Control of ship tank heating systems to increase their energy efficiency

An important problem in the operation of icebreakers and Arctic ships is to prevent excessive icing of ballast tanks above the waterline. Uncontrolled ice formation can damage ballast systems and lead to malfunctions of ballast systems during cargo operations. This paper presents an analysis of the dynamics of water temperature in a ballast tank when the heating system is turned on and off. Recommendations on the control algorithm for the heating system that provides maximum energy efficiency are proposed.

Pseudocochlodinium profundisulcus Resting Cysts Detected in the Ballast Tank Sediment of Ships Arriving in the Ports of China and North America and the Implications in the Species’ Geographic Distribution and Possible Invasion

Over the past several decades, much attention has been focused on the dispersal of aquatic nonindigenous species via ballast tanks of shipping vessels worldwide. The recently reclassified dinoflagellate Pseudocochlodinium profundisulcus (previously identified as Cochlodinium sp., Cochlodinium geminatum, or Polykrikos geminatus) was not reported in China until 2006. However, algal blooming events caused by this organism have been reported almost every year since then in the Pearl River Estuary and its adjacent areas in China. Whether P. profundisulcus is an indigenous or an invasive species has thus become an ecological question of great scientific and practical significance. In this study, we collected the sediments from ballast tanks of ships arriving in the ports of China and North America and characterized dinoflagellate resting cysts via a combined approach. We germinated two dark brownish cysts from the tank of an international ship (Vessel A) arriving at the Jiangyin Port (China) into vegetative cells and identified them as P. profundisulcus by light and scanning electron microscopy and phylogenetic analyses for partial LSU rDNA sequences. We also identified P. profundisulcus cyst from the ballast tank sediment of a ship (Vessel B) arriving in the port of North America via single-cyst PCR and cloning sequencing, which indicated that this species could be transported as resting cyst via ship. Since phylogenetic analyses based on partial LSU rDNA sequences could not differentiate all sequences among our cysts from those deposited in the NCBI database into sub-groups, all populations from China, Australia, Japan, and the original sources from which the cysts in the two vessels arrived in China and North America were carried over appeared to share a very recent common ancestor, and the species may have experienced a worldwide expansion recently. These results indicate that P. profundisulcus cysts may have been extensively transferred to many regions of the world via ships’ ballast tank sediments. While our work provides an exemplary case for both the feasibility and complexity (in tracking the source) of the bio-invasion risk via the transport of live resting cysts by ship’s ballast tanks, it also points out an orientation for future investigation.

COATINGS AND PERMANENT MEANS OF ACCESS – THE ANTI-CORROSION CHALLENGES

The introduction of new regulations for Means of Access (MA) has led to an increase in the number and complexity of access openings, an increase in the size of the access openings in the ship’s structure, and a stricter maintenance regime which presents new challenges throughout the life of modern vessels. Several of the major issues at the design stage of Permanent Means of Access (PMA); the construction of ships; the application of protective coatings during new building, together with coating maintenance during the service lifetime; problems related to cleaning holds after cargoes have been removed; action by the Butterworth crude oil washing action and the challenges of maintenance in ballast tanks, are discussed in this paper.

THE ECONOMICS OF A LONG TERM COATING

An important challenge during ship construction is the protection against corrosion of the ballast tanks. These tanks have many compartments, contain multiple structural elements and play a critical role in the seaworthiness. The majority of the ballast tanks are prepared and coated according to IMO Performance Standard for Protective Coating regulations (PSPC), using a light colored epoxy coating that, when maintenance is being performed by the crew, must remain in a “good” condition for 15 years. This method is set next to a protection system applied by a given owner who keeps its ships in an excellent condition for their complete lifetime using a long term coating. More attention is paid to the preparation and application of the coating and consequently it protects the ballast tanks for more than 25 years. These coating strategies are compared in an economic analysis, supplemented with a sensitivity analysis to evaluate the outcomes due to variable parameters. The results indicate that a long term coating only pays off for owners willing to keep the ballast tanks of their vessels in a good condition for the complete lifetime. The decisive factor is that a long term coating entails no recoating in dry dock. The latter results less toxic components in the atmosphere.

