Do you receive ingredient in bulk bags with loose liners?  Do you have problems getting the ingredient to flow from the bulk bag?  Here's some tips on how to overcome bulk bag discharging flow problems.

Focus on how the bags are filled.  

Flow problems often are the result of the bulk bag liner not being inflated prior to filling.  If this crucial step is not taken, the liner can fold over itself in the bottom of the bag.  If that happens and a ton of ingredient is filled into the bag on top of the folds, flow problems are sure to occur.

Optmize liner handling during discharge.  

Liner tensioners are devices that wind up loose liners during discharge to prevent them from 'growing' too far out of the bottom of the bulk bag and becoming entangled in downstream equipment.  They also improve product flow and ensure that all of the ingredient is discharged from the liner thereby providing 100% yield.

Using one of a number of different styles of liner tensioner can prevent flow problems from bulk bags with loose liners.

• Hold in place.  The simplest type of liner tensioner simply holds the liner in place to prevent it from completely exiting the bottom of the bag during discharge.  Make sure that there is sufficient space between the bottom of the bag and the downstream equipment so that when the liner grows out of the bag during dicsharger it doesn't become entangled in downstream equipment.  Also note that this style tensioner does not pull up on the liner and therefore does not do an effective job of ensuring complete discharge.
• Partial wind up.  A pneumatically actuated tensioner winds up a predetermined amount of the liner during discharge - say 24" - 36".  This reduces or eliminates liner growth out of the bag bottom and ensures complete discharge.
• Complete wind up (see photo above).  If you use a discharger that clamps the liner outlet you must use a tensioner that continuously winds the liner.  Otherwise, the liner will gather at the clamp and almost always prohibit ingredient flow.  This type of discharger and tensioner are typically used when dust containment is critical.

Often bulk bags require inner liners, usually made of polyethylene, to protect the ingredient.  Care must be taken when discharging lined bulk bags to prevent entanglement with downstream equipment and to ensure 100% product yield.

Liners come in many forms: loose tubular, loose fitted, sewn-in, glued-in.

Loose means that the liner is not in any way attached to the outer bulk bag.

Tubular means that the liner is basically a cylinder of polyethylene film that is stuffed in the bag.

Form fit means that the liner is constructured with sides, top and bottom and usually inlet and outlet spouts - it looks just like a bulk bag only it is made from polyethylene film.

Loose Bulk Bag Liners

Whether tubular or form fit, a loose liner requires some sort of physical means to prevent it from discharging with the ingredient and becoming entangled in downstream equipment.  A device called a liner tensioner is typically attached to the bulk bag lifting frame or rigging frame to prevent this from happening.

Liner tensioners vary in their operation, but the most basic simply hold the liner in place preventing it from moving out of the bag.  More sophisticated tensioners wind up a portion or all of the liner as it is emptied.

Before the bulk bag is lifted into the discharger the inlet spout of the bag is untied to expose the tied liner inlet.  The liner neck is then wound onto the liner tensioner spool piece, which is then either fixed in place or rotated to take up the slack in the liner by activating its actuator (typically pnemuatic).

Attached Liners

Even though liners that are attached to the outer bulk bag are designed not to discharge with the ingredient, it sometimes happens anyway.  Often a basic liner tensioner that holds the liner in place is used to guarantee that the liner cannot move.

Liner Tensioner Conisderations

1. Liners 'grow'. Loose liners and liners attached to the top of the outer bulk bag will extend out of the bulk bag outlet spout during ingredient discharge.  Particularly in the case of loose tubular liners, care must be taken to ensure that even if a liner tensioner is used, the liner cannot extend or grow out of the outlet spout enough to foul downstream equipment.
2. Too much liner winding.  If a liner tensioner that winds continuously is used typically the liner outlet is clamped to prevent it from winding all the way up onto the spool piece.  If this is allowed to happen, and the ingredient is at all dusty, dust will be sprayed into the surrounding area when the empty liner is rapidly wound up through the empty bulk bag and then spins around the spool piece.
3. Liner length.  When a liner tensioner is used the liner inlet must be long enough to reach the tensioner spool piece.
4. Ensuring 100% yield.  A liner tensioner that winds up a loose liner - partially or completely - can assist with ensuring that all of the ingredient is dishcarged from the liner.  The act of winding up the liner helps to get the last pounds of ingredient out of the bag.

View this content on Spiroflow's main website.

In previous posts we have discussed reducing shipping costs and the benefits of replacing or eliminating pallets.

In this week's post let's discuss all of the ways that the cost of bulk bag packaging can be reduced.

1. Reduce bulk bag size.  Reducing the height of a bulk bag by 10% decreases its price by roughly 5%.  Maximum densification, for example using the cone table densification system, can almost always decrease bag height by 10% - sometimes by as much as 40% or more.
2. Eliminate baffles.  If your bulk bags have internal baffles and they are being used to enhance stability, it is highly likely you can eliminate them by using a densification system designed for maximum results.  Getting rid of baffles can save as much as $5 per bag.
3. Use coated bulk bags.  If you use liners in your bulk bags you may be able to eliminate them and use coated bulk bags instead.  See the blog post "Bulk Bag Liners - When To Use Them... or Not!" for an excellent review on when to use liners and when not to.  Switching from a liner to a coated bulk bag can save as much as $2 -$3 per bag.
4. Replace wooden pallets with plastic channels.  Using plastic pallet replacement channels can reduce direct packaging cost and logistics related costs too.  See the blog post "Eliminate Wood Pallets - Ship Bulk Bags Without Wood Pallets" for details.
5. Eliminate wooden pallets.  Properly designed and filled bulk bags can be handled only by using their lifting loops thereby eliminating pallets - and their cost - completely.  See the blog post "Pallet Free Bulk Bag Handling" for details.

As you can see from there are numerous ways to significantly reduce the cost of your bulk bag packaging.