L-0 Blade FATT value for material 2

[vali1]

I have a question:

What is the FATT value for steel used on Last Stage L-0 Blade-Low Presure Turbine?
What is the temperature value to be chosen? How down below the operations teperatures?

Thank you,
Vali

 

[vali1]

I asked this because I have some problem with such kind of blade. Fracture right below the stelite plate brazed on.
After a very short period of work an blade failed.After the problem was solved another blade failed. The same condition

 

[byrdj]

I'm not sure, but I though the L-0 blades concern was over temperature.

The main problem I recall overhearing bucket repair engineers mention was resonance tuning. I wish I could think of the chart calulation name they reffered to.

I think the unit I recall assisting disassemble started threwing buckects after the originals were replaced for wear about every 6 months for a couple years before a modified detuned bucket was made and installed

 

[metengr]

The last stage blades on steam turbines can be a range of materials from 12%Cr (403 ss) to 17-4 PH material. The FATT at 50% flat fracture for the LSB and for that matter any stage on the LP is below room temperature.

From what you describe the failure is probably fatigue crack propagation that initiated from the edge of hardened base material caused by brazing Stellite strips. I have seen this before, where brazing is not properly controlled and the blade base material locally hardens. Any type of notch or stress riser in this hardened material will result in crack initiation.

 

[vali1]

Thank you for the messages.
But in order to prove to client I need a value for the FATT. So he can compare with the value obtained for the blade material.
And, I hope it is the last problem with this stage, I have another damage: another blade is broke. But this time is above rooth, where starts aerofoil.
Any suggestion is wellcomed

 

[metengr]

vali1;
You have a potentially serious problem here. My professional advice to you is to stop, and have a metallurgical analysis performed of the failed blade. This is not an FATT issue, this sounds more like a high cycle fatigue damage related to blade material/design problem. I can't provide any more help to you until you get a failure analysis done ASAP. Don't get too far in over your head.

 

[rmw]

I agree with metengr. This is a problem for the experts. Have you ruled out other causes; abnormal operation, rubbing, FOD, etc?

rmw