Ever heard of a 'porthole' style bulk bag?  If you haven't we'll fill you in.  If you have, and you're having problems with them, we'll list what you need to know.

A porthole bulk bag has a porthole in its bottom.  A flat bottom liner is inserted into the bag and filled.

Porthole syle bags are discharged using a bulk bag unloader that features a 'knife' to cut the liner through the porthole. 

1. Stuff the liner properly.  One of the key benefits of using porthole style bags for in-house use (you fill and empty the bags within your plant) is that the outer bulk bag can be reused by simply discarding the old liner and stuffing a new one into the bag.  However, unless the liner is properly reinserted, twists or folds can occur that will prevent the liner from being easily cut by the discharger.  This can lead to shredding of the liner - resulting in downstream product contamination - or a badly twisted or folded liner can seriously impede or even prevent easy product discharge.  Work with your bag/liner supplier to develop a Standard Operating Procedure to ensure the liner is properly inserted.

2. Keep the knife sharp.  This advice might seem counter intuitive from a safety perspective.  However, unless the bulk bag discharger knife is sharp you run the risk of tearing the liner instead of cutting it cleanly.  Tearing through the liner can sometimes result in shredding, which in turn can deposit liner material in the product flow.  Product contaminated with liner shreds is a serious problem to be avoided at all costs.

3. Use the bulk bag discharging equipment properly.  A knife style discharger will have a particular procedure that needs to be followed to ensure trouble free cutting of the liner and complete discharge of the product.  Make sure you confer with your equipment supplier to develop a proper procedure for unloading porthole bulk bags.