Quick Links On This Page

Bag Filling Machine BasicsThe Importance of Pressure for Cement Bagging Machine PerformanceThe Fundamental Pillars of Smart Industrial BaggingIncrease Production without Upgrading Bagging Equipment

Bag Filling Machine Basics

Often customers come to us with a specific bag filling machine in mind, but after a few minutes of conversation with us about what they want to accomplish in their production line, a different bagging machine is recommended, often a less costly solution.

This post will describe the three basic types of industrial and agricultural baggers and link to other sources on the CBE website. This is a good place to start if you want to  become better informed about bagging.

The Valve Bag Filling Machine

Valve bags are frequently used for packaging powders, granules and blends of powder and granules. These bags are engineered to self-close after filling, so a separate sealing step is not required in the production line. Furthermore, because the bag opening is small and mostly contained during the filling process, dust is minimized.

An Air Packer in Operation

In video #1, a very typical valve bag filling machine, a CBE Model 730 air packer is being used to fill bags with a blend of barite and bentonite – a very fine powder measuring 200-300 mesh.

In this application a single operator places an empty bag onto the machine’s spout. The machine fills the bag to its proper weight. The bag closes automatically. The bag drops to the transfer conveyor.

The Model 730 uses high-volume, low-pressure forced air to propel the powder into the bag, which is why the generic term for the machine is “air packer”. An air packer is any valve bag filler that uses forced air to feed product into the bag.

Video #1

The Versatility of Valve Bag Fillers

Valve bag fillers can also be belt-fed, gravity impeller, or auger-fed, all depending on the size, weight and moisture content of the product being packaged.

Valve bag filling machines are very versatile. For example, the Model 730 shown in the video can fill bags ranging in weight from 20 – 110 pounds. The fill rate, depending on material, is 6-8 bags per minute.

An air packer can be integrated with an automated bag placer and palletizer for semi-automated or fully automated operation. Most units we sell, however, are for manual operations such as depicted in the video. An advantage of CBE machines is their simple operation. Literally, five minutes of instruction is all that is necessary to train an operator.

Palletizing Filled Bags

The packaging process isn’t complete, of course, until the bags are neatly arranged on a pallet for shipping. This is why we design production lines for our customers that improve productivity all the way down the line.

Notice in the video that filled bags are transferred through a bag flattening conveyor that removes air in the bag and shapes the bag for secure stacking.

After flattening, the transfer conveyor delivers the bag to the palletizing station where a worker (without bending over) simply lifts the bag into place on the pallet. Facilitating this is a pallet jack that automatically adjusts to the proper height.

A Bag Filling Machine for Open Mouth Bags

Some products and industries are not conducive to valve bags. If the material is too course, or won’t flow well enough, an open mouth bag is required. Some markets and customers traditionally prefer open mouth bags sealed by heat or sewing. In these situations you’ll need a different type of bag filling machine, an open mouth bag filler like the one featured in Video #2, the Model GWB (for Gross Weight Bagger) being used to package granulated zeolite.

Open mouth bag fillers require a second stage in the production line for sealing the bag. In the video a heat sealer is being used for the plastic bag. Alternatively, a sewing station can be used for sealing poly woven bags.

Notice in the video that although the packaging operation is very simple, open mouth bag filling requires slightly more attention from the operator than the valve bag filler in the first video. Still, operator training involves mere minutes.

Video #2

Open mouth bag fillers are frequently found in agricultural applications – packaging grain, feed, seed, and fertilizer. Granulated minerals or chemicals, such as the zeolite being packed in  video #2, are common applications, as well. Food products and landscaping products round out the possible applications for an open mouth bag filling machine.

The Model GWB fills up to six bags per minute. However other models offered by CBE can fill 20-110 pound bags at rates up 24 bags per minute. An open mouth bagger can be gravity-fed, gravity plus vibrator-fed, auger-fed or belt-fed.

For fast, easy filling of free-flowing, non-dusty powders, granules, and flakes, it’s hard to beat a CBE open mouth bag filler. But, what if you’re looking to transport and store up to 4,400 pounds of material in a single bag? What then?

