Survey of Tail-shafts (Superseded by Engr. Circular No. 01 of 2016)

1. Survey Intervals Based on Propulsion System Type

Maximum intervals for tail-shaft surveys based on propulsion system type are specified in the following table:

2. Survey Intervals Based on Survey Process

Classification Societies have implemented extended intervals for tail-shaft surveys under varying nomenclatures. The following survey processes are described for uniformity:

• Normal Surveys: Complete withdrawal and thorough examination of tail-shafts every 5 years (or as per table above).
• Modified Survey: Partial withdrawal of the shaft to examine stern bearing and shaft. Interval between two consecutive full withdrawals can extend up to 10 years (or 5 years for other propulsion systems).
• Partial Surveys: Back off propeller in keyed shafts and examine top half of the cone. Interval between two consecutive full withdrawals can extend up to 7.5 years (or as per table above).
• Tail-shaft Condition Monitoring (TCM) Program: Intervals between two consecutive withdrawals of tail-shaft may be extended to a maximum period of 10 years, provided the vessel complies with IACS Unified Requirements Z21 and is maintained to the satisfaction of the Recognised Organization.

3. Extension of Tail-shaft Surveys

Tail-shaft surveys may be postponed for a maximum period of one year (or till the next scheduled dry-dock surveys, whichever is earlier) for propulsion systems under Sr. no. 1 to 5 of table 1, and six months for systems under Sr. no. 6. This extension is permitted only for vessels less than 15 years of age and companies meeting the conditions of the "green channel" category.