Safe Integrity Research Articles

Numerical simulation of the impact of casing on the buried metal pipeline cathodic protection potential

Abstract Metal casings shield the cathodic protection current and detection signals of buried metal pipelines, making the corrosion protection and detection technology of pipelines at the casing one of the challenges for safe operation and integrity evaluation of pipelines. This paper uses the primary current distribution physics interface in the COMSOL Multiphysic simulation software to study the effects of the coating quality of the casing and pipeline, the installation of sacrificial anodes in the casing, the conductivity of the electrolyte, and defects in the pipeline coating in the casing on the pipeline potential. The influence of distribution. The results show that: The coating quality of the outer surface of the casing and the pipe inside the casing has a great influence on the cathodic protection potential of the pipeline. The better the coating quality, the more negative the cathodic protection potential is, and the less cathodic protection current required by the pipeline, so the power consumption of the forced current law is reduced, and the service life of the sacrificial anode is longer. Installing sacrificial anodes in the casing has a positive effect on the cathodic protection of this special pipe section. The conductivity of the electrolyte in the casing has a certain impact on the cathodic protection potential of the pipeline. When the conductivity of the internal electrolyte is greater, the protective potential of the pipeline becomes more negative. However, impurities such as soil, groundwater, and silt make the pipeline more susceptible to corrosion, so keeping the annular space relatively dry is an important prerequisite for anti-corrosion. When there is a coating defect on the inner and outer pipes of the casing, the potential at the damaged point will have a potential peak. The larger the potential peak difference, the more serious the coating defect is.

Attention-ResNet-AR-LSTM: An intelligent method for PCCP deformation prediction via structure monitoring based on distributed fiber optics

The prestressed concrete cylinder pipeline (PCCP) is extensively employed in long water diversion projects due to its commendable performance and cost-effectiveness. Nonetheless, the continuous application of load on the prestressed steel wire during the production phase can amplify the creep deformation in both the concrete and steel cylinder of the PCCP. This phenomenon may potentially lead to the development of cracks at the socket end of the PCCP, posing a significant risk to the safe operational integrity of the pipeline. In this study, the strain development prediction model of PCCP concrete and steel cylinder is constructed through the integration of ResNet, AR, and LSTM modules, and the attention mechanism is also applied. Based on the prototype test of PCCP structure monitoring, the strain values of steel cylinder and inner concrete were recorded by pre-set distributed fiber optic sensors on the 1st, 3rd, 5th, 7th, 9th, 11th, 13th, 15th, 17th, and 20th day after the production of PCCP. Then an Attention-ResNet-AR-LSTM model is constructed to predict the strain development of PCCP steel cylinder and concrete based on monitoring data on the 20th day using the data of 1st to 11th days. For steel cylinder and concrete structures, the R2 of the proposed models is above 98%, indicating that the proposed models can capture the strain changes of different structures well. Compared with other deep models and machine learning models, the proposed model also shows a significant predictive ability. This model introduces a novel approach to forecast strain evolution during the manufacturing of PCCP.

Finite element analysis and experimental validation of the failure characteristic of pressurized cylinder

PurposeThe high-pressure accumulator has been widely used in the hydraulic system. Failure pressure prediction is crucial for the safe design and integrity assessment of the accumulators. The purpose of this study is to accurately predict the burst pressure and location for the accumulator shells due to internal pressure.Design/methodology/approachThis study concentrates the non-linear finite element simulation procedure, which allows determination of the burst pressure and crack location using extensive plastic straining criterion. Meanwhile, the full-scale hydraulic burst test and the analytical solution are conducted for comparative analysis.FindingsA good agreement between predicted and measured the burst pressure that was obtained, and the predicted failure point coincided very well with the fracture location of the actual shell very well. Meanwhile, the burst pressure of the shells increases with wall thickness, independent of the length. It can be said that the non-linear finite element method can be employed to predict the failure behavior of a cylindrical shell with sufficient accuracy.Originality/valueThis paper can provide a designer with additional insight into how the pressurized hollow cylinder might fail, and the failure pressure has been predicted accurately with a minimum error below 1%, comparing the numerical results with experimental data.

