MARPOL Consolidated Edition 2017

Chapter 4 - Design, construction, arrangement and equipment
Regulation 12
3 Every ship constructed on or after 1 January 2007 shall be provided with a pumping and piping
arrangement to ensure that each tank certified for the carriage of substances in category X, Y or Z does not
retain a quantity of residue in excess of 75 L in the tank and its associated piping. A performance test shall be
carried out in accordance with appendix V of this Annex.
4 For a ship other than a chem ical ta1nker constructed before 1 January 2007 w hich cannot meet the
requirements for the pumping and piping arrangements for substances in category Z referred to in paragraphs
1 and 2 of this regulation no quantity requirement shal l apply. Compliance is deemed to be reached if the tank
is emptied to the most practicable extent.
5 Pumping performance tests referred to in paragraphs 1, 2 and 3 of this regulation shal l be approved by
the Administration. Pumping performance tests shall use water as the test medium.
6 Ships certified to carry substances of category X, Y or Z shall have an underwater discharge outlet (or
outlets).
7 For ships constructed before 1 January 2007 and certified to carry substances in category Zan underwater
discharge outlet as required under paragra[Ph 6 of this regulation is not mandatory.
8 The underwater discharge outlet (or outlets) shall be located within the cargo area in the vicinity of the
turn of the bilge and shall be so arranged as to avoid the re-intake of residue/water mixtures by the ship's
seawater intakes.
9 The underwater discharge outlet arrangement sha ll be such that the residue/water mixture discharged
into the sea will not pass through the ship's boundary layer. To this end, when the discharge is made normal
to the ship's shell plating, the minimum diameter of the discharge outlet is governed by the following equation:
Qd
d = Sld
where
d
Ld
Qd
= minimum diameter of the discharge outlet (m)
= distance from the forward perpendicular to the discharge outlet (m)
= the maximum rate selected at w hich the ship may discharge a residue/water mixture
through the outlet (m 3 / h).
10 When the discharge is directed at an angle to the ship's shell plating, the above relationship shall be
modified by substituting for Qd the component of Qd w hich is normal to the ship's shell plating.
11 Slop tanks
Although this Annex does not require the fitting of dedicated slop tanks, slop tanks may be needed for certa in
washing procedures. Cargo tanks may be used as slop tanks.
MARPOL CONSOLIDATED EDITION 2017 181