cruise ship tug boat

The Ultimate Guide to Tug Boats: Types, Functions, and Applications

A tug, or more commonly a tugboat, is an assistance boat which helps in the mooring or berthing operation of a ship by either towing or pushing a vessel towards the port.

A tug is a particular class of boat which helps mega-ships enter or leave a port. In addition to towing the vessel towards the harbour, tug boats can also be engaged to provide essentials, such as water, air, etc., to a vessel.

Tug boats are also essential for non-self-propelled barges, oil platforms, log rafts, etc. Due to their solid structural engineering, tugs are small but relatively powerful machines.

Their propulsion system is the main reason behind their enormous strength. Some secondary functions of a tug boat, along with easing mooring operation, are listed below:

• They can work as salvage boats and icebreakers.
• They can also have fire fighting accessories to assist in port or barges.
• They are the most critical marine vessels, acting as saviours to ships in hard times, such as in narrow canals and lousy weather.

Most tugboats can also venture into the ocean, but some do not have that propulsion power, like river tugs. River tugs are towboats designed to help out in rivers and canals. Their varied hull types make it dangerous for them to venture into the open ocean.

Renowned tugboat builders include Ranger Tugs, Florida Bay, American Tug, Nordic Tug and Tugboat. They make inboard, outboard, outboard-4S, and other diesel and gas fuel propulsion systems.

Tug boats are known for their moderate draft and broader beam, making them suitable for various commercial and recreational boating activities in coastal, inshore and offshore locations. Tugboats can carry about 6 to 8 passengers or guests.

Table of Contents

Applications Of A Tug

The usage and functions of tugs vary from port to port, as different ports have different requirements and intakes. The common thing is pushing or towing mega boats or barges. Their usage depends on the following factors:

• Port traffic volume,
• Types of ships to be served by that tug,
• Navigational obstacles to be catered to,
• Conditions of environmental protection,
• Local laws and
• Domains to be carried by a tug

The tug boats were among the first to have a steam propulsion engine, which the diesel engine has replaced today.

An average tug boat has 680-3400 horsepower engines (500-2500 kW), but those which are larger and venture out into deep waters have engines with a power close to 27200 hp (20000 kW) and a power: tonnage ratio ranging between 2.20-4.50 for large tugs and 4.0-9.5 for harbour tugs. These are incredibly high ratios, especially considering the ratio of cargo ships or vessels varies between 0.35 and 1.20.

Since a tug boat’s manoeuvrability is one of its assets, all engine developments have focused on improving it without compromising the vessel’s strength and power over the years. Thus, the transition from paddle wheels to propellers.

Classification Of Tugs Based on Purpose

Based on purpose, they serve marine tugs can be of two types:

1. Escort Tugs: The tugs designed generally to escort and manoeuvre ferries and barges to their destination are known as escort tugs.

2. Support Tugs: These tugs provide support services for offshore and towing operations. These tugs play a significant role in berthing operations.

Mainly, tugs used in the marine industry are of three types, which are listed:

• Conventional tug
• Tractor tug and
• Azimuth stern drive tug

1. Conventional Tug

These are the tugs we have been using since the start. They are made using the oldest known principle of tug development. The conventional tug has less manoeuvring capability but is still used in almost all ports worldwide.

With technological advancements, tugs are fitted with diesel engines with either one or more propellers. Single propeller tugs are classified into right-handed conventional and left-handed conventional tugs.

Right-handed conventional tugs are more common and likely to be used than left-handed ones. These are highly reliable.

The essential components of conventional tugs are briefed as follows:

• These have a classic rudder.
• A towing hook is provided in the centre of the tug. Along with other components of tug positioning, a hook is of enormous importance. The safety and performance of the tug boat mainly depend on the towing point location. When a gob line accompanies the towel hook, this point can be taken towards the aft; its distance is reduced from its original value of 0.45 times LWL to minimise tug manoeuvring.
• Its stern consists of the power plant complex.

Configuration of propeller used

Screw propeller — In the “conventional” tugboat, the propelling device is generally diesel driven. The propeller develops thrust in water and is responsible for ships’ movement. These tugboats are designated based on several propellers in them:

• Single screw tug implies one conventional propeller tug,
• Twin-screw tug implies a two-propeller traditional tug and
• A triple screw tug implies three classic propeller tugs.

In conventional screw propeller tugs, a moveable nozzle and rudders are provided, but the whole propeller is immovable or fixed.

The main advantages or features of conventional tugboats are as follows:

• The construction of traditional tugs is quite simple and requires less maintenance, so the maintenance and construction costs of these tugs are meagre compared to the two types of tugs.
• These are self-sufficient and thus require no support system.
• The smaller the propeller, the larger the open water.
• These tugs have the upper hand and maximum efficiency in towing for port-to-port.
• These assist with pushing and tugging operations while carrying towing on a line.
• The operation cost is relatively low and economical while working with moderate-sized vessels.

Disadvantages

There may be certain disadvantages of conventional tugboats, and these are briefed as follows:

• The design principle is ancient; thus, it degrades performance standards.
• They are unidirectional and cannot work in the reverse direction until provided with a reduction gear to facilitate reverse flow.
• There are more chances of cavitation in these tugs.
• These tugs’ stability and strength are less than the other two.
• Due to obsolete design principles, their usage is limited to small and medium boats, so azimuthal stern drive and tractor tugs are employed to assist the mega ships.
• The repositioning of the tugs is relatively slow due to the limited manoeuvring capacity.
• There are more chances of capsizing or overturning the vessel, which results in fatal accidents. A release hook is required to overpower this issue of capsizing and halting the development of girthing.
• Conventional tugs have low values of astern power

2. Tractor Tug

The key to the tractor lies in using a 2-multidirectional propulsion unit, some of which are like large rotating outboard motors, with others consisting of rotating vertical blades.

They enable the tug’s thrust units to be placed side by side, more or less under the bridge, facilitating spectacular manoeuvrability in the right hands.

The towing point can be placed much nearer the stern to get maximum output from the propulsion units, and therefore, the thrust is always outside of the towing point, thus creating a joyous turning moment.

The rotating disc decides the magnitude of the force of thrust. Tractor tugs’ versatility is further enhanced by working the tug’s towline directly from a winch drum with a remote joystick controlled from the bridge. The tug master can thus alter the span of the towline at his will and with considerable ease. Their precision in manoeuvring makes them the most widely used tugs.

Advantages:

It is the most critical type of tug, and a tractor tug has many positive points. Some of its advantages are briefed as below:

• These are the only tugs which provide full thrust over 360 degrees.
• They have rapid power-on response time and are well known for their outstanding manoeuvrability.
• In contrast to conventional tugs, tractor tugs are adaptable to repositioning swiftly at the pilot’s will or on demand of the towing job in which they are employed. Thus, they are readily available tugs with high-efficiency values.
• Their straightforward control systems pose a shallow risk of girthing or capsizing.
• These have extraordinary performance and fast speed.
• They can effectively overcome the forces of interaction with ships at close distances.
• They can work efficiently in sideways movement due to the close location of the propulsion unit to the turning point.
• They have improved operational capability in restricted areas such as a lock flow channel.
• In these types of tugs, a rudder is not required, and the use of a rudder can be eliminated.
• They have reliable and robust propulsion units.

Tractor tugs are the most effective and potent sort of tugs. As everything has specific cons and pros, these have certain loopholes, mainly their complexity and cost. Other drawbacks of these tugs are as follows:

• These kinds of tugs have less bollard pull than ASD tugs.
• They are considered to have very high capital investment costs, implying a lot of money is required to buy and maintain these tugs. In short, it confers that the initial and maintenance cost of tractor tugs is very high.
• The repair and maintenance of complex under-water units of these tugs are pretty expensive
• Handling in an open seaway might be poor with the short distance between the pivot point and the thrust creating a short turning lever
• Heeling angles with full side thrusts may be up to 21 degrees with some tugs. Therefore, the risk of damage can exist when lying alongside a ship
• Sophisticate under-water units may be damaged on grounding
• A draft may be up to 5m, which is significant in comparison to conventional tugs
• The retraining of a traditional tug master is essential to maximise a tug’s potential fully

3. Azimuthal Stern Drive (ASD) Tugs 

These tugs are midway between conventional and tractor tugs as these utilise some of the benefits of both traditional and tractor pulls. It can have two towing locations, one forward and one amidship, and the main propulsion is from two rotating azimuth units, which are placed like a traditional twin screw tug.

These are considered more efficient than conventional tugs but less efficient than tractors. The significant advantages of using ASD tugs are as follows:

• Better directional stability at speed
• They are more suitable hull form for open waters and working in a seaway
• They have improved the bollard pull
• The azimuth units are easy to withdraw for maintenance and repair
• The maximum heel with side thrust is less than 15 degrees, compared to tractor tugs, which have a twenty-one-degree value.
• These tugs have a shallower average draft of 3m

These tugs are challenging to work with as compared to tractor tugs, and other drawbacks of working with these tugs are as follows:

• The side-stepping ability of ASD tugs is not so good.
• The squat at the stern and flooding of the aft deck have been acquainted with certain types when backing with full power.
• They are still susceptible to girting or capsizing when using the aft towing position.
• These types of tugs are slightly more at risk from the interaction effects.
• These have somewhat Complex control systems.
• These tugs are more susceptible to rubbish damage in propellers
• It is not uncommon for 99 % of all towing to be limited to a forward position

Other Miscellaneous Types Of Tugs

Along with these classifications mentioned above, some other miscellaneous types of tugs are briefed as below:

1. Tractor Tugs With Cycloidal Propellers

Before the Second World War, tugboats had high power ratings and large tonnage capacities, and the propeller used was cycloidal to facilitate manoeuvrability; these were renowned as Cycloidal Tugboats. Voith Schneider propeller (VSP) is an advancement of a cycloidal drive. It is excellent at manoeuvring operations, so it became a perfect choice for ferries and barges.

2. The Carousel Tug

The Dutch developed the Carousel Tug, which emerged as an award-winning Maritime innovation in 2006. It consists of interlocking inner and outer rings, the former connected to a vessel and the latter with the tug’s body attached to a towed ship through winches or hooks.

3. Reverse Tractor Tugs

The tractor tugs are termed reverse tractor tugs if they have Z-drive aft-mounted propulsion units. These reverse tractor tugs don’t have a skeg and work efficiently in escorting. These tugs have fewer fatigue issues than tractor tugs due to the unavailability of flat plate skeg. Generally, ASD tugs serve as reverse tractor tugs.

