Training - Critical To Bulk Bag Discharging Success

One of the most overlooked keys to bulk bag discharging success is training.  This post reviews how properly trained operators facilitate a safer, cleaner and more productive bulk bag discharging operation.

Key bulk bag discharging tasks that require specific operator training:

1. Preparing the bulk bag for unloading.  In most cases this is a simple task requiring only the attachment of the bulk bag lifting loops to the lifting frame used to place the bag in the discharger.  However, when certain types of liners are involved the operator must know how to safely use the bulk bag unloader's liner tensioner to hold or wind up the liner during discharge thus preventing it from becoming entangled in downstream equipment.
2. Using bulk bag discharging equipment.  The most common cause of bulk bag discharging problems is misuse of bulk bag discharging equipment.  At best, not following the manufacturer's operating instructions results in poor ingredient yield, unecessary operator involvement to initiate or maintain ingredient flow and/or dusting.  The worst scenario is when an operator's lack of knowledge creates a safety hazard.  This is most often seen when operators reach under an unsupported, suspended bulk bag to untie the outlet and initiate flow.
   
3. Removing the empty bulk bag.  A bulk bag that has just been unloaded is full of dust laden air.  How the operator removes the bag can either maintain a dust free environment or create a dust clogged mess that in some circumstances results in a safety hazard.
4. Disposing of the empty bulk bag.  Even if a bulk bag is removed from the discharging equipment and transported to the point of disposal properly, problems can arise if an operator folds the bulk bag or otherwise expels the dust laden air in an uncontrolled manner - causing a dust clogged mess.

Of course, the first step in sucessfully training operators is to develop well thought out Standard Operating Procedures (SOPs).  With precisely defined operating objectives, tasks and expectations training success is greatly enhanced.

Handling Bulk Bag Liners During Discharge

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.

Handling Hazardous Ingredients In Bulk Bags

Increasingly, bulk bags are used to ship 'hazardous' dry bulk solid materials.  This post investigates what you need to know to handle them.  Note that we will address the topic of how bulk bag manufacturers make bags to meet relevant regulations related to robustness and package integrity in a subsequent post.

First, let's discuss what hazardous means.  The United Nations defines hazardous goods as follows:  "Definition of 'dangerous goods' covers articles or materials capable of posing significant risk to people, health, property, or environment when transported in quantity."

That's a broad definition, but for the purpose of this discussion we'll focus on three potential hazards that can arise during bulk bag handling:

1. Static discharge.  Bulk solids that within a bulk bag may generate enough static charge to iginite flammable vapors, gases or dust.
2. Explosive dust.  Bulk solids whose dust, if allowed to accumulate in a high enough concentration, may explode if exposed to a suitable ignition source.
3. Health hazard.  Bulk solids that present a health hazard to humans via direct contact.

Dissipate Static

There are two ways to mitigate the risk of static discharge: bag and equipment design.

Of the four types of bulk bag (Type A, B, C and D), typically only types C and D are used to prevent static discharge leading to explosions. 

Type C bulk bags feature conductive fabric or conductive threads or filaments woven into non-conductive fabric.  The key factor is that Type C bags must have a grounding point to which all fabric, threads or filaments are connected.  The grounding point must then be connected to an external ground point duing filling and discharging of the bulk bag.

Type D bulk bags are constructed from fabric that allows static charge to be dissipated without being connected to ground.  The advantage of Type D bags is that operators are not required to making a ground connection with the bag prior to filling and unloading - a task that can be forgotten sometimes resulting in disaster.

Equipment used in situations where static discharge could ignite flamable substances must, as a minimum, have ground lugs.  Depending on the Area Classification electrical components may have to be explosion rated.

Contain Dust

If the product you are filling or discharging can cause an explosion if a high enough concentration of dust is exposed to an ignition source, dust containment is critical.

Bulk bag fillers must have 'twin-tube' fill heads and provide a tight seal with the bulk bag inlet spout.  The outer tube of the fill head must then be connected to dust collection system so that dust laden air that is displaced during the filling process is safely extracted.

Bulk bag dischargers must have dust containment features suitable for the hazard level.  There are different levels of dust containment available (discussed in another blog post).

All equipment must feature electric components rated for the Area Classification.

Isolate Human Contact

Bulk solids that are health hazards include various refined metals that are carcinogens, chemical compounds that cause respiratory problems and so on.  When dealing with these products maximum dust containment is required.

