The slides, written out
AI-drawn illustration. Simplified to explain the idea, not to scale.
Slide 1 · P&A MANUAL & CDP PROCEDURES
P&A MANUAL & CDP PROCEDURES
How Chemical Tankers Manage NLS Residues Under MARPOL Annex II
1. CARGO DISCHARGE
2. CDP SELECTION
3. TANK CLEANING
4. DISPOSAL COMPLIANCE
Following the approved P&A Manual and correct CDP procedures ensures safe operations and full compliance with MARPOL Annex II.
Slide 2 · THE CDP NUMBER
THE CDP NUMBER
DECIDES THE PROCEDURE
The CDP number assigned in the vessel's approved
P&A Manual identifies the specific cleaning and
disposal procedure that must be followed for that
substance.
CDP 1b
CDP 2a
CDP 2b
CDP 3
CATEGORY X
& CERTAIN
HIGH-VISCOSITY
CATEGORY Y
STANDARD
CATEGORY Y
CATEGORY Z
VENTILATION
PROCEDURE
Requires prewash
and slops to
reception facility
before overboard
wash.
No prewash
required.
Wash water may
be discharged
overboard under
prescribed
conditions.
No prewash
required.
Wash water may
be discharged
overboard under
prescribed
conditions.
Select substances
may be cleaned
by approved
ventilation
procedures
without washing.
No alternative procedure may be used
without Administration approval.
Slide 3 · WHEN IS A
WHEN IS A
PREWASH REQUIRED?
The P&A Manual defines the cleaning sequence.
Prewash is required for certain cargoes only.
CDP 1b
CATEGORY X &
CERTAIN HIGH-VISCOSITY
CATEGORY Y
1 STRIP THE TANK
To the maximum extent
as per P&A Manual
(Section 3).
2 MANDATORY PREWASH
Immediate wash after
discharge as per Addendum B
(machine position, cycles,
pressure, hot/cold wash).
3 SLOPS TO RECEPTION
FACILITY
Prewash residues must be
discharged ashore.
4 SUBSEQUENT WASH
Full-cycle wash (k = 1.0 for ships
built on or after 1 July 1994).
May be discharged overboard
under prescribed conditions.
5 BALLAST / WASH TANK
To commercial
cleaning standards.
CDP 2a / 2b
CATEGORY Y
CATEGORY Z
1 STRIP THE TANK
To the maximum extent
as per P&A Manual
(Section 3).
2 NO PREWASH
Proceed directly to
subsequent wash.
3 SUBSEQUENT WASH
Full-cycle wash.
Wash water may be
discharged overboard
under prescribed
conditions.
4 BALLAST / WASH TANK
To commercial
cleaning standards.
Category X residues cannot be discharged into the sea
under any conditions and must be delivered to approved
reception facilities.
Slide 4 · MARPOL ANNEX II
MARPOL ANNEX II
DISCHARGE CONDITIONS
When discharging wash water overboard under CDP 2a or 2b,
all conditions below must be strictly met.
>12 NM
MORE THAN 12 NAUTICAL MILES FROM LAND
The ship must be more than 12 NM from the nearest land.
SHIP PROCEEDING EN ROUTE
The ship must be proceeding en route.
SPEED NORMALLY ≥ 7 KNOTS
Self-propelled ships must be proceeding at a speed normally
of 7 knots or more.
25 m+
WATER DEPTH GREATER THAN 25 METRES
Water depth at the discharge point must be greater than 25 metres.
THROUGH UNDERWATER DISCHARGE OUTLET
Discharge must be through the ship's approved underwater
discharge outlet.
FOLLOW VESSEL'S P&A MANUAL PROCEDURES
All steps, limits and operating parameters must comply
with the approved P&A Manual.
THREE DOCUMENTS EVERY OFFICER USES
P&A MANUAL
Contains approved
procedures, CDP tables,
stripping, prewash
(Add. B), ventilation
(Add. C) and flow
diagrams (Add. A).
CARGO
RECORD BOOK
Record every cargo
operation, tank
cleaning, prewash
and overboard
discharge accurately.
CERTIFICATE
OF FITNESS
Certifies the NLS
substances the ship
is approved to carry
under MARPOL
Annex II.
Correct CDP selection + approved procedures + accurate record keeping = ANNEX II COMPLIANCE.
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Drafted by SailR from our daily lessons. AI-drawn illustration. Simplified to explain the idea, not to scale. Last updated 19 Oct 2026.
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