4. Combi-Tugs

A bow thruster and a nozzle with steering are fitted with a conventional Screw Tug to improve manoeuvrability. These modified tugs, along with additional devices like a thruster and steered nozzle, equipped with the latter devices are referred to as “Combi-Tugs”. Combi-Tugs are preferably modified with twin-screw conventional tugs to have maximum efficiency.

5. Z-PELLER

It can have two towing locations, one forward and one amidship, and the main propulsion is from two rotating azimuth units, which are placed like a traditional twin screw tug. Azimuthing propulsion unit replaces conventional shafts and propellers, which allows 360-degree rotation about the vertical axis.

6. Giano Tug

The Giano Tug is highly stable and can serve the purpose of both support and escort tug. It is a high-tech tug which allows remote manoeuvring through VSAT or 4G connections. Its 360-degree rotation and excellent side-stepping speed made it to the top in the order of standards of tugs.

7. Eco-Tugs

Hybrid technology tugs or tugs with LNG as a running fuel are categorised as eco-tugs. These tugs serve the same purpose of escorting and supporting as the conventional tugs, but without harming and polluting the marine ecosystem.

8. Ice Tugs

These tugs escort ferries or barges and serve as icebreakers or salvage boats to make the ferries and barges speed up to their destination.

The Most Powerful Tug in the World

“The title of most powerful tugboat crowns Farstad Shipping’s Far Samson by the Guinness World Record, which achieved an astounding four hundred twenty-three tons bollard pull during testing.” The Spanish shipyard launched a groundbreaking, powerful tug boat to supply the Luleå, Sweden Port.

But presently, Gondan Shipyard promises to build and deliver an ice-breaking towing tug, which is assumed to bag the ticket for the most potent hybrid tug in the World.

Robert Allan’s design was the foundation for building this tug. To assist ships or vessels through challenging regions, it employs a powerful hybrid power system, namely Wärtsilä’s HYTug power system. It combines “Lloyd’s Register class and a 3600-H design of RAL TundRA”.

All the super, as well as substructures of this giant, are very strong and efficient. The superb hull structure is provided, which beats even the class rules of Finnish-Swedish ice. The excellent bollard pull of this tug of about 100 tonnes emphasised its capabilities. It is operated in a diesel manual mode to achieve maximum efficiency.

These can easily break a metre of ice with a comparatively high speed of about three knots. The tug’s thirty-six-metre span is equipped with an excellent propulsion system. Its propulsion system comprises batteries to store energy and run in specific emergencies, shaft motors, generators, two diesel key engines, etc.

The essential features of this tugboat are as follows:

• It is flexible in operation and can switch swiftly.
• It emits less fuel under its hybrid conformations, making its maintenance economical and more accessible.
• There are a variety of operation modes available in this tug due to its innovative and hybrid design.
• It can serve multi-purpose purposes in ice management, assisting ships and enormous barges during voyages, fighting fires, and towing in coastal regions and difficult conditions.

You might also like to read:

• A Guide To Types of Ships
• Types of Sailboats: A Comprehensive Classification
• Different Types of Submarines and Underwater Vessels
• Different Types of Barges Used in the Shipping World
• LNG Tankers: Different Types And Dangers Involved

Disclaimer:  The author’s views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight.

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About Author

Zahra is an alumna of Miranda House, University of Delhi. She is an avid writer, possessing immaculate research and editing skills. Author of several academic papers, she has also worked as a freelance writer, producing many technical, creative and marketing pieces. A true aesthete at heart, she loves books a little more than anything else.

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Not only a dirty job, but one of these most dangerous too. They work with cables that are under huge amounts of strain and could snap. Hat tip to all the tug boat crews out there, helping ships in their time of need.

I am engineer Ali Abusada from Libya I was the chairman of Libyan to wage and selvage company now I am consulting engineer for the company , we are looking for getting new tugboats of 5000hp 4500 hp 300 hp. I need to know where we can find chance in Mediterranean

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Everything You Need to Know About Tugboats, Their Types, and Their Uses

Tugboats – Their types and uses

Tugboats are an indispensable part of the global shipping industry, facilitating the safe passage of large ships through narrow channels, busy stretches, and shallow water, as well as performing several other vital duties, including firefighting and marine salvage.

You’ll find tugboats being used in all manner of industries worldwide, from the cruise industry to the oil industry. Quite simply, without tugboats, the entire maritime world would come to a grinding halt.

But what are tugboats? How do tugboats work? And what are the different tugboat types? You’ll find out the answers to these questions and much more when you read through everything we’ve got to say below.

What is a Tugboat?

The most basic question to answer on this page is what are tugboats? In simple terms, a tugboat is a vessel designed to manoeuvre other vessels by pulling or pushing them. This movement can be facilitated via direct contact between the tug and the other vessel or by using tow lines.

But why are these tugboats needed? They’re needed because larger ships can’t turn sharply at low speed, as insufficient water passes over the rudder to facilitate quick turning. Tugboats are therefore used to push and pull ships into position, such as into designated berths at ports.

However, not all tugboats are used in the way described above, as some tugboats are now used for roles not relating to the movement of vessels. For example, some tugs have been designed for search and rescue operations, while others are specially adapted to act as ice breakers.

Nowadays, most tugboats have two diesel engines. These are exceptionally powerful and can generate over 6,000 horsepower between them. However, electric tugs have recently started to be used, with the first being deployed in Istanbul in 2020. These are slightly less powerful than other tugs but are necessary for use in areas with environmental requirements.

But who works on the tugs? The average tugboat used to navigate ships in and out of port has several types of workers. The captain is in charge of the vessel and must have the necessary qualifications to haul specific tonnages. Mates work under the captain and are second in command, while engineers are required to ensure the tugboat functions correctly at all times. Some tugboats also have a crew of deckhands.

So, to recap, a tugboat is usually used for navigating larger ships by pushing or pulling them into position, although they can also have many other jobs. They’re mainly powered by diesel engines and are manned by several crewmen, all under the overall command of a tug captain.

Anyone looking to gain use of a tugboat has two options. They can either purchase one, which often means spending a large sum, or they can hire a tugboat. Ship chartering represents the most cost-effective option for most.

Bollard Pull: The Measurement of Pulling Power

Bollard pull is a measurement used to determine the pulling power of a vessel, so as you can imagine, it is exceptionally important for tugboats. A more technical definition of bollard pull would be the thrust developed by a vessel’s propulsion systems at zero ahead speed.

There are two types of bollard pull: static bollard pull and continuous bollard pull. The static bollard pull is measured shortly after the start of the test, when full power is possible thanks to the still water. The continuous bollard pull is then measured over 10 minutes.

The bollard pull of tugs and other vessels is calculated in kilonewtons (kN) or occasionally in different units of force like tonnes of force (tf) or short tons (stf). The average medium-sized tugboat has approximately 500-600 kN of bollard pull.

Every vessel that’s required to pull a load must have a bollard pull certificate from one of several classification societies, such as the Indian Register of Shipping (IRS) or the American Bureau of Shipping (ABS).

Importance of Bollard Pull

The bollard pull of a tugboat is exceptionally important, as without the figure, it’s impossible to work out whether a tugboat has sufficient power to navigate a specific ship safely. If the bollard pull is not known, tugboats could be deployed that don’t have the necessary power to bring a large ship to a halt or manoeuvre it quickly and accurately.

How to Calculate the Bollard Pull

To calculate the bollard pull of a vessel, the vessel is anchored to a pier using a bollard. The vessel then propels itself forward at maximum thrust, and the tension measured in the towline shows the total thrust achieved.

The bollard pull test can’t be carried out in all conditions. Instead, a few criteria must be present for the bollard pull test to be accurate. The most important are:

• Undisturbed water
• Enough clearance around the vessel
• An unhindered propellor wake and stream

It should be remembered that perfect conditions are rarely found. Therefore, the results of the test must have some margin of error.

It is also possible to calculate bollard pull using computational simulations. However, these are expensive, and few facilities can run the simulations.

How to Increase Bollard Pull

As you might imagine, the bollard pull of a tugboat is a significant selling factor. Therefore, manufacturers do all they can to design tugboats with the highest possible bollard pull. There are several ways the bollard pull can be increased, including:

• More powerful engines
• Increased number of engines
• Make the vessel design more streamlined to minimise resistance

It should also be mentioned that sellers of tugboats sometimes unscrupulously alter their vessel’s bollard pull score to make it more appealing to buyers. However, buying or renting from reputable companies all but eliminates the possibility of this.

Is Bollard Pull Always Accurate?

Bollard pull is never going to be completely accurate, and this is because conditions are never perfect. For example, the test might be carried out when the bollard and vessel are not perfectly horizontal with each other, or when the water isn’t perfectly calm.

Propellors also regularly yaw vessels to one side slightly, affecting the accuracy of the bollard pull calculation. Even the salinity of the water will influence the accuracy of the test.

To obtain the most accurate results possible, bollard pull tests should be carried out in deep water and away from the mouth of a river. They should also be carried out on a calm day, with minimal traffic in the area.

How Do Tugboats Work?

Tugboats generally work in one of three ways: direct towing, indirect towing, and pushing. Each is used in specific situations and has its unique advantages. Find out about them below.

Direct Towing

This is the simplest type of towing. Quite simply, a towing line attached to a powerful motor is fastened to the vessel being towed. The tug then pulls the ship through the water. This is often used when the vessel is not able to propel itself. Generally, this type of towing happens at low speeds, typically 4-5 knots, and is governed by the bollard pull of the tug.

Indirect Towing

Indirect towing is another way of manoeuvring ships using a tow rope, but it differs considerably from direct towing. In this type of towing, the tow rope is attached to the vessel’s stern, which drags the tug. The tug uses thrust to keep a sheered position in relation to its heading, which allows the drag force to be higher than the bollard pull of the tug. Using this method provides more force when turning or decelerating. It generally happens at speeds of 6 knots or greater.

Most commonly used in North America, pushing is exactly what it sounds like. The tugboat pushes the vessel into position, using its impressive power to reposition ships many times larger than itself. Pushing tugs often have an attachment that fits into a specific receptacle of the vessel being pushed, plus tugs of this type are generally built with reinforced hulls.

Types of Tugboats

In general, there are two types of tugboats – escort tugboats and support tugboats. Below, you can find out a little about these two types of tugs.

Escort Tugboats

Tugs of this type are the most recognisable, as they manoeuvre and escort vessels in dangerous and coastal waters. The escort tug is required to assist with the steering and stopping of large ships, plus they can also perform routine towing tasks in harbours.

