Home | About Us | Industries We Serve | Products | Quote Request | Contact Us



Fulton Companies
Flexible Intermediate Bulk Containers (FIBC)
Home Page



800-521-1414 sales@fultonpacific.com COPYRIGHT FULTON COMPANIES 2001-2004



site map




bulk food shipment containers Finally our high quality intermediate bulk containers are always manufactured in ISO 9000 facilities. Quality products at the best possible price set Fulton Pacific Company apart from the competition.
shipping liners
Material Strength Suppliers and consumers of polypropylene bags usually describe material by its areal density. Areal Density is the dry fabric weight. The most common unit of measure is ounces per square yard, often abbreviated as ounces. A fabric with a weight of 6.5 oz has an areal density of 6.5oz/sq. yd. InterBULK bulk bags are available in one of three weights: 6.0oz (1600D/14x14), 6.5oz (1700D/14x14) or 8.0oz (2100D/14x14) material. FIBC
Material Strength Suppliers and consumers of polypropylene bags usually describe material by its areal density. Areal Density is the dry fabric weight. The most common unit of measure is ounces per square yard, often abbreviated as ounces. A fabric with a weight of 6.5 oz has an areal density of 6.5oz/sq. yd. InterBULK bulk bags are available in one of three weights: 6.0oz (1600D/14x14), 6.5oz (1700D/14x14) or 8.0oz (2100D/14x14) material.
melon bins liners
SAND BAGS These bags are excellent as sand bags in flooded areas. They are extra-strong and last up to 1,200 hours in the sun without disintegrating. Bags are also used to package heavy parts and supplies. Attached tie-string included. Sand bags can be made of either burlap or woven polypropylene. These bags are puncture and tear resistant. USES » Package heavy parts and supplies » Emergency uses » Flood barriers LIMITATIONS » Sandbags will not seal out water » Several months of repeated wetting and drying will accelerate sand bag deterioration » Adding cement to the sand mix can increase effective life
feed shipping A Bulk Bag or FIBC (Flexible Intermediate Bulk Container) is a large woven bag designed to carry bulk materials. Bulk Bags range in size from 28" x 28" x 12" to 51" x 51" x 71", (filled dimensions) and may contain up to 4000lbs of material depending on design. They differ from RIBC’s (Rigid Intermediate Bulk Containers) by having flexible walls and tend to be for dry bulk solids. However, recent developments in bag liners and bag manufacturing have allowed the bulk bag to be used in other applications as well. sunflower seed IMPROVED SAFETY: The manual material handling of bulk material in bags and drums and the discharging of material into process equipment can expose workers to lifting injuries. Bulk Bags require less manual movement since they require a mechanical means (fork truck, pallet jack, or hoist ) to move the container and introduce it into the process. poly woven bags Tensile strength another term that is used to describe the strength of the material used to construct the intermediate bulk containers. Tensile strength is measured by pulling a 1.97 inch (5 cm) wide strip of cloth until it breaks. For example, a 1700D/14x14 weave has a tensile strength of 485 lbs/in2. fibc Bulk Bag Material Fulton Pacific Company bulk bags are made from extruded sheets of polypropylene film, which are cut into thin strips and wound onto bobbins. These strips are referred to as tapes. The tapes can vary in thickness and width, depending on the application of the material. The tapes are then woven into material that will be used to construct the various parts of the intermediate bulk containers. Because the polypropylene material used to make bulk bags is woven, the terms used to describe the material are identical to those used in the textile industry. polyethylene can make plastic bag Fulton Pacific Company is a supplier of Flexible Intermediate Bulk Containers (FIBC). FIBCs, also known as bulk bags are flexible woven polypropylene bags used for shipping, handling and storing dry-flowable and fluid products. apple bags bulk produce packaging feed shipping SAND BAGS These bags are excellent as sand bags in flooded areas. They are extra-strong and last up to 1,200 hours in the sun without disintegrating. Bags are also used to package heavy parts and supplies. Attached tie-string included. Sand bags can be made of either burlap or woven polypropylene. These bags are puncture and tear resistant. USES » Package heavy parts and supplies » Emergency uses » Flood barriers LIMITATIONS » Sandbags will not seal out water » Several months of repeated wetting and drying will accelerate sand bag deterioration » Adding cement to the sand mix can increase effective life
What does FIBC stand for? Flexible Intermediate Bulk Containers What are FIBCs? Also known as bulkbags, big bags or tote bags, FIBCs are woven polypropylene containers designed to hold large quantities of product, from 500kg up to 2000kg.

