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Maritime Blogs

Blogs by Maritime Community

<div class="cStream-Attachment-inner-custom"><div><div style="float:left; width: 130px;margin-right: 12px;float: left;color: transparent;"><a href="/…; target="_blank"><img… style="width: 200px;height: auto;" /></div><div style="width: 75%;float: left;"><div style="font-weight: bold;font-size: 18px;margin: 0 auto 2px auto;"><a href="/…; title="…; target="_blank">6 Indian sailors killed, 6 missing in Kerch strait ship accident</div><div style="margin: 0 auto 8px auto;">Two fuel ships carrying Indian and Turkish crew members caught fire in Kerch Strait</div></div></div></div>

What is the P&I Correspondent

The correspondent acts as the P&I Club's local representative and his principal function is to deal with the various problems which can confront the shipowner member when his ship is within the jurisdiction in which the correspondent is located. Whilst the role of the correspondent is not that of an agent he is expected to stand in the shoes of the P&I Club insofar as the ship's master and the P&I Club member is concerned. The correspondent will handle claims and solve problems, whether or not they will give rise to a claim covered under the P&I Club rules.

So what the special skill set is required for being a P&I Correspondent

In order to handle above mentioned matters he may need to enlist the assistance of local experts such as surveyors, lawyers and other professionals. So definitely networking within the local Maritime community is a must skill.

This entails the necessity for the correspondent to be familiar with the expertise that is available in his area and to provide proper instructions in order to retain control over the handling of the matter.Many of the problems that arise involve local authorities such as the harbour master, customs and immigration officers with whom the correspondent should have a good working relationship.

Additionally, the P&I Club will expect the correspondent to be the "eyes and ears" of the Club and to provide relevant information regarding any changes to local laws or statutory requirements and to advise on any claims trends of which the correspondent becomes aware.

What more is expected from the correspondent by his P&I Club

Loss prevention is an important part of everyday life within the P & I Club and the correspondent has an invaluable part to play in advising the Club on such issues. A major marine casualty is obviously of prime concern to both the member and the Club and speed of response is crucial to effective problem solving. Whilst owners and ships are now obliged to have disaster or major casualty response plans, the Club and its correspondents should be similarly equipped. Every correspondent office should be in a position to respond effectively and efficiently to any casualty which may arise on its shores.

This might consist of a tanker grounding or perhaps passengers from a cruise liner who need to be evacuated and found accommodation ashore prior to repatriation. Contingency plans for such events are essential and the Club would expect the correspondent to have such plans well documented.

In addition to the expectations of the Club, on many occasions the correspondent receives instructions directly from a Club member to provide assistance in all manner of matters which may, or may not, be of a P&I nature. Because correspondents are listed within the Club handbook, members will turn to them to assist in dealing with their local problems. If those problems are not of a P&I nature, fees and expenses will be debited directly to the Club member since they will not be recoverable from the Club.

Potential risks in the Job of an Correspondent of P&I Club

A P&I Club correspondent is of course potentially liable for claims which might arise as a result of any negligence or breach of duty which causes a loss to the Club or its members. Similarly he is also vulnerable to claims for breach of warranty of authority. One such case occurred recently when a P&I Club correspondent was requested to attend on board a ship to survey a cargo of 2000 metric tonnes of bulk fertiliser, which had been contaminated by residues from a previous cargo. The correspondent and the cargo interests reached agreement on a depreciation allowance of US$ 22 per tonne. The correspondent, after several telephone conversations with the P&I Club, obtained verbal agreement to the compromise, and made a written offer of settlement to the cargo interests, which was accepted.

When the cargo interests submitted their claim for US$ 44,000 to the Club, the Club refused to pay alleging that the correspondent had no authority to make the offer of settlement. Not unnaturally, the consignees sued the P&I Club; they also sued the shipowner and the correspondent. Lawyers were appointed to defend the correspondent.Ultimately the court found, with the aid of contemporaneous notes, that the correspondent did in fact have authority from the P&I Club. However, the case illustrates how important it is to have written authority. P & I Club correspondents can also be vulnerable to overlooking time limits and extensions. In one case a correspondent, acting for charterers' liability insurers, failed to appreciate that a letter of guarantee had expired. Although the correspondent had obtained the necessary time extensions from the shipowner, the ship had been sold and the owner was bankrupt. The guarantors were approached for an extension but refused on the grounds that their letter of guarantee had been issued in exchange for a counter guarantee from the shipowner which had also expired.

The role of P & I Club correspondents has essentially remained the same ever since they were first appointed. However, it is certainly the case that with today's advances in technology and communications they will be expected to provide an efficient and speedy service. At the same time they must minimise the cost of dealing with claims on behalf of the Club for the benefit of members overall.

Hits: 1374

Safety is a perceived concept which determines to what extent the management, engineering and operation of a system are free from danger to life, property and the environment.’

The objective of this forum is to start discussion on the tools and techniques that are utilized in Maritime Industry, in the process of carrying out a risk analysis and assessment.

 The following five techniques are usually used in various Ship-management companies as tools for ship-board risk analysis:

  •  Preliminary Hazard Analysis (PHA)
  • Hazard and Operability Studies (HAZOP)
  • Failure Mode, Effect and Criticality Analysis (FMECA)
  • Fault Tree Analysis (FTA)
  • Event Tree Analysis (ETA)

These techniques are utilized in relation to different aspects of risk analysis.

 The Preliminary Hazard Analysis (PHA) methodology is used to identify possible hazards, i.e. possible events and conditions that may result in any severity.

 A more extensive hazard identification method is Hazard and Operability Studies (HAZOP), which searches much more systematically for system deviations that may have harmful consequences.

The Failure Mode, Effect and Criticality Analysis (FMECA) can be used to identify equipment/system failures and assess them in terms of causes, effects and criticality. The application of an FMECA gives enhanced system understanding as well as an improved basis for quantitative analysis.

 Fault Tree Analysis (FTA) and Event Tree Analysis (ETA) are the most commonly used methods in terms of establishing the probability of occurrence and the severity of the consequences, for hazards in the context of risk analysis.

Risk analysis involves analysing a system in terms of its risks. As pointed out by various experts that the concept of risk is central to any discussion of safety. There is a steadily increasing focus on safety in all aspects of life, and in a maritime context risk analysis is nowadays a relatively common investigative and diagnostic element in reviewing system performance with the objective of identifying areas for improvement.

Risk and Safety

Risks and safety are closely linked. But how should we understand the term ‘risk’?

Risk is a parameter used to judge the significance of hazards in relation to safety, and  hazards are the possible events and conditions that may result in severity.

More risky a job is, and then less safe it would be. Mathematically Safety can be expressed as

Safety (S)≈ 1/ Risk (R)

 In other words it can be said that more safety measures are required to reduce the risk of hazards from the job concerned.

Risk (R) is normally evaluated as a function of the severity of the possible consequences (C) for a hazard, and the probability of occurrence (P) for that particular hazard:

 R= f (C,P)

Both the possible consequences (C) and the probability of occurrence (P) are functions  of various parameters, such as human factors, operational factors, management factors, engineering factors and time. It is normal to use the simplest possible relation between C and P, i.e. the product of the two, to calculate the risk (R):


Given this simple equation, we can better understand risk as a concept. For example, a high consequence (C) and a high probability of occurrence (P) for a certain given hazard mean that the risk is high, which will often be considered as intolerable from a safety perspective.

On the other hand, a low consequence (C) and a low probability (P) represent a low risk level. A low level of risk will normally be perceived as tolerable in a safety context, but may even be negligible if it is really low. The risk level that results from a high consequence and a low probability, or vice versa, will often be tolerable, but may in extreme cases be either negligible or intolerable.

The hazards needing special attention are those where both consequence and probability are significant. Given this knowledge, estimated risk of hazards can be used to make informed decisions in terms of improving safety.

Safety can be improved by reducing the risk, and risks can be reduced by reducing the severity of the consequences, reducing the probability of occurrence, or a combination of the two.

The Risk Analysis and Risk Assessment Process

Risk analysis is the process of calculating the risk for the identified hazards. Experts in this field of study often distinguish between risk analysis and risk assessment.

Risk assessment is the process of using the results obtained in the risk analysis (i.e. the risks of hazards) to improve the safety of a system through risk reduction. This involves the introduction of safety measures, also known as risk control options.

A principal diagram for the process of risk analysis and risk assessment is illustrated in Figure below.


