Coupling Service Factor

The selection of a service factor for a coupling in a driven piece of equipment depends a lot on judgement as well as the amount of risk that the owner wants to take.

Recently, (early 2010)there was a significant steam turbine coupling failure at the Iranshahr power plant. Google some of these terms to see the devastating pictures.

It is my understanding the couplings for steam turbines attached to generators should be sized for the "fault to ground" case......which would generate the most amount of torque for the shaft.

Consult with your generator designer about this particular case.

Tell us more about what you are trying to accomplish.......

Thank you very much for your response, I failed to access the link you gave me. I would like to install a flexible coupling between generator and gearbox to compensate for difference in thermal growth. The two machines are sitting on different bases, gearbox on metal base and generator on concrete base. I am at a stage of specifying the coupling requirements.Is this a normal solution to my problem?

Dear Mr. Goldfrey,

Generally the Service Factor is 1.3, but some Designers recommend 1.5.

Thanks,

sdr710

General practice is to use 1.5.

But, I recommand to follow API 671 as the couplings for such a heavy duty machinery is always recommanded in compliance to API 671.

In addition, for the coupling selection for Turbo generator, Coupling and Shaft must be designed for Motor case operation of GENERATOR ALSO. This is a worst case and Torque must be very high.

I also recommnd to ask vendor to submit Transient torsional analysis and Torsional analysis for Complete Train.

With regards,

Nilesh.