Read on to learn how to fill lined bulk bags.
Typically, bulk bag liners are made from polyethylene film and are, in effect, ‘inner bags’ that are placed within a bulk bag or FIBC. The product contacts the liner not the bulk bag.
There are generally two types of liners: loose and form fit.
- Loose liners: a cylinder of PE film that is stuffed into the bag. Loose liners are occasionally glued to the bulk bag.
- Form fit liners: a PE film ‘container’ that looks just like a bulk bag (four sides, top and bottom, inlet and outlet spouts) that is placed within the bulk bag. Often, form fit liners are attached to the bulk bag by various methods including tabs that are sewn into the top (and sometimes bottom) seams of the bag.
Filling Bulk Bags with Loose Liners
The most critical factor in filling a bulk bag with a loose liner is to ensure that the liner has expanded and ‘taken’ the cubic shape of the bulk bag before it is filled. Otherwise, there is a high probability that the unexpanded loose liner will have folds in it that the product will fill
over thereby making it extremely difficult (if not impossible) to discharge.
Blowing air into the liner, generally referred to as inflation, is the quickest and easiest method to expand a loose liner. A fan blower can be used or a device called an eductor connected to a source of compressed air that draws in ambient air are the two most common inflation methods.
The other consideration when filling loose liners is to allow the inlet of the liner to slide down as the bag is being filled while still maintaining a secure grip. If the liner inlet is held so that it cannot move it is highly likely the top corners of the bag will not be filled because the liner will form a peak extending from the fill head where it is clamped to somewhere down the sides of the bag. In this case it would be impossible to fill the bag to target weight unless the bag is significantly oversized.
Filling Bulk Bags With Form Fit Liners
If your bulk bag filler is designed so that the bulk bag rests on a pallet or other flat surface throughout the filling cycle even bags with form fit liners that are attached to the outer bulk bag should be inflated. Otherwise, as with loose liners, the bag may be folded or creased in such a way that the product will fill over the folds or creases thereby impeding discharge and the ability to completely fill the bulk bag.
However, if your bulk bag filler features ‘hang filling’ where the bulk bag spends part of the filling cycle hanging suspended from its loops, inflating form fit liners is unnecessary.
