Regal EmpressConversion of Lignum Vitae Sterntube

Bearings to Thordon COMPAC

RE2002.1

3225 Mainway, Burlington, Ontario, Canada L7M 1A6 Tel: (905) 335-1440 Fax: (905) 335-4033

www.thordonbearings.com

Regal Empress Conversion to COMPAC Propeller Shaft Bearings

Vessel Details

Name: Regal EmpressType of Vessel: Passenger Cruise ShipBuilt: 1953Owner: Regal Cruises Limited, BahamasOperator: International Shipping Partners, Florida, USADWT: 7,680Length, Overall: 186m (610 ft.)Length of tailshaft: 6.96m (274”)Tailshaft Diameter: 541mm (21”)No. of Shafts: two

Date of Starboard Conversion: May 15, 1999Shipyard: Bender Shipbuilding and Repair Co., Mobile, Alabama, U.S.A.

Date of PortConversion: November 5, 2001Shipyard: Detyens Shipyard, Charleston, South Carolina, U.S.A.

Regal Empress Conversion to COMPACRegal Empress was dry-docked at Detyens Shipyard in Charleston, South Carolina onNovember 5, 2001 for a port sterntube bearing conversion to Thordon COMPAC fromlignum vitae. The starboard sterntube bearings were converted to COMPAC from lignumvitae on May 15, 1999.

The following table shows the clearances of the bearing conversions and when the conversions occurred.

Port Sterntube Bearing ConversionThe port propeller was removed from the Regal Empress at Detyens Shipyard in earlyNovember, 2001. The existing clearances (0.343”) taken from the lignum vitae bearingsindicated they would need to be replaced. The port shaft was removed and the ligum vitaewas inspected while still installed in the housing. The visual inspection indicated that thealignment was not an issue for the port shaft, unlike the starboard bearing (see followingStarboard Sterntube Bearing Conversion).

After the lignum vitae was removed, the housings were measured. After studying thehousing and alignment patterns, one 24” long bearing was used in the forward stern tubeand one 24” long segment combined with the 32” long segment was used to make up theafter sterntube bearing. This combination was chosen to increase wear life and bearingperformance as the shaft load is spread over a longer bearing. The housingmeasurements indicated the COMPAC bearings could be interference freeze fit into thehousings. The COMPAC bearings were machined according to the finished sizescalculated from the Thordon Bearing Sizing Calculation Program (sheets follow).

The Forward sterntube shaft in way of the bearing was skimmed slightly, but the Aft stern-tube shaft required more additional machining.

The yard installed the bearings by freezing them in liquid nitrogen and easily sliding theminto the correct position in the housings. The yard was instructed to leave a space of atleast 0.025” between each bearing segnment and the keepers. Keepers were made for theshorter bearing segments to prevent axial bearing movement forward and aft.

Water supply requirements were outlined as per the Thordon Engineering Manual to ensurea water flow greater than 22 Gallons per minute (85 L/min).

The propeller was reinstalled, the vessel departed shortly after.

Starboard Sterntube Bearing Conversion

The replacement of the starboard sterntube bearings of the Regal Empress took place atBender Shipbuilding in May 1999.

The existing lignum vitae (installed in 1995) along with the related keeper strips (used to retainlignum vitae pieces) and the propeller shaft were removed from the starboard stern tube.Upon inspection, it was determined that the propeller shaft would require machining.

Inspection of the Bearing Cooling WaterSupply revealed that it had been totallyplugged with rust and scale over the years.Seawater leaking past the stuffing box hadcaused considerable damage in the shafttunnel area.

The water supply system was cleaned andrepaired as necessary to assure a flowgreater than 22 GPM (85 L/min) to thebearings. The requirement for adequatecooling water to Thordon cannot beoveremphasized. Thordon recommended aflow meter with an audible or highly visiblealarm be installed in order to alert the crewin case the water flow is inadvertently cutoff.

The propeller shaft was machined to a maximum forward diameter of 21.543” (547.2mm) andaft diameter of 21.330” (541.7mm). The decision was also made to machine the starboard aftlines prior to reinstallation.

Based on measured stern tube dimensions, the Thordon COMPAC bearing segments were roughmachined on the OD to allow a minimum of 0.030” (0.76mm) to a maximum of 0.040” (1.02mm) diametric clearance between the bearing OD and housing ID to accommodate a bond fit using TG-75epoxy adhesive. A bond fit was used instead of the normal interference fit due to the significant misalignment through the aft bearing. The misalignment of the shaft and housing was so large thatafter line boring to correct the alignment there was insufficient wall thickness to permit an interferencefit.

After the stern tube ID was “roughed up” with a 24 grit wheel to clean the ID and create a suitablebonding profile, the bearing segments as well as the stern tube were thoroughly cleaned with acetonein preparation for adhesive bonding of the bearings.

Due to the significant off-center boring required to correct the stern tube alignment, a thin wallsection remained. As there was insufficient wall thickness, the bearing had to be bonded in.Note the thin bearing wall on the left (inboard) side after boring to correct the misalignment.

After the TG-75 adhesive had been allowed to cure, the I.D. of the bearings were machined inaccordance with alignment data and sizing information from the Thordon Bearing SizingCalculation Program (see next page) using portable boring equipment.

As a result of the off-center boring, the ID’s of the lantern ring, the stuffing box gland and theretainer ring had to be increased in order to assure proper clearance between those components.

The propeller shaft and propeller were carefully reinstalled and the Regal Empress departedon schedule.

3225 Mainway Drive, Burlington, Ontario L7M 1A6 Canada Tel: +1.905.335.1440 Fax: +1.905.335.4033

www.ThordonBearings.com

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