DNVGL-OS-C301: Stability And Watertight Integrity
OFFSHORE STANDARDDNVGL-OS-C301Edition July 2015Stability and watertight integrityThe electronic pdf version of this document found through http://www.dnvgl.com is the officially binding version.The documents are available free of charge in PDF format.DNV GL AS
FOREWORDDNV GL offshore standards contain technical requirements, principles and acceptance criteria related toclassification of offshore units. DNV GL AS July 2015Any comments may be sent by e-mail to rules@dnvgl.comThis service document has been prepared based on available knowledge, technology and/or information at the time of issuance of this document. The use of thisdocument by others than DNV GL is at the user's sole risk. DNV GL does not accept any liability or responsibility for loss or damages resulting from any use ofthis document.
GeneralThis document supersedes DNV-OS-C301, July 2014.Text affected by the main changes in this edition is highlighted in red colour. However, if the changesinvolve a whole chapter, section or sub-section, normally only the title will be in red colour.On 12 September 2013, DNV and GL merged to form DNV GL Group. On 25 November 2013 Det NorskeVeritas AS became the 100% shareholder of Germanischer Lloyd SE, the parent company of the GL Group,and on 27 November 2013 Det Norske Veritas AS, company registration number 945 748 931, changed itsname to DNV GL AS. For further information, see www.dnvgl.com. Any reference in this document to “DetNorske Veritas AS”, “Det Norske Veritas”, “DNV”, “GL”, “Germanischer Lloyd SE”, “GL Group” or any otherlegal entity name or trading name presently owned by the DNV GL Group shall therefore also be considereda reference to “DNV GL AS”.Main changes July 2015 GeneralThe revision of this document is part of the DNV GL merger, updating the previous DNV standard into a DNVGL format including updated nomenclature and document reference numbering, e.g.:— Main class identification 1A1 becomes 1A.— DNV replaced by DNV GL.— DNV-RP-A201 to DNVGL-CG-0168. A complete listing with updated reference numbers can be found onDNV GL's homepage on internet.To complete your understanding, observe that the entire DNV GL update process will be implementedsequentially. Hence, for some of the references, still the legacy DNV documents apply and are explicitlyindicated as such, e.g.: Rules for Ships has become DNV Rules for Ships.Editorial correctionsIn addition to the above stated main changes, editorial corrections may have been made.Offshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 3Changes – currentCHANGES – CURRENT
CHANGES – CURRENT . 3CH. 1 INTRODUCTION . 7Sec.1Introduction . 71General .71.1 Introduction.71.2 Objectives .72Normative references .72.1 General .72.2 Reference documents .83Informative references .83.1 General .84Definitions .84.1 Verbal forms .84.2 Definitions .94.3 Abbreviations and symbols . 105Documentation .115.1 General . 11CH. 2 TECHNICAL PROVISIONS . 12Sec.1Stability. 121General .121.1 Scope . 122Determination of wind forces .122.1 Heeling moment curves . 123Determination of lightweight .143.1 Inclining test. 144Intact stability requirements .144.1 General . 144.2 Ship shaped units or installations. 154.3 Column stabilised units. 164.4 Self elevating units or installations . 164.5 Deep draught floating installations . 164.6 Cylindrical surface units. 165Damage stability requirements .175.1 General . 175.2 Ship shaped units or installations. 175.3 Self elevating units or installations . 185.4 Column stabilised units or installations and cylindrical surface units . 185.5 Deep draught floating installations . 195.6 Extent of damage – ship shaped, cylindrical and self-elevating units orinstallations . 205.7 Extent of damage – column stabilised units and deep draught floatinginstallations . 205.8 Chain lockers . 205.9 Machinery and machinery space openings . 215.10 Load line and draught marks . 215.11 Extent of watertight and weathertight closing of external openings. 21Offshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 4ContentsCONTENTS
