Mass Elastic Data 1

[GaTechTheron]

All-

So caterpillar will not release any information on their diesel engines, and I must check skid packaged equipment against torsional critical frequencies. Does anyone know what information I need to supply to caterpillar? What is mass-elastic data? How is this incorporated into a dynamic system? Does anyone know how the transfer functions are determined, and combined?

I appreciate your time!

Thanks,
Theron

 

[BigInch]

You will need to get the masses and center of gravities of the static and rotating components of both the engine, the pump and gearbox from CAT. From those and, no doubt, assuming some of your own typical unbalanced force parameters and using the rotational acceleration rates of the engine you can determine the forces moments and torques that will be applied to the skid and foundation or other supporting structure. Those vary with RPM, so the forces over the range from 0 to operating speeds, plus trip (or the short-circuit loads in a motor driven case) need to be applied to the skid and most likely also the foundation to determine equipment distortion and vibration amplitudes expected for the system. The elastic properties of the equipment is normally neglected in the provision of any resistance to distortion. The skid of most pump-engine frames will only need to be sufficiently rigid to ensure shipping, handling and installation distortions are limited to acceptable levels. Afterward, the skid should be properly bolted to the foundation to ensure that the skid and foundation/support et al act together to resist distortion and vibrations from operating loads. The basics of the required analysis can be found in texts covering dynamic of foundations. Google "dynamics of machine foundation systems" for a selection of books on the subject. This one looks promising,

http://www.concrete.org/GENERAL/ACI 351.3R(04)-Foundations-for-Dynamic-Equipment.pdf

http://virtualpipeline.spaces.live.com