What are FIBCs made from? FIBCs are manufactured from woven polypropylene with a variety of different dimensions, filling, discharging and lifting facilities. How safe are FIBCs? At Bulkbag Limited, all FIBCs are regularly tested to destruction both in-house and at the National Engineering Laboratory. These tests conform to BS EN 1898:2001 and EFIBCA standards. FIBCs are issued with individual test certificates to the Safe Working Load and Safety Factor. What are the governing bodies for FIBC manufacturers? EFIBCA (European Flexible Intermediate Bulk Container Association) is a European Trade Association of manufacturers and distributors of FIBCs, who advise the technical and safety standards within the industry.

What is you company's policy on quality assurance? Quality is fundamental and Bulkbag Limited have an approved system of auditing performance, ensuring that the customer is supplied to specification. Our company was first registered to ISO 9002 IN 1989. Are FIBCs easy to handle? Very - FIBCs do not require specialised handling equipment. Most common handling apparatus includes standard forklift, pallet truck or crane.

Because they are fabric and not steel, are FIBCs easily damaged? Although polypropylene is one of the strongest man-made fabrics available, just like rigid bulk containers, FIBCs can be damaged if carelessly handled. It is important that your equipment is regularly checked. For example, forklift truck tines with rough edges may damage the FIBC. If handled correctly, FIBCs can be used successfully for many trips. Are FIBCs stable? Once the product has settled, FIBCs are very stable. Depending on the specific gravity/fill density of the product, it may be necessary to remove some of the air after filling before stacking the bags, particularly if the bag has an internal liner. It is recommended that the height does not exceed twice the width of the bag to assist stability.

Are FIBCs stackable? When filled with most products, FIBCs can be stacked in a warehouse 2 or 3 high. The stability and height of the stack is dependent on the product being transported, together with the handling equipment available. It may be preferable to stack 'pyramid' style depending on the stability of the product itself. What about second hand bags? We do not recommend the use of second hand bags. What about static build up? If static is a problem, as the sole UK licensees for CROHMIQ® Blue fabric, we can offer a concept big bag design manufactured from static-protective fabric which eliminates the need for earthing techniques. Alternatively we can offer traditional earthed bags.

What about leakage? For finer products and powders, we can offer our own brand of 'powderproof' bag which was first introduced to the market place in 1984.

What about more fluid products? For fluid products we can offer internal liners, which can be shaped to the bag itself and glued or tabbed if required. What about dense product, which does not discharge easily? We can offer a cone base, which will assist discharging or even full bottom opening bags.

What about re-using bags? This practice is perfectly acceptable in a closed loop facility where valeting and inspection are part of the process. Do you manufacture all your bags in the UK? We manufacture in the UK - and in addition have facilities in Eastern Europe and Asia, accredited ISO 9002.

ADVANTAGES OF FIBCs OVER OTHER FORMS OF PACKAGING INCLUDE:

Each FIBC can carry up to 1000 times its own weight. Each FIBC has integral lifting loops, eliminating the need for pallets. The woven polypropylene properties of FIBCs allow for the printing of product information to easily identify the product being transtported. Efficient use of space Simple to use Cost effective Very strong yet flexible Low unit cost Variety of dimensions available Variety of filling, discharging and lifting facilities Over 25 million FIBCs are sold in Europe every year to a wide range of industries including building and aggregates, chemical, pharmaceutical and food producers. Can be used for hazardous chemicals as specified in the UN Chapter 6.5 Recommendations. How dischargers work. Bulk bag discharges empty bulk bags easily and cleanly with minimum dust and maximum safety. First, a filled bag that is to be discharged is fitted with a rigging frame, which is a support frame placed over the top of the bag that engages the bag's lifting loops. Second, a forklift truck or hoist lifts the rigging frame and bag onto the discharger hopper, where the bag top continues to be supported by the rigging frame. The material bridge, or set, in the bag is broken as the bag is placed in the discharger hopper because the unsupported bag bottom sags.

