General Awareness of Safe Cargo Operational Procedures on Tankers

Trainees should be capable of assisting during cargo operations on board and may be part of the watchkeeping team in port. The aim is to familiarize trainees with operational sequences, duties, and responsibilities of personnel on watch during operations.

For Oil Tankers This section introduces oil tanker operations, covering:

  • Loading
  • Loaded voyage
  • Unloading
  • Ballast voyage
  • Tank cleaning
  • Crude oil washing
  • Use of inert gas
  • Purging and gas-freeing
  • Tank cleaning and gas-freeing for repairs

For Chemical Tankers This section introduces chemical tanker operations, covering:

  • Cargo information
  • Cargo planning
  • Loading
  • Unloading
  • Tank cleaning and gas-freeing
  • Slops and slops disposal

The purpose is to provide trainees with a general explanation of sequences in cargo, ballast, and slop-handling operations, and how they are linked. Use schematic drawings and simulator photographs. Training is preferably conducted on an oil and chemical simulator.

For Oil Tankers 

Cargo Information

Information is found in:

  • Material Safety Data Sheets (MSDS) for oil cargoes, supplied by shippers.
  • Cargo Data Sheets published by ICS for chemical cargoes.

These sheets include all necessary data for safe handling and carriage of the cargo.

Loading

Safety Confirmations and Clearance Once the Chief Officer confirms all preparations align with the cargo oil loading plan and the shore facility representative confirms readiness:

  • Order opening of designated manifold valves.
  • Commence loading at reduced rate (to avoid static generation), monitoring manifold back pressure.
  • Document the first loading tank in the Tanker Cargo Log Book; restrict the number of initial tanks.
  • Confirm ullage to verify cargo flows as planned.
  • For heated cargo: Confirm temperature matches agreed value and Charterer’s instructions, and is within vessel design criteria (valve/tank coating limitations).
  • After safety checks from all deck/pump room stations, open other loading tanks and increase rate carefully.
  • Maintain close watch on manifold back pressure until final maximum agreed rate stabilizes.
  • Keep communication with shore until parameters stabilize.
  • Adjust Inert Gas (IG) back pressure to maintain slight positive pressure; monitor for changes.

Deck Watch and Personnel Arrangement

  • Deck watch checks for oil leaks in cargo area throughout operations.
  • At start: Confirm no leaks from piping joints and no unintended flow into other tanks.
  • Continuously monitor oil levels in loading tanks until shore flow rate stabilizes; monitor unused tanks for changes.
  • After reaching desired rate and confirmation from all stations (including cargo piping and sea surface), Chief Officer may dismiss off-duty crew and revert to routine watch schedule.
  • Monitor manifold back pressure during valve/tank changeovers.

Leakage Monitoring System

  • Address even small cargo leakages early.
  • Monitor leakages from piping, joints, and valves.
  • Ensure no oil flows into non-loading tanks.
  • Watch loading pressure continuously and monitor likely leak points.
  • Attend to excessive piping vibrations immediately.

Cargo Loading Rates a) General Vessel’s maximum loading rate and venting capacity must be posted in the cargo control room, detailing rates for homogeneous (entire vessel), group-by-group, and tank-wise loadings. This helps the Master determine safe loading rates based on design parameters and cargo.

Chief Officer indicates rates in stages in the loading plan.

  1. b) Theoretical Rates Maximum flow into any single tank < maximum venting capacity (SOLAS). Venting rate taken as 125% of oil loading rate (to account for gas generation).

Factors affecting maximum rates:

  • Manifold diameter
  • Number of tanks loaded
  • Gas venting capacity
  1. c) Setting Loading Rates Consider initial/maximum/topping-off rates and stopping times, regarding:
  • Nature of cargo
  • Ship’s cargo lines and gas venting arrangement/capacity (vent pressure must not exceed builder’s limit; monitor closely at high-rate terminals)
  • Builder’s vent pressure may assume all tanks simultaneous; reduce for fewer tanks
  • Age, condition, and reliability of pipeline/venting systems
  • Precautions against static electricity
  • Any other limitations

De-Ballasting of Segregated Ballast

  • Obtain Berth (Loading) Master’s permission before starting.
  • In principle, commence de-ballasting after cargo operations start.
  • De-ballast per cargo plan to achieve ample trim, especially near completion.