Specialized bulk bag discharging equipment is available for this application.  It is critical that such equipment contain dust at the following critical steps in the bulk bag unloading process:

• Initial onset of product discharge.  The point in time when product begins to flow from the bulk bag can create a large amount of dust.
• Throughout bulk bag emptying.  Of course, dust must be contained as the bulk bag is emptying.
  
• End of discharge. Near the end of the discharge cycle the bulk bag will loose its shape.  Equipment must be designed to maintain dust containment integrity at this crucial stage.
  
• Bag removal.  Removing the empty bulk bag - still full of dust laden air - must be done safely without exposing operators to dust.

Further, bulk bags must be designed to prevent the escape of product particles during handling - otherwise referred to as 'sifting'.  Coated or lined bags can be specifically designed to suit the product and the hazard.

This is only a brief overview of handling hazardous goods in bulk bags.  Users and bulk bag and equipment manufacturers must coordinate closely to ensure safety.

Bulk Bag Dusting - What Causes It?

A common rap against bulk bags is that unloading them can be a dusty mess.  In the first of a series of posts related to bulk bag discharging and dusting, let's examine what causes dust emissions.

1. Bulk bag design.  Unless a bulk bag has been specifically designed to contain the fines present in a given product, particles can sift through the bag fabric.  This looks like smoke escaping from the bag as it is being handled and emptied.  Depending on the amount of fines present in the product, the particle size and its shape, coated fabric may be all that is required to contain the dust.  However, in some cases polyethylene liners are required to prevent product sifting. 
2. Onset of product flow.  The point in time when the operator releases the outlet spout tie and product begins to flow can be a significant contributor to dust emissions.  If the product is flowable, when the outlet spout is released a down rush of product can occur - if the down rush occurs quickly this happens while the access door to your bulk bag unloader is still open.  The rapid drop of product causes an updraft of dust laden air that must be extracted properly or it will result in a cloud of dust being emitted into the atmosphere.  Look closely at how your bulk bag discharging equipment is designed to prevent this.
3. Product flow.  Bulk bag discharging equipment must provide suitable dust containment while the product is moving out of the bulk bag.  While this seems obvious, make sure your equipment can't loose its ability to extract dust during the discharge cycle due to the bag moving as it empties thereby altering the integrity of the 'seal' that the equipment relies on to maintain proper dust containment.
4. End of the discharge cycle.  As the final pounds of product empty from a bulk bag it may cause the discharging equipment's dust containment/extraction features to loose their ability to control dust.  This can result from the bag breaking its seal with the equipment as it looses its shape near the end of the discharging cycle.
5. Empty bulk bag removal.  Dusting can still occur even when the bag is 'empty'.  When a dusty product has been discharged from the bulk bag, the bulk bag is still full of dust laden air.  If the bag is removed from the discharger without re-tying its outlet spout the dust laden air will exit the bag in transit from the discharger and spread thorughout the immediate plant area.  Even if the outlet spout is retied prior to removing the empty bag, care must be taken in how it is handled when it reaches the disposal area - a bulk bag can't be folded or compressed without doing something with the dust laden air it contains.  Determine the best Standard Operating Procedure for your situation and ensure that your bulk bag unloading equipment supports it.  It may be necessary to use purpose-built bulk bag folders to make this step of the process dust free.

As can be seen dust containment and extraction must occur at multiple points in the bulk bag discharging cycle to maintain a clean and safe plant environment.  Careful equipment design and well thought out operating procedures are both required to optimize your bulk bag unloading operation.

Porthole Style Bulk Bags - 3 Key Factors To Success

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.

Solidified ingredient in your bulk bags? Find out how to unload them.

There is a surprisingly high number of dry bulk solid ingredients that will 'set up' (solidify) when stored in a container.  This can cause significant problems when the container is emptied... the problem being that if the ingredient has solidified enough it simply won't flow!

In the case of bulk bags filled with solidified ingredient, we have encountered many plants who have devised their own solutions to this problem:

• Hitting the bulk bag with hand held solid objects (pipes, etc.)
• Bouncing the bag on the floor with a forklift
• Driving the bag into a wall or column with a forklift

As you can imagine these so-called solutions are usually somewhat less than effective and are most certainly sub-optimal - most importantly they are unsafe.

What to do?

Pre-condition the bulk bag by using a device such as the Bag Squeezer.  Its name nicely describes its function!

By safely breaking up the ingredient prior to attempting to discharge it, productivity will be improved, dusting will be minimized and safety will be dramatically enhanced.

