TRÌNH bày nội DUNG TRONG MẢNG KIẾN THỨC THUỶ TĨNH (HYDROSTATIC) ỨNG DỤNG THỰC TIỄN CÔNG VIỆC

TẬP ĐỒN DẦU KHÍ VIỆT NAM TRƯỜNG ĐẠI HỌC DẦU KHÍ VIỆT NAM oOo TIỂU LUẬN MƠN THỦY ĐỘNG LỰC CƠNG TRÌNH NGỒI KHƠI ĐỀ TÀI: TRÌNH BÀY NỘI DUNG TRONG MẢNG KIẾN THỨC THUỶ TĨNH (HYDROSTATIC) ỨNG DỤNG THỰC TIỄN CÔNG VIỆC GVHD: HỌC VIÊN THỰC HIỆN : ThS PGS TS LÊ TẤT HIỂN PHẠM XUÂN TUẤN ANH TP Vũng Tàu, Ngày 12 Tháng 01 Năm 2019 Contents INTRODUCTION STABILITY ANALYSIS 2.1 General 2.2 Wind Condition 2.3 Wind Force Calculation 2.4 Stability Ratio – Intact Stability – Damage Stability 2.5 Cargo items 2.6 Barge items and tow condition INTACT AND DAMAGE STABILITY ASSESSMENTS 3.1 Intact stability assessment 3.2 Damage Stability Assessment RESULTS: 11 4.1 Intact Stability Check 11 4.2 Damage Stability Check 13 INTRODUCTION For installing or repairing offshore Platforms, offshore modules (like Jackets, Topsides, etc.) are transported from fabrication yard to the field of installation These offshore modules are transported through non propelled barges Barge along with the offshore module fastened on the deck is towed by the specified tug For such operations the barge strength and stability calculations are of prime concern Firstly, suitable ballast plan for the barge tanks is decided taking into account the cargo locations on the barge deck The draft and trim are maintained as per MWS guidelines Minimum positive stability range as per MWS guidelines is required to be achieved Motion analysis of this barge is another concern of the transportation Wave induced motions and accelerations at the critical locations like cargo centre of gravity should be known before the actual sail out of the barge These accelerations are required for the further stress analysis at critical locations Conservative design approach is used where the extreme motions are found out This is the case when very high sea state (rough sea) is observed for a specified tow route In such a situation it becomes practically difficult to pull the barge The towing arrangement may be temporarily disconnected Hence in order to get those extreme motions the zero forward speed analysis is done In this essay, we will study the stability analysis for the transportation of CTC1 topside on the transportation barge VIETSOVPETRO 05 The cargo will be transported from the fabrication yard of Vietsovpetro to Ca Tam Oil Field The towing route from the fabrication yard to the site is approximately 120km and the estimated duration of tow is about day STABILITY ANALYSIS 2.1 General A cargo barge integrated system shall have position stability in calm water equilibrium position In addition, the system shall have sufficient dynamic stability (righting ability) to withstand the overturning effect of the force produced by a steady wind from any horizontal direction In order to examine the stability of the system, the following criteria shall be applied 2.2 Wind Condition The stability of cargo barge integrated system shall be evaluated under the following designed wind condition which are specified in DnV Rules (Stability and watertight Integrity – January 2001) and ABS - 1980 Intact Stability : V = 100 knots (51.5 m/sec.) Damage Stability: V = 50 knots (25.8 m/sec.) 2.3 Wind Force Calculation Based on the maximum design wind speed, the wind force acting on the cargo barge system can be computed in terms of the following equation Fw = 0.0623 V2 Ch Cs A (kg) Where: V: wind speed Cs: Shape coefficient Ch: the height co-efficient varied upon the height of the structure on which force acts A: Area of object (m2) 2.4 Stability Ratio In order to examine the dynamic stability of floating structure, the ABS (American Bureau of Shipping) criteria shall be used as a minimum requirement In addition to ABS criteria, the IMO stability check will be carried out – Intact Stability A wind-heeling curve shall be calculated using the method presented in the ABS criteria The Dynamic stability at a certain angle of heel is equal to the area under the curve of righting lever up to that angle, multiplied by the displacement The area under the righting moment curve at before either the second intercept or the down flooding angle, whichever is less, shall not be less than 40% in excess of the area under the wind-heeling moment curve to same limiting angle 2 – Damage Stability The design damage stability condition shall be based on the worst condition where one compartment in the barge is flooded The additional heeling moment induced by the effect of the flooding shall be considered The area under the righting moment curve at or before either the second intercept or the down flooding angle, whichever is less, shall not be less than the area under the wind-heeling moment curve the the same limiting angle 2.5 Cargo items 2.6 Barge items and tow condition INTACT AND DAMAGE STABILITY ASSESSMENTS Barge intact and damage stability during tow are reference from IMO, API and ABS recommendations The Stability curve are deried from statistical stability cases with the effects of wind heeling moment imposed on them 3.1 Intact stability assessment As calculated, the towing condition meets the IMO, API and ABS recommendations on the intact stability in respect of the servise condition The stability standards which are stipulated as minimal are as follows: a) The area under righting lever curve up to the angle of maximum rightinglever, or the angle of downflooding, or 40 degrees, whichever is less, should not be less than 0.08 m-rad (4.58 m-deg) b) The critical metacentric height should not be less than 0.3 metre c) The righting lever should be least 0.20 metre at an angle of heel equal to or greater than 30 degree d) The area under the righting arm should not be less than 3.15 deg-m up to an angle of heel 30 degree e) The area under the righting arm should not be less than 5.15 deg-m up to an angle of heel of 40 degree or the down flooding angle, whichever is less f) The area under the righting arm curve between the angles of heel of 30 degree and 40 degree, or the down flooding angle, should not be less than 1.72 deg-m g) The area under the righting lever curve at or before the second intercept or downflooding angle, or 40 degrees, whichever is less, is not to be less than 40% in excess of the area under the wind heeling arm curve to the same limiting angle 3.2 Damage Stability Assessment As calculated, the towing condition meets the IMO, DNV and ABS recommendations on the damage stability in respect of the service condition The stability standards which are stipulated as minimal are as follows: a) In the case of unsymmetrical flooding, the total heel shall not exceed degrees, except that, in speccial case shall the final heel exceed 15 degrees b) The area under the righting lever curve at or before the second intercept or downflooding angle, or 40 degrees, whichever is less, is not to be than the area under the wind heeling arm curve to the same limiting angle 4 RESULTS: 4.1 Intact Stability Check a) The area at maximum righting lever = 94.00 deg-m > 4.58 deg-m b) Initial metacentric = 25.78 > 0.3 metre c) The righting lever at 30 degree = 6.16 m > 0.20 metre d) The area up to an angle of heel 30 degree = 145.17 deg-m > 3.15 deg-m e) The area up to an angle of heel 40 degree = 201.97 deg-m > 5.15 deg-m f) The area between 30 degree and 40 degree = 56.80 deg-m > 1.72 deg-m g) The area ratio under the righting lever curve at down flooding angle = 8.38 > 1.4 4.2 Damage Stability Check a) Final equilibrium roll angle = 0.99 degree < degree b) The area ratio under the righting lever curve at down flooding angle = 32.32 > 1.4