Demystifying Ship Recycling - Issue 09
Removal of Propeller and Draining of Stern Tube Oil at HKC Compliant Recycling facilities.
All vessels have been fitted with propellers after the era of ships equipped with sails was over. Many ships are sometimes fitted with more than one propeller as per the ships' size, propulsion power, and maneuvering requirements. These propellers are driven by diesel engines, steam turbines, gas turbines, or electric motors as per the technical aspects of the ships. The propellers and prime movers are connected by a shafting system. As we all know, the propeller is fitted outside the ship's hull, and the propeller shaft penetrates the hull. The penetration is called Stern Tube, which has multiple functions. It provides support to the propeller shaft. Modern stern tubes are oil lubricated. Stern tubes are fitted with the aft & forward seals to contain the lubrication oil within the stern tube system and avoid the seepage to the sea and the engine room.
Different domestic and international regulations require the stern tube to be biodegradable. Therefore, in the case of accidental seepage or operational seepage, it does not adversely affect the marine environment. Nowadays, almost all shipowners use biodegradable oils for stern tube lubrication.
HKC compliant recycling facilities at Alang have developed the Standard Operating Procedures (SOPs) to drain and collect the stern tube lubrication oil. Although the oils are biodegradable, they are not allowed to mix with the seawater. The oil is drained inside the engine room to the maximum possible extent, collected, and handed over to the authorized oil collection vendors. When a vessel is delivered to the recycling facility, she is trimmed to the stern, which means the aft draft is higher than the forward draft. Therefore, some oil remains in the stern tube, which needs to be drained outside the vessel's hull near the propeller shaft. Recycling yards prepare a makeshift collection arrangement to drain the oil and not allow it to spill on the sand. Utmost precautions are taken in performing this task. Oil spill kits are kept on standby. Pontoons and empty drums are used as a part of the containment system. The workers use adequate PPE while performing oil draining and collection tasks. The yard safety officer supervises the entire operation.
The propeller is dismantled and shifted to the impermeable floor for further recycling.
The SOPs developed by HKC compliant yards prevent oil contamination with the seawater and ensures vessels are recycled sustainably.