A huge bellows has been designed to prevent contamination of a high-purity environment where scientists are attempting to produce the conditions of high energy and density found at the center of the sun.

Usually protective bellows are used to keep contaminants away from hydraulic cylinder rods and other moveable precision components, but a huge bellows installed on the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) in Livermore, CA, has another mission. It has been designed to contain fumes and vapors that escape from a 60-foot-high telescoping hydraulic cylinder to prevent contamination of the high-purity environment required for NIF's 10-meter diameter Target Chamber.

The 360-in.-extended-height bellows with 72 in. ID presented several design challenges including limited space to accommodate its cross-section and restrictions on its retracted length. Below is a look at how and why this bellows is being put to work.

The large bellows used to contain contaminants at the NIF Target Chamber is readied for installation on the telescoping lift structure.

A Collaborative Project

Lawrence Livermore National Laboratory is operated by the University of California for the U.S. Department of Energy and National Nuclear Security Administration. The center was founded in 1952 as a second nuclear weapons design laboratory to promote innovation in the design of the nation's nuclear stockpile. It has become one of the world's premier scientific centers, where cutting-edge science and engineering in the interest of national security is used to break new ground in many areas including energy, biomedicine, and environmental science.

Large cable and hose carriers are visible on the sides of the 60-foot multi-stage lift mechanism to be enclosed by the bellows.

NIF is a nationwide collaboration between the government, national laboratories, and industry. The NIF project now being completed is a 192-beam, 1.8 MJ laser for creating conditions of extreme temperatures and pressures in the laboratory. It will use advanced laser and optics technologies for missions in national security, energy, and science research.

The unit's 192 laser beams will be fired at a tiny capsule containing the hydrogen isotopes deuterium and tritium, compressing it to a small fraction of its original size and heating it to 100 million degrees. Under these conditions, the fusion fuel will ignite and more energy will be produced than is delivered in the laser beams. The experiments will produce conditions of high energy and density similar to those found at the center of the sun and other stars.

The Nylatrac carriers fit inside the telescoping mechanism.

Part of the NIF project includes a large lift mechanism that is used to service the interior of the spherical aluminum Target Chamber where the laser beams are focused to the center of the chamber. The lift is used to remove a cover from the bottom entrance to the chamber and then is used to insert and hold a specially designed "cherry picker" machine with a manbasket. The inside surface of the Target Chamber is covered with thin stainless steel removable panels. The special man lift enables technicians to reach all internal surfaces of the Target Chamber for maintenance. The lift also will be used to insert other materials into the chamber during maintenance cycles. (High levels of cleanliness are required to achieve the necessary 10-6 Torr vacuum required during NIF laser shots.)

Apex Design Technology Inc., an engineering-based manufacturer that provides tooling and fabrication services as well as design and test capabilities for hydraulic, pneumatic, and electronic systems, was selected to design and build the complex lift mechanism.

Keeping Contaminants In Check

Central to the lift mechanism is a hydraulic cylinder and related structure that provides approximately 52 feet of vertical travel. To meet the extended travel requirements while requiring as little space as possible for the retracted cylinder, Apex used a telescoping cylinder. Because equipment connected to the Target Chamber is very sensitive to petroleum-based vapors, though, a bellows was needed to enclose the lift.

The entire device was designed to nest into a pit when retracted, which limited the space available for the bellows, both in cross-section and height when collapsed. "One challenge was the constraint on size in the envelope from the cylinder to the bellows," says Todd M. Gallagher, vice president of Apex. "It's a very tight tolerance, and the same applies from the exterior of the bellows to the framework."

The bellows was designed by A & A Manufacturing Co. Inc., a specialist in the design and manufacture of bellows, boots, way covers, and other protective components for all types of machinery. It was fabricated from elastomer-coated fabric materials and made in 14 separate groups of convolutions that were joined to make the final bellows. The rings that form the convolutions were made from partial segments because of their size, and all convolutions were joined by external tie strips to ensure uniform expansion and weight distribution. At the top, the strips were clamped to a conical collar that mounts to the lift mechanism.

A & A Manufacturing also furnished two large Nylatrac NXL Series cable and hose carriers to maintain the proper bend radius and protection of the electrical cables that traverse through the lift. These non-metallic, link-type carriers are non-conductive and suitable for the long travel required.

More information is available by contacting A & A Manufacturing Co. Inc., 2300 S. Calhoun Rd., New Berlin, WI 53151, calling (262) 786-1500, writing in 40 on our reader service card, visiting www.gortite.com, or replying online at www.pddnet.com.

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