Understanding System Sensors in maritime vessels

First of all, the basic requirements shall be reviewed.

Vessel sensors should at least measure vessel heading, vessel motions, and wind speed and direction.



The DP system shall have at least 3 sensors: Gyro (gyrocompass), Vertical Reference Sensor (VRS) and Wind sensor.

When an equipment class 2 or 3 DP control system is fully dependent on correct signals from vessel sensors, these signals should be based on three systems serving the same purpose (i.e. this will result in at least three heading reference sensors being installed).

MSC.1/Circ. 1580 


According to this requirement, DP class 2 and DP class 3 vessels shall be fitted with at least 3 gyrocompasses.

Sensors for the same purpose which are connected to redundant systems should be arranged independently so that failure of one will not affect the others. 

For equipment class 3, one of each type of sensor should be connected directly to the backup DP control system, and should be separated by an A-60 class division from the other sensors. If the data from these sensors is passed to the main DP control system for their use, this system should be arranged so that a failure in the main DP control system cannot affect the integrity of the signals to the backup DP control system. 

MSC.1/Circ. 1580


Failure of one sensor shall not affect serviceability of the other ones. For DP class 3 vessels, sensors for the back-up controller shall be connected to it directly and shall be separated from the other sensors (of the same type) with the bulkhead class A.60.


The main sensor is Gyro – it shows the heading and is responsible for yaw axis respectively. Without Gyro the system is not able to take yaw axis under control (auto-heading) and, as a result, will not be able to switch to Auto Positioning Mode (AutoPos). That is why, there is the following requirement – not less than three gyro compasses on DP class 2 vessels shall be installed.

Having three gyro compasses on board and when one of them starts to feed incorrect data, the system or personnel is able to compare the data from all gyro compasses and identify which one transmits inaccurate information. As for DP class 1 vessels, there are two gyro compasses installed only and it is impossible to find out which one failed by means of such comparison. That is why gyro compasses are compared with the magnetic compass and conclusions are drawn.

After determining the faulty gyro compass, it is necessary to ensure if it is not set as a preferable one (Preference) in the DP system. If so, a serviceable gyrocompass shall be set as “Preference”.

Vertical Reference Sensor (VRS) or Motion Reference Unit (MRU) – is a sensor, enabling the DP system to measure deviation angles of the vessel in relation to her vertical position. The difference is that VRS is a previous generation sensor, measuring Pitch and Roll only. MRU – is a modern one and is able to measure Pitch, Roll and Heave.

Wind Sensor – is a sensor of the wind direction and speed. One of the forces that influence the vessel (wind, waves and current) but that can be accurately measured is the wind force. The rest of the forces, affecting the vessel, cannot be read and the DP system calculates them by means of mathematical modelling. The overall influence of these forces, received by the calculation, is called DP Current or Residual force.

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Advancing Your Maritime Career through Experience and Work

Life at sea is a busy life. When you work in a seafarer job it can sometimes feel a bit like eat, work, sleep, repeat. But when you have a moment to yourself in between your watch or shift, there are still things you can do to relax, have some fun, and, just as importantly, progress your career at sea by indulging in some online learning. 

Yes, we know, it might feel like all you want to do is sleep when you’ve clocked off, but making time for yourself and your career, hanging out with your crewmates, or spending some time learning from older and wiser crew onboard will make life at sea more enjoyable and worthwhile.


Life at Sea and Online Seafarer Learning

With that in mind, we are looking at 6 ways you can make good use of your downtime when you’re working in a seafarer job.

The obvious one: video games

Let’s be honest, sometimes all we want to do is finish work and pick up that console! And to be fair, it’s a good way of switching off and getting some downtime. But why not make gaming more sociable by organizing a tournament with your fellow crew and enjoying some healthy competition? 

The chilled one: movie night

 Watching a movie (or binge watching a series) is a great way of kicking back and relaxing after you’ve finished work. Whether you watch your favorite oldies or new movies and television shows alone during your free time or with others,  it will always give you something to talk about with your crewmates.

The useful one: online learning

If you’ve been meaning to learn a new skill or pick up some additional knowledge but you never seem to have the time, it’s time to get real. When you’re in between shifts or watches, and if you’re serious about your maritime career, even spending half an hour a day learning something new will be time well spent. There are plenty of online seafarer courses out there, so pick one that’s relevant to you, and enhance your career prospects while you’re onboard.