An escort tugboat must have an optimum speed equal to or greater than the maximum speed of the vessel being moved, and it must also be able to carry out duties while moving at these top speeds.

Support Tugboats

Support tugboats, as their name suggests, provide support to towing operations. They are primarily used to assist with berthing and unberthing and don’t carry out the heavier work done by escort tugboats – although support tugs are capable of tethered towing of smaller vessels. They can also be used for untethered towing.

It is also possible to find offshore support tugs designed to support offshore operations, such as oil rigs, working in deeper water compared to regular support tugboats. As per regulations, all support tugboats can be used for firefighting purposes.

Tugboat Design

Tugboats generally use three designs: conventional, tractor, and Azimuthal Stern Drive. Each of these has its advantages and disadvantages, which we discuss below.

Conventional Tugboats

As the name suggests, tugs of this type are the way they’ve been for years, created using age-old principles. This makes them relatively easy to construct, plus they also require less maintenance than other tugboat designs. They also have a much lower operational cost, making them the economical choice. What’s more, they’re completely self-sufficient.

Tugs of this type can assist with pulling and pushing, but they are not suitable for on the line or indirect towing due to their lack of manoeuvrability – something that also limits their ability to reposition themselves. Conventional tugboats are less powerful than the other two types of tugboats mentioned on this page, and performance is further affected by the dated design principles used.

It should also be mentioned that conventional tugboats have more chance of capsizing, making them the most dangerous type of tugboat. A release hook is used to mitigate against this issue. Despite the many drawbacks to conventional tugboats, they are used in most ports worldwide.

Tractor Tugs

Tractor tugs are the newer style of tugboats and are named after the traction their propulsion systems manage to achieve when pushing or pulling. This propulsion unit is multidirectional and gives tractor tugs tremendous manoeuvrability. The towing point is placed close to the stern, which allows the propulsion units to work optimally.

Tractor tugs can reposition themselves quickly, making them highly versatile, plus they have a high top speed. They’re the best choice in restricted areas and far less susceptible to capsizing, mainly thanks to their straightforward controls.

However, this design has a few downsides, such as the high purchase costs – which is why many instead look for tractor tug boats for hire – and the lower bollard pull compared to ASD tugs. Retraining of a tug master is also required to gain maximum use from a tractor tug.

Azimuthal Stern Drive

Azimuthal Stern Drive tugs – usually abbreviated to ASD – are a mid-point between conventional tugs and tractor tugs. They get their name from the two azimuth units which provide most of the tug’s propulsion. These are placed in the same way as a twin screw tug. ASD tugs can have two towing locations – one amidship and one forward.

In terms of efficiency, they are better than conventional tugs but not as efficient as tractor tugs. They are the most suitable tug type for working in open waters and seaways, thanks to their hull form, plus they can offer a large bollard pull. The average draft of these tugs is 3 metres, plus the maximum heel with side thrust is under 15 degrees – much lower than the 21 degrees of tractor tugs.

Even the most experienced tug masters will find ASD tugs to be challenging at first, mainly down to the complex control systems onboard. They can also be susceptible to capsizing or girting when using the aft towing position.

Uses and Applications of a Tug

While tugs are mainly used for the manoeuvring of ships, they also have various other uses, all invaluable to the maritime industry. We’ve listed some of the main tugboat types below, so you can see exactly how widespread their use is.

Ice Breaking

Ice-breaking tugs are used to clear a passage of ice, breaking up the ice by impacting it. Many ice-breaking tugs can also push and pull vessels. These tugs are built to be solid – they have unique hulls that can withstand heavy damage, plus the hulls are designed to resist metal embrittlement.

Tugs of this type usually use a twin-engine screw propeller with a Kort nozzle. This non-rotating nozzle can increase thrust by up to 90%, providing the extra power necessary to break through ice. Ice breakers also usually have lower freeboards thanks to the extra scantlings used.

Salvage/Search and Rescue

Marine salvage tugs are generally used to recover grounded ships or apply measures to stop them from sinking. They’re also regularly used for search operations when distress calls are received. Tugs of this type are usually tractor tugs and are manned by specialist crews.

Tugs used in this sphere of work are highly specialised, boasting many extra pieces of equipment. These can include specialised winches and high-powered pumps. They are also usually equipped for dredging operations, where they remove sediment and foreign objects from water channels, ensuring ships can pass through unhindered.

Towing and Workboats

The primary use of tugboats in ports, tugs of this type offer assistance in braking and steering to larger vessels navigating particularly challenging passages. Most tugs of this type have been adapted to offer both pushing and pulling capabilities.

It’s nearly always the case that tugs of this type use Azimuth Stern Drive propulsion systems – you can find out more about these later on this page. They are also often twin-engine powered to provide the extra power needed for operations.

Firefighting

Firefighting is something that every tugboat must be equipped to carry out, as per SOLAS regulations. This means that every tug can carry out basic firefighting duties. However, there are also specialised firefighting tugs operated by qualified firefighting crew, which are stationed strategically to ensure reports of fires can be responded to quickly.

As you might expect, specialist firefighting tugs are equipped with all the features necessary to fight A, B, and C-type fires effectively. These include high-powered pumps, as well as hose lines and specialist retardant materials. They often work with tractor tugs in situations where emergency towing is required.

Anchor Handling

These are exceptionally powerful tugs, often with three engines to increase bollard pull, which deploy, retrieve, and relocate anchors potentially weighing several tonnes. They work in deep water and many miles from any assistance, and as such are required to be self-reliant, able to deal with emergencies if they arise.

These tugs are mainly used to handle anchors for oil rigs, towing them to the necessary location and securing them. They also often undertake supply duties, provide towing help, and move dangerous objects from specific areas.

Ocean Towage

Ocean towage tugs are specialised vessels designed to handle long-distance towing operations, such as towing floating production units and drilling rigs. As you’d expect, they’re fitted with all pulling equipment necessary to perform optimally and are high-powered. Many tugs of this type are also equipped to deal with regular towing jobs.

Ocean towage jobs often take over 24 hours to complete, and the tugs head into deep, open water, meaning they must be specially modified for safety and effectiveness. One vital modification is a large fuel tank to make long journeys possible.

Yarding tugs are smaller than the average tugboat and only have moderate power. Because of this, they are only used for lighter towing activities, with the movement of dumb barges being a particularly common role for these tugboat types.

A single crew member can often operate tugs of this type. Because they are smaller and have less power, they have limited usage within larger ports, where giant vessels are regularly found. Larger tugs, which can also carry out yarding duties and other roles, are often preferred.

Line Handling

Line handling tugs are the least powerful and smallest of all tugboats and have very limited usage. Tugboats of this type are not strong enough to carry out pushing and pulling tasks and instead support larger tugboats, securing the hawser line of ships to facilitate the towing operation.

Tugs of this type can only be used in ports and sheltered waters. They’re often only powered by an outboard motor, although slightly more powerful line handling tugs can also be found. Like all other tugs, they have firefighting equipment and can also be used for oil spills and emergency response.

Survey and Research

Tugboats of this type are specially equipped to carry out many types of surveys and research, including, but not limited to: marine biology research, seismic activity research, hydrographic surveys, and oceanographic research. Tugs of this type must be able to spend extended periods away from shore, plus they need to be able to handle the conditions of many environments.

This type of boat is not technically a tugboat, but the construction utilises many similar principles. They are usually equipped with highly specialised instruments, some of which might be installed in a drop keel, plus they often boast highly advanced radar mapping capabilities.

Tugboats with the primary goal of patrolling an area of water are mainly used by the emergency services, namely the police and coast guard, as well as by disaster rescue operators. They’re also used by those with a need to patrol a harbour.

Tugboats for patrolling are built with speed in mind, and crafts of this type can reach speeds of 40 knots. Patrol boats operating between 20-35 knots often have a water-jet propulsion system fitted, although fitting one can cost large sums of money.

Tugboats of this type are specifically designed to transport personnel and cargo, usually to places such as oil platforms and drilling rigs. They range wildly in size – some are just 30-foot vessels that work in bays and inland waterways, while others are large 200-foot vessels capable of working hundreds of nautical miles from shore.

The capacity of crew boats differs from vessel to vessel, with the largest crew boats being capable of transporting up to 100 passengers, usually in airline-style seating. They typically have a higher GRT, plus they often have considerable space on deck. As they carry passengers, they’re generally designed to offer some level of comfort.

How much does a tugboat cost?

The price of purchasing a new tugboat can vary wildly – some can be bought for around $750,000, while at the other end of the scale, they can cost upwards of $10 million. When well-maintained, tugboats retain much of their value but purchasing second-hand is usually far more cost-effective. However, the cheapest way to gain use of a tugboat is to charter one.

What is it like to travel on a tugboat?

This depends on the type of tugboat being travelled on. Some tugboats are specially designed to carry passengers comfortably, while others are designed to be more practical and focus less on comfort.

Why is it called a tugboat?

As ships became larger and larger, there was the need to assist them when coming into port – the large ships simply didn’t have the manoeuvrability to do it on their own. This was solved by using small boats to provide something called a tug assist. The boats themselves soon became known as tugboats.

How powerful is a tugboat and how come it is able to tow large ships?

Tugboats vary in power, with the average tugboat having a bollard pull of 400-500 kN. This is a tremendous amount of power compared to their small size, and this is primarily caused by the mighty engines used. Also, several tugboats are sometimes used to move a large vessel.

Final Thoughts

As you can see, tugboats are a vital component of the maritime industry. Without them, large ships would find it impossible to navigate specific stretches of water, plus many essential roles, such as firefighting and marine salvage, would remain unfilled. You’ll spot tugboats in every port, and the fact that they’re ubiquitous only underlines further their importance.

Have you enjoyed reading this post? Has it given you a better insight into tugboat types and how they work? Let us know what you think in the comments below, and, as always, if you’ve liked reading this article, please share it with friends, family, and colleagues.

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Swell Cruise Ship, Alaska

• from $ 911 / day

• Converted tugboat with classic charm
• Wood-paneled salon and charming lounges
• Get up close to incredible wildlife

Look no further than the Swell yacht for a fantastic small-ship adventure cruise in Alaska. She is a classic converted tugboat accommodating up to 12 guests in 6 private en-suite cabins. A $4-million refit means she offers amenities found on no other ship in her class in the region. The spacious wood-paneled salon offers a charming place to relax, read a book or play a quiet game. During meal-times, the salon is set up as a dining room so guests can enjoy the delicious onboard cuisine, snacks, and drinks available. There are two Aft Deck lounges: one on the main deck, an enclosed space perfect for enjoying the stunning surrounding views. The upper deck aft lounge has comfortable sofas and a semi-covered hot tub.

