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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.

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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.

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.

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 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.

Conceptually, reusing bulk bags is a good thing.  However,  you have be careful that the way YOU reuse bulk bags preserves the 'goodness'.

Let's explore what that means.

Bulk bags - or FIBCs, bulk totes, big bags, Super Sacks® - are an amazingly versatile and economical method of shipping semi-bulk quantities of dry bulk solids.

In every case, the economics of using bulk bags vs. small containers (50 lb bags, drums, etc.) and rigid bulk containers (corrugated boxes, metal or plastic bins, etc.) is advantageous.  The price per lb of shipped product is almost always lower and the financial return from using bulk bags is even further enhanced when handling labor, yield, warehousing efficiency and other factors are included.

Sounds like a winner, right?  Well, it is.

However, the picture can improve greatly if a bulk bag is reused.  Suddenly, the cost per lb of the packaging drops by half every time a bulk bag is reused.

Obviously, that is a financially compelling reason to reuse bulk bags... but it's gets even better!

Think green.  Even if you recycle your bulk bags (yes, it can be done!), reusing your bags has a tremendously beneficial impact on the energy footprint of the package.  Delaying the demise of the package stretches out its use so that the environmental impact of the packaging on a per lb basis is drastically decreased.  Another VERY good thing.

So, those are compelling reasons to reuse bulk bags, right?  Of course.  Then why might bulk bag reuse NOT be a good thing?

Safety.

Plain and simple: if you do not take great care to ensure that each reused bulk bag is safe before it is used again, you have created a potentially deadly time bomb.

Bulk bags, like ANY package, need to be inspected and, if necessary, repaired before reuse.  Skipping this step can result in problem bulk bags being directed back into production.  Frayed lifting loops, loose stiching, fabric tears, UV fabric damage and many other 'small' problems can result in the total failure of a bag posibly resulting in injury or death.

There exists a growing market for used bulk bags.  Brokers can easily be found who sell used bags.  While this is, on the surface, a useful service, you Must take GREAT care to confirm that the bags in question are safe.

For example, photos abound on the Internet showing used bags for sale that are shown bundled and sitting on loading docks or wharfs - outside in direct sunlight.  Woven fabric made from polypropylene tape degrades when it comes in contact with sunlight.  It takes some time to damage the fabric to the point where handling the bag within its safe load limit would cause failure, but it does happen and it is a very real concern.

That's just one way that a used bulk bag can be unsafe for use.  A thorough inspection by a knowledgeable person is required to confirm that a bulk bag can be safely reused.

So, while reusing bulk bags can be hugely beneficial, care must be taken to guarantee the safety of each reused package. 

The safest, easiest and least costly method of safely reusing bags is to insitute a closed loop system whereby the bags are returned to the producer who filled them - where they are inspected and repaired if required prior to being reused.  Often, a third party is involved who performs the inpection and repair service.

Interested in safely reusing bulk bags?  I suggest that you contact a FIBCA member who can advise you on how to implement a financially rewarding - and safe - bulk bag reuse program.

Super Sack is a registered trademark of B.A.G. Corp.

As a manufacturer of bulk bag handling equipment and a provider of bulk bag handling optimization services, we often challenge ourselves with what it is we need to do to meet all of our customer's expectations.

While it's easy for us to take an insular view of what it takes to design equipment with unique functionality, the 'game' is much larger than just that.

Bulk bag filling and bulk bag unloading equipment is perhaps only a small portion of what we provide our customers.  For example, analyzing their current situation, devising customized ways to solve nagging problems and uncovering operating cost saving opportunities that support an attractive ROI all contribute to creating a valuable customer experience.  Then, of course, there is how well we deliver on those promises.

We know that these are critical pieces of the puzzle that lead to Control and Metering - or any vendor - being seen by their customer's as a valuable partner.

However, it occurs to me that the only way to validate the exact set of 'partner criteria' is to actually ask those whom we serve what's important to them.

To that end you'll soon see Control and Metering reaching out to its customers to find out what we REALLY should be focussing on to enhance our ability to be a good partner.

Can't wait!