Globalization has increased supply and demand for almost all types of goods worldwide, including perishable products such as meat, fish, dairy, and temperature-sensitive pharmaceuticals (vaccines, antibiotics, etc.).

These products are likely to spoil, decay, become unsafe to consume, or even lose their structural integrity if not kept refrigerated during the entire supply chain process. 

While transporting perishable goods across large distances used to be a logistical challenge, the freight industry has come a long way in light of rapid technological advancements in every mode of transport – air, sea, road, and rail. 

Today, air freight is the fastest and most effective way to move perishables across long distances. However, it’s less environmentally friendly and much more costly, compared to other modes of transport.

As a result, sea freight is often the preferred method of moving perishable cargo using refrigerated container ships, due to their ability to transport intermodal reefer containers, increased container capacity, and cost-effectiveness.

In essence, refrigerated container ships, or reefer ships in short, are specialized ocean vessels equipped with climate control systems that can provide continuous power to reefer containers.  

In this article, we’ll explain in detail how they work, what container sizes they support, and the main types of cargo they transport. We’ll also briefly talk about the loading and unloading process in a typical transit.  

What Are Refrigerated Container Ships?

Refrigerated container ships are large ocean vessels that are designed to transport reefer containers. They are used to transport temperature-sensitive cargo (such as meat, dairy, vegetables, fruits, and more) from one port to another.

Refrigerated Container ships
Refrigerated Container Ship Carrying Reefer Containers © N. Johannes

Refrigerated container ships also provide shippers with a more cost-effective freight solution as they can carry large amounts of cargo in a single trip in comparison to cargo planes. 

How Do Reefer Container Ships Work?

In terms of design and structure, reefer cargo ships feature the following components: 

  • Insulated cargo space
  • Air circulation systems
  • Power supply for reefer containers
  • Compressors, evaporators, and condensers
  • Control systems (temperature & humidity)

Cargo Space

The insulated cargo space is made of walls consisting of polyurethane foam between steel plates along with a powerful circulation system that replaces the air inside of the insulated space from the surrounding environment. 

Power Supply

Refrigerated cargo ships are powered by a dual-powered generator capable of running on both electricity and fuel. Other components include compressors, evaporators, and condensers that work together to reduce the space temperature to a range of -4 to 86 degrees Fahrenheit (-20 to about 29 degrees Celcius).

Temperature Control

Reefer cargo ships also contain dedicated humidity and temperature control systems designed to ensure optimum humidity and dissipate heat as required. Once containers are inspected and loaded, the refrigeration system kicks in and segregates the cooling for different sections of the ships containing cargo.

Cargo types that may require different humidity and temperatures include electronics, meat, pharmaceuticals, and more. Once the ship arrives at the destination port, the cargo is unloaded according to standard operating procedures. 

The History of Reefer Container Ships

Most experts postulate that reefer cargo ships have been around since ancient times. The key difference was the use of ice as an integrated cooling process, rather than a sophisticated refrigeration system.

The first vessels specially designed for perishable cargo transportation were introduced in the 1870s. In 1874, shippers started transporting frozen beef from America to London using an insulated cargo space cooled with salt ice.

In the same year, a French Engineer named Charles Tellier integrated three refrigeration machines onto a French vessel to transport beef from Argentina to Europe. 

Five years later, in 1879, a British Vessel called Strathleven featured the world’s first air refrigeration system on a streamer and transported around 40 tons of mutton from Sydney to London. 

Over the next few decades, refrigerated container ships have tried and tested different cooling technologies and evolved significantly. Nowadays, reefer vessels can transport thousands of refrigerated shipping containers at a time.

What Container Sizes Do Reefer Vessels Support?

Reefer vessels are designed to transport refrigerated intermodal shipping containers (also known as reefers in short) across long distances. These containers are available in three different sizes, as explained below:

20-Foot Reefers

20-ft reefers are the most popular refrigerated containers available in the market. They provide approximately 27 cubic meters of thermally-regulated cargo space with the following dimensions:

Height7′ 1″
Length17′ 10 1/2″
Width7′ 5 3/4″
Volume Capacity28,1 cbm / 1,006 cbft
Weight Capacity70,547 lbs

40-Foot Reefers

40-ft reefers are containers equipped with a refrigeration system to transport dry perishable cargo. Learn more about their dimensions and capacities below: 

Height7′ 10 11/64″
Length39′ 5 37/64″
Width7′ 8 33/64”
Volume Capacity67 cbm / 2336 cbft
Weight Capacity58,863 lbs

40-Foot High Cube Reefers

40-ft high cube reefers offer an additional foot of height than 40-ft standard reefers. They’re used to maintain extremely low humidity and temperatures below -10 degrees Fahrenheit. Learn more about their dimensions and capacities below:

Height7′ 11 1/2″
Length38′ 1/4″
Width7′ 6 1/8”
Volume Capacity67.7 cbm / 2,387 cbft
Weight Capacity74,956 lbs

What Types of Cargo Are Transported on These Vessels?

Refrigerated container ships have become an essential part of cold chain logistics. Although they can’t provide extreme cryogenic temperatures, they’re extremely viable for relatively shorter journeys across the sea.

Below is a list of the most suitable items for reefer cargo ships:

  • Fruits & Vegetables – Reefer cargo ships are commonly used to transport export fruits and vegetables across different countries without spoilage. Popular examples include apples, bananas, potatoes, onions, and citrus fruits. 
  • Meat – Meat requires consistent cooling with minimal temperature fluctuations to remain fresh for longer periods. Refrigerated container ships enable safe and efficient meat transport over vast distances. 
  • Dairy Products – Dairy products are extremely temperature-sensitive. As a result, most shippers transport cheese, milk, ice cream, and similar products in controlled environments. 
  • Frozen Foods – Frozen foods like packaged meats, pre-cooked meals, diced vegetables, etc., require near-cryogenic temperatures to remain fresh. These items are suitable in refrigerated container ships that can drop as low as -13 degrees Fahrenheit. 
  • Flowers & Plants – Flowers and plants need a controlled environment with specific temperature and humidity settings. Refrigerated container ships can provide an ideal environment for safe transport and prevent them from withering. 
  • Beverages – Many beverages, like beer, wine, and milk require cold storage. As a result, many companies use refrigerated container ships for export across different countries. 
  • Chemicals – Chemicals like alcohol, esters, ketones, and various types of acids require near-freezing temperatures for safe transit. As a result, manufacturers utilize reefer cargo ships for sustainable and secure transport. 

Loading and Unloading of Reefer Ships

Reefer container ships are loaded and unloaded just like any other standard container ship. Carriers transport reefer containers to a port via a reefer truck or train and load them onto vessels from the container terminal following a thorough inspection to ensure they meet the required safety standards. 

Below is an overview of the process:

  • Containers are delivered to a seaport through the use of semi-trucks.
  • Once the containers are offloaded, they are brought to a temporary yard, where they are held until the reefer container ship arrives.
  • A gantry crane lifts the laden containers onto terminal tractors and positions them at the dock or quay.
  • Port cranes are responsible for positioning the container to their designated slots on the reefer vessel before they are secured using twist locks. 
  • The process is repeated until all the reefer containers have been loaded onto the vessel and secured in place. The vessel is then ready to depart.

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Gerrit Poel

Co-Founder & Writer
at freightcourse

About the Author

Gerrit is a certified international supply chain management professional with 16 years of industry experience, having worked for one of the largest global freight forwarders.

As the co-founder of freightcourse, he’s committed to his passion for serving as a source of education and information on various supply chain topics.