Itineraries aboard the tugboat Swell explore the best of Alaska's Inside Passage. Cruise through Fredrick Sound, Endicott Arm, Tracy Arm, and Baranoff Island on a 9, 10, or 11-day cruise to get up close to incredible wildlife. Brown bears, humpback whales, sea otters, icebergs, glaciers, and historic towns are all on the agenda creating a small-ship Alaskan cruise to remember.

Book online today for an adventure of a lifetime aboard the tugboat Swell.

Choose your departure date adventure cruise | no scuba diving

Included: VAT, Fuel Surcharge, National Park Fees, Port Fees, Visas and Fees, Alcoholic Beverages, Drinking Water, Soft drinks, Tea & Coffee, Wine with Dinner, Beach BBQ, Full-Board Meal Plan (All meals), Snacks, Kayaks, Land Excursions, Naturalist Guide, Cabin Towels, Complimentary Toiletries, Deck Towels.

Required Extras: Environment Tax (200 CAD per trip).

Optional Extras: Gratuities.

Book now, pay later: You can easily place your booking online. We will then hold the spaces for you and you can confirm with a payment later.

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Boat features

• Daily housekeeping
• Indoor Saloon
• Warm Water Showers
• En-Suite bathrooms
• Non-Smoking Rooms
• Seaview Cabins
• Kayaks On-Board
• Dedicated Local & International Crew
• Nearly 1:1 Crew-to-Guest Ratio
• Naturalist Guide
• Observation Deck
• Available for Charter
• Jacuzzi / Hot Tub

Food & Drinks

• Western Food
• Vegetarian Options
• Snacks All Day
• Free Wine w/Dinner
• Vegan Options
• Fine Wines Selection
• Free Soft Drinks
• Set Menu Dinner
• Fine Cuisine

If you have any specific dietary requirements whilst on-board your cruise, you can add this to your special requests on step 2 of the booking form. We advise limiting these requests to religious beliefs or food allergies.

Languages Spoken

The crew speaks English.

Drawings & Vessel Layouts

Accommodation.

Cat 3: Cedar

Cat 3: Douglas Fir

Cat 2: Arbutus

Cat 2: Sitka Spruce

Cat 2: Western Hemlock

Cat 1: Red Alder

Boat specifications.

• Year built 1912
• Year renovated 2004
• Length 88 ft
• Deck area 2 covered
• Beam 20.6 ft
• Top speed 9 knots
• Cruising speed 8 knots
• Max guests 12
• Number of cabins 6
• Number of bathrooms 6
• Freshwater maker yes

Boat Navigation and Safety

• Depth Sounder
• Radio VHF/DSC/SSB
• E.P.I.R.B. Distress System
• Emergency Rafts
• Fire Alarm & Fire Extinguishers
• First Aid Kits
• Satellite & mobile phones
• Bilge pump alarm
• Search light
• Crew trained in first aid
• Emergency flares

We’re here to help, 24/7.

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• 1 double bed
• 120 sq. ft.
• Aircon with control
• Ensuite Bathroom
• Max 2 guests

Largest cabin. Outside door, opening portholes with large private, 3-piece ensuite head, natural light. Small boat queen-sized bed, which is half-way between a double and a queen (75.5” x 57”). Walls on three sides of bed. Storage in a tall, slim cupboard, various drawers, one shelf, and small entry shelf.

Largest cabins. Outside door, opening portholes with Large, 3-piece private ensuite head, natural light. Small boat queen-sized bed, which is half-way between a double and a queen (75.5” x 57”). Walls on two sides of bed. Storage in tall, slim cupboard, various drawers, shelves.

• 2 single beds (twin)

Outside door, opening porthole with private ensuite head, separate washbasin area, natural light. Upper and lower singles. Storage in three small cupboards, two large drawers below lower bunk and two shelves and a desk.

Outside door, opening porthole with large, 3-piece private ensuite head. natural light, skylight. Angled boat double beds (approx 79” x 52”, narrower at feet). Comfortable beds for two people used to sleeping together and don’t mind their feet near each other. Not for people who wish to sleep well separated from their partner. Luxurious for a single paying a single supplement. Storage in three small drawers, two cubbyholes under the bed, and three shelves, plus cupboard in the head.

• Central aircon

Outside door, opening porthole with large, 3-piece private ensuite head, natural light, skylight. Angled boat double beds (approx 79” x 52”, narrower at feet). Comfortable beds for two people used to sleeping together and don’t mind their feet near each other. Not for people who wish to sleep well separated from their partner. Luxurious for a single paying a single supplement. Storage in three small drawers, two cubbyholes under the bed, and three shelves, plus cupboard in the head.

Outside door, opening portholes with private ensuite head, separate washbasin area, natural light, skylight. Two up and down small, extra-long single beds (79.5” x 30”). Storage in tall cupboard with shelves, small under-sink cupboard, under bed.

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MV Swell Review

Imagine cruising through pristine surroundings, coupled with the thrill of spotting wildlife, in the company of a handful of companions. The joys of cruising with Maple Leaf Adventures on a small ship -- really small, as in only 12 passengers -- happen as frequently onboard as on shore. Ashore, it's all about nature. Onboard MV Swell, life centers around whale spotting, socializing and getting to know your fellow adventure seekers, as well as your crew of four or five friendly Canadians.

A classic wood-hulled, coal-fired tugboat, MV Swell was built in 1912 in Vancouver, Canada. Measuring 80 feet long and 22 feet wide, the tug originally worked the British Columbia coast for the Victoria Tug and Barge Company. In 1954, Swell's power was converted to a diesel engine. In 2004, the tug was refitted as an expedition vessel at a cost of $3.5 million. After serving as a dive boat, Swell received an update to its interior decor and joined the Maple Leaf Adventures fleet in 2015.

The Inside Passage itineraries -- both in British Columbia and southeast Alaska -- are flexible and depend on tides, weather and wildlife sightings. The captain stops for whales, bears and anything else passengers express a desire to see up close. Each day, the proposed schedule is posted on a whiteboard in the dining room. Plans are updated as things change, and you quickly learn to go with the flow. Consequently, no two cruises are ever the same. At night, Swell anchors in a secluded cove for peaceful sleeping. Even better, the generator is switched off. Power is provided by a silent battery backup system. No noisy engine. No annoying bright lights. Just twinkling stars and the sounds of nature until the generator is turned on again at 6:30 a.m.

The tug's seasonal travels (late April through October) include spring coastal cruising along Canada's Vancouver Island and Haida Gwaii (formerly Queen Charlotte Islands), islands that are significant to First Nations people. During summer in Southeast Alaska, Maple Leaf Adventures is one of the few permit holders with access to the brown bears of Pack Creek on Admiralty Island, one of the world's densest brown bear populations. Following Alaska, Swell returns to British Columbia for fall cruises to the Great Bear Rainforest with the chance to see a spirit bear, a rare black bear born with white fur. Cruises range from four to 10 nights. Fares include all excursions.

Bottom Line

Fellow passengers.

The majority of passengers are Canadian and American couples in their 60s and 70s. To get the most from the cruise, passengers must be fit and able to climb into and out of Zodiacs (rigid inflatable boats) and hike over rugged, wet terrain. Cruisers with certain pre-existing medical conditions are required to have a physician sign a release indicating fitness for travel in wilderness areas. The single supplement, when available, is 50 percent more than the double-occupancy rate. Announcements are in English.

Maple MV Swell Dress Code

Day or night, the dress code is casual. After all, you need to be dressed and ready for spontaneous wildlife viewing. Also, with limited cabin space, storage is at a premium for foul-weather gear instead of dressy duds. Passengers are asked to pack only soft duffle-type bags. In several cabins, there is no spot to stow a wheeled or hard suitcase. Fortunately, Maple Leaf Adventures provides knee-high rubber boots needed for wet Zodiac landings, making for one fewer bulky item to pack. Bring rainproof pants and a rain jacket for hiking through the rain forest.

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VIDEO: Tug Boat Pushed Under Water by Norwegian Escape

Watch here how a tug boat was pushed under water by Norwegian Escape during ship's conveyance from shipyard to the North Sea in October 2015.

Launched in 2015, Norwegian Escape is the first of the three Breakaway Plus-class newest and biggest NCL ships – together with  Norwegian Joy  (2017) and  Norwegian Bliss  (2018). This class ships are approx 7000 GT tons larger in comparison to the previously biggest vessel of the line,  Norwegian Epic . The NCL Escape ship cost USD 920 million to build.

Tugboats: The Unsung Heroes of the Shipping Industry

Tugboats are a type of vessel that is primarily used for towing other ships and barges. They are commonly found in harbors, ports, and other waterways where large ships need assistance maneuvering in tight spaces or difficult conditions. These powerful boats are designed to provide the necessary force to move much larger vessels and are an essential part of the maritime industry.

Tugboats come in a variety of sizes and configurations, each with its unique capabilities and features. Some are designed for use in open water, while others are specifically designed for use in harbors and other confined spaces.

They can be powered by a variety of engines, including diesel, electric, and hybrid systems, and are often equipped with advanced navigation and communication technology to ensure safe and efficient operations.

Despite their important role in the maritime industry, tugboats are often overlooked by the general public. However, these hardworking vessels play a crucial role in ensuring the safety and efficiency of shipping operations around the world. In this article, we will take a closer look at the history, design, and uses of tugboats, and explore the many ways in which they contribute to the global economy.

Tugboats have been an indispensable part of maritime transportation for nearly 200 years. They maneuver larger watercraft in tight areas and tow unpowered vessels from port to port. In this section, we will explore the early development and modern developments of tugboats.

Early Development

The history of tug boats dates back to the early 19th century when steam-powered boats began to replace traditional sailing vessels. The first steam-powered tug boat, named Charlotte Dundas, was built in Scotland in 1801. It was used to tow barges along the Forth and Clyde Canal in Scotland.

In 1736, Englishman Jonathan Hulls patented a boat powered by a Newcomen steam engine to move large vessels in and out of ports and harbors. Hulls’ boat was never built, but it paved the way for the development of the tugboat.

The early tugboats were small, steam-powered boats used to tow barges and other vessels. They were primarily used in harbors and rivers. In the United States, the first steam-powered tugboat was built in 1818 by Robert Fulton. The boat was named the North River Steamboat or the Clermont.

