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The advantages of inflatable structures

October 26th, 2009 / By: / Structure Basics

Flexible and economical, air-supported structures fill multiple market niches.

When it comes to inflatable products, many people think of bouncy castles, parade floats or dancing tubes used for advertising. But the world of air-supported structures, or inflatables, extends far beyond the use of entertainment and advertising to industrial, military, architectural and aerospace applications.

Whether they’re used as a portable shelter or a payload landing on Mars, air-supported structures offer numerous benefits over traditionally built alternatives. “Typically, inflatables are a more elegant engineering solution because they are simple by design,” says Thad Fredrickson, manager of materials development for ILC Dover in Frederica, Del. “In addition, they require fewer mechanical parts, and they pack tightly and take up very little volume.”

Inflatables provide some eco-friendly benefits as well. “In today’s world when energy and its conservation are in the forefront of development, inflatables offer a low-energy production alternative to comparative products,” says David Abramowitch, managing director of 1300Inflate, a division of Giant Inflatables in Braeside, Victoria, Australia. “This advantage is growing by the use of recyclable fabrics, water-based coatings and low-energy fans and blowers.”

Expanding applications

Such advantages have prompted a host of manufacturers to explore possibilities in inflatable products. Abramowitch formed 1300Inflate, which produces air-supported structures for industrial and safety markets, after winning an IFAI Achievement Award in 2007 for a custom project. The massive, transparent, inflatable PVC wall his company crafted for Federation Square in Melbourne, Australia, served as an alternative to a brick-and-mortar construction, which the overhead structure could not support. The geodesic-style wall was designed to protect visitors from winter weather at the outdoor entertainment complex.

Soon after that project, Abramowitch contracted with a large, multinational company looking for help with inspecting its furnace that burns corrosive materials for the production of steam. The process often damages the insulation, which then falls as refractory debris from the furnace walls. The client had in mind a bouncy castle-style product to catch the falling pieces. 1300Inflate’s solution was FallStop®, a sturdy inflatable platform fitting within the furnace that is remotely deployed from outside the danger zone. In addition, the product doubles as a variable height inspection platform.

“We developed a composite material hybrid that included a base fabric of stainless steel woven mesh that was then made into a hybrid laminate,” says Abramowitch. The platform’s composition also includes a rugged PVC-coated nylon surface layer. “It’s a difficult skin to pierce,” he says, “and it can fold up tight to get in and out of the small access door.”

In addition to the safety platform, 1300Inflate focuses on three other types of inflatable products. One type of product involves those that create and modify space, such as buildings, shelters and booths that are self-supporting with a lightweight footprint. Common uses include portable workshops, soda-blasting booths, and triage or emergency-response shelters. Another is comprised of duct, tunnel and shaft closure, and isolation devices. A third type of product encompasses industrial operations, including molds and plugs for fiberglass and refractory requirements, towers for antenna-placement testing, observation platforms and lighter-than-air platforms. The most popular materials that 1300Inflate uses for envelope construction are PVC-coated nylons and polyesters; vinyl coatings offer weather protection, air retention, mildew resistance and easy cleaning.

In an emergency

The Patten Co., Lake Worth, Fla., has also pioneered inflatable products. Its founder, Fred Patten, developed and patented parachute rafts for World War II applications—the first of their kind used in war. The company has continued to develop life rafts and dive rescue boats that seat anywhere from one to 50 passengers. Patten’s product offerings, however, extend far beyond inflatable rafts. The company has also developed airtight shelters for mine safety, offering miners a safe zone for as much as 96 hours. The shelters, which are 5 feet high by 10 feet wide and 16 to 45 feet long, are inflated out of a steel box that continuously pumps breathable air into the chamber.

Another innovation from Patten is the Life Cube®, to be produced for a company called Inflatable World. The shelter, designed to serve as headquarters for disaster victims, is stored as a 50-inch cube and deploys in six minutes or fewer into a chamber that rises 10 feet and sits atop a 49-square-foot floor. Steve Patten, the company’s president, expects the Life Cube to enter the manufacturing stage in the near future. Working with a company called Air Cushions USA, Patten is manufacturing inflatable lifting bags for cars, semi-trailers and airplanes that are turned over or stuck in the mud.

Patten also makes an inflatable for Armor Screen®, a firm that installs hurricane structures on buildings. Patten has produced tubes measuring nearly 100 feet long and 12 inches in diameter that inflate on each corner of a building and attach to screens, creating a system that cuts wind velocity from 150 mph to 15 mph. “Many owners of condo buildings are saying it is better to buy this product than to replace all the windows in the building with impact-resistant glass,” Patten says.

