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New class notations aim to improve stern tube bearing performance

DNV GL has revised its class rules for single stern tube bearing installations and introduced two new class notations, “Shaft align(1)” and “Shaft align(2)”, to help customers better manage the risk of stern tube bearing failure. The new class notations can be assigned to both newbuilds and vessels in service in conjunction with propeller shaft withdrawal.

The classification rules covering shaft alignment are formulated to achieve an acceptable distribution of loading on the shaft bearings and lubrication of the aft bearing, taking into consideration the bending moment induced by the propeller during operation. However, during turning manoeuvers at higher ship speeds, exaggerated propeller bending moments can occur, potentially resulting in a reduced shaft-bearing contact area and an exponential increase in local pressure and thermal loading. This could cause damage to the aft bearing. Most of the reported bearing damages have been observed in the aft-most part of the aft bearing, typically during a starboard turn on a right-handed propeller installation. The new rules put additional focus on the impact of these transient hydrodynamic propeller forces and moments, induced in turning conditions, on the aft-most propeller shaft bearing.

In the “Shaft align” class notations and the revised main class requirements for single stern tube bearing installations, a multi-sloped bearing design is mandatory. This is further supplemented by an additional evaluation of the aft bearing lubrication condition considering an increased propeller-induced hydrodynamic bending moment on the aft bearing in the downward direction. Additional design and installation criteria also assist to increase the operating margins and enhance bearing performance and fatigue lifetime in normal continuous running conditions.

“We are always looking to push the development of our rules forward to help our customers operate and maintain more reliable and safe ships,” says Geir Dugstad, Director of Ship Classification at DNV GL – Maritime. “With this revision to the DNV GL class rules and the two additional class notations, we will enable owners to enhance bearing performance, and benefit from a longer lifetime in their stern tube installations.”

The notation “Shaft align(1)” is intended for propulsion systems installed on vessels with conventional hull forms and incorporates enhanced aft bearing performance during normal and turning operating conditions. “Shaft align(2)” is intended for propulsion systems requiring additional calculations to predict hydrodynamic propeller loads during turning conditions, for example vessels with non-conventional hull forms such as asymmetric stern, twin skeg etc. Design and in-service follow-up rules for the class notations are included in the updated DNV GL rules for the classification of ships, Pt.6 Ch.2 Sec 10 and Pt.7 Ch.1 Sec 6(38) respectively.

“We hope that by introducing the revised main class rules for single bearing installations and ‘Shaft align (1) or (2)’ we can substantially reduce stern tube bearing failures,” says Oddvar Deinboll, Head of the Machinery section at DNV GL – Maritime. “We’ve received a lot of positive responses from the industry and are already working on some concrete projects.”

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Annual Western Mediterranean LYSCWG on 26-27 April

As in previous years, IIMS is hosting an event around the Palma Superyacht Show on the island of Majorca on Thursday 26 to Friday 27 April for large yacht and small craft surveyors. In recent years the event has gone from strength to strength and the agenda for this year looks equally appealing.

On the first morning the group will meet outside the Superyacht Show entrance to be transported the few miles to take a look at the METALNOX facility at Calvia.
Meet at 08.45 – Transfer to METALNOX by bus
Amongst other things to be seen at METALNOX is the Prop Scan computer system which measures the size and shape of the propellers of ships and yachts internationally. Prop Scan is the first certified ISO system for the correction, reconfiguration and optimization of propellers.
13.15 – Lunch back in Palma

After lunch the group will meet in the classroom adjacent to the Superyacht Show for a series of specially prepared presentations.
14.30 – Karen Brain: Understanding your insurance cover. What do Marine Professionals need?
15.30 – Phil Duffy (topic to be confirmed)
16.30 – Bob Hoghton: Mini ISM
17.45 – Close
19.15 – Dinner

A prompt start on the second day within the show itself gives Mike Schwarz, IIMS CEO, the opportunity to bring delegates right up to date with what has been happening in and around the IIMS family over the past few months.