  •         The first step in the process of risk analysis and risk assessment is to make a problem definition and system description, e.g. to define the vessel and/or the activity whose risks are to be  studied.  
  •           The second step of the process is to perform a hazard identification exercise where possible events and conditions that may result in any severity are identified.
  •            Once the hazards have been identified, third step would be to perform the risk analysis, which is the process of estimating the risks, either qualitatively or quantitatively. First a frequency analysis is used to estimate how likely it is that the different accidents/hazards will occur (i.e. the probability of occurrence). In parallel with the frequency analysis, consequence modelling evaluates the resulting consequences/effects if the hazards really occur. In a maritime context, an accident may have an effect on the vessel, its passengers and crew, the cargo, and/or the environment. When both the frequency and the consequence of each hazard have been estimated, they are combined to form a measures of overall risk.Risk may be presented in many different and complementary forms. Figure below illustrates the principle of risk presentation using a specific risk acceptance criterion. This figure also incorporates an assessment of the hazards in terms of risk, indicating whether they are intolerable (i.e. unacceptable), tolerable (i.e. acceptable) or negligible using continuous risk scales. Often, and particularly in qualitative risk analysis, discrete risk scales are used to assess the relative importance of hazards in terms of risks.
  • b2ap3_thumbnail_ship-board-2.png


  •     Fourth, In order to make intolerable risks tolerable, or to reduce the risks of hazards to as low a level as reasonably practicable (ALARP), the introduction of safety measures into the system will be necessary. A safety measure may, for example, be the construction and implementation of a marine evacuation system on board a ship.
  •     Finally, the cost-benefit analysis is a useful tool with regard to assessing safety measures because such an analysis evaluates whether the benefits of such measures justify the costs involved in implementing them. The benefits can be estimated by repeating the risk assessment process with the proposed safety measures in place, thereby introducing an iterative loop into the assessment process.  

Based on the process described above, conclusions may be drawn and recommendations proposed to the shipowner or ship operator, etc.

Each of the risk analysis techniques presented later in this forum can be utilized as tools within the risk analysis and assessment framework presented in the first figure. For example, both Preliminary Hazard Analysis (PHA) and Hazard and Operability Studies (HAZOP) can be used to identify possible hazards. Fault Tree Analysis (FTA) is useful in carrying out the frequency analysis, while Event Tree Analysis (ETA) is a common method used to study possible consequences of hazards.


System Description

The first step of a risk analysis will normally be to define and describe the system under consideration. This is a step of crucial importance since such a system description is the underlying basis for the risk analysis as a whole.

A system may be defined as an orderly arrangement of interrelated components that act and interact to perform a task or function in a particular environment and within a particular period of time. There are often several system levels, and complex systems are generally made up of subsystems in interrelation.

Which system levels need consideration depends on the characteristics of the analysis itself. For a risk analysis of a shuttle tanker operation one may, for example, consider the following system levels:

  •     Offshore loading operations
  • Tanker traffic and other ship movements along a coast
  • Tanker traffic in a specific fairway
  • Unloading operations
  • Onboard systems for cargo handling and treatment

It must also be recognized that risk analyses are performed on both existing and planned systems. In a maritime context the system description generally covers the following elements:

  • Geographical area: fairway, specific routes or harbours
  •  Environmental description: sea conditions, meteorological relations, visibility, etc.
  • Traffic: transport quantity, frequency/scale of operations
  • Vessels: number, capacities, sizes and technical descriptions
  • Other activities: surrounding traffic and activities that may introduce hazardous situations

Some typical problems often related to the system description step of the risk analysis are the uncertainty of future activities, the complexity of the system and the collection of useful and valid data. These problems introduce the need for simplifications and assumptions. It is very important to clarify, describe and evaluate these problems, because they must be considered when interpreting the results of the analysis.


Systems that are targeted for risk analyses are often quite complex, and the hazards facing the system may not therefore be completely obvious. Hence, after the system description is performed, the next task should be to identify possible hazards. The objective is to identify all possible events and conditions that may result in any severity or harm.

A systemized way to identify such hazards is to apply the Preliminary Hazard Analysis (PHA) methodology to be discussed now.


The principle (or objective) is to identify hazards that may develop into accidents. This is done by generating situations or processes that are not planned or meant to happen. It is important to identify the hazards as early as possible in the design process in order to implement corrective measures in the design. This is known as proactive risk management/reduction.


 In order to generate the hazardous situations or processes, deviations from the normal operation have to be considered. It may be difficult to get started with this exercise. Some deviations can, however, be established by making use of the cues below:

  •  More of . . . .
  • Less of . . .
  • Nothing of . . .
  • Part of . . .
  • Both . . . and . . .
  • Another than . . .
  • Opposite direction . . .
  • Later than . . .

Another approach is to identify parameters related to possible energy transfers. Accidents are often uncontrolled releases or transfers of energy, e.g. as in an uncontrolled fire. By identifying the energy sources, several hazardous events or processes can be established.


The PHA may seem like a very general and non-specific exercise and that is exactly what it is. To facilitate matters for the analyst, it is therefore important to systemize the deviations. There are several ways to do this systemization and the analyst should adapt a system suitable for the system and/or situation he or she is to analyse. Table below is a general table for identifying the hazards.




An oil tanker may introduce hazards to personnel, property and the environment. These hazards have to be identified as a basis for further risk analyses. Perform a Preliminary Hazard Analysis (PHA) for the tanker and sketch the accident development using the form presented in Table above.





Stability and buoyancy considerations are not treated here. Only kinetic energy and cargo energy are treated further.


Based on the energy considerations a PHA is performed for the tanker’s kinetic energy and cargo energy, as shown in the three tables below. These tables are not exhaustive. Can you, for example, find any other hazardous conditions relating to the kinetic energy of the oil tanker and the cargo’s energy? (Please use reply button  in the end of this forum post)













A Hazard and Operability Study, popularly known as HAZOP, is a more detailed and comprehensive hazard identification method than the PHA. The basic idea of HAZOP is to systematically search for deviations from the normal operation of the system that may have harmful consequences.


The principle (or objective) is to systematically examine the system part by part and then define the intention to each part. The intention is the way the system is expected to work. When the intentions are defined, possible deviations from the system’s intentions that may lead to hazardous situations can be identified. The use of so-called guiding words may assist the analyst in the identification of such deviations. For the analysis process to be successful, a team consisting of specialists in several fields should supervise the analysis.


The first task is to get an overview of the system using a system description as described before.

The system has to be divided into sections with independent intentions, and the intention of each part has to be carefully defined.

In a real system all sections or subsystems are dependent on each other to a greater or lesser extent, and these dependencies must be identified.

When the intentions for each part of the systems have been defined, the system description is complete. Then one can start identifying deviations for each part of the system.

Guidewords may assist the creativity of the analyst in order to establish as many deviations as possible, and these guidewords are applied one at a time.

When the deviations are identified the causes of the deviations can be found and the reasons for the occurrence of the causes can be identified.

The identification of causes results in greater/ increased problem understanding and based on this safety measures can be established.

These safety measures can be related to changes in processes, process parameters, design, routines, etc. The whole procedure is repeated for each part and section of the system as shown in Figure below.







The most important resource for a HAZOP analysis is a detailed system description as well as access to complete part intention knowledge. When these resources are established,a set of guidewords may assist the analyst in identifying deviations. These guidewords are presented in the table below.





The HAZOP procedure is further explained in the example below.






The mobility of a vessel is highly dependent on the propeller. If the propeller fails for some reason, the whole propulsion system and navigation system is put out of operation and the ship’s movement is out of control. It is therefore clear that the propeller is a critical component. As part of a HAZOP procedure the controllable pitch propeller (CPP) in is identified as a part with individual intention. Perform a single loop in the HAZOP procedure for the CPP.









The analysis is to emphasize loss of propeller function. The case of degraded operation is not considered here.




Definition of CPP intention: the propeller is to transform rotational energy, transmitted through the propeller shaft, into a pressure difference over the propeller blades. It is this pressure difference that accelerates and maintains the speed of the vessel. The controllable pitch’s intention is to optimize this energy transformation for various operational conditions.


Deviations and their causes and safety measures are identified in Tables below.







These tables are not exhaustive. Other deviations are possible, and to find these one must be creative and have a good understanding of the system.


The whole procedure should be repeated for all parts/subsystems of the propulsion and navigation system in a proper and comprehensive risk analysis.



The Failure Mode, Effect and Criticality Analysis (FMECA) is a systemized inductive method of determining equipment functions, functional failure modes, assessing the causes of such failures and their effects (or consequences), as well as their effect on production availability and reliability, safety, cost, quality, etc., on a component level.

The failure modes are normally and preferably analysed by the use of a standardized form that describes the failure, its causes and how it is detected, the various effects of the failure, as well as assessing important parameters such as failure rate, severity and criticality.

FMECA is a quantitative method. However, the original version of FMECA is a qualitative version where the measured criticality is excluded, i.e. Failure Mode Effect Analysis (FMEA). Therefore, FMECA is still often described as a qualitative method in the literature.


The simple standardized forms used in FMECA assist the analyst to review the possible failure modes and identify their effects. The FMECA method can be used systematically to identify the most effective risk-reducing measures, which assist the process of selecting suitable design alternatives in an early design phase.

As such the FMECA may be a valuable historical document for future design changes. The FMECA method is also used to form a basis for extensive quantitative reliability analyses with the objective of establishing sound maintenance strategies.

According to the Institution of Electrical Engineers (IEE), an FMECA should give an answer to some basic questions:

  • How can each part conceivably fail?
  • What mechanisms might produce these modes of failures?
  • What could the effects be if the failure did occur?
  • Is the failure detected?
  • What inherent provisions are provided in the design to compensate for the failure?