Third, the operator unties the bag outlet (and liner, if used) through a door that provides safe access to the outlet. Fourth, the discharger starts to vibrate the bag to induce the flow of material out of the bag through the cone-shaped discharger hopper to a central outlet. A discharger for lined bags. Liners tend to slip out of the bag outlet during discharging. A liner tensioner and retracting system, which form part of the rigging frame, will prevent the liner from slipping out by pulling the liner over the liner tensioner's drum as the material discharges. The discharger's drop chute is also longer than the liner's outlet extension below the bag outlet spout to prevent the liner from entangling the transfer equipment or process below the discharger. A discharger for single-trip, flat-bottom bags. A discharger for single-trip, flat-bottom bags features a knife that slits the entire bag bottom. A side-of-bag diaphragm seals the bag bottom to contain the dust as the bag is slit. A discharger for hygiene bags. A discharger for hygiene bags features a violator knife that pierces only the liner – not the bag – at discharge. How to prevent contamination during discharging. If the bag has a bottom flap, fold the flap back while the bag is suspended and before it's placed over the discharger. Also remove frayed ends or nonsecured cords from the bag and liner so they don't flow into the process through the discharger.

How to prevent contamination during discharging. If the bag has a bottom flap, fold the flap back while the bag is suspended and before it's placed over the discharger. Also remove frayed ends or nonsecured cords from the bag and liner so they don't flow into the process through the discharger. Some factors to consider when selecting a discharger. Look at the following factors when selecting a discharger for your operation. Bag Loading. Because the bag must be lifted onto the discharger, ensure that the discharger's hoist or forklift can reach the bag. Also make sure that the rigging frame fits your bag size and supports the bag so that it doesn't collapse and restrict the flow. Operator access and safety. Choose a discharger that allows the operator easy access at chest or shoulder level so he or she can quickly untie the bag's outlet before discharging and quickly remove the bag after discharging. Also make sure your discharger doesn't require the operator to stand under a bag during either hoisting or discharging; standing to the side of the bag is safest. Dust containment. Choose a discharger that will capture dust created when the bag enters the discharger or is being discharged. For some applications, you may need a discharger that is equipped with dust-collection equipment, such as a side-of-bag diaphragm seal, exhaust ventilation at the door where the operator unties the bag outlet, and a liner sealing system. Outlet. Make sure the discharger's outlet is long enough to allow the bag to elongate as it empties, without letting the bag's outlet spout or liner entangle the feed or weighing system below. Alarm. Select a discharger with an alarm that signals when the bag is empty; this speeds the process of removing empty bags and loading filled bags onto the discharger.

Processing or feeding devices for your discharger. Many devices for processing or feeding discharged material fit under dischargers, such as vacuum systems, blowers, weighing devices, screw feeders, loss-in-weight feeders, and vibratory tray feeders. Select the device you need by considering the material being discharged, the process you'll use, and the feed method you require. Disposing of empty bulk bags Although a good discharger may leave as little as 2 to 3 ounces of material in a bag, some material will remain. This causes problems – particularly when handling powders – in collapsing bags for disposal or folding them for reuse. If possible, drop empty bags onto a pallet without collapsing them so they can be moved and easily handled elsewhere without adding dust to the work environment; folding empty bags where they're discharged not only creates dust, but requires a lot of floor space. Instead of folding empty single-trip bulk bags, compact them to save disposal costs, but use equipment that can extract dust. Fold multi-trip bags carefully, making sure that the outlet and inlet are open so air can escape without raising excessive dust. Conclusion

Bulk bags, also known as flexible intermediate storage containers, are inexpensive, safe containers that can be used to easily move and store from 500 to 8,000 pounds of bulk materials. Selecting a bag that's right for your application, filling it accurately, and discharging it completely will improve your operating efficiency. Part I of this article, the first of two, will help you select bags by introducing you to bulk bag design. Part II discusses how to fill, handle, discharge, and dispose of bulk bags.

Whether you're a material supplier or user, or a custom packager or shipper, you probably use bulk bags to safely and easily handle bulk materials and to improve your operating efficiency. However, to use bulk bags effectively, you should know how they're designed (Part I), as well as how they're filled, handled, discharged, and disposed of (Part II). Bulk bag design The most expensive part of your packaging system is the bulk bag itself, so selecting the right bag manufacturer and the right bag is important. Choosing a standard bag that's cheaper but doesn't fit your exact needs can raise labour costs, waste materials, and even cost you customers. To choose the right bag for your needs, consult a bag manufacturer and, together, consider several design factors: bag size, lifting loops, filling inlets, and discharge outlets; liners; and single-trip or multi-trip styles. Bag size. A bulk bag's size depends on the bag's base width in relation to the internal dimensions of the shipping carrier, the weight and filled density of the material the bag will hold, and the material's net filled height in the bag. A flexible intermediate bulk container (FIBC) is defined as an intermediate bulk container, having a body made of flexible fabric, which

