The Merchant Shipping (Prevention of Oil Pollution) Regulations 1996

Limitation of size and arrangement of cargo tanks

28.—(1) Every new oil tanker shall comply with the provisions of this regulation. Every existing oil tanker shall comply with the provisions of this regulation if—

(a) it was delivered to its first owner after 1st January 1977; or

(b) it was delivered to its first owner on or before—

(i) 1st January 1977; and

(ii) the building contract for the tanker was placed after 1st January 1974, or in cases where there was no building contract the keel was laid or the tanker was at a similar stage of construction after 30th June 1974.

(2) Cargo tanks of oil tankers shall be of such size and arrangement that the hypothetical outflow O_c or O_s, calculated in accordance with the provisions of Schedule 4 in Merchant Shipping Notice No. 1643/MARPOL 1, anywhere in the length of the ship does not exceed 30,000 cubic metres or 400³✓DW, whichever is the greater, but subject to a maximum of 40,000 cubic metres.

(3) The volume of any one wing cargo oil tank of an oil tanker shall not exceed 75 per cent of the limits of the hypothetical outflow O_c or O_s, referred to in paragraph (2). The volume of any one centre cargo oil tank shall not exceed 50,000 cubic metres. However, in segregated ballast oil tankers as defined in regulation 18 the permitted volume of a wing cargo oil tank situated between two segregated ballast tanks, each exceeding L_c in length may be increased to the maximum limit of hypothetical oil outflow provided that the width of the wing tanks exceeds t_c, where t_c is defined in Schedule 4 in Merchant Shipping Notice No. 1643/MARPOL 1.

(4) The length of each cargo tank shall not exceed 10 metres or one of the following values, whichever is the greater—

(a) where no longitudinal bulkhead is provided inside the cargo tanks, the lesser of—

; and

(ii) 0.2L;

(b) where a centreline longitudinal bulkhead is provided inside the cargo tanks—

;

(c) where two or more longitudinal bulkheads are provided inside the cargo tanks—

(i) for wing cargo tanks—

0.2L;

(ii) for centre cargo tanks—

(A) if

is equal to or greater than one fifth—

0.2L;

(B) if

is less than one fifth—

where no centreline longitudinal bulkhead is provided—

(0.5

where a centreline longitudinal bulkhead is provided—

(0.25

;

and in this paragraph “b_i” is the minimum distance from the ship’s side to the outer longitudinal bulkhead of the tank in question measured inboard at right angles to the centreline at the level corresponding to the assigned summer freeboard.

(5) In order not to exceed the volume limits established by paragraphs (2), (3) and (4) and irrespective of the type of cargo transfer system installed, when such a system inter-connects two or more cargo tanks, valves or other similar closing devices shall be provided for separating the tanks from each other. These valves or devices shall be closed when the tanker is at sea.

(6) Lines of piping which run through cargo tanks in a position less than t_c from the ship’s side or less than V_s from the ships bottom, where V_s is defined in Merchant Shipping Notice No. 1643/MARPOL 1, shall be fitted with valves or similar closing devices at the point at which they open into any cargo tank. These valves shall be kept closed at sea at any time when the tanks contain cargo oil, except that they may be opened for cargo transfer needed for the purpose of trimming of the ship.