EXCESS CLEARANCE BETWEEN SHROUD CASING AND BLADES :


VIBRATION CAUSING DAMAGE :

Name of ship : M.T. NAND HARI
Year : During 2001 – 2003
Trouble shooting : Low scavenge pressure
No. of Units: Seven 7 L45GFC BHP6160

Ship went for dry-dock during the year 2001. Ship was running at 156 RPM from 2001-2002 at the end of 2002 ship’s speed slowed down and Exhaust temperature went very high. Scavenge pressure was 0.15 kg/cm2. Air cooler cleaned, T/Ch filters cleaned. Engine tried and could not achieve required scavenge pressure. Ship was running at 90 rpm with one auxiliary blower. Ship was witnessing fire almost every day at sea.

M/E turbocharger nozzle ring changed. M/E fuel pump timing, exhaust v/v timing were checked. M/E all 7 units overhauled. Still there was no improvement. M/E Turbocharger rotor replaced. Still there was no improvement. Finally it was found that shroud casing found with excessive carbon deposits. Exhaust gas coming out of nozzle ring, initially goes through blades, but slowly gas bypasses the blades and was passing through excessive clearance between blades and shroud casing, there by lowering turbocharger speed, in turn lowering Scavenge pressure. Shroud casing changed – Engine RPM went to 155 with exhaust temperature within limit scavenge pressure improving to 0.71 kg/cm2.

On a voyage from Argentina to Singapore, Turbine tanker T.T. Torino was having vibration on LP turbine. The vessel was VLCC. On fully loaded passage suddenly L.O pipe joining to turbine AFT bearing sheared off and complete went down to bilges. Because of ships momentum the ahead motion could not be checked. Therefore turbine kept on running a little more than 15’ with out having lub. Oil supply for any of the bearings.

Later on pipe was welded and fitted back in place. Stock of Lubricating oil for one complete change was not sufficient. So in consultation with company mixed engine oil with Hydraulic oil from deck and steering gear oil. And sailed at slow speed till reached the port. Then flushed the system and changed with correct grade of L.O.