April 15, 2013 - Charlotte, NC – Spiroflow Systems, Inc. announces the recent acquisition of the assets of Control & Metering of Mississauga, Ontario, Canada.  The company, known for their bulk material handling equipment, had filed for bankruptcy on March 20, 2013.  Spiroflow Systems acquired all company assets on April 12, 2013. 

Spiroflow Systems Chief Operating Officer Cary Moore, and Vice President of Sales & Marketing Mathias Lee concur, ‘We are excited about the ability to further solidify our position as the industry leading provider of material handling solutions with the addition of Control & Metering’s patented Bulk Bag Filling and Discharging technology.  This, coupled with an expanded presence in Canada will allow us to broaden our sales, engineering, manufacturing and services capabilities for our continually growing global customer base.’

Spiroflow Systems will open operations in the Toronto Area under the name ‘Control & Metering, A Spiroflow Company.’ Spiroflow hopes to retain key company personnel to ensure a seamless transition for both companies’ customers. 

For over 40 years, Spiroflow has designed, engineered and manufactured its industry leading line of material handling solutions.  A worldwide supplier of powder handling engineering and equipment, Spiroflow offers the industry’s most comprehensive line of mechanical conveying equipment with a wide range of standard and custom options for both small and large volume users.  Products include bulk bag dischargers and fillers, flexible screw, aero mechanical, tubular cable drag, tubular chain drag and pneumatic conveyors, box, sack and drum dump stations, and the ‘Pacepacker’ range of automatic packing, pick and place and robotic palletizing solutions. 

One of the most overlooked keys to bulk bag filling success is training.  This post reviews how properly trained operators facilitate a much more productive bulk bag filling operation.

Preparing the bulk bag for rigging.  

On the surface rigging an empty bulk bag to a piece of filling equipment appears simple indeed: attach the four loops and the inlet spout and that’s it.  

Of course, those are the basic tasks, but how an operator accomplishes these tasks determines whether it is a minutes long struggle or a 30 second or less fast task.  

Properly preparing the bulk bag to be rigged is the first, absolutely critical, step to minimizing bulk bag rigging time and hassle.

While a bulk bag is being filled the operator should prepare the next for rigging.  Preparation involves the following steps:

1. Unfold the bulk bag and expand it by stretching out the top corners.
2. Unfold the inlet spout.  Many operators find that folding over the lip of the inlet spout to form a collar makes it much easier to slide the spout over the fill head.
3. Place the bulk bag within easy reach of the rigging position.

Rigging the bulk bag.  

There is a simple and effective way to minimize motion and time when rigging a bulk bag.  

• When the bulk bag filler is ready for a bulk bag to be rigged, pick up the bulk bag with the aft loops on each side held in each hand. 
• Rig the aft loops first. 
• Then rig the front loops. 
• Only then should the inlet spout be slid over the bulk bag filler’s fill head. 

Rigging a bulk bag in this sequence guarantees that the operator does not have support the full weight of the bag and wrestle with it during rigging.  

Average operators can easily rig a bulk bag in 30 seconds or less following this procedure.

Using bulk bag filling equipment.  

Generally, bulk bag filling equipment is easy to use when initiating a filling cycle.  

However, in any operation things go wrong occasionally and operators who have been trained to properly suspend the filling operation in mid-bag and re-start the filling process after the problem has been solved minimize lost productivity.  

There are times when bulk bag filling must be aborted mid-bag (due to upstream problems or a host of other reasons).  Again, operators who know how to safely abort bulk bag filling and remove a partially filled bulk bag minimize down time.

Tying Off The Bulk Bag Inlet.  

Many bulk bag filling operations can instantly made more productive simply by tying off the inlet spout outside of the filler instead of within it.  

When a bag has been filled and is ready to be removed from the filler do not tie off the inlet spout before the bag is removed.  

Instead, remove the bulk bag, rig the next and start the filling cycle, then tie off the spout of the bag that was just removed from the filler.  

This applies to both automatic bag removal and forklift removal systems.  Immediately initiating the next fill cycle and then tying off the just-filled bag is always the most efficient method - even if the forklift operator has to wait for the filler operator to tie off the inlet.

Operators trained to accomplish these simple tasks will consistently perform to a higher level of productivity.  

As was pointed out in an earlier blog post "How Big is A Bulk Bag", there is no such thing as a 'standard' sized bulk bag.  The base or bottom seam dimensions are generally sized to fit within the mode of shipping to be used (shipping container, truck trailer, etc.) and/or to fit properly on the selected pallet.

