27. (1) Where the interval between periodical inspections of a ship is four years, it shall be inspected

• (a) in accordance with the requirements of sections 24, 25 and 26, at each quadrennial inspection; and

• (b) in accordance with the requirements of subsection (3),

  • (i) at the first quadrennial inspection after the ship is 24 years old, and

  • (ii) every 12 years after the inspection referred to in subparagraph (i).

(2) Where the interval between periodical inspections of a ship referred to in subsection 18(2) is five years,

• (a) it shall be inspected

  • (i) in accordance with the requirements of sections 24, 25 and 26 at each quinquennial inspection until the ship is 40 years old, and at every quadrennial inspection thereafter, and

  • (ii) in accordance with the requirements of subsection (3),

    • (A) at the first quinquennial inspection after the ship is 24 years old,

    • (B) at the first quadrennial or quinquennial inspection 15 years after the inspection referred to in clause (A), and

    • (C) every 12 years after the inspection referred to in clause (B); and

• (b) the oil fuel bunkers shall be gas-freed, thoroughly cleaned and examined internally at the first quinquennial inspection after the ship is 24 years old, after the next 10 years, after the next nine years, and every eight years thereafter, except that where, upon external examination, the inspector finds the condition of the bunkers to be satisfactory, the gas-freeing, cleaning and internal examination is not necessary.

(3) At the inspection referred to in paragraph (1)(b) and subparagraph (2)(a)(ii), the following requirements apply:

• (a) subject to paragraph (b), the shell plating of a ship shall be drilled at such parts as may be considered necessary to ascertain its thickness and for this purpose the following requirements apply:

  • (i) the number of holes drilled on each side of the ship shall in no case be less than three in each strake of plating not covered with cement,

  • (ii) the holes shall be drilled about amidships and in the vicinity of the peak bulkheads,

  • (iii) all paint and rust shall be removed from the area of the plating surrounding the holes before the thickness of the plating is gauged,

  • (iv) the thickness of the plating at all holes drilled shall be recorded by the inspector, and

  • (v) the plating covered with cement in the bottom of a ship need not be drilled if, in the opinion of the inspector, the cement is adhering to the plating and it is unnecessary to drill at that place;

• (b) in the case of a Great Lakes ship, the inspector shall satisfy himself that the condition of the shell plating is satisfactory and in so doing he shall

  • (i) give special attention to those parts of the ship that are subject to damage in canals and locks and to all parts of the ship that are particularly subject to excessive corrosion or wear and tear, and

  • (ii) ascertain the thickness of the shell plating by drilling holes in such places as he deems necessary;

• (c) where the holds of a ship are insulated for the purpose of carrying refrigerated cargo, and the hull covered by insulation was inspected when the insulation was fitted, insulation additional to that removed pursuant to paragraph 26(j) shall be removed in each of the chambers in order to allow the condition of the framing and plating to be ascertained and the shell plating drilled as prescribed in paragraph (a); and

• (d) all mast and bowsprit wedging of a ship shall be removed whether the plating in way is doubled or not.