For the majority of its products, the Patten Company uses nylons and polyesters featuring coatings made of vinyl, polyurethane and neoprene.

Out of this world

At ILC Dover, engineers have created a series of inflatable products for military and aerospace applications. For a recent project, the manufacturer crafted a radome (a weatherproof enclosure that protects a microwave or radar antenna), for the U.S. Department of Defense. The bubble housed a radar system used to continually look for long-range ballistic threats in American airspace. ILC Dover used Vectran® for the radome because “it is a strong material that can withstand hurricane-force winds,” says Fredrickson. The company also used Vectran for the airbag impact attenuation system that successfully landed the payloads for both the Pathfinder and MER Mars missions.

NASA has contracted with ILC Dover on a number of applications: a urethane-coated polyester shelter that could stand up to the harsh elements of Antarctica; airbags used in test ground landings of the Orion spacecraft to ease impact; and the Inflatable Re-entry Vehicle Experiment (IRVE), an aeroshell designed to demonstrate various aspects of inflatable technology as the structure re-enters the earth’s atmosphere. Both the Mars airbags and IRVE are coated with a silicone rubber.

Additionally, ILC Dover has manufactured helium-filled aerostats, used for surveillance, that rise up to 15,000 feet and are tethered by high strength textile cables that contain communication and power cables. The aerostats are being employed by the U.S. military in the war in Afghanistan. “This is a perfect application in the war theater because the sophisticated surveillance systems can see significant distances from that height,” Fredrickson notes.

What to consider

The fabrics, coatings and finishing of inflatable products all contribute to their successful operation. In terms of selecting materials, Abramowitch of 1300Inflate lists these important characteristics:

  • Tensile strength in both warp and weft of the fabric
  • Tear and rip resistance to reduce accidental damage
  • Coating adhesion to the fabric under all conditions of operation
  • Weathering resistance and the ability to easily clean, including resistance to UV degradation, abrasion resistance and retention of physical properties after long periods of exposure
  • Suitability of the material for joining techniques, which retain the full strength of the base material and integrity and properties of the coatings
  • Pliability and flexibility to prevent damage during packing, storage and handling, as well as ability to shape conform to applied pressures and forces
  • Fire-retardant properties and flame spread resistance to meet fire and safety codes
  • Translucence or opacity, along with insulating properties as the application require

Coatings, meanwhile, contribute to an inflatable’s pliability, weather resistance, durability and color/opacity.

Holding it together

A crucial step in the production process and in ensuring a product’s performance is the joint design. Most manufacturers use radio frequency (RF), applied–heat welding or cementing. Some products are also sewn, though Abramowitch believes that method will eventually fall out of favor.

Based in Fortville, Ind., Genesis Plastics Welding™ is a contract manufacturer that specializes in RF welding of thermoplastic products and components for companies in markets including medical, military, automotive, marine and consumer. The company employs its proprietary RF sealing technology, ecoGenesis, which allows welding of polyethylene, polypropylene and nearly any low-loss polymer in any combination of film, foam, woven fabric and nonwovens.

“The technology is ideal for the replacement of PVC and polyurethane with ‘green’ phthalate-free plastics, as it causes polymers with high dielectric loss factors to respond to RF welding just like PVC,” explains Tom Ryder, vice president of sales and marketing. “ecoGenesis also aids in cost reduction, as it eliminates the need for expensive heat-seal additives and enables the substitution of lower-cost raw materials.”

The technology’s eco-friendly approach is in line with what many manufacturers and fabricators seek today. “By manufacturing with phthalate-free plastics, companies can decrease their carbon footprint and promote healthier manufacturing practices,” Ryder notes. “This process also produces a consistently uniform, high-quality weld that facilitates cost reduction and enhances the long-term performance of our customers’ products.”

Growing bigger

As technology continues to evolve in the world of inflatables, so will the markets and opportunities. “The need for reliable, lightweight and compact shelters that can be rapidly loaded and deployed will be ever growing,” Abramowitch says. “Inflatable products are the only things that meet these requirements.” Ryder agrees with this market prediction. “For support, pressure, cushioning and space filling, inflatables are a great solution. With a world that is always looking for ways to reduce cost, what materials are less expensive than an air-filled inflatable?”

Holly O’Dell is a Minnesota-based freelance writer.

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