The first step of any risk analysis technique/method is the system description. In general the approach to FMECA is to perform the following six stages:

1. General description of the components.

2. Description of possible failures and failure modes.

3. Description of failure effects for each failure mode.

4. Grading the failure effects in terms of frequency, and severity of consequences, as well as specifying reliability data.

5. Specifying and assessing methods for the detection of failure modes.

6. Description of how unwanted failure effects can be reduced and eliminated.

The standardized form, aids the analyst’s approach to the method.


The failure modes are important parameters in the FMECA method. A failure mode can be defined as the effect by which a failure is observed on a failed component/item. There are in principle two types of failure modes which are characterized, respectively, as unwanted change of condition and demanded change not achieved.

 The quantitative part of the method is given by the use of standardized terms for failure frequencies and consequences. The terms describing the failure frequencies are presented below.




 The possible failure consequences are measured using the consequence classes are given below.




The loss of propulsion power directly results in a loss of the controlled mobility of the vessel. In the HAZOP of the propeller (see earlier example) it was assumed that the controllable pitch propeller (CPP) was a critical subsystem for the propulsion system. The criticality is, however, dependent on the failure consequence and the failure likelihood. Hence an FMECA of the whole propulsion system may be appropriate. Find the elements and descriptions to be filled in the FMECA form.

The FMECA form to be used is outlined below, though the content of the FMECA form is not exhaustive, especially in terms of failure causes.       



One of the most frequently used techniques in risk analyses is fault tree modelling. A fault tree analysis (FTA) can be used to identify the subsystems that are most critical for the operation of a given system, or to analyse how undesirable events occur.
The methodology was developed in 1962 by H. S. Watson at the Bell Telephone Laboratories during the development of the 'Minuteman' rocket's combustion chamber.


In the context of risk analyses the FTA method is used to analyse the way an unwanted event occurs, as well as its causes. By the use of a logical diagram the relationship between the causes of the event (e.g. the failure of a certain engine component) is visualized.

The method assumes binary operational modes, which means that an event either occurs or it does not (e.g. a failure alarm is given or not given). Hence, degraded operations or events are not analysed in fault trees.

The logical diagram used in an FTA consists of a set of gate symbols that describe the relationship between causes, and event symbols that characterize the causes.
The main principles of the fault tree analysis method are illustrated in Figure below.           





A fault tree can be analysed both qualitatively and quantitatively (which only, I will discuss here)



The fault tree is a visualization of the relationship between the failures of the analysed system as shown in above figure. This visualization is based on logical gates and symbols. The most common fault tree gate symbols and event symbols are presented in Tables below.






Qualitative Approach:




The first task of a fault tree analysis is to describe the system and its components/subsystems down to a sufficient level of detail, as explained before.


The next task is to construct the fault tree for a particular unwanted system failure using this system description. It is important that all the failures in the fault tree are given precise definitions.


The unwanted event or accident target for the analysis is referred to as the top event of the fault tree. The description of the top event should give answers to what the event is, where it occurs and when it occurs.


The occurrence of the top event is always dependent on two or more conditions or failures on a more detailed, i.e. lower, level. The main task in the FTA approach is to systematically define and structure the conditions or causes that directly lead to the top event. These events should be defined in such a way that only a limited number of causes lead to the top event.


Some literature recommends only defining two causes on the lower level at a time, but for some complex system failures this may not be realistic. The causes directly leading to the top event are at the second level in the fault tree.


 When the events are defined and structured, the next task is to assess the logical relation between the causes. Generally, either the top event is dependent on a simultaneous occurrence of these causes on the second level, or only one of the causes may lead to the top event. In the first case an AND gate is used and in the last case an OR gate is used(refer above figures).


 This procedure is then repeated to establish the logical relations between the causes on the third level of the fault tree, and so on. When the causes are described in such a detail that failure data (i.e. failure frequency) is available, the fault tree construction is finished and ready for quantitative analysis.


Minimal Cut Sets


The objective of qualitative FTA is to establish a general view and understanding of the fault tree construction. This can be achieved by establishing sets of events that have special characteristics. A set of basic events in the fault tree that triggers the top event by occurring simultaneously is called a cut set of the fault tree.


For illustration purposes, a simple fault tree for the top and unwanted event of an initiation of fire can be studied. Based on basic fire theory, a fire can occur only if three basic conditions are satisfied. These three basic conditions are the presence of a combustible material (e.g. wood, oil, etc.), oxygen, and an ignition source (e.g. flame, heat, friction, a spark, etc.). By distinguishing between combustible substances and gases, the following simplified fault tree can be constructed.


As shown in the fault tree, a fire can occur if the following set of causes are occurring: {Combustible substance present, Combustible gas present, Oxygen present, Heat or ignition source present}. This is a cut set for this fault tree because the simultaneous occurrence of the four causes results in the occurrence of the top event {Initiation of fire}.


A Minimal cut set is a set of causes where none of the included causes can be excluded without the causes losing their status as a cut set. Hence, the following two sets of causes are minimal cut sets: {Combustible material present, Oxygen present, Heat or ignition source present} and {Combustible gas present, Oxygen present, Heat or ignition source present}.


To establish the cut sets of a fault tree a systemized algorithm called MOCUS – Method of Obtaining Cut Sets – can be applied. The MOCUS algorithm is represented by four steps:


1. Consider the top event.


2. Replace the event with the events on the second level according to the following criteria: If the events on the lower level are connected through an OR gate they are written in separate rows. If they are connected through an AND gate they are written in separate columns.


3. Perform step 2 successively for all events that are not basic events.


4. When all events are basic events the events in each row constitute a cut set.


The fault tree as described in below figure can be used to illustrate the use of the MOCUS algorithm.





starting point of the algorithm is the top event according to step 1. In the fault tree in this is the following event:


                                                           {Initiation of fire}


This event is then replaced by the events on the lower level according to step 2. Because the events on the second level of the fault tree are connected through an AND gate, they replace the top event in three columns:


Cause 1

Combustible material present

Cause 4


The causes 1 and 4 are basic events and are not treated any further, according to step 2 in the MOCUS algorithm. However, the event of {Combustible material present} needs another loop of the MOCUS algorithm in order to complete the cut sets. Because the gate beyond this event is an OR gate, the causes on the third level are written in separate rows. Hence according to the MOCUS algorithm the cut sets after the second loop are:



Cause 1

Cause 2

Cause 4


Cause 1

Cause 3

Cause 4


According to step 4 of the algorithm, each row constitutes a cut set, and hence there are two cut sets, K1 and K2, for the fault tree.


Consequently, the general conditions for a fire, i.e. the event {Initiation of fire}, are satisfied when, for example, Cause 1, Cause 2 and Cause 4 occur simultaneously. Because none of the causes in the two cut sets can be removed without them losing their status as cut sets, both K1 and K2 are minimal.


Another important term in the fault tree terminology is the so-called path set. A path set assembles a set of causes with the characteristic that non-occurrence of the causes in the path sets ensure that the top event does not occur. For the fault tree in the above figure, the non-occurrence of Cause 1 {Heat or ignition source present} ensures that the top event does not occur. Hence Cause 1 is a path set.


Both the minimal path sets and the minimal cut sets give important information about the properties of the system. The number of elements in the minimal cut sets should be as large as possible to avoid triggering of the top event due to a few causes. Barriers may be built into the system to achieve this. The number of path sets should be large because this implies that the system is designed to have multiple ways of avoiding the top event.






The failure modes of a tanker’s main propulsion system have been established earlier in this forum using a FMECA analysis. The connections and relations between the failures are unknown, and must therefore be modelled in a fault tree. Construct a fault tree where the top event is loss of propulsion power for the tanker. Then perform a qualitative fault tree analysis using the algorithms and methods.




Qualitative approach: fault tree construction


The top event is already defined as ‘loss of propulsion for the tanker’. A simple way to break down the propulsion system is to emphasize on power transition in the main propulsion system. There are three independent events that may result in the top event. These are the ‘loss of propulsion power transmission’ in the shaft lines or gear, ‘loss of propulsion power generation’ from the engines, and ‘loss of propulsion power consumption’ due to propeller failure. Only one of these events has to occur in order to trigger the top event. Hence these three events have to be combined by an OR gate. The fault tree can be structured as shown below.



 The ‘loss of propulsion power transmission’ event in the above figure can be caused by gear failure and/or shaft line failure, and must therefore be combined through the use of an OR gate.


The ‘loss of propulsion power consumption’ event only includes the event of controllable pitch propeller (CPP) failure. In terms of the event of ‘loss of propulsion power generation’, both the starboard and port engines must fail to deliver power to the gear. An AND gate must therefore be used for these two events. There are two ways each engine can fail to deliver power to the gear: by failure of the clutch and by failure of the engine itself. An OR gate must be used for these events because one is sufficient for the engine to fail to deliver power to the gear. The events of main engine failure (both starboard and port engines) in the above figure need to be treated in further detail. According to the FMECA, the causes or basic failure events 1, 2 and 3 (see below table) are all gathered in the ‘main engine failure’ event, and these have to be combined through the use of an OR gate since one of the causes is enough for the main engine to fail.




