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SPM Shock Pulse Monitoring dBm/dBc

SPM Shock Pulse Monitoring dBm/dBc

dBm/dBc which is a part of the original Shock Pulse Method (SPM) is used to obtain an easy, fast and reliable diagnosis of the operating condition of rolling element bearings.

Features of dBm/dBc Shock Pulse Monitoring

  • Easily understandable condition evaluation in red-yellow-green scales
  • Easy, fast and reliable diagnosis of bearing condition
  • Verifies the source of high shock pulse readings when used with SPM Spectrum

Bearings generate shocks in the interface between the loaded rolling element and the raceway throughout their lifetime. And, the shock pulse transducer outputs the electric pulses proportional to the shock magnitude while these shocks ring it.

In fact, shock pulse transducers make it possible for you to have a calibrated measurement of the shock pulse amplitudes; because unlike vibration transducers, they respond at carefully tuned resonance frequency of about 32 kHz.

Measuring dBm/dBc

Shock pulses which are produced in the bearings and traveled through the material will be picked up by the transducer. Then, it convert the shock pulses to electric signals which are processed to provide a peak value and a carpet value.

After that, the shock pulse meter counts the rate of incoming shock pulses per second (occurrence); and changes the measuring threshold until two amplitude levels are determined:

  • The shock carpet level (approximately 200 incoming shocks per second). This level is displayed as decibel carpet value (dBc ).
  • The maximum level (the greatest incoming shock under 2 seconds). This level is displayed as decibel maximum value (dBm).

The operator can establish a peak value (using a flashing indicator or earphones) by increasing the measuring threshold until no signal is registered. In fact, shock pulses are measured on a decibel scale (1000 x increase between 0 and 60 dB); because of their very large dynamic range.

Shock pulse amplitude is determined by three basic factors:

  • Rolling velocity (bearing rpm and size)
  • Oil film thickness (distance between the metal surfaces in the rolling interface). The oil film thickness depends on load, alignment and lubricant supply
  • The mechanical state of the bearing surfaces (roughness, damage, stress, loose metal particles)

Analyzing dBm/dBc

You can determine the source of shock pulse by analyzing the shock pulse measurement in the frequency domain. And, “SPM Spectrum” is there to verify the origin of high shock pulse readings. In fact, the damaged bearings generate shocks that typically have an occurrence pattern matching the ball pass frequency over the rotating race. For instance, the shock which are produced in damage gears reveal other types of patterns; while random shocks from disturbance sources have none.

Of course, the frequency patterns of bearings are available in SPM Condmaster Ruby (a comprehensive diagnostic, troubleshooting and analysis software). Also, linking the symptom group “Bearing” to the measuring point makes it possible for the user to highlight a bearing pattern by clicking on its name. You can also add other symptoms when it’s needed. Actually, measured signal originates from the bearing; and finding a clear match of a bearing symptom in the spectrum is the proof!

SPM Instrument offers a wide range of condition monitoring; predictive maintenance and inspection equipment. Therefore, if you like to see the list, don’t hesitate to click here and see the list with pricing and details.

At last, Felixtrument supplies a complete range of innovative acoustics and audio equipment which come in different types and sizes. Therefore, if you are in need of any Sound & Vibration equipment; you may browse through our various products which you may find in the mentioned link; to find the one which best suits your needs.

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