deannoel
Mechanical
- Aug 8, 2008
- 4
I have the 2007 edition B&PV Div II, and the screening methods A and B seem straight forward enough. I'm working through a B analysis for some purchased vessels.
I have a maximum stress value at proof load (Smax), and I want to evaluate the vessel for 30 proof cycles over it's lifetime. In step 3 you determine the number of full range cycles for the design pressure. Since my stress at proof load (Smax) is more then the maximum allowable stress (S), it makes sense to me that instead of reading N(C1S) off of the fatigue curve table 3.F.10 I should calculate N(C1Smax). The numbers make sense to me, 475 cycles to MAWP compare to 171 to proof (cycles in which a fatigue analysis is reqired if exceeded).
Linearly expraploating between value on 3.F.10 is sufficient?
Now, when I read the analysis done per 1998 code (which I don't have), the numbers calculated seem unbelieveable. 1003324 = number of allowable proof cycles? I have two different reports, by PEs, that state that the vessels (similar) are good for 100000+ proof cycles. I can't get my head around that. Is there a huge difference in the codes between 1998 and 2007? The 1998 analysis referes to Table and Figures 5-110.2. Are these similar to 3.F.10?
Thanks in advance for any help you can give. I know I'm spraying questions.
Dean
I have a maximum stress value at proof load (Smax), and I want to evaluate the vessel for 30 proof cycles over it's lifetime. In step 3 you determine the number of full range cycles for the design pressure. Since my stress at proof load (Smax) is more then the maximum allowable stress (S), it makes sense to me that instead of reading N(C1S) off of the fatigue curve table 3.F.10 I should calculate N(C1Smax). The numbers make sense to me, 475 cycles to MAWP compare to 171 to proof (cycles in which a fatigue analysis is reqired if exceeded).
Linearly expraploating between value on 3.F.10 is sufficient?
Now, when I read the analysis done per 1998 code (which I don't have), the numbers calculated seem unbelieveable. 1003324 = number of allowable proof cycles? I have two different reports, by PEs, that state that the vessels (similar) are good for 100000+ proof cycles. I can't get my head around that. Is there a huge difference in the codes between 1998 and 2007? The 1998 analysis referes to Table and Figures 5-110.2. Are these similar to 3.F.10?
Thanks in advance for any help you can give. I know I'm spraying questions.
Dean