1. API 20K Flange Design Task Group API SC6 Task Group
Date: June 26, 2008.

2. Design Analysis Procedure
Yes No
Design Verification
Design meets
Static Load
requirements
Redesign
Design Validation
Testing
Fatigue Analysis
Fatigue life
Sealability Analysis
Design Flange
Functional Design Specification
Static Loads per Task Group Consensus
Dynamic Loads-TBD

3. Bolt Diameter Estimation
Bolt Diameter Based on Internal Pressure + Gasket Load and 20 No. bolts
(Estimate purposes only, Bolt Strength > 4” Dia & Temp Derating not included)
Bolt Grade B7 L7
B7M
L7M
A453 Gr.660
120K yield
135K Yield
>2.5 Dia, Yield Strength, psi
95000
80000
Test Pressure Condition, Bolt Dia (Bolt Stress at 83% Sy)
4.75
5.25
4.25 4
Observation: Large Bolt Diameter.
Concerns/Design Considerations:
1. For High Strength Bolts-Tapped Hole depth need to be adjusted for material yield differences.
Availability of bolt material with uniform cross sectional properties.
Ability to achieve uniform make-up through applied torque.
Larger Flange OD. Increase in equipment weight. Increased cost.
Monolithic equipment design: Increased Handling weight & Machining Cost.

4. Alternate Bolt Materials
Higher Strength, >120 to 130 ksi yield may be needed
Higher than 120 Yield Strength Inconel 718 not included in API 6A ksi/150 ksi may be included in next revision.
Inconel 925 is being considered by NACE
Alloy bolting, hardness 35 Rc/strength is limited due to Hydrogen Embrittlement when connected to C P protection

5. BX-164 Seal Ring Gasket
At Make-up condition entire gasket(316 S.S,) cross section yields
Gasket leakage concerns: (a) Cyclic loads, (b) At high temperature
New Cross section to be designed. (Reference: R. Eichenberg’s method.) New Cross section is under development.
Design guidelines & Test protocol for Gasket needs to be established.
Concerns: Cost of testing . Material Selected will verify performance of that material.

6. BX-164 Seal Ring Gasket Design Parameters Check per Eichenberg Method
API 6A Dimensions
Ring No.
Bore Dia
Max Bore
Pressure Rating
Height
Width B
B max P H A
BX164
18.75
18.78
10K-15k
1.185
0.968
Eichenberg Design parameters checked
10ksi WP
15ksi WP
20ksi WP
Ring No.
Bore Dia
Ht of Gskt
Width of Gskt B
BX164
18.75
1.170
0.968
1.185
1.368

7. Hydril 18-3/4” 20 ksi Flange Design (Preliminary)
Stress Calculations Method: ASME Section VIII, Division 2, Appendix 3

8. Flange Design API 6A Flange Design: Reference: API TR 6AF2
ASME Methodology, ASME Section VIII, Div2, Appendix 4
Design Allowable per API 6A, Based on Tresca Theory (Stress Intensity): For API 75K Material
Working Pressure: Sm = (2/ 3)*Sy
Test Pressure: ST = (0.83)* Sy
Bolt Allowable: API 6A:
83 % of Yield, Max Stress,
Make up load 50% of Sy
ASME Method, Section VIII, Div2, 2007 Edition:
Sm = Lower of (2/ 3)*Sy or ST = TS/2.4
Bolt Hydrostatic Pressure: Sbm = 0.95 Sy
Sbm + Sbb = lower of 1.43 SY or 2.43 SY-1.5Sbm

9. Summary Bolt Size affects flange OD.
Need higher strength bolt material
Deepwater application requires considerations for affects of CP protection and potential exposure to well bore fluid when insulated,
Bolting Allowable being reviewed. Recommendation to follow.
BX-164 Gasket is inadequate. New Gasket is needed.
Material selection for subsea use may qualify only one gasket material
Flange Design Method/Allowable being reviewed. Recommendation to follow.
API 6A + ASME Sect VIII (Edition referenced in API 6A) or
ASME Sect VIII, 2007 Edition

10. Mission Statement and Deliverables
To design a standardized 18-3/4”-20K Flange for deepwater application and analyze the flange capabilities under combination of internal and external structural loads at exposed temperatures.
Deliverables:
1. Integral Flange Dimensions
2. Blind Flange Dimensions
3. Design File
Design Method & Acceptance
criteria
Bolting
Design loads, Operating
envelope
Assumptions
Design Calculations
Flange Capability, FEA
Report
4. Flange Capabilities chart (Similar to API TR 6AF2)
5. Life Cycle Calculations
6. Material Requirements:
Refer to API 6A or specify per design
7. Quality Control Requirements