ISSUE 1 emphasized important viewpoints on preparing tanker ships for green recycling
Expert Insights: Preparing Tanker Ships for Green Recycling & Safety Measures
ISSUE 2 focused on Purging and Gas Freeing Operation for Man Entry
Expert Insights: Purging and Gas Freeing Operation for Man Entry

ISSUE 3

GMS Trader Kiran Thorat highlights – Man Entry and De-mucking process

A manned entry should be conducted for inspection once the Cargo Oil Tanks (COTs) have been thoroughly purged with inert gas and subsequently gas-freed using fresh air. Given that COTs are classified as enclosed spaces, it is essential that an Enclosed Space Entry Permit is completed by a responsible officer from the vessel's crew prior to any personnel entering the tank.

Pre-entry preparations:

The standby team at the tank entrance must be exclusively assigned to the designated man entry operation. Under no circumstances should they leave their position without an appropriate replacement. At a minimum, a self-contained breathing apparatus (SCBA), stretcher, and emergency escape breathing device (EEBD) must be readily available at the tank entrance. Additional safety equipment may be utilized based on a specific risk assessment of the cargo tank atmosphere’s toxicity. A complete permit for the workspace must be prominently displayed at the entrance of the Cargo Oil Tank (COT) after all checks are finalized and the permit has been issued by the officer responsible.

Illumination:

Personnel entering Cargo Oil Tanks (COTs) must wear full Personal Protective Equipment (PPE). Due to the typically slippery surfaces within COTs, adequate illumination is critical. Lighting should be provided using portable lamps with low-voltage, preferably 12-volt, power sources to minimize the risk of electric shock from the vessel's main power supply. Alternatively, compressed air-driven lighting may also be used to ensure safe visibility within the tanks.

Ventilation:

• Isolate the relevant cargo tank from adjacent tanks to prevent accidental entry of cargo liquids or vapors through piping systems or connections.

• Keep suction and stripping valves closed and implement lockout/tagout procedures before starting operations.

• Ensure all IG isolation valves are closed and locked to prevent hazardous or toxic vapor migration into the tank being de-mucked.

• Maintain continuous ventilation of Cargo Oil Tanks (COTs) using air-driven portable blowers or inert gas blowers in fresh air mode.

• Monitor atmospheric conditions inside COTs periodically, ensuring oxygen levels are at or above 21% and hydrocarbon levels are below 1% of the Lower Flammable Limit (LFL), while all personnel must carry calibrated personal gas meters.

Communication:

Personnel entering Cargo Oil Tanks (COTs) must maintain close communication with the standby team positioned outside the tank. The standby team, in turn, should establish continuous communication with the command center, such as the navigation bridge, to ensure coordinated safety and rapid response capability. The interval between two communication checks should be briefed to all participating members of the operation as per the enclosed space entry permit. Actions to be taken in case of loss of contact.

De-mucking:

Oil tankers transport various grades of oil, broadly categorized as clean and dirty products. Over multiple voyages, solid sludge residues accumulate on internal structures, such as steel supports, stringers, and longitudinal, within cargo tanks. De-mucking is the process of manually removing these Solid Sludge Residues (SSR) from tank structures.
The removed sludge is collected in bags that must be securely sealed to prevent spillage. These bags are then lifted to the main deck using portable winches, typically positioned over manhole doors, which are designed to accommodate loads of approximately 10 to 20 kg of SSR at a time. The winches used for lifting are either pneumatically powered or manually operated.
Complete SSR removal is required throughout the full height of the Cargo Oil Tanks (COTs). For areas beyond manual reach, specially trained personnel with rope access qualifications are needed to reach higher sections. De-mucking is a demanding and labor-intensive operation; as such, external contractors are often engaged, bringing skilled personnel who work in rotating teams to ensure thorough removal. This process is particularly time-consuming on single-hull tankers compared to double-hull tankers due to structural differences.

Equipment:

De-mucking operations require specialized equipment, including shovels, scrapers, heavy-duty jumbo vinyl bags, portable fans, air compressors, wilden pumps, air hoses, portable lamps, and tripods. These tools are essential for the effective and safe removal of sludge from cargo tanks, ensuring that personnel can operate efficiently while maintaining safety standards.

Precautions:

• Disturbing SSR during collection can result in significant emissions of hydrocarbon vapors and toxic gases, which may unexpectedly elevate gas concentrations above safe levels. Continuous ventilation with flexible ducts, positioned directly at the cleaning site, is essential to disperse these emissions effectively.

• Manhole openings should be clearly marked with guards and safety warning signs to prevent falls.

• Designated smoking areas must be established for workers and vessel staff to maintain safety protocols.

• After any break in the operation, cargo tanks should be re-assessed for oxygen and hydrocarbon levels before personnel re-entry to ensure atmospheric safety.

• Care should be taken when lowering and handling tools to prevent them from falling from a height or creating sparks, both of which could pose ignition hazards.

Disposal of SSR:

SSR bags must be gathered in skips and subsequently offloaded to an authorized shore reception facility to ensure compliant and environmentally responsible disposal.

For more information or any clarification, please write to bd@gmsinc.net