Returning ChallengesPipeline Components

Carlos SiciliaPipeline Innovation Forum 2014Hvik, 27/03/14

Limit State Design for Submarine Pipelines

Good design codes DNV-OS-F101

Recommended Practices

JIPs

Company Guidelines

Even framework for problem specific reliability

assessment, e.g. used for UHB

Introduction

What about elements within pipeline system that

are not pipes?

Pipeline Components

Present in all systems

Introduction

PIP systems:

Bulkheads

Swaged joints

Inner pipe pull collars

General:

J-lay collars

Riser hang off

Flanges

Connectors

Corrosion monitoring

spools

Introduction

Other:

Tees

Wyes

Hot tap

Bends?

In-line structures?

Introduction

Introduction

J-lay Collar

End Bulkhead

In-line Pull-out Collar

What does DNV-OS-F101 say about this?

Design according to recognized codes with some

additional requirements

Pipeline Code

What does DNV-OS-F101 say about this?

At least same safety as the connecting pipeline/riser

section

The component shall be designed to accommodate

the loading from the connected pipeline section and

vice versa with appropriate safety

But how to even agree on Design / Test pressure?

Pipeline Code

ASME VIII, PD5500, EN13445-3

Background to Pressure Vessel Design Codes

Pressure Vessel Codes

S = min (SMTS/3.5, SMYS/1.5)

Basic approach:

Linear elastic stress analysis with factored loads

Linearize stresses

Separate Primary and Secondary stresses

Check against allowable values

Pressure Vessel Codes

Based on actual limit states:

Plastic collapse (gross plastic deformation)

Local failure (limit potential for fracture)

Collapse from buckling

Cyclic loading fatigue

Cyclic loading ratcheting

Sensible and all relevant aspects covered

Conceptually consistent with pipeline code

Pressure Vessel Codes

But is safety level consistent?

Material factor ~ 1.3 Load factor ~ 1.5

Is this too conservative?

Pressure Vessel Codes

Straight pipe Bending moment with design pressure

ScenarioDNV

LCC

EN-13445

Limit Moment Allowable Moment

No material

factor

With material

factor

No material

factor

With material

factor

Moment [kN/m] 542 580 446 387 297

Ratio to DNV 1.00 1.07 0.82 0.71 0.55

More advanced options:

Elastic perfectly plastic analysis

Full non-linear analysis with material hardening

Based on strain limits

Pressure Vessel Codes

Maximum Plastic Strain

Is the non-linear option enough?

Pressure Vessel Codes

High Loads (Buckle?)

Pressure Vessel Codes

Pressure Vessel Codes

S = min (SMTS/3.5, SMYS/1.5)