Sec.2Watertight integrity, freeboard and weathertight closing appliances . 221General .221.1 Application. 222Materials.222.1 Technical requirements . 222.2 Supplementary classification requirements . 223Watertight integrity .223.1 General . 223.2 Internal openings . 233.3 External openings . 233.4 Strength of watertight doors and hatch covers. 233.5 Frame and bulkhead interface . 253.6 Operation and control of watertight doors and hatch covers. 264Weathertight closing appliances .264.1 General . 264.2 Weathertight doors . 274.3 Weathertight hatch coamings and covers . 274.4 Gaskets and closing devices . 284.5 Drainage arrangement . 284.6 Buckling check . 295Freeboard .295.1 General . 295.2 Self elevating units or installations . 305.3 Column stabilised units or installations . 306Ventilators and air pipes.316.1 General . 317Inlets, discharges and scuppers .317.1 Sea inlets and discharges in closed systems . 317.2 Discharges. 327.3 Scuppers . 328Side scuttles and windows.338.1 General . 339Testing of doors and hatch covers .339.1 Pressure testing of watertight doors and hatch covers . 339.2 Hose testing of watertight and weathertight doors and hatch covers . 339.3 Function testing of watertight doors and hatch covers. 3310 Closing arrangements for doors and hatch covers .3410.1 Description of waterlines (beach lines). 3410.2 Description of location of openings . 3410.3 Operation, indication and locking . 34CH. 3 CERTIFICATION AND CLASSIFICATION. 37Sec.1General . 371Introduction .371.1 Application. 372Design review .372.1 Documentation requirements . 372.2 Specific classification requirements . 37Offshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 5Contents5.12 Internal watertight integrity and subdivision. 215.13 Loading computers . 21
Certification of materials and components.373.1 General . 373.2 Certification requirements under this standard. 38Offshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 6Contents3
SECTION 1 INTRODUCTION1 General1.1 Introduction1.1.1 This offshore standard provides principles, technical requirements and guidance related to stability,watertight integrity, freeboard and weathertight closing appliances for mobile offshore units and floatingoffshore installations.The types of units and installations that are covered by this standard include:— ship shaped units— column stabilised units— self elevating units— deep draught units.Guidance note:For novel designs, not recognised by the typical features of a known type of design, the stability requirements have to be consideredseparately and based on an evaluation of risks reflecting the unit's design, the intended operational aspects and the n-c-e---n-o-t-e---1.1.2 The standard has been written for general worldwide application. Governmental regulations mayinclude requirements in excess of the provisions by this standard depending on the size, type, location andintended service of the offshore unit or installation.1.2 ObjectivesThe objectives of this standard are to:— provide an internationally acceptable standard of safety by defining minimum requirements for stability,watertight integrity, freeboard and weathertight closing appliances— serve as a contractual reference document between suppliers and purchasers— serve as a guideline for designers, suppliers, purchasers and regulators— specify procedures and requirements for units or installations subject to DNV GL certification andclassification.2 Normative references2.1 General2.1.1 The standards given in [2.2] include provisions which, through reference in the text, constituteprovisions of this offshore standard. The latest issue of the references shall be used unless otherwiseagreed.2.1.2 Other recognised standards may be used provided it can be demonstrated that these meet or exceedthe requirements of the standards given in [2.2].2.1.3 Any deviations, exceptions and modifications to the design codes and standards shall be documentedand agreed between the contractor, purchaser and verifier, as applicable.Offshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 7Chapter 1 Section 1CHAPTER 1 INTRODUCTION
Chapter 1 Section 12.2 Reference documents2.2.1 Applicable DNV GL and DNV documents are given in Table 1.Table 1 DNV GL and DNV reference documentsReferenceTitleDNVGL-OS-B101Metallic materialsDNVGL-OS-C101Design of offshore steel structures, general - LRFD methodDNVGL-OS-C201Structural design of offshore units - WSD methodDNVGL-OS-D101Marine and machinery systems and equipmentDNV Rules for shipsDNV Rules for Classification of ShipsDNVGL-CG-0168Plan approval documentation types – definitionsDNV-RP-C205Environmental Conditions and Environmental LoadsDNV Classification Notes 20.1Stability Documentation for Approval2.2.2 Other reference documents are given in Table 2.Table 2 Normative referencesReferenceTitleICLL 1966International Convention on Load Lines, 1966, amended by Protocol 1988IMO MODU Code, 2009Code for the Construction and Equipment of Mobile Offshore Drilling Units, 20093 Informative references3.1 General3.1.1 Informative references are not considered mandatory in the application of this offshore standard,but may be applied or used for background information.3.1.2 Informative references are given in Table 3.Table 3 Informative referencesReferenceTitleISO 1751Shipbuilding and marine structures - Ships’ side scuttlesISO 3903Shipbuilding and marine