Cannot be handled manually when filled Is intended for shipment of solid material in powder, flake, or granular form. Does not require further packaging Is designed to be lifted from the top by means of integral, permanently attached devices (lift loops or straps) Flexible intermediate bulk containers (FIBCs), also known as "big bags," "bulk bags," and "bulk sacks," were first manufactured in the late 1950s or early 1960s. There is some controversy as to where the first FIBCs were made; however, it is known that FIBCs were made in the United States, Europe, and Japan during the time period mentioned above. The first FIBCs were constructed with heavy-duty PVC-coated nylon or polyester where the cut sheets are welded together to form the FIBC. These FIBCs were made with integrated lift slings around the container, or attached to a specially made pallet, or a metal lifting device that the container sat on. The handling devices allowed the container to be filled from the top and discharged from the bottom. The initial cost of these heavy-duty PVC containers is high; therefore, they are designed to be reused many times in a closed-circuit system, where problems of control logistics, prevention of contamination, cleaning, and liability for loss or damage can be agreed on by the shipper and receiver of the product. Flexible intermediate bulk containers manufactured with polyolefin fabrics were experimented with in England, Japan, Canada, and the United States all at about the same time in the late 1960s to the early 1970s. It was the development of these high-strength light weight fabrics (i.e., polypropylene) that spurred the growth of the flexible intermediate bulk bags that are universally used today.

The rapid growth in Europe in the manufacturing of FIBCs occurred in the mid 1970s during the oil crisis. The oil-producing countries building program required large quantities of cement. The demand for cement was shipped in FIBCs at the rate of 30,000-50,000 metric tons per week from Northern Europe, Spain, and Italy to the Middle East. The demand for bulk bags in the United States grew slower than in Europe until 1984, when the U.S. Department of Transportation (DOT) agreed to grant exemptions for the shipment of hazardous products in FIBCs. Performance standards for FIBCs were established and issued by the Chemical Packaging Committee of the Packaging Institute, USA under T-4102-85. These standards were used to obtain exemptions until DOT included flexible containers with the other types of IBCs in the Title 49 CFR for hazardous products. The flexible bulk container offers features that are unique to this package. It can be folded flat and bailed for shipment to the user. The weight of a bulk bag used to ship one metric ton of product weighs 8-10 lb, offering a low package: product weight ratio. The cost of FIBCs is competitive with other forms of packaging as it is usually utilized without pallets. They are easy to store and handle in warehouses with standard equipment. When shipping by boat the FIBCs are gang-loaded with up to 14 bulk bags on a spreader bar, and are shipped as break bulk. The standard filled diameter of FIBCs is 45-48 in., designed to fit two across in a truck or a shipping container. Special configured containers are made to meet specific requirements of the container user. FIBCs generally are manufactured to meet specific requirements of the container users. The height of the container, the diameter and length of the spouts, coated or uncoated fabric, and whether a polypropylene liner is necessary will be specified according to the type of product that will be shipped.

When hazardous products are shipped in FIBCs, the UN mark for the product must be printed on the container body. In the United States the manufacturer or a third party lab may certify the container according to the regulations in Part 178 of the Title 49 CFR. All other countries require a third party lab to certify the container. FIBCs containing non-hazardous or non-regulated product when shipped export from the United States must have performance testing certification if destined for a country that requires performance standards for bulk bags. This material is used by permission of John Wiley & Sons, Inc. A. Brody and K. Marsh, "Flexible Intermediate Bulk Contains," Wiley Encyclopedia of Packaging Technology, 2nd Edition, Wiley-Interscience, New York, 1997, pp. 448-449. Copyright © 1997 John Wiley & Sons, Inc. To choose a bag that will fit into your carrier, you must consider the bag's base width. The base width of a bulk bag depends on the filled width of the bag, because the midsection of a bag with a square or rectangular top and bottom will round out. Measuring both the internal size of the carrier – such as a truck trailer or International Standards Organization (ISO) container – and the bag's filled width ensures that the bag will press fit into the carrier (most truck trailers have internal widths of 96 to 100 inches; ISO containers have internal widths of 92 inches).

