At the turn of the 20th century, the Valve Pouches was invented by salt salesman Adelmer M. Bates. The story goes that he sold more salt than the company could supply, and the bottling methods of the time seemed to limit his sales commissions. Once the bags were developed, Mr. Bates ventured into the development of equipment to fill his new bags. Since then, five basic machines have been developed to handle the various products filled into Valve Pouches:
- Air Packing Machines (also known as Force Flow)
- Spiral Packer
- gravity packer
- Wheel Packer (also known as Jet Stream)
- vacuum packaging machine
While many granular or granulated products can be effectively filled into valve pockets, the greatest use of valve pockets centers on powdered products or mixtures including powders. Since the opening of the Valve Pouches is much smaller than that of the open bag, the flow of powdered products can be better controlled.
The earliest advantage of Valve Pouches was that they closed themselves, reducing the labor required to fill and close (hand sewn) open bags at the time. Despite many innovations in valve design, including membrane locks and double traps, the self-closing function is a far cry from an airtight seal. Therefore, many bags used in the chemical and food industries are ultrasonically sealed after filling. Other advantages of Valve Pouches include tighter-filled bags and more square bags that typically stack better on pallets (compared to other bag formats such as open-mouth bags and form-fill-seal).
Mr. Bates’s original Valve Pouches were made of cloth. Today, the vast majority of valve bags are made of multiple layers of paper with an optional layer of polyethylene. Most are paper, although valve bags can be made from polyethylene or woven polypropylene.
Of the five device types above, four are frequently used. Gravity packers are rarely used because they are best suited for granular or granulated products, and these products are better filled with open or form fill seal equipment. There is a lot of overlap in the applications of these machines.
To help you choose, the pros and cons of the remaining four machine types are discussed below:
1. Air packing machine (Liliu)
Advantage:
- fast fill
- good accuracy
- Versatile – for fine powders and products up to 3/8” particle size
- There are no moving parts in the product flow
- Gentle product handling – no mechanical shear, minimal degradation
- Easy to clean up – bottom and chamber are accessible
Shortcoming:
- Adding air to the product during the filling process
- There is a risk of breaking the bag as the bag is filled under pressure
- Does not handle very light products well (<10 lbs per cubic foot)
- Does not handle “sticky” products well (e.g. baking mixes containing fat)
2. Spiral Packer
Advantage:
- A small amount of air is added to the product during filling
- Rarely will the bag break as the bag is not filled under pressure
- Minor adjustments – easy to understand mechanical filling method
- Versatile – can handle a wide variety of products – including difficult “sticky” products such as baking mixes containing fat
Shortcoming:
- Vigorous settling may be required to fill bags tightly
- Fluidized powder rushes past the auger even when the auger is stopped
- Usually slower than other fill methods
- Several ways to adjust the machine to the ideal settings for a variety of products
- Susceptible to wear – wearing parts in the product flow
- May cause mechanical shear and product degradation
3. Impeller Packer (Jet)
Advantage:
- Quickly fills most powders
- tightly packed bags
Shortcoming:
- Limited product range – 200 mesh and finer
- Difficult to clean (before product changeover)
- Susceptible to wear – wearing parts in the product flow
- May cause mechanical shear and product degradation
- Adding air to the product during the filling process
- There is a risk of breaking the bag as the bag is filled under pressure
- Some products may cause the impeller housing to heat up – may cause the product to burn
4. Vacuum packaging machine
Advantage:
- Can handle very light products well (< 10 lbs per cubic foot)
- Produces a tightly filled bag
- Gentle product handling – no mechanical shear, minimal degradation
- There are no moving parts in the product flow
- If the bag breaks during filling, the product is contained in a vacuum chamber – the environment remains clean
Shortcoming:
- Difficult to fill into bags with polyethylene barrier
- fill slowly
- Expensive compared to other filling methods
- Bags may burst during filling
Generally, air and screw packaging machines are used for food, chemicals, minerals and certain types of feed. The impeller packaging machine is mainly used for minerals, while the vacuum packaging machine is mainly used for chemicals. While it is wise to first consider the machines traditionally used for your product, you may also want to consider the unique advantages of a particular machine type. Most equipment manufacturers offer testing services to help you determine which machine is best for your product and your needs. Below is a basic chart that can be used to identify possible machines for your product.