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Towing in ice during escort
Responsible organisation
2021 (English)Report (Other academic)
Abstract [en]

This project has aimed to evaluate towing practices and towing forces for existing and new bow types, specifically EEDI bow types, to determine if there are challenges to towing in ice which can be addressed by updates to existing requirements, rules or best practice documents. The evaluation was undertaken using feedback from operators of EEDI compliant merchant ships, feedback from captains of icebreakers that have undertaken towing in ice of EEDI compliant vessels, a review of mooring arrangements of EEDI compliant vessels and an analysis of the towing forces using force-vector analysis. In addition, the Aker Arctic Ice Simulator, usually used for training crews operating icebreakers, was used to simulate towing forces. Due to COVID19 restrictions a number of planned activities associated with direct observation of towing in ice (both onboard the icebreaker and merchant vessels) were subsequently cancelled. The project has therefore drawn the majority of its practical conclusions from interviews. With respect to towing the main differentiating point for EEDI compliant ships is the sharp bow form, the main operational consequence of which (with regards to towing) is the positioning of the chocks and bollards on the merchant vessel mooring deck: Sharper EEDI bows may lead to situations where the bollard and chock positioning results in a smaller angle between the whisker wire and the centerline (spread angle), leading to less control of the merchant vessel (course stability). Although utilising the Aker Arctic Ice Simulator did not advance to a stage where the system can be used as a platform for testing different mooring arrangements,insight from using the simulator, combined with a review of full scale towing measurement data and more straightforward analytical analysis confirmed the overall operational view that bollard location has a direct influence on the course stability of the ship under tow and consequently that bollard / chock location is an important factor in the tow. However, considering regulating the bollard / chock location in isolation poses problems, because the line towing angle (which is the driver for course stability under tow) is also dependent on the whisker wire length (from the icebreaker) and the distance between the bow of the merchant vessel and the icebreaker’s aft deck (which is driven by the operational need to have the towing block over the icebreaker’s aft deck to enable ease of connection / disconnection).

Place, publisher, year, edition, pages
Sjöfartsverket , 2021. , p. 61
Series
Trafikverkets forskningsportföljer
Keywords [en]
Towing, Ice Operations, EEDI
Keywords [sv]
Bogsering, Isoperationer, Sjöfart
National Category
Marine Engineering
Research subject
FOI-portföljer, Sjöfartsområdet
Identifiers
URN: urn:nbn:se:trafikverket:diva-17752Archive number: TRV 2019/50479OAI: oai:DiVA.org:trafikverket-17752DiVA, id: diva2:1902238
Projects
Sv/Fi Styrelsen för vintersjöfartsforskning utlysningar 2020, 2021 och 2022 samt 2023
Funder
Swedish Transport Administration, TRV 2019/50479Available from: 2024-10-01 Created: 2024-10-01 Last updated: 2025-02-10Bibliographically approved

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Marine Engineering

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CiteExportLink to record
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Citation style
  • apa
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