To determine the base width for your bag when shipping bags side by side in a truck trailer or ISO container, use the formula: internal trailer width x 3.14 8x stretch factor To determine the rounded diameter or filled width of the bag, use the formula: (base length + base width) x 2 x stretch factor 3.14

The bag's stretch factor varies with the fabric weave's tightness, the fabric weight, and the material's filled density. For example, a bag with a 36-inch-square base and a stretch factor of 1.03 has a rounded diameter of about 47 inches. Before ordering your bags, make sure your bag manufacturer offers the bag base size you'll need to fit your carrier. The weight your bag must handle depends on your material's filled density and the weight you need to ship in each bag. The height of your bag may be limited by the headroom you or your end user need to discharge the filled bag. Safe storage practices also affect bag height: Bags taller than 60 inches shouldn't be stacked; bags taller than 48 inches shouldn't be stacked more than two high, even if they're on pallets. Bags shouldn't be taller than twice their base size, either. The material's filled height in the bag will vary, depending on the material's characteristics and the filling machine you use, so have your material tested on your filling machine before ordering your bags. Filling machines that densify the material during filling save bag height and make safer, more stable bags for stacking and handling. Table I lists various bag sizes – including empty and filled sizes and capacities – and bag styles for three standard base dimensions. Lifting loops, filling inlets, and discharge outlets. Selecting these components depends on your material, your equipment, and your hygiene requirements.

Lifting loops are usually located at the top four corners of the bag; they can also cross the corners. A bag's lifting loops must be strong enough to lift the bag when it's filled. Ten-inch loops are typical; 12-inch loops may be required if forklifts with fork tines will pick up the bags. Pop-up loops stand up to simplify inserting the fork tines into the loops, but are expensive. To avoid wear on all types of loops, smooth the sharp edges of the fork tines. The bag's filling inlet is tailored to fit the filling machine. A filling spout is the most common type of bag inlet and is used with a filling machine that feeds material through a tube or pipe. While 14-inch spout diameters are common with unlined bags, a lined bag's filling spout diameter can be increased to 20 to 25 inches if the filling machine spout is clamped only to the bag's liner. This larger diameter allows material to fill the shoulders of the bag without bridging in the bag's neck, which is especially important with powders. Bags with coned-top inlets accommodate cones formed by materials that don't flatten out at the top after filling, such as full-fat soya flour and some milk powders. A bag with a cone-top inlet can replace an oversized bag for a given weight of these materials as long as its lifting loops are extended and the filling spout's maximum diameter is used during filling. Bags with duffle-top inlets may also be used for this purpose. Both coned- and duffle-top inlets are uncommon. Bags with inlet spouts are filled by filling machines with twin-tube filling heads. Bags with open tops or duffle-top inlets are filled by other filling devices, such as front-end loaders.

The bag's discharge outlet should be large enough to discharge the material easily, which depends primarily on the discharger used. The most common type of outlet is an outlet spout. Outlet spout diameters can range from 10 to 25 inches. Typical outlet spouts are 14 inches in diameter and 18 inches long. The outlet spout must be long enough – at least 15 inches – to be tied off (usually by a drawstring) and, in most cases, goosenecked; if the outlet is too long, though, it can get caught in the discharger's feed system. Other bag outlets work with particular materials or dischargers that standard outlet spouts can't: hygiene outlets, super hygiene outlets, total-opening bag bottoms, and flat or plain bag bottoms. Bags with hygiene outlets have coated hygiene flaps that cover and protect that bag's base to protect it from dirty pallets or floors; these flaps can be pulled back before discharge. A sewn-in polyethylene membrane inside the bag or a full sealed liner covers a 15- to 18-inch-diameter hole, rather than an outlet spout, in the bag's base. Bags with super hygiene outlets are similar, but have either tailored polyethylene or tubular liners, allowing the liner to be clamped to the discharger before emptying. Hygiene bags require a special discharger and are used for foods, pharmaceuticals, and other materials that must be protected from contamination. Bags with total-opening bottoms, which open like bomber doors, can be discharged by releasing a holding cord. This type of outlet works with very low density materials, such as chopped straw or fiber, as well as with chicken manure and wood pulp, as long as the material in the bag weighs 1,500 pounds or less.

