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Torsional Analysis

Torsional Analysis

Torsional Analysis

Dear All,

In case for torsional anaysis of gas compressor. The result of torsional analysis when you analysis whole system compare with separately analysis of each equipment(compressor, coupling ,engine). Result as same isn't it?

Please suggest

Best Regards

RE: Torsional Analysis

Torsional analysis is to be applied to the complete shaft line (driver end to driven end).
To me it does not make sense what you ask or question is poorly stated.

RE: Torsional Analysis

Hello RotaryW

For my question about torsional analysis of compressor skid.
Case 1: If run the separately analysis using only engine excitations, then run the analysis using only compressor excitations (and then combine the results).
Case 2: If run whole system (compressor-coupling-engine) excitation.
The result for 2 case, aren’t different? What is normal practice for analysis compressor skid. Because our vendor separate analysis for each equipment and then combine the result.

RE: Torsional Analysis

Torsional analysis is done for complete train. All the inertias are modelled as discs and then the analysis is carried out.
Common method to carry out is Holzer method. In this method arbitary vibration of radian is assigned to an extreme disk and the torque required to achieve these vibrations are calculated. To carry this analysis modelling of complete train will be required.

Besides, there are different excitation frequencies for eg: impeller vanes and cut water will have excitation. Motor will have excitation during starting and transient due to electrical faults. These all shall be considered when constructing campbell diagram.

Read below tutorial for more information.


In short torsional analysis shall be of all elements modeled together.

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