Demystifying Ship Recycling - Issue 10
Stability of vessel’s hull during recycling at HKC Compliant recycling facilities.
Ships are designed and constructed considering intact stability and damage stability. Vessels during their active sea service remain stable while facing rough seas and different adverse weather conditions. Ship’s stability is achieved during sea life by using seawater for ballast and laden passage. Occasionally in older vessels, sand, mud, or pig iron was used as permanent ballast. Ships usually remain stable unless some operational errors occur in ballasting and deballasting operations or following improper loading and unloading sequences.
When a ship is delivered for recycling to the HKC compliant yards, her hull rests on the ground. The stability criteria for ships are different than in the afloat condition. At first, a ship-specific Ship Recycling Plan (SRP) is prepared. In the SRP, a sequence is incorporated to slice the vessel’s hull basis estimated weights by naval architects. Accordingly, the slices are removed from the port and starboard side of the hull to ensure the center of gravity of the hull remains within the hull, and the ship remains upright all the time. The hull is cut in a Zig-Zag way to ensure that nearly the same weight of steel plate sections are removed from both sides of the vessel’s hull. Cutting hull in this pattern helps to maintain safe access to the vessel’s structures, and effective working height is reduced. It takes roughly 6 to 8 months to cut the complete hull at a normal recycling rate in which the ground conditions change. The hull is pulled towards the recycling yard regularly as recycling progresses. Therefore, the cutting sequence is altered in some instances to ensure stability with prior approval from the SRP committee. Furthermore, the hull is secured with heavy-duty chains to the winches. The slices are lifted with cranes with heavy lifting capacity and kept on the secondary cutting zone without allowing them to fall on the intertidal zone.
HKC compliant recycling facilities have developed SOPs to ensure recycling is done safely and environmentally soundly.