Bags with flat or plain bottoms discharge material when the entire bag bottom is cut manually or with a fixed-knife discharger; these outlets are obviously for single-trip bags. Because cutting the bag can leave shreds of bag fabric in the material, this outlet is best for materials like base minerals that can't be harmed by the shreds or for applications where the shreds can be screened out after discharge. Coating the bag base fabric will minimize shredding when the bottom is cut. A bag with a plain bottom must be slit open to discharge. A bag with a drawstring outlet is easy to untie and controls dust; a bag with a lined drawstring outlet may be used when the bagged material must be protected by a polyethylene liner. Liners. Liners protect the bagged material – primarily fine powders, foods, pharmaceuticals, and chemicals – from moisture and air. Liners are typically made of linear-blend polyethylene because it's stronger than low-density polyethylene and is less likely to crumb or shred if cut during discharge. It's also safe to use when filling with materials with temperatures below 80°F; high-temperature liners (safe to 120°F) must be used with materials over 85°F, but are more expensive. Linear-blend polyethylene liners are also rate moisture-proof, not waterproof, but will admit moisture over a long period. Liners are extruded in tubes and may be gusseted immediately or left ungusseted. (Using ungusseted liners is often more efficient than using gusseted liners: Pockets of material can collect in a gusseted liner's sealed gussets, and shaking this material out by hand and controlling the dust created is time-consuming). The extruded tube's circumference should equal the bag base's perimeter plus a 2 percent stretch factor. The liner's thickness can be from 2 to 8 mils, depending on the amount of protection the bagged material requires.

Single- or multi-trip styles. Sing-trip bags can be used once; multi-trip bags can be used several times. Almost any bag design can be either single- or multi-trip, as long as the bag isn't damaged during discharging, such as by cutting the bottom. The fabric and construction of single-trip bags should provide a safety factor of 5 to 1; for multi-trip bags, the safety factor should be at least 5 to 1. Whether you choose single- or multi-trip bags depends on several factors. Single-trip bags are cheaper on a cost-per-bag basis, though not necessarily on a cost-per-ton-moved basis. Lined bags with outlet spouts must be single-trip, because relining and retying off the outlet spout on multi-trip bags is too expensive. Single-trip bags are also more practical in many situations because returning multi-trip bags is time-consuming and costly – you must carefully handle and fold the bags before they're returned. Multi-trip bags have stronger fabric and loop material than single-trip bags. You can use multi-trip bags as often as 50 to 100 times if you carefully fill, handle, and discharge them. Multi-trip bags are best for in-house use (as long as bagged materials aren't cross-contaminated or such contamination doesn't matter) and for regularly shipping one material between one company's plants. However, to be cost-efficient, your multi-trip bags should have a return rate of 50 percent: on average, base your cost estimates on using the bags three times. The costs of returning and inspecting the bags and retying or resecuring their outlets – often underestimated – also make the bags expensive. Multi-trip bags that must be relined or that have discharge outlets that don't refasten easily raise operating costs, too. Finally, the further apart the filling and discharging locations for multi-trip bags are, the less efficient the bags will be.

Bulk bags, also known as flexible intermediate storage containers, easily, safely, and inexpensively move and store from 500 to 8,000 pounds of bulk materials. Selecting a bag that's right for your application and filling, handling discharging and disposing of it properly will make your operation more efficient. Part I of this article introduced bulk bag design. Part II discusses how to fill, handle, discharge, and dispose of bulk bags. Using bulk bags to safely and easily handle bulk materials can improve your operating efficiency. To use bulk bags effectively, you should know how they're designed (Part I), as well as how they're filled, handled, discharged, and disposed of (Part II). Filling bulk bags Properly filling bulk bags produces tightly packed, stable bags that are easier and cheaper to ship. The following paragraphs explain how a filling machine works, how it densifies bagged material, and how filled bags are removed from a filling machine. Some factors to consider when choosing a filling machine are also discussed. How a filling machine works. Empty bulk bags are hung by their lifting loops from hooks at the top of the filling machine. A filling device (such a screw conveyor) feeds material into the filling machine's surge hopper, which controls the flow through a flexible connection into the bag. The vibration table (which also supports the bag bottom and adjusts to different bag sizes) raises to support the bag bottom before filling starts. This causes material to flow into the sides of the bag bottom during filling and prevents the bag bottom from forming a rounded, unstable shape.

When the bag is about one-third full, the table begins to vibrate the bag and densify the material; this is repeated for several vibration/stretching cycles, depending on how densely packed the material must be (see the section Cyclical vibration and hang filling for more information). The vibration table lowers between cycles. When the bag is filled and densification is complete, the table lowers to disengage the bag. The self-releasing hooks then release the bag and a forklift truck or other device is used to remove the filled bag through the side of the filling machine's frame. The platform at the rear of the machine enables the operator to easily perform various functions (such as attaching the bag's lifting loops to the filling machine's bag hooks) at chest or shoulder level. How a filling machine densifies bagged material. A filling machine vibrates bagged material to densify the contents and remove entrained air, making the bag more compact and uniformly shaped, and thus, more stable. Materials with entrained air – particularly powders – that aren't compacted during or after filling make the bag unstable and dangerous and can raise handling costs. Improper filling, and improper handling after filling, can cause the bag to lean to one side or become banana-shaped, which can't be corrected once the bag is filled. To understand how densification works, it may help to consider first how the bulk density of a bagged material is defined, then how entrained air is removed from different materials, and finally, how a filling machine uses cyclical vibration and hang filling to densify bagged material.