Welding Joint Made of Two Different Austenitic Materials

Using austenitic steel in welding structures requires both destructive and non-destructive testing (NDT) to approve the use of intended welding specification, but also testing of material properties, even if they are guaranteed by manufacturer. In this particular case, X2CrNiMo17-12-2 (commercial trademark AISI 316L) is the material that has to be partly replaced by NiCr21Mo (commercial trademark Incoloy 825) in a piece of process equipment exposed to elevated temperature and highly corrosive environment. This research presents an investigation of overmatching V groove welded joint made of these two austenitic steels. Due to materials properties and specific application conditions, low heat input TIG welding was utilized. Mechanical properties of welded joint have been examined to check criteria which guarantees safe work and integrity of welded components. Chemical composition of used filler material was close to the one of NiCr21Mo alloy, providing weld overmatching, which needs to be checked as well. Mechanical testing (tensile, bending, impact, hardness), macro-and microstructure analysis provided detailed insight into welded joint characteristics and a ground for further investigation concerning heterogeneous austenitic welded joint, taking into account overmatching effect.

A decision tree model for accurate prediction of sand erosion in elbow geometry

Erosion of piping components, e.g., elbows, is a hazardous phenomenon that frequently occurs due to sand flow with fluids during petroleum production. Early prediction of the sand's erosion rate (ER) is essential for ensuring a safe flow process and material integrity. Some models have been applied to determine the ER of the sand in the literature. However, these models have been created based on specific data to require a model for application to wide-range data. Moreover, the previous models have not studied relationships between independent and dependent variables. Thus, this research aims to use machine learning techniques, namely linear regression and decision tree (DT), to predict the ER robustly. The optimum model, the DT model, was evaluated using various trend analysis and statistical error analyses (SEA) techniques, namely the correlation coefficient (R). The evaluation results proved proper physical behavior for all independent variables, along with high accuracy and the DT model robustness. The proposed DT method can accurately predict the ER with R of 0.9975, 0.9911, 0.9761, and 0.9908, AAPRE of 5.0%, 6.27%, 6.26%, and 5.5%, RMSE of 2.492E-05, 6.189E-05, 9.310E-05, and 5.339E-05, and STD of 13.44, 6.66, 8.01, and 11.44 for the training, validation, testing, and whole datasets, respectively. Hence, this study delivers an effective, robust, accurate, and fast prediction tool for ER determination, significantly saving the petroleum industry's cost and time.

Cybersecurity in Unmanned Aerial Vehicles: a Review

Abstract Context With the rapid advancement of unmanned aerial vehicle (UAV) technology, ensuring these autonomous systems’ security and integrity is paramount. UAVs are susceptible to cyberattacks, including unauthorized access, control, or manipulation of their systems, leading to potential safety risks or unauthorized data retrieval. Moreover, UAVs encounter limited computing resources, wireless communication and physical vulnerabilities, evolving threats and techniques, necessity for compliance with regulations, and human factors. Methods This review explores the potential cyberthreats faced by UAVs, including hacking, spoofing, and data breaches, and highlights the critical need for robust security measures. It examines various strategies and techniques used to protect UAVs from cyberattacks, e.g., encryption, authentication, and intrusion detection systems using cyberthreat analysis and assessment algorithms. The approach to assess the UAVs’ cybersecurity hazards included STRIDE (a model for identifying computer security-related threats) connected with the threats considered. Findings Emphasis was laid on the evaluation highly depending on the accuracy of UAV mission definition, potential intruders, and social and other human-related situations. The review discovered that most studies focused on possible intruders’ portraits, which can be crucial when conducting a cybersecurity assessment. Based on a review, future research directions to mitigate cybersecurity risks are presented. Significance Protecting UAVs from cyberthreats ensures safe operations and data integrity and preserves public trust in autonomous systems.

Failure Mode and the Prevention and Control Technology of Buried PE Pipeline in Service: State of the Art and Perspectives