The old school one: board games

 Why not put the console down and keep it old school instead by organizing a game of cards or a board game night? It may seem old fashioned but you might be surprised at how much you enjoy some fun childhood favorites - and of course there are lots of board games designed for adults too. Make it as fun and friendly or as competitive as you feel your crewmates can handle!  

Understanding the Role of Controllers in the DP System

While speaking about a controller, the word “computer” as well as the word “brain” are often used, as all calculations and control of the DP system are done there. The word “controller” will be used to avoid confusion as there is a computer in the base of the DP console either. 

There is one controller on DP class 1 vessel and there are two controllers on DP class 2 vessels respectively. There are some requirements for the latter: in case of a failure of one controller, another one shall take over the control and shall not be affected. To provide this, in other words redundancy, a communication of two units needs to be established and changing from an online controller to a back-up one shall be made automatically.

For equipment class 1, the DP control system need not be redundant. 


For equipment class 2, the DP control system should consist of at least two computer systems so that, in case of any single failure, automatic position keeping ability will be maintained. Common facilities such as self-checking routines, alignment facilities, data transfer arrangements and plant interfaces should not be capable of causing failure of more than one computer system. An alarm should be initiated if any computer fails or is not ready to take control. 



All of the above shall be explained: there is no idea of worse-better, main-auxiliary or master-slave – both controllers are equal as per their characteristics. One can encounter the following practice on board, when the use of controllers is done using a schedule one week on-line, the other one is back-up. Thus, one controller is active (controlling the operations) and the second one is back-up (ready to take over the control at any moment).

DP class 3 vessel shall have at least two controllers complying with the DP class 2 requirements and one additional back-up controller, which is separated with a fireproof bulkhead (A.60 class). During DP operation this back-up controller shall constantly receive information from sensors, reference systems, thruster feedback, etc.

For equipment class 3, the main DP control system should consist of at least two computer systems arranged so that, in case of any single failure, automatic position keeping ability will be maintained. Common facilities such as self-checking routines, alignment facilities, data transfer arrangements and plant interfaces should not be capable of causing failure of more than one computer system. The two or more computer systems mentioned above do not include the backup computer system; thus, in addition, one separate backup DP control system should be arranged, see paragraph below. An alarm should be initiated if any computer fails or is not ready to take control. 

For equipment class 3, the backup DP control system should be in a room separated by an A-60 class division from the main DP control station. During DP operation, this backup control system should be continuously updated by input from at least one of the required sets of sensors, position reference system, thruster feedback, etc. and be ready to take over control. The switchover of control to the backup system should be manual, situated on the backup computer, and should not be affected by a failure of the main DP control system. Main and backup DP control systems should be so arranged that at least one system will be able to perform automatic position keeping after any single failure. 

MSC.1/Circ. 1580


The third controller is mentioned as a back-up one, though it is able to control position of the vessel by itself. Switching over to it is performed manually. Based on the above, any failure, whatever it is, shall not affect the back-up controller. If any of the controllers are not able to take over the control, the DP system shall initiate corresponding alarm.

Also, controllers communicate and verify each other, e.g. the alarm goes off, if one of the controllers works slower, i.e. the rate of information processing of such a controller differs - it is not synchronized with another one or other ones and is not ready to take over the control. 


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The HiPAP system is a high precision acoustic positioning system that is used for positioning of subsea targets on both shallow and deep water. It uses both Super Short Base Line (SSBL) and Long Base Line (LBL) positioning techniques. The HiPAP system establishes subsea positioning so accurate in SSBL mode that the more complex LBL principle is made redundant within reasonable depths. The time and cost of survey operations are therefore reduced to a minimum.

The HiPAP system is also a reliable underwater reference for Dynamic Positioning (DP) systems. The system always sends raw position data to the DP system, allowing the DP itself to perform the evaluation, weighting and filtering of its references. The HiPAP system is important for safe operation of dynamic positioning systems because it provides extreme positioning accuracy and reliable underwater reference for DP systems.

High Precision Acoustic Positioning System (HiPAP) has a number of advantages and applications that make it useful in various maritime  operations and there's a HiPAP Basic Skills video course with more detailed description.