It was used to tow barges on the Hudson River. By the mid-19th century, tugboats were becoming more common, and their use was expanding beyond just harbors and rivers.

Modern Developments

As technology advanced, so did the capabilities of tugboats. In the mid-20th century, diesel engines began to replace steam engines in tugboats. This allowed for more power and efficiency. Today, tugboats come in a variety of shapes and sizes and are used for a wide range of tasks. They are used to tow barges, assist larger ships in docking, and even to fight fires on the water.

Modern tugboats are equipped with advanced technology, including GPS and radar, to help them navigate and operate more efficiently. They are also designed to be more environmentally friendly, with many tugboats now using cleaner-burning engines and alternative fuels.

In recent years, there has been a trend toward developing autonomous tugboats. These self-driving boats could potentially reduce costs and improve safety in the maritime industry. However, there are still many challenges that need to be overcome before autonomous tugboats become a reality.

Types of Tugboats

Tugboats are small but powerful boats that are primarily used for towing and pushing other vessels. There are different types of tugboats based on their functionality and the environment they operate in. In this section, we will discuss the three main types of tugboats: Harbor Tugs, Ocean Tugs, and River Tugs.

Harbor Tugs

Harbor Tugs are the most common type of tugboat, and they are designed to operate in ports and harbors. They are typically smaller in size and have less power than ocean tugs. Harbor tugs are used for a variety of tasks, including moving cargo ships, barges, and other vessels around the harbor. They are also used for firefighting, pollution control, and other emergency services.

Harbor Tugs are usually equipped with a single propeller, which provides the necessary power to move the vessel and the towed vessel. They also have a towing winch, which is used to control the towline.

Ocean Tugs are designed to operate in open waters and are larger and more powerful than harbor tugs. They are used for towing large cargo ships, oil rigs , and other vessels over long distances. Ocean Tugs are equipped with multiple propellers, which provide the necessary power to move the vessel and the towed vessel. They also have a towing winch, which is used to control the towline.

Ocean Tugs are classified into three types based on their size and power:

River Tugs are designed to operate in rivers and other inland waterways. They are smaller and less powerful than harbor tugs and ocean tugs. River tugs are used for towing barges, dredging, and other tasks that require maneuverability in shallow waters.

River Tugs are usually equipped with a single propeller, which provides the necessary power to move the vessel and the towed vessel. They also have a towing winch, which is used to control the towline.

Tugboat Operations

Tugboats are designed to provide assistance to larger vessels in a variety of ways, including towing, pushing, and marine salvage operations . These operations require specialized knowledge and expertise to ensure safe and effective outcomes.

Towing is the most common operation performed by tugboats. Tugboats use a towing line to pull larger vessels, such as cargo ships or oil tankers, to their destination. The towing line is attached to a winch on the tugboat, which provides the necessary power to move the vessel. Tugboat operators must carefully consider the weight and size of the vessel being towed, as well as the weather and sea conditions, to ensure safe towing operations.

Pushing is another operation performed by tugboats. Instead of using a towing line, tugboats push larger vessels, such as barges or other vessels without propulsion, to their destination. Tugboats can push vessels in a straight line, or they can use a technique called “hipping up” to push the vessel sideways. This technique is often used when navigating narrow or shallow waterways.

Salvage Operations

In addition to towing and pushing, tugboats are also used in salvage operations. Salvage operations involve recovering vessels that have run aground or are in distress. Tugboats can assist in these operations by providing additional power to move the vessel, stabilizing the vessel, and transferring crew and equipment to and from the vessel. Salvage operations require specialized knowledge and expertise to ensure safe and effective outcomes.

Tugboat Propulsion Systems

Tugboats are an essential part of the maritime industry, used for towing and pushing other marine vessels, and for assisting in port operations. Tugboats are equipped with a variety of propulsion systems, each designed to meet specific requirements.

Azimuth Stern Drive Tug

The Azimuth Stern Drive (ASD) tug is a popular choice for port operations and ship docking. The ASD tug has a propulsion system that consists of two or more azimuth thrusters, which can rotate 360 degrees, providing excellent maneuverability. The ASD tug is capable of both pushing and pulling operations and is ideal for berthing large vessels in confined spaces.

Conventional Tug

The conventional tug is equipped with a single propeller and rudder system. This type of tug is commonly used for towing operations between ports. The conventional tug has a high towing capacity and is capable of towing large vessels over long distances.

Tractor Tug

The Tractor tug is equipped with a propulsion system that consists of two or more Voith Schneider Propellers (VSP). The VSP system provides excellent maneuverability and is capable of both pushing and pulling operations. The tractor tug is commonly used in ship docking and port operations.

VSP Voith Schneider Propeller

The VSP system is a propulsion system that consists of a circular plate with vertically mounted blades. The blades can be tilted to provide thrust in any direction. The VSP system provides excellent maneuverability and is commonly used in tugboats and other vessels that require precise maneuvering.

Each type of tugboat propulsion system has its advantages and disadvantages. The choice of propulsion system depends on the specific requirements of the operation. Tugboat operators must carefully consider the requirements of each operation to select the appropriate propulsion system.

Tugboat Safety

Regulations.

Regulations exist to ensure the safety of tugboats and their crew. The United States Coast Guard (USCG) sets these regulations, which include requirements for equipment and crew qualifications. Tugboats must have proper navigation and communication equipment , fire-fighting equipment, and life-saving equipment. Crew members must also have the necessary training and certification to operate the vessel and handle emergency situations.

The USCG also requires regular inspections of tugboats to ensure compliance with regulations. These inspections cover everything from the vessel’s structure and machinery to its safety equipment and crew qualifications. Tugboat owners and operators must maintain their vessels in good working order to pass these inspections.

Proper training is essential for the safe operation of tugboats. Crew members must be trained to operate the vessel and handle emergency situations, such as fire or flooding. They must also be familiar with the vessel’s equipment and safety procedures.

Training programs for tugboat crew members include classroom instruction and hands-on experience. Classroom instruction covers topics such as vessel operations, navigation, and safety procedures. Hands-on experience includes training in vessel handling, towing, and emergency procedures.

In addition to initial training, crew members must also receive regular refresher training to maintain their skills and stay up-to-date with new regulations and technologies.

Overall, tugboat safety is a top priority for the USCG and the industry as a whole. Regulations and training programs help ensure that tugboats and their crew operate safely and effectively.

Tugboats in Our Lives

Each year, New York City hosts the Great North River Tugboat Race and Competition . This event, which has been held annually since 1994, brings together tugboats from around the region to compete in a variety of events, including a race up the Hudson River and a nose-to-nose pushing contest.

The event is a celebration of the important role that tugboats play in the maritime industry, and it provides an opportunity for the public to see these powerful vessels up close.

In addition to the races, the event also features tugboat tours, live music, and other family-friendly activities.

During the event, you may notice special attention from photographers and shipspotters taking pictures of tugboats. Shipspotting is a hobby that involves photographing and tracking ships and other vessels as they move through ports and waterways.

It is a popular hobby among maritime enthusiasts, and it provides an opportunity to learn more about the shipping industry and the vessels that operate within it. Shipspotters often gather at ports and other vantage points to photograph passing ships and record information about their size, type, and destination.

They may also use websites and apps to track the movements of specific vessels and share information with other enthusiasts. Shipspotting can be a fun and rewarding hobby, but it is important to remember to respect the privacy and safety of the vessels and their crews.

Shipspotters should always follow local regulations and guidelines, and should never interfere with the operations of the vessels they are observing.

Can tugboats go fast?

Tugboats are not designed for speed, but for power and maneuverability. They typically have a top speed of around 10-12 knots, but their primary function is to tow or push other vessels, not to travel quickly.

How are tugboats so powerful?

Tugboats are powerful due to their design and engine power. They have a short, wide, and deep hull that provides stability and maneuverability. They also have high-powered engines, often diesel, that allow them to generate a lot of torque and pull larger vessels.

How much does a tugboat cost?

The cost of a tugboat can vary greatly depending on its size, age, and condition. Small used tugboats can be purchased for less than $100,000, while larger, newer tugboats can cost millions of dollars.

How hard can a tugboat pull?

The amount of force a tugboat can exert, or its bollard pull, varies depending on the size and power of the tugboat. Smaller harbor tugs may have a bollard pull of a few hundred horsepower, while larger ocean tugs can have a bollard pull of over 100 tons.

Is it safe to use a tugboat?

Yes, tugboats are safe to use when operated properly and in compliance with regulations. The United States Coast Guard sets regulations for tugboats, including requirements for equipment and crew qualifications. Crew members must receive proper training in vessel operations, navigation, and safety procedures, and must receive regular refresher training to maintain their skills and stay up-to-date with new regulations and technologies.

About the author

I worked as an officer in the deck department on various types of vessels, including oil and chemical tankers, LPG carriers, and even reefer and TSHD in the early years. Currently employed as Marine Surveyor carrying cargo, draft, bunker, and warranty survey.

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Frequently Asked Questions

• Nov 14, 2020

How do tugboats work?

Updated: Oct 27, 2021

Tugs are special boats that assist other vessels into and out of port. The primary purpose of these boats is to help move larger ships by towing, pushing, and guiding. Many even have fire suppression and other systems to help the larger ships. But how is it that these seemingly tiny tugs move boats a thousand times their size, and why can’t those boats move themselves? Let’s take a look at what makes tugs special, and why they’re an integral part of shipping.

Image Credit: MarineLog

Why are tugs needed?

Tugs fill a few different roles:

Acting as salvage boats

Acting as ice breakers

Tugs carry firefighting equipment to provide assistance in case of a fire

Moving barges, rigs, and other floating equipment that does not propel itself

Helping a boat through narrow areas, in inclement weather, or docking and mooring

The last role is usually the largest, but why do large ships need help getting into and out of port? It’s easy to maneuver a large ship at sea, they can keep up speed and have plenty of room to adjust course. The larger ships grew, the more they could carry long distances, but the less agile they became at low speeds and in tight spaces. Moving sideways is particularly difficult for vessels that can be hundreds of meters long. Often, when huge vessels like container ships and LNG ships get close to port, they are escorted by a tugboat, ensuring they take the safest route. Once in port, it’s again up to the tugs to take them on the last leg of their journey.

How do they move large ships?

