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What is a Reefer Container?

MAY 24, 2021 BY RYAN STOLTZ

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Reefer containers have a long history, dating back to over 40 years. Early refrigerated containers (or Reefers) primarily found applications in transporting temperature-sensitive products and perishable cargo over long distances.

Today, restaurants, farming operations, and packing houses are increasingly using refrigerated containers onsite.

In addition, several industries worldwide have begun using refrigerated shipping containers as coolers or freezers.

Reefer container units are ideal for temporary storage needs during renovations and creating additional storage during seasonal peaks, keeping fruits, vegetables, meat, and pharmaceuticals at the desired temperature.

 

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How Does a Reefer Container Work?

A generator set (or Genset) attached to the container provides the container with cooling and electricity. As reefer containers help in the transportation of perishable goods, these generator sets are usually a combination of fuel-powered and electric-powered.

The dual-generator source allows the container to work both overseas and on the road by a truck. Another advantage of having dual-powered reefers is that these units can maintain your shipment's temperature even in the most adverse conditions.

Reefer containers have specially designed floors with grooves, known as  T-shaped decking.  The T-shaped flooring profile helps the container distribute cold air from the bottom.

There is a consistent supply of chilled air in the reefers around the entire shipment.  This cool air from the unit blows through the vents from the bottom to the back door. Warm air from the top of the container flows back to the refrigeration unit, where it chills again and returns to the interiors.

Some reefers also allow fresh air from the environment to enter the refrigeration cycle. As fresh air flows in, carbon dioxide and ethylene-filled air move out from the container. These containers prevent the premature spoilage of fruits.

Please note that reefer units only maintain the pre-cooled cargo temperature for the time of transport. They do not generally reduce the cargo temperature during transportation.

Types of Reefer Containers

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There are a variety of refrigeration units available in the market these days.

Each container differs according to the service condition, efficiency requirements, and the cargo they need to carry.

One-Trip Containers

One-trip reefers have made just one trip across the ocean and will arrive in excellent condition, with all sections working reliably. A one-trip reefer unit can achieve extremely cold temperatures.

Used Containers

Used containers are a more affordable option for businesses that don't have the means for high upfront investment. A used refrigeration unit might likely sustain some wear and tear throughout its lifecycle but still deliver adequate functionalities. It is crucial to inspect any temperature-controlled used reefer before purchase to ensure the cargo doors open quickly, there is perfect air exchange, and the conditions are cold enough to store chilled goods.

Closed Reefer Containers

A closed reefer container is a single unit with an automatic heating and cooling system which runs exclusively on electricity. These units primarily function as cold storage and are not generally used for transporting goods.

Modified/Controlled Atmosphere(MA/CA) Containers

These containers use an air exchange system to maintain an ideal set temperature, humidity levels, and ventilation for dedicated cold products that require a specific environment.  MA/CA reefers are also heavily insulated, which helps in temperature control.

Automatic Fresh Air Management (AFAM) Containers

AFAM reefers are the most advanced type of temperature-controlled reefer units.  These containers use a control unit that automatically regulates the air exchange inside to maintain the required temperature. With such precise levels of control,  you can influence or extend the shelf life of the goods stored inside.

What are the Components of a Reefer Container?

The components of a reefer container include:

  • Interior fans: Interior fans help maintain and circulate adequate airflow to ensure temperature control.
  • Control unit: You can set the cooling parameters such as temperature, humidity, and ventilation with the help of a control unit.
  • Fresh air vent: Atmospheric air from outside enters through this vent while harmful fruit-ripening gases, such as ethylene, leave from this duct.
  • Unit evaporator:  The evaporator unit heats or cools the circulating air inside the container to drain excess moisture.
  • Condenser: There are two types of commonly-used condensers in reefers: Air cooling and Water Cooling system. The Air-cooled condenser section helps pull cool air from the top of the container and discharges it under the cargo.

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Features

There is a wide variety of reefer containers available in the market. Each unit comes with special features to accommodate different kinds of reefer cargo. These are some of the unique features of refrigerated shipping containers:

1. Temperature

Refrigerated containers are capable of controlling temperatures ranging from  -30°C and +30°C. A reefer container comes equipped with refrigeration equipment required to store perishables, frozen goods, and pharmaceuticals.

2. Size

Reefers are most widely available in the standard 20-foot size for shipping containers. However, you can also opt for forty and forty-five-foot units for ample volume storage.  Another variant is a high cube reefer container that can accommodate taller chilled cargo.

3. Material

Most refrigerated containers have a corrosion-resistant Corten Steel body, providing strength and high durability, allowing stacking of refrigerated units alongside regular containers.

4. Power

A reefer container requires an external power supply to provide cooling electricity. Most containers receive electrical power from the ship during sea transport. On land, a reefer container derives power from a diesel generator set. Reefers generally require three-phase high voltage electricity.

5. Refrigerant

Similar to refrigerators, reefers rely on a thermodynamic process known as the vapor-compression cycle. The operation revolves around specific components, including a compressor, condenser, evaporator, and expansion valve.