3 Ways To Reduce Dusting When Discharging Bulk Bags

Unfortunately, Dusting is a Common Problem

While bulk bags can be the most economical package for shipping semi-bulk quantities of dry bulk solids, they often get a bad rap from end-users because the process of unloading them can be dusty.

Excessive dusting during discharge obviously causes a mess requiring additional clean up labor.  However, it can cause significant profit reduction because every pound of product that lands on the floor reduces ingredient yield and increases input costs.

Dusting Can Be Costly!

We know of a food manufacturer whose bulk bag discharging stations create a lot of dusting during unloading.  A plant visit confirmed the mess made during bulk bag discharging, but curiously their floors are always spotless!  

The plant has hose bibs EVERYWHERE, which encourages cleaning.  Seemingly a good thing.  

However, a thorough analysis of their ingredient yield showed that they were losing approximately $300,000.00 annually due to poor yield: TONS of product - along with a good chunk of profit - were being washed down the drain!

While it's true that not all of that waste was directly attributable to dusting from bulk bag dischargers, most of it was.

So, not only is dusting during bulk bag unloading a nuisance and housekeeping issue, it can quickly affect - negatively - the bottom line.

What can be done?

1. Training.  The biggest issue we see with the use of bulk bag dischargers is that operators are not following the manufacturer's operating instructions.  Regardless of the equipment used to unload bulk bags, if it is not used properly optimal dust containment cannot be achieved.  Left to their own devices operators will quickly figure out the easiest way to get product out of the bag - and that often leads to unecessary dust emissions.  Easy operation sounds like a good thing, but the reality of discharging bulk bags is that they require some effort to use properly.  Work with your bulk bag discharger vendor to fully understand how their equipment should be used to best effect and then train and supervise your operators accordingly.
2. Bulk bag design.  We often see situations where fine product sifts through the fabric of bulk bags.  If that sounds familiar your ingredient vendor should be willing to work with you to provide a bulk bag that eliminates this problem.  The easiest solution is to used coated bulk bags that feature a film of polypropylene bonded to the inner surface of the bag fabric.  This should cure most sifting problems.  However, if a coated bag isn't enough your vendor should be using a separate polyethylene liner.
3. Bulk Bag Discharging Equipment.  Bulk bag dischargers come in many configurations.  Some are better than others when it comes to dust containment.  Look for designs that allow easy  and safe access to the bag outlet spout while keeping it enclosed in a hopper that can be connected to a vacuum dust collection system.  However, not all of these designs are created equal!  If the hopper that is under negative pressure is filled with product during discharging, dusting will still be a problem when the hopper door is opened and product that has adhered to the inside of the door drops on the floor.  Ideally, the outlet spout of the bulk bag should protrude out of the hopper during discharge so the only time the hopper sees dust is during the initial stage of product flow and perhaps at the end of the discharge cycle.  Ergonomics are also a key criteria when selecting a bulk bag discharger.  As mentioned above, you don't want your operators circumventing Standard Operating Procedures and creating excessive dusting because the bulk bag discharger is too difficult to use properly.  Carefully evaluate dust containment features and ergonomic design when selecting a bulk bag discharger.

Bulk Bag Liners - When To Use Them... or Not! GUEST ARTICLE!

This article was written by Dan Schnaars, President of Ameriglobe LLC, one of North America's premier FIBC manufacturers.

When to Use Liners vs. Laminated Fabric vs. Fabric for your Bulk Bags

When you are in the process of designing your bulk bag packaging specifications, one of the key issues to consider is the kind of environmental protection the bag must provide to your product.

The best answer for you can sometimes be quite detailed.  Here we will consider the three basic types of protection.

Uncoated or Breathable Fabric Bulk Bags.

Bulk bags are made of woven polypropylene. While the weaving makes a fabric that appears quite solid, it is, in fact, breathable.  Air and ambient moisture pass quite easily through plain fabric.  Dusty products contained within can ‘dust' through the fabric and/or the seams of the bag.  For the majority of applications, breathable or plain fabric does not provide enough containment.  Any product contained in a breathable fabric bag will likely reach ambient humidity levels within a few days.

But, some products such as soy bean seeds or peanuts require a breathable container.  The airflow retards germination and mold and is, therefore, a necessary feature.  Many minerals travel in breathable fabric bags due to cost.  The mineral products often have a low cost per ton and the packaging cost is quite a significant factor in the final product cost.  Coating the fabric does add cost to any fabric.