Material defects and external environmental factors increase the engineering safety risks of buried PE pipelines in service. This paper mainly reviews the failure mode and the prevention and control technology of buried PE pipelines in service, as well as comparative failure characteristics between the buried PE and steel pipelines. The main failure factors of buried PE pipelines can be divided into four levels: the first level is third‐party damage; the second level includes three failure factors, i.e., surface subsidence, joint failure, and aging failure; the third level consists of pipe piercing, crack development, and pipeline defect; the fourth level is a corrosion failure. Besides, steel and PE pipelines have various physical and mechanical properties, which lead to a significant difference in the service performance and degradation mechanism in practice. For instance, corrosion and welded joint leakage are the two common problems in steel pipelines during the service period, while PE pipelines have excellent corrosion resistance. Additionally, in order to ensure and maintain the long‐term operations of PE pipelines, it is of great significance to develop and promote nonexcavation technologies of construction, renewal, and repair for natural gas‐buried PE pipelines. Furthermore, based on the above studies, some further research studies on buried PE pipelines in service are suggested and discussed, e.g., (a) the service performance and degradation mechanism of buried PE pipelines in complicated environmental conditions, (b) the interaction mechanism among the engineering structure, PE pipelines, and geological environment, as well as PE pipeline geological soils coupled in multiple physical fields, and (c) the combinations of the traditional engineering risk assessment method and the numerical analysis method considering the interaction between the PE pipeline and geological environment. The results could be helpful for a better understanding of the operation conditions of buried PE pipelines, and it is also hoped that this study could provide guidance for the safe operation, maintenance, and integrity management of buried PE pipelines.

Experimental research on the mechanisms of condensation induced water hammer in a natural circulation system

Natural circulation systems (NCSs) are extensively applied in nuclear power plants because of their simplicity and inherent safety features. For some passive natural circulation systems in floating nuclear power plants (FNPPs), the ocean is commonly used as the heat sink. Condensation induced water hammer (CIWH) events may appear as the steam directly contacts the subcooled seawater, which seriously threatens the safe operation and integrity of the NCSs. Nevertheless, the research on the formation mechanisms of CIWH is insufficient, especially in NCSs. In this paper, the characteristics of flow rate and fluid temperature are emphatically analyzed. Then the formation types of CIWH are identified by visualization method. The experimental results reveal that due to the different size and formation periods of steam slugs, the flow rate presents continuous and irregular oscillation. The fluid in the horizontal hot pipe section near the water tank is always subcooled due to the reverse flow phenomenon. Moreover, the transition from stratified flow to slug flow can cause CIWH and enhance flow instability. Three types of formation mechanisms of CIWH, including the Kelvin-Helmholtz instability, the interaction of solitary wave and interface wave, and the pressure wave induced by CIWH, are obtained by identifying 67 CIWH events.

Post-test analysis of Series D experiments in LIFUS5/Mod3 facility for SIMMER code validation of WCLL-BB In-box LOCA

The In-box LOCA for the WCLL-BB is recognized as a Design Basis Accident (DBA) and is of substantial interest to the DEMOnestration reactor design, therefore, the transient response of such an accident must be carefully investigated and addressed to ensure the safe operation and integrity of the whole system. In this way, the LIFUS5/Mod3 test facility (constructed at ENEA Brasimone Research Center) has been upgraded in the period 2018–2020 to perform a series of tests. The first set of the tests were named Series D, which are characterized by injecting specified amounts of pressurized water into the Lithium lead liquid bulk. The experimental campaign aimed at validating and qualifying the SIMMER-III code as a reliable numerical tool for the safety studies of the WCLL BB.In parallel with performing the tests, SIMMER-III Verification and Validation (V&V) was conducted according to a standard code validation procedure. SIMMER-III is a two-dimensional, multiphase, multicomponent, Eulerian, fluid-dynamics code which was firstly developed at the Japan Nuclear Cycle Development Institute (JNC). An adopted version of the original SIMMER-III code so-called Ver.3 F Mod.0.1 (which was developed at University of Pisa), was employed for the analyses. The V&V activity was successfully completed and documented as the technical reports within the past numerical analytical and experimental activities for the first three tests (D1.1, D1.2 and D1.5).In this article, the experimental data of the Tests D1.1, D1.2 and D1.5 are used for the SIMMER-III code results comparison. A qualitative analysis of the results obtained is reported according to the time trends for the most relevant parameters. The results show that the SIMMER-III code acceptably predicts the transient and the accuracies of the relevant test parameters are in agreement with the acquired experimental signals. Although that the primarily validation results are highly promising but further code assessment, development and validation are essential to approach such a qualified system code, which is suitable for fusion safety applications. The present validation work has been successfully followed by its ongoing experimental and numerical activities as a multilateral EUROfusion project.

