Stern tube leaking… but only when the vessel goes astern.
No leak ahead.
No alarms.
Only water ingress during astern operation.
This was the issue reported by the crew of one of the vessels we recently supported.
Instead of immediately replacing the seal, we performed vibration and shaft displacement measurements during berthing operations.
The results showed that the problem was not the seal itself.
During astern operation, shaft centre movement near the stern tube was up to 3× higher than during ahead operation.
This additional shaft deflection affected the stern tube seal performance, allowing water ingress.
Our recommendation:
Recalculate the stern tube seal design and positioning to compensate for shaft movement during astern operation.
This is a good reminder: many stern tube leaks are treated as a seal problem, while the real root cause is shaft alignment and dynamics.
If you’re dealing with recurring stern tube leaks or unexplained vibration issues, let’s talk.
We support ship managers and superintendents with advanced onboard vibration diagnostics and shaft analysis.