WTT Series (Transverse Tunnel Thruster)

Perform visual inspection and NDT (non-destructive testing) according to OEM and classification society standards. Polishing in combination with edge damage repair increases operating efficiency by 2-5%. Check for pitting, erosion patterns and corrosion spots; document severe pitting areas.

5-year overhaul: Disassemble and inspect all seals. 10-year overhaul: Complete replacement of blade foot O-rings. Check for water penetration in jet thruster assembly. Seals are critical for system protection.

Measure propeller shaft wear with poker gauge (between last two stern tube seals). Perform complete inspection of tooth clearance, tooth pattern and shaft seals. 5-year overhaul: seal replacement. 10-year overhaul: comprehensive replacement.

5-year overhaul: Check bearing clearance and wear. 10-year overhaul: Complete bearing replacement, reset preload, perform NDT inspection. Check main bearing axial clearance wear with feeler gauge (0.1 mm); maximum wear limit 2 mm. Use Wärtsilä bearing wear measurement system for remote monitoring of propeller shaft shoulder.

Check gear oil regularly. At critical wear limits: partial change (bleed-and-feed) or complete oil change. Monitor water content in oil (critical >1000 ppm). Check fine filtration system and redundant filter options. Continuously filter out water ingress. Use all Wärtsilä-approved spare parts. 5-10-year overhaul: Perform oil change and filter maintenance.

Check for oil leakage at outer seal. Inspect inflatable emergency seal and inner rope guard. Fully serviceable underwater without habitat or discharge. Measure seal gap and wear. Check retrofit compatibility with other seal types. Confirm compatibility with EAL and mineral oils.