4.1.1 This paragraph requires pipes and valves
to be of steel or other equivalent material. As classification societies
permit grey cast iron for cargo piping with a maximum permissible
working oil pressure of 16 kg/cm2, grey cast iron may be
permitted in the supply system for crude oil washing systems when
complying with nationally approved standards.
4.1.3 The requirements of this paragraph allow
alternative arrangements. One such alternative is that where the system
is served only by centrifugal pumps so designed that the pressure
derived cannot exceed that for which the piping is designed, a temperature
sensing device located in the pump casing is required to stop the
pump in the case of overheating.
4.1.6 On new oil tankers the steam heater referred
to shall be located outside the machinery spaces. However, on an existing
oil tanker with an existing steam heater located in the machinery
spaces, no more additional isolation will be required other than that
which isolates the crude oil washing system from the machinery spaces.
4.2.4 This paragraph requires each machine to
be capable of being isolated by means of stop valves in the supply
line. Where more than one submerged machine is connected to the same
supply line a single isolating stop valve in the supply line may be
acceptable provided the rotation of the submerged machines can be
verified in accordance with paragraph 4.2.13(a)
or (c) of the revised Specifications for the Design, Operation
and Control of Crude Oil Washing Systems.
4.2.8 With regard to the application of this paragraph
a slop tank is considered as a cargo tank.
Guidelines for the assessment of shadow
(a) Shadow diagrams (to be prepared in accordance
with 4.2.9) must be on drawings the
scale of which must be at least:
(i) 1:100 for tankers of less than 100,000 tons
(ii) 1:200 for tankers of less than 100,000 tons
deadweight and above.
(b) The drawings must provide at least a plan
view, a profile view and an end elevation for each tank, or for tanks
considered to be similar.
(c) Sufficient detailed drawings of the vessel
must be provided to check that all large primary structural members
have been included.
(d) The term “large primary structural members”
is to be construed as those components of a tank structure which contribute
significant strength to the ship, such as web frames and girders.
It is intended that smaller components such as those that contribute
to plate stiffening be excluded. In general the following lists, in
conjunction with the diagram showing structural components of cargo
tanks, may be used to amplify this interpretation. (See diagram on page 27.)
(e) Shadows cast upon the underside of decks,
web frames, centre and side girders can be ignored.
(f) Calculations must be provided either on the
drawing or separately to show how the percentages required by 4.2.8 have been arrived at. The calculations
should be itemized so that it is possible to relate each item with
a particular shadow area.
(g) Where a curved surface is presented to jets
it is not necessary to provide exact geometric projections to determine
the resultant shadow. A reasonable estimate is acceptable.
(h) For the purpose of determining the bottom
area of wing tanks, the breadth of the tank is to be taken as the
horizontal distance measured across the top of the bottom longitudinal
frames to the inside of the shell plating, midway between the tank
(i) A swash bulkhead may be taken as a tank boundary.
However, in this event the bulkhead must be assumed to have no openings
corrugations on corrugated bulkheads
crossties in transverse web frames, unless it can be verified by tank
inspection that their presence does not affect the cleanliness of the tank.
However, for the purpose of making an initial assessment, where there are no
more than two crossties and each is less than 1/15 of the total depth of the
tank they may be ignored.
4.2.10 “Water rinse” means the water
washing process carried out in connection with tank cleaning after
crude oil washing and is not intended to be construed as limiting
the amount of water needed in the process.
(a) The “oil monitoring system” referred
to in this paragraph means any approved system, including laboratory
tests, which verifies that the oil content of the effluent does not
exceed the stated level. If laboratory tests are to be conducted,
standards contained in resolution A.393(X) should be used as guidance.
Oil tankers engaging in a trade where discharge of cargo takes place
in one port State and cargo loading in another port State create a
special problem with respect to verification. Two alternatives available
to confirm the tanker's capability are:
(i) The tanker could be required to conduct the
entire COW operations at the discharge port, taking inspectors to
sea if necessary to observe water washing, handling of departure ballast
and discharge of arrival ballast;
(ii) Co-ordination between the flag State Administrations
and port States to obtain the required documentation.
However the test is performed, it should be decided on a case-by-case
basis taking into account the service of the tanker and the availability
(b) The expression “totally discharged to
the loading port harbour” which is used in this paragraph shall
be so construed as to mean the total quantity of arrival ballast except
that quantity which is to be retained on board as specified in section
15 of the Crude Oil Washing Operations and Equipment Manual.
4.4.3 During bottom washing the stripping capacity
shall be at least 1.25 times the total throughput of all the machines
that may be simultaneously in use according to paragraph 4.4.3. This does not mean that all the machines
in a tank have to be operated simultaneously during bottom washing
but the bottom washing may be carried out in steps according to detailed
procedures laid down in the Operations and Equipment Manual. The stripping
capacity should be at least 1.25 times the throughput of all machines
that are in operation simultaneously during any stage of the bottom
4.4.5 In crude oil tankers having individual cargo
pumps in each tank, each pump having an individual piping system,
dispensation from the required special small diameter line may be
given in cases where the combined amount of oil left in the tank after
stripping and the volume of oil in the piping system from the manifold
to the tank is less than 0·00085 times the volume of the cargo
tank. If a deepwell cargo pump system is provided with an evacuating
system for retained oil, the above consideration should also apply.
5.2(b) This paragraph requires that officers who
assume overall charge of a crude oil washing operation must have participated
in a crude oil washing operation on the ship for which they are required
to undertake the responsibility for cargo discharge, or on a similar
ship. However, for new ships, for ships changing for the first time
to the carriage of crude oil, for ships new to a particular owner,
or for ships which are changing registry in which it may not be possible
to acquire the particular experience, the Administration may accept
as an alternative:
(i) a person such as a shore-based senior officer
appointed by the company (additional to the ship's complement) who
is experienced in the operation of crude oil washing and is present
to advise the ship's personnel; or
(ii) a senior member of the crew such as the master,
chief officer or cargo control officer who has participated in at
least four crude oil washing operations and is on board the ship;
provided that an Operations and Equipment Manual, in a language
readily understood by the ship's officers, is available on the ship.