MARPOL Consolidated Edition 2017

Chapter 4 - Requirements for the cargo area of o il tankers
Part A - Construction
Regulation 18
Segregated ballast tanks
SEE INTERPRETATION 34
Oil tankers of 20,000 tonnes deadweight and above
delivered after 1 June 1982
1 Every crude oil tanker of 20,000 tonnes deadweight and above and every product carrier of
30,000 tonnes deadweight and above del ivered after 1 June 1982, as defined in regulation 1.28.4, shall be
provided with segregated ballast tanks and shall comply with paragraphs 2, 3 and 4, or 5 as appropriate, of
this regu lation.
2 The capacity of the segregated ballast tanks shall be so determined that the ship may operate safely
on ballast voyages without recourse to the use of cargo tanks for water ballast except as provided for in
paragraph 3 or 4 of this regulation. In al l cases, however, the capacity of segregated ballast tanks shall be
at least such that, in any ballast condition at any part of the voyage, including the conditions consisting of
lightweight plus segregated ballast only, the ship's draughts and trim can meet the following requirements:
.1 the moulded draught amidships (dm) in metres (without taking into account any sh ip's deformation)
shall not be less than:
dm = 2.0 + 0.02L
.2 the draughts at the forward and after perpendiculars shal l correspond to those determined by the
draught amidships (dm) as specified in paragraph 2.1 of this regulation, in association with the trim
by the stern of not greater than O.Ol SL; and
.3 in any case the draught at the after perpendicular shall not be less than that which is necessary to
obtain fu ll immersion of the propeller(s).
3 In no case shall ballast water be carried in cargo tanks, except:
.1 on those rare voyages when weather conditions are so severe that, in the opinion of the master, it
is necessary to carry additional ba llast water in cargo tanks for the safety of the shi p; and
.2 in exceptional cases where the particular character of the operation of an oil tanker renders
it necessary to carry ballast water in excess of the quantity required under paragraph 2 of this
regulation, provided that such operation of the oil tanker falls under the category of exceptional
cases as established by the Organization.
SEE INTERPRETATION 35
Such additional ballast water shall be processed and discharged in compliance with regulation 34 of this
Annex and an entry shal l be made in the Oil Record Book Part II referred to in regulation 36 of this Annex.
4 In the case of crude oil tankers, the additional ballast permitted in paragraph 3 of this regulation shal l be
carried in cargo tanks only if such tanks have been crude oil washed in accordance w ith regu lation 35 of this
Annex before departure from an oil unloading port or terminal.
MARPOL CO SOLIDATED EDITION 2017 69