Depending on the size of the ship and the tugs, once in port, one or more tugs can tow via a tow line or push the ship into dock. At low speeds, large vessels don’t have enough water passing over the rudder to turn quickly, so this assistance is needed for the final mooring of the ship, especially in crowded ports. The tow line can be used for direct or indirect towing. With direct towing, the tug is pulling the vessel straight ahead, likely due to the ship not having the ability to propel itself. With indirect towing, the tug can act as a rudder and pull the ship to one side, helping rotate the ship as it moves. Of course, tugs can also cruise right up to the side of the ship and push. Large ships usually have designated areas where tugs can push safely.

Image Credit: Workboat

What are the types of tugboats?

Tugboat designs have changed over the years, the oldest being the conventional tug. These are in use all over the world and consist of a diesel engine and have one or multiple propellers. They use a screw propeller design with nozzles and rudders that move to help them maneuver. The benefits to a conventional tug are that they are simple, low maintenance, and have a proven design. Downsides are they do not have the performance of new tugs, some only go in one direction, they are more prone to capsizing, and can’t work with the largest ships. They are very reliable and still in use today.

The tractor tug is next up, it uses a “2-multidirectional propulsion unit, of which some are rather like large rotating outboard motors with other consisting of rotating vertical blades,” according to Marine Insight. These are more versatile and agile compared to conventional designs. They can provide 360 degree thrust, have low risk of capsizing, and can work sideways. Downsides are less pull compared to newer ASD tugs, high maintenance cost, and complexity.

Azimuthal Stern Drive (ASD) use some of the benefits of both the conventional and tractor tugs. They have two towing locations and use two rotating azimuth units for propulsion. Benefits of these tugs are lots of bollard pull, shallow draft, and better stability at speed. Downsides are they are a little more complex to control and limited in some maneuvers. You can see a tugboat with azimuth thrusters in the photo below.

Image Credit: Reddit

Most tugboats are still powered by diesel engines. Many newer and larger tugs have two diesel engines, some with a combined total of over 6,000 horsepower! There are also hybrid tugs that combine diesel and electric power, and LNG-powered tugs.

Are there electric tugs?

Yes! In September 2020, the first fully electric tugboat went to work in Istanbul. ZEETUG, which stands for Zero Emission Electric Tug boat, built the Gisas Power , owned by GISAS Shipbuilding. It operates in the Port of Tuzla Aydınlı Bay, where environmental and navigational needs drove the demand for the electric tug. Plugboats has specs on the Gisas Power , “The Gisas Power has an overall length of 18.7 metres • 61 feet, a beam of 6.7m • 22′ and 32 tonnes of bollard pull (BP), which is how the power of tugboats is rated. Different tugboats are designed for different jobs, but the ‘average’ tug has a BP rating of about 40-45 tonnes and the strongest are rated at 60-65T BP.” ZEETUG’s electrical propulsion system can be built to specifications from 5T BP all the way up to 75T BP. The ZEETUG-30 is the first all electric tugboat - it gets power from two 1,450kW battery packs that are located separately, forward and aft, and air-cooled. More electric tugs and even hydrogen tugs are on the way.

Image Credit: PlugBoats

What about Autonomous tugs?

There are autonomous tugs too! In March 2020, Wartsila and PSA completed initial sea trials with an autonomous tugboat for the IntelliTug project. The PSA Polaris was retrofitted for autonomous navigation and tested to ensure it could avoid virtual and real-life obstacles. They are continuing R&D on the new tug throughout 2020.

Image Credit: Splash247

As you can see, tugboats are an important part of getting large ships into and out of port, through dangerous situations, moving all types of non-powered or disabled vessels, firefighting, and even search and rescue. Check out the video below for a day in the life of a tug operator in Dublin Port.

Video credit: Dublin Port Company

https://www.marineinsight.com/types-of-ships/what-are-tug-boats/

https://www.popularmechanics.com/technology/infrastructure/a5358/4346840/

https://en.wikipedia.org/wiki/Tugboat

https://www.workboat.com/news/government/upgrading-tugboat-engines-are-cost-effective-pollution-control-report-says/

https://plugboats.com/worlds-1st-all-electric-tugboat-now-work-istanbul/

https://splash247.com/wartsila-and-psa-completes-trial-of-autonomous-tugboat/

https://www.youtube.com/watch?v=s-u5I4AR4EU

https://www.marinelog.com/news/turkish-tugboats-deliver-big-bollard-pull-on-trials/

https://external-preview.redd.it/erXmKizXsWGXnopfSMakaWbAAIXBzukWGqqD1zFLTRI.jpg?auto=webp&s=61936af76333f2cc0198b3efacd026a338ecc108

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Tugboats | Definition, Working & What Tugboat Used For – Ultimate Guide

Last Updated on July 29, 2020 by Amit Abhishek

A Tugboat or Tugboats are a special vessel used mainly near the harbor and ports to assist in docking of the ships. As discussed in my older post “ Types of Boats “; a tug boat is a powerful vessel in a small form that uses push or pull to do its job. Its primary job is to assist large ships during maneuvering and docking operation.

The other use of tugboats is to tug or pull barges; oil platforms, disabled ships to carry them to the secured positions. Not just that, many a time they are also used as ice breakers do fire fighting duties and act as a salvage boat. It is also not uncommon to see them performing escort for a large ship in narrow waters.

With an average power of 700 to 3500hp, they are quite powerful in deep and shallow waters.

Being one of the first vessels to incorporate steam propulsion; they are considered pioneers in the development of the shipping industry.

These small yet powerful watercraft first built in 1736; for the support and salvage operation in Clyde Canal ( Scotland ).

The two main advantages of tugboats over other watercraft and ships is; its ability to maneuver easily in the most restrictive waters and its high power to weight ratio.

Tugboats are not just more powerful for their size but equally more strong and solid. They can be seen in rivers, near ports, and out in the ocean; yet only a few notice their presence due to its small size.

What Are Tugboats Used For ? – Its Types Based On Area Of Application

Ships began to grow bigger and bigger with the development of the shipping industry starting from the late 20th century.

In less than a century they become so large; it practically becomes impossible to turn the ship in narrow channels or near ports.

Since each sip is required to dock in a preassigned position; tugboats become an important aspect of the shipping industry.

Without a tug boat, it is almost impossible to berth a very large ship at the port. Other than its primary operation to assist the large ship’s in mooring and berthing operation; it also take part in a number of port activities at times. Overall they have been used to tow, assist and escort ships near ports and in congested waters.

Thanks to its solid structure and high power to weight ratio; they also act as salvage boats, icebreakers and utility boats for barges and oil platforms.

Many a time they are also seen as shifting offshore drilling platforms. This enormous strength and power came from its unique propulsion system.

Based on there specific use and area of operation; a tugboat or tug boats can be classified into 3 main types:

1 ) Seagoing Tugboats

Made with high strength material these boats are built to go out in international waters and generally have the most powerful engines.

A little bigger than its other subtypes; they have a power to tonnage ratio of about 2:4.5 to 2.2:5. Equipped with towing lines they tow ships, other boats, and other watercraft.

Out in the open sea they salvage ships and boats that undergo engine failure, or receive significant damage from collision or grounding.

These vessels are then towed using towing lines capable of handling ships of much larger sizes with free movement. This free movement of towing lines is often ensured by having a low aft deck structure.

Ranging from 150 to 250 feet in length these boats are generally called upon to do heavy-duty jobs at sea; such as shifting drilling platform, barges, and damaged ships.

Other than that they are also used for fire fighting and other emergency responses at sea. Other than that they are often used in navy across the world for support and patrol purposes.

2 ) Harbor Tugboats

A harbor tug is the one we usually see near ports handling and supporting proper docking of the ships. These tugboats do this by using push and pull to rotate and position the ship in a particular position.

It is hard for any ship to turn 360 degrees in such congested water; and if it wasn’t these tugs it would be a challenge.

They are designed for both assisting and towing purposes and so are generally termed as multi-purpose tugboats.

Having such high demands they have a higher power to tonnage ratio; in comparison with other tugboats of 4:10 or 3.9:9.5. The majority of harbor tugs that we see are of azimuth stern drive type.

In some cases, you may also find another more powerful tugboat called tractor tug; which includes benefits such as 360 degrees turning at full capacity while towing a ship.

The other benefits include instant power, better control, excellent maneuverability, and better response. Irrespective of its type ( azimuth stern drive vs tractor tug ) harbor tugs have the most maneuverability than others.

3 ) Escort Tugboats

If you ever been on any ship without bow thruster you must have noticed tugs assisting in your ship near canals and in the area with a narrow passage.

These specialized tugboats which are designed to assist in the maneuverability of very large ships; in restricted waters are best known as the escort tugboats.

Other than that escort tugs came into rescue; when your ship’s main propulsion system fails or has trouble steering the ship.

Thus you can find them near canals, harbors, ports, and channels; where there are huge risks of pollution and maritime safety due to engine failure or steering gear defects.

Thus the first escort tugboat was used for an oil tanker in 1975. On many ports around the world having an escort, tugboat is made compulsory as part of safety.

The boat can use both direct or indirect mode of operation or either of the two. Thanks to the growing size of ships newer tugs are having more and more bollard pull.

Types Of Tug Boat Based On Their Application Or Purpose

A ) escort tug boats.

These are the specialized tug boats used to assist the ship in navigation in local waters. They are usually found near a canal or a narrow sea area of strategic importance. These are generally the first tug boats that came to rescue operation in an emergency. Other than that they are also used to maneuver ferries from one place to another.

Note: Already Discussed above so not going in details

B ) Support Tug boats

The name support tugs themself gives a brief idea about them; what they do and how much could be their size. These are the ones used for supporting other vessels near and around the harbor or ports.

They are generally involved in towing and berthing operations. There are many distinct types of support tug available based on their design capabilities.

And the only thing that sets them apart is their maneuverability, strength, and control.

In a crowded harbor, even with bow thrusters, it becomes impossible sometimes to securely berth a ship without using a tug boat.

Thus its a necessity for most ports otherwise the whole operation will be exceedingly difficult and risky.

It’s all about the collective exercise of exerting forces at the designated places on a ship to turn it efficiently by 360 degrees.

Since a ship has ample power and means for the backward and forward movement. The tug boats generally just assist them with their sideways movement.

While on some ports there are local laws that make it compulsory to have tug assistance; most ships just do because it reduces both the risks and effort of mooring operation.

1 ) Conventional Tug Boat

They are the simplest of the tug types used by our forefathers and still in service. While they have lesser maneuverability compared to moder design; they are cheap and simple to maintain.

Thus you can still find them around near most ports across the globe. They usually have either a single or multi propper driven by a diesel engine.

