Annex I- Regulations for the Prevention of Pollution by Oil

Chapter 4 - Requirements for the cargo area of oil tankers. Part A - Construction

Regulation 26 - Limitations of size and arrangement of cargo tanks

1 Except as provided in paragraph 7 below:

.1 every oil tanker of 150 gross tonnage and above delivered after 31 December 1979, as defined in regulation 1.28.2, and
.2 every oil tanker of 150 gross tonnage and above delivered on or before 31 December 1979, as defined in regulation 1.28.1, which falls into either of the following categories:
  .2.1 a tanker, the delivery of which is after 1 January 1977, or
  .2.2 a tanker to which both the following conditions apply:
    .2.2.1 delivery is not later than 1 January 1977; and
    .2.2.2 the building contract is placed after 1 January 1974, or in cases where no building contract has previously been placed, the keel is laid or the tanker is at a similar stage of construction after 30 June 1974

shall comply with the provisions of this regulation.

2 Cargo tanks of oil tankers shall be of such size and arrangements that the hypothetical outflow Oc or Os calculated in accordance with the provisions of regulation 25 of this Annex anywhere in the length of the ship does not exceed 30,000 cubic metres or , 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 oil outflow referred to in paragraph 2 of this regulation. 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 of this Annex, the permitted volume of a wing cargo oil tank situated between two segregated ballast tanks, each exceeding lc in length, may be increased to the maximum limit of hypothetical oil outflow provided that the width of the wing tanks exceeds tc.

4 The length of each cargo tank shall not exceed 10 m or one of the following values, whichever is the greater:

.1 where no longitudinal bulkhead is provided inside the cargo tanks:

where a centreline longitudinal bulkhead is provided inside the cargo tanks:

but not to exceed 0.2L


where two or more longitudinal bulkheads are provided inside the cargo tanks:

  .3.1 for wing cargo tanks: 0.2L
  .3.2 for centre cargo tanks:
    .3.2.1 if is equal to or greater than one fifth: 0.2L
    .3.2.2 if is less than one fifth:

where no centreline longitudinal bulkhead is provided:


where a centreline longitudinal bulkhead is provided:

bi 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 of this regulation and irrespective of the accepted type of cargo transfer system installed, when such system interconnects 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 tc from the ship's side or less than vc from the ship's bottom 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 only for cargo transfer needed for the purpose of trimming of the ship.

7 This regulation does not apply to oil tankers delivered on or after 1 January 2010, as defined in regulation 1.28.8.