life brushless dc motors provides design versatility. The pumps are suitable for use in portable instruments where compact size, low current consumption, and reliability are needed.

Gear pumps are available in stainless steel, Hastelloy, and titanium from Tuthill Pump Group, Concord Operations (Concord, CA). The company offers miniature, leak-free gear pumps that are magnetically coupled, sealless, and nonpulsing. Pumps are also available in chemically resistant engineered plastic. Flow rates range from less than 1 ml/min to 38 L/min, with differential pressures up to 250 psi. The pumps can be used for metering, dosing, dispensing, sampling, and processing. Applications include medical, laboratory, temperature control, and heat-transfer equipment.

Tiny Pump Produces High Vacuum Flow

A multistage ejector vacuum pump can be used when working with small medical components. The P2010 vacuum pump from PIAB Vacuum Products (Hingham, MA) measures 1.08 in. high and weighs 0.54 oz. While most pumps require at least 59-87 psi, the P2010 can generate a vacuum of 24.9 in.Hg at a feed pressure of 26 psi. According to the company, the pump can reduce compressed air costs by up to 50%. In addition, company research indicates that the pump produces higher vacuum flow when compared with traditional single-stage ejectors.

Because ejector pumps do not give off heat, no cooling is needed. The small size of the vacuum pump prevents it from needing rigid mounting, making it easy to install. Feed pressure can be increased to 87-101.5 psi if needed. The pump features Coax, a patented ejector technology based on PIAB's multistage concept for creating a vacuum with compressed air. The technology integrates the internal components of a multistage vacuum pump into a vacuum cartridge.

Several Operation Modes Add Versatility to Syringe Pump

A syringe pump provides continuous fluid delivery, infusion, or withdrawal. The Harvard Apparatus Inc. (Holliston, MA) Pump 33 provides two independent pumping channels that are linked through hardware and software. When combined with a valve box, the unit provides continuous, pulse-free fluid delivery.

The pump features several modes of operation. Reciprocal or parallel mode enables the two pumping mechanisms to run independently, in the same or opposite directions. A proportional mode allows different flow rates and syringe diameters to be set for each syringe holder. The autostop mode terminates operation when a limit switch is activated. Continuous-run mode reverses direction at the flip of a limit switch. The pump has high-pressure capabilities, and includes TTL and RS-232 connections.

Ceramics Used to Make Valves, Pump Components

Ceramic materials such as high-purity alumina and tetragonal zirconia polycrystals (TZP) are used to make valves and other components. Ceramaret S.A. (Bôle, Switzerland) produces high-precision pistons, valves, and other custom-made parts. The components can be used in high-pressure pumps, pipettes, and dispensers. Hot isostatic pressing treatment is available on request for zirconia pistons. Surface finishes are polished to better than 1 µin.

Parts are available in standard sizes or can be made to customer specifications. All parts are made in-house to guarantee material quality during all stages of production. Applications include high-pressure pumps for analytical instruments and micropumping devices for the medical industry. The company is certified to ISO 2001:2000 and ISO 14001:2004 standards.

Sealing Feature on Valves Decreases Leakage

A maker of valves uses a flexible seal for positive leakage control of liquid or gas. Kepner Products Co. (Villa Park, IL) offers flow and pressure control valves with its flexible seal seat design. The seat design combines metal-to-metal and O-ring seal contact. The components'O-ring is securely retained at the seat, rather than on the poppet, protecting it from the destructive abrading and blasting effect of the flow. The seal closes around scratches, dents, and other irregularities. It is designed to prevent any leakage past the seat. A variety of O-ring seal elastomers are offered for system compatibility. The flexible seal seat is available on check, relief, shuttle, and pilot-operated check valves.

Controlling the Flow with Diaphragm and Proportional Valves

Diaphragm valves can be used for precise flow control. George Fischer Inc. (Tustin, CA) provides compact, lightweight diaphragm valves in chemically inert, abrasion-resistant beta polypropylene and Sygef PVDF. The Types 314-319 diaphragm valves are available in manual, pneumatically actuated, and high-temperature-resistant configurations. A zero-static option is also offered. The Diastar pneumatically actuated diaphragm valve series provides regulation and control for neutral or aggressive media in chemical- and water-treatment applications. The company's diaphragm valves come with metric spigot, butt-fusion, flanged, or bead-and-crevice-free ends.

A proportional valve offers increased flow rates in a small package. Parker Hannifin, Pneutronics Div. (Hollis, NH) has introduced the HFPro valve as part of its line of MDPro proportional valves. Using the same 15 × 15 × 45-mm body as the MDPro, the HFPro offers flow up to ~ 45 L/min at 25 psi, a 20-L/min increase over the next smaller orifice in the product line. The increased flow capability enables a single valve to be used where two were previously required, saving space and power consumption.

The valve features both 5-mm ID barbed and face-seal manifold bodies. Three standard control voltage ranges of 0-5, 0-12, and 0-24 V dc are offered. The unit consumes less than 3 W while continuously regulating full flow at maximum ambient temperatures of 50°C. Additional features include wire-leaded electrical termination, an FKM elastomer seal, and a 35-million life cycle rating.

The valve is suitable for respiratory therapy medical devices and high-flow gas control applications.

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