Objectives 1. To understand underlying concepts i.e. relationship between NG-18 surface flaw equation and API 579 approach
2. To have a feel of how much margin you actually have (Again….Yes!) Most important objective of this course!!!
Outline 1.
Objectives
2.
Major concerns for thinning assessment
3.
Exercise: TP moment
4.
Exercise: More exercise
5.
Exercise: Curve plotting
6.
Exercise: Defect length assessment
7.
Figure 5.6 from API 579
8.
Key lessons from Part 3
Major concerns for thinning assessment
Primary concern: • The component will rupture (DANGEROUS!!!!!) Flaw too large Flaw had eaten up reinforcement at major structural discontinuities (MSD)
Secondary concern: • The component will leak Remaining thickness too thin
Outline 1.
Objectives
2.
Major concerns for thinning assessment
3.
Exercise: TP moment
4.
Exercise: More exercise
5.
Exercise: Curve plotting
6.
Exercise: Defect length assessment
7.
Figure 5.6 from API 579
8.
Key lessons from Part 3
TP moment •
•
Given the following equations & diagram..
Express the remaining thickness ratio in terms of defect length i.e.;
s d tc
tmin tmm
Outline 1.
Objectives
2.
Major concerns for thinning assessment
3.
Exercise: TP moment
4.
Exercise: More exercise
5.
Exercise: Curve plotting
6.
Exercise: Defect length assessment
7.
Figure 5.6 from API 579
8.
Key lessons from Part 3
More exercise Given σyield = 30,000 psi & σUTS = 60,000 psi, determine remaining thickness ratio Rt (= tmm/tmin) for the following cases. Failure σfailure is limited to SE = 20,000 psi. Case 1: σflow = 1.1SE Case 2: σflow = σyield Case 3: σflow = 1.1σyield
0.5 1 2 3 4 5 6 10
Outline 1.
Objectives
2.
Major concerns for thinning assessment
3.
Exercise: TP moment
4.
Exercise: More exercise
5.
Exercise: Curve plotting
6.
Exercise: Defect length assessment
7.
Figure 5.6 from API 579
8.
Key lessons from Part 3
And even more exercises… •
Plot your results in the following chart: 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -0.1 -0.2 0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5 10
Outline 1.
Objectives
2.
Major concerns for thinning assessment
3.
Exercise: TP moment
4.
Exercise: More exercise
5.
Exercise: Curve plotting
6.
Exercise: Defect length assessment
7.
Figure 5.6 from API 579
8.
Key lessons from Part 3
And some even more exercises… •
Given the following data & the following diagram at the bottom; Piping strength data: σyield = 30,000 psi, σUTS = 60,000 psi Piping dimensions: Diameter Do = 36 inches, thickness tc = 0.75 inch Defect dimensions: depth d = 0.15 inch, length s = 10 inches Operating pressure: 340 psi
•
Using the plot from the previous exercise, evaluate if the defect length is acceptable for each case Case 1: σflow = 1.1SE (RSF=0.909)
Pass / Fail
Case 2: σflow = σyield (RSF=0.667)
Pass / Fail
Case 3: σflow = 1.1σyield (RSF=0.606)
Pass / Fail
s d tc
tmin tmm
And some more… •
Given the following data & the following diagram at the bottom; Piping strength data: σyield = 30,000 psi, σUTS = 60,000 psi Piping dimensions: Diameter Do = 36 inches, thickness tc = 0.75 inch Defect dimensions: depth d = 0.15 inch, length s = 10 inches Operating pressure: 435 psi
•
Using the plot from the previous exercise, evaluate if the defect length is acceptable for each case Case 1: σflow = 1.1SE (RSF=0.909)
Pass / Fail
Case 2: σflow = σyield (RSF=0.667)
Pass / Fail
Case 3: σflow = 1.1σyield (RSF=0.606)
Pass / Fail
s d tc
tmin tmm
Outline 1.
Objectives
2.
Major concerns for thinning assessment
3.
Exercise: TP moment
4.
Exercise: More exercise
5.
Exercise: Curve plotting
6.
Exercise: Defect length assessment
7.
Figure 5.6 from API 579
8.
Key lessons from Part 3
Figure 5.6 of API 579
Significance of parameters “How DEEP is the flaw?”
• Called thickness ratio • A measure of how much the flaw has encroached the minimum required thickness
“How BIG is the flaw?”
• The relative sizes of the flaw with respect to the component dimension (pipe/vessel/tank)
Outline 1.
Objectives
2.
Major concerns for thinning assessment
3.
Exercise: TP moment
4.
Exercise: More exercise
5.
Exercise: Curve plotting
6.
Exercise: Defect length assessment
7.
Figure 5.6 from API 579
8.
Key lessons from Part 3
Key lessons from Part 3 1. The curves used in API 579 have their origins from the NG-18 surface flaw equation 2. The most important length parameter for burst strength, under internal pressure loading, is the longitudinal extent of corroded area 3. Designs have margins – you must know where you are along the stress-strain curve 4. The most important considerations are rupture – most dangerous!
