OTM-7.9	Oil Tanker Manual OTM Cargo Care During Voyage	Doc No.: OTM 7.9 Revision: 01 Date: 15 Oct 2024 Issued by: DPA Approved by: MD

1. APPLICATION

This document applies to all officers onboard fully managed tanker vessels.

2. PURPOSE

The purpose of this document is to specify cargo care procedures during voyage.

3. RESPONSIBILITIES

• Chief Officer: Overall in charge.
• Deck Officers: To assist the chief officer as required.
• Chief Engineer: Overall in charge for availability of machinery required for cargo care.
• Watch Keepers: Assist the chief officer & deck officers.

4. CARGO HANDLING AND OPERATIONAL TESTS DURING VOYAGE

Cargo Heating

Refer to OTM 7.13 – Cargo Heating.

Preventing Vapour Loss

• Monitor escape of cargo vapour by checking PV valves.
• Ensure all hatch lids, ullage ports, and other tank openings are gas-tight.
• Maintain inert gas blanket on cargo throughout voyage using the inert gas system as necessary.
• Keep tanks under a good positive pressure at all times.

Prevention of Grade Contamination by Cargo Vapour

Cargoes of different vapour pressure carried with a common venting system can lead to contamination.

• Isolate the venting systems for the two grades if possible.
• Use the individual PV valves (if fitted), for pressure control.
• Follow any specific instructions from charterers.

Pre-arrival Checks, Tests, and Inspections

Carry out the following tests, inspections, and checks during the laden passage, before arrival at discharge port:

• Hydraulic Systems
  • Activate hydraulic system and check for leakage.
  • Ensure that the motors are working properly.
  • Check operation of valves.
  • Check operation of high and low pressure alarms, low oil level, and auto stop/start systems.
  • Overhaul portable hydraulic hand pumps if necessary.
• Inert Gas System – Refer to OTM 7.10 – Inert gas system.

5. OPERATIONAL CHECKS FOR TANK VESSEL DURING SEA PASSAGE

Carry out the below checks/controls during sea passage based on the nature of cargoes carried:

• Daily Check of Pump Room
  • Check hydrocarbon gas to detect cargo leakage.
  • Bilge sounding to detect water leakages.
• Control of Valves
  • Cargo segregation or mixing or contamination.
  • Tagging of valves: When the vessel is carrying more than one grade, tag the valves of each grade by different colour.
  • Avoid inadvertent access or operation of valves.
  • Keeping the cargo control room and/or hydraulic room locked.
  • Use ‘Lock out – Tag out’ procedure to identify and isolate the grades.
• Segregation of Venting Lines to avoid vapour contamination
  • In case of common venting lines, keep tank isolation valves shut.
  • Check inert gas pressure regularly.
  • Lock tank isolation valves to avoid inadvertent operation.

  Note:

  • Chief Officer should have the keys to the I.G. isolation valve locks.
• Cargo Tanks Level
  • Investigate any variation in the tank level immediately.
• Cargo Tank or Line Pressure
  • Monitor and maintain cargo tank/line pressure within design limits to avoid structural damage.

  Coution:

  • Structural damage of tanks / lines can lead to serious pollution.
  • Top up inert gas if tank pressures fall below 100 mmwg.
  • If the pressure increases, it may have to vent off using mast riser or PV valves.

  Note:

  • In case of releasing toxic vapours, refer to ECP matrix A13 Hazardous vapour release.
  • Cargo lines also suffer over and under pressurization due to an increase or fall in the temperature of the cargo in the line.
  • Release line pressure one by one, by crack opening the drop valve and the goose neck valve to the cargo tank.
• Cargo Temperature
  • For heated cargoes, follow heating instructions given by the shipper.

  Note:

  • 1. Heating instruction will specify voyage/discharge temperatures and maximum temperature rise per day.
  • 2. Once daily: For heat sensitive cargoes (eg Phenol, Acrylic acid) temperatures: additionally- adjacent cargo tanks temperature should be monitored and recorded.
  • In case of any doubt, Marine superintendent should be contacted.
  • Maintain daily cargo temperature record.
  • If in a hot climate (e.g., warm seawater and sun warming up the deck), a more frequent check may be necessary.
  • If temperature starts rising to a dangerous level, put cooling systems into operation.
  • For cooling, circulate cold fresh water in the heating coils, and/or flush deck by ambient seawater.
• Inspection of Cargo Lines
  • If loaded with multiple grades, do not pressure test the cargo lines, nor try out the cargo pumps.
  • If the vessel is regularly involved in multiple grade loading, then pressure test the lines and try out of cargo pumps during tank cleaning.
• Gas Detection and Sounding of Empty Tanks Adjacent to Cargo Tanks
  • On vessels without fixed gas detection systems or fixed gas detection system without recorders for void and ballast spaces within the cargo tank area, regularly monitor for hydrocarbon content with portable equipment.
  • Include sounding and ullaging of the empty spaces to detect cargo or water leakages.
  • Monitor non-cargo spaces within the cargo tank area as follows:
    • Soon after each loading operation
    • Everyday during loaded passage and immediately prior to arrival at port
    • Prior ballasting
    • In unusual events such as grounding, collision, contact damage, after a period of very heavy weather, or any other unforeseen operational problems
    • Every third day during ballast passage (sounding or ullaging only)
  • When on short coastal voyages, which make the above regulations impractical to follow, visual inspection of the tanks or the ballast water is a suitable alternative measure.
  • Record the test results.
  • During voyage, gas-monitor all void spaces every day and record results.