Section 1 General

101. Application

1. The requirements in the Rules are to be applied to the design, manufacture, installation and survey of mobile offshore units classed with the Society or intended to be classed under the Society. Mobile offshore units (hereinafter referred to as "units" in the Rules) as used herein are the units which are not intended for service at one particular offshore location and which are capable of moving for the intended offshore operation. However, for the restricted service units, special consid- eration may be given by the Society. The mobile offshore drilling units engaged in drilling oper- ation are to comply with Rules for the Classification of Mobile Offshore Drilling Units.

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. 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 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

the Rules and are subject to approval by

6. Floating structures, which are not for industrial purpose, such as floating hotel, floating restaurant and floating performing place, etc. are to be applied to Guidance for Floating Structures.

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.

Ch 1 General Ch 1

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

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

(1) 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.

(2) Determination of the adequacy of sea bed conditions, regarding bearing capacity, resistance to

possible sliding and anchor holding capability.

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. Load line

1. Any unit to which a load line is required, is to be assigned under the applicable terms of the

International Convention on Load Lines, 1966.(hereinafter referred as “ICLL” in the Rules)

2. All units other than those specified in Par 1 are to have load line marks which designate the max- imum permissible draft when the unit is in the afloat condition.

3. Load line markings are to be placed at suitable visible locations on the structure to the satisfaction of the Society. These marks, where applicable, are to be visible to the person in charge of moor- ing, lowering or otherwise operating the unit.

4. The permissible draught is to be established on the basis of meeting the applicable stability and structural requirements as set forth herein for afloat modes of operation, with such seasonal allow-

Ch 1 General Ch 1

ances as may be determined.

5. In no case is the draught to exceed that permitted ICLL.

6. A load line, where assigned, is not applicable to bottom-supported units when resting on the sea bed, or when lowering to or raising from such position.

7. Self-elevating Units and Surface Type Units

For self-elevating units and surface type units, the load line is to be accordance with not only Par

1 through 6 but also following requirements.

(1) Freeboard of the units is to be assigned in accordance with ICLL after confirming that the hull structure has a sufficient strength for the draft corresponding to the freeboard assigned. Freeboard of units which cannot be assigned in accordance with ICLL due to special forms of units, however, is to be assigned in accordance with the requirements in Ch 4, 6 and 7 at floating condition.

(2) Where moonpools are arranged within the hull in open communication with the sea, the volume of the moonpool should not be included in calculation of any hydrostatic properties.

(3) Where the moonpool has a larger cross sectional area above the waterline at 85% of the depth for freeboard (depth for freeboard has the same meaning as defined in regulation 3 of the 1988

LL Protocol) than below, an addition is to be made to the geometric freeboard corresponding to the lost buoyancy. This addition of for the excess portion above the waterline at 85% of the

depth for freeboard is to be dealt with the following (A) to (C) as below for wells and

recesses.

(A) Where an enclosed superstructure contains part of the moonpool, deduction is to be made for the effective length of the superstructure.

(B) Where open wells or recesses are arranged in the freeboard deck, a corrosion equal to the

volume of the well of recess to the freeboard deck divided by the waterplane area at 85% of the depth for freeboard is to be made to the freeboard obtained after all other correc- tions, except bow height correction, have been made.

(C) In stability calculation, free surface effects of the flooded well or recess are to be taken in- to consideration.

(4) Where small notches or relatively narrow cut-outs at the stern of the unit, the same procedure

for correction described in (3) is to be carried out.

(5) Narrow wing extensions at the stern of the unit are to be considered as appendage. The appen- dages are not to be included in the calculation of freeboard length.

8. Column Stabilized Units

(1) The

(2)

freeboard of the unit are to be determined by the requirements of Ch 4, 6, 7 and Par 9.

(2) The enclosed deck structure of the if this unit is to be appropriate to the Society.

(3) The position of openings which cannot be closed in emergencies is not to be located below the deck structure of the unit.

9. Vertical distance between the wave crests and underside of deck structure

(1) Self-elevating Units

The unit is to be designed for a crest clearance of either 1.2 m , or 10 % of the combined storm tide, astronomical tide and height of the maximum wave crest above the mean low water level, whichever is smaller, between the underside of the unit in the elevated position and the

crest of the design wave. The crest elevation is to be measured above the level of the com- bined astronomical and storm tides.

(2) Column Stabilized Units

(A) Vertical distance between the lower surface of deck structure and wave crest is to be en- sured for all afloat modes of operation, taking into account the predicted motion of the unit relative to the surface of the sea.

(B) For on-bottom modes of operation, clearances are to be in accordance with those specified in (1).

Ch 1 General Ch 1

106. 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-

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 107., 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.

107. 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.