    The main engine failure modes can be arranged/modelled in a fault tree  as shown in below figure.



Qualitative approach: establishing minimal cut sets


The MOCUS algorithm is applied (subscript s=starboard, subscript p =Port):


MOCUS step 1:

‘Loss of main propulsion power for a specified tanker under one year of normal operation.’




MOCUS step 2:






MOCUS step 3.1: for the ‘loss of propulsion power transmission’ event (i.e. E1 in the fault tree):







MOCUS step 3.2 – for the ‘loss of propulsion power generation’ event (i.e. E2 in the fault tree):











MOCUS step 3.3 – for the event that ‘starboard engine fails to deliver power to gear’ (i.e. E4 in the fault tree):













MOCUS step 3.4 – for the event of ‘starboard main engine failure’ (i.e. E6 in the fault tree)

















MOCUS step 3.5 – for the event of ‘port main engine failure’(i.e. E7 in the fault tree)




























































MOCUS step 4:


There are 19 possible combinations of basic causes (or basic event failures) for the propulsion system (each row). There are mostly two basic causes in each cut set. It is advantageous to have as many basic causes in each cut set as possible, and one and two basic causes in each cut set is not much. The cut sets K1, K2 and K19 include only one basic cause. Hence the top event is triggered when one of these basic causes occurs. It would therefore be advantageous to implement redundancy or other reliability improving measures for these cut sets. For example, would the use of two independent propeller systems create redundancy and hence reduce the risk for top event occurrence? This may, however, not be practicable.




In the fault tree analysis (FTA) section the probability for loss of the propulsion function on a tanker was estimated. The possible consequences that may result because of the lost propulsion function, however, have not been analysed so far. If the consequences of an event or incident are to be analysed, a so-called event tree analysis (ETA) approach may be applied.


The event tree splits up a given initiating event forwardly and is therefore an inductive method.




An ETA is a logical diagram based on chains of possible events. The logical diagram used in an ETA describes the relation between an initiating event and the events that describe the possible consequences.


The basic principle of the ETA approach is that each level in the chain of events leading to a consequence consists of two mutually exclusive dichotomy (separated) events. Two events are, by definition, mutually exclusive (or disjoint) if it is impossible for them to occur together at the same time.


Dichotomy means that an event can only have two different outcomes. For example, the event of a tanker collision may have two possible outcomes with respect to the oil cargo tanks: non-rupture of the cargo tanks or the rupture of these tanks, the latter resulting in oil pollution and possibly also a fire.


Based on this it is clear that ETA is a binary technique. An initiating event may develop into several consequences both in type and magnitude/severity. The likelihood of one event is dependent on the previous events, as well as the nature of the event.  




ETA is a quantitative method for the estimation of consequence probabilities based on a given initiating event. Hence the first task of the approach is to define the initiating event, which is the first in a sequence of events leading to a hazardous situation or accident.


Next, the safety systems, mechanisms and situation characteristics that function as barriers in the consequence development process are established in a chronological order.


The probabilities for the outcomes of each dichotomy event (e.g. the success of a particular safety barrier/mechanism) are then estimated and an initial event tree is established.


At this stage, however, the probability for each dichotomy event is independent of the previous events. Two events are, by definition, independent if the occurrence of one event does not give us any information about whether or not another event will occur, i.e. the events have no influence on each other. In reality, on the other hand, the events may to some degree be dependent on each other.


As presented in below figure, these dependencies can be related to the time, their location in the event chronology, and conditional involvements of previous events.




Some sort of correction for these dependencies should be performed. It is not, however, possible to establish a general procedure for such corrections.




In order to perform a realistic and acceptable ETA the analyst(s) must have sufficient system knowledge and understanding. In addition, common sense, as well as logical and creative thinking, are important resources in the process of performing an event tree analysis. The design of the event tree diagram is done using the following approach.


The events are arranged in chronological order with the initiating event on the top, followed by important and relevant intermediate events and the consequence events placed at the bottom. The binary dichotomy event occurrence is visualized in the event tree by placing the unwanted event (i.e. failure) to the right and the successful/desired event to the left.






The loss of propulsion power results in loss of controlled mobility for an oil tanker. The event of loss of propulsion power has been examined earlier in this forum using the fault tree analysis (FTA) approach. The potential consequences for the loss of propulsion power have not, however, been analysed in detail. Because the oil tanker has large oil spill potential, with devastating effects on the environment, it is of great interest to estimate the likelihood of an oil spill if propulsion function is lost. Such information can, for example, be used to evaluate whether additional safety measures should be implemented to reduce the probability for such accidents. For the given system description as in below figure, find the likelihood of oil spill when the propulsion function is lost.








The loss of propulsion power has a probability of 0.465 per year.




The initial event tree shown is designed as in below figure.





In this initial event tree, possible dependencies between the events have not been assessed. This assessment process is, however, far from easy and is normally carried out at the discretion of the analyst. The problems involved in assessing dependencies between events exist for all quantified methodologies. The dependencies between the events in the initial event tree are assessed in the influence diagram.




For example, it is found that the ‘critical impact forces’ event and the ‘emergency anchoring failure’ event are both dependent on the ‘critical weather force’ event. The ‘critical weather force’ event may, on the other hand, be dependent on the ‘critical drifting direction’ event.


Based on the influence diagram, an assessment of the probabilities is performed at the discretion of the analyst, and the event diagram shown below can then be established.




 The consequence probabilities are calculated by finding the product of all the events leading to the consequence, including the probability of the initiating top event in the event tree. As can be seen from the event tree in the above figure, the likelihood/probability of oil spill initiated by the loss of propulsion power, and caused by a critical stranding, is 0.048 per year of operation.


Conclusion and practicality of these mathematical circuses


To a professional sea-going mariner, port manager, insurers, etc. these techniques of Risk assessment, seems to be more just a fancy mental exercise, then being of some practical usefulness.


In fact there is assumption like probability of a certain event to occur, which is quite difficult to be found in a practical scenario and which require a very astute observation and data collection on the part of ship and shore based management and then there is a mental exercise to ascertain flowcharts for the simple and regular looking maritime operations.


In the era of short staffed ships and even more short staffed shore teams, where the hard-work of keeping engineering systems ship shape, experience of operators and their instinct decides the consequences, doing such exercises realistically, will definitely require an Artificially intelligent computer simulation system with regular updates of various scenarios and there probabilities, otherwise to the ordinary Maritime managers these techniques will remain only of Academic interest.















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Optimising a vessel’s route based on environmental information such as wind, waves and current patterns can lower fuel consumption and decrease delays while also reducing structural and cargo damage claims. Weather routing software products utilize not only weather and oceanographic data but also the hydrodynamic details of the vessel to provide the ship’s crew with real-time ship-specific routing advice. The Blog refers to software characteristics and benefits of voyage optimization.

The resolution A.528 (13) adopted by IMO in 1983 recognizes that weather routeing, by which ships are provided with "optimum routes" to avoid bad weather, can aid safety. It recommends Governments to advise ships flying their flags of the availability of weather routeing information, particularly that provided by services listed by the World Meteorological Organization.

The use of modem electronics for navigation such as GPS and ECDIS has significantly improved the safety of navigation. Still, strategic weather routing and hull engine monitoring are needed to plan and execute safe and efficient passages across the ocean.

The effort to develop an onboard guidance system started in the late 1970s when shipboard computers were first introduced in order to bring sea keeping knowledge to ships at sea.

Several attempts were later made to develop commercial systems for the shipping industry.

The wind and wave forecast limitations, the high cost of computers and the lack of an effective communications system explain why these early systems were not widely accepted by shipping companies as a cost-effective means of reducing damage.

Since then the weather routing systems evolved tremendously, from simple weather routing (weather forecasts converted to routing recommendations, neglecting vessel details) to more complex decision supporting systems.

The latter take into account the vessel’s behaviour in poor weather situations (computed with hydrodynamic methods) in addition to weather and oceanographic conditions.


Climatological maps and tables are used when planning a route. Climate routes reflect the seasonal variation of tropical and extra tropical storm tracks, monsoon regimes, wind speed and direction, wave height frequencies and ice limits, areas of high swell, sea ice limits and prevailing ocean currents, for the major ocean basins of the world.

All this information are contained in nautical publications such as: Pilot Chart Atlases, the Sailing Directions (Planning Guides), maps included in the Ocean Passages of the world publication, the Pilot books and other climatological sources.

When the voyage starts, the short term weather variability plays an important role. Two strategies can then be used: the ship can first follow the climate route and deviate if the weather becomes better or worse or can first follow the shortest track and deviate if the weather becomes worse.

The shipmaster has to take the final decision in the actual and forecasted operating condition which requires different sources of information such as the weather charts, the meteorological warnings, the operational conditions, the ship design characteristics etc.

All this information has to be carefully balanced and analysed to formulate an unambiguous advice on optimum speed or heading, change of loading condition or settings of active roll stabilizers.

The situations become complicated if routing considering safety and economy happen to conflict. Without a reliable decision support system it is difficult to judge the conditions in an objective manner, in particular during night.

