Until now, most shippers who use flexible intermediate bulk containers (FIBCs) have used them plain or with generic tube liners. That's beginning to change as people realize the benefits of form-fit liners. This article explores why form-fit liners have become a hot trend for semi-bulk shippers.
The advantage of a form-fit liner is implied by the name. The liners fit the bulk bag snugly so bags can hold more product. They make the bags easier to fill, handle, and discharge. That suggests why the form-fit liner market is growing 12-14% a year, faster than the FIBC market.
The disadvantage is price. Though prices have come down in recent years, form-fit liners still cost several times as much as tube liners. "It's a difficult sale," admits Michael Jones, territory manager of Smurfit-Stone, a reseller of bulk bags with liners.
The case for liners
Most shippers still use FIBCs without liners. That's fine for many dry flowable products, but problems can arise. A common one is contamination. No matter how tightly woven a bulk bag is, water, air, and odors can seep in. "What liners are historically used for is moisture control," says Fred Gonzalez, vice president of marketing and sales at Inter-Pak. Some products are so hygroscopic they can draw moisture from concrete. Even small amounts of moisture can ruin products such as high-purity chemicals or foodstuffs.
When a bulk bag is full, its seams stretch and allow further access. A bag may suffer nicks and scrapes in transit also. A fine particulate will flow like a liquid through any tiny holes.
A related problem with unlined bags is leakage. Substances such as carbon black can sift through a bag's microscopic gaps. The trouble is compounded if the product is environmentally harmful. Any leak of a hazardous chemical can trigger an investigation or fine from the authorities.
Because FIBCs carry a variety of substances-flour, sugar, seasonings, powders, mixes, resins, coatings, pharmaceuticals, vitamins, minerals, fertilizers-lining the bags is often a smart precaution. "The No. 1 reason for a liner is to protect the contents from the environment or the environment from the contents," says Ben Greene, director of sales and marketing at Grayling Industries, a leading manufacturer of bulk bag liners.
Liners typically are made of low-density polyethylene, which is inexpensive, lightweight, and moisture-resistant. Liners of special material exist for special situations. Antistatic polyethylene works well for fine-particle matter that clings to surfaces. Multiwall and laminate combinations using metalized polyester are good for extremely air- and moisture-sensitive products. Other liner materials include high-density and rubber-modified polyethylene, polypropylene, and nylon.
Liners also protect the FIBCs themselves. After shipping, the liners are discarded and recycled, but the bags can be reused. Often the economics argue against this-bags must be cleaned or sterilized, sometimes decontaminated, and returned to the source-but liners make it possible. Greene notes that a support industry has emerged to refurbish bulk bugs and return them to duty.
The tubular approach
The simplest way to line an FIBC is with a tube liner. These liners come in long, tubular rolls of polyethylene. A shipper draws the tube through a bag's fill and discharge spouts, cuts it off at each end, and attaches the ends to the spouts.
Tube liners are popular because they're cheap and easy. They have "no features and benefits," says Ken Ross, a senior sales representative at Grayling. The only question is, "What is their real cost?" But problems often occur with tube liners, especially in large-scale operations. Among them:
• The cylindrical tube doesn't conform to the rectangular FIBC's shape. Even when loaded, the tube's rounded volume doesn't fill the bag's corners or edges. Some bulk bag experts say as much as 20% of a bag's capacity is wasted. Because of the unused space, it takes more bags to convey the same amount of goods.
• As the product stretches the tube liner, it stresses the plastic. In the corners or wherever the FIBC doesn't support it, the liner is more likely to break.
• Filling a 50-inch bulk bag may require up to 150 of tubing. As the liner twists in the bag, it pleats and folds, trapping the product in its creases. This can lead to an uneven discharge flow, increasing the handling time. Moreover, material often remains caught in the folds. "It's a constant problem to get the product out," says one tube liner user. The only way to do it is to remove the tube liner and shake it out, a costly and time-consuming process.
• The tube liner's large surface exposes more of the product to the environment. Water, air, and other contaminants have more chance to permeate the liner or infiltrate through breaks.
• Since the tube liner is much wider than the 14 spouts, it gathers and bunches at either end. This can restrict the flow into and out of the FIBC severely. A slower fill or discharge rate elevates the handling costs.
• The ties or straps attaching the tube liner to the spout can come loose, particularly when discharge equipment tenses the liner. Without mooring, the liner may slip partially or totally out of the bag. An unattached liner may tangle in the equipment and halt it; the product may spill and become contaminated.
