Section 5 Special Survey – Hull requirements

5.1.1 The survey is to be of sufficient extent to ensure that the hull/structure and related piping is in satisfactory condition and is fit for its intended purpose, subject to proper maintenance and operation and to periodical surveys being carried out as required by the Regulations.

5.1.2 The examination is to be sufficient to ascertain substantial corrosion, significant deformation, fractures, damages or other structural deterioration and, if deemed necessary by the Surveyor, suitable non-destructive examination may be required.

5.1.3 The requirements of Pt 1, Ch 3, 1.6 Planned survey programme are to be complied with as applicable for all units.

5.1.4 The requirements of Pt 1, Ch 3, 2 Annual Surveys – Hull and machinery requirements are to be complied with, as applicable, for all units.

5.1.5 A Docking Survey, or an In-water Survey in lieu of a Docking Survey, in accordance with the requirements of Pt 1, Ch 3, 4 Docking Surveys and In-water Surveys – Hull and machinery requirements is to be carried out as part of the Special Survey.

5.1.6  Ship units and other surface type units. For units with crude oil bulk storage tanks, the requirements of Pt 1, Ch 3, 7 Special Survey - Oil tankers (including ore/oil ships and ore/bulk/oil ships) - Hull requirements of the Rules for Ships are to be complied with as applicable. For units with liquefied gas cargo containment systems, the additional requirements of Pt 1, Ch 3, 9 Ships for liquefied gases of the Rules for Ships are to be complied with as applicable.

5.2.1 The unit is to be prepared as necessary for the Surveyors to gain proper access for the careful inspection and examination of all items listed in this Section. Voids and closed spaces are to be thoroughly ventilated to ensure adequate levels of oxygen in the air, fuel tanks, oil storage tanks and other similar spaces are to be gas freed and cleaned as necessary and paint lining, insulation and other coatings and coverings are to be removed locally if required by the Surveyors.

5.2.2 In cases where the inner surface of the bottom plating is covered with cement, asphalt, or other composition, the removal of this covering may be dispensed with, provided that it is inspected, tested by beating and chipping and found sound and adhering satisfactorily to the steel.

5.2.3  Ship units and other surface type units. The requirements of Pt 1, Ch 3, 5.2 Preparationof the Rules for Ships are to be complied with, as applicable.

5.3.1 All spaces within the hull/structure and superstructure are to be subject to an overall survey and examination.

5.3.2 Watertight integrity of tanks, bulkheads, hull, decks and other compartments is to be verified by visual inspection.

5.3.3  Ship units and other surface type units. The requirements of Pt 1, Ch 3, 5.3 Examination and testing of the Rules for Ships are to be complied with, as applicable. Testing of crude oil storage tanks is to be carried out as deemed necessary by the attending Surveyor. For units assigned an ESP notation, the requirements of Pt 1, Ch 3, 7.5 Testing of the Rules for Ships are to be complied with as applicable, see also 5.3.15.

5.3.4 For tank internal examinations, the requirements of Pt 1, Ch 3, 5.3 Examination and testing 5.3.2of the Rules for Ships are to be complied with as applicable.

5.3.5 In spaces used for salt-water ballast, excluding double bottom tanks, where a protective coating is found in POOR condition, as defined in Pt 1, Ch 3, 1.5 Definitions, and it has not been repaired, where a soft or semi-hard coating has been applied or where a protective coating was not applied from the time of construction, maintenance of class will be subject to the space in question being internally examined and gauged as necessary at Annual Surveys.

5.3.6 For independent salt-water double bottom tanks where a protective coating is found to be in POOR condition, as defined in Pt 1, Ch 3, 1.5 Definitions, and it has not been repaired, where a soft or semi-hard coating has been applied or where a protective coating was not applied from the time of construction, maintenance of class may, at the discretion of the Classification Committee, be subject to the spaces in question being examined and gauged as necessary at Annual Surveys.

5.3.7 Double bottom, deep, ballast, peak and other tanks, including cargo holds assigned also for the carriage of salt-water ballast, are to be tested with a head of liquid to the top of air pipes or to the top of hatches for ballast/cargo holds. Boundaries of oil fuel, lubricating oil and fresh water tanks are to be tested with a head of liquid to the maximum filling level of the tank. Tank testing of oil fuel, lubricating oil and fresh water tanks may be specially considered, based upon a satisfactory external examination of the tank boundaries, and a confirmation from the Master stating that the pressure testing has been carried out according to the requirements with satisfactory results.

5.3.8 Where repairs are effected to the shell plating or bulkheads, any tanks in way are to be tested to the Surveyor's satisfaction on completion of these repairs.

5.3.9 In units with crude oil storage tanks, all piping systems on deck and within the storage tanks and adjacent spaces are to be examined to ensure that tightness and condition remain satisfactory. Special attention is to be given to ballast piping in storage tanks and crude oil storage piping in ballast tanks, pump-rooms, pipe tunnels and void spaces.

