Dynamic Balancing Services: The Down And Dirty

Dynamic balancing is the process of balancing machines by measuring imbalance using sensors as the machine rotates. These sensors pick up vibrations and can help you determine where corrective measures need to be taken. All rotating machines have some sort of vibration as they are in operation but dynamic balancing sensors look for an excessive amplitude of vibration.

Excessive vibration can reduce equipment life and also create a number of other issues. While eliminating all vibration is not possible, the closer you can get to the true axis the better your machine will operate.

How Balancing Works

Centrifugal fan dynamic balancing

As an example, lets consider a centrifugal fan in a production facility. The fan spins (or osculates) around an axis point that may or may not be in a good balance. To test the balance of the fan, we place sensors on the rotating pieces of equipment (bearing pedestals) to detect vibration.

These sensor gather information during rapid rotation and tell you if the system needs to be adjusted.

If the centrifugal fan needs adjustment, weight can be added or removed. This is commonly done on the rotating outer portion of the fan to achieve a better balance. Adding weight is generally easier than removing weight and can involve attaching bolts, nuts and washer to small fans. For larger fans, welding on small steel plates is a common technique used to achieve a better balance.

Once weight has been added the fan, it is then tested with sensors again to ensure it has reduced the overall vibration. According to Infinair, typically an unbalanced level for a small fan is G2.5 and G4.0 for larger fans. This is based on AMCA standard 204.

Benefits Of Dynamic Balancing

The main benefit of dynamic balancing is reducing vibrations. This can increase safety and improve equipment performance, lifespan and reduce heat. Performing a balancing test can also:

  • Reduce excessive noise
  • Prevents impeller and component erosion
  • Detect casting imperfections
  • Highlight loose parts causing imbalance

Dynamic VS Static Balancing

Static balancing (AKA primary balancing) is the act of balancing machinery based on its center of gravity while it is not in rotation. This involves attaching low friction bearings to the machinery and the heaviest section will naturally swing to the bottom. You then remove material from the heavy side or add to the lighter side until the piece no longer rotates without assistance.

Dynamic balancing on the other hand involves rotating the equipment while measuring the imbalance, so you can add counterbalances.  

While both types of balancing have their place, dynamic balancing is commonly the preferred method. This is because it can lead to a more accurate balance.

Sensors and Vibration Analysis

Balancing is the act of adding and removing weight to reach a more balanced position. Vibration Analysis is the key behind making these adjustments in the proper places.

Sensors measure the vibration. The type of sensor determines what you can measure. For instance, some sensors measure vibrations and displacement, while others measure velocity and acceleration. Some common sensors include piezoelectric (PZT) sensors, laser doppler vibrometer, proximity probes, accelerometers and microelectromechanical sensors (MEMS).

For the more technically minded people, you may like Bruel and Kjaer‘s description of how sensors work.

“the fluctuating vibration force can be detected, and an electrical signal sent to a vibration meter. The indicated vibration level is directly proportional to the resultant of the unbalanced masses.

The direction in which this resultant acts (i.e. the radius containing the centrifugal force) can be determined in an accurate way by comparing the phase of the fluctuating signal leaving the vibration meter with a standard periodic signal obtained from some datum position on the rotating object.

It is now possible to define the unbalance at the bearing by means of a vector. The length is given by the magnitude of the unbalanced force (the measured vibration level) and the angle is given by the direction of action of the force. Further, if the resultant unbalanced force at a bearing can be resolved into its primary (first-order moments) and secondary (second-order moments) components, it will be possible to balance the object.”

Equipment Performance

We attach sensors to all sorts of equipment to gauge performance. Some common equipment includes:

  • Industrial fan balancing Engine Crankshafts 
  • Pumps
  • Gears
  • Piston Engines
  • Flail Rotor Balancing
  • Reciprocating Compressors
  • Industrial Fans
  • Flywheels
  • Drive Shafts
  • Impellers

Our Reliability Department

Reliability testingOur Reliability Services department uses the latest technology to detect problems before they occur, preventing downtime and lost revenue. We help you save money by maximizing up-time, efficiency, reliability, and equipment life. Our customer-focused and consultative approach means we bring quantifiable results that focus on your unique facility. We provide:

Call us at 1-800-237-3141, email sales@rasmech.comchat with a support agent, or contact us online.