A Pasted Valve Stepped End (“PVSE” or “valve”) 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 a horizontal filling spout. Valve bags can be made from paper, polyethylene film, or woven polypropylene.
How is a valve bag filled?
Valve bags are filled through an opening located in the top corner of the bag. Product is pumped or forced into the bag via gravity, air pressure, impeller, 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. Common sleeve types include paper insert, poly lock, tuck-in, and sonic seal. 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.
What types of products can be filled into valve bags?
Valve bags are ideal for quickly and efficiently packing dry products that flow. The valve bag construction results in a squared-up bag, which palletizes very securely and can be printed with product information on the side or end panels for easier product identification in pallet loads.
There are 5 basic types of valve bag filling machines: Auger, Impeller, Air, Gravity, and Vacuum. Each type performs the same basic task of putting product into the bag. Bagging machines range in size, speed, output, and automation level.
Auger – Auger packers utilize a horizontal screw to convey product from a supply hopper through the fill spout and into the bag. The screw is powered by a drive shaft that turns the screw. This style packing system is ideal for cake-like powders, flakes, and granular products. In general, auger-style bag filling equipment packs bags slower than impeller or air packing equipment.
Impeller - Impeller packers use a multi-blade vertical or horizontal impeller to convey the product into a bag. Product flows by gravity from the supply hopper into the product feed inlet at the top of the machine. When a fill cycle is initiated, the impeller creates a positive draw on the product moving it through the feeder and into the bag. The impeller packer is designed for maximum efficiency by entraining less air, which results in faster filling rates and smaller-sized bags.
Air - Air Packers, sometimes called Forced Flow or Pneumatic Packers, are high-speed, gross weight baggers that blow fluidized material into valve bags. The Air Packer offers both excellent weight accuracy and simple operation. Air packers provide for high filling rates and minimal strain on a bag.
Gravity – Gravity packers utilize gravity alone to draw product from a supply hopper through a funnel and into the bag. This style of packing equipment is the most cost-effective but the least efficient. Most gravity packing equipment systems do not require a power source.
Vacuum – Vacuum packers use negative pressure to draw material into the valve bag. Bags are placed in a vacuum chamber where the product is effectively sucked into the bag. This style packing system is typically only used for light ultra-fine products such as carbon black, fumed silica, and graphite. Fill rates are fast and accurate, but the time to place bags into the chamber (“clamshell”) can be slow.
Valve Bag Filling Equipment Automation
Valve bagging equipment can range from labor-intensive manual setups to state-of-the-art fully automatic pack lines.
Manual – Operator places the bag on the fill spout by hand and pulls the filled bag off by hand. From there the filled bag is palletized.
Semi-Automated – Operator places the bag on the fill spout by hand. Machine discharges the filled bag onto a conveyor where the bag is palletized.
Fully Automated – Machine places the bag on the fill spout, machine discharges the filled bag onto a conveyor and the bags are palletized via robot.