Indian Register of Shipping

Abstract The global shipping industry is at a critical stage as it faces an unprecedented challenge in responsibly recycling large vessels exceeding 50,000 gross tonnages (GT). These huge ships, including post-Panamax, Suezmax, & ultra-large container vessels, along with Very Large Crude Carriers (VLCCs). Ultra Large Crude Carriers (ULCCs), and Ultra Large Gas Carriers (ULGCs) represent an integral part of the international maritime trade yet pose unique complexities when they reach the end-of-useful-life phase. One of the biggest challenges in front of the industry is that there aren't enough recycling facilities that can handle these huge ships safely and responsibly. Some of the other impending issues related to the recycling of these large vessels have been discussed in detail in this paper, including the regulatory landscape, infrastructural limitations (limited supply), environmental considerations, and economic feasibility. Large vessels require specialised shipbreaking facilities that demand substantial capital investment, mainly to accommodate such ships. Few critical infrastructural investments include dredging costs to comply with adequate draft depths of 8-10 meters, berth or drydock width of over 40 meters, and heavy-lift cranes capable of handling over 50-ton blocks. The challenge is further amplified considering that approximately 16,000 vessels (representing over 700 million deadweight tonnes - DWT) are expected to reach their end-of-life and require recycling over the next decade. This projection is nearly three times the ships recycled over the last 10 years. (MI News Network 2025) This paper evaluates the major challenges regarding the recycling of large ships, assessing the regulatory landscape with special emphasis on the IMO's Hong Kong International Convention (HKC) ratification, market dynamics, infrastructure constraints, and industry stakeholder responsibility. The analysis addresses the urgent need for green ship recycling that balances environmental protection, worker safety, and financial viability while meeting the growing demand for responsible ship recycling. Some emphasis has also been placed on the underlying opportunity for a circular economy and the potential supply of green steel.

Tuberculosis (TB) is a contagious disease caused by the bacterium Mycobacterium tuberculosis, which most often affects the lungs, specifically pulmonary tuberculosis. One of the leading opportunistic diseases globally, affecting one-third population and resulting in approximately 1.5 million deaths annually. A weakened immune system against mycobacterial diseases has contributed to over 1.1 million people being co-infected with other life-threatening diseases, such as Human Immunodeficiency Virus (HIV). Abundant research highlighted the biotherapeutic potential of naturally occurring compounds against mycobacterial disorder. The increasing cases of MDR/XDR-TB are mainly derived from tuberculosis, coupled with the emergence of extensively drug-resistant (XDR) and multidrug resistance (MDR) strains, have made treatment more challenging. The condition emphasized the crucial requirement for novel plant-derived anti-TB medications. The persistence and latency of M. tuberculosis, along with drug resistance, have made tuberculosis treatment increasingly challenging. This review aims to comprehensively examine tuberculosis disease including current standard treatment, promising new drugs under development and the potential of medicinal plants and their bioactive compounds as alternative or supplementary therapies to combat mycobacterial infections, specifically focusing on the potential of plant-derived metabolites to act as effective antimycobaterial agents. It specifically highlights the role of plant-derived metabolites as effective antimycobacterial agents.

Computations for air gap response of a semisubmersible platform based on a 3D numerical wave tank approach are presented. The developed method is in time domain and can consider nonlinearities associated with incident wave and hydrostatic forces exactly in determining the body response, but the interaction hydrodynamics of radiation and diffraction are based on simplified linearization assumptions. The incident wave can be defined by any suitable wave theory and here defined by a fully nonlinear numerical wave model. After verifying the present computations results in its degenerated linearized version against the usual linear 3D Green function–based frequency-domain results for air gap predictions, systematic comparative studies are undertaken between linear and the approximate nonlinear solutions. It is found that nonlinear computations can yield considerably conservative predictions as compared to fully linear calculations, amounting to a difference of up to 30%–40% in the minimum air gap in steep ambient incident waves at high and moderate frequencies.