The Bulk Bag Filling Machine

Bulk bags or “super sacks” are gaining in popularity as efficient methods of storing and transporting large volumes of material – chemicals, plastics, and minerals being the most common.

In Video #3 a CBE Model 530 bulk bag filler is paired with an automated pallet dispensing system for bagging 5-20 bags per hour of plastic resin.

Bulk bag filling looks simple but precise engineering is required to fill a bag quickly without wrinkling the bag or trapping air pockets inside. A properly designed bag filling machine and process ensures proper filling.

Video #3

Watch carefully in the video how the strap holders rotate making it faster for the operator to hang each bag. Also note that before product flows into the bag, the machine blows air into the bag to open it fully.

This high volume application required an automated pallet dispensing system which enables a single operator to fill up to 20 bags each hour.

For feeding product to the bag filling machine, one can choose belt-feed, auger-feed, rotary-vane feeder, gravity-feed, vibratory feed or air lock feeder.

Today, when manufacturers and distributors are looking at ways to reduce material handling costs, the bulk bag (super sack) is gaining in popularity.

Rest assured that one call to Choice Bagging Equipment will connect you with a bag filler specialist who will be able to recommend the best solution for your production requirements and budget. Request a call back here.

The Importance of Pressure for Cement Bagging Machine Performance

It’s not surprising that pressure is an important factor in bagging dry bulk powders; for a cement bagging machine or concrete bagging machine it is especially critical to speed and weight accuracy. This article explains how one customer significantly improved productivity and accuracy by following the fundamentals.

Our Model 730 Pressure Flow Air Packer is one of the most popular concrete and  cement bagging machines on the market today. We recently installed a pair of Model 730 Pressure Flow Air Packers to bag concrete and mortar mixes at a dry mix plant in Montreal, Canada.
Shortly after installation, the customer called to say that the weight accuracy was not within weight tolerance and also that the concrete bagging rate was much slower than expected. Additionally, the machine is designed to empty out completely at the end of a production run but for some reason he reported that when these machines would empty down to its last 2-3 bags of material, it would completely stop flowing out of the machines.
This was a problem because the customer made very small batches of product and had very frequent product grade changeovers that required opening and completely cleaning the interior of the machine between batches. This meant that nearly ever batch, the customer would have to open the chamber and dump 100-150 pounds of material creating waste and extra cleanup time. Our customer asked that I come to the plant to evaluate the machines and determine whether they had some kind of mechanical or electrical problem. The presumption was that there must be some sort of internal problems with the filling machines.

Mysteriously Slow

Upon arrival to the plant, it was quickly apparent that there was a problem. Although in that moment, bag weight accuracy was within specification, the bags were taking unusually long to fill. All of the mechanics of the machine and the controls were operating as designed, but product was taking too much time to load into the bag. Looking at the pressure gauge on the side of the pressure gauge on the side of the chamber, I noticed that it registered no pressure. So I began a diagnostic analysis of the chamber and its pressurizing system which consisted of the pressurizing chamber, the air pad and the blower control valve that regulating the inlet of high volume, low pressure air into the machine.

Looking for Obstructions

I looked for obstructions in the flow of air to the air pad the fluidized the material and also the disseminator that provided the pressurizing air to drive the air with force down and out of the machine. Neither had any obstructions but neither were flowing the amount of air needed to fill a bag properly.

Checking the Low Pressure Blowers

Then I asked to see the low pressure blowers that were supplied with the machines. Our blowers are specially designed to provide high volume, low pressure air to provide the pressurizing and fluidizing air required for the machines to operate properly. At this point, I learned that the blowers had not been installed. Instead the old set of blowers from the previous set of baggers that ours had replaced were left in place and used to feed air to our machines. I asked to see them.

The first thing I noticed is that they were exceptionally old and smaller than the blowers that we had provided. Additionally, the relief valves that prevented the old blowers from over-pressuring when not filling bags had been modified by someone at the plant to vent off half of the air that the blowers could generate before that air was even transferred over to our machines.

I asked what it would take to shut the line down to exchange the old blowers out for the new ones. This was not possible as the customer was in the middle of a campaign and this was there busy season. I told the customer that without knowing the exact condition of the old blowers there would be no way to assure that we could generate the volume of air and pressure required to achieve the results he was looking for.