5.3.10 Where substantial corrosion, as defined in Pt 1, Ch 3, 1.5 Definitions, is identified in crude oil storage tanks and is not rectified, this will be subject to re-examination at Annual and Intermediate Surveys and is to be gauged as necessary.

5.3.11 At the first Special Survey and at subsequent Special Surveys, representative tanks are to be examined by a Close-up Survey. The extent of the survey is to be agreed with LR in advance of the survey. For all units over 10 years of age, all salt-water ballast tanks and free-flooding areas where accessible are to be examined.

5.3.12 The attachment to the structure and condition of anodes in all tanks is to be examined.

5.3.13 In addition to the requirements of 5.3.1, columnstabilised units and tension-leg units are to have a complete bracing Close-up Survey consisting of a detailed dry examination of all bracings and their structural connections to columns and decks. The connections of columns to lower hulls, pontoons and upper hulls are to be examined. All critical regions defined in 2.2.3 are to be examined by approved methods of NDE, see also Pt 1, Ch 2, 3.5 Existing installations – Periodical Surveys. Primary structure of the upper hull or platform which form 'Box' or 'I' type supporting structure and their end connections are to be examined. All free-flooding areas and sponsons are to be examined.

5.3.14 In addition to the requirements of 5.3.1, self-elevating units are to have a complete survey of all legs, footings and mats. Particular attention is to be given to the leg structure in way of the waterline. Tubular or similar type legs are to be examined externally and internally, including stiffeners and pin holes. All critical regions defined inPt 1, Ch 3, 2.2 Structure and equipment are to be examined by approved methods of NDE, including the leg connections to footings or mats, see also Pt 1, Ch 2, 3.5 Existing installations – Periodical Surveys. Jetting piping systems or other external piping, particularly where penetrating footings or mats, are to be examined. Where the spud cans or mat are partly or entirely obscured below the mud line where the Special Survey is otherwise being completed, consideration may be given to postponement of the examinations until the next Rig move.

5.3.15 In addition to the requirements of 5.3.1, surface type units are to have a Close-up Survey carried out in accordance with an agreed programme, see also Pt 1, Ch 3, 1.6 Planned survey programme. The programme should identify all critical areas of primary structure components and connections within compartments to be surveyed. Special attention is to be given to underdeck structure supporting topside equipment, flare stack and cranes, etc. The Surveyor may extend the Close-up Survey if deemed necessary, taking into account the maintenance of the tanks under survey and the condition of the corrosion prevention system. For areas in tanks where coatings are found to be in GOOD condition, as defined inPt 1, Ch 3, 1.5 Definitions , the extent of Close-up Survey may be specially considered.

5.3.16 In addition to the requirements of 5.3.1, structural appendages and ducts for positioning units, sponsons and positioning spuds on surface type units are to be examined.

5.3.17 On all units, careful examination is to be made of those parts of the structure particularly liable to excessive corrosion, or to deterioration or damage from causes such as chafing, lying on the sea bed or handling of drilling equipment, stores, etc., and due to water collection in corners of bulkheads and on weather decks, and in other exposed areas.

5.3.18 All decks including helidecks and their supporting structure, deck-houses, casings and superstructures are to be examined. Where aluminium alloy is used in the structure, bimetallic joints are to be examined as far as practicable. Lifeboat and winch platforms and their supporting structures are to be examined.

5.3.19 Wood decks and sheathing are to be examined. If decay or rot is found or the wood is excessively worn, the wood is to be renewed. Attention is to be given to the condition of the plating under wood decks, sheathing or other deck covering. If it is found that such coverings are broken, or are not adhering closely to the plating, sections are to be removed as necessary to ascertain the condition of the plating, see also Pt 1, Ch 3, 1.2 Surveys for damage or alterations.

5.3.20 Primary bulkheads in the upper hull of columnstabilised units and in the hull of self-elevating units are to be examined. Particular attention is to be given to the structure below and derrick sub-structures and supports under process plant, drilling derricks and other heavy equipment. Bulkheads adjacent to leg wells, turrets and moonpools are to be examined. Bulkhead penetrations in way of doors and other openings are to be examined.

5.3.21 A Close-up Survey of structure around external and internal turrets is to be held as per an agreed planned survey programme. Thickness measurements are to be made as per the agreed planned survey programme, seePt 1, Ch 2, 3.5 Existing installations – Periodical Surveys . Turret bearings are to be examined in accordance with the manufacturers’ recommendations and agreed survey programme. Records of analyses of turret and swivel bearing seals and lubricants are to be examined by the Surveyors for compliance to manufacturers’ standards and/or recommendations.

5.3.22 Mooring buoys, mooring arms and yokes, mooring towers, and other similar special features of the installation are to be specially examined in accordance with an agreed planned survey programme.