Depending on the bulk density of the product and its characteristics, the bulk bag's height can be significantly affected by the bulk bag filling technology employed.  And, this can be a source of lucrative operating cost savings!

If your product's packed bulk density is around 35 lb/cu ft or less and its loose bulk density is more than 10-15% less than that, chances are reasonable that you are not able to achieve bulk bag weights of 2,000 to 2,205 lb using bulk bags sized to fit within a shipping container or a truck trailer.

If that's the case, maximum densification during filling can in most cases put more weight into the same sized bulk bag.

When that happens operating cost savings pile up quickly:

• Since you can put more weight in each bag, you can buy fewer bags.  A 10% increase in payload weight equals a 10% reduction in the number of bags you have to buy!
• Since you can put more weight in a container or trailer there are fewer shipments that must be made and each shipment carries more weight per container.  Once again, a 10% increase in payload weight reduces the number of containers thereby reducing shipping costs.  This can be a HUGE cost savings!

So, if you are unable to currently achieve one ton/tonne payload weights in your bulk bags investigate using bulk bag filling technology that will mazimize densification.  You may be able to put tens and even hundreds of thousands of dollars onto your plant's profit line by increasing the payload weight of your current sized bulk bags !

Learn about Control and Metering's cone table bulk bag filling technology that provides maximum densification.

There are a number of factors involved in successfully stacking bulk bags.  The one most overlooked is that your filled bulk bags must have a flat top!

Most dry bulk solids have an angle of repose.  If you pored a handfull of your product on a flat surface it would form a peak.  The angle of the peak with the horizontal varies depending on the properties of the product.

When product is poured into a bulk bag it forms a peak just the same as the example above.  However, if you plan to stack bulk bags it is critical that your bulk bag filling equipment densifies the product enough to produce a flat top.

A filled bulk bag with a flat top provides a stable platform on which to stack.  Without it, the odds of a leaning or falling stack are greatly increased.

If you are stacking bulk bags or plan to, safety is the first priority.  Make certain that your bulk bag filling equipment can produce a flat topped bag before you do anything else!

See how Control and Metering's cone table densifiction technology produces flat topped bulk bags!

Baffles are pieces of plastic fabric that are sewn vertically across each of the four corners of a bulk bag.  The fabric pieces have holes in them so that product can flow 'through' them and fill the corners of the bag.

You can see the vertical seams of the baffles in the photo at the left.

There are two reasons to use baffles:

1. Bulk Bag Stability.  If you suffer from unstable bulk bags, baffles can improve their stability and safety.
2. Bulk Bag Shape.  Baffles counteract the natural tendency of a bulk bag to 'round out' - a filled bulk bag will be almost circular in horizontal cross section at a point midway up its height. Sometimes this can cause problems when trying to maximize the load in a truck trailer or a shipping container.  Baffled bags are virtually square in cross section when they are filled.

Baffles are costly.  They can add as much $5 - $6 dollars per bag.  Therefore, their use should be carefully evaluated.

If you are considering baffles to improve bulk bag stability, compare the life cycle cost of using baffles at $5 per bag vs. the one time capital cost of filling equipment that can densify your product properly and produce a safe package with baffles.

Depending on how many bulk bags you fill per year, it doesn't take long for a properly designed bulk bag filler to pay for itself vs. having to spend $5 per bulk bag for the life of the production line.  

We got a call from a customer the other day who asked us to evaluate a chronic dusting problem that occurs when they fill bulk bags with their fine powder product.  Turned out that it was more a much more complex situation than it sounded like on the phone!

A site visit revealed the problems symptoms.  As soon as a bag started to fill dust begins to escape along the seams at the top of the bag where the top panel is sewn onto the sides of the bulk bag.  The product was 'sifting' through the top panel seams.

This being a very fine powder, the sifting caused a significant cleanliness issue.  However, the customer finally decided to tackle this long standing issue because of the problem's potential impact on the health of operators and it's impact on profitability - product falling on the floor was not being paid for by customers!

