The Dunnage Bag Solution
The simple solution to the problem is to fill up the voids amongst the cargo loads . Seems like
the dunnage bag is perfect for this job.
What Is A Dunnage Bag?
Essentially it consist of a plastic air bladder fitted with a one-way or two-way valve and placed
inside a paper bag ( single or multiple ply ) or a polywoven bag .The outer bag serves to
protect the inner bladder and to give it strength when inflated.
Other names used for dunnage bags are air bags, disposable inflatable dunnage and
Dunnage bags are normally specified by size ( the uninflated width and length) and working
( or operating) pressure as these attributes determine the force the bag can generate when
The common working pressures are 10kPa(1.4psi), 20kPa(2.9psi),40kPa(5.8psi) and
60kPa(8.7psi). For paper dunnage bags, this roughly correspond to 1-ply for the 10kPa, 2-ply
for the 20kPa , 4-ply for 40kPa and 6-ply for the 60kPa bag.In the case of polywoven dunnage
bags, there is only one layer for the outer bag and the density (gsm) of the woven fabric is the
main determinant of the working pressure.For a given working pressure,the force generated is
directly proportional to the size of the bag . The force needed to restraint the cargo loads
inside the container is a largely dependent on the gross weight of the cargo.
It is important to select the correct size to fit the gross height of the stacked cargo loads
inside the container. The force transmitted is directly proportional to the contact surface area
with the cargo load .It is good to have as as much of the cargo load surface as possible
covered by the dunnage bag.
The inflated bag is rounded at the top and bottom. This gets progressively worse (for a bag of
given size ) as the bag becomes thicker ( or as the void becomes bigger) . The maximum
thickness ( the maximum void size it can fill) is largely determined by the width of the bag.
Only the flat part of the bag surface remains in contact with the cargo load .Therefore, the
void determines the effective contact area for a given bag width.It is recommended that at
least 50 percent of the surface area of the bag should be in contact with the cargo load .
|Width of bag
||Recommended Max. Void