Before we get started, we should clarify that barges and cargo ships aren’t actually the same thing. While barges do carry a lot of cargo, they are a subcategory of ship. Cargo ships are always self-propelling, but barges have to be towed and are primarily meant for large rivers or canals. Either way, they are both extremely heavy. How heavy?
A Barge ship’s or cargo ship’s weight depends on its size, shape, and how much freight (cargo) they carry. Dry bulk cargo ships can weigh as much as 200,000 tons, while some liquid barges will weigh 100 to 200 tons more. The greatest factor in a barge’s weight is dead weight.
Of course, there’s more than one kind of barge and more than one kind of cargo ship. That was just the average weight. To learn more about each barge and cargo ship type, what they weigh, why they weigh that much, and more, keep reading.
How Much do Cargo Ships Weigh?
In the maritime categories, there are technically 4 types of barges, but one of those types have 5 of its kind beneath it. Meanwhile, there are 8 different types of cargo ships, including barge vessels.
Since they are almost interchangeable, we’ll keep them together. They are categorized not only by how large they are, but also by what their utilization is and how much cargo they can carry. Below are estimated weights. They are not entirely accurate, but they do give a good idea of the approximate weights by deadweight tons (DWT).
|Type:||Estimated Empty Weight (in tons):||Carrying Capacity (in tons):|
|Deck Barges (Inland)||43730||12,000|
|Spud & Crane Barges (Inland)||39198||230|
|Hopper Barges (Inland)||20102||1250|
|Shale Barges (Inland)||5572||1500|
|Liquid Mud Barges (Inland)||6835||259|
|Project Cargo Barges||176720||1632933|
|Dry Bulk Vessels||200,000||200,000|
|Split Hopper Barges||31313||72511|
|Submersible Barges||62037||10,435LT (light tons)|
Why Are Barges So Heavy?
The biggest culprit of a barge’s weight is the cargo. The standard cargo shipping container sizes are 20’L x 7.7’W x 7.9’H and 40’ x 7.7’ x 7.9’. They are made of either aluminum or steel. The aluminum containers will normally allow a larger payload of goods, but the steel will give a larger internal area for storage.
90% of all goods are shipped within these particular dry good containers. The tare weight (weight of the empty container) of the shorter freight is 5,071.5 lbs (2,300kg) and the larger freight is 8268.8 lbs (3,750kg).
Each cargo ship has a particular carrying capacity based not only on their size but also their shape. Their shapes allow them to be better suited for certain goods and loads. So each particular shape and their total deadweight capacity (load capacity) is as follows.
|Shape Type:||Deadweight Cargo Capacity (varied units of cargo capacity):|
|Crude carrier||2,500,000T (2.5MT)|
|LNG carrier||70,000 – 120,000DWT|
|Chemical||5,000 – 35,000DWT|
|Livestock||2,000DWT – 25,000DWT|
|Heavy-lift||13,000DWT – 26,000DWT – 100,000DWT|
While we have mentioned cargo in particular, a ship’s deadweight is the total weight that a ship can carry, which also takes into account crew, fuel, the supplies for the crew (i.e. freshwater and food), ballast water (water that is in the hull), and even the propellant system.
The only factor that adds to the deadweight capacities we’ve listed is the materials the ship was made with and their size.
Barges are typically constructed with a wood (often mahogany) or steel hull that is connected by “stringers,” which are wood or iron cross-members. Shale barges are an exception. They are constructed with concrete.
Genuine mahogany weighs 40lbs per cubic foot, the density of steel is about 7.8g per cubic cm, and concrete weighs 150lbs per cubic foot.