The propeller used can be of single screw, double screw or multi screw type with a conventional rudder. They usually have a towing hook provided at their center.

The position of that towing hook is of great importance; as the safety and performance of the tug depend much upon the position of towing hook.

The major advantage of using conventional tugs is its low operational and maintenance costs. Furthermore, it is easy to maintain and is also self-sufficient.

Their downside is low astern power, lesser efficiency, stability issues, and operational hazards in the form of risk involved of capsizing while the operation.

2 ) Azimuthal Stern Drive

It is a special type of tug that utilizes the power of two rotating azimuthal stern drive for propulsion. This not just saves the space and mass of having a dedicated marine engine but also improves the power significantly.

The design helps with both speed and stability of the vessel; thus making it suitable for work in open waters.

This boat holds two towing locations one at the front and one at astern. With better bollard pull, efficiency and towing power it’s better used for the largest vessels to assist in their berthing.

The major advantage of azimuth stern drive over conventional tug is that it can work well even under shallow waters.

The azimuth themselves are much easy to remove, inspect and do regular routine maintenance. It also features a much better heel with a side thrust of around 15 degrees.

Thus improving its directional stability while at high speed or doing towing operation under full power.

3 ) The Tractor Tugs

These are the big boys of the tugs world with a heel to side thrust of around 21 degrees. It possesses such a better control thanks to its multidirectional propulsion unit.

Which is either in the form of an outboard motor or double blade rotating blade. Thanks to its design and location of the towing point at stern much nearer to its propulsion unit; it posses a positive towing moment.

This all makes it a versatile machine with better control, power, and speed. Thus they are much more flexible than both astern and conventional tugs and have a better response time.

These are really great for the sideways movement as it is the only tug boat that provides the full towing force for complete 360-degree rotation.

It put it into a much superior category with the ability to easily overcome the interaction forces; that a boat feels or undergoes as it interacts or came too close to a larger ship.

The only disadvantage is that they have a lesser bollard pull and are not cost-effective. Meaning it required huge capital investment and running cost.

How Tugboats Work Or Do Its Job

Although tugboats look much small and helpless with respect to big ship but it drastically reduces the berthing time. Even with ships using bow thruster; a tug can rotate them 10 times faster than using big bow thruster.

That is achieved by the sound grip of the tugs on ships hull, its powerful engines, and simple forces such as a push or pull.

A tug does its job by using either the direct approach or indirect ones. Most conventional and azimuth harbor tugs often work in a team and push the ship in order to turn it.

They use their high power engine ( 3 to 4 thousand hp ) and heavy displacement hull to generate more grip and displacement in water.

They use a turbocharged four-stroke marine diesel engine with a computer monitored fuel injection system; that provides enough power to tow most ships on their own.

Having a low freeboard with heavy displacement hull design makes sure the tug stays low in the water. This helps generate more friction with water meaning more power with a steady boat.

In the indirect approach tractor tugs and azimuth harbor tugs hook on to the back of the ship; now using the towing line and its powerful propulsion it turns the ship on its own.

With that being said I do not want to neglect the importance of waves, wind, and weather condition that affects this process.

Step’s Followed In Ship’s Towing Operation

All concerned parties tugs, ship’s and the port control must follow a particular code of conduct while entire towing operation. Such code of conduct followed by step by step instruction; are all in all part of ports navigation safety system which is pat of the international ports marine safety code.

All concerned parties must be aware of the role he or she has to play in the entire sequence of events. These steps include planning, Pilot -Master exchange, communication, preparedness, connecting towing gear, safe operation and disconnecting of the towing gear.

• Planning: After the pilot has embarked on the ship; A detailed action plan must be discussed and agreed upon between the ship’s master and the pilot before the towing operation. All necessary maneuvers and the number of tugs to be allocated for assistance are discussed beforehand. This includes number and types of tugs to be used, towing positions, number of personnel involved, present conditions, etc. Conflict if any is resolved all before the actual towing operation starts.
• Pilot-Master Exchange: Apart from the brief introduction and planning there must be a formal exchange of key information between the pilot and the ship’s master. The pilot must inform the master about the mode of towage, tug rendezvous, planned ship speed, minimum and maximum towing force, maximum speed of tug, area of transit and lines of communication with active VHF channels. Similarly, the master must brief the pilot about self-working limits of mooring fittings, chocks/bollard/points to be used for towing, areas of hull strengthened and any other important information such as bow thruster/CPP etc.
• Communication: Before the towing operation line of communication is being agreed upon between the ship’s master, pilot, tug master, and the port authorities. VHF communication channels and Vessel Traffic Services acts as the major communication channel between the concerned authorities. Once VHF communication is established between the ship and the tug; it must be tested and then used through the towing operation. It is important that proper means of communication is maintained throughout the operation.
• Preparedness: Towing ropes and wraps are under huge load and tension during the entire mooring and towing operation. Sudden failure in any part can result in acute damage to the ship and boat with certain loss of life and heavy injuries. That is why its a must to take precautions before starting towing operation. All running gear such as ropes must be checked for wear or damage and checked for sufficient strength. All other associated equipment & gear must also be inspected and tested for correct operation.
• Connecting Towing Gear: Before connecting towing gear the ship’s speed must be sufficiently reduced; as to allow safe connection and rendezvous with the tug. Both ships and tug relative position and speed must be closely monitored and administered with the VHF channels. Before commencing to tow, it must agree upon which towing gear to be used before the heavy lines are being transmitted. The towing gear must be free of any obstruction and is able to run freely under its maximum load limit.
• Safe Operation: To ensure safe operation all crew or associated personnel must stay away from danger zones. If possible all personnel if not required must be instructed to move away after completing its job. The working crew must be aware of the risks involved and what to do to stay away from possible dangers. They must also be aware that the mooring lines can sometimes automatically disconnect in an emergency. And at all times continues communication must always be maintained.

How Powerful Is A Tugboat & How Come It Able To Toe Large Ships?

The power and capability of a tug boat are measured in the form of its maneuverability and engine power. The power is determined by the amount of torque the engine produces or horsepower. Similarly, the ability turn, pick up speed and stop within record time and distance determine its maneuverability.

On average a tug can have an engine with power in between 3 to 6 thousand horsepower. A 3 thousand horsepower engine can allow tugs to toe ships as large as an aircraft carrier. It is for the ULCC that tugs of greater power are required. Similarly, a tug should be capable of turning a complete 360 degree almost within her length.

Moreover, it must go from its maximum speed forward to maximum speed back in not less than 15 seconds. The reason for all this power and agility is simple; to be able to toe large ships maintaining safe maritime passage. Thanks to the unique ability of water to exert less friction; any small vessel can push or pull a large ship.

These tugs are equipped with strengthening winch and additional stability that helps them exert more torque and strain on the towing line; thus exerting necessary force to toe the ship.

To turn they also apply forward push in teams of two and three on dedicated positions on the ship’s hull. All big ships have these soft positions marked on the hull; making it easier for tugs to do their job.

Common Doubts & Questions ( Tugboats )

Q.1. why do some tug boats spray water near ports.

Ans: While its not much of a required job or event but rather a long ceremonial custom to welcome arriving ship at port. Right from the early days of shipping, it is in tradition to spray water in the air using fire hydrants and nozzles. This is done to give due respect to any vessel or on special occasions.

Q.2. Why Do Tugs Stay Far Ahead Of The barges Or Ship It Toe?

Ans: There is no such thing as brakes in water and you will not stop just because your engines are on hold or down. In the condition when a ship or barge ( a water vessel without engine ) is toed by a tug; it is common practice to maintain a safe distance. If not there can be accidents and the barge or ship can collide with the tug.

Q.3. Does Tugs Too Have Anchors?

Ans: Every water board vessel that has its own propulsion system has an anchor. It is another thing that its not that big as many other boats of similar size or power do have. It is so because they are mostly in service and rarely required to anchor and wait for the orders. They can have either conventional anchor or the one which they can lower with the windlass.

Q.4. Why Do Most Tugs Push More Than Pull?

Ans: Since a majority of tugs are used near harbor and ports they generally assist in berthing/docking of the large ships. On most occasions they are not required to toe; and so it always easier and safe to push the ship on marked position to turn it using tugs. That is the reason why many people find them pushing near ports, but away from ports they usually toe or pull other water vessels. Even in ports, bigger tugs tend to pull more than pushing them.

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Tug workers' strike strands cruise ship passengers in Vancouver harbour

Update 1 pm: The cruise ship has now set sail for Alaska 

Cruise ship passengers aboard the Celebrity Eclipse were supposed to be en route to Alaska by now, but instead, they spent the last day stranded in the Vancouver harbour, with no indication of when or if they’ll leave.

The boat was supposed to depart Sunday at 4:30 pm but was still in the harbour as of 9:30 am Monday — all because of job action by tug boat workers.

“Without the support of tug boats, the ship is unable to depart the port,” Celebrity said on Twitter. “We’re working with local authorities to resolve the situation so that the ship can depart.”

Hi Claire, there’s a local tug workers strike at the Port of Vancouver. Without the support of tug boats, the ship is unable to depart the port. We are working diligently with all local authorities to resolve the situation so that the ship can embark on its sailing. — Celebrity Cruises (@CelebrityCruise) August 29, 2022

Fuel barge is still attached to #Crusie ship #CelebrityEclipse pic.twitter.com/iOobqAXVY3 — sherepunjabradio (@SherEPunjab600) August 29, 2022

Tug workers began their strike on August 25 , after union negotiations with Seaspan reached an impasse. Union members across British Columbia have been told to decline all employment opportunities until the employer delivers an improved offer.

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Passengers aboard the shift have shared their frustrations on social media and have criticized the cruise line operator for its lack of communication. According to passengers on Twitter, the captain updated passengers at 6 pm Sunday and again at 7 am Monday — but there’s still no clear solution.

“Stuck on Celebrity Eclipse in Vancouver harbour. Been on board nearly 20 hours and not moved an inch,” a passenger named Neil Young tweeted. “Not going anywhere and can’t get off. Worst thing is total lack of communication from the company.”

@CelebrityCruise 1/2 Stuck on Celebrity Eclipse in Vancouver Harbour. Been onboard for nearly 20 hours now and not moved an inch. Not going anywhere and can’t get off. Worst thing is total lack of communication from company . Just had first announcement since 6pm last night — Neil Young (@shakeyneil) August 29, 2022

According to Young, two other cruise ships left before the Eclipse, which was frustrating to watch. Celebrity replied to him, saying the Eclipse just happened to be the final ship scheduled to depart.

