• Title, Summary, Keyword: 선미관

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A Study on the Forced Fitting Method of Stern Tube Bearing for Propulsion Shafting in Ships (선박 추진축계 선미관 베어링의 강제 압입 피팅 방식에 관한 연구)

  • Cho, Kwon-Hae;Lee, Jae-Hyun;Kim, Yang-Gon
    • Journal of Advanced Marine Engineering and Technology
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    • v.34 no.5
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    • pp.653-660
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    • 2010
  • The stern tube bearing is installed to the stern tube and stern boss casting by using the method of the force pressured fitting. The adequate value of the interference between the stern tube bearing and casting should be considered owing to the slip. In this study, to review and compare the fitting force and the contact pressure, the theory of thick walled cylinder is considered to clarify the formula which received from the maker. Also the fitting force and contact pressure are calculated by using the standard value of interference, Young's modulus, Poisson's ratio and friction coefficient.

The Effect of Transient Eccentric Propeller Forces on Shaft Behavior Measured Using the Strain Gauge Method During Starboard Turning of a 4,700 DWT Ship (스트레인 게이지법을 이용한 4,700 DWT 선박의 우현 전타시 프로펠러 편심추력이 축 거동에 미치는 영향 연구)

  • Lee, Jae-ung;Kim, Hong-Ryeol;Rim, Geung-Su
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.4
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    • pp.482-488
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    • 2018
  • Generally, after stern tube bearing shows a significant increase in local load due to propeller load, which increases the potential adverse effects of bearing failure. To prevent this, research on regarding shaft alignment has been carried out with a focus on reducing the relative slope between the shaft and support bearing(s) under quasi-static conditions. However, for a more detailed evaluation of a shafting system, it is necessary to consider dynamic conditions. In this context, the results revealed that eccentric propeller force under transient conditions such as a rapid rudder turn at NCR, lead to fluid-induced instability and imbalanced vibration in the stern tube. In addition, compared with NCR condition, it has been confirmed that eccentric propeller forces given a rapid rudder starboard turn can lift a shaft from the stern tube bearing in the stern tube, contributes to load relief for the stern tube bearing.

Quasi-Static Equilibrium of a Propeller Shaft in a Hydrodynamic Oil-Lubricated Stern Tube Bearing (윤활유(潤滑油) 선미관(船尾管) 베어링 축계(軸系)의 준정적(準靜的) 평형상태(平衡狀態)에 관한 연구(硏究))

  • S.Y.,Ahn;S.S.,Kim
    • Bulletin of the Society of Naval Architects of Korea
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    • v.26 no.3
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    • pp.51-61
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    • 1989
  • Recently, the growth in the propulsion power and propeller size of typical energy saving ships has resulted in severe damages of the oil-lubricated stern tube bearing. Consequently, a more rational analytical method for the design of the shafting system is required. In this paper an analytical method applicable to the design of the oil-lubricated stern tube bearing and shafting system is presented. The method consists of the finite element analysis of the shafting system and the oil film hydrodynamics. The shafting system is modeled as a three-dimensional problem using beam elements taking account for the steady components of thrust, lateral forces and moments of the propeller as well as the elastic foundation effects. The oil film hydrodynamics is modeled as a two-dimensional problem. Equal and retangular elements employing hourglass control method are used for the construction of the oil film fluidity matrix. To search the quasi-static equilibrium position between the propeller shaft and the oil film, an optimization technique is employed. Some numerical results based on the proposed method are compared with some measured and numerical data available. They show acceptable agreements with the data.

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A Study on Flexibility Acquisition Method for VLCC Shaft System (VLCC 축계 시스템의 유연성 확보 방안에 관한 연구)

  • Shin, Sang-Hoon;Ko, Dae-Eun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.12
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    • pp.135-139
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    • 2017
  • The main reason for heat accidents occurring at the after stern tube bearing (STB) is excessive local pressure caused by the deflection of the propulsion shaft due to propeller loads. The probability of a heat accident is increased by the low flexibility of the shaft system in very large crude oil carriers (VLCCs) as the engine power and shaft diameter increase and the distance decreases between the forward and after STBs. This study proposed shaft system with only an after STB and no forward STB for a flexibility acquisition method for a VLCC shaft system under hull deformation. A Hertzian contact condition was applied, which assumes a half-elliptical pressure distribution along the contact width for the calculation of the local squeeze pressure. The propeller loads, heat effect, and hull deflection under engine operating conditions are also considered. The results show that the required design criteria were satisfied by building a partial slope at the white metal, which is the material at the axial contact side in the after STB. This system could reduce building cost by simplification of the shaft system.

A Study on Optimum Shaft Alignment Analysis for VLCC (VLCC의 최적 축계정렬해석 연구)

  • Kim Hyu Chang;Kim Jun Gi
    • Special Issue of the Society of Naval Architects of Korea
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    • pp.134-137
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    • 2005
  • Recently, in VLCC, shafting system is stiffer due to large engine power whereas hull structure is more flexible due to scantling optimization, which can be suffered from alignment damage by incompatibility between shafting and hull, In this study, shafting system without stern tube forward bush was adapted for less sensitive system against external factors. Also, shaft alignment analysis was considered with hull deflection at various ship loading conditions and stern tube after bush of long journal bearing was evaluated by static squeezing pressure and dynamic oil film pressure with sloping control. Whirling vibration was also reviewed to avoid resonance with propeller blade order. So, reliable shafting design for VLCC could be achieved through optimized alignment analysis for the system without stern tube forward bush.

