Filling and Closing Open Mouth and Pasted Valve Multi-Wall Paper Bags

February 17, 2021

Bag Packing Basics

image2-1Nearly any industrial material that’s powdered, flaked, or granular can be packed into a multi-wall paper bag. Specific methods used for packing bags include:

  • Gravity
  • Impeller
  • Air Pressure
  • Vacuum
  • Fluidized Bed
  • Vibration Feed
  • Auger
  • Belt

The physical and functional characteristics of the material being packed will determine the most effective method of packing as well as the type of multi-wall paper bag required. For example, dusty dense products like cement are typically packed with valve packers in pasted valve (PVSE) bags. The need to pack heavy cementitious material at high speed makes valve style equipment and packaging highly efficient. Contrast this with dusty light products like flour that are most commonly packed with open mouth packing equipment in pinch bottom open mouth (PBOM) or sewn open mouth (SOM) bags. Flour is also a contamination sensitive product. A PBOM bag offers the best sealing capabilities in the multi-wall paper bag family. 

Southern Packaging works with best-in-class bag packing equipment manufacturers including:


Open Mouth Bag Packers

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To package basic free flowing products such as animal feed, rice, seed, and fertilizer, a gross weight open mouth bagger under a control hopper would be considered. An operator places an empty bag on a conveyor that transitions to the filling mechanism. The bags mouth is presented manually or automatically on the fill spout and filled until it achieves the desired weight. The filled unclosed bag then transfers to a sewing head where it can be manually or automatically fed through the sewing head. Once the bag is closed it will transition to the pallet for shipping. 



PBOM, PSOS (Webb Pinch)

To package sensitive free flowing products such as food ingredients, hazardous chemicals, fine chemicals, and odor emitting materials an upgraded version of the open mouth bag may be employed. A pinch style sack provides for simple, complete sealing of the bag opening. Where a sewing machine requires operator manipulation and frequent adjustments, a pinch sealing unit is significantly less labor intensive and requires far less maintenance. A pinch sealer closes the bag by activating pre-applied glue on the bag’s opening with hot air, folding the open end over to complete the closure, and pinching the fold closed until the glue cures. The result is completely sealed package. Pinch style bags can be used on manual or fully automated equipment.


Pasted Valve Bag Packers


A valve bag is a common industrial packaging style designed to package a wide variety of dry flowable products including flakes, pellets, fine powders, and grains. Valve bags are packed on equipment that deposits material into the bag via horizontal filling spout. Product is pumped or forced into a small opening in the top corner of the bag by air pressure, impeller, vacuum, or auger. When the bag is discharged from the packing equipment, forces generated by the product inside the bag allow the valve opening to self-seal. Valve bags can be equipped with different valve or “sleeve” types. Each sleeve type performs the same basic function. However, the proper sleeve type for your product and packing equipment needs to be evaluated when designing a valve bag.

Valve packing equipment can be designed to gross weigh a product as it fills or have a net weight scale above the unit that drops a pre-weighed charge into the bag. Each type provides for accurate filling. There is a high degree of variability in valve bag packing equipment automation. The most basic setup can include hand presentation and removal of the bag from the fill spout. Fully automated lines can robotically place, discharge, and palletize bags with maximum speed, efficiency, and accuracy. 

Proper bag sizing is critical to proper valve bag function. A bag that is too loose or too tight will cause the bag to sift or eject material from the bag’s valve opening. Understanding product density and volume requirements allows a bag manufacturer to produce a high performing, functional bag.



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