This video material contains experience sharing collected from many years of hydro acoustic usage. It is essential for confident operation of HiPAP system in dynamic positioning and will help you develop your knowledge for the further understanding and use of APOS system. The material involves all necessary explanations and aspects of hydroacoustic system setup and principle of operation for dynamic positioning.

The video material consists of:

  • Basic understanding of sound in water, its properties, and its effect from surrounding factors.
  • General familiarization with HiPAP and APOS.
  • All steps from A to Z in setting up and using the system for dynamic positioning.
  • Practical use of transponders and hydroacoustic system in SSBL mode.
  • Geographic position in SSBL.

“Basic Operations with HiPAP” is made for the basic level of Marine Officers/DPO/JDPO who would like to boost their knowledge about the sound in water and how to use it for dynamic positioning in SSBL mode (Super Short Base Line). The material is prepared by seafarers for seafarers containing only essential info for beginners to improve confidence in operations with hydroacoustic systems. The material is taken on a live system in operational conditions.

DP and Non-DP. Dynamic positioning of offshore vessels

If you’re considering an offshore fleet, let’s look at the difference between ships with dynamic positioning (DP) and those without. For many offshore operations, it’s necessary to keep a vessel at a fixed position and heading. Traditionally, this has been done using an anchor spread. Nowadays, dynamic positioning (DP) systems are replacing anchors. A seagoing vessel is subjected to forces from wind, waves, and currents as well as from forces generated by the propulsion system.

The vessel’s response to these forces - its changes in position, heading, and speed - is measured by the position-reference systems and the gyrocompass. Readings from the reference systems are corrected for roll and pitch using readings from the vertical reference sensors. Wind speed and direction are measured by the wind sensors. The DP control system calculates the forces that the thrusters must produce to control the vessel’s motion in three degrees of freedom - surge, sway, and yaw - in the horizontal plane. Dynamic positioning systems are typically used by offshore vessels for accurate maneuvering, maintaining a fixed position or track keeping (pipe/cable laying).

DP systems are usually found on offshore drilling vessels (drilling ships and semi-submersibles), offshore support vessels (platform supply vessels (PSVs), well intervention vessels, diving support vessels), pipe-laying and offshore construction vessels, dredging vessels (suction hopper dredgers, trenching vessels), rock-dumping vessels, and shuttle tankers (during offloading of FPSOs)

DP systems are divided into three classes (according to the degree of reliability): 


Class 1 (DP 1). The “loss” of a given position by a ship can occur in the event of any single malfunction.

Class 2 (DP 2). “Loss” of position does not occur in the event of a single failure of any subsystem or component (propulsion, sensor, control console, etc.), including cables, pipes, etc.

Class 3 (DP 3). The term “single fault” includes, in addition to the faults specified for Class DP-2, the complete failure of all components within one waterproof or fireproof compartment due to fire or flooding.

A non-DP (Dynamic Positioning) vessel refers to a type of ship or boat that does not have dynamic positioning capabilities.

Non-DP vessels rely on traditional methods of navigation and positioning, such as using anchors, mooring lines, and thrusters for maneuvering and maintaining their position manually. These vessels may be equipped with traditional navigation systems like GPS (Global Positioning System) and other instruments to assist in navigation and maneuvering.

It's important to note that the lack of dynamic positioning capability means that non-DP vessels may not be suitable for operations that require precise and stationary positioning, such as deep sea drilling, subsea construction, or underwater exploration in challenging conditions. In such cases, DP vessels are preferred due to their ability to maintain position accurately and efficiently. 

The salary difference between DP (Dynamic Positioning) and non-DP vessels can vary based on several factors, including the type of vessel, job responsibilities, experience level, and location. However, in general, salaries for crew members working on DP vessels tend to be higher compared to those on non-DP vessels.

DP vessels require specialized skills and training, and crew members operating and maintaining the dynamic positioning system are typically paid higher salaries due to the additional responsibilities and technical expertise involved. These positions may include DP operators, DP technicians, DP engineers, and DP officers.

On the other hand, non-DP vessels may have a broader range of crew positions that are not directly related to dynamic positioning operations. These positions can include captains, officers, engineers, deckhands, and other seafarers. The salaries for these roles on non-DP vessels can vary depending on factors such as experience, rank, and the type of vessel.