Weather routing software represents a very useful support system due to its different tools that provide avoidance of bad weather, optimized routing advice and optimized speed along the route, monitoring of chartered vessels for speed claims, reduced risk of damage to cargo, vessel and persons and reduced propulsion power demand.

Two general types of routing services have been identified by Bowditch, 2002(in The American Practical Navigator: An epitome of navigation) :

the first provides forecast conditions and computes routing recommendations, which are then broadcast to the vessel; the second assembles and processes weather and sea condition data and transmits this to ships at sea for on-board processing and generation of route recommendations.

The former system allows for greater computer power to be applied to the routing task because powerful computers are available ashore. The latter system allows greater flexibility to the ship’s master in changing parameters, evaluating various scenarios, selecting routes and displaying data.


The Ship-board Weather Routing systems (SWR) are easy-to-handle systems. Various types are developed in the previous years, for example: BonVoyage System developed by Applied Weather Technology, Inc., Vessel Optimization and Safety System (VOSS) developed by Ocean Systems Inc. and Oceanweather Inc., and Vessel and Voyage Optimization Solution (VVOS) developed by Jeppesen Marine Inc. a Boeing company.

These ship board weather systems provide decision support for the navigator regarding optimum speed and course based on limit values for relevant ship response.

Furthermore, forecasted weather information is processed onboard to enable active planning of the route. The weather routing systems are and most probably will be further upgraded with fuel consumption modules in relation to the demand for practical guidance to reduce fuel consumption in waves. This also could lead to the reduction of the emissions of CO2, NOX and SOX.

The BonVoyage System provides the most recent weather and ocean data to the ship by broadband or email communications in a compressed format in order -to minimize communications costs. The captain can view and interpret the information due to the fact that the data are presented under the form of maps and graphics. The system also includes an algorithm that allows the delivery of estimates of fuel cost and time en-route(

The forecasts are of higher confidence for voyages of over 10 days due to the high-resolution of wind and wave data. These data provide better simulation and allow ship captains to take advantage of small variations in wind and wave to make safer route plans. Ship safety is improved due to the wave forecasts (72 hours) of the areas where a freak wave is most likely to occur. BonVoyage (BVS) is a helpful tool due to the prediction of speed loss (issued from its model on climatological ship resistance) and specific vessel consumption.

In May 2012 the BonVoyage System was integrated with Transas' Electronic Chart Display Navigation System (ECDIS) to help captains fully optimize their voyage planning. This allows now the data transfer from BVS to Transas Navi-Sailor ECDIS and vice-versa. In December 2013 BonVoyage System has been integrated with UKHO’s Admiralty e-Navigator and ChartCo’s Passage manager and has therefore the capability to interchange track waypoints with the above mentioned systems.

The combination between the BonVoyage System and the Ship route advisory Services allows the transfer of route data between ship and shore, a graphical depiction of weather, routes and currents through BVS, detailed current data with tidal streams, 16 day forecast 4 times a day etc.(

The Vessel Optimization and Safety System (VOSS) from Ocean Systems Inc. and Oceanweather Inc. is another provider of weather and oceanographic conditions forecast; global wind and wave models are generated for 10 days of forecast 365 days a year (as shown in below figure).


The twice daily forecast is available on 1.25 x 2.5 degree Lon/Lat global grid with update of global circulation -currents. Data include tropical cyclone tracks, 500 hPa heights, surface pressure, wind speed and direction and 3 -ave trains. Accuracy of the forecast is enhanced by real-time ingestion of satellite altimeter/ scatterometer wind and wave measurements (as shown in below figure), ocean buoys and ship observations, as well as by experienced meteorologists.


The VOSS system also provides customized ship response predictions with user specified loading conditions. The ship motion program takes into account voluntary speed reduction based on vessel motions propeller/engine limitations, allows user to simulate multiple routes for comparison. It also predicts roll and pitch motion, accelerations, slamming, bending moment, shear force, speed, power and RPM using forecast or user input sea and swell conditions.

Another algorithm is offered within this system for minimum time and minimum cost routes over a range of arrival times without exceeding the Safe Operating Envelope (SOE).

The Vessel and Voyage Optimization Solution (VVOS) from Jeppesen Marine Inc. a Boeing company is another weather routing system which automatically generates a full range of optimized routes for balancing trade-offs between ETA and fuel consumption; it also optimizes to minimum fuel speed plan for required arrival time and also realizes a comparison of VVOS optimal speed management to traditional strategies such as constant speed or “sprint and loiter”( . The simulation tools facilitate the analysis of any route using high-resolution forecast weather to weigh trade-offs among ETA, fuel consumption, ship motions, hull stresses, and weather and sea conditions. The high resolution forecasts of wind, wave and ocean current are for 15 days.

The most efficient routes are identified due to the fact that the system utilizes a just-in time operating strategy that avoids wasting fuel with sprint and loiter alternatives. The routing support from experienced ship masters is available 24/7/365. The system also ensures a route import/export in 20 different ECDIS formats, improving workflow and reducing mistakes.

The Vessel and Voyage Optimization Solution includes a guidance system that recommends speed and heading changes to manage ship motions and help minimize heavy weather damage; this is due to the use of hydrodynamic modelling, optimization algorithms and high-resolution ocean forecasts. VVOS includes a detailed, ship-specific model of user’s ship motion, engine and propeller characteristics. This ship model computes the speed made good under forecast wind, wave and ocean current conditions at a given engine power and propeller RPM, as well as ship motion limitations uniquely defined for each ship. The system also delivers accurate ETA predictions. At sea, ships download the latest ocean area forecasts via satellite communication. Masters can update and re-optimize passage plans as new forecasts become available or operational requirements change during a passage.

Waves forecast

Route selection and surveillance depend on all of the environmental factors but wind and wave’s optimization effect is the most important process in obtaining an optimum routing.

Waves forecast improved due to the refinement of short term numerical weather prediction forecast systems and their extension into the medium range and to the development of global spectral wave prediction models.

Over most of the global oceans there are few wave measurement sites available for model verification. Therefore, satellite radar altimeter estimates of significant wave heights are used (The significant wave height (Hs) is defined traditionally as the mean wave height (trough to crest) of the highest third of the waves (H1/3). The term is historical as this value appeared to be well correlated with visual estimates of wave heights from experienced observer, as also depicted in the previous figure)

Most measuring devices estimate the significant wave height from a wave spectrum; satellite radar altimeters are unique in measuring directly the significant wave height thanks to the different time of return from wave crests and troughs within the area illuminated by the radar.


As shown in first figure Significant wave height and direction, Oceanweather Inc. Modern ocean wave prediction systems can also estimate freak (rogue) wave events. This waves’ height is at least 2 times higher than the significant waves

New characteristics: avoidance of the Emission Control Areas (ECAs)

The latest version of the BonVoyage System allows the management of the voyage track by displaying ECA zones and making them “no-go” areas. Captains can see their voyage track outside and inside the ECA zones.

Simply moving waypoints in BVS allows them to visualize the impact of time in the ECA zone and compare it to the overall effect of time en route. With BVS’s ECA zone calculation tools, informed decisions can be adopted about how much time to sail inside or outside these zones. The goal is therefore to give captains and ship operators the data they need to manage voyage costs while complying with IMO regulations.

On August 1, 2012, North America Emissions Control Area (ECA) zones become enforceable. The regulation is part of Annex VI to the MARPOL Convention titled “Regulations for the Prevention of Air Pollution from Ships”. The regulation dictates that the ECA Zones extend up to 200 nautical miles from coasts of the United States and Canada, including a portion of the Hawaiian Islands. In the ECA Zones, ships are required to burn fuel with sulphur content not exceeding 1.00%. Notable exceptions to this area are the Aleutian Islands and Arctic waters of North America.


The ship-board weather routing systems intend to enhance the ship’s and crew safety at sea and to gain operational benefits by reducing repair times, reduced fuel expenses and less cargo claims.

The more advanced ship-board weather systems process weather data comprising wind and seaway information to continuously compute the ship’s response during the voyage. The technology still undergoes extensive development. Besides wind and wave forecasts, voyage optimization should also take into account sea surface currents since they can significantly impact ship speed and fuel consumption.

High resolution global circulation models enhanced by satellite measurements can now produce accurate depictions of major currents and eddies daily. Further advancements in meteorology are expected, especially in the forecast computer models, which will extend the time range and accuracy of the dynamic and statistical forecasts. Response models for sea-keeping and resistance in waves will be customised to individual ships and routes, which will be achieved by utilizing real-time and historical data with self-learning algorithms.

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This blog will discuss the history and the problems of the intact ship stability regulations entered into force over the years.

The problems involving ships stability loss as well as ships capsize concerned the maritime community from the first beginning, this type of problems being always a part of maritime safety. Maritime casualties related to loss of ship intact stability continue to be present despite the fact that ships comply with stability criteria.

The basic motivation behind writing this blog came from the feeling that key advances in the knowledge, understanding, and applicability of ship stability principles, stated in regulations, correlated with practical problems, can be integrated within a single framework.


