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.

Looking for ways to improve the sustainability of your bulk bags?

How about reducing their size?

How do you do that?

Do a better job of densifying your product so that it takes less volume for a given weight... and use a shorter bag!

Ideally, the product you put in your bulk bag should be at its maximum packed bulk density when it leaves your bulk bag filler.  If it's not you are using a larger bulk bag than necessary and, more importantly, it may not be safe.

Not all bulk bag fillers do the same job when it comes to compacting or densifying your product.

At Control and Metering we use a 'rule of thumb' that for every 10% you can reduce the height of your bulk bag, the cost reduces by 5%.

So if you can do a better job of densifying your product while it's being filled you're not only lowering your packaging costs you're also improving your packaging sustainability.

A VERY nice win-win!

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.

Before we discuss all of the considerations necessary to design a successful high-speed bulk bag filling line, let's first agree on what "high-speed" means!

If you are currently filling four bulk totes per hour, 10 bags per hour may seem to be high-speed.  After all, that's a 250% rate increase!

If you're filling 10 bags every hour, an automated bulk bag filling system that produces 15 - 20 FIBCs in the same time it takes you to fill 10 is a big deal.

However, at least for the purpose of this article, we're going to define high-speed bulk bag filling as producing 30 or more filled bulk bags per hour.

Yes, that's a lot, but it can be done consistently, with excellent weighing accuracy and such a rate can be achieved while producing stable - safe - bulk bags.

Sequence of Events

What happens when filling bags at a total rate of over 30 tons - 60,000 lb - per hour?  Well, exactly the same things happen as when filling 3 bags per hour, except they happen in a much shorter period of time.

Here is the timing chart for a bulk bag filling system designed to achieve a rate of 30 bags per hour:

Those are the same five tasks that are required to fill virtually any bulk bag at any rate.  However, as you can see and as we predicted above, the duration of each task is very short if we want to achieve a total cycle time of only 120 seconds!

High Speed Bulk Bag Filling - Critical System Considerations

Bulk Bag Design

The design of your bulk bag must support the overall system required to achieve a high speed bagging rate. 

For example, is the design of the loops compatible with the equipment such that they will be easily released and not hang up when the bag is automatically removed from the filling machine? 

Is the diameter of the inlet spout big enough to accommodate the filling machine fill head - that has been designed to achieve the instantaneous flow rate necessary to fill the bag in the required time?

Bulk Solid Handling System

The system that moves or conveys the dry bulk solid powder, flake, granules, pellets, etc. to the bulk bag filling system must be sized to maintain the gross throughput of the system.  In the case of 30 - one ton bags per hour, that is 60,000 lb per hour.

Instantaneous Bulk Solid Flow Rate

Ensuring that the bulk material handling system upstream of the bulk bag filler can maintain a continuous rate of 30 tons per hour does not necessarily guarantee that bulk bags can be filled to match that rate.

As can be seen in the timing chart above, over half of the cycle time is consumed by tasks unassociated with actually getting the bulk solid product into the bag.

In our example there is only 55 seconds allowed to deposit 2,000 lb of product into the bulk bag.  That means the required instantaneous bulk solid flow rate is roughly 130,000 lb per hour!

If the bulk bag filling machine performs weighing during this time, a 'dribble feed' task is required.  That means that part of the 55 seconds alloted to filling the bulk bag with product is used to dribble the last, say, 50 lb of product into the bulk bag to maximize weighing accuracy. 

Typically, for it to be effective, the dribble feed time is 10-15 seconds in duration.  That leaves only 40 seconds to fill 1,950 lb into the bag.  In that case the instantaneous fill rate is over 175,000 lb per hour!

Surge Capacity

As described in the above section, the bulk bag is actually being filled for only a portion of the total bag fill cycle time.  The rest of the time - called overhead time - is taken up by other tasks. 

During the overhead time bulk solid product cannot flow into the bag.  However, since our bulk material handling system continuously feeds 60,000 lb per hour to the bulk bag filling system, the product conveyed during the overhead time must be stored above the bulk bag filler. 

Typically, a surge hopper or storage vessel of some kind is used to hold the product conveyed to the bulk bag filler during the overhead time.  Calculations can be made to determine the vessel volume necessary to hold the product - commonly called surge capacity.

Bulk Bag Filling System

The bulk bag filling machine must be designed to accomplish the tasks in the time alloted - while maintaining acceptable weighing accuracy and producing stable and safe bulk bags.

Features such as automatic loop release, automatically movable loop attachments, automatic bag removal, etc. are required.

