TH Seal

Thruster Stop Leak & Water Ingress Control

The TH Seal is designed to support thruster systems affected by oil leakage, water ingress, or reduced seal performance. Thruster seal Core, Plus, and Max are selected based on leakage level, water contamination, thruster type, oil volume, system condition, seal arrangement, and operating profile.

System Compatibility & Blending
Thruster Seal treatments are based on high-quality thruster lubrication oil and are designed to blend with most commonly used mineral thruster lubricants. The product is added to the relevant thruster oil system according to the recommended dosage and application guidance.

Suitable System Types
Thruster Seal can be considered for selected thruster applications, including tunnel thrusters, azimuth thrusters, and thruster seal / lubrication systems, as well as common lip seal, face seal, and air seal arrangements where applicable.

The correct Thruster Seal variant — Core, Plus, or Max — is recommended based on oil leakage level, water ingress condition, thruster type, oil volume, system condition, seal arrangement, and operating profile.

Assessment Before Application
Before treatment, we review the thruster type, seal arrangement, leakage rate, water contamination level, oil type, viscosity, oil volume, filtration, system configuration, and operating conditions. This allows us to recommend the most suitable Thruster Seal variant, dosage, and onboard application approach for the specific case.

TH 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

Low-Level Oil Leakage - Coastal Passenger Ferry

Thruster Seal Core – Oil Leakage Support for a Coastal Passenger Ferry

Vessel type: Coastal passenger ferry
Thruster type: Tunnel thruster
Thruster oil volume: ~350 L
Estimated leakage: ~0.4 L/hour or 9,6 L/daily

Scenario

During routine ferry operations, the crew observed a consistent low-level oil leakage from the tunnel thruster seal system. The vessel operated on a fixed route with frequent port calls, allowing the crew to monitor the leakage over time. While the leakage was not critical, the operator wanted to reduce oil loss and support stable seal performance before the issue developed further.

Action

The operator contacted Addvation to assess the situation. Based on thruster type, oil volume, leakage level, and operating profile, Thruster Seal Core was recommended as a starting point.

Recommended starting point: Thruster Seal Core
Indicative quantity: ~20–25 L total

Application

The product was applied by the crew during a scheduled port stay, following the recommended dosage and application guidance.

Outcome

The leakage was reduced and stabilized, supporting continued operation without immediate intervention. The system remained under observation toward the next planned service window.

Moderate Oil Leakage - Platform Supply Vessel

Thruster Seal Plus – Leakage Support for a Platform Supply Vessel

Vessel type: Platform supply vessel
Thruster type: Azimuth thruster
Thruster oil volume: ~750 L
Estimated leakage: ~0.8 L/hour or ~19 L/day

Scenario

During offshore support operations, the crew observed recurring oil leakage from the thruster seal system. The leakage was not constant, but increased during manoeuvring, station keeping, and higher load conditions. While the vessel remained operational, the operator wanted to reduce oil loss, stabilize seal performance, and avoid unnecessary disruption before the next planned service window.

Action

The operator contacted Addvation to assess the situation before the vessel's next scheduled port call. Based on thruster type, oil volume, leakage behaviour, seal arrangement, and operating profile, a reinforced sealing support approach was recommended.

Recommended starting point: Thruster Seal Plus
Indicative quantity: ~50-55 L total

Application

The product was delivered to the vessel's next port and applied by the crew during port stay, following the recommended dosage and application guidance.

Outcome

Leakage was reduced and brought under better control across operating conditions. The thruster system remained operational, with improved sealing stability and reduced operational uncertainty until planned maintenance.

High Oil Leakage - Offshore Construction Vessel

Thruster Seal Max – Leakage Support for an Offshore Construction Vessel

Vessel type: Offshore construction vessel
Thruster type: Azimuth thruster
Thruster oil volume: ~1,600 L
Estimated leakage: ~3.0 L/hour or ~72 L/day

Scenario

During offshore construction operations, the vessel experienced a significant increase in leakage from the azimuth thruster seal system. The leakage became more pronounced during dynamic positioning, manoeuvring, and higher load conditions, indicating deteriorating seal performance. The leakage level created operational concern due to increased oil consumption and the need to avoid unplanned intervention before the next scheduled maintenance window.

Action

The operator contacted Addvation to assess the situation ahead of the vessel's next port call. Based on thruster type, oil volume, leakage severity, seal arrangement, and operating profile, a maximum sealing support approach was recommended.

Recommended starting point: Thruster Seal Max
Indicative quantity: ~150 L total

Application

The product was delivered to the vessel's next port and applied by the crew during port stay, following the recommended dosage and application guidance.

