A Pasted Valve Stepped End (“PVSE”) multi-wall paper bag, is a common industrial packaging style designed to package a wide variety of dry flowable products. Valve bags are packed on equipment that deposits material into the bag via horizontal filling spout. When the bag is discharged from the packing equipment, forces generated by the product inside the bag allow the valve opening to self-seal.
Measuring a Valve Bag
Bag Size:
A: Face Width is always listed first.
B: Finished Length is always listed second.
C: Top Width is always listed third. If the Top Width and Bottom Width are the same, this will be the last dimension in the specification.
D: Bottom Width may be listed fourth. This is less common.
Valve Size:
Valve size will be equal to or less than the Top or Bottom Width. If the valve size is less than the Top or Bottom Width, the valve is considered to be “Reduced”.
Sizing a Valve Bag
Step 1:
Establish desired product weight to be packaged in pounds or kilograms
Step 2:
Determine bulk density of product. If loose and packed densities are known, the bag should be sized for the loose bulk density.
Step 3:
Divide desired product weight by bulk density to determine bag volume required.
For example: Customer desires 50lbs of material to be packed in the bag and the bulk density of the material is 35lbs/cubic foot.
Bag Volume = 50/35 = 1.43 cubic feet
Step 4:
Based on the desired volume, identify appropriate bag size “starting” point (see chart). If the required volume lies between two figures, select the larger number.
Step 5:
Convert bag size based on desired/required dimensions
Size Conversion Formula:
- 1 inch of bag width = 2 inches bag length
- 1 inch of bag top width (thickness) = 2 inches bag length
- 1Width: 2Length: 1Thickness
Examples:
- 18” x 23” x 5” can convert to 17” x 25” x 5” (reduce width, increase length)
- 18” x 23” x 5” can convert to 19” x 23” x 4” (increase width, reduce thickness)
- 20” x 24” x 6” can convert to 18” x 26” x 7” (reduce width, increase length, increase thickness)
Step 6:
ALWAYS VERIFY ESTIMATED BAG SIZE BY FILLING SAMPLE BAGS
Contact our experienced team for all your technical bag questions. Whether you need an in-stock bag for immediate shipment or a custom designed solution, Southern Packaging is here to assist. Give us a call or email today!
Whenever we talk about paper we always include discussion of paper’s basis weight. But what is basis weight and what does it mean when selecting a bag? Merriam Webster defines basis weight as, “the weight in pounds of a 500-sheet ream of paper cut to a basic size.” So it’s accurate to say that basis weight refers to the thickness of the paper. The higher the basis weight, the thicker the paper is and, accordingly, the stronger the paper is. Bags with a higher basis weight can typically hold more than bags with a low basis weight. Basis weight is usually written with a pound sign (#) after the weight to indicate pounds; 40# means a paper has a 40 pound basis weight. Let’s look at some examples of basis weight in bags:
Merchandise bags: Our standard size merchandise bags have a basis weight of 30# to 35# for white, recycled natural, and colored paper, depending on the color and/or size. That means our merchandise bags are made from paper that weighs 30 to 35 pounds when cut to a standard size ream of 500 sheets. This is ideal for clothing, reading material, other retail merchandise, and even bakery, sandwich, and prepared foods.
Hardware Bags: Designed for holding much heavier items like screws, bolts, plant bulbs, and are even used as evidence bags by police departments. These bags have a much heavier basis weight of 50# to 58# depending on the size of the bag. This heavier weight of paper gives hardware bags the strength and durability to hold up to carrying bulky items that may tear through a lighter basis weight bag.
Shipping Bags: Our Eco-Shipper ® and Eco Natural shipping bags are designed to hold up to the rigor of postal or freight carrier transport. These recycled – and recyclable – shipping bags are made from 99# to 126# basis weight paper, depending on the bag size and color. Retailers across North America rely on these heavy duty mailers to safely transport their retail goods to their customers.
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