Risks at the Intersection of Research and Oncology Nursing

To describe the increasing complexity and scope of clinical trials research, convergent research, and the clinical nurse roles and responsibilities to ensure safe patient care and study data integrity. Textbooks, journal publications, federal regulations, US Food and Drug Administration documents, clinical practice guidelines. The immune system, genetics, and molecular pathology are not new in the context of oncology treatments. The reliability and clinical validation of in vitro diagnostic medical devices is, however, becoming increasingly more important in the development of marker driven targeted therapies, immunotherapy, and adoptive T-cell transfer. Protecting patients and preserving the integrity of clinical trials is of utmost importance. The role and scope of oncology and research nurses will intersect and shift as clinical care continues to involve high-acuity patients who participate in complex in vitro diagnostic and therapeutics clinical trials. The expertise of oncology nurses may vary in skills and knowledge domain; however, all scopes of practice are underpinned by the nursing code of ethics to ensure accountability for all aspects of patient care.

An overview of application of micromechanical models in ductile fracture analysis of welded joints

Fracture of welded joints has been an important research and industrial topic for a long time, having in mind the key role of welded joints in ensuring the safe operation and integrity of welded structures. This work contains an overview of application of micromechanical models to ductile fracture of welded joints. The main benefit of these models, in comparison with the classical fracture mechanics approach, is consideration of the local quantities (stress and strain) in prediction of damage development. The damage is quantified through the value of the damage parameter, which is typically related to the void nucleation, growth and coalescence for ductile fracture of metallic materials, i.e. the description of the material can be related to the actual material behaviour during fracture. Most of the presented studies, including those published by the present authors, are performed on steel as the base material, and the rest deal with aluminium alloys.

Effects of proof tests on the safety performance of safety-instrumented systems

The imperfection in the values of the average probability of failure on demand (PFDavg) creates uncertainty about the effectiveness of safety-instrumented system (SIS). To overcome this problem, many parameters such as dangerous failures, common cause failures, diagnostic coverage rate and proof tests are taken into consideration. In order to emphasise the importance of the proof tests and show their effects on the safety performance of the SIS, a new analytical formula is developed in this study. The impact of these tests on the SIS's allocation of the safe integrity level (SIL) is shown through the results obtained in the present research.

Research on Safe Communication Architecture for Real-Time Ethernet Distributed Control System

With the penetration of real-time Ethernet in industry, the mechanism of CANopen protocol based on real-time Ethernet (COE) has been widely used in various distributed control systems. However, due to some defects of the existing COE mechanism, the functional integrity and security for communication could not be guaranteed. Thus, Safe-COE architecture is designed in this paper. First, safe communication problems in systems are analyzed. Then, based on the Security and Safety Modeling (SESAMO) method, safe building blocks for communication are designed and combining these building blocks with Safe-COE mechanism, a kind of Safe-COE communication architecture is proposed. Finally, communication performance is tested based on this architecture. The results show that based on the general Ethernet MII bus interface, the minimum communication cycle could reach 125 μs , and the minimum synchronization accuracy of peripherals control could be about 100 ns. Moreover, the formal modeling method is used to verify the safe integrity of this architecture. The results show that the architecture could meet related safe requirements of attack protection, data validation, disconnect monitoring, and state switching. Currently, there is no safe communication architecture for a distributed control system that could fully meet related standards and consider both functional safety and information security. It could provide a theoretical basis and solution for safe communication in the distributed control system.

Employing exogenous melatonin applying confers chilling tolerance in tomato fruits by upregulating ZAT2/6/12 giving rise to promoting endogenous polyamines, proline, and nitric oxide accumulation by triggering arginine pathway activity

In the present study, the mechanisms employed by exogenous melatonin applying for conferring chilling tolerance in tomato fruits during storage at 4 °C for 28 days were investigated. Conferring chilling tolerance in tomato fruits in response to exogenous melatonin applying at 100 µM may arise from upregulating SlZAT2/6/12 giving rise to triggering CBF1 gene expression. Employing higher arginine pathway activity in tomato fruits by exogenous melatonin applying demonstrating by higher endogenous polyamines accumulation arising from higher ornithine decarboxylase (ODC) and arginine decarboxylase (ADC) genes expression and enzymes activity, higher endogenous proline accumulation arising from higher pyroline 5-carboxylate synthetase (P5CS) and ornithine aminotransferase (OAT) genes expression and enzymes activity accompanying by lower proline dehydrogenase (PDH) gene expression and enzyme activity and higher endogenous nitric oxide (NO) accumulation arising from higher nitric oxide synthase (NOS) gene expression and enzyme activity may be responsible for keeping safe membrane integrity.