Modified Relief Valves Restricting Air Flow

He asked me to see what I could do. I went back to look at the blowers. I noticed that the reason the relief valves had been modified was that they were worn out and someone had done their best to rig them to keep them going. Replacing them was the first order of business. I asked to see the pumps we had provided. I Compared the relief valves on our pumps to the relief valves on the old pumps. Fortunately, with some simple plumbing changes, our pressure relief valves able to be retrofitted to the old blowers. Once I replaced the reliefs, we were able hold steady pressure at 5 PSI although the volume was still much slower than optimal.

I then switched my attention to the Model 730’s. They were designed to divide the flow of incoming air from the low pressure blowers and direct the bulk of the air to the upper half of the pressurizing chamber to utilize as pressurizing air and the remainder down to the bottom of the machine to provide fluidizing air to lift and convey the material into the bag. Realizing that the old pumps were not capable of generating the volume of air required to both pressurize and fluidize simultaneously, I shut off completely the pressurizing air and directed the entire air flow to the air pad to fluidize the material. Although this solution had its own drawbacks, the machines were now capable of filling bags at a respectable pace and bag weight accuracy was improved.

Puzzling Weight Fluctuation

We began to run and check weigh all of the bags coming down the line to the bag palletizing system. We would see that the bag weights would begin good but then the weights would begin to drift after a period of time. At this point, I asked what the minimum level of product was required to be maintained above the machine for it to be allowed to run. I was told that there was no minimum standard. I then asked what type of level controls were in the bin to indicate to the operator how much material was in the bin at a given time. I was told there were level sensors in the bin but they were not visible to the machine operator and were only used to signal the blending system when there was room in the bin for the next batch of product.

Maintaining Head Pressure

I told the client that especially without the blower capable of generating pressurizing air to generate artificial head pressure in the filling machine, that maintaining product head pressure of product above the machine would be imperative to maintaining good filling speed and weight accuracy. Varying head pressure is very important as changing head pressure changes how the product flows and how the product flows (and at what rate and consistency) directly affects bag weight accuracy. I then trained the system operators to manually monitor the level of product in the supply bin and to stop filling bags when the level of product in the bin got low. This did not cause a production problem as the Model 730’s were capable of bagging much faster than the blending process was able to make new product.

With these changes in place and the customer now aware of how to compensate for the lack of air pressure and head pressure, the results improved dramatically. Bag fill times averaged 5 seconds per bag per spout on 30 KG (66 Lb) bags and weight tolerance averaged +/- .25-.5% depending on the grade of material packaged.

Paying attention to how to properly install and setup a cement bagging machine (or any other application) is critical. Installing a bagging machine is not simply a matter of sliding it under a supply bin and connecting it to utilities. It must be supplied with a good and consistent flow of material and especially if this is not possible, then assuring that the machine has good access to an adequate air supply is even more critical. And if these fundamentals are not fully understood, then it is advisable to seek the help and advice of someone who can help get the fundamentals right. Failing to pay attention to the details or work with someone who will can be costly and cause results to suffer.

The Fundamental Pillars of Smart Industrial Bagging

Regardless of which type of bag an operation uses – valve, open mouth or bulk bag – the ultimate goal of virtually every industrial bagging operation is to fill and seal as many bags as possible cleanly and accurately within a specified time period. Yet while the goal is simple, bagging dry bulk solids can often be tricky in implementation.

There are interrelated factors that must be in balance in order to ensure a successful operation. Three of these factors work together like the legs of a three-legged stool. If one is missing or not in balance with the others, the stool will not set right or possibly topple over. These three factors are:

  • Product
  • Bag
  • Machine

A Corollary Relationship

There is a direct and corollary relationship between these three aspects in every bagging application and the right combination can mean the difference between success or failure. The concept is simple; if one pillar is out of balance with the other two, the results of the entire installation will suffer. Furthermore, a small change to any one of them – the product, bag or machine – necessitates a change in one or sometimes both of the others.

The Cause of Many Problems

It’s very common to blame poor results on bagging machinery, but often times bagging equipment is not the largest problem. It’s just as likely that product characteristics have changed (or in some cases continuously change). Working in partnership with a competent bag supplier and machine manufacturer can help to steer clear of common pitfalls and avoid hazards that might otherwise produce in poor results.

