Although the importance of proper alignment of the propulsion shafting has been a well-publicized recent year, discussions among M-16 Panel members involved in all phases of shipbuilding and repair indicated that there still appeared to be some lack of knowledge surrounding the subject within the industry. In general, it was felt by the panel members that most designers of new ships were aware of the various alignment criteria for shafting systems and were designing new ships with shafting systems that met the criteria. However, it was noted that often in repair work, particularly in older ships the shafting systems were poorly designed and usually no data exists on the desired alignment. In addition, frequently the personnel performing the work are not aware of the importance of proper alignment.
For example, if no other information is available, a repair facility may realign a shaft system with all bearing on a straight line, whereas the original alignment called for some bearing to be offset to improve the load distribution and contact in the bearings or perhaps provide proper alignment with a reduction gear. In such a case, the straight-line alignment could result in wiped bearings, excessive gear wear, or perhaps a vibration problem.
The panel decided to conduct an alignment survey of American Shipyards. The questionnaire covers (1) the criteria used in evaluating shipboard alignment, (2)acceptable tolerances on alignment, and (3)methods used for measuring alignment.
The intent of this report is to make the results available to the industry in an effort that can be reasonably expected of a shipyard by a shipowner when an alignment check in necessary in a ship.