5.3.23 For deep draught caisson units having combined oil/ballast tanks which for operational requirements are always full, the periodic survey programme is to be agreed to at the design stage. Owners may consider installing suitable steel coupon plates in these tanks, where practicable, to monitor corrosion. Where coupon plates are fitted, their position will be specially considered and they are to be electrically insulated from the unit. Weight and thickness of the coupon plates are to be recorded and reported at each special survey.

5.3.24 For tension-leg units, a Close-up Survey of the structure in way of tethers is to be carried out.

5.3.25 For units having a DRILL notation, the drilling derrick, including bolting arrangements is to be examined. Other structural components and supports forming part of the drilling plant are to be examined and tested as necessary, see also Pt 1, Ch 3, 2.7 Drilling units.

5.3.26 For production units with a process plant facility having a PPF notation, all plant supporting structure, including bracing trusses and skids, is to be examined, see also Pt 1, Ch 3, 2.5 Production and oil storage units.

5.3.27 The requirements for thickness determination of the structure of all unit types are to be in accordance with Pt 1, Ch 3, 5.4 Thickness measurement.

5.3.28 Crane pedestals and similar supporting structures to access gangways and flare booms, masts and standing rigging are to be examined.

5.3.29 At the second Special Survey and subsequent Special Surveys, chain lockers are to be cleaned and examined internally.

5.3.30 For disconnectable units and mobile offshore units assigned the character figure (1), anchors are to be examined. Anchors are to be partially lowered and raised by the windlass or winch as applicable. The chain cables and wire rope cables are to be examined as far as practicable. If any length of chain cable is found to be reduced in mean diameter at its most worn part by 12 per cent or more from its nominal diameter, it is to be renewed. The anchor windlass or winch is to be examined. For equipment forming part of a positional mooring system, seePt 1, Ch 3, 5.5 Positional mooring systems.

5.3.31 The hand pumps, suctions, watertight doors, air and sounding pipes are to be examined. In addition, the Surveyor is to examine internally air pipe heads in accordance with the requirements of Table 3.1.

5.3.32 The Surveyor is to be satisfied as to the efficient condition of the helm indicator, protection of aft steering wheel and gear on self-propelled units.

5.3.33 Foundations and supporting headers, brackets and stiffeners for drilling-related apparatus, where attached to hull, deck, substructure or deck-house, are to be examined.

5.3.34 Foundations of machinery are to be examined.

5.4.1 The requirements for thickness measurements given in Pt 1, Ch 3, 1.8 Thickness measurement at survey are to be complied with.

5.4.2 In addition to the thickness measurements required by 5.4.1 to ascertain local wastage, thickness measurement is to be carried out on units with crude oil bulk storage tanks at the first Special Survey and at subsequent Special Surveys, in accordance with the requirements of Pt 1, Ch 3, 5.6 Thickness measurement and Pt 1, Ch 3, 7.7 Thickness measurement of the Rules for Ships, as applicable.

5.4.3 On all other unit types, thickness measurement is required at the second Special Survey and at subsequent Special Surveys. Thickness measurement of the primary hull structure is to include the shell plating of hulls, pontoons, columns, bracings, main strength decks, bulkheads, legs, footings, mats and the structure of representative salt-water ballast and pre-load tanks and other tanks and critical areas as required by the Surveyor, to determine the amount of any general diminution in thickness. The extent and location of such measurements are to be agreed by LR prior to each survey, see also Pt 1, Ch 3, 1.6 Planned survey programme.

5.4.4 A report is to be prepared by the qualified firm carrying out the thickness measurements. The report is to give the location of measurement and the thickness measured as well as the corresponding original thickness. The report is to give the date when measurement was carried out, the type of measuring equipment, names of personnel and their qualifications and is to be signed by the Operator.

5.4.5 The thickness measurement report is to be verified and signed by the Surveyor and countersigned by an Authorising Surveyor.

5.5.1 On units fitted with positional mooring equipment which have been assigned a special features notation in accordance with Pt 3, Ch 10 Positional Mooring Systems, the requirements for annual surveys in Pt 1, Ch 3, 2.2 Structure and equipment are to be complied with.

5.5.2 Where practicable, mooring cables, chains and anchors are to be lifted to the surface for detailed inspection in accordance with 5.5.3 and 5.5.4 at each Special Survey. Alternatively, in situ inspection, using acceptable techniques, will be considered by LR when requested. See also Pt 3, Ch 17 Appendix B Guidelines on the Inspection of Positional Mooring Systems for guidance notes on the inspection of positional mooring systems.

5.5.4 Anchors of mobile offshore units are to be cleaned and examined. Wire rope anchor cables are to be examined. If cables are found to contain broken, badly corroded or bird caging wires, they are to be renewed. Chain cables are to be ranged and examined. Maximum acceptable diminution of anchor chain in service will normally be limited to a two per cent reduction from basic chain diameter (basic chain diameter can be taken as the diameter, excluding any design corrosion allowance, which satisfies the Rule requirement for minimum factors of safety).

5.5.5 The windlasses or winches are to be examined.

5.5.6 Structure in way of anchor racks and anchor cable fairleads is to be examined.