Additionally, the overall demand and market conditions for DP vessel operations can influence salary levels. In regions or industries where there is a high demand for DP vessels and a shortage of qualified personnel, salaries may be higher to attract and retain skilled crew members.

The integration of DP (Dynamic Positioning) technology into the merchant fleet has been steadily increasing in recent years. While DP systems were traditionally associated with offshore support vessels and specialized industries like oil and gas, they are now being adopted by a wider range of merchant vessels for various purposes.


Here are some key areas where DP integration has been seen in the merchant fleet:


Cruise Ships: Cruise ships are increasingly utilizing DP systems to enhance passenger comfort and safety during operations such as docking and maneuvering in narrow spaces.

Ferries: Some ferry operators have integrated DP technology to optimize docking and ensure precise positioning, improving the efficiency of passenger embarkation and disembarkation.

Specialized Vessels: Other merchant vessels, such as cable-laying ships, pipe-laying vessels, and heavy-lift vessels, are also incorporating DP technology to ensure accurate positioning and stability during critical operations.

The integration of DP systems into the merchant fleet requires specialized training and expertise for crew members responsible for operating and maintaining these systems. There are established guidelines and standards, DP Operator Training Schemes, recommendations and procedures developed by internationally recognized organizations to ensure proper training and certification for DP operators as well as safety of operations.

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Expert Tips for Landing Your Next Maritime Job

Whether you’re a cadet fresh out of maritime academy, a seafarer who has spent some time ashore and wants to get back to working in a job at sea, or someone who’s looking for their next job in the maritime industry, if you’re serious about finding a seafarer job, apart from being qualified, the next best thing you can do is to make sure you’re organized.

You don’t need us to tell you that maritime jobs aren’t regular 9 to 5s where you stay with the same company for a few years at least. Most careers at sea mean working with different employers and signing many different contracts.

And that means you must be prepared when you need to find your next position.But if you’re not a naturally organized person this can feel a bit intimidating!

So with that in mind, we’re going to give you a few tips about how to make your search for jobs at sea more efficient. Let’s face it - when you’re more organized you’ll be able to focus on your current job better and be able to relax when it comes to time ashore!


3 Top Tips for Finding Your Next Job at Sea

If you’re looking for your next sea job, chances are you’re applying to different employers. It makes sense that the more applications you submit, the higher the likelihood of you finding your next job is, right?

Sure. But the problem is that the more CVs you send, the harder it is to keep track of your applications. Not to mention the time and effort that’s needed to communicate with all the different manning agencies and employers.

You want to make the most of your downtime and shore leave. And you don’t want to look unreliable because you’ve forgotten to reply to an email or missed an interview.

So what can you do? Here are 3 do-able quick tips to finding your next seafarer job with less stress!

Create a Spreadsheet

Whether you use Excel, Google Sheets or another type of spreadsheet software, trust us, this will make life so much easier. And you don’t need to be technically-minded!

A basic list of the companies or manning agencies you’ve applied to will be massively helpful in keeping what jobs you’re interested in and with who in order.

Things to include are the company’s name, the date you applied, the type of vessel, and the crew change date. You could also add the name of who you spoke to, their contact details and the vessel, and then update it with the current status of your application.


Use a Manning Agency

Using a manning agency is a great time saver to find your next job at sea because they do the hard work for you. You don’t need to use your precious time chasing up employers as that’s their job.

We strongly advise knowing who you’re dealing with though. There are a good number of scam agents out there so please do watch your back. This article tells you how to spot scammers who offer fake seafarer jobs.

Put simply, a good, reputable manning agent will look after its seafarers and not charge you money to find you a job.


Use an App to Find Seafarer Jobs on the Go

As a seafarer you travel a lot. Which is why you need to make your search for maritime job  vacancies as quick and easy as possible. That’s why we like mobile apps for seafarers.

Look for an app that gives you instant access to seafarer jobs, that lets you create and update your seafarer profile, send and receive messages from potential employers and allows you to manage your upcoming crew changes.

After all, you’ve got enough to do so why not make finding your next seafarer job easier - wherever you are?

