Bags with Valve… a small world of their own.

Bags with Valve or Valve Bags are closed at the top but have a side opening or spout that facilitates quick loading or filling utilizing hoses or special bagging machines. The valve itself incorporates a locking system that closes automatically without seams when the bag is filled.

It is common for Bags with valve to have side gussets to keep them better and more compact when they are stacked on pallets at their storage location.

Bags with Valve and non-valved bags come in various sizes, grammages, and colors, with micro-perforations, printing including bottom and sides, and multilayer construction, for example.

If the impression of the bag is not symmetrical, the valve can be placed on the right or left side of the bag, as required.

¿Paper Bags with Valve or PP Woven Bags?

The most common Bags with valves are paper bags and polyethylene (PE) valve bags, although woven polypropylene (PP) bags with valves are now widely used. There are aluminum bags with valves

Bags with valves
Paper made

Bags with valves
PP woven
Endurance Minor Major
Weight of the bag itself Major Minor
Up to 3 times less than paper
Overall resistance Minor Major
Resistance to the effect of
persistent humidity and sunshine
Minor Major
Production shrinkage Majors Minors
Affordable price Major Minor
Subject to plastic tax No Yes
Raw material availability Low for paper High for Polypropylene
Source of raw material Paper: Forests,
that should be regenerated.
Polypropylene: Petroleum,
that cannot be regenerated.

Types of valves

There are mainly two types of valves: internal and external.

  • Internal valve: The access valve to the bag is located on the side of the bag but does not protrude beyond the width of the bag. That is, it runs completely through the interior of the bag.
  • External valve: The loading valve protrudes to the width of the bag itself and, once loaded, is usually folded inward to increase the effectiveness of the seal.

Types of valve sealing

Several types of seals for valves must be selected according to the contents and the required degree of tightness.

  • Self-closing valve: The pressure of the contents occupying the entire interior of the bag causes the valve to close by itself. This sealing is enough in many cases but is the least watertight. It is not a suitable type of sealing for food products.
  • Ultrasonic Shutoff Valve: Shutoff that can be applied mainly on Polypropylene (PP) valves to make the inner product more watertight.
  • Heat Sealing Valves: Closing that heat seals the valve so the contents are completely closed and airtight. Polyethylene (PE) valves are usually used.

In some cases, a thumb notch can be included in the valve to facilitate handling and placement in the packing equipment.

The bottoms of the bags can be sewn or glued on a square bottom.

Benefits of Valve Bags

In addition to the speed of automatic loading of valve bags, there are other benefits to using this type of bag:

  • Less loss of material due to spillage in the load.
  • Less dust output from the loaded material.
  • Less percentage danger of contamination of the contents due to automatic loading from bagging machines.
  • The square tops and bottoms make the sides square, facilitating stable stacking of the bags.
  • There is no need for sealing operations, with the automatic sealing of some valves, saving time and closing machinery.

Markets and sectors that are particularly heavy users of valve bags

The markets or sectors where Valve Bags are most frequently used are, among others…

  • Cement, concrete and other construction materials
  • Chemical products
  • Resins, polymers and granular products
  • Agricultural products
  • Fertilizers
  • Salt and sugar
  • Animal feed
  • Seeds and spices
  • Nuts and dried fruits

Paper Bag
with external paper valve

PP Woven Bag
with external PE valve

Paper Bag
with internal paper valve