Placing an Orientation Suture During an Elliptical Excision Procedure Is Simple, Efficient, Safe, and May Help Preserve Tissue Integrity

<p class=MsoNormalCxSpFirst style=margin-left:0in;mso-add-space:auto; text-align:justify;text-indent:0in;mso-list:l0 level1 lfo1> 1. Abstract <span style=font-size: 10.0pt>An elliptical skin excision is often performed to provide diagnostic information on managing cutaneous disorders. We propose a simple and safe modification of the standard technique by placing an orientation suture in the specimen before it is removed from the skin in order to provide traction and prevent structural damage to the tissue. <span style=font-size: 10.0pt>An elliptical skin excision is often performed as part of an incisional or excisional biopsy to provide diagnostic information for managing cutaneous disorders [1] . In addition to establishing or confirming a diagnosis, an elliptical skin excision can be used to evaluate the effectiveness of therapy, provide a specimen for histological assessment of margins, and offer a surgical cure for numerous cutaneous disorders [2] . <span style=font-size: 10.0pt>Commonly, an elliptical excision is performed after the surgical site has been marked, anesthetized, prepped, and draped [3]. In the standard procedure, lateral margins of the excision are made, the elliptical specimen is grasped at one of its poles with a pair of tissue forceps and the tissue is elevated. The surgeon then separates the specimen from underlying tissues along a horizontal, even plane using a scalpel or sharp tissue scissors [2] . A suture to remind the surgeon of the orientation is often placed after the specimen has been completely removed from the underlying tissue. The specimen is then transferred to the appropriate fixative container and subsequently submitted to pathology. <span style=font-size: 10.0pt>We propose a simple and safe modification of the standard technique by placing the orientation suture in the specimen before it is removed from the skin in order to provide traction during the removal process without compounding structural damage to the tissue.

Safe number and integrity of graphs

For a connected graph G=(V(G),E(G)), a non-empty subset S of V(G) is a safe set if, for every component C of G[S] and every component D of G−S, we have |V(C)|≥|V(D)| whenever there exists an edge of G between C and D. If G[S] is connected, then S is called a connected safe set. The safe numbers(G) of G is defined as s(G)≔min{|S|:S is a safe set of G}, and the connected safe numbercs(G) of G is defined as cs(G)≔min{|S|:S is a connected safe set of G}. The integrity of a graph G is defined as I(G)≔min{|S|+τ(G−S):S⊆V(G)}, where τ(G−S) is the order of the largest component of G−S.In this paper, we discuss a relationship between the (connected) safe number and the integrity in a connected graph.

Prevalence of tuberculous lesion in cattle slaughtered in Mubende district, Uganda

BackgroundThe aim of this study was to estimate the prevalence of gross pathology suggestive of bovine tuberculosis (TB-like lesions) and evaluate animal’s characteristics associated with the risk of having bovine TB-like lesions among cattle slaughtered in Mubende district in the Uganda cattle corridor.MethodWe conducted a cross sectional study in which 1,576 slaughtered cattle in Mubende district municipal abattoir underwent post-mortem inspection between August 2013 and January 2014. The presence of bovine TB-like lesions in addition to the animal’s sex, age, breed, and sub-county of origin prior to slaughter were recorded. Associations between the presence of bovine TB-like lesions and animal’s age, sex, breed, and sub-county of origin prior to slaughter were initially analysed using a univariable approach with the chi-square test, and subsequently with a multivariable logistic regression model to assess the combined impact of these animal characteristics with the risk of having a bovine TB-like lesion. Additionally, and as a secondary objective, tissue samples were collected from all carcases that had a bovine TB-like lesion and were processed using standard Mycobacterium culture and identification methods. The culture and acid fast positive samples were tested using Capilia TB-neo® assay to identify Mycobacterium tuberculosis complex (MTC).ResultsOf 1,576 carcasses inspected, 9.7% (153/1,576) had bovine TB-like lesions from which Mycobacterium spp and Mycobacterium Tuberculosis Complex (MTC) were isolated in 13 (8.4%) and 12 (7.8%) respectively. Bovine TB-like lesions were more likely to be found in females (OR = 1.49, OR 95% CI: 1.06–2.13) and in older cattle (OR = 2.5, 95% CI: 1.64–3.7). When compared to Ankole cattle, Cross breed (OR = 6.5, OR 95% CI: 3.37–12.7) and Zebu cattle (OR = 2.57, 95% CI: 1.78–3.72) had higher odds of having bovine TB-like lesions. Animals from Kasanda (OR = 2.5, 95% CI: 1.52–4.17) were more likely to have bovine TB-like lesions than cattle from Kasambya.ConclusionsThe findings of study reveals that approximately one in ten slaughtered cattle presents with gross pathology suggestive of bovine TB in Mubende district in the Uganda cattle corridor district, however, we isolated MTC in only 8.4% of these bovine TB-like lesions. Therefore, there is a need to understand the cause of all the other bovine TB-like lesions in order to safe guard diagnostic integrity of meat inspection in Uganda.