“We spent thousands of dollars to go on this cruise and are stuck at the dock due to a fuel barge that is tied off to the ship, and those employees are striking,” Mark Powers tweeted.

How about we focus on the Celebrity Eclipse that was supposed to leave Vancouver at 4 today? We spent thousands of dollars to go on this cruise and are stuck at the dock due to a fuel barge that is tied off to the ship and those employees are striking. — Mark Powers (@MarkPow57791085) August 29, 2022

David McCue, another passenger, shared a photo of his view from Vancouver, adding he’s frustrated to learn he’ll miss out on parts of his cruise to Alaska.

My view of our 2nd day of our Alaskan Cruise-still stuck at the wharf in Vancouver 😡😡😡😡 Not real happy and waiting for updates to see what part of our cruise we will miss out on- if we ever get out of port Vancouver pic.twitter.com/1aDsPVs5Gr — David McCue (@DavidMcCue1) August 29, 2022

Another passenger, Thiago Salgado, said most of the ship is still in high spirits and enjoying the onboard offerings.

“There are worse places to be stuck at,” he said on Twitter. “Crew is very nice and everything on the ship is working as expected. We are still hoping to set sail to Alaska soon.”

Hello Amanda Not much else to say. There are worse places to be stuck at… Passengers are still in high spirits enjoying what the ship has to offer. Crew is very nice and everything on the ship is working as expected. We are still hopping to set sail to Alaska soon. 🤞🏻 — Thiago Salgado (@thiago_salgado) August 29, 2022

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Could Tugboats Have Helped Avert the Bridge Collapse Tragedy in Baltimore?

W ith the 95,000-ton cargo ship Dali powerless and hurtling helplessly toward the Francis Scott Key Bridge, the harbor pilot commanding the vessel had just minutes to make his last, desperate attempts to avoid disaster. He declared distress, dropped anchor and, notably, called for help from nearby tugboats.

Two 5,000-horsepower tugs, which only minutes earlier had helped guide the ship out of its berth at the Port of Baltimore and peeled off, quickly turned back and raced toward the Dali. But it was too late. The massive ship stacked with cargo slammed into the bridge in the predawn darkness Tuesday, toppling the span and killing six construction workers .

Whether those tugs could have averted the disaster with the Dali already out of control is debatable. But maritime experts interviewed by The Associated Press say they could have made a difference if the tugs had stuck by the ship longer, escorting it on its 18-minute trip through the port’s deep-water channel, in a position to see it drifting off course and potentially nudge or tow it back in line.

Such extended tugboat escorts aren't required or even customary in Baltimore or at many other U.S. ports, mostly because of the costs they would add for shippers. But with the increasing size of cargo ships and the threat they pose to bridges and other critical infrastructure, some are questioning whether they should be.

“I’m a big fan of tug escorts,” said Joseph Ahlstrom, a member of the Board of Commissioners of Pilots of the State of New York, which regulates the state's harbor pilots. “If applied early enough and effectively, yes, a tug escort could prevent a collision with the bridge or with another ship, or going aground."

“Going to sea is danger,” added Ahlstrom, who also teaches at the State University of New York’s Maritime College. “But if you’re going to go to sea, if you’re going to put yourself at risk, do whatever it takes to minimize risk.”

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Maritime experts told the AP that the Baltimore disaster highlights how each individual port makes its own tugboat rules, resulting in a patchwork across the nation, and how competition among ports for business from cost-conscious shipping companies has trumped calls for extended tugboat escorts that can add tens of thousands of dollars to every transit.

Baltimore's port, operated by the state of Maryland, ordinarily uses tugboats to help maneuver big ships out of their docks and doesn't require extended tugboat escorts into the port's channel and broader Chesapeake Bay unless ordered by local harbor pilots or the U.S. Coast Guard over safety concerns tied to weather, traffic, cargo or mechanical issues. Shippers can also request tugs.

In the case of the Dali, two state harbor pilots boarded the Singaporean-flagged ship to take over navigation through the port as the vessel set out on a trip to Sri Lanka. Two tugboats, the Eric McAllister and the Bridget McAllister, guided the massive vessel out of the tight spaces of the dock and then released when the ship was safely in the channel.

But within minutes, according to satellite data that tracks vessel traffic, the 984-foot (300-meter) Dali began to drift out of its lane and veered more sharply before slamming into one of the main pillars of the bridge, which is a critical conduit for Baltimore truckers and commuters.

The National Transportation Safety Board, which is investigating the crash, said a review of ship's voyage data recorder showed the pilot's 1:26 a.m. call for help from nearby tugs came about four minutes before impact.

“One of the things that was hard for me to believe is that they didn’t require tugs on the vessel as it was traversing towards the bridge,” said David Heindel, president of the Seafarers International Union, which represents U.S. merchant mariners.

“Some ports require tugs, depending on the vessel, usually tankers. You see where tugs have to escort ships in and out of port, especially narrow ports," Heindel said. "In the end, I think that that may be exactly what happens in the Port of Baltimore.”

The Maryland Port Administration did not immediately respond to requests for comment. A U.S. Coast Guard spokesman said the service doesn't direct tug operations in the port and the Dali's departure “is the typical outbound scenario for these types of cargo ships.”

The Dali is owned by Grace Ocean Private Ltd. and managed by the Singapore-based Synergy Marine Group. Synergy spokesman Darrell Wilson said the pilots guide the company's ships in and out and that he didn't know how tugs are coordinated.

The Eric McAllister and Bridget McAllister are muscular machines. Called tractor tugs, they don't just nudge ships. The Eric McAllister, the bigger of the two, is 98 feet (30 meters) long and equipped with a thick steel cable and winch that, when attached to even a large cargo ship, can potentially pull it away from trouble.

The 1989 Exxon Valdez disaster in Alaska's Prince William Sound spurred Congress and a few states to require tug escorts for oil tankers. But those limited requirements were aimed at protecting wildlife from spills, not safeguarding critical infrastructure such as bridges.

Jennifer Carpenter, president of the American Waterways Operators, a trade group that represents tugboat and barge companies, said that given the Dali tragedy, she expects regulators to look closely at whether more stringent tugboat escort requirements are needed.

But she said tugboats are just one part of a complex safety matrix that also includes concrete fenders for bridges and emergency response systems.

The supply of tugboats is limited and using them more frequently entails risks, she said, primarily pollution and increased sea traffic.

“The last thing we want to do is have two tugs escorting every vessel,” Carpenter said. “That would have massive implications for the efficiency and safety of our waterways, which are already pretty crowded.”

Some ports have tried to boost vessel escort requirements. But they often face resistance from shippers, who are under pressure from customers to move goods as cheaply as possible.

In 2004, California’s Legislature passed a bill requiring tug escorts for chemical tanker ships in San Francisco Bay, but it was vetoed by then-Republican Gov. Arnold Schwarzenegger amid protests by the shipping industry over cost concerns.

“Tugs are a big upfront cost and a lot of companies don’t want to pay for that,” said Sal Mercogliano, who writes a widely followed shipping blog. "And if Baltimore starts mandating it, you’re going to see ships go to Norfolk, Philadelphia, New York — wherever is cheapest.”

McAllister Towing, which operates the tugboats that guided the Dali, can charge $15,000 or more for one or more of its ships to lead a large cargo vessel out of its berth, according to a recent rate sheet, with more charges for extended escorts.

That may be small change for a big shipping company but the costs can add up.

John Konrad, a licensed captain, said there’s an “unspoken tension” between shipping companies and pilots over how many tugboats should be used and how long they remain with a seagoing vessel.

“The pilots would like, in an ideal world, to have extra tugs with them all the time until the ship gets out to the ocean,” said Konrad, founder and CEO of gCaptain, a website for maritime professionals.

“But the shipping companies don’t want to pay for those tugs," he said. "So there’s always this push and pull.”

Associated Press reporter Josh Funk contributed.

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Crowley Shipping

Ship assist and tanker escort, meet the fleet.

As a proud service provider in the Pacific Northwest since the 1920s, we provide escort and docking services for tankers, container ships and other vessels throughout the region.

The Pacific Northwest presents some very distinct environmental and physical challenges, but our highly flexible tugboats in the region support the operational needs of our customers wherever they do business.

In North Puget Sound, we assist tankers, ATBs, and other large vessels in and out of berths and provide escort services throughout rugged coastal region, which, at times, experiences extreme weather conditions. Our high horsepower/high bollard pull tugs, which are equipped with the latest technology in navigation, communications and firefighting equipment, have been specifically designed to provide safe and efficient escorts and assists to tankers operating in the region.

In Seattle, Tacoma and other regional surrounding ports, we provide docking services for tankers, container ships and other vessels, as well as the occasional escort.

The following tugs are in operation in the Pacific Northwest:

Since 1906, we’ve been providing tug services in the San Francisco Bay. Today, we serve the entire Bay Area region, utilizing technologically advanced and powerful Z-Drive tugs manned by experienced crews. Our tugs are available to assist in the docking, undocking and towing of container ships, car carriers, tankers and other types of vessels entering and leaving the region.

Further, our tugs are specifically designed to provide tanker escort services to ensure safe passage in and out of the San Francisco Bay refinery ports.

Our harbor tug services are backed by solid environmental, safety, and quality assurance programs, with all crews and shore-side support personnel dedicated to providing customers with the best service and the assurance that the job will be done right the first time, every time. 

The following tugs are in operation in the Bay Area:

Our agile and powerful tugboat fleet provides harbor ship assist for safe entries and departures from this Southern California port complex.. We have three tractor tugs operating in the area, which provide agile maneuvering and control. We also have a new, Rapport-designed tractor tug to serve the region that provides Tier IV emission compliant engines with 90 tons of bollard pull for the biggest tankers calling the region.

These capabilities are particularly important to efficiently assist vessels in and out of the many berths of the two busiest container ports in the country. Furthermore, the State of California has declared Crowley tugs as capable of the most difficult tanker escort work in the Los Angeles and Long Beach harbors.

The following tugs are available in the Los Angeles region:

We provide tug services in the Port of San Diego, California, utilizing modern tractor and Z-Drive tugboats specially designed for harbor work to ensure safe passage in and out of this specialized port. These vessels, the highest horsepower tugs in the area, are manned by highly experienced crews available to assist in the docking, undocking and towing of container ships, car carriers, tankers and other types of vessels entering and leaving this Southern California port. 

The following tugs are in operation in the Port of San Diego:

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