HPHT Flange Design Since the summer meeting: • Met five (5) times since summer meeting • Working on Flange Design Methodology (will be ready

to hand out draft by next summer meeting) • The task group all agreed that Bolting stress would be

limited to 83% of yield. Focus now is on Gasket Sealing Criteria (round table)

• Focus now is on Gasket Sealing Criteria (round table) • All analyst are getting same results for bolting and

flange stress

HPHT Flange Design Methodology: • Identified API PN 90-21 as a guideline to

defining a leakage criteria • Bolt Stress Criteria API 6A • Flange Stress Criteria ASME VIII LRFD • Fatigue ASME VIII • Ratcheting ASME VIII • Local Strain ASME VIII

HPHT Flange Design Moving Forward: • Continue drafting methodology • Fatigue, Ratcheting, Local Strain (still stands,

much of the time was still focused on bolting) • Collaborate with AWHEM to Design 18 ¾” 20K

Flange using methodology • Currently: pressure, bending and tension • Future work: temperature, extreme, survival

Gasket Sealing Criteria Round Table Discussion

PN 90-21 Contact Stress Jonathan Ellens NOV

or

Flange Separation Nigel McKie TechnipFMC

PN 90-21 Flange Study & Contact Stress Case Study

Jonathan Ellens NOV

Initial Theory of PN 90-21

“To prevent leakage, the contact pressure at the seat/seal interface must be above the internal pressure considering all factors such as pressure energization, external loads, and gasket geometry. In fact, contact pressure may need to be well above the internal pressure.”

Results of PN 90-21 • External Load Tests

• “For all flanges analyzed, the outer seal is predicted to remain effective until external loads large enough to yield the bolts are applied.” (Conclusion 3)

• Tested for tension, bending, and combination loads

Mesh Sensitivity Analysis • 7-1/16” – 10,000 psi*

• 1/12th model • Load order 1. Preload (50% YS) 2. Wellbore Pressure (10 ksi) 3. Tension (1,000 kips in 10 kip intervals)

• Observe when contact is lost on gasket ID seal

• Analysis run in Abaqus 6.14-1 • Contact modeled using surface-

surface, with surface smoothing

*Also studied in PN 90-21

Updated Contact Techniques

Contact Pressure Without Surface Smoothing

Contact Pressure With Surface Smoothing

Mesh Sensitivity Analysis Elements Nodes

248,803 272,845

Elements Nodes

125,747 140,978

Elements Nodes

32,717 39,187 Elements Nodes

43,799 51,764

250k 125k

43k 32k

Mesh Sensitivity Results PN 90-21 testing: Gasket ID seal lost at 10 ksi wellbore + 400 kips

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350 400 450 500

Cont

act P

ress

ure

(ksi

)

Tension Load (kips)

Contact Pressure vs TensionMesh Density Comparison - 7 1/16" - 10,000 psi Flange

Max Contact Pressure - 32k Elements

Max Contact Pressure - 43k Elements

Max Contact Pressure - 125k Elements

Max Contact Pressure - 250k ElementsPN 90-21 (1994) FEA Leakage Predicted: ~450 kips

Abaqus Mesh Sensitivity FEA (2017) Leakage Predicted: 410-427 kips

• Leakage criteria based on contact pressure is NOT mesh sensitive

• All 4 mesh densities predicted leakage of inner gasket seal within 7 percent of actual leakage (400 kips)

Mesh Sensitivity Conclusion

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350 400 450 500

Cont

act P

ress

ure

(ksi

)

Tension Load (kips)

Contact Pressure vs TensionMesh Density Comparison - 7 1/16" - 10,000 psi Flange

Max Contact Pressure - 32k Elements

Max Contact Pressure - 43k Elements

Max Contact Pressure - 125k Elements

Max Contact Pressure - 250k Elements

Abaqus Mesh Sensitivity Analysis (2017) Leakage Predicted: 410-427 kips

PN 90-21 Fatigue Testing

• Low Preload Test: 4-1/16-15,000 psi Flange

• Cycled 0 psi to 15,000 psi for ~10,000 cycles • Bolt make-up of 600-775 ft-lb (30-40%

normal preload value, 15-20% YS preload) • .011” flange face separation • No galling or damage after cycling

Flange Separation Nigel McKie TechnipFMC

3 1/16” 4 1/16”

5 1/8” Trendsetter

7 1/16”

3 1/16” 4 1/16”

5 1/8” Trendsetter

7 1/16”

Service Criteria • Robust Baseline Capabilities

Contact Pressure (PN 90-21) • Will “always” seal