Cargo Information 

• Information about cargoes is essential for vessel and crew safety.
• Found on ICS or other Cargo Data Sheets for each product, including data for safe handling and carriage.
• Cargo information kept on board and available to all concerned.
• Cargo not loaded unless sufficient information for safe handling/transportation available.
• Responsible officer posts necessary cargo information on notice board before operations.
• All personnel engaged in cargo operations familiarize themselves by studying ICS or other Cargo Data Sheets.
• Chemical tanker operations may involve simultaneous loading, unloading, and tank cleaning.

Loading 

• All personnel follow standing instructions at all times (whether cargo dangerous or not).
• Personnel on watch/involved wear appropriate protective clothing per ICS or other Cargo Data Sheets for dangerous cargoes.
• Cargoes stowed per pre-prepared stowage plan.
• Prior to loading: Inspect cargo tanks for cleanliness and suitability per stowage plan.
• For cargoes with major fire hazard: Purge tanks with nitrogen to remove air (non-flammable atmosphere above cargo); maintain nitrogen “padding” during voyage.
• Cargo routing from manifold to tanks:
  • On chemical tanker with pump-room.
  • On chemical tanker with separate lines for each tank.
• Cargo vapour removal during loading.
• “Closed-circuit” loading operation.
• For cargoes with major health hazard vapours: Load in “closed circuit” with vapour-return line.
• Check for impurities: Take cargo samples from lines and tanks during loading.
• Adjust vessel’s trim, list, and stability (if necessary) by filling/emptying ballast tanks during loading.
• Record all events during cargo operations.

Unloading 

• All personnel follow standing instructions at all times during unloading (whether cargo dangerous or not).
• Personnel on watch/involved wear appropriate protective clothing per ICS or other Cargo Data Sheets for dangerous cargoes.
• Unload cargoes per planned sequence of emptying tanks.
• Prior to unloading: Analyze cargo samples from each tank and cargo lines to check for on-board contamination during passage.

Pumps and Unloading Systems of a Chemical Tanker Types of Pumps Used:

• Centrifugal pumps
• Screw pumps
• Piston pumps (reciprocating pumps)

Main Cargo Pumps:

• Mainly centrifugal type.
• Either submerged pumps integral with hydraulic motors or extended shaft with deck-mounted electric motors (deep well pumps).

Benefits of Centrifugal Pumps:

• Simple construction (no valves).
• Relatively small size (can operate at high speed).
• Continuous pumping (no pulsation).

Drawbacks of Centrifugal Pumps:

• Difficulty constructing for high differential pressure per stage.
• High efficiency only within limited field.
• Normally not self-priming.
• Back flow through pump when stopped.
• Difficulty pumping high-viscosity liquids.

Pump Characteristics:

• Supplied with graph (performance curve) based on tests with specific liquid, temperature, density, impeller, and revolution rate.
• Includes: Q-H curve (total head vs. flow), power consumption, efficiency, NPSH.
• Design point: Best general result for efficiency, NPSH, power, flow.
• Total head independent of liquid density; differential pressure and power consumption vary proportionally with density.
• Curves for specific liquid; remember when evaluating.

Demonstration (use simulator drawings from Appendix 1 section 2):

• Cargo routing from tank to manifold on chemical tanker with pump-room.
• Cargo routing from tank to manifold on chemical tanker with deep well pumps and separate lines for each tank.
• Functioning of cargo-tank venting system during unloading.

Additional Unloading Notes:

• In tanks with major fire hazard cargoes: Use inert gas or nitrogen to maintain positive tank pressure during unloading (avoid air entry).
• Adjust vessel’s trim, list, and stability (if necessary) by filling/emptying ballast tanks during unloading.

Tank Cleaning and Gas-Freeing 

Reasons for Tank Cleaning:

• Prevention of contamination of the cargo to be loaded.
• Prevention of contaminated ballast.
• Maintenance of cargo tanks and equipment.

Tank-Washing Machines:

• Used for tank cleaning.
• May be fixed or portable.
• Tank-cleaning equipment must be properly earthed to avoid accumulation of static electricity.

Personnel Safety:

• Personnel involved in tank-cleaning operations may be exposed to cargo vapours.
• Use equipment for personal protection if necessary.

Tank-Cleaning Procedures:

• Different cargoes require different procedures.
• Cleaning may be done with:
  • Hot or cold seawater
  • Fresh water
  • Ventilation only
• Water cannot be used for tank cleaning before or after some cargoes.
• In some cases, detergents are added to the washing water.
• In some cases, solvents are used for tank cleaning.

Use Diagrams:

• Use the diagram in Appendix 1 Section 2 of this course to explain:
  • The working of a tank-washing machine.
  • How the electric bonding of tank-cleaning hoses may be checked.
  • A safe procedure for the connection and disconnection of tank-cleaning equipment.

Tank Cleaning Sequence:

• Pre-wash
• Main wash
• Fresh water rinse

Gas-Freeing:

• Purpose: Replace cargo vapours, inert gas, or any other gases with air.
• May be done by fixed or portable fans driven by air, steam, water, or hydraulic fluid.
• Operation verified by regular checks of the tank atmosphere.
• Tank atmosphere checked by measuring:
  • Percentage of oxygen
  • PPM values of cargo vapours or toxic constituents of inert gas
• A cargo tank is gas-free only when:
  • Oxygen content is 21% by volume
  • No vapours from cargo or toxic constituents of inert gas measured above the Threshold Limit Value (TLV)

Slops and Slops Disposal:

• Modern chemical tankers fitted with tanks for storage of slops.
• Cargo tanks may also contain slops.
• Discharge of slops into the sea prohibited unless certain conditions satisfied.
• Slops from certain noxious chemicals discharged to shore facilities.
• All slop-handling operations recorded in the Cargo Record Book.