Class surveys periodicity and scope

IMO, Uncategorized

Class renewal survey / special survey

Class renewal surveys/special surveys are carried out at five-year intervals. However, consideration may be given by the Society, in exceptional circumstances, to granting an extension for a maximum period of three months after the due date. In such cases the next period of class will start from the due date for the previous class renewal survey before the extension was granted. The special survey may be commenced at the 4th annual survey and be progressed with a view to completion by the 5th anniversary date. The class renewal surveys/special surveys include extensive examinations to verify that the structure, main and essential auxiliary machinery, systems and equipment of the ship are in a condition which satisfies the relevant Rules. The examinations of the hull are generally supplemented by thickness measurements and witnessing of tests as specified in the Rules, and as deemed necessary by the attending surveyor, to assess that the structural condition remains effective and to help identify substantial corrosion, significant deformation, fractures, damages or other structural deterioration.

Annual survey

Annual surveys are to be carried out within a window from three months before to three months after each anniversary date. At the time of annual surveys, the ship is generally examined. The survey includes an inspection of the hull, equipment and machinery of the ship and some witnessing of tests, so far as is necessary and practical in order to verify that, in the opinion of the attending surveyor(s) the ship is in a general condition which satisfies the Rule requirements.

Intermediate survey

An intermediate survey is to be carried out within the window from three months before the second to three months after the third anniversary date. The intermediate survey includes examinations and checks on the structure as specified in the Rules to verify that the vessel is in compliance with the applicable Rule requirements. The Rule criteria become more stringent with age. According to the type and age of the ship the examinations of the hull may be supplemented by thickness measurements as specified in the Rules and where deemed necessary by the attending surveyor.

Bottom / Docking survey

A bottom/docking survey is the examination of the outside of the ship’s hull and related items. This examination may be carried out with the ship either in dry dock (or on a slipway) or afloat: in the former case the survey will be referred to as dry-docking survey, while in the latter case as in-water survey. The conditions for acceptance of an in-water survey in lieu of a drydocking survey will depend on the type and age of the ship and the previous history. The outside of the ship’s hull and related items are to be examined on two occasions in the five-year period of the certificate of class with a maximum of 36 months between surveys. One of the two bottom/docking surveys to be performed in the five-year period is to be concurrent with the class renewal/special survey. For ships subject to the Enhanced Survey Programme (ESP) and 15 years of age and above, the intermediate bottom/docking survey is to be carried out in a dry-dock.

Tailshaft survey

A tailshaft survey is the survey of screwshafts and tube shafts (hereafter referred to as tailshafts) and the stern bearing. The different types of surveys to which tailshafts may be subjected and the intervals are:

  • complete survey
  • modified survey
  • partial survey.

Tailshaft complete survey

Tailshafts are to be submitted to complete examination at a periodicity based on the type of shaft and its design. “Complete” means that the shaft is drawn up for examination or that other equivalent means of examination are provided.

Tailshaft modified survey

A modified survey of the tailshaft is an examination which may be accepted at alternate five-yearly surveys for tailshafts provided that the shaft arrangement is in accordance with specific requirements.

Tailshaft partial survey

A partial survey allows a postponement of the complete survey, having a periodicity of 5 years, for 2.5 years.

Boiler surveys

Boilers and thermal oil heaters are to be surveyed twice in every five-year period. The periodicity of the boiler survey is normally 2.5 years. Steam boilers, superheaters and economisers are examined internally and externally. To this end, boilers are to be drained and suitably prepared for the examination of the water-steam side and the fire side. Where necessary, the external surfaces are to be made accessible for inspection by removal of insulation and lining.

Non-periodical surveys

Such surveys are carried out for example:

  • to update classification documents (e.g. change of owner, name of the ship, change of flag);

.• to deal with damage or suspected damage, repair or renewal work, alterations or conversion, postponement of surveys or outstanding recommendations/conditions of class;

  • At the time of port State control inspections.

In the event of damage which affects or may affect the class of the ship, the owner is to advise the Society without delay. Arrangements are then made at the earliest opportunity for a surveyor to attend and ascertain the extent of the damage and determine if it is such that the vessel no longer complies with the applicable Rule requirements. Following repair, the surveyor will again assess the status of the vessel to determine if it has been returned to a condition that is in compliance with the applicable Rule requirements. Any damage in association with wastage over the allowable limits (including buckling, grooving, detachment or fracture), or extensive areas of wastage over the allowable limits, which affects or, in the opinion of the surveyor, will affect the vessel’s structural, watertight or weathertight integrity, is to be promptly and thoroughly repaired thereby removing the need for the imposition of any associated condition of classification. Otherwise, damages and partial or temporary repairs considered acceptable by the surveyor for a limited period of time are covered by the issuance of an appropriate recommendation/condition of class. Damages or repairs required by the surveyor to be reexamined after a certain period of time are also covered by an appropriate recommendation/condition of class.


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