Considerations in vacuum pump suitability
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Whilst component performance, size and cost are obvious considerations in the selection of vacuum pumps, these rather bland descriptors can represent only the tip of the iceberg. We look below the surface to reveal far-reaching design implications
Reducing weight, improving handling, expanding applications, gaining production efficiency and saving space and energy are all important engineering considerations in the design and development of consumer, commercial and industrial products.
Whilst the glamour of any new design often seems to be focused on the miniaturisation of electronics components and microchips, it is most often the workhorse components which are the real key to a product's success or failure. The application scope of products such as vacuum pumps is enormous. Within a whole host of medical, environmental, automotive, aerospace and many other products, pneumatic systems such as vacuum pumps and compressors are mission-critical components, and increasingly in their initial selection they are being treated as such.
Working in miniature
With pneumatic system size ultimately limited by the laws of physics, core components like vacuum pumps are never going to enjoy quite the same breathtaking headlines as the electronic devices that share space in the overall product package. That said, innovations in vacuum pump design have led to dramatic reductions in size which can enable OEMs to realise significantly smaller product design envelopes.
There are no "one size fits all" solutions with miniature pumps, with designers offered a wide range of choices including diaphragm, piston, rotary vane, vibrating armature diaphragm and peristaltic pumps. Selection of the right pump has to be defined by the specific application. In medical devices, diaphragm and rotary vane pumps are common choices. Both operate with low electromagnetic interference motors and offer optimal speed control with minimal torque sacrificed. Both offer a wide range of pressures and flows. Diaphragm pumps are tighter, leak-proof and provide greater vacuum/pressure without contaminating a medium. The rotary vane design provides a smooth, pulse-free flow, but the transported media is in direct contact with the pump vanes which increases the potential for contamination.
Rotary vane pumps do, however, offer ultimate potential for miniaturisation, with typical applications including portable gas analysers, and medical and analytical instrumentation.
In other areas, vibrating armature pumps are preferred for continuous duty, when pump longevity and zero-contamination risk are important. However, these AC pumps are less compact than other miniature pumps. Piston pumps are compact, and provide above average vacuums/pressures, but are not leak-free.
The price is right
Component cost is always a consideration in the development of any new product, but there can be much more to consider than the initial purchase price. Meeting stringent demands for end product miniaturisation, for example, can mean that pump modification is necessary. Similarly, a product upgrade can necessitate significant system design changes which can require alternative pump mounting strategies, orientation and other design tweaks. Whilst these modifications can undoubtedly be achieved by the OEM, they can often more easily be accommodated by the manufacturer, providing cost savings in the longer term even though the purchase price might be slightly higher.
Cost is also becoming an issue in industries that have traditionally enjoyed a certain flexibility in their end product pricing. The medical industry, for example, had few incentives in the past to disclose product cost objectives to the likes of pump manufacturers. Now, target price objectives have become crucial in product development, with neither the pump manufacturer nor the OEM product designer able to ignore the volatile economic and technical forces in today's market.
Early dialogue with the pump supplier in the design phase can resolve all-important cost issues and help attain required performance and reliability levels. If that dialogue also extends to the OEM's service department, additional company concerns can be met. For example, a lower cost component specification that enables a finished product to be designed, engineered and manufactured under budget might actually sabotage overall company profits in warranty and service work. A knowledgeable pump manufacturer can match pump type and materials of construction with the necessary duty cycle to meet the end product lifetime, maintenance schedule and reliability requirements.
The performance advantage
Vacuum pump performance measured in terms of achievable flow rates, vacuum levels and pressures, has direct links to both component size and cost. A pump which offers significantly superior performance when compared to conventional designs might cost a little more, but that improved performance might well translate into a corresponding competitive advantage for the OEM in the finished product. Alternatively, it might allow an OEM to standardise on a smaller pump for a given task. Pump selection, therefore, becomes a process which needs careful analysis.
Make it smaller; give me better performance; make it easier for me to integrate into my product; make it more reliable; reduce my cost; and give it to me quickly - these are seemingly contradictory system design mandates. But when innovations in vacuum pump design are coupled with customisation capability and an early and meaningful dialogue with the OEM, a component specification can be made which will go a long way towards ensuring the end product's success.
29 June 2006
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