The larger a barge is, the more materials are needed for its construction and the heavier it will be. Each type of barge’s dimensions are widely varied.
|Type:||Dimensions (Min & Max):||Estimated Weight in Tons:|
|Deck Barges (Inland)||60’ x 26’x 5’ to 282′ x 54′ x 12’6″||142T – 43730T|
|Spud & Crane Barges (Inland)||30′ x 110′ x 7′ to 70′ x 195′ x 10’6″||419T – 39198T|
|Hopper Barges (Inland)||195′ x 35′ x 12′ to 200′ x 35′ x 13′||1486T – 20102T|
|Shale Barges (Inland)||110′ x 30′ x 7′ to 195′ x 35′ x 12′||1572T – 5572T (not accounting rebar)|
|Liquid Mud Barges (Inland)||130′ x 34’ x 7’||561T – 6835T|
|Crane Barges||30′ x 110′ x 7′ to 70′ x 195′ x 10’6″||419T – 33168T|
|Ocean Barges||140’ x 40’ x 9’ to 400’ x 99’9” x 20’||914T – 176720T|
|Project Cargo Barges||140′ x 40′ x 9′ to 400′ x 99’9″ x 20′||914T – 176720T|
|Dry Bulk Vessels||427’ x 10’ to 1400’ x 200’||77T – 200,000T|
|Tank Barges||107’ x 27’ x 7.2’ to 443’ x 72’ x 14.4’||377T – 101460T|
|Split Hopper Barges||164’ x 30’ x 10’ to 225’ x 45’ x 14’||893T – 31313T|
|Submersible Barges||276’ x 77’ x 3’ to 472’ x 119’ x 5’||1157T – 62037T|
Does a Barge’s Weight Affect Their Speed?
In everyday physics, the heavier an object is the more it resists any change to its speed. Heavier objects will also maintain their motion longer than lighter objects. This resistance to change in motion is caused by an increase in inertia.
In other words, barges and cargo ships are exceptionally slow. The average speed of a cargo ship, which has its own propulsion system, is between 20-26 knots. 1 knot is approximately 1.15mph, making the average speed of a cargo ship 20-30mph.
Tankers and dry bulk carriers can usually move between 10 – 15 knots (11.5 – 17.25mph) because of their much larger loads.
How are Barges and Cargo Ships Transported?
The journey of a barge from being built to common necessary transport is interesting. All barges are built in shipyards (a.k.a dockyard). This is also where they are repaired. Whether what is being built is a
- Deck barge
- Ocean barge
- Hopper barge
- Cruise ships
- Cargo ships
Transport from the Shipyard
Construction is a tricky art on its own. While construction is done offshore, barges aren’t built on the ground. A barge is kept in the air by being built piece by piece on a series of pads and bars. Barges are constructed as close as possible to the ocean or large river they are next to.
The process isn’t graceful and it looks as dangerous as it sounds. Sometimes the builders don’t even know how they’re going to get a massive hunk of floating metal into the water exactly. What can happen is the barge is pushed on its Teflon pads during high tide so that the water is as close as possible. CATs will usually be responsible for the pushing, and then the barge is literally dumped into the water, like this.
Transport in the Water
This isn’t the end of the question, of course. Some of you may not have known this, but most barges are not built with their own propulsion systems. Cargo ships do have their own slow mechanical marine propulsion system, but barges do not.
Once a barge is in the water, it relies entirely on tugboats to take it from one location to another. Cargo ships do need tugboats in order to get started out of the harbor, and because of their cumbersome size, tugboats are necessary to help them maneuver around other craft as they pull into the harbor.
If you’ve seen a tugboat, the first thing you’ve noticed is its small size. It’s common to see an ocean barge being guided by a single tugboat a fraction of its own size, and you have to wonder how they do it.
If we take McDonough Marine Services as an example in marine transport, this company owns and operates tugboats and push boats that range from 600HP to 2200HP. Enough horsepower for all kinds of barge jobs.
There are several ways tugboats operate with barges. The typical arrangement they take is to attach a “towing bridle” to the barge or cargo ship made with two lines. Then, a third line is connected to the towing winch of the tugboat. There will either be a single tow, double tow, tandem tugs, or breasted tugs.
It might seem bizarre that our cargo ships have to go so slow and even need to have a boat a fraction of its size to help it get started, but we do it this way because it works. Amid the clumsy and dull appearance is careful calculating, scientific principles, and a lively crew doing everything in their power not to let the ship sink.
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