Looking for reference text for FFS analysis

[deannoel]

Little out of my field of study here, so forgive me. I've been pegged to perform API 579 style Fitness-For-Service investigations on some old tanks we have on site. Low pressure LN2 tanks with little history outside of manufacturers data reports from the late 50s, and recent visual inspections. I have a generous timeline, access to funding for resources and training, and all of my reports will be reviewed by offsite PEs that performed these investigations when the volume was much lower. That said, I'm looking for some direction with background texts, and PV training courses if possible. I see the handbooks out there, but I'm looking for texts with all of the derivations and some problem sets I can work. The future holds FEA and FLAGRO analysis, but for now I want to work through all of stress derivations, fracture mechanics, and material science I can. I know this is an ME board, and if I was an ME I wouldn't be asking these questions, but I truely and humbly want to learn. I graduated in physics and did an applied masters in a different engineering field, so I respect the amount of work it took to learn your trade. I don't want magic formulas or anything for free, I'm just trying to steer my career towards FEA.
Right now I'm just going over old reports that determined a theoretical flaw that existed during the proof test and calculated the number of cycles it takes for that flaw to grow to critical size at MAWP. I just have an aversion to using equations I can't derive.
Thanks for reading, and TIA if you want to share some texts that got you where you are.

Dean

 

[nickelkid]

http://www.paulin.com/webinar/

I find the webinars on the above link very useful.

 

[jte]

Dean-

I admire your enthusiasm and hope that you have the endurance to follow through with your plans! If you were an ME without pressure vessel and piping experience, you'd be asking the very same questions, so don't be too humble. I envy your "generous timeline, access to funding for resources and training..." and it's a good idea that your work will be reviewed by offsite PE's with experience. Just venturing a guess, but sounds kinda like government funded rocket science to me...

I guess I'd recommend talking to these folks:

http://www.fitnessforservice.com/training/practitioner.html

They quite literally "wrote the book" on FFS.

Another good resource may be

http://www.becht.com/Content.aspx?cid=154&lvl=3

Not an easy task you're taking on, and my prediction is that you will in many cases be frustrated in searching for derivations to the formulas. Some relatively simplistic areas of FFS are still active research topics (e.g. pipe with local thin area under a compressive bending moment). Many of the formulas in 579 / FFS-1 are statistical curve fits to test data, rather than derived formulas. But, its a fun field if you are the type who enjoys this kind of pain...

jt

 

[deannoel]

Thanks JT. Your guess is spot on. Test complex with PVs of all shapes, sizes, and condition. I'm cutting my teeth on some old LN2 dewars. The combination of thin wall (1/4") to large diameter (~55") to low MAWP (65 psi) is giving me fits when it comes to determining remaining life. When I iteratively solve for the critical flaw size at proof load (105 psi) I get huge [>>0.25] starting flaw sizes. The fracture toughness just seems too high?

I was using a flaw aspect ratio (0.15) that makes the size of these flaws almost comical. That's where I just had to take a few steps back and start reading the fundamentals more. I picked up an early 80's version of Bednar's design handbook and I'm giving it the old physics workthrough.

Much thanks for the resources, and the kind words. The material science side of this scares me, but I can't worry about that right now.