Section 5 Special Survey - Thickness measurement requirements for steel yachts
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Special Service Craft, July 2022 - Part 1 Regulations - Chapter 4 Periodical Survey Regulations for Yachts - Section 5 Special Survey - Thickness measurement requirements for steel yachts

Section 5 Special Survey - Thickness measurement requirements for steel yachts

Parent topic: Chapter 4 Periodical Survey Regulations for Yachts

5.1 General

5.1.1 Thickness measurements, as required by Pt 1, Ch 4, 4 Special Survey - General - Hull requirements are to be carried out in accordance with the following requirements.

5.1.2 Thickness measurements are to be taken at the forward and aft areas of all plates. In all cases the measurements are to represent the average of the multiple measurements taken on each plate. The extent of local substantial corrosion of plates is to be established by intensive measurement in the affected areas. Where measured plates are renewed, the thicknesses of adjacent plates in the same strake are to be reported.

5.1.3 Thickness measurements are normally to be by means of ultrasonic test equipment. For vessels less than 500 gross tons a suitably qualified exclusive Surveyor (where available) may carry out thickness measurements. On all other occasions, thickness measurements are to be carried out by a firm approved in accordance with LR’s Approval for Thickness Measurement of Hull Structures.

5.1.4 Thickness measurements may be carried out in association with the fourth Annual Survey.

5.1.5 The minimum requirements for thickness measurement are indicated in Table 4.5.1 Thickness measurement of steel yachts.

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

5.1.7 The acceptance criteria for thickness measurements are according to the LR document Thickness Measurement and Close-Up Survey Guidance.

5.2 Thickness measurement reporting

5.2.1 A report is to be prepared by the approved firm 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 and supervisor.

5.2.2 The thickness measurement report is to be verified and signed by the Surveyor.

Table 4.5.1 Thickness measurement of steel yachts

Special Survey I
(Yachts 5 years old) 		Special Survey II
(Yachts 10 years old) 		Special Survey III
(Yachts 15 years old) 		Special Survey IV and subsequent
(Yachts 20 years old and over)
Suspect areas, as required by the Surveyor and may include areas where the coatings are found to be other than in GOOD condition, see Note 1. Suspect areas, as required by the Surveyor and may include areas where the coatings are found to be other than in GOOD condition, see Note 1. (1) Any exposed plating throughout the Main Deck. (1) All Main Deck plating outside deckhouses or superstructures and including plating in way of wood deck planking or sheathing.

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

(2) Shell plating in way of the waterline throughout the length of the craft.
(3) Suspect areas, as required by the Surveyor may include areas where the coatings are found to be other than in GOOD condition, see Note 1. (3) 2 transverse sections of deck and shell plating within 0.5L amidships.
(4) 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) Shell and tanktop plating immediately adjacent to tank top margins.
(c) Bottom shell in way of any cement, asphalt or other composition.
(d) Shell plating below portlights and windows.
(e) Tanktop plating below ceiling or cabin soles.
(f) Deck plating and side shell plating in way of galleys, washrooms and refrigerated store spaces.
(g) Structure in way of integral sanitary tanks.

Note 1. Suspect areas are locations within the hull structure vulnerable to increased likelihood of structural deterioration and may include, for steel hulls, areas of substantial corrosion and/or fatigue cracking, see also Pt 1, Ch 4, 1.5 Definitions 1.5.3 and Pt 1, Ch 4, 4.4 Examination and testing - Additional items for steel yachts 4.4.6.

Note 2. Coating condition for steel craft is defined in Pt 1, Ch 4, 1.5 Definitions 1.5.6.

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