Main Menu

See All Software See All Instruments See All Transducers See All Vibration Testing Equipment See All Electroacoustics See All Acoustic End-of-Line Test Systems See All Academy See All Resource Center See All Applications See All Industries See All Services See All Support See All Our Business See All Our History See All Global Presence

Main Menu

See All nCode - Durability and Fatigue Analysis See All ReliaSoft - Reliability Analysis and Management See All Test Data Management See All DAQ Software See All Drivers & API See All Utility See All Vibration Control See All High Precision and Calibration Systems See All DAQ Systems See All S&V Hand-held Devices See All Industrial Electronics See All Power Analyzer See All S&V Signal Conditioner See All Acoustic Transducers See All Current and Voltage Sensors See All Displacement Sensors See All Force Sensors See All Load Cells See All Multi Component Sensors See All Pressure Sensors See All Strain Sensors See All Strain Gauges See All Temperature Sensors See All Tilt Sensors See All Torque Sensors See All Vibration See All Accessories for Vibration Testing Equipment See All Vibration Controllers See All Measurement Exciters See All Modal Exciters See All Power Amplifiers See All LDS Shaker Systems See All Test Solutions See All Actuators See All Combustion Engines See All Durability See All eDrive See All Production Testing Sensors See All Transmission & Gearboxes See All Turbo Charger See All Training Courses See All Acoustics See All Asset & Process Monitoring See All Custom Sensors See All Data Acquisition & Analysis See All Durability & Fatigue See All Electric Power Testing See All NVH See All Reliability See All Vibration See All Weighing See All Automotive & Ground Transportation See All Calibration See All Installation, Maintenance & Repair See All Support Brüel & Kjær See All Release Notes See All Compliance

Main Menu

See All API See All Experimental Testing See All Electroacoustics See All Noise Source Identification See All Environmental Noise See All Sound Power and Sound Pressure See All Noise Certification See All Industrial Process Control See All Structural Health Monitoring See All Electrical Devices Testing See All Electrical Systems Testing See All Grid Testing See All High-Voltage Testing See All Vibration Testing with Electrodynamic Shakers See All Structural Dynamics See All Machine Analysis and Diagnostics See All Dynamic Weighing See All Vehicle Electrification See All Calibration Services for Transducers See All Calibration Services for Handheld Instruments See All Calibration Services for Instruments & DAQ See All On-Site Calibration See All Resources See All Software License Management

Predictive Maintenance for Shaker Systems

Predictive test methodologies are designed to help determine the condition of your shaker system to prevent unexpected failures and to estimate when maintenance should be performed.

Unlike reactive maintenance, predictive testing methods provide valuable insight into whether your shaker may experience problems in the near future. Implementing a predictive maintenance test plan allows you to plan maintenance within the context of tightly packed test schedules and to reduce the risk of unplanned downtime and equipment failure. To do this, keeping a series of reference plots for a shaker is critical. These reference plots also allow you to see which of the many tests are putting the most stress on the shaker system. 

All shakers produce different characterization plots. It is important to keep a reference set and copies of the same performance throughout the life of the shaker system to ensure that your shaker performs at its best under your operating conditions. When reviewing the latest plots, with reference to the previous ones, differences can be looked at and implications can be drawn.

Recording a character of a shaker

When considering the performance of a shaker system, several aspects must be taken into account in order to properly create the different characterization plots.

  • Test Setup: Always use the same equipment setup. If there are any changes, run the same test with the old setup and again with the new, noting any differences due to the control equipment. 
    • Run the shaker in the vertical axis
    • Ensure that the shaker runs from cold
    • Fit a triaxial accelerometer to the centre insert of the shaker’s armature
  • Vibration Profile: Set a profile in the controller for a 5 mm peak-to-peak constant displacement crossing into a 2 gn constant acceleration sine sweep across the entire frequency range of the shaker. Use peak control with a 1 octave per minute sweep rate.
  • Recording: Record the drive, control and the cross axis in both directions.
    • Define the highest frequency that can be run with the control position, by looking at the drive. Ensure that the drive does not rise past the nominal level seen at 200 Hz
    • Run a high-level sweep at 20% of displacement, velocity and acceleration through the frequency range as defined previously. Record the drive, control, cross axis in both directions and the total harmonic distortion plotted through the frequency range. Use the same measurement technique for the analysis of distortion

Once these plots have been taken, they should be kept in a file and repeated at sensible intervals through the vibration test system life. These intervals should be determined by the usage of the shaker and the practical level of testing that can be performed. As a guide Hottinger Brüel & Kjær LDS would recommend taking these plots at monthly periods, or after any significant high-force testing that has occurred.

These plots can reveal several things, mostly about the health of the armature and suspension. Armature problems can mean either a failure in the coil, or within the frame. Changes to these plots over time will indicate that these parts are becoming worn or old. However, it does not necessarily mean that they need to be replaced. 

The fact that the plots are changing will indicate that they need to be monitored and possibly inspected visually. The speed of change indicates whether a failure is imminent. Changes tend to happen slowly to start with and then accelerate just before failure. 

What to look for in the shaker plots

Control plot

Ideally the plot will be flat, if it is not flat then it could indicate that there is a control problem. Nevertheless, there is very little that can be determined from the control plot alone.

Drive plot

This diagram should look the same as the previous 2 g drive plot in terms of level, shape and resonant frequencies.

The most important information is the first resonant frequency that can be seen on the drive plot. This frequency should be plotted over time to easily detect changes. Normally, with any unused armature, there is an initial change, that is, the frequency drops by 2 – 5%. It then stabilizes with minor further changes until the armature begins to fail. Large changes may indicate impending armature failure.

The shape of the drive plot should be the same as before. It is an indication of a problem if the curve has more ‘bumps’ or ‘dips’ than before. Large changes associated with a drop in resonant frequency indicate an impending armature failure.

The base level should be the same as before. If it is not, this may indicate either a control problem or a field loss.

Cross axis plot

This is the most difficult to interpret plot as it will vary with the temperature of the shaker suspension. To interpret this, you should look at the base level of the cross axis and see that it is approximately the same as before. 

Any peaks that occur should be logged in frequency and level and plotted through time. Hottinger Brüel & Kjær LDS would recommend taking 4 peaks to plot for any shaker, normally the highest, but spread through the frequency range, this may mean taking lower peaks at the lower frequencies.

Large changes mean that the suspension is getting worn and should be visually inspected.

Distortion plot

Although this is a different measurement to the cross axis, the same way of looking at it occurs. Take the previous plots and look at the base level shape to the curve. 

Check to make sure that the new plot matches this, while also checking the peaks are not changing primarily in level, but also in frequency. Changes in the base level or increased peak levels can indicate either a problem with the armature or the suspension. Refer to the other plots to identify the problem.

Other factors

Other factors can cause problems that would look like a failing armature, these are:

  • Loose accelerometer cables
  • Decoupling, either under the insert or under the accelerometer
  • Anything loose on the armature, inserts, screws, etc.
  • Excessive noise pick-up
  • As with any test procedure over time, consistency is the most important thing, ensuring that as many things as possible are kept the same

HBK maintenance plans suit your needs

Hottinger Brüel & Kjær’s service agreements and preventative maintenance plans provide you with peace of mind that your investment is operating at optimal capacity, allowing you to concentrate on other business-critical activities. All plans include support and annual service maintenance, covering inspection, testing and verification or adjustment of critical components.

Learn more about shaker service