structures - Ships’ ordinary rectangular windowsISO 1095Shipbuilding and marine structures - Toughened safety glass panes for side scuttlesISO 614Shipbuilding and marine structures - Toughened safety glass panes for rectangularwindows and side scuttles - Punch method of non-destructive testingSOLAS 1974The International Convention for the Safety of Life at Sea, 1974, as amended4 Definitions4.1 Verbal formsTable 4 DefinitionsTermDefinitionshallverbal form used to indicate requirements strictly to be followed in order to conform to the documentshouldverbal form used to indicate that among several possibilities one is recommended as particularly suitable, withoutmentioning or excluding others, or that a certain course of action is preferred but not necessarily requiredmayverbal form used to indicate a course of action permissible within the limits of the documentOffshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 8
Table 5 DefinitionsTermDefinitioncolumn stabilised unita unit with the main deck connected to the underwater hull or footings by columnsdamage penetration zone defined as 1.5 m from the outer skinThe damage penetration zone is limited to exposed portions only.damage waterlinethe final equilibrium waterline, including the wind heeling moment, after a damagedownfloodingany flooding of the interior of any part of the buoyant structure of a unit through openingswhich cannot be closed watertight or weathertight, as appropriate, in order to meet theintact or damage stability criteria, or which are required for operational reasons to be leftopendynamic anglethe angle of heel where the area requirement according to the stability requirements of Ch.2Sec.1 is achievedexposed portionsthose portions of the structure that are exposed to collision from other unitsGuidance note:For a column stabilised unit, the exposed portions are the portions of the columns, pontoons andbracings which are located outboard of a line drawn through the centres of the periphery columns,see Figure 1.Figure 1 Exposed portions of a column stabilised eld movethe transit voyage which can be completed within 12 hours (transit time) or within the limitsof favourable reliable weather forecasts, whichever is lessHowever, for certain operating areas and seasons, a field move may exceed 12 hours ifjustified by independent reliable evidence.Guidance note:Weather may be considered favourable up to Beaufort condition 6, i.e. average wind speed of --first interceptthe angle of heel where the righting moment curve intercepts the heeling moment curve forthe first timeThe first intercept is also known as the static angle of heel.floating offshoreinstallationa buoyant construction engaged in offshore operations including drilling, production,storage or support functions, and which is designed and built for installation at a particularoffshore locationfreeboardthe distance measured vertically downwards amidship from the upper edge of the deck lineto the upper edge in the related load linelightweightthe unvariable weight of the unit; i.e. the basis for calculating the loading conditionsAnchors and cables intended for mooring the unit at the field are to be excluded from thelightweight and included in the loading conditions as variable loads.Offshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 9Chapter 1 Section 14.2 Definitions
TermDefinitionmaximum allowablevertical centre of gravitythe maximum vertical centre of gravity (VCG) which complies with both intact and damagestability requirements at a given draught and service modeAll loading conditions are to have a VCG below the maximum allowable value for the givendraught and service mode. The free surface effect of each slack tank should be calculatedabout the axis at which the moment of inertia is the greatest.mobile offshore unita buoyant construction engaged in offshore operations including drilling, production,storage or support functions, not intended for service at one particular offshore site andwhich can be relocated without major dismantling or modificationoffshore installationa collective term to cover any construction, buoyant or non-buoyant, designed and built forinstallation at a particular offshore locationposition 1 and 2in accordance with Regulation 13 of the International Convention on Load Line 1966 (ILLC1966), adapted to mobile offshore unitssafe draughta draught which can be accepted under loading condition corresponding to damagedcondition with respect to strength, and the requirement for minimum airgap is fulfilledsecond interceptthe angle of heel where the righting moment curve intercepts the heeling moment curve forthe second timeself elevating unita unit with movable legs capable of raising its hull above the surface of