The problem of stability of the floating bodies, which can be traced back to Archimedes himself, has never ceased to interest scientists and engineers and has become an important part of academic studies.

Intact Ship Stability have been known for a very long time in terms of positive righting moments. Since from 1747 Bouguer define in his work “Traite du navire, de sa construction et de ses mouvements” the metacentre as the intersection of two vertical axes passing through the centre of buoyancy (the centre of gravity of the displaced fluid) at two slightly different angles of heel.

Years later, Euler in “Scientia navalis sea Tractatus de Construendis ac Dirigendis Navibus” gave a general criterion of the ship stability, based on the restoring moment: the ship remains stable as far as the couple weight (applied in vessel’s center of gravity) and the buoyancy force (applied in vessel’s center of buoyancy) creates a restoring moment.

In 1757, Bernoulli, discovered the relationship between metacentric height (GM) and the rolling period of ships. Later on, Moesley, introduced the dynamic approach with respect to the area under level arm curves.

Around 1900, the problem of ships stability was considered as solved based on knowledge to evaluate the dynamic stability of existing ships. In fact, only the theoretically considerations were solved, but the main problem was to apply these fundamentals as a practical calculations of ships stability related to righting levers, having in view the complex geometry of ships hulls.

This problem remained up until last decades of 20th century, several methods, based on approximations, were invented to overcome this problem, but the final solutions came with the appearance of computers. Ship stability was judged mainly on the calculated value of metacentric height which also in nowadays is still wrongly viewed as a main factor.

In 1939 Rahola carried out extensive statistical investigations into ship stability. Various still water lever arm curves of capsized ships were analysed and he concluded that a large number of ships had righting levers below the minimum values of righting levers recommended by experts at that time. He identified that the ships had various values of righting levers, from too small, according to maritime board, to “critical” levers and sufficiently large lever arms. His investigations resulted finally in the definition of a “standard” lever arm curve defined by minimum levers at 20 and 30 degrees heel, the maximum lever being at 35 degrees heel and the angle of vanishing stability at 60 degrees.All lever arm curves are accepted as equivalent when the enclosed area up to 40 degrees is of the same amount or larger as the standard curve. Rahola’s investigation was a success and proved, later on, to be the base of minimum stability criteria adopted over the years.

Even the present intact ship stability criterion, issued by International Maritime Organization through Resolution MSC.267 (85), is based on Rahola’s conclusions.

From his investigation, it is important to note that ships that capsized due to dynamic effects like resonant rolling or shifting of cargo has been categorized as safe ships with sufficient large still water lever arms in most of the situations. Thus, dynamic influences were neither considered directly, nor indirectly, in Rahola’s minimum requirements.

Provisions concerning intact ship stability were introduced at a later stage in international regulations of ship safety. The necessity of intact stability rules was indeed uncertain until SOLAS ’48, as stated in Recommendations contained in Annex D, recommends to the Administrations a more detailed examination of intact ship stability.

The first international intact ship stability rule at IMO was originated by a recommendation contained in the conclusions of SOLAS’60, when for the first time was recommended to initiate studies on the basis of information referred by ships types, as intact stability for passenger ships, cargo ships and fishing vessels as well as standards of stability information.

As a result, the General Stability Criteria based on righting arm characteristics was adopted in 1968 with IMO Resolution A.167. This recommendation, known as “statistical criterion” is originated from the studies of Rahola and was developed in terms of global quantities related to initial metacentric height, static and dynamic stability arms satisfying a set of standards obtained empirically from statistics of casualties.

The requirements in Res. A.167 consisted of a minimum GM value, a minimum lever arm value at 30 degrees heel and three minimum areas below the lever arm curve. However, dynamic effects were not taken into account. When Res. A.167 was developed, data in sufficient quantity was only available for smaller ships, thus the resolution was applicable only to ships smaller than 100 meters in length. On one hand, it was simply to use but on the other hand it was difficult to improve as has no physical modelling and no mention to sea state and moreover the level of safety was unknown.

The introduction of Res. A.167 constituted a tremendous improvement of previous state of art regarding stability at international level but practically…was nothing. In comparison, all subsequent changes and new introduction can be considered only as smooth changes.

Again, as an answer to recommendations given in the conclusions of SOLAS’74, where was recommended the improvement of international standards on intact stability of ships taking into account the external forces affecting ships in seaway which may lead to capsize or unacceptable angles of heel, the Weather Criterion was adopted in 1985 by IMO Res. A.562. The main aim of this criterion was to assure that ships are able to withstand heeling moments due to incoming waves and wind without exceeding certain roll angles. The structure of the criterion was prescriptive as well, whereas the threshold values were based on statistical long-term evaluations of accidents made since the first formulation in the stability requirements of the Soviet Register of Shipping from 1947.

The critical KG value was adjusted to fit the mean of all KG values of ships in the statistics, which were considered safe in operation.

Shortly after its introduction, from the first time in 1985, the weather criterion was criticized. The main point of critics was, beside the partly unrealistic simplifications regarding the constant heeling lever due to wind and wave induced roll motion, that the criterion is calibrated for old ship types with traditional hull forms, moderate to small lateral areas and small B/T – ratios.

The general outcome of resolutions A.167 and A.562 is typically in the form of limiting curve for GM and KG as a function of ship draft. Comparisons have been made for families of ships of same typology between statistical and weather criteria requirements, generally finding that the second one is more severe.

Comparison has been made also between resolutions A.167, A.562 and SOLAS’90, for particular types of ships, like the modern large passenger cruise ships. It has to be observed that Res. A.167 is usually only subject to criticism while the other two instruments are severely criticized.

All recommendations and regulations relating to ship intact stability and safety against capsizing issued by the International Maritime Organization (IMO) were consolidated in Code on Intact Stability of All Types of Ships Covered by IMO Instruments, adopted by Res. A.749(18) on 4th November 1993.

With the adoption of Res. A749, which incorporates Res. A.167 the upper limitation in ship length was lost apparently without prejudice and both criteria, the general criteria and weather criteria, were considered for ships of 24 m in length and over.

The general intact stability criteria regarding lever arm curves proprieties are almost unchanged from those stated in Res. A.167.

All the general intact stability requirements were applicable to ships of 24 meters in length and larger. Surprisingly and in contrast to the old regulation A.167, they also applied to ships of more than 100 meters in length, although the majority of the ships represented in the statistical example on which the requirements were based, has a length of less than 60 meters.

It was widely accepted that the general intact stability criteria, in the form of Res. A.749 (18), do neither provide a sufficient level for large ships, nor do they assure a uniform safety level for ships of different size or type. One major reason for these problems was the fact that the minimum requirements were not being scaled with the ship size. In practice, this leads to the situations that a large container vessel of 300 meters in length is allowed to sail with the same minimum GM of 15 centimetres as a small coaster with a length of approximately 80 meters.

Applying Froude’s similarity law, it follows that lever arms increase with the geometrical scale λ with increasing ship size. Thus, in order to provide the same ability to resist heeling moments in the above mentioned example, the GM value would have to be increased for the large ships by the factor 300m/80m = 3.75.

The ‘severe wind and rolling criterion”, originally introduced by IMO Res. A.562(14) in 1985, was also part of the IMO Res. A.749(18).

As a consequence of the container ship development in the early 1980’s, a clear trend could be noted to ship designs with increasing beam of ships, without similar increase of the depth. This is simply, because this type of ship typically carries large amounts of deck cargo resulting in relative large vertical centres of gravity.

Under the pressure to optimize the ship’s economically, designers usually try to maximize the number of containers carried on deck. To fulfil the minimum stability requirements it is an appropriate measure to increase the ship’s beam and thus, to maximize the waterline area of the vessel. This results in larger initial stability, but reduced form stability, whereas an increase in depth is always unfavourable for the initial stability of the vessel (not for the form stability).

Large initial stability, low additional form stability and a relative small range of positive righting levers characterize the lever arm curves of the resulting ship designers.

Hull forms having large values B/T and B/D need larger righting levers than conventional hull forms. This may be explained by the reduced form stability combined with larger alteration on righting lever in waves. It was found that in bow or stern quartering seas, those vessels were endangered where the centre of gravity was significantly higher than the still water line.

The explanation might be that the difference between the alternating restoring moment due to the wave action and heeling moment takes larger values. Moreover, hull forms having large ratio of waterline coefficient over block coefficient are suspected to have large righting lever alterations in waves and therefore more vulnerable rolling.

The revision of Intact Stability Code started in 2001 and completed in 2006. The first step consisted in an important structural reorganization and in the development of an alternative way on experimental basis to fulfil the requirements of weather criterion for ships having parameters outside the original range.

All recommendations and regulations relating to ship intact stability and safety against capsizing issued by the IMO are consolidated nowadays in the International Code on Intact Stability (2008 IS Code) adopted by Res. MSC.267(85) on 4th December 2008.

Compliance with the new Code was required under changes to the SOLAS and Load Line Conventions, for ships whose keels are laid on or after July 1st, 2010, to which these Conventions apply.

