Strain Gauge를 이용한 선박 추진 축계 베어링 반력의 측정 및 분석에 관한 연구

Abstract

Modern ship hulls of large oil carriers and container carriers have become more flexible with scantling optimization and increase in ship length. On the other hand, as the demand for power has increased with the ship size, shaft diameters have become larger and stiffer. Consequently, the alignment of the propulsion system has become more sensitive to hull girder deflections, resulting in difficulties in analyzing the alignment and conducting the alignment procedure. Accordingly, the frequency of shaft alignment related bearing damages has increased significantly in recent years. Specially, after stern tube bearing damage and failure for large oil carriers have been reported several times. However, the bearing reaction of the after stern tube bearing cannot be measured by jack-up method due to the hull structure condition. Therefore, when the jack-up method is used for the bearing reaction measurements, the bearing reaction for the after stern tube bearing obtained from the theoretical calculation method have to be used.

In this paper, the shaft alignment on the large oil carrier is theoretically calculated and the differences between the calculated and actual installed bearing reaction values are compared. The bearing reactions for forward stern tube bearing and intermediate bearing are calculated by the simple formula using the strain gauge bending moments obtained from the measurements. Their reliability is confirmed by comparing the bearing reactions from jack-up method and the bearing reaction for after stern tube bearing is calculated by the same method. Also, the bearing reactions on the after stern tube bearing, forward stern tube bearing and intermediate shaft bearing under all operating conditions are calculated by using the bending moments obtained from the measurements and it is confirmed that the differences of the bearing reaction for all operating conditions are caused from hull deflection. The results of this study should prove useful for the future projects of the alignment calculation including the hull deflection effectiveness