Stern Shaft Assembly Repair and Overhaul
During its last dry dock chemical tanker, Sichem Challenge was known to have worn stern shaft bearings and a worn stern shaft sleeve on her water-lubricated shaft line arrangement.
ATZ was contracted by Selandia to provide a parts and attendance package to manage the overhaul of the stern shaft arrangement, supplying all seal, bearing and tailshaft sleeve parts to complete the repair/overhaul
ATZ attended the docking of Sichem Challenge to supervise and carry out this work package.
- Design stern shaft sleeve and bearing dimensions to meet DNV class approval criteria
- Attend vessel and ensure yard manufacture and installation meets makers guidelines
- Work with the customer and attending DNV surveyor to ensure that all parts supply, installation calculations and equipment testing met classification society requirements.
During the previous docking of Sichem Challenge, it was noted that the stern shaft sleeve was heavily corroded in way of the shaft seal, requiring local machining and fitment of a bespoke stern seal size. Furthermore, it was seen that the water-lubricated stern shaft bearings had significant wear and would need replacing at the next docking.
ATZ undertook the supply of components associated with the stern shaft works.
Prior to attendance, ATZ conducted all relevant design calculations for seal sizing, stern shaft sleeve and composite bearing machining.
ATZ supplied oversized bronze sleeve billets for the yard to machine to ATZ calculated dimensions. The new sleeve would replace the existing sleeve on the removed stern shaft and be designed to return the stern shaft to the original design dimensions. This would allow fitment of new, to original design size, stern seal components.
The ATZ supplied composite bearing billets were machined by the yard to calculations and drawings supplied by ATZ and were freeze fitted in the sterntube in place of the removed worn rubber-type bearings.
With the bearings in place, the shaft was re-inserted in the sterntube and coupled to the intermediate shaft. This allowed ATZ to conduct assembly and test of the stern shaft seal.
All AtZ design calculations, test results and measurements were presented to the customer and attending DNV surveyor.
ATZ presented the composite bearing commissioning protocol to the crew prior to departure.
ATZ Marine Technologies supplied quality propulsion equipment in good time in support of the Sichem Challenge dry dock and supported the stern propulsion activities before, during and after the dry dock and was in attendance during the dock itself.
Sichem Challenge was successfully overhauled to the satisfaction of the Selandia Ship Management and DNV.