Section
4 Bottom Surveys – In dry dock and In-water – Hull and machinery requirements
4.1 General
4.2 Bottom Surveys in dry dock
4.2.1 Where a unit is in dry dock or on a slipway, it is to be placed on blocks
of sufficient height, and proper staging is to be erected as may be necessary, for
the examination of the shell, including bottom and bow plating, keel, sponsons and
appendages, stern, sternframe and rudder.
4.2.2 For self-elevating units, the leg footings and those parts of the leg and
hull that are normally under water are to be examined. The connections between leg
chords and the footings or mats are to be inspected and subjected to NDE.
4.2.3 For self-elevating units, at each Bottom Survey in dry-dock coinciding
with Special Survey, the Surveyor is to be satisfied with the internal condition of
the leg footings or mats. Leg connections to leg pads are to be non-destructively
tested. Non-destructive testing may be required of areas considered to be critical
or found to be suspect by the Surveyor. Non-metallic expansion pieces in the main
seawater cooling and circulating systems are to be examined both externally and
internally.
4.2.4 For column-stabilised units, external surfaces of the upper hull or
platform, footings, pontoons or lower hulls, underwater areas of columns, bracing
and their connections, sea chests, and propulsion units as applicable, are to be
selectively cleaned and examined to the satisfaction of the attending Surveyor.
Non-destructive testing may be required of areas considered to be critical or found
to be suspect by the Surveyor.
4.2.5 The shell plating is to be examined for excessive corrosion,
deterioration due to chafing or contact with the ground and for undue unfairness or
buckling. Special attention is to be given to the connections between the bilge
strakes and bilge keels.
4.2.6 The external cathodic protection system and coatings are to be
examined.
4.2.7 Visible parts of the rudder, rudder pintles, rudder stocks and couplings
and stern frame are to be examined. The pintles are to be examined either by removal
of the inspection plates, or if considered necessary by the Surveyor, the rudder is
to be lifted to enable examination. The clearances in the rudder bearings are to be
measured. The securing of rudder couplings and/or pintle fastenings is to be
confirmed. Where applicable, pressure testing of the rudder may be required if
deemed necessary by the Surveyor.
4.2.8 The sea chests, sea connections and overboard discharge valves and cocks
and their attachments to the hull are to be examined.
4.2.9 Visible parts of the propeller(s) and sternbushe(es), are to be examined.
The clearance in the sternbush and the efficiency of the oil gland, if fitted, are
to be ascertained and recorded. For controllable pitch propellers, the Surveyor is
to be satisfied with the fastenings and tightness of hub and blade sealing.
4.2.13 Where a unit has an *OIWS notation, at completion of each
dry-docking in order that the *OIWS notation can be maintained, the condition
of the high resistance paint is to be confirmed and, as applicable, satisfactory
access arrangements to take the sternbush clearance and rudder pintle/bearing
clearances are to be verified.
4.3 In-Water surveys
4.3.2 Special arrangements must be incorporated into the unit's design or
otherwise provided to allow adequate survey of thrusters, stern bearings, rudder
bearings, sea suctions and valves, etc., see
Pt 3, Ch 1, 2.1 General 2.1.3.
4.3.3 Special consideration shall be given to ascertaining rudder bearing
clearances and sternbush clearances, based on a review of the operating history,
onboard testing and stern bearing oil analysis. These considerations are to be
included in the proposals, see
Pt 1, Ch 3, 4.3 In-Water surveys 4.3.5.
4.3.4 The In-Water Survey is to provide the information normally obtained from
the Bottom Survey in dry-dock, so far as practicable. For oil-lubricated sternbush
arrangements the clearance in the sternbush is not required to be ascertained
subject to the Surveyor confirming satisfactory operating history and condition data
records (lubricating oil analysis, bearing temperature, lubricating oil consumption)
and verifying satisfactory operation of the screwshaft.
4.3.5 When there is no access, special consideration shall be given to ascertaining rudder
bearing clearances and sternbush clearances of water-lubricated bearings based on a
review of the operating history, on board testing and stern bearing condition data.
These considerations are to be included in the proposals for In-Water Surveys which
are to be submitted in advance of the survey being required, so that satisfactory
arrangements can be agreed with LR.
4.3.6 Proposals for In-Water Surveys are to be submitted in advance of the
survey being required so that satisfactory arrangements can be agreed with LR.
4.3.7 A planned procedure for the routine inspection of the underwater areas
is to be agreed between the Owners and LR. A procedure document is to be placed on
board the unit and made available to the Surveyor. Where survey experience indicates
that modifications are required to the inspection procedures, the procedure document
is to be modified to the satisfaction of LR.
4.3.8 The In-Water Survey is to be carried out at an agreed geographical
location, with the Surveyor to LR satisfied that the unit at a suitable draught and
the conditions satisfactory for diver or ROV inspection. The In-Water visibility is
to be good and the hull below the waterline is to be clean. The Surveyor is to be
satisfied that the method of pictorial presentation is satisfactory. There is to be
good two-way communication between the Surveyor and the diver/ROV operator. The
Surveyor is to be satisfied with the methods of orientation of the divers on the
plating, which should make use where necessary of permanent markings on the plating
at selected points. The Survey is to be witnessed by the Surveyor. This requires the
Surveyor to be on board while the Survey is carried out, to the extent necessary to
control the process. The Surveyor may extend the scope of Survey if deemed
necessary.
4.3.9 Prior to commencing the In-Water Survey, the equipment and procedures for both
observing and reporting the survey are to be agreed between the Owners, the Surveyor
and the diving firm.
4.3.10 In general, the In-Water Survey is to be carried out using LR approved
diving company with suitably qualified divers. Alternatively, the In-Water Survey
may be carried out using a LR approved ROV operator, subject to agreement with the
attending LR Surveyor.
4.3.11 The efficient condition of the cathodic protection system and the high
resistance paint is to be confirmed at each In-Water Survey to the satisfaction of
the Surveyors, in order that the OIWS notation can be maintained.
4.3.12 If the In-Water Survey reveals damage or deterioration that requires
early attention, the Surveyor may require that the unit be dry-docked, in order that
a more detailed survey can be undertaken and the necessary work carried out.
4.3.13 Diver/ROV-assisted surveys are not acceptable for the periodic survey
inspections of primary bracing members, or intersections of bracings with columns or
pontoons, or column to pontoon intersections on column-stabilised units, except in
exceptional circumstances when specially agreed with the Classification Committee
and the procedures have been approved, see alsoPt 3, Ch 1, 2.2 Construction booklet 2.2.3.
4.3.14 Turret and bearings below water level, underwater parts of mooring towers
and/or articulated towers (where applicable), chain stoppers, chain cables and
mooring lines/chains are to be examined as far as practicable during In-Water
Surveys. On tension-leg units, tethers and their upper and lower connections are to
be examined.
|