Planning for Topping-Off

  • Such period (topping-off) should be planned well before the level in cargo tanks approaches topping-off ullages.

Cargo Sampling Requirements & Procedures

In any bulk liquid shipment (chemical, petrochemical, petroleum product, or crude oil), comprehensive and reliable control procedures are required to identify and minimize the effects of potential cargo contamination.

  • Cargo sampling and sample retention provide the most effective means to determine when and/or how contamination might have occurred, allowing unfounded allegations of shipboard liability to be challenged.
  • This is the most potent tool available to ship’s officers, who otherwise depend on the competence and integrity of locally appointed surveyors.

Purposes of Sampling:

  • For high-purity cargoes: Inspection of samples at the manifold or ‘first-foot’ level in cargo tanks allows assessment of incoming cargo quality and line cleanliness.
  • Visual inspection (not immediate analysis) checks for:
    • Changes in colour
    • Presence of water (if insoluble in cargo)
    • Presence of foreign particulate matter
    • Odour taint (less straightforward; not applicable to all cargoes)
  • Toxic or highly odoriferous cargoes should not be tested for odour.
  • Any observed quality deviation requires immediate halt of cargo operations and further investigation.

Main Shipboard Sampling Points:

  • Manifold: At commencement of loading and spot checks during loading (special care during shore tank switches).
  • Ship’s cargo tanks: At ‘first-foot’ level.
  • Ship’s tanks: After loading.
  • Ship’s tanks: Before discharge.
  • Ship’s manifold: At commencement of discharge and spot checks during discharge.

Sampling Compliance:

  • Follow industry standards (ASTM, IP, ISO, etc.).
  • For high-purity cargoes: Use a ‘running’ sample from each shore tank.
  • If cargo is not homogeneous: Use careful ‘zone’ sampling to assess quality.
  • Dangerous chemical cargoes may require specialized sampling techniques, equipment, and points as prescribed by the equipment in use.
  • Safety is paramount with toxic or dangerous cargoes.

Sample Containers:

  • Clear glass bottles: Most useful for visual checks.
  • Brown glass bottles: For light-sensitive cargoes (e.g., some kerosene, amines, phenol).
  • Plastic containers: For caustic soda, potash, etc.
  • Lacquer-lined tinplate containers: Generally unsuitable for chemical cargoes (used for petroleum products).
  • Closures: Choose cargo-specific; polypropylene or PTFE inserts preferred.
    • Waxed disc types: Suitable only for petroleum products and crude oils.
    • Aluminium foil-faced discs: Unsuitable for acid/alkaline samples.

Sample Size and Labelling:

  • Capacity: 500 ml.
  • Label clearly with: Ship’s name, date, time, port, sample location, sample type (e.g., running), sampler’s identity.
  • Samples must be signed, sealed, and (if possible) counter-signed by the local surveyor.

Sample Retention:

  • Ideally retain in a dedicated locker on board for 12 months (often impractical).
  • Retain until instructed otherwise if quality query arises.
  • Normally handed to P&I Association representative in case of a claim.

Unloading 

Operation of Cargo Pumps:

  • When starting to ballast, operate cargo pumps to prevent oil escape overboard when sea suction valve is opened.
  • Refer to ICS/OCIMF publication “Prevention of Oil Spillages Through Cargo Pumproom Sea Valves”.

Sequence of Valve Operations (for loading ballast into non-inerted tanks containing hydrocarbon vapour):

  • Open tank valves first.
  • Restrict initial ballast flow so entrance velocity < 1 meter/second until:
    • Longitudinals are covered, or
    • Ballast depth ≥ 1.5 metres (if no longitudinals).
  • This prevents geyser effect leading to electrostatic charge buildup in mist/spray cloud, potential discharge, and ignition.

