Dynamic Balancing to API and ISO Standards

May 9, 2019by cbmadmin

Keeping equipment properly balanced is crucial in maximizing its usefulness, longevity, and safety. Maintaining optimal balance of rotating components minimizes the need for repairs, cutting both costs and machine downtime. A properly balanced rotating component creates less undue wear-and-tear on bearings and less overall vibration. In fact, improper balancing is a leading cause of rotating equipment failure. Don’t put it off. To maximize the efficacy and lifespan of machines with rotating components, and to bring them into compliance with industry standards, dynamic balancing services should be performed as soon as any unbalance is suspected.

The Importance of Proper Balance

When a rotor is unbalanced, unnecessary vibration causes stress in both the rotor and its support structure. As bearings and other support systems are exposed to repeated excessive loading, the mechanical seals will become damaged and may eventually fail. The rotating element of a pump will work more efficiently and last much longer if it is properly balanced.

Major Causes of Unbalance

The following are the most common factors that cause rotating elements to become unbalanced.

  • Improper mounting during stacking
  • Incorrect machining and fabrication tolerances
  • Non-homogenous component material
  • Damaged shaft (this is most commonly caused by heat or mechanical conditions)
  • Haphazard mounting of components
  • Non-symmetrical rotors
  • Malformation of rotating elements (from stress or extreme temperature fluctuations)
  • Product buildup in or around the component
  • Corrosion or erosion of rotating components (this can be the result of aforementioned product accumulation)

Industry Standards

The American Petroleum Institute (API) and the International Standards Organization (ISO) have set guidelines so that manufacturers and repair shops have a standard by which to perform dynamic balancing operations. Aside from providing recommendations and requirements for design principles, functionality, and analysis for all manner of rotating components, these standards provide vital information for finding proper balancing tolerances and conducting effective machinery performance testing. The standards use precise calculations to recommend balance tolerances in relation to a part’s diameter-to-length ratio. ISO also supplies the industry with a Balance Quality Grade, to be applied in order to figure the limits of residual unbalance.

Tolerances and Unbalance Allowances

Industry standard-setters hold that there is a certain allowance for residual imbalance, or the amount of imbalance still left after a rotor has been balanced. Using a formula set forth by the API, a manufacturer or repair technician can find the maximum allowable residual imbalance for each correction plane of the rotor being serviced. There is also a recommended margin of safety for variations in the residual unbalance between the time the unit is serviced and the time it is inspected. This recommendation, set by the ISO, recognizes that slight changes can sometimes be written off to calibration differences in inspection equipment, heat and humidity, drive errors, and tooling issues.

Professional Dynamic Balancing

Achieving optimum tolerance levels during balancing requires precision equipment and expert techniques. Sometimes a portable balancing system is warranted when the equipment being serviced is not able to be easily transported. Streamline Industries offers comprehensive dynamic balancing services that include data readouts to ensure that your machines are within the guidelines and standards of the industry. These data also provide incredibly useful insight into the factors that contributed to the original state of imbalance so further unbalance can be prevented.