Maintaining cargo ships seaworthyness - Periodic surveys by Classification Societies
Requirement of Periodic surveys
To maintain the assigned class all steel ships are required to be surveyed and examined by the Society’s surveyors at regular periods. The major hull items to be examined at these surveys only are discussed here.
Annual surveys are applicable for all steel ships. These annual surveys are where practicable held concurrently with statutory annual or other load line surveys.
At the survey the surveyor is to examine the condition of all closing appliances covered by the conditions of assignment of minimum freeboard, the freeboard marks, and auxiliary steering gear particularly rod and chain gear. Watertight doors and other penetrations of watertight bulkheads are also examined and the structural fire protection verified. The general condition of the vessel is assessed, and anchors and cables are inspected where possible at these annual surveys. Dry bulk cargo ships are subject to an inspection of a forward and after cargo hold.
Instead of the second or third annual survey after building or special survey an intermediate survey is undertaken. In addition to the requirements for annual survey particular attention is paid to cargo holds in vessels over 15 years of age and the operating systems of tankers, chemical carriers and liquefied gas carriers.
Ships are to be examined in dry dock at intervals not exceeding 2½ years. At the drydocking survey particular attention is paid to the shell plating, stern frame and rudder, external and through hull fittings, and all parts of the hull particularly liable to corrosion and chafing, and any unfairness of bottom.
The Society may accept in-water surveys in lieu of any one of the two dockings required in a five-year period. The in-water survey is to provide the information normally obtained for the docking survey. Generally consideration is only given to an in-water survey where a suitable high resistance paint has been applied to the underwater hull.
Steel ships may be subject to special surveys as required by various classification society rules. These surveys become due at five yearly intervals, the first five years from the date of build or date of special survey for classification and thereafter five years from the date of the previous special survey. Special surveys may be carried out over an extended period commencing not before the fourth anniversary after building or previous special survey, but must be completed by the fifth anniversary.
The hull requirements at a special survey, the details of the compartments to be opened up, and the material to be inspected at any special survey are listed in detail in the Rules and Regulations . Special survey hull requirements are divided into four ship age groups as follows:
1. Special survey of ships—five years old
2. Special survey of ships—ten years old
3. Special survey of ships—fifteen years old
4. Special survey of ships—twenty years old and at every special survey thereafter.
In each case the amount of inspection required increases and more material is removed so that the condition of the bare steel may be assessed. It should be noted that where the surveyor is allowed to ascertain by drilling or other approved means the thickness of material, non-destructive methods such as ultrasonics are available in contemporary practice for this purpose. Additional special survey requirements are prescribed for oil tankers, dry bulk carriers, chemical carriers and liquefied gas carriers.
When classification is required for a ship not built under the supervision of the Society’s surveyors, plans showing the main scantlings and arrangements of the actual ship are submitted to the Society for approval. Also supplied are particulars of the manufacture and testing of the materials of construction, together with full details of the equipment. Where plans, etc., are not available, the Society’s surveyors are to be allowed to lift the relevant information from the ship. At the special survey for classification all the hull requirements for special surveys (1), (2), and (3) are to be carried out.
Ships over twenty years old are also to comply with the hull requirements of special survey (4), and oil tankers must comply with the additional requirements stipulated in the Rules and Regulations. During this survey the surveyor assesses the standard of the workmanship, and verifies the scantlings and arrangements submitted for approval. It should be noted that the special survey for classification will receive special consideration from Lloyd’s Register in the case of a vessel transferred from another recognized Classification Society. Periodical surveys where the vessel is classed are subsequently held as in the case of ships built under survey, being dated from the date of special survey for classification.
When a vessel requires repairs to damaged equipment or to the hull it is necessary for the work to be carried out to the satisfaction of Lloyd’s Register surveyors. In order that the ship maintains its class, approval of the repairs undertaken must be obtained from the surveyors either at the time of the repair or at the earliest opportunity.
Related information :
Basic Design of the Cargo Ship - Economic factors designing a new ship
Role of Classification Societies in maintaining cargo ships standard
Protecting ships hull against corrosion - Recommended paint methods as ruled by class surveyors
Ropes and hawsers used on board a general cargo vessel
Cargo ships various lifting gears - Advantages
Operation of deck cranes
Characteristics of marine paints
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