Why SPO flanges are so superior to ASME flanges regarding ... · PDF file• Warping of...
Transcript of Why SPO flanges are so superior to ASME flanges regarding ... · PDF file• Warping of...
Copyright © 2013 Freudenberg Oil & Gas Technologies
Why SPO flanges are so superior to ASME flanges regarding risk of leakage
Tor EriksenFreudenberg Oil & Gas
Technologies
Slide 2Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeWhy Leaks ?
2. Insufficient bolt preload (final tightening forgotten by reopening after testing)
3. Misalignment and insufficient sealing pressure ( low gasket factor)
1. Unauthorised opening when pressurised
4. Misalignment/excessive bolt preload and sealing pressure – gasket damage
5. Fatigue damage/ detoriation of seal from vibration
6. Fatigue damage/ detoriation of seal from variabel piping displacements due to temperature variations or external distortions e.g. hogging and sagging in floatingstructures
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N/AN/AN/A
N/A
Slide 3Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeWhy Leaks ?
8. Fatigue crack in bolts
9. Fatigue crack on flange material
7. Corrosion
10. Bolt relaxation from loads as outlined in paragraphs 5 and 6 above
11. Failure of threaded joint between bolts and nuts
12. Failure from inappropriate material quality in bolting, flanges or seals
N/AN/A
N/A
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Slide 4Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeWhy Leaks ?
2. Insufficient bolt preload (final tightening forgotten by reopening after testing)
3. Misalignment and insufficient sealing pressure ( low gasket factor)
1. Unauthorised opening when pressurised
4. Misalignment/excessive bolt preload and sealing pressure – gasket damage
5. Fatigue damage/ detoriation of seal from vibration
6. Fatigue damage/ detoriation of seal from variabel piping displacements due to temperature variations or external distortions e.g. hogging and sagging in floatingstructures
0+
N/AN/AN/A
N/A
Slide 5Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeUnauthorized opening when pressurised
� Does not happen at flange joints,which are not connected to valves, equipment, maintenance spools or blinds, e.g. in flanged joints along this flare header of the NORNE FPSO.
�The IX seal ring would start with a small leak during disassembly, thus providing a warning whistle before a hazardous leak would occur. Such pre-warning cannot be guaranteed for most of the gaskets used in ASME flanges.
�Most frequent: � Mix-up of equal branch connections to a manifold.� Misunderstanding / poor communication, not by purpose
How?
Slide 6Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeUnauthorized opening when pressurised
Well-bays• Typically large number of flanges and
valves, high pressure• Frequently modified offshore - new
wells on stream• Large number of leak sources
Mix-up and opening of any pressurised type of bolted joint may happen in a manifold system, but the compact flange offers other benefits here:
Compact Flanges for well-bays offers• Space saving – often critical in these areas• Significant weight savings• Improved safety and environmental
conditions due to gas tight, leak free and maintenance free connections
Slide 7Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeWhy Leaks ?
2. Insufficient bolt preload (final tightening forgotten by reopening after testing)
3. Misalignment and insufficient sealing pressure ( low gasket factor)
1. Unauthorised opening when pressurised
4. Misalignment/excessive bolt preload and sealing pressure – gasket damage
5. Fatigue damage/ detoriation of seal from vibration
6. Fatigue damage/ detoriation of seal from variabel piping displacements due to temperature variations or external distortions e.g. hogging and sagging in floatingstructures
0 +
N/AN/AN/A
N/A
Slide 8Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact Flange
Insufficient bolt preload
• Leaks from ASME flange joints at start up due to forgotten bolt tightening are highly represented in statistics on causes to leakage from flange joints
• If compact flanges are closed with no visual gap between the flanges at the outer rim, there must be a lot of preload from the bolting. (At least 2/3 of required preload is then applied to a SPO CF joint)
• It cannot be revealed by visual inspection if the bolts of an ASME flange connection have been tightened properly or if nuts have been finger tightened, only
Slide 9Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeWhy Leaks ?
8. Fatigue crack in bolts
9. Fatigue crack on flange material
7. Corrosion
10. Bolt relaxation from loads as outlined in paragraphs 5 and 6 above
11. Failure of threaded joint between bolts and nuts
12. Failure from inappropriate material quality in bolting, flanges or seals
N/AN/A
N/A
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Slide 10Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact Flange
Most leaks from corrosion will start slowly including all bolted joints.
Corrosion
ASME flanges� with flat sheet gaskets may release large amounts of fluid suddenly due
to gasket rupture when flange sealing areas get corroded, and result of this is bolt relaxation.
ASME RTJ flanges� may also start leaking suddenly from breakdown of a corroded seal ring.
SPO CF� The double barrier of the SPO CF makes corrosion to the seal ring virtually
impossible. Even if micro scratches on the heel surfaces hasled fluid pressure to the seal ring, the supply of corrosive fluid would be extremelylow.
� The seal ring of the SPO CF is much better protected against externalcorrosion than any seal or gasket suitable for ASME flanges.
