Regulations on Crude Oil Washing Operations and COW Manual Contents

 General Requirements:

• This regulation comes under MARPOL Annex I, Chapter 4 - Requirements for the Cargo Area of Oil Tankers, Part C - Control of Operational Discharge of Oil, Regulation 35

• Every oil tanker operating with crude oil washing systems shall be provided with an Operations and Equipment manual detailing the system and equipment and specifying operational procedures.

• The Operation and Equipment manual shall be to the satisfaction of the Administration and if an alteration affecting to COW system is made, the Operations and Equipment manual shall be revised accordingly.

• For the ballasting of cargo tanks, sufficient cargo tanks shall be crude oil washed before each ballast voyage so that taking into account the tanker's trading pattern and expected weather conditions, ballast water is put only into cargo tanks that have been crude oil washed.

• Unless an oil tanker carries crude oil which is not suitable for crude oil washing, the oil tanker shall operate the crude oil washing system under the Operations and Equipment Manual. 

COW Operation and Equipment Manual:

• This Manual is written under the requirements of Administration relating to the International Convention for the Prevention of Pollution from ships.

• The purpose of the Manual is to meet the requirements for Crude Oil Washing under the specifications for the Design, Operation and Control of Crude Oil Washing systems.

• It provides standard operational guidance in planning and performing a crude oil washing programme and describes a safe procedure to be followed.

The Manual shall contain the following 18 sections:

Section 1: Text of the Revised Specifications

    This section contains the complete text of the revised Specifications for the Design, Operation and control of COW systems and the agreed interpretations to the provisions of the revised specifications.

Section 2: Drawings of the Crude Oil Washing System

The section contains line drawings showing:

1. Crude oil washing lines and valves.
2. Cargo pumps, lines and valves.
3. Ballast systems.
4. Stripping systems.
5. Position of tank washing machines.
6. Position of holes for hand dipping and tank gauges.
7. Inert gas deck distribution system.        

Section 3: Description of COW system & Operational & Equipment Parameters

The section contains  a description of the cargo, ballast, washing and stripping and in addition, specifies:

1. Types of tank washing machines and their standpipe length inside the tanks.
2. Revolutions of the machines.
3. Methods of checking the operation of tank washing machines.
4. Minimum operation pressure for crude oil washing.
5. The maximum permitted oxygen level in cargo tanks.
6. Duration of tank washing machine cycles.
7. Results of the tests performed and method of computation under the revised specifications.
8. Method of preventing entry of oil into the engine room.

Section 4: Dangers of and Precautions Against Oil Leakage

        This section contains information on the dangers of leakage from the crude oil washing system, the precautions necessary to prevent leakage and the action to be taken in the event of leakage. 

Section 5: Use and Control of Inert Gas

• This section contains information on the inert gas requirements and the instructions to cover those periods when the inert gas pressure is released for reasons of cargo operation.

• In addition, it indicates the method and procedures to be used for taking samples of the tank atmosphere.

Section 6: Precautions Against Electrostatic Hazards

        This section contains details of the procedures for minimizing electrostatic generation.

Section 7: Personnel Requirements

        This section specifies the number of people to be associated with the crude oil washing process and their necessary qualifications.  Their names and ranks may be provided on separate documents.

Section 8: Methods of Communication

        This section gives the details of communication between the watchkeeper on deck and the cargo control position so that, in the event of a leak or malfunctioning of the COW system, the washing may be stopped as soon as possible. 

Section 9: Determination of the Suitability of a crude Oil for use in Crude Oil Washing

• This section contains guidance in determining the suitability of crude oil for use in crude oil washing.

