ISO 21963:2020

INTERNATIONAL ISO
STANDARD 21963
First edition
2020-09
Ships and marine technology —
Marine environment protection
— Tanks and piping systems for
facilitating 5 ppm oil-water separation
Navires et technologie maritime — Protection de l'environnement
marin — Réservoirs et systèmes de systèmes de tuyauterie utilisés
pour faciliter la séparation entre le pétrole et l'eau à 5 ppm
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Technical specifications . 1
4.1 Oil-water separation equipment (OWSE) . 1
4.2 5 ppm OWS . 3
4.3 Oil content meter (OCM) . 4
4.4 Automatic discharge stopping device (ADSD) . 4
4.5 Electric and electronic systems . 4
4.6 Heating facilities . 4
5 Installation requirements. 4
5.1 5 ppm OWS . 4
5.2 Oil content meter (OCM) . 5
5.3 Automatic discharge stopping device (ADSD) . 5
6 Testing of the 5 ppm OWS . 5
Annex A (informative) Examples of schematic diagrams for the management
of oil‑water effluents on fixed offshore marine structures . 6
Annex B (normative) Testing of 5 ppm OWS. 8
Annex C (normative) Environmental testing for the switchboard of the OWSE .18
Bibliography .20
Foreword
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This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology,
Subcommittee SC 2, Marine environment protection.
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iv © ISO 2020 – All rights reserved

Introduction
Marine environment protection is required by national, regional and international regulations.
The International Convention for the Prevention of Pollution by Ships (MARPOL) was adopted in 1973 and
it has been regularly updated by amendments made by the Marine Environment Protection Committee
(MEPC) of the International Maritime Organization (IMO). MARPOL is the legal basis for the prevention
of marine pollution. MARPOL requires the installation of oil-water separation systems to treat fluids
consisting of mixtures of oil and water generated on board ships.
On fixed offshore marine structures (e.g. converter stations and transformer substations of offshore
wind turbines), oil-in-water emulsions, oily mixtures of surface water, fuel and lubrication oil, and many
other substances covered by regulations might spill or otherwise cause hazards. Hence there is a need
to separate these mixtures to an oil concentration of less than what is currently required by MARPOL.
INTERNATIONAL STANDARD ISO 21963:2020(E)
Ships and marine technology — Marine environment
protection — Tanks and piping systems for facilitating 5
ppm oil-water separation
1 Scope
This document provides requirements and test methods for tanks, piping and separation systems
facilitating the separation of contaminated fluids of oil and water on fixed offshore marine structures
and ships, where treatment is performed by separation systems that optimize oil-water separation to a
concentration equal to or less than 5 ppm.
It is applicable to fixed offshore marine structures and to ships operating in designated sea areas
determined by the relevant authorities.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 8217, Petroleum products — Fuels (class F) — Specifications of marine fuels
ISO 9377-2, Water quality — Determination of hydrocarbon oil index — Part 2: Method using solvent
extraction and gas chromatography
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
parts per million
ppm
number of parts of oil per one million parts of water, expressed by volume
Note 1 to entry: 1 ppm equals to 1 μl of oil per 1 l of water.
3.2
ppm display
numerical scale display of the parts per million (3.1)
4 Technical specifications
4.1 Oil-water separation equipment (OWSE)
Oil-water separation equipment (OWSE) installed on fixed offshore marine structures shall be
constructed suitable for offshore use.
The OWSE shall comprise:
— an oil-water separator (5 ppm OWS);
— a 5 ppm oil content meter (5 ppm OCM); and
— an automatic discharge stopping device (ADSD).
If intended to be fitted in locations where flammable atmospheres can be present, OWSE are expected
to comply with the relevant safety regulations for such spaces. Any electrical or electronic equipment
which is part of the 5 ppm oil-water separation equipment shall be either intended and designated for
use in non-hazardous areas, or, if intended to be used in hazardous areas, it shall be type-approved by
the Administrations or recognized organizations on their behalf as safe for use in hazardous areas.
Figure 1 shows an example of the functional layout of an OWSE.
The OWSE shall be resistant to corrosion and to other conditions of the marine environment where it
is in use.
The OCM may include an oil content alarm.
An example of a schematic plan for the management of oil-in-water effluents in fixed marine offshore
structures is shown in Figure A.1.
An example of a schematic diagram for the management of the separation and treatment of oil-in-water
effluents on fixed marine structures is shown in Figure A.2.
Fixed offshore marine structures or ships fitted with an OWSE shall, at all times, have a copy of the
operating and maintenance manuals available.
2 © ISO 2020 – All rights reserved

Key
1 5 ppm OWS 8 ADSD
2 mixture inlet, filling and rinsing (oil-free water) 9 sampling location
3 discharge treated water, oil <5 ppm into the sea 10 back to bilge water holding tank or bilge
4 discharge separated media into waste oil tank 11 OCM
5 manual recirculation facility or valve for testing 12 flushing water inlet
(inherently safe)
13 back to bilge water holding tank or bilge
6 discharge for testing 14 flow switch controller
7 recirculation water, oil >5 ppm
Figure 1 — Example of functional layout of an OWSE
4.2 5 ppm OWS
The 5 ppm OWS shall be designed to reduce the oil content in an oil-in-water mixture to a volume
concentration equal to or less than 5 ppm.
The 5 ppm OWS shall be so designed that it functions automatically. However, fail-safe arrangements to
avoid any discharge in case of malfunction shall be provided.
The 5 ppm OWS may include any combination of a separator utilizing gravity separation, filtration, and
coalescence to produce an effluent with an oil content not exceeding 5 ppm by volume.
The 5 ppm OWS shall utilize a continuous automatic process and shall indicate when it is in operation. It
shall be capable of continuous operation for at least 24 h or normal duty without attention.
All parts of the 5 ppm OWS which are subject to wear and tear shall be easily accessible for maintenance.
4.3 Oil content meter (OCM)
The OCM shall be able to measure the oil content in the water mixture with a resolution of 1 ppm and
shall provide a ppm display. The ppm reading shall not be affected by emulsions and/or the type of oil.
The OCM shall give an alarm signal if the oil content exceeds 5 ppm in the effluent. The response time
of the OCM, that is the duration between a deviation in the sample being supplied to the OCM and the
display showing the current oil content (ppm), shall not exceed 5 s.
If the OCM is flushed with water for more than 5 s, the system shall create an alarm.
The accuracy of the OCM shall be checked at least every 5 years according to the manufacturer's
instructions. Alternatively, the unit may be replaced by a calibrated OCM. The calibration certificate for
the OCM, certifying the date of the last calibration check, shall be retained on the fixed offshore marine
installation for inspection purposes. The accuracy checks can
...