Section 6 Special Survey – Thickness measurement requirements for steel ships
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Naval Ships, January 2023 - Volume 1 Ship Structures - Part 1 Regulations - Chapter 3 Periodical Survey Regulations - Section 6 Special Survey – Thickness measurement requirements for steel ships

Section 6 Special Survey – Thickness measurement requirements for steel ships

Parent topic: Chapter 3 Periodical Survey Regulations

6.1 General

6.1.1 Thickness measurement requirements for steel ships are stated in Tables Table 3.6.1 Thickness measurement of steel ships and Table 3.6.2 Thickness measurement - Additional requirements in way of structure identified with substantial corrosion. See also Vol 1, Pt 1, Ch 3, 1.8 Thickness measurement at surveys.

6.1.2 Thickness measurements may be carried out in association with the fifth Annual Survey.

6.1.3 In areas where substantial corrosion, as defined in Vol 1, Pt 1, Ch 3, 1.5 Definitions, has been noted, then additional measurements are to be carried out, as applicable, in accordance with Table 3.6.2 Thickness measurement - Additional requirements in way of structure identified with substantial corrosion to determine the full extent of the corrosion pattern.

6.1.4 Where substantial corrosion is identified and not rectified, this will be subject to re-examination and gauging as necessary at Annual and Intermediate Surveys.

6.1.5 At each Special Survey, thickness measurements are to be taken in way of critical areas, as considered necessary by the Surveyor. Critical areas are to include locations throughout the ship that show substantial corrosion and/or are considered prone to rapid wastage.

6.1.6 The Surveyor may extend the scope of thickness measurement if deemed necessary.

Table 3.6.1 Thickness measurement of steel ships

Special Survey I
(Ship 6 years old) 		Special Survey II
(Ship 12 years old) 		Special Survey III
(Ship 18 years old) 		Special Survey IV and subsequent
(Ship 24 years old and over)
       

(1) Bottom and lower parts of chain locker.

(2) Critical and Suspect areas, as required by the Surveyor and may include areas where the coatings are found to be other than in GOOD condition.

(1) Wind and water strakes in way of 0,5L amidships.

(2) Bottom and lower parts of chain locker.

(3) Critical and Suspect areas, as required by the Surveyor and may include areas where the coatings are found to be other than in GOOD condition.

(1) Weatherdeck plating under wood deck planking or sheathing

(2) Shell plating in way of the waterline throughout the length of the ship.

(3)Two complete transverse sections of deck and shell plating within 0,5L amidships, one of which should be in way of a machinery space

(4) Bottom and lower parts of chain locker.

(5) Critical and Suspect areas, as required by the Surveyor and may include areas where the coatings are found to be other than in GOOD condition.

(1) All weatherdeck plating outside deck-houses or superstructures and including plating under wood deck planking or sheathing.

(2) Shell plating in way of, and below, the waterline throughout the length of the ship.

(3) Two complete transverse sections of deck and shell plating within 0,5L amidships, one of which should be in way of a machinery space.

(4) Bottom and lower parts of chain locker.

(5) Critical and Suspect areas, as required by the Surveyor and to include as applicable:

(a) Areas where the coatings are found to be other than in GOOD condition.

(b) Bottom shell in way of any cement, asphalt, ballast or other composition.

(c) Deck plating and side shell plating in way of galleys, washrooms and refrigerated store spaces and any other wet spaces.

(d) Structure in way of integral sanitary tanks.

Note See Vol 1, Pt 1, Ch 3, 1.5 Definitions 1.5.9 for the definition of GOOD condition.

Table 3.6.2 Thickness measurement - Additional requirements in way of structure identified with substantial corrosion

Structural member Extent of measurement Pattern of measurement
Plating Suspect areas and adjacent plates 5 point pattern over 1 m2
Stiffeners Suspect areas 3 measurements each in line across web and flange

6.2 Thickness measurement reporting

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

6.2.2 The thickness measurement report is to be verified and signed by the Surveyor, and included with the Surveyor’s report.

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