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Stern tube seal and system inspection for cruise ship


Type of project: Inspection and report

Customer Name: UK cruise operator

Location: Southampton Port, UK

Initial Enquiry: 

Our engineers were required to carry out a stern tube inspection on a cruise ship whilst in dock at Southampton on behalf of our sister company AtZ. The vessel had reported leakage from one of their two Wartsila MD stern tube shaft seals of 16 litres per day or more but was unsure if there was likely failure that would require stopping the shaft or whether the issue could be resolved in service.
The vessel was due to dock within three months, and the customer wanted a complete and independent evaluation of the condition of both seals so that they could have the required parts available and resolve any issues during repairs.
ATZ and MIT have a great deal of propulsion, seal and bearing experience, including the design and development of this seal. As such, we were able to offer a thorough and informed assessment of the seal condition to support the customer’s dock plans and support their recommended remedial actions.

Project Objectives:

Provide independent and expert assessment of the equipment condition within a short time frame from our Southampton base. Make recommendations as to interim measures to be taken on board, and identify parts required for forthcoming refit.

Complete the inspection and report within a single weekend day call-in port.

Overcome any unforeseen on-site issues to the highest standards without delay to the ship’s departure date.

Project Description: 

stern tube service

The vessel had reported an inboard seawater leak from the Starboard shaft. Reported starboard leakage is approximately 16 litres per day. Our engineers were asked to attend in order to:

  • Assess the seal condition
  • Recommend any containment actions
  • Advise what future maintenance is required.

The system was found to be in satisfactory condition, with air and water supplies correctly configured.

Corrosion of the seal housings, spring assembly and seat were noted. Wear of the rotating seal interfaces was also significant. Evidence of leakage from the port seal was also found.

Monitoring and containment actions were recommended as follows:

Monitor leakage daily to identify any significant changes which may require more urgent intervention. The performance of the port seal was also to be observed.

Regular checks of the inflatable seals to ensure they remained operational in case of emergency.

Inflatable seal operation to be checked and logged monthly by activating the seals when the shaft is stationary. This prevents any excess marine growth build-up and checks their condition.

Stern tube replacement


Observed leakage of the starboard and port seal was confirmed, with the most likely source considered to be the worn interface.

The overall condition of the starboard seal required refurbishment in the near future. A major overhaul of the seal assembly to include new interfaces, rubber items, bellows, and inflatable, as well as re-establishing the seat surface and other corroded surfaces, was recommended as a minimum.

The port seal was found to be in a similar condition, and our recommendations, therefore, apply to both seal installations.

We provided the customer with a thorough and technically detailed independent assessment of their seal condition and recommendations for the management and repair of observed leakage.

Stern tube overhaul


Contact our team today to discuss how we can help onboard your vessel.


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