Clasification Society Rulefinder 2016 - Version 9.25
Clasification Society Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, January 2016 - Part 4 STEEL UNIT STRUCTURES - Chapter 7 Watertight and Weathertight Integrity and Load Lines - Section 4 Watertight integrity |
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![]() Section 4 Watertight integrity4.1 Watertight boundaries4.1.1 All units are to be provided with watertight bulkheads, decks and flats to give adequate strength and the arrangements are to suit the requirements for subdivision, floodability and damage stability. In all cases, the plans submitted are to clearly indicate the location and extent of the bulkheads. In the case of column-stabilised drilling units, the scantling of the watertight flats and bulkheads are to be made effective to that point necessary to meet the requirements of damage stability and are to be indicated on the appropriate plans. 4.1.2 The number and disposition of watertight bulkheads are to comply with Pt 4, Ch 3, 5 Number and disposition of bulkheads. 4.1.3 The strength of watertight subdivisions are to comply with Pt 4, Ch 6, 7 Bulkheads. 4.1.4 Ship units and other surface type units are to be fitted with a collision bulkhead in accordance with Pt 3, Ch 3, 4.2 Collision bulkheadof the Rules for Ships. 4.2 Tank boundaries4.2.1 Deep tanks for fresh water, fuel oil or any other tanks which are not normally kept filled in service are, in general, to have wash bulkheads or divisions. 4.2.2 Tank bulkheads and watertight divisions are to have adequate strength for the maximum design pressure head in normal operating and damage conditions and the scantlings are to comply with Pt 4, Ch 6, 7 Bulkheads. 4.3 Boundary penetrations4.3.1 Where internal boundaries are required to be watertight to meet damage stability requirements, the number of openings in such boundaries is to be reduced to the minimum compatible with the design and proper working of the unit. 4.3.2 Where piping, including air and overflow pipes, ventilation ducts, shafting, electric cable runs, etc. penetrate watertight boundaries, arrangements are to be made to ensure the watertight integrity of the boundary. Details of the arrangements are to be submitted for approval. 4.3.3 No openings such as manholes, watertight doors, pipelines or other penetrations are to be cut in the collision bulkhead of ship units and other surface type units, except as permitted by Pt 5, Ch 13, 3 Drainage of compartments, other than machinery spaces and Pt 5, Ch 13, 4 Bilge drainage of machinery spaces of the Rules for Ships. 4.3.4 Where pipelines or ducts serve more than one compartment, satisfactory arrangements are to be provided to preclude the possibility of progressive flooding through the system to other spaces in the event of damage, see also Pt 4, Ch 7, 3.2 Damage zones. 4.3.5 Where piping systems and ventilation ducts are designed to watertight standards and are suitable for the maximum design pressure head in damage conditions, they are to be provided with valves at the boundaries of each watertight compartment served. 4.3.6 Ventilation ducts which are of non-watertight construction are to be provided with valves where they penetrate watertight subdivision boundaries. 4.3.7 Where valves are provided at watertight boundaries to maintain watertight integrity in accordance with Pt 4, Ch 7, 4.3 Boundary penetrations 4.3.5 and Pt 4, Ch 7, 4.3 Boundary penetrations 4.3.6, these valves are to be capable of being operated from a pump-room or other normally manned space, a weather deck, or a deck which is above the final waterline after flooding. In the case of a column-stabilised unit, this would be the central ballast control station. Valve position indicators should be provided at the remote control station, weather deck or a normally manned space. 4.3.8 For self-elevating units, the ventilation system valves required to maintain watertight integrity should be kept closed when the unit is afloat. Necessary ventilation in this case should be arranged by alternative approved methods. 4.4 Internal openings related to damage stability4.4.1 The requirements for the operation, alarm displays and controls of watertight doors and hatch covers and other closing appliances are given in Pt 7, Ch 1, 9 Riser systems. 4.4.2 Internal access openings fitted with appliances to ensure watertight
integrity, are to comply with the following:
4.4.3 Internal openings fitted with appliances to ensure watertight integrity,
which are to be kept permanently closed while afloat, are to comply with the
