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12 pages, 3510 KiB

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Using Onboard-Produced Drinking Water to Achieve Ballast-Free Management

by Kun-Tu Lu, Hon-Kit Lui, Chen-Tung Arthur Chen, Li-Lian Liu, Lei Yang, Cheng-Di Dong and Chiu-Wen Chen

Sustainability 2021, 13(14), 7648; https://doi.org/10.3390/su13147648 - 8 Jul 2021

Cited by 6 | Viewed by 4626

Abstract

Based on the International Convention for the Control and Management of Ships’ Ballast Water and Sediments (the Ballast Water Management Convention, or BWM Convention) of the International Maritime Organization, from 8 September 2017, all ships must have an approved Ballast Water Management Treatment System (BWTS) to prevent the invasion of alien species through the discharge of ballast. Generally speaking, the need for an approved BWTS is limited to large vessels, as they are too large or too expensive for small vessels to install. This study aims to propose a simple ballast-free approach for small vessels (e.g., tugs, workboats, research vessels) that require ballast to compensate for the weight loss of fuel when sailing. Our approach involves refitting the dedicated ballast tank of these small vessels to be drinking water tanks and filling the tanks with onboard-generated distilled or reverse osmosis water to adjust the stability of the ships. We assessed our approach using three vessels. Two ships using our proposed method were certified by the American Bureau of Shipping as containing no ballast water tank, and not being subject to the BWM Convention. This study provides an environmentally harmless, easy to use, and economical approach for small vessels to comply with the BWM Convention. Full article

(This article belongs to the Collection Reviews, Advances and Applications in Environmental Sustainability)

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16 pages, 31014 KiB

Open AccessArticle

Development and Experiments of an Electrothermal Driven Deep-Sea Buoyancy Control Module

by Jiaoyi Hou, Weifeng Zou, Zihao Li, Yongjun Gong, Vitalii Burnashev and Dayong Ning

Micromachines 2020, 11(11), 1017; https://doi.org/10.3390/mi11111017 - 19 Nov 2020

Cited by 16 | Viewed by 4174

Abstract

Due to the extremely high pressures in the deep sea, heavy ballast tanks and pressure compensating hydraulic tanks are typically required to support the operation of classic buoyancy controls. Buoyancy control systems driven by phase-change materials (PCM) have unique advantages over conventional hydraulically actuated buoyancy control systems, including high adaptability for deep-sea exploration and simple, lightweight, and compact structures. Inspired by this, a buoyancy control module (BCM) was designed with flexible material as the shell. Instead of a conventional mechanical system, the device uses an electric heating drive to control buoyancy by heating and cooling the PCM. Based on the principle of pressure compensation, this device can adjust the buoyancy of a small underwater vehicle in a deep-sea high-pressure environment. The BCM successfully adjusts the buoyancy to lift itself up and down in the South China Sea at a depth of 3223 m. The performance of the phase-change BCM to control buoyancy under high pressure is validated by systematic experiments and theoretical analysis. Our work proposes a flexible scheme for the design of a deep-sea phase-change-driven BCM and highlights its potential application in deep-sea micro-mechanical systems, especially soft robots. Full article

(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines)

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15 pages, 6848 KiB

Open AccessArticle

Failure Analysis on a Collapsed Flat Cover of an Adjustable Ballast Tank Used in Deep-Sea Submersibles

by Fang Wang, Mian Wu, Genqi Tian, Zhe Jiang, Shun Zhang, Jian Zhang and Weicheng Cui

Appl. Sci. 2019, 9(23), 5258; https://doi.org/10.3390/app9235258 - 3 Dec 2019

Cited by 1 | Viewed by 3783

Abstract

A flat cover of an adjustable ballast tank made of high-strength maraging steel used in deep-sea submersibles collapsed during the loading process of external pressure in the high-pressure chamber. The pressure was high, which was the trigger of the collapse, but still considerably below the design limit of the adjustable ballast tank. The failure may have been caused by material properties that may be defective, the possible stress concentration resulting from design/processing, or inappropriate installation method. The present paper focuses on the visual inspections of the material inhomogeneity, ultimate cause of the collapse of the flat cover in pressure testing, and finite element analysis. Special attention is paid to the toughness characteristics of the material. The present study demonstrates the importance of material selection for engineering components based on the comprehensive properties of the materials. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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