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Exploring Competencies and Their Impact on Seafarers

As someone working in a seafarer job, your ability to perform your job safely and competently at all times - even when under pressure - is essential. Working at sea, no two days are the same and there are a number of factors that can play a huge part in how your day plays out.

You may be working in difficult weather conditions. The sea may be rolling and rough. And,  depending on your rank and role, you might be working with dangerous or complex machinery or systems. Put simply, there are any number of challenges you will need to be prepared to meet.

Which is why the only way that you, as a seafarer, can possibly be prepared for anything your vessel or the elements has to throw at you is through training and education.

After all, professionalism and safety is paramount on a vessel and knowing how to act in every possible situation to ensure your safety, that of your fellow crew members, the cargo, and the vessel is key.

And that is where competencies for seafarers come into the picture.

The Importance of Competencies for Seafarers

First of all, what does ‘competent’ actually mean? 

The dictionary describes competent as “Having the necessary ability, knowledge, or skill to do something successfully.”

And whether you are an officer of the watch, a bosun, a chief engineer or a deck cadet you need that ‘necessary ability, knowledge, or skill’ to perform your tasks onboard to the highest standard. 

However, we know that, unfortunately, accidents can, and do, happen - in every workplace, not just the maritime industry. And like it or not, the majority of accidents happen because of human error - whether they’re on board a container ship or in a factory. 

And, if you’re a seafarer, you don’t need us to tell you that accidents that happen at sea can have catastrophic consequences.

Therefore, maritime training is something that needs to be taken very seriously. After all, you can never have too much education!

What Are Seafarer Competencies?

As you likely know, if you want to get ahead in your maritime career, the more skills and knowledge you have, the better. 

In the shipping industry competency assessments are used to validate the skills and knowledge that you hold as a seafarer for the vital role you have to play onboard your vessel. 

So what are the competencies of a seafarer? Let’s take one rank as an example.

Let’s say, for the purpose of this article, that you’re an able bodied seaman. That means that you should have a sound knowledge of seamanship and your competencies will include medical first aid (including CPR), lifesaving and firefighting. With that comes knowing how to use firefighting and safety equipment.

And talking of equipment, in our example of an AB role, you will also need to be able to confidently undertake general maintenance on the deck and have an understanding of the workings, operation and repair/maintenance of any equipment that you need to use on your vessel.

You will also be called upon to understand the principles and procedures that enable you to perform different tasks within your remit as well as being expected to be well versed in cargo operations.

How to Add to Your Seafarer Skill Set

No matter what seafarer rank you are, if you want to ensure your career at sea goes from strength to strength it is imperative that you continue to build on your skill set and knowledge base.

And one way you can do this is by adding to the knowledge you gained at maritime academy and at sea.

For example, could gaining basic skills in the High Precision Acoustic Positioning system (HiPAP) elevate your career? Or would knowing more about how to calculate quantities of grain cargo help you gain your Chief Mate’s license? 

And even if you’re a Captain or Chief Officer who has already covered grain stability in the past, you might find that our course gives you that timely refresher that we all need now and again when we’ve been doing the same job for a while!
There are only so many jobs on ships to go round - and a lot of seafarers, with more coming up through the maritime academies every semester. So if you understand that training is the way forward in your career, why not take a look at our accessible and affordable online seafarer training courses and further your employment opportunities today.

Mastering Grain Stability for Bulk Carriage

The carriage of grain in bulk can pose certain risks and challenges, which require careful consideration and management to ensure safe transportation. Here are some reasons why the carriage of grain in bulk can be considered dangerous:

Shifting and Unstable Loads: Grain cargoes are prone to shifting and settling during transportation, particularly due to the movement of the ship. This can lead to unstable loads and changes in the ship's stability, potentially resulting in a loss of stability and the risk of capsizing or listing. If the cargo shifts suddenly, it can cause the ship to become unbalanced and lead to dangerous situations.

Free Surface Effect: Grain cargoes are often not completely solid but can have void spaces or voids filled with air. This can create a free surface effect, where the grain cargo can slosh or shift within the cargo hold, impacting the ship's stability. The free surface effect can reduce the ship's metacentric height (GM) and increase the risk of excessive roll or even capsizing in rough seas.

Spontaneous Combustion: Some types of grain, such as oily seeds or grains with high moisture content, are prone to spontaneous combustion under certain conditions. If the cargo is not properly stored, ventilated, or monitored, heat can build up within the cargo, leading to self-ignition and the risk of fire onboard the ship.