An Example of a Powder Bagging Problem

As an example, consider a producer of a powdered material that decides to upgrade its packaging machines. The producer’s representatives search for and find a machine that has the combination of features they are looking for at a price they can afford. They conduct testing on the machine prior to purchase and all projections look excellent.

The new machine is installed and put into operation. At first glance, all appears well. But soon operators complain that the machine is spilling a large amount of product during the filling process or dusting excessively. Or perhaps the bag weights are out of specifications for weight tolerance. Any of these problems could be caused by the bagging machine itself. But they could just as easily be caused by a bag that is too small (one that fills to volume before it fills to weight) or the bag could be sized right and the bagging machine could be performing properly and the product is being over-aerated by upstream process equipment or somehow the product is being inconsistently fed to the filling machine. The point is that many times the cause and effect of problems within a bagging application might or might not be what they appear to be. There is a balance that must be achieved between bag, machine and product to make good results possible.

Pillar #1, The Product

The installation of any new industrial bagging equipment should begin with a thorough analysis of the product and its properties as well as a careful review of the environment that the machinery will be installed in. Crucial traits such as flow property, bulk density, moisture content, de-aeration characteristics, compaction properties are all important factors in choosing the correct machine for the application.

Additionally, the design and construction of the silo / supply bin and the product feed system should also be reviewed to ensure that the bagging machine is being supplied with material that is consistent and is not being subjected to influences of upstream equipment that will change the products density, flow characteristics and consistency.

Finally, sometimes product manufacturers will change the formulation of their products after their equipment has been operating for a period of time. When this happens, it’s important to test and analyze the new material mix to determine what the ideal bagging machine settings and bag characteristics should be to use with the new product formulation.

Pillar #2, The Bag

Although it does not seem difficult, choosing a bag that is engineered correctly for a given application is not as straight forward as it may appear. Frequently when a producer experiences poor results, the root cause of the problem is a bag that is not appropriately designed for that specific application.

This is not to say that the problem is the quality of the bag or the producer of the bag for that matter. For instance, a common problem we see on a regular basis is that bags are sized to fit the packed (non-aerated) bulk density of a given material while most times those same materials are fed into the bag at their loose (aerated) bulk density. In practical terms what this means is that when the product is moved mechanically or pneumatically, it is entrained with air and when that air is mixed with the material the bulk density is temporarily lowered.

The problem is that most people sell their products by weight, not volume. The dilemma they face is that if they sized their bags to fit the loose (aerated) bulk density of their material, the bag would look like a raisin when the product settled and returned to their non-aerated state. But to make matters worse, frequently they will use the bag and the bagging machine as a mechanism for compacting the material into as small a space as possible.

valve bag for industrial baggingOn the surface, it makes sense. A dense package looks better. It travels well and is less susceptible to load shifting during transit. And the more material that can be fit into a smaller space, the less it will cost to ship. Yet, the simple fact is that a bag that fills to volume before it reaches the target weight will produce a list of negative and unwanted side effects. The bag will be full but the bagging machine that is designed to fill by weight will continue to attempt to deliver material into a bag that has no more room to fit it. The result is product spillage and dusting and bag weights that are out of tolerance.

Perhaps the more critical of the two is the bag’s ability to release air pressure, and that depends largely on the materials used to fabricate the bag. Many factors must be considered here, including whether the bag is made with traditional paper, high performance paper, plastics or a combination. The weight of the material and the number of layers also need to be considered. The ability of a bag to release internal air pressure is greatly impacted by the inside mechanics of the bag, like whether there is a layer of polyethylene (PE), to what extent the PE is perforated or sliced, and where in the layer sequence the PE is inserted. The ability of the bag to release air pressure subsequently impacts filling speed and overall machine performance. For instance, in the case of an air packers which work by creating an imbalance of air pressure between high pressure (the pressurizing chamber) and low pressure (the bag), if the air pressure inside the bag equalizes with the pressure in the pressurizing chamber of the machine, the product will stop flowing or flow slowly.
The second factor, consistency in the quality of the bag’s construction, can impact the filling process in three ways. First, in automated applications, if bag tolerances vary from bag to bag due to loose manufacturing tolerances of the bag manufacturer, the machine might have issues consistently placing the bag on the spout for filling. This could also affect the way they stack in the magazine, which can lead to misfeeding in the system. Finally, if there are issues with the quality of the bag or inconsistency in characteristics like perforation, efficiency can be compromised due to poor de-aeration.