The competitive role of wear and RCF: Full scale experimental assessment of artificial and natural defects in railway wheel treads

Assessments of the severity of wheels tread defects under rolling contact fatigue conditions are in general very uncertain when based on theoretical concepts supported only by small scale material characterization and without the possibility of a full scale validation. In real service conditions, the tread surface and subsurface defects are subject to a number of variable mechanical loading conditions given by the combination of vertical and lateral loads and wheelset steering. The present paper describes some interesting experiences from recent RCF tests performed by Lucchini RS on its full scale roller rig (named “BU300”) on two very high speed railway wheelsets coming from revenue trafic. The test rig was used in order to reproduce running conditions very near to normal service conditions. A concept for test acceleration was applied: the ratio curve distance/straight distance was increased, since curves are more critical to RCF compared to straight running. Firstly, the scope of the test was to monitor the behavior of defects in order to evaluate the impact on the safe integrity and to reduce RCF damage by considering two different steel grades: ER8 (EN13262) and Superlos® developed by LucchiniRS. Secondly the results of the tests provided interesting information regarding rate of crack propagation.Depending on the crack depth from the tread surface and the wear rate obtained, an important basis for describing the competitive role of RCF and wear is offered. In addition some considerations on preventive wheel reprofiling (skimming) strategies are proposed that can reduce RCF impact on wheel life. The accumulated results are also valuable since they can be used as a basis for the validation of RCF models. Finally this work confirms the ability of the roller rig to reproduce equivalent service running conditions that can generate RCF cracks similar to those found in service.

Improving digital image watermarking by means of optimal channel selection

Supporting safe and resilient authentication and integrity of digital images is of critical importance in a time of enormous creation and sharing of these contents. This paper presents an improved digital image watermarking model based on a coefficient quantization technique that intelligently encodes the owner’s information for each color channel to improve imperceptibility and robustness of the hidden information. Concretely, a novel color channel selection mechanism automatically selects the optimal HL4 and LH4 wavelet coefficient blocks for embedding binary bits by adjusting block differences, calculated between LH and HL coefficients of the host image. The channel selection aims to minimize the visual difference between the original image and the embedded image. On the other hand, the strength of the watermark is controlled by a factor to achieve an acceptable tradeoff between robustness and imperceptibility. The arrangement of the watermark pixels before shuffling and the channel into which each pixel is embedded is ciphered in an associated key. This key is utterly required to recover the original watermark, which is extracted through an adaptive clustering thresholding mechanism based on the Otsu’s algorithm. Benchmark results prove the model to support imperceptible watermarking as well as high robustness against common attacks in image processing, including geometric, non-geometric transformations, and lossy JPEG compression. The proposed method enhances more than 4 dB in the watermarked image quality and significantly reduces Bit Error Rate in the comparison of state-of-the-art approaches.

Ship dynamic stability assessment based on realistic wave group excitations

Ship propensity for stability failure in irregular beam seas is addressed. A new method, based on the combination of the Karhunen–Loève theorem with the theory of Markov processes, is employed in order to construct realistic wave groups of varying heights and periods. The focus is set on waveforms with high probability of occurrence, given a sea-state. These waveforms are then applied, as beam-sea excitation, to a modern container vessel. Safe basin integrity diagrams and transient capsize diagrams are produced through short numerical simulations. For comparison purposes, alternative forms of excitation, such as wave groups of varying heights but fixed periods; and regular wave groups of fixed heights and periods, are also considered. Differences in the system's transient response, specifically on the integrity of its safe basin and on the transient capsize diagram, are discussed. The proposed method advances the so called “critical wave groups method” and it can be used for a swift assessment of ship stability.