Slewing Ring Selection for Wind Turbines

[Farhad Hosseini]

Hi all,

I am working on the slewing rings used in the pitch system of wind turbines.
We have calculated the tilting moments and axial loads for the following load cases:
- nominal operational condition
- maximum operational condition
- maximum downtime condition
- extreme condition

A service factor of about 2 is also suggested for wind turbine application. My question is: which of the above mentioned tilting moments/axial loads must be multiplied by the service factor? All of them? or only the operational moments/forces?

Thanks

 

[Tmoose]

Double posting is frowned upon.
It usually is kind of confusing.

 

[rb1957]

what is the "service factor" supposed to be doing ?
"2" sounds like an impact load ? ie dynamic effects;
but "service loads" sounds like a fatigue rule of thumb (ie if your structure is good to double the typical loads then it should have infinite life) ?

another day in paradise, or is paradise one day closer ?

 

[Chpal1984]

If I remember correctly there are different load cases in IEC 61400 (including normal, extreme operational, extreme conditions etc as you list), each load case also has a partial saftey factors defined in the standard. Then you design to the highest load. Now I haven't heard of this 'service factor', is that just an extra factor that you apply? As with anything it depends how conservative you want to be. I would pick the highest axial and tilt loads and multiply by your service factor, then design to that (well unless it gives you a silly result)

 

[Farhad Hosseini]

The service factor supposed to consider the dynamic effects and shocks as an extra factor. But when we calculating the extreme conditions, our software considers the dynamic effects by itself. The IEC load factors (1.35 and 1.1 for different load cases) are considered as well. Therefore, I think only nominal loads should be multiplied by the service factor, not extreme loads.
On the other hand, in the catalog of many slewing ring manufacturers, they suggest service factors based on the application, but say nothing about which loads should be multiplied by their suggested service factor....

 

[Tmoose]

http://www.eng-tips.com/viewthread.cfm?qid=413349