Design of Subsea Well Intervention Systems Using Non-ferrous Alloys

API RECOMMENDED PRACTICE 17G3 FIRST EDITION, FEBRUARY 2021

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Copyright © 2021 American Petroleum Institute

Foreword

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Contents

Page

1. Scope 1

2. Normative References 1

3. Terms, Definitions, Acronyms, and Abbreviations 2

   1. Terms and Definitions 2

   2. Acronyms and Abbreviations 2

4. Titanium Group 3

   1. Objective 3

   2. Design 4

   3. Galvanic Corrosion Considerations 6

   4. Fasteners 7

   5. Coatings 7

   6. Metallic Seal Ring 8

   7. Hardfacing and Metallic and Nonmetallic Coating 8

   8. Ductility, Toughness, and Hardness 8

   9. Fracture Mechanics 8

   10. Titanium Selection 9

   11. Manufacturing and Fabrication Requirements 10

   12. Nondestructive Testing 11

5. Aluminum Group 11

   1. Objective 11

   2. Design 12

   3. Galvanic Corrosion Considerations 15

   4. Coatings 16

   5. Hardfacing and Metallic and Nonmetallic Coating 16

   6. Valves and Actuators 16

   7. Ductility, Toughness, and Hardness 16

   8. Fracture Mechanics 16

   9. Aluminum Selection 17

   10. Manufacturing Requirements 18

   11. Nondestructive Testing 19

Annex A (informative) 20

Bibliography 21

Figures

1 Steel and Titanium Stress Joints vii

1. Stress-Strain Curves of Steel and Titanium 20

2. Stress-Strain Curves of Steel and Aluminum 20

Tables

1. Titanium Alloy Grades 4

2. Aluminum Alloys 12

v

Introduction

This document is not intended to be a standalone document from API 17G, rather a complement to current engineering practices set forth by API 17G with the inclusion of titanium and aluminum alloys.

It is important to note that certain design guidelines will supersede some API 17G requirements due to the material properties of titanium and aluminum. These guidelines will be noted and emphasized for clarity and to resolve conflicting design and test procedures between the API 17G3 and the parent document.

It is necessary that users of this recommended practice be aware that additional or different requirements that can better suit the demands of a particular service environment, the regulations of a jurisdictional authority, or other scenarios not specifically addressed in this recommended practice may be applied as required. This document is a recommended practice and it is not intended to replace sound engineering judgment.

One of the drivers for using titanium for the riser is the natural flexibility of titanium over traditional materials such as steel.

As demonstrated in Figure 1, from this side-by-side analysis of using steel vs titanium to construct a tapered stress joint above the well control package, you find the titanium stress joint provides a 50 % improvement in both wave height capacity (Hs) and vessel watch circle radius (vessel offset).

This analysis was based on an alloyed titanium stress joint example in simulated North Sea currents and wave conditions, along with a water depth of 80 m. All loads to the stress joint remain within the normal design limits.

9

8

7

6

Titanium MSJ

Hs

5

4

Steel TSJ

3

2

1

0

m/m 0

1

2

3

4

5

6

7

8

9

10

Vessel offset

Figure 1—Steel and Titanium Stress Joints

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Design of Subsea Well Intervention Systems Using Non-ferrous Alloys

1. Scope

   
   

   This recommended practice provides design guidelines for the use of non-ferrous materials in subsea intervention systems and components.

   
   

2. Normative References

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

API Specification 17D, Design and Operation of Subsea Production Systems—Subsea Wellhead and Tree Equipment

API Standard 17G, Design and Manufacture of Subsea Well Intervention Equipment

API Technical Report 17TR8, High-Pressure High-Temperature Design Guidelines

API Specification 20F, Corrosion-resistant Bolting for Use in the Petroleum and Natural Gas Industries

API 579-1, Fitness-for-Service

ANSI 1/NACE MR0175 2/ISO 15156 3 (all parts), Petroleum and natural gas industries—Materials for use in H2S-containing environments in oil and gas production

ASME Boiler and Pressure Vessel Code (BPVC) 4, Section VIII: Pressure Vessels; Division 2: Alternative Rules, 2019 Edition

ASME Boiler and Pressure Vessel Code (BPVC), Section VIII: Pressure Vessels; Division 3: Alternative Rules for Construction of High Pressure Vessels, 2019 Edition

ASME FFS-1, Fitness-for-Service

ASTM 5 E399, Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials

ASTM E647, Standard Test Method for Measurement of Fatigue Crack Growth Rates

ASTM E992, Practice of Determination for Fracture Toughness of Steels Using Equivalent Energy Methodology

ASTM E1290, Standard Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement

ASTM E1820, Standard Test Method for Measurement of Fracture Toughness

1 American National Standards Institute, 25 West 43rd Street, 4th Floor, New York, NY 10036, www.ansi.org.

2 NACE International, 15835 Park Ten Place, Houston, TX 77084, www.nace.org.

3 International Organization for Standardization, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Switzerland, www.iso.org.

4 ASME International, 2 Park Avenue, New York, NY 10016-5990, www.asme.org.

5 ASTM International, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428, www.astm.org.

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