post by David Parrin, Senior Advisor Cordstrap Knowledge Center
In a previous post I answered a question we regularly receive about the use of dunnage air bags in airplanes.
Another question we are often asked at Cordstrap Knowledge Center is if inflatable dunnage bags can be used to secure cargos inside reefer containers. Luckily the answer is YES. Due to the lack of lashing points in a reefer container, dunnage bags are one of the few securing methods available. However, care has to be taken that they are used properly to allow unhindered air circulation and prevent loss of pressure in the bags.
Temperatures inside reefer containers can go down to -23°C (-9.4°F). I am sure you could imagine that filling the dunnage bag during the summer at an outside temperature of 25°-30°C (77°-86°F) and then cooling to -23°C (-9.4°F) could lead to the bags hanging loose in the gaps between the cargo.
The bags will of course lose some pressure but, in the example above and at a maximum filling pressure of 0.2 Bar (20 kPa), Boyles’s Law tells us that the pressure change will be only around 16% as the temperature drops down to -23°C (-9.4°F).
Filling each bag up to the maximum filling pressure (taking care as always not to damage the packaging), waiting a couple of minutes to allow the pressure in the bag to settle and then adding a little more pressure will compensate for the expected small pressure drop.
To allow an unhindered flow of conditioned air around the cargo there are a number of important points to be taken care of during loading:
1. Never load the reefer beyond the red “No cargo above this line” indicators in the reefer.
2. Always leave sufficient room between the dunnage bag and the floor and/or roof of the reefer container to allow the air to circulate fully around the packaging. Failure to do this could end up with blocking the air flow resulting in possible damage to the product being transported.
3. When dunnage bags are used down the center of the reefer, allow sufficient space between the bags to allow the air to circulate freely around the cargo.
4. Do not use dunnage bags between the cargo and the doors as this will prevent the necessary air-flow and could lead to doors bursting open at the destination.
Hopefully you found this article helpful. I love feedback, so feel free to share your experience, questions, critique or wisdom in the comment box below.