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Optimized miniature diaphragm and vacuum pumps solutions

Posted: Wednesday, November 30, 2005

by Hargraves Miniature Diaphragm Pumps
Hargraves Miniature Diaphragm Pumps

Fluidic and pneumatic system developers are being challenged to develop medical devices, gas analyzers, fuel cell components, digital printers and other products in smaller package sizes. These development engineers require miniature diaphragm pumps, micro vacuum pumps or miniature air compressors that are optimized for pressure, vacuum, flow, noise reduction and efficiency in smaller envelope constraints without sacrificing long life. Hargraves Technology (HTC USA), www.hargravesfluidics.com, has developed an OEM program to optimize and configure a miniature diaphragm pump, miniature vacuum pump or micro air compressor to the fluid transport system’s specific application using standard components. The innovative Hargraves design permits configuration flexibility to achieve the optimal performance solution. The components listed below impact the fluidic performance of the miniature diaphragm pump in different ways.

Pump Stroke – The stroke length is the principal contributor to how much flow and pressure the pump produces - the higher the offset, the higher the flow and pressure/vacuum. Hargraves has the capability to manufacture many different stroke lengths and hold them to very tight tolerances.

Pump Head – The internal shape of the pump head has an affect on the pressure/vacuum levels that the pump can achieve. Hargraves has researched and developed various optimized chamber geometries that allow pumps to reach higher pressure/vacuum levels in a smaller package size than its competitors. Hargraves has several chamber configurations that can be selected for optimized fluidic performance.

Diaphragm – The performance of the pump depends on three different characteristics of the diaphragm:

Durometer - The stiffness of the diaphragm elastomer is measured in durometer. The higher the durometer, the stiffer or harder the diaphragm will be. This will result in pumps capable of higher pressures and flows. A lower durometer diaphragm will produce lower pressures, but requires less energy to operate.
Shape – The diaphragm shape dictates the flow and pressure level that the miniature diaphragm pump, miniature vacuum pump or micro air compressor can achieve. HTC USA has several different shapes that can be used depending on the application requirements.
- Flat - The flat diaphragm has the ability to operate in an alternating vacuum/pressure mode. However, there are limits to the stroke offset that can be used with this diaphragm.
- Molded or Shaped - If the application requires higher flow, a molded or shaped diaphragm will be used with a higher offset.

Elastomer materials – Most of the industry uses an EPDM (ethylene propylene diene rubber) material that typically could expect a life up to 3,000 hours under most operating conditions. This, of course, was unacceptable to our customers that were requiring life performance under demanding conditions to exceed 20,000 hours without service. To eliminate premature diaphragm failures, the Hargraves engineers searched throughout the elastomer industry for a material that would endure these rigorous demands at extended life cycles. They were repeatedly told by the so-called “industry experts" that this extended operating life could not be accomplished with elastomer materials. Undeterred, the Hargraves team took the initiative to develop a high performance diaphragm material. This research project resulted in the development of an advanced EPDM, or AEPDM, a proprietary material configuration that has been tested to last ten times longer than that used by other pump manufacturers. The life of Hargraves’ AEPDM diaphragms can exceed 20,000 hours depending on the application.

Hargraves also offers Viton and Teflon coated AEPDM for applications where the media is not chemically compatible with EPDM elastomers. For example, Viton is used in applications such as auto emissions analyzers and Teflon coated diaphragms are used in many ink/solvent-based applications.

Valves – Similar to the diaphragm, there are several variables when selecting the optimal inlet and outlet valves in the pump head for a specific application.

Shape - The standard valve used is a “butterfly" design valve, which has efficient and low noise characteristics. Hargraves still offers its original valve shape, the “flapper" in some applications.
Elastomer materials – The material that is used for the valve is dependent on the media that is being pumped. Hargraves’ standard material is EPDM, but offers the valve in Viton, Perfluro and our proprietary AEPDM.
Durometer –HTC USA has found that the durometer of the valve has an effect on the flow, noise and several other aspects of the performance.

Motor – The RPM and torque of the motor have several effects on the performance of the pump. The RPM setting will impact the flow rate and the time to achieve pressure/vacuum. The lower the torque, the lower the stalling pressure of the pump. Additionally, the RPM level will have a significant impact on the overall pump noise. If a low sound level is a critical requirement, then the applications solutions team will select a pump that can be tuned down to achieve the needed performance and reduced noise. Several motor technology options can be selected due to application considerations such as current draw, life, weight, envelope size, noise and cost.

Hargraves Technology application engineers are available to assist to optimize a miniature diaphragm pump, miniature vacuum pump, miniature liquid pump or mini air compressor for a specific fluidic application. By filling out an application worksheet with the system design criteria, an optimized miniature diaphragm pump recommendation will be presented. The Hargraves online store facilitates a fast and easy way to select a wide range of pumps for development testing.

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