SECTION 1 Materials

101. General

All materials are to terial standard.

be suitable for their intended service conditions and defined by recognized ma-

102. Materials of structural steels

Selection of structural steel materials associated with drilling structures is to comply with the fol- lowing requirements.

1. Structural steels utilized for drilling structures are considered to be primary structural members or secondary structural members specified in Ch 3 of the Rules.

2. Steel for plates, shapes and structural pipe sections is to be in accordance with requirements of API RP 2A-WSD or Ch 3 of the Rules.

3. Where toughness is to be considered in material selection, the toughness testing criteria required in Pt 2, Ch 1 of Rules for the Classification of Steel Ships are to be met as a minimum for the principal structural load-bearing components of derricks, masts and burner booms. If there are more stringent requirements imposed in the application of API RP 2A-WSD or API Spec 4F, then these requirements are to be applied.

4. Bolts and nuts are to have corrosion characteristics comparable to the structural elements being joined and are to be manufactured and tested in accordance with recognized material standards.

103. Materials of drilling equipment

Materials associated with drilling equipment and components is to comply with the following requirements.

1. Materials for drilling and well control equipment are to be selected in accordance to the applicable design codes with consideration to toughness, corrosion resistance, weldability and to be suitable for their intended service conditions.

2. All materials are to be defined by recognized standards.

3. Materials for drilling and well control equipment are categorized as follows.

(1) Mechanical load-bearing component

(2) Pressure-retaining equipment

(3) Piping under pressure load and external loads

4. Materials associated with drilling equipment or components are also to comply with the following specific criteria.

(1) Material Properties

To determine the suitability of a material to withstand design stresses, the ultimate tensile strength, specified minimum yield strength, elongation and reduction of area are to be specified in accordance with recognized material standards.

(2) Toughness

(A) Mechanical Load-Bearing Component

(a) Toughness testing for mechanical load-bearing components is to be performed in accord-

ance with relevant API or applicable recognized standards.

(b) Charpy V-Notch (CVN) impact testing is to be performed at the required temperature in the relevant API or applicable standard or the minimum design temperature, whichever is lower. For a specified MDT above 0°C, Charpy V-Notch impact testing is to be per- formed at 0°C.

(c)

(d)

The acceptance criteria of Charpy V-Notch impact testing is to be in accordance with the relevant API, ASME or applicable recognized standard.

Material for mechanical load-bearing components not covered by, or not in full com-

pliance with API standards or applicable recognized standards, the following Charpy V-Notch criteria applies.

(e) Other CVN criteria or alternative test data, such as crack-tip opening displacement (CTOD), nil ductility transition (NDT) temperature, or related service experience will be considered if submitted to the Society prior to manufacturing.

(f) It should be noted that additional requirements for toughness. The Society may require to

include additional toughness requirements of other national and international regulatory bodies in the scope of the design review and fabrication inspection where deemed nec- essary by the Society.

(B) Pressure-Retaining Equipment and Piping

(a) Toughness testing for pressure-retaining equipment and piping is to be performed in ac- cordance with the relevant API, ASME or applicable recognized standard.

(b) Charpy V-Notch (CVN) impact testing is to be performed at the required temperature in

the relevant API, ASME or applicable standard or the minimum design temperature, whichever is lower. For a specified MDT above 0°C, Charpy V-Notch impact testing is to be performed at 0°C.

(c)

(d)

The acceptance criteria of Charpy V-Notch impact testing is to be in accordance with the relevant API, ASME or applicable recognized standard.

Material for mechanical load-bearing components not covered by, or not in full com-

pliance with API standards or applicable recognized standards, the following Charpy V-Notch criteria applies.

(e) Other CVN criteria or alternative test data, such as crack-tip opening displacement (CTOD), nil ductility transition (NDT) temperature, or related service experience will be considered if submitted to the Society prior to manufacturing.

(f) It should be noted that additional requirements for toughness. The Society may require to include additional toughness requirements of other national and international regulatory bodies in the scope of the design review and fabrication inspection where deemed nec- essary by the Society.

