Wartsila Stern Tube Seal (Lip Seal)
A passive multi‑lip rubber stern tube seal that prevents oil leakage and seawater ingress, using an air or oil barrier (Airguard/Enviroguard) to enhance sealing performance.
Inspector Detail
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Common issues
- Individual seal lip wear leading to oil leakage or seawater ingress
- Loss of air/oil barrier pressure between the lips
- Seal housing misalignment following shaft movement or bearing wear
- Contamination of the barrier air supply
- Lip hardening or cracking with age, particularly after long dry-docking periods ashore
- Monitoring system (oil level or air pressure sensor) faults
Inspection checklist
- Barrier air or oil pressure and flow check
- Forward and aft seal chamber oil level check
- Visible leakage inspection at the seal housing
- Air supply filter/dryer condition
- Monitoring alarm function test (low oil level / low air pressure)
- Seal lip condition assessment when accessible at dry dock
- Shaft alignment check where accessible
Service intervals
| Oil/barrier level and pressure check | daily to weekly during watchkeeping rounds |
| Air supply filter/dryer service | per OEM, commonly every 3-6 months |
| Full lip seal renewal | typically tied to the dry-docking cycle (often around every 5 years alongside class special survey), or sooner on condition if leakage is observed |
| Oil sampling | per the vessel's PMS, commonly every few months |
Typical wear limits
| Lip seal condition | generally assessed by leakage rate trend and visual lip condition rather than a single measured dimension; an upward trend in oil consumption or barrier air usage toward the seal manufacturer's stated alarm threshold indicates renewal is due - the exact figure must be confirmed against the specific seal size's own technical manual (Airguard, Enviroguard, FSTL or FST), as it is not generalisable across the seal range |
Ranges are typical for this design class. Always confirm against the manufacturer documentation for your serial number.
Critical spares
- Complete lip seal ring set, forward and aft
- O-rings and gaskets for the seal housing
- Barrier air filter/dryer element
- Seal housing fasteners
Safety
- Stern tube oil pollution risk to the marine environment on seal failure
- Confined space entry for aft peak/stern tube inspection
- Pressurised barrier air supply system
- Diver or dry dock work around the propeller and rudder during seal renewal
Class survey
Stern tube seal condition and lubricating oil consumption records are typically reviewed at each class survey; renewal is commonly tied to tailshaft/stern tube survey intervals, and any leakage above the alarm threshold should be reported and addressed ahead of the next scheduled dry-docking.
Components & Design
Component data being added…
Technical Data
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Common failures & inspection points
Service & Maintenance
Seal drain inspection daily. Air supply pressure check daily (Airguard). Oil consumption monitoring — abnormal increase indicates seal wear. Seal replacement at drydock (every 5-10 years or as needed). Shaft liner condition check at each seal replacement.
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