Stop Leak
ST SEAL
Stern Tube Leakage Control
The ST Seal range is designed for different levels of stern tube oil leakage. Core, Plus, and Max
are selected based on leakage rate, system condition, oil volume, and operating profile.
System Compatibility & Blending
Our Stop Leak treatments are based on high-quality stern tube oil and are designed to blend with most commonly used stern tube lubricants. The product is added to the relevant oil system according to the recommended dosage and application guidance.
Suitable System Types
ST Seal can be considered for selected aft seal, forward seal, and stern tube applications, including common lip seal, face seal / Cedervall-type, and air seal arrangements.
The correct ST Seal variant — Core, Plus, or Max — is recommended based on leakage rate, oil volume, system condition, seal arrangement, and operating profile.
Assessment Before Application
Before treatment, we review the seal type, leakage rate, oil type, viscosity, oil volume, filtration, system configuration, and operating conditions. This allows us to recommend the most suitable product, dosage, and onboard application approach for the specific case.
ST Seal Product Range
Leakage rates are indicative only. The final recommendation is based on a technical review of the system, seal arrangement, lubricant, oil volume, filtration, and operating conditions.
Application Example
Developed for real operating conditions across a wide range of vessel types and sealing systems.
Low-Level Leakage - Fishing Vessel
Vessel type: Fishing vessel
Stern tube volume: ~600 L
Estimated leakage: ~5 L/day
Scenario
During regular fishing operations, the crew observed a consistent low-level oil leakage from the stern tube. The vessel returned frequently to its home port, allowing the crew to monitor the situation over time. While not critical, the leakage showed signs of gradually increasing, raising concern about long-term seal condition.
Action
The operator contacted Addvation to assess the situation. Based on system size and observed leakage, ST Seal Core was recommended as a starting point.
Recommended starting point: ST Seal Core
Indicative quantity: ~40 L total
Application
The product was applied by the crew during routine port stay, following standard application procedures.
Outcome
Leakage was reduced and stabilized, allowing continued operation without further escalation or need for immediate maintenance.
Moderate Leakage - Offshore Vessel
Vessel type: Offshore support vessel
Stern tube volume: ~1,200 L
Estimated leakage: ~15–20 L/day
Scenario
During offshore operations, the vessel experienced increasing stern tube leakage under varying load conditions. The leakage was not constant, but intensified during higher load periods, indicating progressing seal wear.
Action
The operator contacted Addvation to assess the situation ahead of the vessel's next scheduled port call. Based on system size and leakage behavior, a reinforced sealing approach was recommended.
Recommended starting point: ST Seal Plus
Indicative quantity: ~ 70 L total
Application
The product was delivered to the vessel's next port and applied by the crew during port stay, following standard application procedures.
Outcome
Leakage levels were reduced and stabilized across operating conditions, improving system reliability and reducing operational uncertainty.
High Leakage - Container Vessel
Vessel type: Container vessel
Stern tube volume: ~4,500 L
Estimated leakage: ~60–80 L/day
Scenario
During transit, the vessel experienced a significant increase in stern tube leakage, indicating deteriorating seal performance. The leakage level created immediate operational concern, including increased oil consumption and pressure to avoid unplanned dry-docking.
Action
The operator contacted Addvation to assess the situation before the next scheduled port call. Based on system size and leakage severity, a maximum sealing support approach was recommended, with delivery coordinated to the vessel's next port.
Recommended starting point: ST Seal Max
Indicative quantity: ~230 L total
Application
The product was applied by the crew during port stay, following standard application procedures.
Outcome
The issue was resolved to a stable operating level, allowing the vessel to continue as planned - and avoid immediate disruption before planned doc.
Developed for real operating conditions across a wide range of vessel types and sealing systems.
Request ST Seal
Send us your vessel details, and we'll help assess dosage, application, and compatibility.