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Home › Dry Dock › Tail Shaft Survey
Operational guide · Certification & surveys

Tail Shaft Survey

Propeller-shaft survey method, interval, withdrawal and any extension follow UR Z21 as incorporated in class Rules; condition monitoring creates no autonomous CMS tail-shaft regime.

tail shafttail shaftstern tubeCMS

Operational Explanation

Propeller-shaft survey method, interval, withdrawal and any extension follow UR Z21 as incorporated in class Rules; condition monitoring creates no autonomous CMS tail-shaft regime.

Regulatory Reference

IACS UR Z21 and applicable Classification Society Rules.

UR Z21 distinguishes closed oil- or fresh-water-lubricated systems from open water-lubricated systems. Also identify the propeller coupling, seals and shaft protection: do not transfer methods or monitoring data from a different arrangement. IACS UR Z21.

For example, Method 3 for closed systems requires relevant records and samples together with checks of bearing wear, accessible parts, propeller and seals, and verification of no reported grinding or welding repairs to the shaft/propeller. Check method eligibility in the Rules: a satisfactory oil analysis meets only part of the conditions. IACS UR Z21, 2.1.3.

Scope of Application

Shaft type, lubrication/sealing arrangement, monitoring, results and Rules determine method/interval; Machinery Continuous Survey is distinct.

Procedure / How to Complete It

  1. Identify shaft arrangement and Z21 method.
  2. Check due date and withdrawal requirements.
  3. Collect oil analysis, bearing temperature and seal records where required.
  4. Use monitoring for modified method/extension only if Rules allow.
  5. Obtain surveyor acceptance before omitting withdrawal.

Practical Example

Quarterly oil analysis may be required evidence, but alone does not replace the due propeller-shaft survey.

What Typically Goes Wrong

Presenting Continuous Machinery Survey/CMS as an autonomous choice to avoid shaft withdrawal or using one five-year cycle.

Common Mistakes Mistake Library

MistakeConsequenceHow to Avoid It
Presenting Continuous Machinery Survey/CMS as an autonomous choice to avoid shaft withdrawal or using one five-year cycle.Non-compliant decision or treatmentFollow the approved arrangement and applicable sources

What the PSCO Checks

Check survey status and formally granted extensions, known leaks or abnormalities and defect management. Compare monitoring reports with the class-accepted method; do not equate a stable trend with survey completion.

Operational Tips

Preparation checklist

FAQ

Does CMS replace shaft survey?
No.
Does monitoring avoid withdrawal?
Only if the method, arrangement, records and results satisfy all applicable Rule conditions and class accepts the survey. Monitoring alone does not authorise omitting withdrawal or extending the due date.

Related Topics

Bottom Survey and In-Water SurveyRudder and Sea Chests

Last substantive revision of this page: 15 September 2026 · page fingerprint 4806fdcb0150