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When to Specify Torsional Analysis for Rotating Equipment

When to Specify Torsional Analysis for Rotating Equipment

When to Specify Torsional Analysis for Rotating Equipment

(OP)
Hi Everybody,

Requirement of Torsional analysis always confuses me while preparing rotating equipment data sheets (Pumps, Compressors etc.) I would like to know what is the criterion for specifying torsional analysis ?
Is this based on:
1) Break power ?
2) Driving Speed rpm ?
3) Variable speed machines (VFD) etc.?
4) Reciprocating equipment (Recip. compressor / Engine driven) etc.

Is there any Code or standard specifies or gives guideline on torsional analysis requirement. Experts pls help.[/b]

RE: When to Specify Torsional Analysis for Rotating Equipment

Add natural frequencies to your list.

RE: When to Specify Torsional Analysis for Rotating Equipment

We perform TVC's mainly for the marine industry, pump installations and generators. For propulsion installations, the rules are quite clear. for industry, isn't a lot covered by API rules?
In my opinion, it is always wise to perform a TVC. This is a relatively low cost check, and can help you to avoid many problems.

regards
rob

RE: When to Specify Torsional Analysis for Rotating Equipment

API 610 for Centrifugal pumps and API 617 for Centrifugal Compressors both have criteria and requirements for torsional analysis.

RE: When to Specify Torsional Analysis for Rotating Equipment

In addition to resonant frequency aspects, some specs are concerned with possible low cycle fatigue anywhere in the train whenever starting a heavy rotor etc "across the lines", or similarly, if some kinds of motor faults occur, causing brief periods of HIGH torque.

RE: When to Specify Torsional Analysis for Rotating Equipment

Gear driven machines & those machines with VFDs are more vulnerable. If you are concerned about the influence of dynamic torques in the drive train, then torsional analysis helps.

RE: When to Specify Torsional Analysis for Rotating Equipment

As a vague rule of thumb
When ever you have variable excitation it is best to have a torsional analysis done.

Variable excitation can come in many forms.
1.) Variable Loads (Stops, Starts, Dwells, Reverses)
2.) Variable Speeds (Transmissions, VFDs)
3.) Operational load excitation (functioning compressor cylinders)
4.) Operational power excitation (functioning cylinders in Engines)

When it comes to couplings we are always here to help.
WWW.PSCCOUPLINGS.COM

RE: When to Specify Torsional Analysis for Rotating Equipment

Variable loads may prove difficult, because a regulator may have a lot of influence here, and this requires a lot of variables a standard TVA program cannot cope with. In such a case, and if problems are expected or need to be avoided at all costs, I recommend a vibration measurement.

RE: When to Specify Torsional Analysis for Rotating Equipment

rob768,

Excellent Point ! ! ! When I think about torsional "analysis", it can come in the form of classical software analysis or physical measurement like you mentioned. Either way, "analyze" the system as oppose to just running it.

When it comes to couplings we are always here to help.
WWW.PSCCOUPLINGS.COM

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