Water lubricated shaft bearings pass muster

2020-12-12T09:03:49+00:00 December 12th, 2020|Technology|

A recent inspection of the 20-year-old water-lubricated propeller shaft bearings installed on a twin-screw cruise ship were found to be within classification society parameters.

In addition, the bearings were suitable for continued use for a further 10 years.

At the shipowner’s request, Thordon Bearings attended the unnamed cruise ship’s docking at Damen Brest, France, to assess the propeller shaft liners and outboard bearings of the 2,500 pax-capacity cruise ship.

Her COMPAC bearings were installed in 1999.

Thordon’s Business Development Manager – Marine, Jeffrey Butt, said: “After more than 20 years of service and 6,100 annual operating hours, bearing clearances were significantly below Lloyd’s Register’s 10.5 mm maximum allowable clearance.

The maximum clearance recorded was 7.34 mm on a starboard shaft bearing. The vessel could potentially operate these same bearings for another 10 years,” he claimed.

The condition of the 83,000 gt vessel’s shaft liners – themselves indicative of successful bearing performance – was claimed to be equally impressive.

Gus Juarez, Thordon Bearings’ technician from the Global Service & Support team involved in the inspection, said: “There were some minor circumferential marks on the shaft liners, but they looked well-polished. There was no indication of circumferential grooving or damage. All liners were determined to be in satisfactory shape.”

Copies of all the inspection videos were provided to the LR surveyor and shipowner representatives following the October drydocking.

According to Butt, the reliability and near-obsolescent maintenance requirement of a seawater lubricated shaftline is one of the main reasons why the cruise sector increasingly favours a conventional propeller shaft arrangement over a podded propulsion system.

“We have accumulated data over the past eight years revealing more than 25 incidents where the pod failures resulted in cancelled or changes to cruise itineraries.

I know one vessel that has been in and out of drydock five times in the past eight years, resulting in 55 itinerary changes, two cancelled sailings, several shortened port stays, and thousands of dollars in compensation. You don’t seem to have this kind of bother with a shafted ship,” Butt added.

“Compared to pods, a ship fitted with COMPAC has an enviable track record. Performance, reliability and environmental sustainability is unmatched,” he said.

The shaft inspection at the Brest yard was the second cruise ship to emerge from a drydocking with a Thordon bearing in near perfect condition after decades of operation.

In September, 2015, during the inspection of a sistership, surveyors recorded a bearing wear down of 7 mm. This was 17 years after the system was installed.

Craig Carter, Director of Marketing and Customer Service, Thordon Bearings, said: “Based on our cruise installations to date, a seawater-lubricated propeller shaft system typically has a wear-life of 25 years, saving millions in maintenance costs and emergency repairs. There are no lubricants to purchase, no service contracts to sign, reduced maintenance budgets and zero pollution risk,” he stressed.

Thordon has supplied water-lubricated bearing systems to cruise ships operated by Princess Cruises, Seabourn, Disney Cruises, Viking Cruises, MSC Cruises, P&O Cruises, Oceania, and Regent Seven Seas, among others.