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  InterBULK USA, LLC
  29A Lafayette Street
  Arlington, MA
  02474
 
  InterBULK Canada, Inc.
  4851 Singer Court
  Regina, SK
  S4X 4T5

  Phone: (888) 547-8513
  Fax: (888) 511-4805
  sales@inter-bulk.com

   The Right Design for Your Bulk Bags
Determine Size Requirements for Bulk Bags
The bulk density of the product to be packaged will dictate the size of the intermediate bulk containers required. Given that bulk bags are flexible, a dense product usually requires smaller polypropylene bags than lighter products. Factoring in the amount of "stretch" the bulk bag will display is somewhat complicated, however, you can readily calculate your size requirements if you have the following information available:
1. The product bulk density (lbs./cubic foot) of the product
2. The maximum allowable filled width
3. The total weight to be shipped per bulk bag

Example:
Customer A wants to ship Agricultural Limestone using InterBULK bulk bags. The method of transportation will be enclosed vans and trailers that have an internal width of 8 feet or 96 inches and the bags will weigh exactly 2,205 lbs when filled. The bulk density of Agricultural Limestone is 68-lbs./cu. ft. (this information is usually supplied by the company). What size bulk bags do we need here?

The first step is to figure out the volume of the bag needed. If we are filling a bag with 2205 lb weight then the volumetric capacity must be 2,205 lbs/68lbs per cu. ft. = 32.43 cubic feet total.
If polypropylene bags must stack to fit side by side on a truck, they can be no wider than 48 inches. Bulk bags have an average expansion rate of 120% of empty capacity when filled. To ensure loading fit in this case, the empty dimension must be 38 inches or less. In calculating width, it is better to allow for room between intermediate bulk containers. Packing bulk bags too tightly can cause excessive rubbing and tear.

In considering the above factors, the bag InterBULK chose to supply was 35 x 35 x 40 inches. We know this bulk bag will expand to 42 inches when filled. This bag has an empty capacity of 28.36 cubic feet and will hold 34 cubic feet filled (28.36 cu. ft. x 1.20 = 34 cubic feet).

Note: It is always important to factor in the expansion rate when determining the capacity and width formula. Bag handling and product settling can increase expansion of flexible intermediate bulk containers as much as 128%. It is also recommended not to exceed a 2 to 1 height to width ratio to prevent the polypropylene bags from tipping.

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