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Effects of propeller eccentric forces on propulsion shafting system under hard port turning conditions (선박 좌현 전타 조건에서 프로펠러 편심추력이 추진축계에 미치는 영향 연구)

  • Kim, Bu-Gi;Lee, Jae-Ung;Kim, Jung-Ryul
    • Journal of Advanced Marine Engineering and Technology
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    • pp.682-689
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    • 2018
  • Normally, a ship's propeller weight significantly increases the support load of bearings in the ship's shafting system, which increases the potential risk of bearing failure. To prevent this, a series of studies on shaft alignment are conducted with a focus on reducing the relative inclination angle between the propeller shaft and after stern tube bearing under quasi-static conditions. However, to achieve a more complete stability evaluation of the shafting system, the dynamic state of the shaft alignment must be considered. Our results revealed that propeller eccentric forces, which fluctuate in a hard port turning, demonstrated fluid-induced instability and contributed to stall phenomena in the stern tube. In addition, depending on the specific ship being considered, the opposite results from those in previous studies could be derived. Therefore, the imbalanced vibration characteristics that originate from the propeller eccentric forces in the transient condition must also be considered.

A Study on Designing an Effective Support Point for After-Stern Tube Bearings Concerning Shaft Alignment (추진축계 정렬시 선미관 베어링 유효지지점 설정에 관한 연구)

  • Lee, Jae-ung;Kim, Yeonwon;Kim, Jung-Ryul
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.6
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    • pp.803-809
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    • 2018
  • Generally, the gap-and-sag method is used in the shipbuilding stage before coupling the shafts to check whether they are installed at the same position as designed and derived from shaft alignment calculation. The primary installed propeller shaft becomes a reference point, the position of the remaining shafts are sequentially determined through the gap-and-sag value derived from the deflection and deflection angle at each shaft flange by own weight. If the reference point varies against the design value, it would have a series of effects on the installation of the remaining shafts. Moreover, after coupling the shafts, even if the bearing reaction forces derived from measurement are satisfied by the allowable limit range, consequently it might have an adverse effect on the stability of the shafting system by not being able to estimate the relative slope angle between the propeller shaft and the after-stern tube bearing. In this paper, to deal with above-mentioned phenomenon, the theoretical calculations related to designing an effective support point of the aft stern tube bearing and analysis by measurement is conducted through a case of open-up inspections. Based on this, a shaft installation guideline is proposed to minimize the misalignment related to preventing wiping damage of the after-stern tube bearing.

A Feasibility Study on the Application of Stern Tube Unit for the Twin Skeg LNG Carrier (쌍축 LNG 운반선에 대한 선미관 유닛 적용 가능성 연구)

  • Shin, Sang-Hoon;Sung, Young-Jae;Park, Jeong-Yong;Han, Bum-Woo
    • Journal of the Society of Naval Architects of Korea
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    • v.53 no.4
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    • pp.282-289
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    • 2016
  • Traditional construction method of the stern tube is difficult to control the process and needs excessive working hours. Recently in order to resolve these issues, stern tube unit has been installed for some commercial vessels. The stern tube unit is a monolithic structure of bush and related components. The purpose of this study is to carry out a feasibility study for application of the stern tube unit for a 174K twin skeg LNG carrier. In this study, a 19,000 TEU container carrier installing the stern tube unit has been selected to compare with the deformations of stern for a 174K twin skeg LNG carrier.

Effect of Transient Condition on Propeller Shaft Movement during Starboard Turning under Ballast Draught Condition for the 50,000 DWT Oil Tanker (50,000 DWT 유조선의 밸러스트 흘수에서 우현 전타시 과도상태가 프로펠러축 거동에 미치는 영향 연구)

  • Lee, Jae-ung
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.26 no.4
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    • pp.412-418
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    • 2020
  • Generally, the propeller shaft that constitutes the ship shaft system has different patterns of behavior due to the ef ects of engine power, propeller load and eccentric thrust, which increases the risk of bearing failure by causing local load variations. To prevent this, different studies of the propulsion shaft system have been conducted focused the relative inclination angle and oil film retention between the shaft and the support bearing, mainly with respect to the Rules for the Classification of Steel Ships. However, in order to secure the stability of the propulsion shaft via a more detailed evaluation, it is necessary to consider dynamic conditions, including the transient state due to sudden change in the stern wakefield. In this context, a 50,000 DWT vessel was analyzed using the strain gauge method, and the effects of propeller shaft movement were analyzed on the starboard rudder turn which is a typical transient state during normal continuous rate(NCR) operation in ballast draught condition. Analysis results confirm that the changed propeller eccentric thrust acts as a force that temporarily pushes down the shaft to increase the local load of the stern tube bearing and negatively affects the stability of the shaft system.