Type of project:  

• Investigate and rectify a pitch imbalance issue on a ferry, specifically focusing on the starboard Ulstein gearbox.

Customer name: UK ferry operator 

Location: Greenock, Scotland

Initial enquiry: 

In the dry docks of Greenock, Scotland, our expert engineers were called upon to address a significant challenge: a pitch imbalance in the Ulstein starboard propeller of the ferry vessel. This issue was causing operational inefficiencies and required immediate attention.

Project Description

Initial Observation:

Our team observed the gearbox in operation while sailing from Ayr to Greenock. No issues were detected during this phase.

Issue Verification:

Upon docking at Dales Greenock, the reported issue was confirmed:

• With the clutch engaged at 0 pitch, the propeller produced an ahead wash.
• Adjusting the pitch control to 15% astern resulted in the wash moving to astern/neutral.
• Returning the pitch control to 0 did not change the wash.
• Disengaging the clutch until the propeller shaft stopped and then re-engaging the clutch resulted in the pitch moving ahead.

Initial Troubleshooting:

• The O/D slide valve was removed and replaced with a new one from the ship’s spares, but the issue persisted.
• Leakage on the slide valve was checked and compared with the port side; both were the same.
• Pitch movements were observed with the engine running via a Perspex plate on the top cover, and all appeared normal.

Manual Control Test:

• Lever arm stoppers and actuator were removed to control pitch manually using a standby pump.
• Maximum pitch was reached to increase servo pressure, testing the servo piston seal by causing pressure to ramp up and activate the safety relief valve.
• Pressures were compared to the port side, and both were the same.

Decision to Overhaul:

Based on the findings, a decision was made to overhaul the gearbox.

Gearbox Overhaul:

• The gearbox was fully dismantled, and all bearings and seals were changed.
• Precise measurements of the output shaft runout were taken before removal and after the overhaul.
• All measurements were forwarded to Kongsberg for approval, and the appropriate work was carried out in accordance with their response.

Testing and Sea Trials:

The gearbox was tested and underwent sea trials to ensure the issue was resolved.

Conclusion:

The investigation and subsequent overhaul of the Ulstein propeller starboard gearbox on the ferry successfully addressed the pitch imbalance issue. The detailed process ensured that all potential causes were examined and the gearbox was restored to optimal functionality.

At MIT, we specialise in solving complex drivetrain issues, ensuring our customers’ vessels operate smoothly and efficiently. Our recent success in Greenock is a testament to our commitment to excellence and customer satisfaction.

Download the full overhaul report here