The stability criteria as included in the revised Code are virtually the same as the original IMO Res. A.167 adopted in 1968 (statistical criteria) and in Res. A.562 adopted in 1985 (severe wind and rolling criterion) with small amendments and some relaxations. As a first main difference from the previous regulations, the new Code, which is referred to as the 2008 IS Code, has two parts:

Part A which is mandatory, contains general intact stability criteria for cargo and passenger ships and Part B, which is recommendatory, contains intact stability criteria for certain types of ships as recommendations and additional guidelines.

What has changed? There are two significant changes. The first is the requirement for all ships to demonstrate compliance with wind and wave criteria. If the standard criteria are not applicable to the vessel, due to the vessel dimensions falling outside those relevant for the formulae given, model tests may be used to derive a value for the angle of roll. Model tests may also be used to identify the wind heeling lever for all vessels.

The assumed weather criteria is simply to use, it is based on physical phenomena / modelling but was adjusted with capsizing casualties in the form of the wind velocity. In other words, the wind velocity in the weather criteria does not represent the actual sea state and has rather empirical meanings. Since the weather criteria involve such an empirical factor, it is not easy to improve the criteria. However, the simplified modelling takes into account only beam waves and wind, why no internal degree of freedom, like shifting of cargo or water on deck, was introduced. In fact, it concerns only one mode of ships loss and the level of safety is largely unknown.

Although it considers the dynamics of ship roll motions, at least in a simplified way, the prescriptive scenario of weather criteria is not suitable to assess phenomena endangering ships in head, following and quartering waves and it also never was intended to be used in such a way.

The second significant change is the requirement for flag administration approval of stability instruments, in cases where an instrument is proved to supplement the stability book. However, to be applied this requirement it is necessary the development of guidelines for the approval of stability instruments, defining acceptable tolerances.

The Code is still based on the same assumptions, according to which the ship indicator of stability safety is the righting arm curve on calm water.


There were still some other pending issues, connected with the possible consequences of a mandatory IS Code making impossible the adoption of some alternatives currently used by Administrations. The most important is connected again with the required minimum value for the angle of maximum righting lever.

The safety level guaranteed to the ships by the compliance with stability criteria, however, is in general unknown and it is still a big open problem. It is indeed typical to open the way to alternatives by stating that “a level of safety has to be guaranteed, as a minimum, by any alternative assessment”. Statements like this are often used to try to avoid excessive relaxation of safety standards, but in fact are less meaningful than they could appear.

Of course, ship safety at sea was greatly improved by the development and implementation of present stability criteria, as contained in IS Code, and other measures (for example the assignment of freeboard), although being these measures recommendatory in nature or not so widely adopted.

A black box is constituted by the sentence “to the satisfaction of the Administration” that often accompanies these alternative measures. Actually, these sentences should be accompanied by some guidelines or codes of practice.

In addition it is clear that the safety level is unequally distributed among different ship typologies and, even inside a given ship typology, it appears to be strongly dependent on ship size. This is particularly true for the General Criterion, which is the result of a global re-active approach.

It mixes indeed in the same pan good and bad designs in a set of standards most of which not having a clear physical relation with the phenomena they are trying to avoid.

Also the present version of Weather Criterion, due to its relatively poor, although physical, modelling spreads unevenly the safety level among ship types.

A study conducted in Japan on the capsizing probability of a sample of 29 passenger and 46 cargo ships marginally complying with both provisions of Intact Stability Code revealed that this quantity is spread in a wide interval covering many orders of magnitude. The results also indicate that the safety level is generally higher for ships with length higher than 100 m.

From point of view of ship safety this is however, not the final solution. From time to time, stability casualties happen in spite of the fact that the particular ship meets all existing IMO criteria.

The existing criteria may also be not applicable to some type of modern ships incorporating novel design features especially because original criteria as Res. A.167 developed more than forty years ago were based on casualty statistics that included mainly vessels under 100 m in length.

With many modern ships there is no previous experience in relation to safety and stability and satisfying existing criteria may not assure required level of safety.

In order to achieve sufficient level of safety with respect to stability, all elements creating stability system have to be taken into account. Taking into account the fact, that less than 20% of all casualties are caused by faulty or bad design of the ship, the safety requirements that refer mainly to design features of the ship cannot ensure sufficient level of safety, in particular with regard to ships having design features.

The general belief is that current ship stability regulations reflect little of the state of the art of ships behaviour and seakeeping in different practical situations, especially in rough seas. Additionally, ships that are categorized as safe continue to loss their intact stability due to influence of factors, which depend, directly or indirectly, on minimum stability requirements.

There is a necessity of rethinking of the stability problems, arising from the new ship design trends, new ship’s operation from economical point of view, as well as competitive officers on board vessels capable to face the new challenges, generating new requirements that

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Today’s ships are technologically advanced, thus determining the importance of the continuous professional development of seafarers, as well as the importance of decision making at all levels of the crew in high risk situations in which the ship can be found.

In spite of the development of marine technology and comprehensive training for maritime professions, there are frequent ship accidents, mostly as a result of human error. Experts often associate these errors with consciousness and conscience, the psychological factors that affect deliberation and decision making.

There is a tendency to overestimate the effects of technology, which stems from ignorance, fatigue, high spirits, preoccupation with factors that are not associated with work, etc.

Therefore, it has become important to study and teach about human behaviour on board, especially about the psychological and sociological aspects.

In psychology, research and theorizing focuses on the seafarers internal states as a result of the cause-effect relationship with the environment of individuals. Moreover, sociology studies their work context, such as organizational values and norms, the structure of work positions and their roles, power and leadership relations, etc.

Because of the comprehensive approach of the mentioned disciplines, the integration of their research goals is sometimes practiced, especially in psycho-sociology as an interdisciplinary science.

The comprehensive knowledge can contribute to an optimal education and informing of the crew in relation to the marine context, which is marked by constant and rapid technological advances, and increasingly diverse interaction between men and machines during working process.

Unfortunately, despite the development of psychology and sociology over the past century, there is little interest devoted to the study of maritime affairs within these disciplines. This is confirmed by rare and unsystematic literature, the underdevelopment of psychological and sociological sub-disciplines dealing with maritime affairs, as well as their non-representation in the education of seafarers.

However, it should be noted that the maritime theme is becoming a recognized subject of sociological interest. For example, in 2013, the European Sociological Association (ESA) organized two scientific conferences in Turin and Zadar to encourage its study.

Not surprisingly, they were held in traditionally maritime countries, but it is still too little an effort for a systematic approach to maritime affairs within the psychological and sociological sciences, which can contribute to the safety and efficiency of seafarers in a changing work environment.


Modern technological progress has led to a significant acceleration of lifestyle, as well as to having activities in several areas simultaneously for most of time.

The former meaning of time and space have been significantly changed. “The information technology has enabled people to interact almost simultaneously in their physical and virtual space that can be found in remote areas of the world. Hence the current age is often described as a “real virtuality”,“global village” and using other similar concepts.”

The achievements of modern communication technology allow each seafarer to be informed during the voyage about everything that happens with his family and the other important social groups, while he can perform various actions such as stock tickers considerations, observation of changes in the value of shares, on-line gambling and to have fun in different ways, in short – to do lot of things that were not possible twenty years ago while he was on board.

Previously, such activities were considered as plans when docking or upon arrival home. Actually, now sailor can actively participate in all the events which he used to take during his stay on the land, during the voyage.

However, there is one particular aspect that is reflected in the fact that the seaman is isolated from his family and other common environment and cannot react the same way as when he is situated in that setting. He is often just an observer of family and other emotionally important events, which he can only participate in from a distance. This dimension was even previously in the mind of sailors, but with the difference that just rare and filtered information were coming to seafarers by letter or telegraph and less frequently by phone, which for the most of them represented an emotional protection not just from others, but from themselves. This is not irrelevant according to the research which show that maritime accidents are still very frequent although shipbuilding industry has made significant efforts to improve the structure and reliability of ships to reduce the number of accidents and the value of the damage, but also to increase the efficiency and productivity of labour compliance.

However, while the former maritime accidents were frequent due to unsafe and unequipped ships, it is clear that modern shipping technology is only one factor in the overall safety of the ship where the man and his use of technology are crucial.

In addition to complexity of maritime occupations, technology often represents a new burden and challenge for sailors which they have to cope with. “It should be noted that technology always carries specific cultural meanings. It is necessary to train for its use that often involves changes in the perception of the environment such as changes in values and normative orientation of individuals.”

Furthermore, the technology provides lot of benefits. The development of shipping industry has contributed to global connecting, technological progress, expanding markets and increasing prosperity over the last two centuries.

“Seafaring contributes to globalization so far since it is the incomparably biggest and most important segment of the transport system by the value and quantity of transported goods.”

However, the technology carries risks that can endanger people and environment if used incorrectly. In order to be able to cope with these challenges, first we need to recognize them. Technological solutions take lot of actions that previously needed to be performed slowly and with more human involvement. However, it does not relieve employees from liability of programming, monitoring, supervising and coordinating activities with other agencies responsible for boating, boarding, docking, unloading and recently an increasing defense from hijackers.