In urea plant equipment, particularly those operating in the synthesis cycle, anti-corrosive liner plates are usually applied to the pressure retaining carbon steel vessel walls. Even with the correct material selection, controlled fabrication methods and maintenance, the risk of highly corrosive urea-carbamate solution leaking through these liners always exists in these equipment which might eventually damage the carbon steel walls. Existing designs of these equipment utilizes “weep holes” to reveal such leakages. Various designs exist, but in general these weep holes are 15–20mm dia. plain openings in the vessel walls connecting the space between the liner and the vessel wall to the outside atmosphere or the leak-detect apparatus. These equipment operate at high pressures and temperatures and therefore ASME Section VIII Division 2 is normally the preferred design and construction Code. This Code, earlier to the publication of its Edition 2007, had provisions in it to exempt openings not exceeding certain diameters, from any reinforcement calculations. Traditionally, equipment designers have been applying this clause to seek the exemption of these weep holes from any further calculations. However, starting with Edition 2007, this Code did away with such exemptions and has made it mandatory to assess openings of all sizes, particularly if they are in the monobloc vessels. Weep holes are no exception. This paper discusses how the assessment of these weep holes in cylindrical shells can be carried out by applying the “Elastic-Plastic Stress Analysis Method” stipulated in Para. 5.2.4 & 5.3.3 of the ASME Section VIII Division 2 Code. This paper also provides the basis for recommending this method. In the application of this method, the subject is approached as a “shell with opening” and not as conventional “nozzle opening in the shell”.

Various methods have been in use for the determination of stresses at the nozzle-shell junction due to external loads and moments. Some methods evaluate stress in the cylindrical or spherical shell (e.g. WRC 107 now WRC 537) while others evaluate stresses in cylindrical shells and nozzles (e.g. WRC 297). ASME Section VIII Division. 2 specifies use of WRC 107/WRC 297 or Finite Element Analysis (FEA) for determination of stresses at shell-nozzle junctions with external loads and moments on the nozzle. Each method could yield a different result for the same loading condition and geometry and this has been recognized in comparisons made in WRC 297 with WRC 107 and FEA. Further, customized FEA software are also available for this analysis. There still seems to be some confusion in users of these methods regarding selection of method for optimization of design. Users not familiar with Finite Element Method prefer to use calculations based on WRC 107/297. Hang-Sung Lee, et.al. have recently (PVP 2011 – 57407) analyzed nozzle shell junctions using the Finite Element Method, compared their results with calculations to WRC 297 and made recommendations. The work presented in this paper is not an attempt to compare individual stresses obtained by classical versus analytical methods. Instead, an attempt has been made to consolidate the results obtained by the various methods into charts to enable a user to make a preliminary assessment to ascertain under what geometrical conditions the calculations made by each of the above methods would result in overall Code acceptable stresses without the results being either overly conservative or un-conservative. This is particularly relevant to the geometries which use the graphs and charts which have been extrapolated without rigorous theoretical background in the WRC Bulletin 537. The Finite Element Method has been used as the referee method.

Over the years many methods are evolved for computing ship motions and loads, i.e. seakeeping analysis. All of these methods are known as potential flow methods where fluid is assumed to be irrotational. In these methods velocity vector is represented as a gradient of scalar potential phi (φ) known as velocity potential. One of the oldest methods is strip theory method where ship is descretized into number of 2D strips. Other methods are panel methods where entire hull is descretized into number of panels. These are also known as Green’s function methods. Various formulations of Green’s function do exist. In a recent development Green’s function methods are extended to Rankine Panel method (RPM) where free surface in the vicinity of vessel is panelized for computations. In RPM Green’s function computations are made easy. Again these methods are divided into frequency domain and time domain. Time domain methods take into account various nonlinearities which generally cannot be handled by frequency domain methods. For zero and non-zero forward speed of the vessel different formulations exist. All these methods have their own advantages and disadvantages. Hence, it is very important in the initial design stage to decide on method of seakeeping analysis. Here an attempt is made to compare the results of seakeeping analysis using various tools based on various seakeeping methods.

Fatigue is a phenomenon, which needs to be considered in the present day’s vessel design. The welded joints are particularly affected by the fatigue damage due to high stress concentrations caused by the metallurgical discontinuities present in the weld. For oil tankers and bulk carriers adequate guidelines for the fatigue strength assessment have been established by the classification societies. But for navy vessel, like offshore patrol vessel, the design guidelines for the fatigue strength analysis are not widely available. In the present paper, an attempt has been made to calculate the fatigue life of offshore patrol vessel (OPV). In general five stages of work is involved in calculating fatigue life of any ship structure. These are, load calculation, nominal and hot spot stress computation, long-term stress distribution, selection of S-N curve and the fatigue damage calculation. In the present study, the wave loads are obtained by the rule based estimation. The finite element analysis with the submodeling approach has been used to get the hot spot stress at critical locations. The two-parameter Weibull curve has been used to get the long-term distribution of stress. And at the end, the fatigue damage and the fatigue life have been computed using the Palmgren-Miner linear cumulative damage theory at the critical locations of the vessel.