Managing Condensation Inside Shipping Containers
Although Port Containers USA’s watertight, steel shipping containers are built to withstand the most violent storms and keep ocean waves at bay, the pervasive issue of internal condensation is shared by all 17 million boxes estimated to be in existence around the world. Fortunately, the finest brains in the engineering world have been researching the problem for many years and come up with a range of increasingly smart solutions.
Why Condensation Occurs
Moisture tends to accumulate on the interior of the roof and top six-inches of a container’s corrugated steel side walls. It’s often caused by a combination of damp or wet goods, including uncured timber, plants or farm produce, combined with differentials in external and external temperatures.
Another scenario in which condensation frequently occurs, is when a Conex box is loaded in the humid conditions of the tropics, then shipped to the cooler, temperate climate of a location like New Jersey. Those opening the containers are often surprised to find moisture streaming down the walls and shrink-wrapped goods, despite the absence of obvious leaks in the steel superstructure or doors. This unwelcome phenomenon is sometimes referred to in the shipping trade as ‘cargo sweat’ or ‘container rain’. It’s the same principle at work as when steam in your bathroom condenses on a cold mirror.
This isn’t a major problem during relatively short journeys but can cause damage to perishable loads and lead to the smell of mildew pervading items like curtains, carpets and clothing, when a shipping container is used for medium to long-term storage purposes. For these reasons, it’s best to employ some tried-and-tested counter-measures to protect vulnerable contents.
Ways to Combat Condensation
The condensation issue is one experienced by all sizes of container, from 8-feet to 40-feet, and the preventative measures are the same in each case.
Ventilation is a common answer to unwanted moisture – just like opening your steamy bathroom’s window! Shipping container vents usually take the form of several holes punched through the corrugated steel walls, just below the top rail, but with external brackets welded or riveted across them. This promotes airflow but ensures the structure remains watertight. Although vents can be useful, they are limited in size and effectiveness, due to the need for units to remain watertight. Airflow can be further restricted when shipping containers are stacked tightly together on board a ship. For this reason, it’s best if additional vents are located at the ends. If you are storing dry cargo vents alone should be adequate for a limited period but it’s best to supplement them with other measures.
De-humidifiers can come in handy in a storage situation. They need an external power source and work by sucking air in at one end, removing any moisture present, and blowing dry air back out into the container. The moisture is collected in a reservoir for later disposal or can be channelled outside.
Absorb-poles are another useful alternative to dehumidifying the air. They rely on salts that absorb moisture and turn it into a gel that can later be removed. Because they are unobtrusive and non-mechanical, they make an effective budget option.
Choose One of Our Insulated Containers
Port Containers USA’s insulated shipping containers in several sizes are also excellent at preventing condensation, particularly when combined with one or more of the above methods.