Moisture Content and Contamination: Grain cargoes are sensitive to moisture content and contamination. Excessive moisture can cause grain to spoil, leading to the release of harmful gases like carbon dioxide or methane, which can be hazardous to crew members. Contamination by foreign substances, such as chemicals or toxic materials, can also pose health risks and compromise the quality of the cargo.

Structural Overloading: Grain cargoes are generally heavy, and when loaded in bulk, they can exert significant pressure on the ship's structure, including the cargo holds, hatch covers, and bulkheads. Overloading or uneven loading of grain cargo can exceed the structural limits of the ship, leading to structural failures, hull deformations, or even cargo hold collapses.

To mitigate these risks, various measures and regulations are in place to ensure safe carriage of grain in bulk. These include proper cargo handling procedures, monitoring moisture content, ventilation and temperature control, compliance with stability criteria, and adherence to international guidelines and standards, such as those provided by the International Grain Code and the International Maritime Organization (IMO).

Performing grain stability calculations on a ship is important for several reasons:

Structural Integrity: Grain stability calculations help ensure the structural integrity of the ship's cargo holds. Grain cargoes, such as wheat, corn, or rice, can shift during transportation due to the movement of the ship, leading to uneven loading and potential stresses on the ship's structure. By calculating grain stability, the ship's operators can determine the optimal loading configuration and prevent excessive stresses that could compromise the integrity of the cargo holds or the entire vessel.

Safety: Maintaining grain stability is crucial for the safety of the crew, the ship, and the environment. If the cargo shifts significantly, it can result in a loss of stability and increase the risk of capsizing or listing. By performing grain stability calculations, the ship's operators can ensure that the cargo is loaded in a stable manner, minimizing the risk of accidents or cargo shifting during rough seas or sudden maneuvers.

Compliance: Grain stability calculations are often required by regulations and standards set forth by maritime authorities and organizations. For example, the International Maritime Organization (IMO) provides guidelines on the safe carriage of grain cargoes, including stability criteria that must be met. By conducting grain stability calculations, shipowners and operators can demonstrate compliance with these regulations and avoid penalties or restrictions on cargo transportation.

Efficient Space Utilization: Grain stability calculations can also help optimize the use of available cargo space on a ship. By determining the optimal loading patterns and distribution of grain cargo, operators can maximize the amount of cargo that can be transported while maintaining stability. This can lead to improved efficiency, reduced transportation costs, and increased profitability.

In summary, grain stability calculations on a ship are essential for ensuring structural integrity, maintaining safety, complying with regulations, and optimizing cargo space utilization. These calculations help prevent accidents, protect the crew and the environment, and facilitate efficient and safe transportation of grain cargoes.


Different Types of Fleet in the Maritime Industry

Working at sea can be fraught with various dangers and problems for seafarers, the profession of seafarer attracts many young people. But a job at sea implies a long absence from the shore, away from relatives and loved ones. Some become sailors in order to continue family traditions.

An important factor in choosing a maritime profession for many is the prospect of career growth and, therefore, the opportunity to earn more money in the future. But in order to develop in this field in the future, it is necessary to understand what specialties exist and what specialists are required.

When you are coming to fleet choices, it's important to note that each fleet category includes a wide range of vessel sizes and specifications to suit specific operational requirements. Additionally, advancements in maritime technology and sustainability practices have led to the development of hybrid vessels, electric ferries, and more eco-friendly solutions within the maritime industry.  Consulting with maritime experts can provide valuable guidance to ensure the fleet choice aligns with the specific needs of seafaring operations.. Here are some common types of fleets in the maritime industry and the vessels typically chosen for each category:

Cargo fleet is for transporting goods and commodities by sea, cargo fleets often consist of container ships, bulk carriers, and general cargo ships. These vessels are designed to efficiently carry large quantities of cargo. Examples include Panamax and Post-Panamax container ships, Capesize bulk carriers, and multipurpose cargo ships.

Tanker fleet is involved in transporting various liquid cargoes, such as crude oil, petroleum products, chemicals, and liquefied natural gas (LNG). Tanker vessels are classified into different categories based on their cargo type and size. Common types include crude oil tankers, product tankers, chemical tankers, and LNG carriers.