Laminated (coated) Fabric Bulk Bags 

The most common method of environmental protection for your bulk bagged product is to use a bag that has a thin layer of film laminated to the inside of the bag.  This lamination eliminates most of the air flow through the bag. Most products travel well in this type of bulk bag.  Dusty products do not pass through the lamination and dust from the outside does not enter the bag through the weave.  Ambient humidity transfer is greatly limited by the lack of air flow as well.  If small amounts of sifting are not an issue and small amounts of contamination are not an issue, then this bag is most often the right choice.

Lined Bulk Bags

The need for extreme cleanliness, moisture control, or oxygen flow is what generally dictates the need for liners. 

Contamination Issue - Bulk bags are made from a manual sewing process. The fabric itself is often charged with static electricity that causes small pieces of sewing thread to cling to it.  Some companies are vacuuming the insides of the bag and working in clean environments, but this is only a reduction of the opportunity and amount of contamination.  Over the course of time, a loose thread or two will occur.

Sifting issue - In the sewing process, a needle punctures the fabric and carries a thread through the hole with it.  In order to do this the needle has to be bigger than the thread it leaves behind. Powders will often pass through this extra space.  To reduce this, bulk bag manufacturers offer to add ‘sift-proofing' materials to the seams.  Again, while this greatly reduces the amount of product that can sift through the seams, it can never be 100%.  If it were, then bulk bags made in this way would be able to hold water and not a single one can do this.

Only the proper use of a liner can ‘100% guarantee' that there will be NO contamination in your product.

Moisture control - If sifting cannot be prevented, then you can easily see why strong moisture control cannot be attained without a liner as well. The selection of the specific liner is just as important as the selection to have any liner at all. 

Most applications will use a 2 to 3 mil polyethylene liner.  This liner will work for almost all food applications, general moisture control, all sifting and contamination issues.

Specialized liners can be used when there is an absolute and special need.  For absolute moisture control, a liner with foil laminated to it can be used.  Liners with special gas transmission rates are selected when odors need to be contained or oxygen must be kept out.

Hazardous materials almost always require the use of a liner.

Liner attachments - The final piece to this discussion would be the connection between the liner and the bag itself.  Although many companies simply put the liner into the bag with no connection, this will often create problems for the end user during the discharge process. 

If the liner is unattached, it simply falls out with the product and becomes a contaminate in the receiving hopper.  Liners should be physically attached to the bag so that it will stay in the bag as the product leaves the bag.

There are three methods for attachment; sewing, tape tabbing and gluing.  Different products need different strengths of holding power. 

Some products like pellets will flow very easily from the bag.  It takes very little attachment support to hold the liner within the bag.  In this case, any of the attachment methods will work well. 

Other products tend to clump together such as powders.  These products can grab the liner more intensely.  It takes much more holding power to keep the liner attached to the bag. 

While opinions may vary, the method of attachment that involves the greatest number of square inches of the liner for its strength is a good gluing method.  Done well, this method can generate the most holding power possible for the most difficult applications.

Whatever your need, when you are designing a bulk bag package, involve your bulk bag supplier in the decisions.  They should be able to recommend the best product protection for your application.

-Dan Schnaars, President Ameriglobe LLC

How Big Is A Bulk Bag?

Bulk bags, FIBCs, bulk totes - call them what you will - are usually sized to contain one ton or metric ton of dry bulk solid material.

However, we've seen bulk bag payloads as small as a few hundred pounds and as big as 5,000 lb and more.  That being said, you may be surprised at how often we are asked the size of 'standard' bulk bags - as if there is only one size.

The fact that bulk solids have different bulk densities - usually expressed in pounds per cubic foot - means that for a bulk bag to contain a specific weight it has to be sized accordingly.  For a given weight, a bulk bag filled with a lower bulk density product will be bigger than one filled with a higher bulk density product.

That means that bulk bags end up being whatever size is required to contain the weight of product you want to package.  I.e. there is no 'standard' size!

Here's the basic procedure to size a bulk bag: 

1. Determine the method by which your bulk bags will be shipped: truck, rail, shipping container, etc.  This will determine the maximum width and depth of the bulk bag (and the pallet size if you're using them - you don't have to!).
2. Once the base dimensions have been determined calculate the bag volume required to hold the payload and then calculate the height using the known cross sectional area of the bag (base x width).

So, remember that there is no such thing as a 'standard' size bulk bag and that yours needs to be sized to your specific requirements.  Any reputable bulk bag vendor will be able to quickly determine the right size bag for your application - and then test it with your actual product to fine tune their calculations.