Bulk density. A bagged material's bulk density can be untamped or tamped. Untamped bulk density is the density of a material sample collected during its free fall through the filling spout; at this point, the material includes entrained air. Tamped bulk density is the density of a material sample collected after it's been vibrated for several minutes and the entrained air has been removed. A bagged material's bulk density should be as near as possible to its tamped bulk density. Table I provides volume ratios of untamped to tamped bulk densities for several materials. Table 1 Volume ratios of untamped to tamped bulk density for several materials Material Tamped bulk density (lb/ft3) Untamped bulk Density (lb/ft3) Volume ratio Untamped/tamped (percent) Aluminum chips 15 7 47 Aluminum oxide 120 60 50 Ammonium nitrate 62 45 71 Baking soda 55 40 73 Barium sulfate 180 120 67 Portland cement 75 60 80 Wheat flour 40 33 83 Talc 60 50 83

Entrained air removal. Entrained air is removed from different materials at different rates, depending on particle shape and size. For example, removing entrained air from plate-shaped clay particles takes three or four times as much vibration as removing entrained air from round particles of similar size. Granular particles lose entrained air under their own weight, without vibration. Large granules reach tamped bulk density faster than small granules, although vibrating the bag as filling stops will make the bag even more stable. Cyclical vibration and hang filling. A filling machine can perform vibration and hang filling (or stretching) in continuous cycles to densify the material in the bag and ensure that the bag bottom is stable. In the vibration cycle, a coned-top vibration table engages the bag bottom; as the table vibrates, it forces material into the bag's corners and compacts it, while also deaerating and compacting the material throughout the bag. Because vibration works only on the weight of material above the vibration table, vibration usually starts when a minimum weight (about 400 pounds, or one-third of the bag's capacity) fills the bag. The vibration table moves down before bags are tied off and removed from the filling machine.

In the hang filling or stretching cycle, the coned-top vibration table moves down and causes the center column of material in the bag to collapse, flattening the material's surface. This ensures that the material in the bag corners is the most densely packed, so the filled bag will sit flat, not on a rounded bag bottom. During the final 10 percent of filling, the bag remains in the stretch cycle to ensure that the bag is accurately weighed to within 0.1 percent of the scale's capacity. Some bag types work better than others for hang filling. For instance, all woven polypropylene bags – the most common type of bag – stretch when hung. However, straight, compacted, unwrinkled polypropylene bags will remain more stable after hang filling. How bags are removed from a filling machine. A forklift or a motorized roller conveyor may be used to remove bags on pallets from a filling machine. Using a forklift involves the following steps (Fig. 3): Once the bag is filled, the filling machine's vibration table moves down and the operator detaches the bag inlet from the filling head. A forklift is used to move a pallet under the bag. The machine's bag hooks automatically release the bag's lifting loops as the bag is placed on the pallet, and the forklift removes both the bag and the pallet (Fig. 3b).

Using a motorized roller conveyor involves these steps: At the final filling stages, the vibration table still engages the bag; the movable conveyor section – carrying a pallet – is ready to move under the bag being filled. A previously filled bag waits on the conveyor next to the filling machine, ready to be removed. When the bag is filled, the vibration table moves down and movable conveyor section and pallet move into place below the bag. The operator detaches the bag inlet from the filing head, and a forklift removes the previously filled bag. The movable conveyor section raises until the newly filled bag rests on it and the lifting loops disengage. The bag then moves along the conveyor to wait for removal by the forklift. Some factors to consider when choosing a filling machine. When selecting a filling machine for your application, consider the following factors Strength. Choose a machine that's strongly built and will withstand damage from forklifts. Easy operator access. Make sure the machine has a platform or other support structure for the operator to stand on that is safe, protects the operator, and enables the operator to easily attach the lifting loops to the filling machine's bag hooks, engage the bag's inlet spout to the filling machine's spout, disengage the inlet spout after filling and tie off the inlet spout. Keep in mind that these duties are easiest to perform at chest or shoulder level. Bag bottom support. Choose a machine with a platform or table that supports the bottom of the bag as it's filled (a vibration table can service this purpose). This creates a stable bag by supporting the bag's bottom center when filling starts, forcing the material to flow into the sides of the bag near the bottom. This side material will then have the highest bulk density, so the bag will rest on its outside bottom edges instead of a rounded bottom center.