The group will then transfer by bus for the second facility visit, this time a trip to Oscar Sierra before returning to the Superaycht Show. At that point the training event officially concludes and delagates can then enjoy the show for the rest of the afternoon courtesy of a free VIP pass from IIMS.

Oscar Sierra Safety Equipment S.L. is one of the leading marine safety specialists in the Mediterranean. They are both manufacturers and distributors of marine safety equipment. The group will focus on looking at life saving and fire fighting equipment during their visit.

The cost of the event is €190. This includes training and bus transfers on both days, plus a complimentary VIP entry ticket to the show which can be used over the weekend too. Lunch and dinner is at the individual’s cost. Attendance at the event also attracts 5 CPD points.

To register your place at the event please email Cathryn Ward or call her on + 44 23 9238 5223. We will invoice you.

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Operators and surveyors urged to test cargo hold’s bilge system to minimise claims

Operators and surveyors urged to test cargo hold bilge systems to minimise claims
Operators and surveyors urged to test cargo hold bilge systems to minimise claims

The UK P&I Club has reminded those working in the marine industry that significant insurance damage claims can result if a bulk cargo is damaged due to the leakage of the bilge system into a loaded bulk cargo hold.

To reduce the chance of such cargo damage, operators and surveyors are advised to inspect and test the cargo hold bilge system as part of the routine pre-loading checks of the cargo holds.

Inspection and testing of cargo hold bilge system non-return valves should be included in routine pre-loading checks of the holds. These non-return valves may not be seated tightly, because of the presence of previous cargo residue and scale around the valve seat.

Hold bilge sounding pipes should be positively proven to be unobstructed and comparisons made between the documented maximum pipe height and actual measurement at the deck datum point. The full depth of the sounding pipes should be confirmed when sounding any cargo hold.

Furthermore, maintenance and operational safeguards must be conducted in the hold bilge system:

Bilge system valves and pipework should be periodically checked and maintained as part of the planned maintenance system.

Rigorous procedures should be in place to prevent valves being left open when not in use.
Should a hold ingress alarm be activated, it should be thoroughly investigated, including checking all related systems and pumping of the bilges to observe for any discharge.

All the above have as a purpose to deal with the the risks of potential damaged cargo and the associated insurance claims.

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Rolls-Royce to provide tug sector with its first Hybrid System

Photo credit: Rolls-Royce
Photo credit: Rolls-Royce

Rolls-Royce will supply the tug boat sector with its first hybrid propulsion arrangement for installation to a multi-purpose tractor tug undergoing construction for Baydelta Maritime LLC. The vessel is being built at Nichols Brothers Boat Builders, in Washington State, U.S.A.

The order represents the first hybrid tug using proven Rolls-Royce hybrid technology, the first installation of a hybrid system for Nichols Brothers and the first hybrid tug designed by Jensen Maritime, Crowley Maritime Corp’s Seattle-based naval architecture and engineering firm.

The 100-foot long tug will feature the same ship assist and tanker escort capabilities of existing Delta Class harbour tugs but with greatly improved towing performance. The Rolls-Royce hybrid system enhances the vessel’s escort capability, enabling the tug to provide support for assisting the ultra-large container ships that operate from US West Coast ports.

Rolls-Royce will supply all electric motors, shaft generators and a power management and control system. The Hybrid arrangement provides power to US255 azimuth thrusters with ducted fixed pitch propellers that can be rotated 360 degrees around the vertical axis. This arrangement optimises omni-directional thrust and manoeuvrability as well as providing improved crash stop capability.

Erik Larsen, Rolls-Royce, Vice President – Tug and Fish, Americas, said: “Baydelta Maritime is a long-standing customer for Rolls-Royce, but this order is of particular significance because it marks our first Rolls-Royce Hybrid System for a tug. The tug will provide improved fuel efficiency and emissions. It shows this market, that the Rolls-Royce portfolio extends way beyond our US-type azimuth thrusters, the propulsion system of choice for this segment.”