(3) Materials used in well control equipment or components that can potentially be exposed to sour or H2S service are to be selected within appropriate limits of chemical composition, heat treat- ment and hardness to resist sulfide stress cracking. For this purpose, selection of material is to be guided by applicable part of NACE MR0175/ISO 15156(Materials for use in H2S containing environment in oil and gas production).

34 Guidance Relating to the Rules for the Classification of Mobile Offshore Drilling Units 2015

104. Corrosion Allowance

Where drilling systems are subjected to a corrosive or erosive environment, the design is to include corrosion allowances in accordance with the followings

1. The amount of additional material needed will be determined based on the predicted rate of corro- sion and the design service life of the component.

2. In the absence of any standard allowance or submitted information, a corrosion allowance of 1.6

mm is to be utilized.

105. Forming and welding of materials

1. Forming

Forming of materials utilized in drilling equipment and components are to comply with the follow- ing requirements.

(1) In general, for steel components, forming at temperatures around 205°C is to be avoided.

(2) Where degradation of properties is unavoidable, complete post forming heat treatment may be required.

(3) Suitable supporting data is to be provided to indicate compliance with the specified properties.

(4) For materials with specified toughness properties that are to be formed beyond 3% strain on the outer fiber, data are to be provided indicating that the toughness properties meet the mini-

mum requirements after forming. After straining, specimens used in toughness tests are to be

subjected to an artificial aging treatment of 288°C for one hour.

2. Welding

(1) Welding of drilling equipment and components is to be in accordance with Sec 2.

(2) Generally, weldments subject to H2S service are not to exceed a hardness of 22 Rockwell C in weld metal or heat-affected zone (HAZ), see NACE MR0175/ISO 15156.

106. Manufacturing process

1. Wrought and cast products are to be procured in accordance with written specifications that, in ad- dition to property requirements, specify the frequency, location, orientation and types of test specimens. Nondestructive examination is to be performed if required.

2. Rolled steels

Plates, shapes and bars may be supplied in the as-rolled, thermo-mechanically processed, normal- ized, or quenched and tempered condition, depending on the intended application.

3.

4.

107.

Steel forgings

(1) Requirements in Pt 2, Ch 1, Sec 6 of Rules for the Classification of Steel Ships is to be applied, except that a forging reduction ratio is to be not less than 3:1.

(2) Where a net change in the cross section does not occur during a portion of the forging oper-

ation, the hot working ratio representing that portion will be evaluated as a complement to the forging reduction ratio.

Castings

(1) In general, cast products are to be supplied in a heat-treated condition. Samples for testing are to be taken from integrally cast coupons or appropriately designed separately cast coupons.

(2) These coupons are to be subjected to the same heat treatment as the casting.

Sealing materials

1. Elastomeric sealants

(1) Materials used for sealing are to be suitable for the intended operating pressures and temperatures.

(2) Age-sensitive materials for critical components are to have a defined storage life and be identi-

fied in storage as to month and year of manufacture.

2. Ring joint gaskets

(1) Ring joint gaskets are to be of soft iron, low carbon steel or stainless steel, as required by the

Guidance Relating to the Rules for the Classification of Mobile Offshore Drilling Units 2015 35

design standard.

(2) Gaskets that are coated with a protective coating material such as fluorocarbon or rubber for shipment and storage are to have the coatings removed prior to installation.

108. Traceability of the products and materials

All materials used for major mechanical components and pressure-retaining equipment are to be fur- nished with documentation that states the process of manufacture. The manufacturers are responsible for maintaining this documentation on file and, upon request, are to provide this information to the Society.

1. Certified materials test report

(1) Chemical and mechanical properties for each heat

(2) Heat treatment temperatures and time at temperature

(3) Charpy impact values and temperatures

(4) Hardness test readings (as applicable to NACE MR0175/ISO 15156)

2. Manufacturing processes

(1) Welding records (including welding procedures specification(WPS) and Qualification)

(2) Post weld heat treatment

(3) Non-destructive examination results

(4) Hardness test results (as applied to NACE MR0175/ISO 15156)

(5) Dimensional check results

(6) Hydrostatic pressure tests