Outcome

Leakage was reduced and brought under better control, allowing the thruster system to remain operational. The vessel continued its planned operation with improved sealing stability until the next scheduled maintenance opportunity.

Early-stage Water Ingress - Small Ro-Ro Ferry

Water Ingress – Thruster Seal Core for a Small Ro-Ro Ferry

Vessel type: Small Ro-Ro ferry
Thruster type: Tunnel thruster
Thruster oil volume: ~300 L
Observed issue: Early-stage water contamination in the thruster oil

Scenario

During routine thruster oil checks, the crew observed increased cloudiness in the lubrication oil, indicating early signs of water ingress. The vessel operated on a short fixed route with frequent port calls, repeated manoeuvring cycles, and regular thruster use during docking. The system remained operational, but the operator wanted to limit further water contamination and support stable seal performance until the next planned service window.

Action

The operator contacted Addvation to assess the situation. Based on thruster type, oil volume, oil condition, seal arrangement, and operating profile, Thruster Seal Core was recommended as a starting point.

Recommended starting point: Thruster Seal Core
Indicative quantity: ~ 20 L total

Application

The product was applied during a scheduled port stay, following the recommended dosage, application guidance, and onboard monitoring procedures.

Outcome

Water ingress was reduced and brought under better control. The oil condition stabilized, allowing the thruster system to remain operational while it was monitored toward planned maintenance.

Moderate water Ingress - Wind Farm Service Vessel

Water Ingress – Thruster Seal Plus for a Wind Farm Service Vessel

Vessel type: Wind farm service vessel
Thruster type: Azimuth thruster
Thruster oil volume: ~650 L
Observed issue: Ongoing water contamination and reduced oil clarity in the thruster oil
Estimated water ingress: ~0.25–0.4 L/hour or ~6–10 L/day

Scenario

During repeated offshore transfer operations, the crew observed recurring signs of water contamination in the thruster lubrication oil. Routine checks showed increased cloudiness and a gradual deterioration in oil condition, especially after periods with frequent manoeuvring and higher load changes. The thruster system remained operational, but the operator wanted to reduce further water ingress and stabilize the oil condition before the next planned service window.

Action

Addvation reviewed the thruster type, oil volume, oil condition, seal arrangement, operating profile, and observed water ingress. Due to the recurring contamination and demanding operating conditions, Thruster Seal Plus was recommended as a reinforced water ingress support treatment.

Recommended starting point: Thruster Seal Plus
Indicative quantity: ~45 L total

Application

The product was applied during a planned port stay, following the recommended dosage, application guidance, and onboard monitoring procedures.

Outcome

Water ingress was reduced and brought under better control. The oil condition became more stable, allowing the thruster system to remain operational while it was monitored toward the next planned maintenance opportunity.

Significant water Ingress - Cable-Laying Vessel

Application Scenario
Water Ingress – Thruster Seal Max for a Cable-Laying Vessel

Vessel type: Cable-laying vessel
Thruster type: Azimuth thruster
Thruster oil volume: ~1,900 L
Observed issue: Significant water contamination and unstable oil condition
Estimated water ingress: ~1.0–1.5 L/hour / ~24–36 L/day

Scenario

During offshore cable-laying operations, the crew observed a significant deterioration in the thruster oil condition. Routine inspections showed increased cloudiness, signs of free water, and unstable lubricant performance after prolonged dynamic positioning and high-load thruster operation. The vessel remained operational, but the contamination level created concern about further seal deterioration and the need to avoid unplanned intervention before the next scheduled service window.

Action

The operator contacted Addvation to assess the situation. Based on thruster type, oil volume, water contamination level, seal arrangement, and demanding operating profile, a maximum water ingress support approach was recommended.

Recommended starting point: Thruster Seal Max
Indicative quantity: ~160 L total

Application

The product was delivered to the vessel's next port and applied during a planned service window, following the recommended dosage, application guidance, and onboard monitoring procedures.

Outcome

Water ingress was reduced and brought under better control. The oil condition became more stable, allowing the thruster system to remain operational while the vessel continued toward the next planned maintenance opportunity.

Why Water Ingress Must Be Taken Seriously

Water ingress can quickly reduce lubrication performance and increase the risk of corrosion, heat, seal wear and bearing damage.

1. Oil contamination
Milky or cloudy oil indicates water contamination and reduced lubrication performance.

2. Corrosion risk
Seawater in the oil can cause corrosion and accelerate internal wear.

3. Heat and friction
Poor lubrication may increase friction, temperature and stress on the seal area.

4. Bearing and seal damage
Untreated water ingress can lead to bearing wear, seal damage and unplanned maintenance.

5. Oil condition before treatment
Light contamination may be treated after assessment. Milky or heavily contaminated oil should normally be replaced before adding ST Seal.