All the above shows the necessity of monitoring technological developments with the ongoing influence of consciousness and conscience. As one’s presence of mind in the act of understanding and trials, one’s conscience (Latin Conscientia) is a subjective judgment about the morality of the desired act. It is the last standard that should be followed during the operation. This is allowed by morality, a psychological function, which enables one to impose and comply with value norms, but also to insist on self-punishment in the case of non-compliance.

His rules of conduct, man learns through his interaction with the outside world (environment), through a life-long process of socialization, in which he learns specifics of the society in which he lives. In time, he develops his identity through the internalization of values and norms, and when he starts to understand them as a part of himself, he holds to them firmly, seldom breaking them. During this process, in parallel, he develops his conscience according to the ethical principles, i.e. that which society comprehends as good and desirable.

Nevertheless, there are different reason behind why people, frequently or not, act in discordance with the established values and rules (hindered accomplishment of goals, quick social changes without the ability to adapt to them instantly, labelling individuals as deviant, which results in their association with other problematic individuals and groups, etc), which “society sanctions informally (rebuke, avoidance, etc) or formally (fines, prison, etc.) if such behaviour is recognized, depending on the severity of the deed”.

As a result of some kind of experiential (perceptional) integration and stabilization, consciousness (Latin Notitia) is correlated with morality and conscience, as well as the outside world. It shapes our experiences and distinguishes us from other living beings.

Obviously, it is not enough to be a good and experienced naval officer (be it captain or sailor) because the professional changes are such that one can always expect to make some significant errors in the evaluation and work during his career.

Therefore, we need to constantly contemplate our actions and adapt ourselves to the changing environment.


As a conscious being, human being has the ability to self-observation which means the ability to control and express procedures. Its review is often called the “voice of conscience” which is also referred as “practical reason”, which means that we explain, justify and analyse our actions.

Thus, conscience occurs simultaneously with observation as a functional analysis. Human being should perform tasks according to his conscience that is unconditionally connected to his duty, as a good and desirable action toward his environment.

Conscience is similar to a legal process and is often referred to as the inner judge. It arbitrates and imposes punishment often requiring a change in behaviour.

Since conscience is a subjective category, it is frequently repressed when people do not show remorse for their actions. “However, human being is a social being and he is liable to justify his arguments to others with their consciences.”.

The accident on a cruiser Costa Concordia suggests many questions about captain’s, officer’s and the rest of the crew’s conscience who had left the ship without care for the passengers.

Stranding on the Italian island Giglio rocks in early 2012, thirty-two passengers lost their lives. The captain did not call for help until the Livorno port authority compelled him to do so and to take command of evacuation.

Many examples show that maritime accidents are often caused by human error and that the malpractice after an accident leads to serious consequences. “More than 6000 people die on the sea everyday. An average of five shipwreck occur and take many human lives, permanently damaging the flora and fauna and causing significant economic losses.”

Some of the most distinct maritime accidents caused by careless actions are the sinking of the tanker Dona Paz in 1987, which collided with another tanker where the overcrowded boat killed 4341 people; the sinking of the Kursk submarine in 2000 that killed 118 crew members who lived a few days after the accident, but the Russian government has hesitated to seek international help, believing that they would rescue sailors; the sinking of the overcrowded ferry Jool in 2002 that killed more than 1000 passengers who rushed to one side in order to shelter from the oncoming storm.

Many other maritime accidents are associated with matters of conscience. Besides all the technical and technological improvements, the security on the modern ship is not satisfactory due to fact that 96% of the accidents are caused by the error of the crew of which 71% goes to management errors and 29% to the operational errors. They usually arise from multiple factors such as the dominant communication of the company in relation to the ship’s crew who passively complies with its demands, usually against their better judgement, the negative impact of arbitrary leadership on board with the crew uncritically meeting the requirements of the authority, excessive feeling of ability and the impact of modern technology which is used uncritically with susceptibility to technical and technological solutions.

One of the key factors that contribute to the large number of maritime accidents is certainly crew fatigue caused by excessive work, lack of sleep and its poor quality, stress, insufficient leisure time between periods of work and other factors.

Moreover, fatigue can be associated with development of technology that intensifies naval activity in terms of frequent short trips when crews work more than 12 hours per day, shorter stops in ports for loading and unloading of goods and people, frequent inspections and long-term reduction of crew.

Furthermore, the technology provides numerous opportunities for crew during leisure (playing computer games, surfing the Internet, communication with their families and friends, etc.) and thus contributes to fatigue as it may interfere when working.

However, it should be noted that technological advances have contributed to the overall development of our civilization and therefore the maritime industry which is reflected in the quality of today’s ships, sailor’s equipment, increasingly important and differentiated education for this activity, the quality of life on board, etc.

One should not ignore the danger of technology, which is consistent with the fact that it is a cultural product for who’s design man has a crucial impact, but on the other hand it changes society and people- their consciousness, values , norms and understanding of conscience.

Due to rapid development of technology, we are often in opportunity to let it manage everything for us. But is it always advisable to do this without supervision? Of course it is not due to the fact that technology does not have the intelligence and cannot make the best decisions in unforeseen situations.

Therefore, we need to constantly review the adverse effect of routine, monotony and the sense of power that can abate the observation and perception of certain signals. If everything repeatedly passes smoothly without problems, do we feel too relaxed? If so, it is conscience that springs to prevent us from the inappropriate relaxation.

Responsibility for human lives, the environment, property and all that we are entrusted with the management and usage should design not only knowledge but also the conscience, experience and skills that a person should have to deal with when seafaring.


The function of one’s conscience is essentially active in human conscious and unconscious actions. Conscientious people act automatically according to their ethical standards that lead them in various activities. Occasionally, however, they think about the attitude that needs to be built in relation to a particular person or a given situation, including orders.

Then the conscience is part of self-awareness and fully participates in the creation of the attitude that will be taken. Consciousness is one of the psychological concepts that cannot be directly seen or touched, yet it is more difficult to describe, but for most people it implies a reality that can be shared with others. We are not always aware of sensory stimuli. It may also happen that we are not aware of the effects of stimulus if we do not pay attention, but it does not mean that they do not participate in shaping.

In addition, everyone has a sense of self, others, things and events so we need to agree on common positions - especially if it is a duty. Discussion and agreement cannot be easily replaced by any technology or virtual world.

On the other hand, even though we are different, which is reflected in a variety of situations and relationships with different people, for most people there is a continuity of experience of their own personality. A large part of that continuity has emotional qualities and includes our relationship with other people, which is reflected in the form of general kindness, melancholy, shy demeanour, aggressive behaviour, etc. It is important to be aware that the emotional states can largely or decisively impact on the human experience, abilities and mindset.

Lieberman and Eagly, describe two types of processing arguments. One is systematic – one carefully examines the validity of the argument. Another includes shortcuts - it is superficial, much less careful and includes responses to a less important aspects of communication such as a personality or reputation of a person that gives an argument, not the validity of the argument. Other experts consider that people in a good mood follow shortcuts, while neutral or negative mood incline systematic deliberation of arguments.

In other words, instead of thinking, we often use the entrenched cliché and find it as an answer to a question or problem. Instead of stimulating our creativity, we hide behind the routine. In situations which require greater commitment, vigilance, attention and control increases the risk of overlooking important new elements that can significantly affect the conscientious performance of duty.

The systematic consideration of arguments and circumstances is particularly important in those areas (organizations) which are exposed to constant change and uncertainty, where the ship is certainly one of them.

Although there are cultural differences that affect decision-making, whereby “Westerners are more individualistic unlike Easterners that focus on collective and group evaluation, modern maritime occupations encourage initiative and the crew is chosen according the criteria of cultural coherence that allows functioning without major difficulties in communication and work”.

Importance of individuality as well as teamwork, responsibility and unity among the members are emphasized. Their characteristics, knowledge and skills are essential for successful business, based on the continuous improvement of individuals and the collective progress of “learning organization” through its members in order to successfully adapt to the overall changes.

Generally speaking, in all judgments we use incomplete knowledge and in such circumstances the judging process includes other elements. If you feel optimistic, it will affect your judgments. Good qualities and positive concepts are more easily available. Appending the effect by which every episode in memory is marked as one that has made us happy, sad, angry, etc., when we make a judgment our mood can act as a piece of information.

It is important not to forget that there is conscience besides consciousness that we have to consciously invite for help when taking the final attitude.


The way we access the problem is essential to our efficiency in its resolving. Our conscious action should be conscientious. In other words, it should be morally acceptable for us and others. Certainly, there are other factors that affect the efficiency in resolving problems such as the level of expertise, possibility of insight into the problem, etc.

When information is relatively unknown or unclear, emotional states have particular importance in human actions. With the impact of mood, people act systematically (in desolate or neutral mood) or by following shortcuts (in a good mood) that include routinely actions without much thought. Thoughtless action leaves considerable consequences for humans and environment, especially where changes are frequent, such as sailing.

Although marine technology is constantly advancing, accidents are still frequent and usually caused by error of the crew. Therefore, in the era of new knowledge and new technologies, it is essential to underline the key role of consciousness and conscience in controlling and responsible usage of technological advances in the current and future maritime activity.

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Golden Bollard 2017


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