A STUDY INTO THE COATING THICKNESS OF SHIP BALLAST TANKS

Ballast tanks are expected to be coated according to the IMO Performance Standard for Protective Coating regulations (PSPC15), in addition to the paint application requirements of the paint producer. In general, a coating system should consist of minimum two spray coats of light-colored epoxy coating on flat surfaces with a Nominal total Dry Film Thickness (NDFT) of 320 μm and 90% of all thickness measurements greater than, or equal to the NDFT and none of the remaining measurements below 0.9 x NDFT (the “90/10 rule”). Allegedly, the value of 320 μm in this PSPC15 rule may be misconstrued as a benchmark for coating application on flat surfaces, eventually leading to a non-PSPC15 compliance due to the resulting variation in coating thickness violating this 90/10 rule. This study indicates that over the years, the arithmetic mean in-situ DFT appears to be 498±18 μm and that too high and low thicknesses, below 288 μm and above 800 μm, were noted in the field. Analysis of a survey of ballast tank coating performance of ships indicates that too low thicknesses appear to be negatively impacting the average theoretical ballast tank performance. However, when an application mean DFT benchmark of 525 μm is used, the coating will almost surely comply to the 90/10 rule and the risk of falling below the 288 μm threshold is small, less than 2% in most cases. Consequently, using 320 μm as a mean DFT benchmark could result in a non-PSPC15 compliance with the in-situ ascertained coating thickness variation as this does not exclude coating thicknesses below 288 μm, which may then result in a significantly less than average theoretical coating performance. If the coating application is performed very evenly, the benchmark may be reduced to 429 μm with a probability of falling below 288 μm reduced to 0.1%. It should therefore be emphasized that the PSPC15 requirement is a coating system framework description, and that the requirement should be broadened to include a mean DFT as a coating applicator benchmark together with a clearly specified minimum and maximum DFT, in order to avoid any misinterpretations.

SIMULATING FLOOD RECOVERY MANOEUVRES USING A FREE-RUNNING SUBMARINE MODEL

Managing submarine safety, effectively, requires an understanding of many areas of platform performance, including its ability to manoeuvre. QinetiQ’s free-running submarine model (FRM) capability, the second generation Submarine Research Model (SRMII), forms a key part of the UK’s predictive manoeuvring capability that supports the MoD’s ability to conduct hydrodynamic assessment of the manoeuvring and control performance of the Royal Navy’s current and future submarines. Uniquely for an FRM, the SRMII has a large and capable ballast system. This is able to emulate a flooding incident within a submarine compartment and the subsequent emergency recovery procedures, which may include blowing the submarine’s main ballast tanks. This paper discusses how the SRMII’s ballast system was used to generate model-scale trajectories, which are not obtainable with many other FRMs. The experimental data were used to successfully validate the mathematical model, which predicts the maximum pitch angle response of a full-scale submarine to a compartment flood, to within an average accuracy of 1% at model-scale. However, the range of the non- dimensional flow angles the FRM exhibited was shown to be within that for a full-scale flood trajectory. Therefore, further tests have been proposed to increase the extent of the data in the future.

An integrated metagenomic and metabolite profiling study of hydrocarbon biodegradation and corrosion in navy ships

Naval vessels regularly mix fuel and seawater as ballast, a practice that might exacerbate fuel biodegradation and metal biocorrosion. To investigate, a metagenomic characterization and metabolite profiling of ballast from U.S. Navy vessels with residence times of 1-, ~20-, and 31 weeks was conducted and compared with the seawater used to fill the tanks. Aerobic Gammaproteobacteria differentially proliferated in the youngest ballast tank and aerobic-specific hydrocarbon degradation genes were quantitatively more important compared to seawater or the other ballast tanks. In contrast, the anaerobic Deltaproteobacteria dominated in the eldest ballast fluid with anaerobic-specific hydrocarbon activation genes being far more prominent. Gene activity was corroborated by detection of diagnostic metabolites and corrosion was evident by elevated levels of Fe, Mn, Ni and Cu in all ballast samples relative to seawater. The findings argue that marine microbial communities rapidly shift from aerobic to anaerobic hydrocarbonoclastic-dominated assemblages that accelerate fuel and infrastructure deterioration.