Bruel & Kjaer UK Ltd. - PRODUCT NEWS

Using vibration diagnostics for consumer goods reliability

Ensuring the reliability of heating and refrigeration circuits, the Valliant Group’s Center of Competence uses vibration diagnostics to understand and predict damaging resonances in systems and components such as piping and compressors.

Located in Vitoria-Gasteiz in Spain, the Vaillant Group’s Center of Competence (CoC) develops and approves Refrigerant Circuit Modules (RCMs). These RCMs are the core of both the aerothermal and geothermal heat pumps manufactured by the Vaillant Group. Heat pumps are one of the key product segments for the Vaillant Group’s renewable energy strategy.

When it came to ensuring the reliability of their RCMs, the CoC chose a vibration analysis system from Brüel & Kjær. Development and Innovation Engineer Javier Oleaga said: “We were looking for an instrument which would enable us to accurately characterise the vibration of a refrigerant circuit module, in order to assure the quality and lifetime of the heat pump. When we decided to buy equipment to measure and analyse vibration signals, our partner - the University of Mondragón -recommended Brüel & Kjær’s vibration systems to us.”

In this test procedure, the objective is to find the frequencies at which the excitation frequencies of the compressor can generate resonances (large-amplitude displacements), which cause fatigue and breakdowns.

This requires measurement of the natural frequencies of the pipes, which move in three dimensions. Triaxial accelerometers are placed in key positions on the critical pipes. Then the piping is excited with a purpose-designed impact hammer made by Brüel & Kjær.

The obtained result is a series of Frequency Response Functions (FRFs), showing the natural resonant frequencies and the amplitudes of the piping at those frequencies. The acceptance criteria are to check the correct shape of the time signals (force and acceleration), the autospectrum of the force, and the shape of the coherence in each measurement. If they are correct, the measurement is validated and the results are considered reliable.

About Bruel & Kjaer
Brüel & Kjær is a world-leading manufacturer and supplier of sound and vibration solutions for use in a wide range of applications including environmental noise measurements, building acoustics, vibration measurements and quality control for use in the automotive, aerospace and consumer industries, as well as by local authorities. Today Brüel & Kjær has 900 employees and sales offices in 55 countries. Brüel & Kjær is a subsidiary of UK-based Spectris plc. ( Spectris has annual sales of approximately £656m and employs around 6000 people worldwide in its 15 business units.
For more information, please contact :-

Bruel & Kjaer UK Ltd.
Jarman Way, Royston, Herts. SG8 5BQ. UK
Tel: +44(0) 1763 255 780
Fax: +44(0) 1763 255 789

October 2012

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