Slide 11Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeWhy Leaks ?
8. Fatigue crack in bolts
9. Fatigue crack on flange material
7. Corrosion
10. Bolt relaxation from loads as outlined in paragraphs 5 and 6 above
11. Failure of threaded joint between bolts and nuts
12. Failure from inappropriate material quality in bolting, flanges or seals
N/AN/A
N/A
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Slide 12Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeFailure of threaded joint between bolts and nuts
• Dynamics in ASME flanged connections provides high risk of fatiguecracks at high local stress areas in the bolts.
• High fire loads may cause failure of bolt and nut connections in flangedconnections before bolt relaxation will result into a leak.
• Warping of large ASME flanges is frequent when tightening the bolts. Result is high stress on the first threads in the bolt to nut connectionbecause the nut will impose severe bending stresses to the bolt whenflange surface is not perpendicular to the bolt axis.
• The SPO CF is designed so that bending of bolts is impossible.
• SPO CF provides no dynamic load to the bolt and nut connections.
• The SPO CF can be protected from this scenario by simply using special fire nuts, while corresponding fire protection of an ASME flanged connection wouldrequire insulation of the complete assembly.
Slide 13Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeWhy Leaks ?
8. Fatigue crack in bolts
9. Fatigue crack on flange material
7. Corrosion
10. Bolt relaxation from loads as outlined in paragraphs 5 and 6 above
11. Failure of threaded joint between bolts and nuts
12. Failure from inappropriate material quality in bolting, flanges or seals
N/AN/A
N/A
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Slide 14Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeFailure from inappropriate materials
• Failure from inappropriate materials in flanges, bolting and seals is less likely when no component is subject to dynamic loads.
• Forgings for machining of SPO flanges and seal rings are subject to the most stringent requirements.
• Bolting materials shall satisfy the latest requirements in ASME VIII Div. 2
Slide 15Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeLeak limit comparisonExample 6” class 1500
• A 6” class 1500 bolted RTJ to ASME B16.5 shall be typically tightened to a total load of 1704 kN
• This gives an extra theoretical capacity of 512 kN axial load or 27kNm bendingmoment without leakage if flanges have infinite stiffness, i.e. no deformation! BothFEA and testing show severe deformations>>>>>>�
• The corresponding class 1500 compactflange joint shall be tightened to a total load of 2316 kN.
• This gives an extra capacity of at least 275 kN axial force or more than 18kNm bending moment for the tightness of the heel seal based on 1,5 x DP (ref. ISO 27509, clause 4.2)
Slide 16Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeLeak limit comparisonExample 6” class 1500
• This corresponds with an equivalent pressure of 550 bar. The tension force was then increased to 1975 kN until yield of bolting and pipe, but the joint was still tight!
• In a test performed by DNV in 2003 on a 6” class1500 CF to NORSOK L-005 in 316SS, the heelseal kept tight until a tension load of 750 kN and with an internal pressure of 258,6 bar.
Tension and Pressure test of 6” class 1500 CFC in 316SS, Oct. 2003
Slide 17Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact Flange
Risk level welded versus flanged joint
• Statoil and several other oil companies do not permit welding outsidepressurized habitats in process areas during production on offshore platforms.
• A DNV study for Statoil in 2005 concluded that habitat welding during production represent a risk to potential loss of life (PLL) of same magnitude as the precence of a standard ASME flange joint in service for 20 years.
• The SPO CF will significantly reduce risk of leakage, and thus reduce the PLL compared with ASME flanges as explained in this presentation.
• Report no/DNV Reg No.: / 12FQG2F-6, Rev 01, 2010-03-12,”Reliability Evaluation of SPO Compact Flange system” concludes that leak probability from the bolted joint itself may be less than from the adjoining girth welds to the pipe.
Slide 18Copyright © 2013 Freudenberg Oil & Gas Technologies
Reliability acc. to DNV report of March 2010
Leakage rate per year of a flange connection compared to piping and girth weld
SPO® Compact Flange
Slide 19Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact FlangeBolt load versus pressure
BoltLoad(alltogether)
Pressure
Sufficient to seal?
Typical curve for a large ASME flange connection
IX seal is pressure energized when heel faces are not sealing any more
SPO CF joint
ASME flange joint
Slide 20Copyright © 2013 Freudenberg Oil & Gas Technologies
SPO® Compact Flange
• A 16₺ class 2500 SPO CF joint with IX seal ring was qualified to
Shell MESC SPE 77/312*) leakage class A at 431 barg and
120oC in February 2011.
• An 8₺ 15,000psi SPO CF joint with HX seal ring was qualified to
Shell MESC SPE 77/312*) leakage class A at 1035 barg and
ambient temperature in Oct. 2011. (Test recordings were
lower than limit of reliable readings according to the Shell
specification)
Fugitive emissions - Examples
*) The accumulation technique in accordance with EN 1779, B3, as referenced in
Shell MESC SPE 77/312 of August 2010, was used.
The most stringent requirements to fugitive emissions have been met: