International Journal of Marine Engineering Innovation and Research, Vol. 5(3), Sept. 2020. 164-171 (pISSN: 2541-5972, eISSN: 2548-1479) 164 Analysis of the Effect of Sloshing on Damage Stability after the Addition of LNG Tanks Agoes Santoso 1 , Achmad Baidowi 2 , Mardisuin Siahaan 3 (Received: 01 January 2019 / Revised: 05 August 2020 / Accepted: 31 August 2020) Abstract - The Damage Stability, better known as leaky ship stability, is a condition where the vessel has a leak in the ship's compartment so that the stability condition of the ship is disrupted. This study is a study of the effects caused by sloshing on the stability of the ship. The method used to calculate damage stability is the lost buoyancy method. This method assumes a condition where when the vessel has a leak, the vessel buoyancy will decrease. This happens because the empty space in the vessel will be filled with water, so it is no longer the part that contributes to the buoyancy so that the ship will increase and can result in sinkage. According to the calculation of SOLAS (Safety of Life at Sea) Consolidated Edition 2014 Chapter II-1 Part B-1. There are two indexes compared, namely index Required index R = 0.77172, which depends on the length of the lining and Attained subdivision index A = 0.83736. The pi factor shows a maximum of 5 leak zones that can be overcome by the ship to remain stable. By comparing the index value of A> R, it can be seen that this ship has fulfilled the SOLAS requirements. Keywords⎯ damage stability, probabilistic, lost buoyancy, sloshing. I. INTRODUCTION Ship stability performance is influenced by two main factors, that are: 1. The shape of the hull of the ship and, 2. Load distribution on board. The first factor is the constant value of ships that have been completed, while the second factor can change at each loading and unloading condition depending on the type of cargo carried by ship. A kind of change in certain load distribution can occur due to sloshing that occurs in partially filled tanks. Sloshing is a phenomenon of fluid free movement in a partially filled container which gives a free surface effect (FSE). When the tanks on board are half full, rolling and pitching the ship makes the liquid in the tank move towards the movement of the ship. This effect is known as an FSE. Damage stability, better known as leaky ship stability, is a condition in which the ship has a leak in the ship's compartment. The ship's ability to maintain the buoyancy of the ship is reduced so that the stability of the ship becomes disrupted. This condition must be overcome by having a compartment plan that is able to prevent instability or even cause the ship to get a grounding. The method is used to calculate damage stability is the lost buoyancy method. This method assumes a condition where when the vessel has a leak. The vessel buoyancy will decrease. This happens because the empty space in the vessel will be filled with water so that it is no longer the part that contributes to the buoyancy so that the ship will increase and can result in sinkage [1]. In accordance with the calculation of SOLAS (Safety of Life at Sea) Consolidated Edition 2014 Chapter II-1 Part B-1. There are two indexes compared, namely index R Required index, which depends on the length of the sealing and index A Attained subdivision index. The index A value depends on the pi factor, which indicates the possibility that the compartments or some of the related compartments have a leak and the factor that indicates the possibility of the ship surviving in the event of a leak. By comparing index A and index R values, it can be seen whether damage stability and ship insulation have met SOLAS standards. Therefore, this research will analyze the movement of sloshing in the LNG tank, which is related to stability when the condition of the hull of the ship has leaked. With the sloshing analysis, it will be known that it will affect the new intact stability and damage stability condition, whether it meets the requirements of SOLAS Consolidated Edition 2014 Chapter II-1 Part B-1 [5]. II. METHOD A. Characteristics of Ro-Ro Ferry Ro-Ro (Roll On - Roll Off) is a type of passenger ship that can be used to transport passengers as well as vehicles. The ro-ro ship has a ramp door that works open and closes mechanically to load vehicles connected directly to the pier. The ramp on ro-ro ships is usually made on the stern, bow, or side of the ship equipped with system lashing to prevent cargo loads vehicles shifting when sailing in bad weather. As one of the modes of transportation that are widely used to connect regions in Indonesia, ro-ro vessels are an important concern for ship safety given the many ro-ro ship accidents in Indonesia. According to the safety aspects of ro-ro vessels, there are several considerations that make ro-ro ships more likely to experience accidents, including (a). stability problem, (b). low freeboard, (c). door access charge, (d). absence of bulkhead, (e). location of high safety equipment, (f). sensitive to weather conditions, Agoes Santoso is with Departement of Marine Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, 60111, Indonesia. E-mail: agoes@its.ac.id Achmad Baidowi is with Departement of Marine Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, 60111, Indonesia. E- mail: ahmadbai@gmail.com Mardisuin Siahaan is with Departement of Marine Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, 60111, Indonesia. E- mail: mardisuinsiahaan@gmail.com