NISALAH

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NTSB report into collision published

The National Transportation Safety Board (NTSB) has released an investigation report on the collision between the tug 'Mark E Kuebler' and the 'Nisalah' on Jan 22, 2023, at 3.30 p.m. LT, while the tanker was transiting inbound in the Corpus Christi Ship Channel near Ingleside, Texas. The tug’s hull was breached and the tanker’s propeller was damaged in the collision. The captain of the 'Mark E Kuebler' grounded the ship to prevent it from sinking, and, while aground, a small sheen of hydraulic oil was observed. The oil was recovered with absorbent pads. No injuries were reported. The damage to the 'Mark E Kuebler' was estimated at $3 million; the damage to the 'Nisalah' was estimated at $3.9 million. The 'Mark E Kuebler' was one of five tugs assigned to assist the inbound tanker in transiting through the Corpus Christi Ship Channel to a terminal in Ingleside. After meeting the 'Nisalah' in the Corpus Christi Ship Channel, the 'Mark E Kuebler' transited off the tanker’s starboard quarter for a brief period. The mate on the tug then executed a clockwise 180° spin maneuver in preparation for making up to the tanker. During the maneuver, the tig fell back toward the stern of the 'Nisalah', and, in response, the mate increased the speed of the tugboat to regain a position off the tanker’s starboard quarter. However, as the tug, now transiting in the astern direction, moved forward about 50–60 feet off the 'Nisalah', its stern was drawn in toward the tanker. The mate attempted to counteract this motion by increasing engine power and turning the Z-drives to steer the stern away from the tanker; however, the thrust was not able to overcome the hydrodynamic forces pulling the vessel into the tanker. Consequently, the 'Mark E Kuebler' collided with the 'Nisalah'. As the 'Mark E Kuebler' moved to get into position alongside the 'Nisalah' after executing the 180° spin, the tugboat (moving in the astern direction) approached the area of low pressure on the tanker’s starboard quarter. Because the 'Nisalah' was in ballast, the inward curve of the ship’s hull toward the stern at the waterline was more pronounced than it would have been if the ship was loaded. Thus, the pressure near the VLCC’s starboard quarter was further reduced as compared to the vessel at its loaded draft. In addition, the drop in pressure was further accentuated near the propeller. The hydrodynamic suction produced by the low pressure in this area caused the 'Mark E Kuebler'’s stern to be drawn into the tanker. As the tug attempted to regain position on the Nisalah, the VLCC’s speed was 9.6 knots. Hydrodynamic forces created by a ship increase exponentially with speed, and therefore an increase of even a few knots has a significant effect on the forces acting on a tugboat operating nearby. Moreover, as the 'Mark E Kuebler' attempted to move into position, the tugboat’s speed increased to 11.6 knots—just 1.4 knots less than its maximum-rated ahead speed. Higher speed reduces the amount of reserve propulsion power available to the operator. Because most of the tug's engines’ power was being used to regain position on the 'Nisalah', the 'Mark E Kuebler' had insufficient power to counteract the hydrodynamic forces created by the tanker. After the collision, the tugboat’s operating company instituted a policy limiting stern-first landings of tugboats on assisted vessels to speeds of 7 knots or less. The National Transportation Safety Board determineed that the probable cause of the collision between the ships was the mate maneuvering the tugboat near the starboard quarter of the tanker, which resulted in the tugboat being drawn in toward the tanker by hydrodynamic forces that the tug had insufficient reserve power to counteract due to the transit speed of the vessels. Report with photos: https://www.workboat.com/coastal-inland-waterways/ntsb-tugboat-was-pulled-into-tanker-s-prop-during-texas-collision

Tug grounded following collision with tanker

The US Coast Guard responded to the grounding of the 'Mark E. Kuebler' (IMO: 9866110) near the South Texas Gateway refinery in Corpus Christi on Jan 23, 2023. Coast Guard Sector Corpus Christi command center watchstanders received a call on Jan 22 at 4 p.m. from the agent of G&H Towing stating that the 'Mark E. Kuebler' had ran aground outside the channel near the South Texas Gateway refinery and was taking on water. Watchstanders issued a safety marine information broadcast and directed the launch of a Coast Guard Station Port Aransas 45-foot Response Boat–Medium crew to assist with de-watering. Once on scene, the RB–M crew began assisting with de-watering efforts. Before running aground there was a collision between the tug and the tanker 'Nisalah'. Responders did not observe any signs of pollution and there were no reported injuries. The Coast Guard currently has pollution responders on scene monitoring salvage operations. Report with photo: https://coastguardnews.com/coast-guard-responds-to-aground-tug-near-corpus-christi/