Torsional Vibration Analysis (TVA)

Examples of Damaged Shafts and Couplings
A) Motor FailureB) Damaged CouplingC) Fractured ShaftD) Melted Rubber Coupling

Examples of Damaged Shafts and Couplings


Excessive torsional vibration and resonance leads to damaged crankshafts, couplings, gears, auxiliary equipment, and more. Repair costs to such equipment can easily exceed $1,000,000 in parts, labor, and downtime. Over 80% of all torsional systems we analyze require system modification during the design stage to reduce the risk of failures.

Applications requiring a Torsional Vibration Analysis, or Torsional Study

  • Reciprocating Gas Compressors
  • Screw Compressors
  • Plunger & Centrifugal Pumps
  • Centrifugal compressors
  • Engines

 

Scope

Modal Analysis

  • Generate the mass elastic model for the entire drive train
  • Calculate the torsional natural frequencies

Forced Response Analysis

  • Calculate the vibratory torque acting on the system
  • Perform the forced response analysis to assess torsional vibration and dynamic stress amplitudes

To avoid torsional resonances and excessive torsional vibration we recommend changes such as, but not limited to:

  • Coupling size
  • Flywheel installation
  • Detuner installation
  • Limiting operating conditions
  • Material changes to the shafts
 FEA model of a crankshaft

Features in BETA's Torsional Studies

 

Application & Technical Support

API Compliant Studies (Including but not limited to 613, 618, 671, and 684)

 

Customer Benefits

  • Avoid catastrophic failures of crankshaft components and associated downtime.
  • Provide appropriate coupling selection for specific applications
  • Reduced maintenance and operating costs
  • Maximized unit availability
 

BETA Advantages

  • Comprehensive evaluation of the entire range of operating conditions plus upset conditions – not just the assumed "worst case." This improves system reliability and avoids the chance of design errors
  • BETA’s tolerance band analysis improves accuracy and minimizes risk. This technology evaluates the risk and design impact due to the tolerances of key input parameters. BETA’s approach reduces the risk of failures and avoids unnecessarily expensive torsional solutions
  • BETA has an extensive database of engine, motor, compressor and coupling information – resulting in faster and more accurate analysis
  • Our system approach focuses on the entire package including engine, driver, coupling, etc. This approach is more comprehensive and accurate compared to services that focus primarily on the engine (or compressor)
  • Extensive database of system solutions
  • Leading expert in reciprocating machinery applications (compressors and engines) 
  • Dedicated torsional support team that can provide fast, efficient, and high quality designs

 

 

Tips for Improved Torsional System Design

A TVA should be performed for:
  • Any new driver or compressor combination
  • Any change in compressor configuration (different cylinders) or significant changes in operating conditions (pressures, cylinder loading)
  • Different motor (same frame rarely means same rotor inside)
  • Drive trains experiencing failures
  • VFD applications
  • Critical applications
  • A field assessment is recommended to confirm torsional vibration and dynamic stresses on sensitive and critical systems.

FEA model of a motor rotor core FEA model of spider bars FEA model of a fan

Example of Torsional Modeling Capacity for Design Studies (Motor Rotor Core with Spider Bars and Fan)