Fit as a fiddle
Form-fit liners solve these packaging problems. Made of the same materials as tube liners, they're custom-manufactured to fit FIBCs precisely. The form-fit liner's corners nestle in the bulk bag's corners, says Michael Jones of Smurfit-Stone, so "the product is allowed to flow to the corners, and even to the top of the bag." Even its fill and discharge spouts match the bag's spouts.
Because a form-fit liner fits snugly, there's no bunching or creasing. The FIBC's sides support the liner and reduce the stress on it. The liner's surface is less exposed, so less contamination occurs. The package is sturdier, so shippers can use taller bags or stack the bags higher.
Many bulk bag vendors insert form-fit liners loosely into their FIBCs, attaching them with tabs or loops. The liners' fitted shape is usually enough to keep them in place during discharge. It's simple to remove the liners for recycling and then reuse the bags.
Sometimes vendors sew the liners around the bags' upper perimeter. They may reinforce the sewn seams with polyethylene tape. Another technique is to glue the liners in place, securing them over a large area. Either method ensures liners won't slip, yet pulling them out remains easy.
Dollars and sense
What's the downside of form-fit liners? In a word, price. Because of their higher quality and customized construction, they cost more than tube liners. Many shippers aren't convinced that form-fit liners are worth the expense. For commodity products they may be right. But when a substance is more expensive, the form-fit liners' benefits may outweigh the costs. "With the use of a package like this," says one bulk bag vendor, "you can completely justify its price because it can hold more product and discharge dependably."
If a shipper fills two bags a day, the inefficiencies probably don't justify the form-fit liners' cost. But if the volume is 200 bags a day, the inefficiencies add up. A look at justifying form-fit liners:
• Better and faster handling. Fred Gonzalez of Inter-Pak says fill-time reductions of 30-35% are common. Finicky powdered products may load even quicker. One of Inter-Pak's customers cut its filling time 50-60%, adds Gonzalez-from 21/2 minutes to just under a minute.
In a production-line setting, where an empty bag immediately replaces each full bag, productivity can improve dramatically. "When you can start showing a customer some substantial reductions in his labor cost of filling a bag," says Gonzalez, "it makes it a little more palatable to spend a little more money."
• More filling. Jones has observed "anywhere from 15% to 20% more product" in bags with form-fit liners. He notes one client that wasn't getting enough of a new, "fluffier" kind of super-absorbent in its bags. The client switched to form-fit liners and the bags filled out perfectly, says Jones. "They worked like a charm."
Ken Ross of Grayling reports that customers who switch to form-fit liners sometimes find an extra 10 inches at the top of their FIBCs. They can use shorter, less-expensive bags and the cargo becomes more stable. Since they're packed solid, the bags don't "flop around" in transit or during handling.
•Less waste in shipping. The form-fit liners don't bunch or pleat, so little product is left inside. If the substance is expensive and "you're leaving five pounds' worth of material in the bag," says Ben Greene of Grayling, "it could easily pay for the liner." Again, the form-fit liners are also less prone to fail or permit contamination.
•Less waste in handling. Unlike tube liners, the form-fit liner's spouts fit the fill and discharge equipment exactly. A rubber bladder usually secures the form-fit liner's spout. Little product is lost during fill or discharge.
Jones notes a related advantage. "It's easier to seal the top of the bag." A form-fit liner can form an airtight seal against corrosive or volatile chemicals.
•Customization. While tube liners are all basically the same, form-fit liners can be custom-made for unusual bags or products. For instance, a customer may want a liner with moisture barriers on the sides but not on the top or bottom. Grayling can make liners with different films in different areas.
Into the new millennium
Like many businesses, form-fit liner companies face new challenges as they enter the 21st century. Among them are the economic slowdown and the globalization of markets.
One potential threat comes from overseas. With their low-cost labor, countries like Turkey, Indonesia, and China are mass-producing cheap bulk bags with or without liners. Domestic liner producers counter that foreign producers can't match the just-in-time delivery and customization available here.
Grayling normally sells its liners to FIBC manufacturers, who then resell lined bags to customers. The company is working to educate both end-users and FIBC companies about the form-fit liners' advantages. Because no one in the industry has much hard data, it's staging side-by-side comparisons to prove the productivity gains more than compensate for the cost.
Even with the price hurdle, shippers are finding the benefits compelling, which is why form-fit liners are outpacing the industry growth rate. "Everybody will admit the form-fit liner is a better product," concludes Grayling's Ross. The trick is showing it's better for the bottom line as well.