the seaservice modes—operation condition, i.e. normal working condition—temporary conditions, i.e. transient conditions during change of draught to reachanother service mode or installation mode—survival condition, i.e. in case of severe storms—transit condition.ship shaped unita unit with a ship or barge type displacement hull of single or multiple hull constructionintended for operation in the floating conditionvariable loadthe load that varies with the operation of the unit such as deck cargo, fuel, lubricating oil,ballast water, fresh water, feedwater in tanks, consumable stores and crew and their effectswatertightcapable of preventing the passage of water through the structure under a head of water forwhich the surrounding structure is designedweathertightwater will not penetrate into the unit in any sea conditions4.3 Abbreviations and symbolsAbbreviations used are given in Table 6.Table 6 AbbreviationsAbbreviationFull textCGclass guidelineCIBSclassification information breakdown structureILLCInternational Convention on Load LinesIMOInternational Maritime OrganizationISOInternational Organisation for StandardisationLRFDload resistance factor designMODUmobile offshore drilling unitOSoffshore standardRPrecommended practiceVCGvertical centre of gravityWSDworking stress designOffshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 10Chapter 1 Section 1Table 5 Definitions (Continued)
5.1 General5.1.1 The documentation given in Table 7 is required to be produced to document aspects covered by thisstandard:Table 7 Documentation requirementsObjectDocumentation typeAdditional descriptionFor approval (AP) orFor information (FI)B010 – Lines plan or offset tablesB020 – External watertight integrityplan or freeboard planFISubject to approval for Column-stabilised andself-elevating units where beach lines accordingto Ch.2 Sec.2 [10.1] must be included.B030 – Internal watertight integrityplanFINot applicable for Ship-shaped units. See alsodefinition of B050 for more details.APB050 – Preliminary stability manualApplicable for Ship-shaped unitsAPB070 – Preliminary damage stabilitycalculationApplicable for Ship-shaped units. See alsodefinition of B050 for more details.APB040 – Stability analysisStabilityAP/FIB100 – Inclining test procedureAPB110 – Inclining test reportB120 – Final stability manualB130 – Final damage stabilitycalculationAPThe final stability manual may be included inthe operation manual.Applicable for Ship-shaped unitsB200 – Freeboard planAPAPAP5.1.2 For general requirements to documentation, see DNVGL-CG-0168 Sec.1.5.1.3 For a full definition of the documentation types, see DNVGL-CG-0168 Sec.2 and DNV ClassificationNote No. 20.1.5.1.4 For documentation requirements related to certification and classification, see Ch.3.Offshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 11Chapter 1 Section 15 Documentation
SECTION 1 STABILITY1 General1.1 Scope1.1.1 This section gives requirements related to the following design parameters of mobile offshore unitsand floating offshore installations:1) Buoyancy and floatability.2) Wind exposed portions.3) Draught range at various modes of service.4) Watertight and weathertight closing of external openings.5) Internal watertight integrity and watertight subdivision.6) Lightweight and loading conditions.1.1.2 The combination of the design parameters under [1.1.1] items 1 to 5 will determine the maximumallowable vertical centre of gravity (VCG) of the unit or installation at the applicable service draughts andmodes.1.1.3 The loading of the unit or installation at various service draughts and modes shall be within the limitsof maximum allowable VCG-curves.1.1.4 In order to determine VCG of the actual loading conditions, the lightweight and its centre of gravitymust be known. This shall be obtained by an inclining test carried out in accordance with [3].1.1.5 The requirements of this section are based on the IMO MODU Code, 2009.1.1.6 Deep draught floating installations (e.g. SPARs) are not directly covered by the IMO MODU Code.Criteria identical to those of a column stabilised unit or installations have been adopted.2 Determination of wind forces2.1 Heeling moment curves2.1.1 The curves of wind heeling moments shall be drawn for wind forces calculated by the following formula:2F 0.5 C s C h P V AF the wind force (Newton)Cs the shape coefficient depending on the shape of the structural member exposed to the wind (see Table2)Ch the height coefficient depending on the height above sea level of the structural member exposed towind (see Table 2)P the air mass density (1.222 kg/m3)V the wind velocity (metres per second)A the projected area of all exposed surfaces in either the upright or the heeled condition (square metres)(See MODU Code 3.2.3)2.1.2 Wind forces shall be considered from any direction relative to the unit and the value of the windvelocity shall be as follows:— in general a minimum wind velocity of 36 m/s (70 knots) for offshore service shall be used for normaloperating and transit conditions and a minimum wind velocity of 51.5 m/s (100 knots) shall be used forthe severe storm conditionsOffshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 12Chapter 2 Section 1CHAPTER 2 TECHNICAL PROVISIONS