Preparation and Meetings:

  • Chief Officer prepares watch schedule and Person-in-Charge list for oil transfer operations during discharge.
  • Conduct “Pre-transfer cargo safety meeting” with concerned crew; duty officer reads discharge plan aloud.
  • Discuss special details, port requirements, precautions, and procedures.

Preparation for Cargo Equipment:

  • Cargo oil transfer pumps and Inert Gas System (IGS) well prepared before arrival at discharge port.

Cargo Oil Transfer Check Lists:

  • Chief Officer completes checklists prior to, during, and upon completion of operations; signs them.
  • Master signs completed “Tanker Discharging Checklist”.
  • For multi-port discharge: Pre-arrival tests can be completed before first port.
  • Relevant checklists: “Crude Oil Washing Checklist”, “Ship/Shore Safety Checklist”, “Double Hull Operation/COT Monitoring Record”, “Ship to Ship Transfer Checklist” (as required).

Display of Warning Notices and Signs:

  • Take into account and display appropriately.

Hose Connection:

  • Chief Officer or deck duty officer must attend during connection of cargo oil transfer arms/hoses.

Cargo Oil Transfer Meetings:

  • Master, Chief Engineer, and Chief Officer attend “pre-transfer cargo safety meeting” with terminal representative.
  • Ensure agreement on discharge plan and emergency communication method.
  • Complete and sign “Ship/Shore Safety Check List” or relevant “Ship to Ship Transfer Check List” after safety checks, before starting operations.

Ullage Measurement and Cargo Quantity Calculation:

  • Performed by terminal side or surveyors (ullage, temperature, water, sampling).
  • One watch officer attends measurements and assists in cargo quantity calculation.
  • Ensure all ullage ports (vapor locks) and openings closed after measurement and before operations start.

Lining up Pipelines and Valves:

  • Prepare lines between tanks and pumps after ullage measurement.
  • Mark and protect tanks not to be discharged from accidental operation.
  • Fill separator with caution to avoid “Liquid Hammer”; ensure even filling with vapor passage.
  • Set cargo tank line and pump room valves per plan before discharge start.
  • Use ship-specific ‘Valve Checklist’ prudently.
  • Secure and lash shut valves not in use.
  • Supervise and check line/valve settings by Watch Officer; re-confirm by Chief Mate.
  • Open manifold valves only on Chief Officer’s permission; monitor manifold pressure regularly.
  • Operate major valves per terminal representative’s order.

Personnel Arrangement at Beginning of Operations:

  • All deck crew attend and distribute as per Chief Officer’s instruction for startup.

Tool Box Meeting:

  • Remind crew of safety: No smoking/use of fire, designated emergency exits, other matters.

Additional Safety Notes on Tank Atmosphere:

  • In inerted cargo tanks: No explosive atmosphere; avoid flammable range during gas-freeing.
  • Soot particles in inert gas create additional ignition hazard in explosive atmosphere.
  • Gas-freeing non-inerted tank brings atmosphere into explosive range temporarily.
  • Oil tankers supplied with meters for oxygen content, hydrocarbon content, toxic gas content.
  • Meters show percentage Lower Flammable Limit (LFL) by volume.

Tank Cleaning and Gas-Freeing for Repairs:

  • Procedures for tank cleaning, purging, and gas-freeing must be followed.
  • Before personnel entry: Check atmosphere for oxygen (must be 21% by volume), hydrocarbon (< 1% LFL), and toxic gas (after certain cargoes).
  • After tank washing: Manual residue removal may be needed (generates more hydrocarbon gas).
  • Gas-freeing must be continuous.
  • Adjacent bulkheads/pipelines may add hydrocarbon gas.
  • Shut off inert gas supply to tank.
  • Gas-free certificate from qualified chemist required before contractor work.
  • Additional hot work permit for hot work; reissue daily or as per port authority.
PreviousNext