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SPM Instrument has introduced a shock pulse measuring technique, which is suitable for low-speed machinery applications such as twin wire presses, screw presses, drying cylinders and wind turbines.

According to the company, condition monitoring is all about optimising operations and maintenance for the purpose of lowering costs.

It is difficult to obtain reliable results when measuring on low-speed applications.

These applications create signals with low energy content, where earlier vibration technologies made it difficult to measure such signals with satisfactory results.

SPM Instrument’s next-generation SPMHD measuring technique combines the True SPM method with an advanced digital technique.

Thanks to its high dynamics, SPMHD can distinguish the weaker yet relevant signals, which are typically hidden among stronger signals caused by mechanical shock phenomena or electronic noise.

Therefore, the ability to detect weak signals provides advantages when measuring at low speeds.

SPMHD is built around patent-pending signal processing in several steps.

The technique works with the digital enveloping of the analogue shock pulse transducer signal.

The sampling frequency is very high, resulting in a crisp and distinct signal.

A 24-bit A/D converter provides sharp resolution and detail in spectra and time signals.

For a full picture of the bearing condition, the measuring cycle is based on number of revolutions rather than time.

This maximises the chances of capturing relevant signals in the course of one measuring cycle.

By adjusting the sampling frequency to revolutions per minute, spectra are said to be clear and concise.

The measuring technique looks for recurring patterns and uses newly developed algorithms to enhance repetitive signals and to eliminate randomly occurring high readings.

Thanks to the pattern recognition, spectra and time signals are suitable tools for analysis.

According to the company, the source of the signal is simple to identify as every component has its own, distinct damage signature.

The time signals are easily interpreted, making the type and extent of the damage simple to determine.

As a result, no trending is required; occasional measurements provide a reliable diagnosis.

In addition to spectrum and time signal, the measuring technique also generates two scalar values: HDm and HDc.

HDm represents the highest value measured during the measuring cycle, while HDc is a measure of the bearing lubrication condition.

Both values are suitable as the basis for setting alarm limits, regardless of machine type.

The automatic evaluation of measuring results, presented on a green-yellow-red scale, provides a quick overview of machine condition.

SPMHD has been tested on low-speed applications such as twin wire presses, screw presses, drying cylinders and wind turbines, some running at speeds as low as 5rev/min, for many months.

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