Introduction

In any propulsion shafting system, the load carried by each bearing is an important factor contributing to the overall succesful operation of the system.

Gap and offset as well as optical methods are used on new constructions to align ship’s main propulsion shafting, and when careful procedures are followed, will provide good alignment, however, they are indirect methods of obtaining bearing reactions and subject to considerable error in some cases.

Method

The HYDRAULIC JACKING METHOD, as developped by H.C. Andersen of MASS., U.S.A. is a direct method of propulsion shaft alignment, wherein the bearing reactions are determined by jacking the shaft out of its bearing, with a calibrated electronic load cell in between.

In repair work, it expedites an alignment check, since it is not necessary to unbolt the intermediate shafts, and quick answers are obtained on what needs to be done to establish a good propulsion shaft alignment, in other words, satisfactory bearing reactions.

When the jacking method is used to obtain bearing reactions existing on a lineshaft system, certain procedures must be followed, characteristics of the shafting system understood and correct interpretations of the hysteresis loop made, so correct results are obtained.

A qualified engineer, assisted by one or two fitters, should carry out this kind of shaft alignment operations.  There is no need for external engineering assistance, such as by computer, all decisions are made on board and remedial actions are taken immediately, so that in a shortest possible timeframe the propulsion shafting finally will have satisfactory bearing reactions and bearings will have optimum orientations for long-life, troublefree operation.

Certification

The above-described method has approval from Regulatory Bodies.