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API 17 – Subsea HPHT Discussion

PER 15K : “… should be used as a guide by the various API Subcommittees to develop future documents on equipment specifications for HPHT service. This report is not intended to replace existing API equipment specifications. … intended to illustrate accepted practices and principles that may be considered…”

HPHT Design Design Methodology has been in review and development for 5+ years and relies on ASME BPVC, Section VIII, Division 2 or 3.

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But no clear guidance when/where to switch from Div 2 – “Thin wall” to Div 3 – “Fracture Mech.” No industry (operator) guidance on Validation Testing.

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What constitutes “acceptance”? Is it Annex F or something tied to fatigue life/fracture mechanics?

Material Properties for pressure containing and pressure controlling components showing clarity on what’s needed in last 2 years.

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But no data on material ‘s HPHT properties published for widespread use.

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No clear path yet on seal technology.

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Most agree that for HPHT, E-P or Load-Limit + FAD (fracture mechanics) is way

to go. The question: When do we switch? The question: How do we balance between 6A which has 20k and 350 and 17D which has 15k and 350?

Elastic vs. Elastic-Plastic

Validation Testing

The question: When is Annex F testing is no longer valid? Is Annex F only valid for elastic design / functional testing? What level of testing is desired when fatigue design life is identified?

Materials Issues

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Main material use groups for HPHT

Pressure Containing Pressure controlling Fasteners Seals

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What pressure containing/controlling properties need to be met?

Tensile, Yield, modulus @ elevated temperatures Tensile/yield ratio da/dn @ temperature & environment K1C, J1C, K1SCC for ranking Fatigue life at temperature Affect of cathodic protection - hydrogen Seals - creep resistance Fasteners - stress relaxation