A quick review of the situation revealed several potential root causes of the problem:

• Faulty bag inflation.  The customer inflates every bag prior to filling.  Initial observation indicated that once product began to flow into the bag, it appeared that the bulk bag remained 'taut'.  Was the inflation system continuing to force air into the bag during filling?  If so, the excessive positive air pressure in the bag that would result from the inflation system continuing to run during filling could easily overcome any treatment of the top panel seams designed to prevent sifting.
• Inadequate dust extraction.  As a bulk bag is filled the air in the bag is displaced by the product flowing into the bag.  A means of removing this displaced air must be provided or excessive positive air pressure in the bag may occur during filling.  Per the above, this could lead to sifting through the bulk bag's sewn seams.
• Poor bulk bag construction.  In a situation where inflation and dust collection systems are operating properly, the cause of the sifting may be that the bulk bag is constructed with ineffective seam treatments that are designed to prevent sifting.

In this case the customer was interested in acquiring an 'area' type dust collection system to extract the product from around the top of the bulk bag.  In other words, they were looking at dealing with the symptom of the problem and not its root cause.

The solution they were contemplating is, in my experience, almost always ineffective.  Trying to blanket a relatively large area with a negative pressure source in hopes of vacuuming all of the fugitive dust particles either requires an enormous amount of air flow or simply does a poor job.  Further, any hope of reintroducing the collected product particles back into the packaging system so that it is not wasted is crushed because of the potential for sucking up contaminants along with the dust.

So, the proper process to deal with a situation like this is to carefully troubleshoot the system to determine the root cause.

In the article "High Speed Bulk Bag Filling - Preweighing", preweigh bulk bag filling systems, capable of achieving filling rates up to 40 bulk bags per hour, were described:

"Pre-weighing refers to weighing the payload of product to be placed in a bulk bag in a separate bin or hopper above the bulk bag filling machine.

Doing so eliminates the time required to precisely weigh the product as it flows into the bulk bag on the filling machine. Rather, the pre-weighed 'shot' can be dropped into the bulk bag as quickly as it can be made to flow through the pre-weigh hopper outlet."

In this article critical design considerations will be discussed.

Product Conveying Balance

A preweigh bulk bagging system capable of filling 40 bulk bag per hour must be 'fed' by the upstream production process and the system that conveys product to the bagging location, at the same rate - product in must equal product out.

This can be accomplished in two ways.

Often, the production line will continuously convey product to a large silo (50+ tons capacity).  The preweigh bulk bagging system is located underneath the silo and bulk bagging occurs either continuously, if production can keep up with the bulk bagging rate, or periodically when production has filled the silo to an appropriate level.

A less common arrangement is where the production line can continuously match the bagging rate and product is continuously conveyed to the bagging line where it is continuously filled into bulk bags.

Weighing

Designing the weighing sub-system is the most challenging aspect of implementing a preweigh bulk bagging system.

As was shown in the previous article, a 40 bag per hour system has a total cycle time of 90 seconds.  Of that, 15 seconds is allocated to emptying the preweigh hopper (the vessel wherein the product shot is weighed) into the bulk bag.  From the preweigh hopper's perspective, the remainder of the cycle time - 75 seconds - can be used to weigh the next shot.

Assuming a typical dribble feed duration of 15 seconds,  the fast fill portion of the weighing cycle is 60 seconds.

Typically, 50 - 100 lb of the total shot weight is dribble filled.  That means that, in the case of a 2,000 lb bag, 1,950 lb of product must be metered into the preweigh hopper in 60 seconds.  This equates to a very high instantaneous flow rate of approximately 117,000 lb/hr.

Two key factors must be considered to maintain accurate and consistent weighments:

1. Flow control.  The device used to meter the product into the preweigh hopper must be properly selected.
2. Flow rate.  The rate at which the product flows into the preweigh hopper must be consistent from bag to bag. 

There are a number of ways to design such a weighing system according to the desired weighing accuracy and capital budget.

Note that preweigh systems can be designed to consistently maintain accuracy of +/- 2 lb.

Bag Stability

The faster bulk bags are filled the less time is available for densification.  Further, bag stability becomes more of a concern as the bulk bag filling rate increases. 

Applications with bagging rates over 20 per hour must be carefully assessed to determine what amount of densification is required to produce safe and stable packages.

As the bagging rate approaches 25 bulk bags per hour and beyond, stability and densification become a major concern with almost any product - particularly if stacking the bulk bags is a requirement.

In a preweigh system capable of filling 40 bulk bags per hour, the filling machine must be carefully designed to ensure the filled bags are stable and safe.

In the next article we will look at when a preweigh bulk bagging system should be used.