However, the most critical consideration is that because each task duration is so short, each aspect of the bulk bag filler's design must be optimized to not only operate quickly, but to perform its function properly in so short a time.  Weighing accuracy of +/- 1-2 lb and bags that have been filled to their maximum bulk density can be achieved when filling bulk bags in excess of 30 per hour.  However, specialized designs are required.

Filled Bulk Bag Takeaway

Removing one filled bulk bag every two minutes from the bulk bag filling system is no easy task.  Forklift traffic patterns must be considered as well as the round trip distance from the filling system to/from the warehouse storage point or loading dock.

Pushing The Envelope

Bulk bag filling rates in excess of 30 tons per hour can be achieved.  Filling machines that perform weighing can be made to fill up to 35 bags per hour.  Pre-weighing - weighing the product in a vessel above the filler and dropping the 'shot' into the bag as quickly as possible - can reduce the bulk bag filling cycle to the point where it is possible to produce over 40 bags per hour.

As can be seen there are many considerations that must be addressed when implementing a high speed bulk bag filling system.  Careful work conducted in partnership with the bulk bag and bulk bag equipment vendors is a must to ensure success.

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

Many producers of dry bulk solids, who have traditionally shipped their products in drums, boxes or rigid totes, want to take advantage of the financial benfits of converting to bulk bags. 

However, it is often difficult to convert every customer at once.  That means that for at least some period of time bulk bags and the legacy package(s) must be filled.

The problem is how do you handle having to fill multiple packages with multiple packaging machines? 

Changeover can be a significant challenge particularly if your current packaging machine is not portable.  Production scheduling and the time required to simply change from the existing packaging machine to the bulk bag filler can be barriers that prevent companies from benefiting from bulk bags.

What's the answer?

A multiple-package filling machine.  Purchasing a bulk bag filler that also fills drums or boxes or rigid totes - or ALL of these packages - is feasible and economically very attractive.

Filling multiple packages on one machine requires more up front capital as compared to a machine designed to fill only bulk bags.  However, the operational benefits of using a single machine that automatically changes its configuration to fill up to four different packages are significant.

Just think, no delays for changeovers AND you can satisfy those customers who have not yet converted to bulk bags.  A good deal I think.  Plus, there's the financial benefits that immediately hit your bottom line from converting to bulk bags... but that's another story! 

We often run across bulk bag users who subscribe to the idea that bulk totes MUST be inflated before filling.

Not true!

It's understandable why this common practice exists and why it persists: through-pallet densification FIBC fillers.

A through-pallet bulk bag filler is characterised by the bag resting on a pallet throughout the fill cycle.  As you can imagine, if a bulk bag is attached to the filler and left to drape randomly on the pallet prior to filling, it is possible - perhaps likely - that the bag will become twisted or folded on itself and not fill properly.  Hence, bags are often inflated prior to filling when a through-pallet filler is used.

While inflating a big bag is generally a good idea with this kind of bulk bag handling equipment, it takes time during the filling cycle and adds capital cost.  However, there is an alternative.

If you use a filler that features hang filling - the bag hangs from its loops for about half the time it is being filled - you don't have to inflate your bulk bags.

A key characteristic of this type of filler is that a pallet is NOT in the machine while it is filling bulk bags.  Because the bag is not in constant contact with a pallet and because the bag is hung from its loops, you don't have to worry about poor performance from not using inflation.

With a hang filling bulk bag loader the ONLY time you need to use inflation is if your bags contain loose tubular liners.

Stacking bulk bags CAN be done safely.  There are a few things to carefully consider before attempting to stack FIBCs, but if you do your homework and if testing conducted with your product and bulk bags proves they can be safely stacked, the increase in warehouse efficiency can be a remarkable financial benefit.

Here are the things to consider before attempting to stack bulk bags:

1. Is the nature of your product conducive to stacking?  Some dry bulk solids are easily fluidized and behave like a liquid, others densify like a brick.  Where does your product fit within this spectrum?
2. Are your bulk bags properly designed to facilitate stacking?  Unique bulk bag designs exist with features specifically aimed at aiding stacking stability such as stand up loops, strategically placed gussets, etc.  Do you need these features?
3. Is your filling equipment up to the task?  Does your filling equipment densify your product enough to produce a safe and stable FIBC capable of being stacked?

The best way to determine the answers to the above questions is to work with your big bag and filling equipment vendors.  They should be able to conduct tests that will prove that your product can be stacked safely in bulk bags.

Regarding benefits, double stacking doubles your storage space utilization.  Triple stacking improves warehouse efficiency by another third.  And, quadruple stacking - yes it can be done! - reduces your bulk bag storage footprint by a factor of four compared to not stacking at all.

As you can see stacking bulk bags can provide a huge improvement in warehouse efficiency and profit improvement.  If you're interested contact your bulk bag and equipment suppliers and get stacking!

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!