Part 7 Surveys Chapter 1 Surveys During Construction Section 2 Surveys at Builder’s Yard – Hull Structure and Outfitting 7-1-2

16 ABS RULES FOR BUILDING AND CLASSING MOBILE OFFSHORE DRILLING UNITS . 2012

11.5 NDT of Surface-Type Drilling Units

Complete Joint Penetration (CJP) butt welds, tee welds and corner welds, within the midship 0.6L of a

surface-type drilling unit are to be specifically subjected to NDT during construction:

i) Intersections of butts and seams in the sheer strakes, bilge strakes, deck stringer plates and keel

plates

ii) Intersections of butts in and about moonpool corners on main deck and bottom platings

iii) In the vicinity of breaks in the superstructure

iv) Any temporary access closures or inserts in main structures

At the discretion of the Surveyor, NDT outside the midship 0.6L is to be carried out at random.

11.7 Type and Extent of NDT

The percentage of weld joint to be subjected to NDT and type of NDT carried out (e.g., Radiographic

Testing (RT), Ultrasonic Testing (UT), Magnetic Particle Inspection (MPI), Penetrant Testing (PT), Eddy

Current (EC) or Alternating Current Field Measurement (ACFM)) will depend on the design of the unit

and the calculated fatigue life of the joint.

Minimum extent of NDT to be carried out is shown in Table 1 of this Section. Volumetric NDT techniques

include RT and UT. Surface NDT techniques include MPI, PT, EC or AFCM.

Additional NDT may be requested by the Surveyor if the quality of fabrication or welds is not in accordance

with these Rules and applicable Standards.

11.9 NDT Personnel and Records

Builder’s NDT department is to be independent from other departments and not working for production.

All NDT records are to be reviewed by a Level 2 NDT technician and signed prior to review and

endorsement by the attending Surveyor.

All NDT records are to be properly maintained at least until the delivery of the drilling unit, and be

available to the Surveyor upon request anytime during construction.

11.11 NDT Acceptance Standards

Class A and Class B acceptance standards of the ABS Guide for Nondestructive Inspection of Hull Welds

will be applicable as follows:

i) Class A acceptance criteria are to be used for NDT of welds of hull structure categorized as

“Special Application Structure” or “Primary Application Structure” in accordance with 3-1-1/5.

ii) Class B acceptance criteria are to be used for NDT of welds of hull structure categorized as

“Secondary Application Structure” in accordance with 3-1-1/5 and other locations where Class A

acceptance criteria do not apply.

iii) Modified procedures and acceptance criteria are to be specified to reflect the application when

radiographic or ultrasonic inspection is specified for other type connections such as partial

penetration and groove type Tee or corner welds.

Part 7 Surveys Chapter 1 Surveys During Construction Section 2 Surveys at Builder’s Yard – Hull Structure and Outfitting 7-1-2

ABS RULES FOR BUILDING AND CLASSING MOBILE OFFSHORE DRILLING UNITS . 2012 17

TABLE 1 Nondestructive Testing* (NDT) of Steel Structure Welds (2012)

Structural Member Extent and Type of NDT

Special Application Structure

(Most Critical)

100% Volumetric NDT plus 100% Surface NDT all CJP welds, where welded plate

thickness is 5/16 inch (8.0 mm); and

10% MPI of all fillet welds, where plate thickness is 5/16 inch (8.0 mm).

Primary Application Structure

(Intermediate)

20% Volumetric NDT plus 100% Surface NDT of all CJP welds, where plate

thickness is 5/16 inch (8.0 mm); and

10% Surface NDT of all fillet welds, where plate thickness is 5/16 inch (8.0 mm).

Secondary Application Structure

(Least Critical)

Random Volumetric NDT of CJP welds and Surface NDT of fillet welds, only if

considered suspect by the attending Surveyor during construction.

* NDT procedures and acceptance criteria is to at least satisfy the ABS Guide for Nondestructive Inspection of Hull Welds.

13 Corrosion Protection

Unless otherwise approved, all steel work is to be suitably coated. Tanks or preload spaces intended for

salt water ballast are to have a corrosion-resistant hard coating on all internal surfaces.

13.1 Performance Standards for Protective Coatings (PSPC)

Where requested by the Owner, a unit with protective coatings which are verified by a Surveyor to be in

compliance with the ABS Guide for the Class Notation Coating Performance Standard (CPS), will be

assigned and distinguished in the Record with the class notation CPS.

15 Survey of Load Line

Every drilling unit is to have marks which designate the maximum permissible draft when the unit is in the

afloat condition. Such markings are to be placed at suitable visible locations on the structure, to the satisfaction

of ABS. On column-stabilized units, where practical, these marks are to be visible to the person in charge

of mooring, lowering or otherwise operating the unit.

The load lines are to be established under the terms of the International Convention on Load Lines. Where

minimum freeboards cannot be computed by the normal methods laid down by the Convention, they are to

be determined on the basis of compliance with the intact or damage stability requirements for afloat modes

of operation. The requirement that the draft of the unit not exceed the assigned load line may be considered

temporarily not applicable for bottom-supported units when raising, lowering or resting on the sea bed.

The requirements of the International Convention on Load Lines with respect to weathertightness and

watertightness of decks, superstructures, deckhouses, doors, hatchway covers, other openings, ventilators,

air pipes, scuppers, inlets and discharges, etc., are to be taken as a basis for all units in the afloat condition.

Upon satisfactory completion of the load line survey, an ABS LL-11D report is prepared by the Surveyor,

which is to be maintained onboard the unit. Upon satisfactory completion of the deadweight or inclining

experiment (as applicable) carried out in presence of the Surveyor, the builder’s stability report is to be

submitted to ABS for review and issuance of the load line assignment. The Surveyor is to verify load line

marking onboard the unit in accordance with the assignment.

17 Survey of Spaces (Damage Stability Criteria)

In assessing the damage stability of drilling units, as required by 3-3-2/1.3.2, the following extent of damage

is assumed. If damage of a lesser extent results in a more severe condition, such lesser extent is to be assumed.

During the survey of spaces, all piping, ventilating systems, trunks, etc., within the assumed damage area

are to be considered damaged. Positive means of closure are to be provided to preclude progressive

flooding of other intact spaces. Assumed damage conditions are as follows.