GMS Tanker Expert and Trader, Kiran Thorat shares important viewpoints to increase awareness about Tanker ships; preparing tanker ships for green recycling and safety measures that should be incorporated among stakeholders in ship recycling industry.

Tanker ships are used extensively worldwide to transport various grades of oils in bulk. Globally, diverse types of tankers operate according to their size and the grade of cargoes they carry.
As of September 2024, there are more than 1300 tanker vessels aged above 20 years and about 2100 tanker vessels aged between 15 to 19 years.
With ongoing geopolitical situation, disruption in supply leading to an increase in oil price, some of the tankers continue to operate. Most of the Tankers will be due for recycling in coming years.

Recycling Tanker Ships:

Tankers carry clean petroleum products Gasoline, jet fuel etc. As well as dirty petroleum products such as fuel oil, crude oil etc. By thoroughly understanding Standard Operating Procedures (SOPs) all stakeholders can minimize the risks and multiple hazards it carries to prevent accidents.

• After completion of Cargo discharge operations, tankers perform ballast passage to the ship recycling destinations.

• Tanker’s recycling involves hot work in the form of gas cutting of hull structure.

• Before arriving at the recycling yards vessel’s cargo and slop tanks are cleaned and prepared for Gas Free for Hot Work (GFHW) standards.

• It is crucial that the vessels are delivered to the shipyards where cargo tanks, slop tanks and pump room are as per GFHW standards, as the yard workers perform hot works including ship steel cutting.

• Improper conditions inside the cargo tanks such as presence of flammable gases and compounds could cause life-threatening injuries and even death.

• Ship owners are responsible for delivering vessels with cargo and slop tanks in GFHW condition to the recycling yards.

Preparation of Cargo and slop tanks as per GFHW involves the following steps:

Cargo tank cleaning:

Tank cleaning operations should be well planned. These operations are ship specific and cleaning procedures are documented in a manual on board for every tanker vessel. It is essential to maintain enough wash water for effective cleaning of cargo tanks.
Tanker ships perform tank cleaning as per Crude Oil Washing (COW) Manual or Procedures & Arrangements Manual (P&A) periodically. However, for preparing vessels as per GFHW, the cargo tanks need to be washed with water.

Washing of cargo tanks:

Hot water washing is done when cargo tanks are in inerted condition that have oxygen content below 8%, this is because presence of oxygen above certain levels readily contributes to combustion, and in some situations cause heavy exothermic reaction i.e., explosion.

Cargo tanks are cleaned by sea water with the help of tank cleaning machines, some of which are installed on the main deck. However, occasionally portable tank cleaning machines are used along with the portable hoses.
Pressurized sea water is sprayed via tank cleaning machine supplied from cargo or designated tank cleaning pumps to deep clean inside areas of the cargo tank. All cargo stains and residues are removed from tank bulk heads and collected at bottom of cargo tanks. Portable tank cleaning machines are used where fixed tank cleaning machines do not cover all areas of tank's internal structures.
Sea water can be used at ambient or heated temperature (by passing sea water through cargo tank cleaning heater). The heating medium is usually steam supplied from the engine room boiler. The sea water temperature is maintained between 60 – 80 degrees Celsius suitable for tank coating. Additionally, heating coils in cargo / slop tanks are used to maintain temperatures.

Subsequently enough Tank cleaning chemicals are added to the sea water to ensure degreasing action. Cargo tanks are further washed with sea water without chemicals to remove chemical residues. If MARPOL (International Convention for the Prevention of Pollution from Ships) permits discharge of wash water, then it is directly pumped overboard.
If MARPOL does not permit pumping of wash water overboard then it is collected in the cargo tanks, transferred to slop tanks using cargo pumps and reused to wash different tanks. After cleaning all cargo tanks, the remaining wash water is collected in the slop tanks and discharged to the approved shore reception facility.
It is important to note that for effective tank washing, the pressure and temperature of wash water need to be monitored regularly. It is paramount to check whether Tank cleaning machines are turning in order, that are designed to cover all areas of the tank.

Post sea water washing, cargo tanks are rinsed with fresh water through tank cleaning system to remove all traces of sea water and cleaning chemicals.

To Summarize effective tank washing requires a careful balance of three factors: water pressure, temperature, and proper degreasing action. Tank cleaning operations must be recorded in Cargo Record Book.
For more information or any clarification, please write to bd@gmsinc.net