following:
4.5 External openings related to damage stability4.5.1 Where watertight integrity is dependent on external openings which are
used during the operation of the unit while afloat, they are to comply with the
following:
4.5.2 Where watertight integrity is dependent upon external openings which are permanently closed during the operation of the unit while afloat, such openings are to comply with the requirements of Pt 4, Ch 7, 4.4 Internal openings related to damage stability 4.4.3. 4.5.3 External watertight doors and hatch covers of limited size which are used while afloat may be accepted below the worst damage waterline, including wind heel effects, provided they are on or above the freeboard deck and the closing appliances comply with the requirements of Pt 4, Ch 7, 4.4 Internal openings related to damage stability 4.4.2 and Pt 4, Ch 7, 4.4 Internal openings related to damage stability 4.4.2. 4.6 Strength of watertight doors and hatch covers4.6.1 The symbols used in this sub-Section are as follows:
4.6.2 Closing appliances for internal and external openings are to have scantlings in accordance with this sub- Section and are to satisfy the requirements of Pt 4, Ch 7, 4.4 Internal openings related to damage stability and Pt 4, Ch 7, 4.5 External openings related to damage stability respectively. 4.6.3 In general, watertight closing appliances are to be designed to withstand the design pressure head from both sides of the appliance unless the mode of failure based on the damage stability criteria can only result in one-sided pressure loading. 4.6.4 The thickness of plating, t, subjected to lateral pressure in damage conditions is to be not less than:
t = 0,0048s
4.6.5 The section modulus, z, of panel stiffeners fitted in one direction and edge stiffeners is not to be less than:
z = 0,0065s k
The section modulus of secondary panel stiffeners may also be determined from the above formula, but doors with stiffeners designed as grillages will be specially considered. 4.6.6 The moment of inertia, I, of edge stiffeners is in general not to be less than:
I = 0,8 4.6.7 Securing devices for closing appliances are to be designed for water pressure acting on the opposite side of the appliance to which they are positioned, see also Pt 4, Ch 7, 4.6 Strength of watertight doors and hatch covers 4.6.3. 4.6.8 The strength of the bulkhead and deck framing in way of watertight closing appliances is to comply with the requirements of Pt 4, Ch 6, 7 Bulkheads. 4.6.9 Watertight closing appliances are to be hydraulically tested in accordance with the requirements of Pt 3, Ch 1, 8.3 Trial trip and operational tests 8.3.1 in Pt 3, Ch 1, 8 Inspection and workmanship of the Rules for Ships. In general, the test is to be carried out before the appliance is fitted to the unit. The test pressure is to be applied separately to both sides of the appliance, see also Pt 4, Ch 7, 4.6 Strength of watertight doors and hatch covers 4.6.3. 4.6.10 After installation in the unit, watertight closing appliances are to be hose tested in accordance with the requirements of Pt 3, Ch 1, 8.3 Trial trip and operational tests 8.3.1 in Pt 3, Ch 1, 8 Inspection and workmanship of the Rules for Ships, and functional tests are to be carried out to verify the satisfactory operation of the appliance, its control and alarm functions, as required byPt 7, Ch 1, 9 Riser systems. 4.7 Weathertight integrity related to stability4.7.1 Any opening, such as an air pipe, ventilator, ventilation intake or outlet, non-watertight sidescuttle, small hatch, door, etc. having its lower edge submerged below a waterline associated with the zones indicated in (a) or (b), is to be fitted with a weathertight closing appliance to ensure the weathertight integrity, when:
![]() Figure 7.4.1 Minimum weathertight integrity requirements for column-stabilised and tension-leg units4.7.2 External openings fitted with appliances to ensure weathertight integrity, which are kept permanently closed while afloat, are to comply with the requirements of Pt 4, Ch 7, 4.4 Internal openings related to damage stability 4.4.3 and Pt 4, Ch 7, 4.4 Internal openings related to damage stability 4.4.3. 4.7.3 External openings fitted with appliances to ensure weathertight integrity, which are secured while afloat are to comply with the requirements of Pt 4, Ch 7, 4.4 Internal openings related to damage stability 4.4.2 and Pt 4, Ch 7, 4.4 Internal openings related to damage stability 4.4.2 . |
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