Home » Case Studies » Rapid Emergency Repair of Niigata ZP 41 Following Severe Water Ingress Onboard Offshore Tugboat
Table of Contents
Case Study
Rapid Emergency Repair of Niigata ZP 41 Following Severe Water Ingress Onboard Offshore Tugboat
Table of Contents
Background
Industry
Marine
Solution
Emergency Repair and Seal Overhaul
Make & Model
Niigata Z-PELLER®
Propulsion System
Asset
Offshore Tugboat
Objective
To identify and eliminate the cause of water ingress in the starboard ZP unit and
Repair the Niigata Propulsion System
to operational condition with minimal downtime using onboard spares and expert technical intervention.
Challenge / Problem Context
1. Water ingress detected in the starboard ZP unit: Sudden water ingress was observed, threatening propulsion reliability and vessel safety.
2. Presence of fishing net entanglement around the Z-PELLER®: Debris entanglement was suspected to have compromised the stern tube liner and seal integrity.
3. Scoring marks on the stern tube liner: Damaged liner surface led to oil-water cross-contamination, requiring urgent component renewal.
4. Complex component disassembly required within tight timelines: Repair work involved full propeller dismantling, liner and seal replacement, and sea trials—normally requiring 4 days.
What Did We Do?
1. Inspected and confirmed water ingress cause through oil draining and physical examination: Found scoring on the stern tube liner and a fishing net entangled in the ZP area, leading to seal leakage.
2. Dismantled starboard propeller as per OEM guidelines and removed damaged components: Removed propeller cap, lock nut, liner, and both seal housings to access the damaged parts.
3. Replaced stern tube liner, propeller shaft seals, and steering rotary seals with new components: Cleaned seating areas, fitted new O-rings and seals, and torqued all critical fasteners to 2050 NM.
4. Mounted back propeller, kort nozzle, and conducted precision assembly with OEM clearances: Ensured proper push-up travel measurement (6.0 ± 0.1 mm) and filled the unit with 2600 liters of VG 100 oil.
5. Performed air pressure testing and steering motion checks: Carried out 0.5 bar pressure test for one hour—confirmed no leaks. Checked port-starboard steering performance.
6. Completed sea trials post-repair and carried out cementing of propeller cap: Verified all systems operational, ensuring mechanical integrity under load conditions.
Results That We Achieved
1. Resolved water ingress and restored propulsion system integrity: Prevented further oil contamination and avoided long-term ZP unit damage.
2. Eliminated root cause—fishing net entanglement and scored liner—through expert diagnosis: Reduced risk of repeat failure through proper mechanical corrections and component renewals.
3. Executed complex overhaul procedures 25% faster than standard timeline: Completed job—including sea trial—in just 3 days instead of the typical 4, minimizing vessel downtime.
4. Validated operational safety and system performance through rigorous testing: Pressure tests and motion checks confirmed complete leak elimination and steering responsiveness.