6. Insulated Walls

The walls of these refrigeration units lie between stainless steel panels located on both sides of the insulation. While standard cargo containers come with concealed plumbing and electrical lines, reefers feature externally mounted electrical outlets and plumbing fixtures.

7. Aluminum Floors

Refrigerated reefers have aluminum flooring carved into a T-shaped profile. The T-floor design keeps the contents of the container elevated so that cold air can circulate underneath.

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Benefits

Some of the advantages of using a reefer are as follows:

  • Reefer boxes are self-contained that don't need additional cold storage after delivery.
  • They help improve the shelf life of goods by circulating fresh air.
  • You can choose from a wide range of sizes and easily transport reefers by water, road, and air.
  • Even in harsh environmental conditions, reefers deliver excellent performance in the desired temperature.
  • Reefers are cost-effective as they offer better returns in the long run.

How are Reefer Containers Different From Fridge Boxes?

While reefers are full-fledged service containers, fridge boxes are individual units used to store up to two pallets of cold storage.

A fridge box features well-engineered seal technology and equipment that can maintain the temperature within one degree for up to five days.

Fridge boxes are much smaller in size and relatively less expensive. You can also ship fridge boxes to keep small volume products cold while shipping warm goods in the same container.

What is a Reefer Container Used for?

The most common applications of a reefer container are as follows:

1. Fruits and Vegetables

Reefer containers remain the preferred mode of transporting fresh produce worldwide as they are incredibly effective at keeping produce fresh.

2. Meat and Poultry

Refrigerated units can keep meat at -18 degrees or below as they circulate temperature-controlled air. The airlocked cold tunnel keeps poultry and meat fresh for extended periods.

3. Medicines

Reefers can help transport essential medicines across continents without letting the external weather adversely affect their potency.

4. Disaster Relief and Healthcare

Reefers allow aid workers to deliver food, medications, and equipment to disaster sites in top condition and assist in prompt relief and rehabilitation during unprecedented times.

Learn more about the uses of reefer storage containers.

Reefer Temperature Control for Frozen and Chilled Cargo

Internal air circulation is essential for temperature control in reefers. The type of insulation also plays a crucial role in maintaining the optimum temperature.

There is a constant flow of hot air inside the container from two sources: the external environment and internal heat from fruit ripening. Keeping goods next to each other reduces the gaps and helps prevent the accumulation of heat.

Reefers remove the excessive buildup of heat through fresh intake of air from outside. Advanced units use automated humidity control elements and data loggers to maintain optimum temperature.

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What is a Reefer Pre-Trip Inspection?

A pre-trip inspection (PTI) of reefers can ensure that your unit is functioning correctly. PTI also helps avoid hassles that may crop up later during service. A basic PTI check includes checking the container for loose connections, damaged and missing components, refrigerant levels, and electrical utilities.

Once you power on the container, check for any abnormal noises, fan flow directions, and ensure that the unit has calibrated sensors. Switch on the data loggers and check for normal functioning. Lastly, ensure that the temperature and defrost settings are in place and there are no current leakages in the evaporator, compressor, condensers, pumps, and fans.

Safety Precautions

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With a reefer's ability to achieve such low temperatures, it is essential that you cautiously follow the manufacturer's recommendations when operating these containers. Always use personal protection equipment like glasses and safety gloves at all times. You should also:

  • Keep hands, clothing, and tools away from the fan when it's in motion
  • Always work in a well-ventilated area
  • Disconnect the power source before making repairs
  • Use a CO2 extinguisher to put out flames, should they occur
  • Do not bypass any electrical safety device

Common Problems with Refrigerated Containers

Leakages are the most common problem in refrigeration units. Damaged seals around the openings may allow air to escape.

Regular wear and tear may also damage pressure lines. There can also be electrical malfunctions and weakened refrigerants in the container after extended use.

A professional technician can resolve these issues quickly. Regular maintenance and inspection will also help avoid these hassles.

How Much Are Reefer Containers?

A reefer container is a specialized, cold-storage unit that features sophisticated refrigeration equipment and insulation that adds to its cost. Standard reefers cost up to six times more than standard shipping containers.

Several other factors such as service life, condition, additional customizations, partitions, and accessories may add to its cost.

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FAQ

How does a refrigerated container work?

Refrigerated shipping containers operate in the same way as refrigerators. However, they contain a specific T-shape flooring system that allows cool air to flow underneath. The design of these "bottom air delivery" units guarantees a great atmosphere and the ability to preserve cargo by providing a consistent supply and the perfect exchange of air.

How much does a refrigerated container cost?

A new 20' refrigerated shipping container has an average cost ranging from $5,600 to $7,000. Used 20' refrigeration units are more affordable and cost anywhere between $3,900 and $4,400. Large 40' containers fall in the $10,000-$12,000 range.

How are refrigerated shipping containers powered?

Refrigerated containers require an external power supply to provide cooling electricity. Each unit gets electrical power from the ship during sea transport. When on land, it receives power through diesel generators.

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