(See MODU Code 3.2.4)2.1.3 In calculating the projected areas to the vertical plane, the area of surfaces exposed to wind due toheel or trim, such as under-deck surfaces, etc., shall be included using the appropriate shape factor. Opentruss work may be approximated by taking 30% of the projected block area of both the front and backsection, i.e. 60% of the projected area of one side.(See MODU Code 3.2.5)2.1.4 In calculating the wind heeling moments, the lever of the wind overturning force shall be takenvertically from the centre of pressure of all surfaces exposed to the wind to the centre of lateral resistanceof the underwater body of the unit. The unit is to be assumed floating free of mooring restraint.(See MODU Code 3.2.6)Interpretation:For units supported by dynamic positioning systems, the centre of the thruster force should be appliedas the centre of lateral resistance.In case the total maximum thruster force is less than the wind force, the total wind heeling momentmay be taken as a combination of wind moment and thruster moment. The lever of the wind forceshould in this case be taken to the centre of the lateral resistance of the hull. The lever of the maximumthruster force is taken vertically from centre of the thruster force to the centre of the lateral resistanceof the underwater end of –––Table 1 Values of the coefficient CsShapeCsSpherical0.4Cylindrical0.5Large flat surface (hull, deckhouse, smooth under-deck areas)Drilling derrick1.01.25Wires1.2Exposed beams and girders under deck1.3Small parts1.4Isolated shapes (crane, beam, etc.)1.5Clustered deckhouses or similar structures1.1Table 2 Values of the coefficient ChHeight above sea level (metres)ChHeight above sea level (metres)Ch0 – 15.31.00137.0 – 152.51.6015.3 – 30.51.10152.5 – 167.51.6330.5 – 46.01.20167.5 – 183.01.6746.0 – 61.01.30183.0 – 198.01.7061.0 – 76.01.37198.0 – 213.51.7276.0 – 91.51.43213.5 – 228.51.7591.5 – 106.51.48228.5 – 244.01.77106.5 – 122.01.52244.0 – 256.01.79122.0 – 137.01.56Above 2561.80Offshore standard, DNVGL-OS-C301 – Edition July 2015Stability and watertight integrityDNV GL ASPage 13Chapter 2 Section 1— where a unit is to be limited in operation to sheltered locations (protected inland waters such as lakes,bays, swamps, rivers, etc.) consideration shall be given to a reduced wind velocity of not less than 25.8m/s (50 knots) for normal operating conditions.
(See MODU Code 3.2.7)2.1.6 Wind heeling moments derived from wind tunnel tests on a representative model of the unit may beconsidered as alternatives to the methods given in [2.1.1].(See MODU Code 3.2.8)3 Determination of lightweight3.1 Inclining test3.1.1 An inclining test shall be required for the first unit of a design, when the unit is as near to completionas possible, to determine accurately the light ship data (weight and position of centre of gravity).(See MODU Code 3.1.1)Interpretation:For self-elevating units, lightweight Centre of Gravity should be specified for each relevant position ��end of –––3.1.2 For successive units which are identical by design, the light ship data of the first unit of the seriesmay be accepted in lieu of an inclining test, provided the difference in light ship displacement or position ofcentre of gravity due to weight changes for minor differences in machinery, outfitting or equipment,confirmed by the results of a deadweight
IMO MODU Code, 2009 Code for the Construction and Equipment of Mobile Offshore Drilling Units, 2009 Table 3 Informative references Reference Title ISO 1751 Shipbuilding and marine structures - Ships’ side scuttles ISO 3903 Shipbuilding and marine structures - Ships’ ordinary rectangular windows
Recommended practice, DNVGL-RP-C301 - Edition July 2015 Page 3 DNV GL AS CHANGES - CURRENT Changes - current General This document supersedes DNV-RP-C301, April 2012.
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Recommended practice, DNVGL-RP-G105 – Edition October 2015 Page 3 DNV GL AS CHANGES – CURRENT Changes – current General This document supersedes DNVGL-RP-0006, January 2014. Text affected by the main changes in this edition is highlighted in red colour. However, if the changes On 12 September 2013, DNV and GL merged to form DNV GL Group.File Size: 2MBPage Count: 77