Sometimes a bag change may have nothing to do with a supplier, but is instead the result of a well-intentioned machine operator who sees an opportunity to save a penny or two per bag by making a change. Or perhaps the company’s purchasing department decides to switch to a bag with fewer layers.

Regardless of the reason, the company needs to step back and consider how the change will impact efficiency and make adjustments to the other two points of The Bagging Triangle to compensate.

Pillar #3, The Machine

The key to machine selection is to work with a manufacturer who understands the three pillars of bagging. A tell-tale sign of a manufacture that understands the relationship of these three elements within a packaging process is one that offers to test product bag and machine together in order to make competent equipment recommendations.

Test Samples of the Product on the Machine

Although there are some straight forward applications that do not require up front testing (like bagging corn or rice), the process typically starts with the machine manufacturer requesting a small product sample from the customer to analyze.

If the manufacturer’s initial analysis of the product matches with his understanding of the application, customer requirements and the customer’s available budget, it is then a best practice to have a larger sample of the material sent to the manufacturer so he can set up a simulated product run of the material under a load of the customer’s actual product tested on the customer’s actual bag.

Testing the product is a critical step that helps define the product characteristics, the bag’s filling behaviors and additionally to identify any previously unforeseen issues that were not considered in the original analysis of the application. From there the machine manufacturer can identify and define the proper filling technology to achieve the ideal productivity level. In addition, this testing helps determine optimal filling rates, how many spouts are needed to hit those rates, and what settings will need to be maintained on the machine to achieve them.

The initial setup is only the beginning. As a machine operator or company makes changes to the bag or the product, it is imperative that they evaluate the effect of those changes and adjust parameters on the machine to maintain balance. Before making the machine adjustments, it’s always wise to consult the manufacturer. Even well intentions changes can produce negative results if consideration is not given to how product and bag must also be altered to balance those changes.

In conclusion, it is the sum of product, bag and machine that creates the conditions for optimal efficiency, productivity, and profitability. Working in partnership with competent bag and equipment manufacturers to find the right combination of product, bag and machine is imperative to the success of the application and ensure that high quality results are achieved.

Increase Production without Upgrading Bagging Equipment

Is upgrading bagging equipment or adding new machines the only way to increase capacity? There have been improvements in technology that make filling machinery faster, cleaner and more weight accurate. But many times you might be costing yourself valuable production without being aware that you are doing it.

A Small, Simple Change for Boosting Production

There is a relatively small change that you can make that could quite possibly increase your production without any additional changes. Did you know that you might be able to increase how quickly your bags fill simply by increasing their interior capacity?

You can sometimes increase a bag’s length, width or height without noticeably changing the look of the bag or changing pallet dimensions.  This small thing can have an instant positive effect in decreasing bag fill times and sending your productivity and efficiencies higher.

Big Improvements without Upgrading Bagging Equipment

Sometimes a little can mean a lot. Although a tightly filled bag looks very appealing and stacks well, it can often be the cause of longer than necessary bag fill cycles. Especially when bagging aerate-able powders, the product will often fill the bag to volume before the bag reaches weight. Even though the bag appears full, the bag filling machine will continue to attempt to fill more product into it because it has not reached the correct weight. If this is the case, the bag fill cycle will begin at a rapid pace (in terms of Lbs or KGs filled per second) and then slow once the bag is filled to volume even though the machine’s mechanics (air flow, auger & impeller) or speed have not changed or slowed. It is a simple matter of not having more capacity to fit more product.  The only way for more product to fit into the bag is to either densify / settle it into the bag or wait for it to de-aerate so more product can fit in both of which take time. Additionally bag densification can increase the complexity of the machine and increase its cost. Increasing the bag’s interior capacity can be done at little to no cost (if the change is made when bags are re-ordered during normal course).