Section 1 General

101. Application

1. The requirements in the Rules are to be applied to the surveys, hull construction, equipment and machinery of mobile offshore drilling units. Mobile offshore drilling units (hereinafter referred to as "units" in the Rules) as used herein are units or vessels capable of engaging in drilling operations for the exploration for or exploitation of resources beneath the seabed such as liquid or gaseous hydrocarbons, sulphur or salt.

2. The requirements in the Rules are to be considered as minima by the Society. In addition, partic- ular National Governments may have regulations which might be in excess of these requirements.

3. The Society is prepared to offer assistance, upon the request of an Owner or designer, in evaluat- ing a specific design against published National regulations.

4. Other similar units/other special purpose units, which do not engaged in drilling operations but which have configurations and modes of operation similar to drilling units, may be considered for classification by the Society, on the basis of the requirements as found to be applicable, and the relevant rules. In addition, evaluation must be made of other possible loading condition peculiar to the type of unit under consideration. Calculations substantiating the adequacy of the design are to be submitted to the Society. Machinery and electrical installations, etc. for other special purpose units will be subject to approval by the Society, as found to be applicable.

5. The items listed below, where applicable, are covered by the Rules the Society.

- Material

- Structural strength

- Welding

- Stability, intact and damaged

- Weathertight/watertight integrity

- Temporary or emergency mooring equipment

- Jacking system

- Propulsion machinery, including shafts and propellers

- Steering gear and rudders

- Auxiliary machinery

- Pumping and piping systems, including valves

- Boilers and pressure vessels

- Electrical installations

- Protection against fire and explosion

and are subject to approval by

6. When drilling systems are classed by the Society upon request of the Owner, drilling to be comply with the Guidance. 【See Guidance】

systems are

102. Types of units

Units are classified into the following four groups depending upon their types.

(1) Self-elevating Units : Self-elevating unit is a unit having hulls with sufficient buoyancy to safe- ly transport the unit to the desired location, after which the hull is raised to a predetermined el- evation above the sea surface on its legs, which are supported by the sea bed. Equipment and supplies may be transported on the unit, or may be added to the unit in its elevated position.

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The legs of such units may penetrate the sea bed, may be fitted with enlarged sections or foot- ings to reduce penetration, or may be attached to bottom pads or mat.

(2) Column-stabilized Units : Column-stabilized unit is a unit which depends upon the buoyancy of

widely spaced columns for flotation and stability for all afloat modes of operation or in the raising or lowering of the unit, as may be applicable. The columns are connected at their top to an upper structure supporting the equipment. Lower hulls or footings may be provided at the bottom of the columns for additional buoyancy or to provide sufficient area to support the unit on the sea bed. Bracing members of tubular or structural sections may be used to connect the columns, lower hulls or footings and to support the upper structure. Operations may be carried out in the floating condition, in which condition the unit is described as a semisubmersible, or when supported by the sea bed, in which condition the unit is described as submersible. A semisubmersible unit may be designed to operate either floating or supported by the sea bed, provided each type of operation has been found to be satisfactory.

(3) Surface Type Units

(A) Ship Type Units : Ship type unit is a seagoing ship-shaped unit having a displacement type

hull or hulls, of the single, catamaran or trimaran type, which have been designed or con- verted for operations in the floating condition. The unit of this type has propelling machinery.

(B) Barge Type Units : Barge type unit is a seagoing unit having a displacement type hull or hulls, which have been designed or converted for operations in the floating condition. The unit of this type has no propelling machinery.

(4) Other Type of Units : Units other than those specified in (1) to (3), are to be in accordance with the relevant requirements in this Chapter and are to be at the discretion of the Society.

103. Exemptions

1. The Rules are not to be applied to the following items ;

(1) Structural details of industrial items used exclusively in drilling or related operations.

(2) Machinery, electrical and piping systems used exclusively for industrial purpose, except in so far as their design or arrangement may affect the safety of the unit.

(3) Determination of the adequacy of sea bed conditions, regarding bearing capacity, resistance to possible sliding and anchor holding capability.

However, when drilling systems are classed by the Society, drilling systems are to be comply with the Guidance.

2. The assessment of the required holding capacity, arrangement and operation of position mooring equipment and dynamic positioning equipment used for station-keeping activities in connection with the unit's operation is the responsibility of the Owner, and is not included in the Rules.

104. Equivalency and novel features

1. Alternative hull construction, equipment, machinery and their arrangement and scantlings will be ac- cepted by the Society, provided that the Society is satisfied that such construction, equipment, ma- chinery and their arrangement and scantlings are equivalent to those required in the Rules.

2. Units which contain novel features of design, with respect to buoyancy, elevating arrangements, structural arrangements, machinery, etc., to which the Rules are not directly applicable, may be classed, when approved by the Society on the basis that the Rules, in so far as applicable, have been complied with and that special consideration has been given to the novel features based on the best information available at the time.

105. Operating Booklet

An Operating Booklet is to be provided for each unit to the satisfaction of the Society, and its copy is to be submitted to the Society. The booklet is to include the following information, as ap- plicable to the particular unit, so as to provide suitable guidance to the operating personnel with regard to safe operation of the unit :

(1) General description of the unit and light ship data based on the results of inclining experiment of the unit, etc.

(2) Pertinent data for each approved mode of operation, including design and variable loading, envi-

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ronmental conditions, assumed sea bed conditions, draught, etc.

(3) The lowest temperatures of atmosphere and sea water assumed at the design stage.

(4) General arrangement showing watertight compartments, closures, vents, allowable deck loadings, etc.

(5) Hydrostatic curves or equivalent data.

(6) Capacity plan showing capacity of tanks, centre of gravity, free surface corrections, etc.

(7) Instructions for operation, including precautions to be taken in adverse weather, changing mode of operation, any inherent limitations of operation, etc.

(8) Plans and descriptions of the ballast system and instructions for ballasting. If permanent ballast

is to be used, the weight, location and substance used are to be clearly indicated.

(9) Piping diagrams of fuel oil transfer systems.

(10) Hazardous areas plan

(11) Fire control plan

(12) Arrangement of life-saving appliances together with escape routes.

(13)

Stability information in the form of maximum KG versus draught curve, or other suitable pa-

rameters based upon compliance with the required intact and damaged stability criteria.

(14) Representative examples of loading conditions for each approved mode of operation specified in 207., together with means for evaluation of other loading conditions.

(15) Diagrams of main and auxiliary wiring systems.

(16) Details of emergency shutdown procedures for electrical equipment.

(17) Identification of the helicopter assumed in the design of the helicopter deck.

106. Construction booklet

A set of plans showing the exact location and extent of application of different grades and strengths of structural materials, together with a description of the material and welding procedures employed, is to be placed aboard the unit. Any other relevant construction information is to be in- cluded in the booklet, including restrictions or prohibitions regarding repairs or modifications.