ViganGeneva DryTelestackPort of StocktonSailors SocietyVan Aalst
  • Van Aalst
  • TMS Awards 2023
  • Port of Stockton
  • Bühler GmbH
  • Telestack
  • Geneva Dry

Small propellor defects can result in increased radiated noise

Small propellor defects can result in increased radiated noise

(Posted on 24/02/23)

The slightest deviation in the machining, polishing, and finishing of ships’ propeller blades could result in underwater radiated noise and cavitation, even if defects are within the maximum tolerance allowed by classification societies and the ISO 484-1 standard.

A Canada Transport-funded study on the impact of manufacturing tolerances on propeller performance – carried out by Memorial University of Newfoundland, DRDC Atlantic Research Centre, and propeller manufacturer Dominis Engineering – found the slightest change in propeller geometry resulted in “significant” cavitation, and much earlier than previously thought.

The behaviour of a section of propeller blade with leading edge defects of 94µm, 250µm and 500µm were studied using Computational Fluid Dynamics (CFD) at the DRDC-Atlantic Research Centre, and Memorial University of Newfoundland, in a three-year project that concluded last year.

Project lead, Dominis Engineering President Bodo Gospodnetic, said: “Experimental results show that current widely accepted propeller manufacturing tolerances as stated in the ISO standard need to be thoroughly evaluated and investigated further.”

The current tolerance for a defect to the leading edge of a propeller blade is 500µm (0.5mm).

Ship propellers are manufactured according to ISO 484-1, with the majority of propellers made from castings rough machined on CNC (Computer Numerically Controlled) mills and then finished using robotic and manual grinding. However, robotic and manual grinding of propeller surfaces introduces inaccuracies and deviations from the approved design, which can lead to cavitation, erosion, noise, vibration and loss of propeller efficiency.

“The leading-edge is a very challenging area to manufacture accurately yet it has a strong influence on sheet, streak and vortex cavitation,” said Gospodnetic.

Researchers found that a ship with “defective” propeller must travel at a given percentage slower than a vessel with a “correct” propeller to operate below the cavitation inception speed and remain quiet. For example, a ship with a propeller defect of 0.5mm would have to sail at 45% of the speed of a defect-free propeller to avoid cavitation noise. The smaller the defect, the less speed reduction is required to remain quiet.

“The 0.5mm defect tested is one of the tightest ISO 484-1 propeller manufacturing tolerances yet it has been demonstrated that it affects cavitation inception significantly and detrimentally. The rules need tightening up,” said Gospodnetic.

ISO 484-1:2015 has been a standard for propellers since 1982 and although the standard was reviewed in 2015 and 2022, the allowable tolerance and geometry remains unchanged.

“We know that 80% of underwater radiated noise comes from the propeller, but if ships are legislated to be quiet in sensitive habitats such as the Juan de Fuca Strait then they will have to limit their speed to below the cavitation inception speed,” said Gospodnetic.

While initial CFD studies show how very small defects can influence cavitation inception research partners are looking for funding to continue their investigation in second phase model tests in a cavitation tunnel.

Latest News

Berge Neblina sets sail with four carbon-saving rotor sails

(Posted on 12/07/24)

Berge Bulk has announced the successful installation of four emissions-reducing rotor sails on Berge... Read more


Wärtsilä simulators to support Singapore's Wavelink Maritime Institute

(Posted on 12/07/24)

Technology group Wärtsilä has supplied its new dual-fuel engine simulator technology for Wavelink... Read more


Oulu extends cargo handling with Konecranes Gottwald

(Posted on 04/07/24)

The Finnish Port of Oulu has ordered a Konecranes Gottwald ESP.7 Portal Harbor Crane to improve cargo... Read more


Intergis adds flexibility in South Korea with Konecranes Gottwald Gen 6 MHC

(Posted on 28/06/24)

Intergis Co., Ltd ordered a Konecranes Gottwald ESP.5 Mobile Harbour Crane to improve its bulk and general... Read more


Live freight rate visibility across routes and maturities

(Posted on 28/06/24)

AXSMarine, a pioneer and market leader in the provision of advanced solutions and market intelligence... Read more


Weathernews enhances SeaNavigator platform with powerful new tools

(Posted on 19/06/24)

In line with its focus on continuous improvement of its cloud-based SeaNavigator voyage-optimization... Read more


BOA: Ships should be built to seawater-lubricated sterntubeless design

(Posted on 14/06/24)

Future newbuild ships of all types should be built without a sterntube and with a seawater-lubricated... Read more


Survitec white paper calls for greater oversight for fire safety inspections

(Posted on 07/06/24)

Global Survival Technology solutions provider Survitec has highlighted the dangers of inadequate maintenance... Read more


Making sense of real-time load measurement

(Posted on 07/06/24)

The handling of dry bulk materials used to be a completely manual process, but it is now being increasingly... Read more


Laskaridis Shipping and Metis to find pathways to low carbon future

(Posted on 01/06/24)

A research project which brings together The Cambridge Centre for Advanced Research and Education in... Read more


CimbriaBühler GmbHTBA GroupTMS Awards 2023Port of South Louisiana
  • Vigan
  • TBA Group
  • Port of South Louisiana

Subscribe to our newsletter

Keep up to date with the latest global news in bulk cargo handling and shipping