Bag height adjustment. While a filling machine is usually designed to fit one bag height and has fixed hooks to keep the bag's lifting loops vertical, bag heights can vary with different materials and different shipment weights. Thus, choose a filling machine that is big enough to accommodate the tallest bag the machine will fill, but will adjust to the shortest bag. Also ensure that operator duties can be performed for each bag size at chest or shoulder level. Liner attachment. Slip-seal (rather than clamp) liners onto the filling spout to prevent dust from escaping. Slip-sealing causes the liner to slip into the bag's inside dimensions, rather than stretch and weaken, as the liner is inflated and filled. Feed rate control and displaced air exhaust. Choose a filling machine that will control the feed so the material flows into the bag at the required rate. Make sure air displaced by the material is able to exit the bag. Bag filling rate. Choose a filling machine that can fill bags at the rate your application requires. Filling rates for most filling machines can range from 8 to 15 bags per hour, depending on how easily the operator can access the bag hooks and filling head and how many automated filling controls the machine uses. The rate also depends on the filling feeder's feed capacity, the required fill weight, the required fill accuracy, the ratio of untamped to tamped bulk density, and the time it takes two-thirds of the bag's contents to reach tamped bulk density. Bag filling rates are also affected by how easy it is to remove filled bags and what type of pallet- or skid-sheet-handling/removal system is used.

High-capacity filling machines can fill more than sixty 2,000-pound bulk bags per hour and typically include three filling stations mounted on a carousel below a hopper, which preweighs the material for each bag. Forklifts can be used to remove filled bags from high-capacity machines by inserting the forklift tines directly into the bag lifting loops; this eliminates the need for pallets or skid sheets. Controller. Choose a filling machine with a controller that allows the operator to perform all bag filling functions manually and that operates automatically once the filling starts. Also make sure the controller is compact – preferably microprocessor-based – and easily accessible. Suspension weighing. Use a filling machine with a suspended scale, because the scale will be isolated from vibration and make weighing more accurate. Handling filled bulk bags Proper handling will speed and simplify the transportation of filled bags, as well as protect the bagged material. The following paragraphs detail methods for transporting filled bags, restacking filled bags, and preventing contamination of bagged material. Transporting filled bags. Bulk bags can be shipped on pallets and skid sheets both over the road and by rail; bulk bags can also be shipped by sea. Each requires different bag handling methods.

Shipping bags on pallets. The easiest way to move bulk bags is on pallets, which can be lifted by forklifts. To efficiently load bags on pallets, follow these steps. First, use a pallet size that allows the rounded section of each bag to overlap the pallet edges, so the bags on adjacent pallets (rather than the pallets) touch each other. This not only minimizes the risk that pallets will damage the bags, but ensures that bags stacked on pallets will be more stable. Second, position each bag on the pallet's center. While the rectangular shape of most pallets can make centering difficult, most forklifts can either side-ship pallets or use other devices to precisely place loads. Third, use close-slatted pallets, which have top and bottom surfaces with tightly fitting slats; the small amount of space between slats will prevent bags from protruding through and being pinched and damaged either by the slats of other pallets when the pallets are stacked or by forklift tines during unloading. Using close-slatted pallets can also improve your load's stability, which will reduce bag damage, unloading time and work for the forklift driver.

However, close-slatted pallets are costly, so only use them in-house unless your customer will return the pallets. Instead, us nonreturnable pallets for stacked loads, or stack two bags on one pallet (as long as the filled bag height is under 42 inches). Though these methods are labor-intensive, they may still be cheaper than shipping close-slatted pallets. For nonstacking loads, use standard single-trip pallets, but be aware that forklift tines can damage the bags and poorly constructed pallets. Shipping bags on skid sheets. If you have equipment for handling skid sheets, you can use the sheets instead of pallets, but your loads won't be as stable. On skid sheets, stack bags only two high if they're filled to heights over 40 inches; don't stack bags filled to heights over 54 inches. If the filled heights of your bags exceed these heights, consider shipping the bags on racks. As with pallets, use a skid sheet size that allows filled bags to overlap the sheet's sides, so that the bags on adjacent sheets (rather than the sheets) touch. Center the bags on the sheets. Shipping bags by sea. Bulk bags are frequently used to ship minerals, chemicals, grains, and other dry solids by sea. Using bulk bags for sea shipment lowers shipping costs.