Advancements in valve bags have provided European mills and flour manufacturers with a competitive advantage that many U.S. dry bulk food manufacturers have yet to realize. In years past, manufacturers of dry bulk food products have shied away from valve bags, which were known for being messy and failing to provide reliable seals. As a result, open mouth bags gained in popularity, but in recent years, many European mills and flour manufacturers have overwhelmingly switched to valve bags. Despite the shift from open mouth bags to valve bags for packaging dry bulk food materials in Europe, few U.S. mills and flour manufacturers have followed suit.
The first valve bags were introduced in the mid-1920s, and throughout the years, valve bags have often had a slightly higher cost than traditional open mouth bags. However, the cost difference between open mouth bags and valve bags has practically disappeared. In fact, advancements in valve bags and valve bag packaging machine technology have created cost-savings for manufacturers in the form of decreased cleaning, more accurate filling and dosing, more secure seals, more efficient palletizing and storage, and increased packaging speeds.
Below is a closer look at the latest valve bag packaging advancements and their applications in dry bulk food packaging to help manufacturers stay up to speed on the latest developments.
Dust Prevention Advancements
Even though there are numerous state-of-the-art dust collection systems on the market, the best way to keep dry food packaging facilities clean is to control dust at its source. Much of the dust created in facilities is created when bags are transported to a sealer after being filled. For packaging machines that have only one sealer downstream, such as a single sewing machine, the time between when a bag is filled and when it is sealed creates an opportunity for product to escape the package.
An improved dust-free way to package dry bulk food products is to keep the bag at the spout and seal it while at the spout. With the small opening of valve bags, sealing at the spout is possible. Using a filling spout with an inflatable sleeve that seals the area around the bag opening, advanced valve bag packaging machines are capable of producing a hermetically sealed closure with dust-free filling. However, beware that some valve bag filling machines may appear to seal at the spout, but often the bag is removed from the spout and discharged, then it is sealed. This allows product to escape into the air before the bag is fully sealed.
In addition to sealing-at-the-spout capabilities, valve bag packaging machines are also available that reside in dust-proof enclosures, which provide secondary dust containment to increase plant cleanliness and reduce dust explosion zones. Valve bag packaging machines in dust-proof enclosures also prevent contaminants from entering packaging during filling.
Some of the earliest valve bags were self-sealing. Self-sealing bags are held closed by the force of the product in the bag, but they do not provide a food grade seal. Today, the most advanced sealing process for valve bags is ultrasonic sealing, which creates a hermetic seal that prevents the flow of air and moisture into a package.
Ultrasonic sealing uses high frequency sound waves that melt the plastic film bag material by vibrating the molecules to a point where heat is generated from the inside out. Even though ultrasonic sealing produces enough heat to seal a bag, it does not generate external heat like traditional heat sealers. In fact, the seal is cool to the touch immediately after sealing. Reducing the amount of external heat that is produced during sealing reduces facility cooling costs. Since the seal area is smaller than open mouth bags, an ultrasonic seal on a valve bag is also more consistent and secure than traditional seals used for open mouth bags, such as sewn seals. The process of sewing a bag creates holes in the packaging, which allows air and vermin to enter the bag. With ultrasonic sealing, no punctures have to be made in the bag to create a seal.
Palletizing and Storing Advancements
Valve bag machines with pneumatic, vertical impeller, horizontal impeller and auger filling options provide more control over the densification and deaeration of product, which ultimately impacts palletizing and storage. Valve bag filling produces increased product compaction by filling bags to maximum capacity. This complete filling of a bag creates a block-shaped bag that is easier to stack and store. Block-shaped bags are also less likely to shift during transport and they are also easier to move with robotic grippers. In contrast, open mouth bags result in more freeboarding (unfilled space in the bag), which creates bags of varying shapes that are more difficult to stack and transport.
Valve bag filling has a reputation for being slower than open mouth bag filling, but advancements have made valve bag filling faster than traditional open mouth bag filling for packaging dry bulk food materials. High capacity multi-spout valve bag filling machines are capable of producing more than 1,600 100-pound bags per hour and more than 2,000 50-pound bags per hour.
In addition, valve bag packaging machines with sealers at each spout minimize downtime. If a sealer needs maintenance on a multi-spout machine with only one sealer, production stops completely. Sealers at each spout allow production to continue even if one sealer is offline due to maintenance. Today’s valve bag packaging machines are also capable of filling bags of a wide range of sizes between 25 and 100 pounds, which reduces changeover times.