Passenger fleet is dedicated to providing transportation services for passengers. Passenger fleets include cruise ships, ferries, and luxury yachts. Cruise ships come in various sizes, accommodating a large number of passengers, while ferries serve shorter distances, often transporting vehicles and pedestrians across water bodies.

Offshore fleet support various offshore operations, such as oil and gas exploration, production, and maintenance. Offshore fleet typically consists of offshore supply vessels (OSVs), platform supply vessels (PSVs), anchor handling tug supply vessels (AHTS), and crew boats. These vessels are equipped to transport supplies, personnel, and equipment to offshore installations.

Fishing fleet is involved in commercial fishing activities, including catching, processing, and storing fish and seafood products. These fleets comprise fishing trawlers, longliners, purse seiners, and factory ships equipped with processing facilities.

Research Fleet is dedicated to scientific exploration, oceanographic studies, and marine research. These fleets may include research vessels equipped with advanced scientific equipment, laboratories, and diving facilities to support various scientific missions and data collection.

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Demystifying Azimuth Thrusters: maritime navigation at first

Earlier we discussed different types of thrusters in the article “Components of the DP system - Thrusters”. Dynamic Positioning (DP) systems maintains the position and heading of a vessel or offshore floating unit by means of thrusters, without the need for anchors. Thrusters play a crucial role in DP systems by providing the necessary thrust for position and heading control.

Azimuth thruster is capable of rotating 360 degrees. Being able to develop the thrust in any direction, a vessel with azimuth thrusters has good maneuvering characteristics. Azimuth thrusters can be both auxiliary and main source of thrust development, and they may have fixed-pitch propellers or controllable-pitch propellers.

The pod is typically located below the waterline and can be rotated by a hydraulic or electric motor.

By having the ability to rotate the thrust vector, ships equipped with azimuth thrusters can change direction of movement quickly and easily, making them highly maneuverable. This makes them particularly useful for tugboats, offshore supply vessels, and dynamic positioning systems for maintaining the position of floating structures.

The size and power of azimuth thrusters can vary depending on the specific application and vessel size. They are typically electrically or mechanically driven and can range from a few hundred kilowatts to several megawatts in power.

But sometimes the specific tasks require to limit sector of azimuth thruster rotation. For this purpose there are several modes available in the DP System.  

Fixed Azimuth function can be usable when the thruster force is necessary to fix in a particular direction. This function shall be used when the vessel has an azimuth thruster located in the fore-and-aft centre line, usually closer to the bow from the midships and aimed to act against main environmental force, depending on which one is stronger at present moment: wind, current or their interaction. Thus, such an azimuth thruster takes the main load while the others just correct the vessel’s position with the minimum one.

While fixed, azimuth thrusters don’t provide the vessel with such a maneuverability, as a fully steerable azimuth thrusters. But they are still valuable propulsion systems in certain applications, providing additional thrust and maneuvering capabilities to enhance vessel control in specific directions.

Biasing Mode is a mode, when two azimuth thrusters work compensating each other (in opposite directions), e.g. it is used in light environmental conditions to avoid constant thruster spin (hunting for a direction). Thruster Biasing has three main parameters: minimum load, at which azimuth thrusters work against each other (counteract); working sector of azimuth thrusters (Angle factor) and load percentage of the azimuth thrusters, when they exit ‘Biasing Mode’ and start working in the same direction, sharing the load demand (Turn factor). In the neutral condition, therefore, two thrusters work in the opposite direction with the power load, set by the operator. In order to provide sustained direction of forward or aft movement, both azimuth thrusters pivot within the predetermined sector, so that the sum linear vector is developed, while lateral vectors compensate each other. They can increase force making the vessel move faster, but they cannot decrease it lower than the level, set by the operator. In order to provide movement to port or starboard direction, one azimuth thruster develops more force than the other.

The Turn factor determines when to turn a thruster within a group, instead of continuing to counteract the other thruster. The maximum force for each thruster is 10 tones and the idle or bias force is 2 tones.

The Angle factor determines the relative priority of angle against force to satisfy the force demand. The same 10 tones demand ahead is achieved, but more thrust is used with a higher angle factor, than with a lower angle factor.

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