Rolls-Royce and Baydelta have been working together since 1990s, when the San Francisco -based operator specified its first azimuth thrusters. Since then Baydelta’s entire fleet of tractor tugs is equipped with drive units.

“Our US 255 azimuth thrusters are ideally suited to provide the manoeuvrability and bollard pull needed for operations in larger harbours, terminals and escort applications. One of the reasons for success is the product’s ability to provide bollard pull of more than 90 tons.

“The key benefit operating these thrusters in a hybrid configuration is that it reduced the power requirement. Typically, a tug of this size would need a power output 2500kW. The hybrid arrangement allows operators to achieve the required bollard pull from a smaller engine. It provides greater operational flexibility,” Larsen explained.

Peter Zwart, VP of Operations, Baydelta Maritime, highlighted the maintenance benefits of the Rolls-Royce system. “We started building this current class of tugs in 2007 and now all our tugs have Rolls-Royce thrusters, the US 255. We know that with proper maintenance they last a long time, hopefully up to 15 years without a major overhaul”.

Commenting on their operational performance, Mark Barnum, Captain, Baydelta Maritime, added: “In San Francisco Bay containerships can enter at high rates of speed to maintain manoeuvrability and Rolls Royce thrusters are very responsive. We can go from full ahead to full astern in under 30 seconds. They also allow us to provide pilots with high tonnage breaks to prevent anything from happening during manoeuvres.”

The new tug Jensen Maritime has designed for Baydelta will be capable of a 90 short-ton bollard pull and capable of carrying up to 71,000 gallons of fuel, 4,300 gallons of fresh water, a large pilot house will provide all-around visibility, and the deckhouse has an open feel with a large mess and lounge area along with accommodations for a 8-person crew.

Bryan Nichols, Director Business Development, Jensen Maritime, said: “The development of this new tug demonstrates our commitment to innovative, environmentally friendly design while continuing to deliver powerful, high-quality performance. This tug will meet the industry’s demand for strong, yet nimble vessels with the quality design people expect from us.”

The tug is planned for delivery in February 2019.

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Revolutionary ultraviolet light-emitting diodes fouling prevention technology under development

Revolutionary ultraviolet light-emitting diodes fouling prevention technology under development
Revolutionary ultraviolet light-emitting diodes fouling prevention technology under development

AkzoNobel has teamed up with Netherlands based healthcare company Royal Philips to develop ultraviolet light-emitting diodes fouling prevention technology.

The system will use technology developed by Royal Philips with the aim of combining experience from both companies to produce an economically viable solution for underwater fouling prevention.

The system will integrate UV light-emitting diodes in a protective coating, which AkzoNobel says will allow for the UV light to be emitted from the coating surface, preventing biofouling from accumulating.

“In our sustainable fouling control initiative, we actively explore and develop alternatives to biocidal-based solutions,” said Oscar Wezenbeek, director of AkzoNobel Marine and Protective Coatings. “This development is a great proof point of our continuous focus on delivering eco-friendly solutions to our customers.”

And the organisation says that complexities will be overcome and the technology will revolutionise the fouling control industry.

Initially, the focus will be on applications for ships, yachts and offshore assets, but the project could potentially be extended to include other surfaces challenged by bio-fouling issues.

“This unique project is fully aligned with AkzoNobel’s continuous focus on innovation,” added Klaas Kruithof, AkzoNobel’s chief technology officer. “In our quest to not only protect and colour, but also functionalise surfaces, we actively look for complementary technologies and partners to innovate with.

“In this case, the combined capabilities and technology of Royal Philips and AkzoNobel will enable us to accelerate the realisation of this transformative innovation, which we intend to initially market ourselves and consider licensing out to third parties for large-scale adoption.”

The system will be biocide-free.

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