• As general guidance to the suitability of oil for crude oil washing on board a tanker, the following criteria should be used:

• For Aromatic crude oils whose kinematic viscosity is the temperature controlling characteristics, the kinematic viscosity of the oil used for crude oil washing should not exceed 60 centistokes at the oil wash medium temperature.

or

• For paraffinic crude oils whose pour-point temperature is the controlling characteristic, the temperature of the cargo to be used for the crude oil washing should exceed its cloud point temperature by at least 10 degrees celsius if excessive sludge is present and should only be used once in a 'closed cycle' washing programme.

• The list of crude oils unsuitable for carriage and crude oil washing to be inserted in the Crude Oil Washing and Equipment Manual, the following standard text may be used:

    For a Tanker not fitted with heating coils: 

• This tanker is not fitted with heating coils in the cargo tanks and should not carry cargoes that will require to be heated either to obtain pumpability criteria or to avoid excessive sludging of both the dedicated clean ballast tanks and the vessel's tanks to be washed for sludge control.

    For a Tanker fitted with heating coils in Slop Tank(s):

• This tanker is fitted with heating coils only in her slop tanks and should not carry cargoes that will require to be heated for pumpability.

    For a Tanker fitted with heating coils:

• This tanker is fitted with heating coils in all cargo tanks and, subject to the limitations of the cargo heating system, can carry cargoes that require heating for either pumpability or sludge deposition/control.

(Cloud Point Temperature: It is the temperature at which the crude oil's wax and associated oil phase separates from the bulk liquid phase of  the cargo)

 

Section 10: Crude Oil Washing Checklist

        This section contains operational checklists for the use of the crew at each discharge which shall include the checking and calibration of all instruments.

Section 11: Approved Methods and Programmes for Crude Oil Washing

        This section contains those details which form the basis of crude oil washing in the tanker and which are necessary to formulate a washing programme that will correspond with all predictable circumstances of cargo discharge restraints. It includes information on the following:

• The minimum number of tanks to be washed.

• The method of washing each tank, i.e. single or multistage.

• The number of tank washing machines to be used simultaneously.

• The crude oil washing pressure and the means to maintain the required pressure.

• The duration of crude oil wash.

• The preferred order in which tanks are to be washed.

• The minimum trim during the completion of washing and draining tanks.

• When draining and stripping of tanks is to commence. 

Section 12: Typical Crude Oil Washing Programmes

        This section contains the details of some typical washing programmes under various conditions of discharge such as single or multiport discharge, single and multigrade cargo.

Section 13: The Method of Draining Cargo Tanks

        The section contains a description of the method of draining cargo tanks and should include the parameters which indicate when the tank is dry and which will be at least all of those required by the revised specifications. The minimum trim conditions must be stated.

Section 14: The Method and Procedures for draining Cargo Pumps and Lines

        This section contains a description of the method and procedures for draining cargo pumps, cargo lines, crude oil washing lines and stripping lines and includes information on the use of the small-diameter line.

Section 15: Typical Procedure for Ballasting and the Method of Preventing Hydrocarbon Emissions

This section contains a description of typical procedures for ballasting and includes:

1. The procedure for draining and stripping before loading ballast.
2. The procedures for preventing hydrocarbon emission into the atmosphere

Section 16: Compliance Procedure for Regulation 9 of Annex I of MARPOL 73/78     

        This section contains information and procedures for water washing tanks and lines, discharge of departure ballast and the decanting of slops at sea to ensure compliance with Regulation 9.   

Section 17: Inspections and Maintenance of Equipment

        This section contains information on procedures to be followed at recommended intervals for onboard inspections and maintenance of crude oil washing equipment.

Section 18: Procedures for changing from Crude oil Trade to Product Trade

        This section contains operational procedures for changing from crude oil trade to product trade for a tanker which is fitted with separate independent pumping and piping arrangements for ballasting dedicated clean ballast tanks and which has been issued with two IOPP certificates running concurrently with one certificate certifying that the tanker to be a crude oil tanker and the other certifying it to be a product carrier.

Reference: IMO Publications and Documents - Specification and Manuals - Crude Oil washing systems -   Resolution MEPC.81(43)