Top scientists spin to win

A piezo-controlled pressure regulating valve is helping chemists and physicists examine matter at atomic and subatomic level by controlling rotational speed in a nuclear magnetic resonance chamber built at Bruker BioSpin in Rheinstetten, Germany.

Non-destructive analysis of materials is a key technique for scientists working in a wide range of fields, with much of the current work being conducted at the atomic level. Bruker BioSpin have developed a system for nuclear magnetic resonance (NMR) analysis in which a sample container, supported on an air bearing is turned using precision blasts of air.

During the design stages the Bruker engineers undertook an extensive search for a suitable high performance valve and found only one that met all their criteria, the Tecno proportional valve made by Hoerbiger-Origa.

NMR works on the same principle as the medical procedure of magnetic resonance tomography. A very strong magnetic field is created within the chamber and radio waves are directed through it. This affects material in the chamber by transferring atomic nuclei to different energy levels as they absorb the radio waves. Different substances absorb different frequencies of wave, so can be identified by their ‘resonance frequency’.

Because of the magnetic field, conventional electric motors cannot be used in this application and due to the spin speed an air bearing is the best option for supporting the rotor. These two factors combine to suggest that an air motor may be the best prime mover for the system. However few air motors are able to offer the precision required.

The Bruker team found the answer in using Hoerbiger-Origa’s ‘Tecno piezo controlled air pressure regulator to drive an air turbine with precise blasts of air.

Proportional pressure control is achieved using a tiny piezo ceramic lever that is bi-stable under the effect of a nanovoltage signal. One of its main attributes to Bruker is that its switching is practically instantaneous so gives very good control of air flow. Another is that the nanovoltage does not adversely influence the magnetic field.

In fact the chamber uses a second Tecno valve, this time controlling the air bearing in relation to the total mass of the rotor plus its test pieces.

A test procedure may involve several hours of operation, during which time the rotor may be turning at up to 65000 rps (3,9 Mrpm). Part of the design brief was such that the Hoerbiger-Origa valve control movement to +/- four revolutions.

Ray Barnes, Hoerbiger-Origa’s UK Managing Director, says the company is no stranger to such projects. “We have equipment at other high level research establishments in the UK, the performance requirements are almost always astonishing to those of us from an industrial background, but the extreme demands help us to raise performance specifications for our standard equipment and to push back the limits of the products capability.”

HOERBIGER Origa is a company of HOERBIGER Automation Technology, a business unit of HOERBIGER Holding AG, Zug / Switzerland. HOERBIGER is active throughout the world as a leading player in the fields of compression technology, automation technology and drive technology. In 2007, its 6,300 employees achieved sales of around 1 billion Euro. The focal points of its business activities include key components and services for compressors and engines, pneumatic and hydraulic systems for vehicles and machine tools, as well as components and systems for shift and clutch operations in vehicle drivelines of all kinds. Through innovations in attractive technological niche markets, the HOERBIGER Group sets standards and delivers cutting-edge solutions for the benefit of its customers.

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