BUSRide Maintenance MAY-JUNE 2020 | Page 15

Figure 2. Luxfer’s hydrogen fuel delivery systems connect multiple compressed gas cylinders to a manifold system using various Swagelok fluid system components. Image © Swagelok Company fitting installation times are about three times faster now.” The inherent accuracy of creating consistent leak-tight connections using Swagelok tube fittings also improves efficiencies for Luxfer by reducing its inspection and testing times. To assemble a fitting connection, assemblers fully insert preswaged tubing into the fitting and then turn the fitting with a wrench a specified number of times. Followed properly, these assembly procedures result in leak-tight connections nearly every time, which means Luxfer’s fuel delivery systems pass inspection nearly every time. When using the O-ring face seal type fitting connections, inspectors often had to tighten various connections during testing – or rework some fittings altogether – to pass the inspections. Securing hydrogen service certifications Luxfer would not be able to achieve the efficiencies gained by using Swagelok tube fittings without the components meeting stringent regulatory standards for hydrogen fuel service, as dictated in the EC 79- 2009 EU H2 Regulation. When the two companies started to consider an alternative fitting technology, Swagelok had not yet applied for EC 79-2009 certification, which is required for any component that will handle compressed hydrogen with a nominal working pressure above 30 bar (435 psig). This includes the 350-bar (5,076-psig) systems Luxfer is currently making for the hydrogen-powered bus market and the higher-pressure 700-bar (10,152-psig) systems it is beginning to produce to meet new market demands. Swagelok’s tube fitting Figure 3.In Swagelok tube fittings, the two ferrules provide a hinging colleting action that securely design, which can accommodate grips the tube. The hardened back ferrule (light Luxfer’s 350-bar (5,076-psig) gray) provides direct and axial support to mitigate service, uses a twin-ferrule the effects of vibration and maintain a leak-tight design in which the hardened tube grip.. Image © Swagelok Company back ferrule provides the differential hardness needed to achieve a robust, leak-tight tube grip with excellent vibration resistance (Figure 3). During the course of tightening a fitting, the two ferrules provide a hinging colleting action that securely grips the tube, with the back ferrule providing direct and axial support to the tube gripping function. To enable use of these fittings in Luxfer’s systems, Swagelok went through the rigorous process of securing EC 79 certification – something hydrogen-powered vehicle manufacturers did not think would be possible. “It was a huge commitment for Swagelok to go through the costs of the EC 79 approval,” said Anderson. “While our customers thought that achieving the certification could not be done, Swagelok has actually done it.” Swagelok is taking a further step to enable the same leak-tight sealing performance of its tube fittings on the higher-pressure hydrogen systems Luxfer is developing. The move to 700-bar (10,152-psig) systems will require using Swagelok’s FK tube fitting technology, which features a reengineered twin-ferrule design that offers superior vibration resistance for higher pressure systems. The enhanced hinging colleting action of the FK fitting also prevents the fittings from backing off due to vehicle vibrations. Swagelok is investigating EC 79 certification for this fitting design to permit its use on Luxfer’s higher- pressure systems. Ensuring safety via training With hydrogen fuel systems housing flammable, high-pressure gas, there is no room for error in fuel delivery system fabrication. That is why Luxfer participates in a robust training program with Swagelok that includes instruction on tube fitting installation and system inspection. Swagelok’s full-day tube fitting training course gives Luxfer’s assemblers the knowledge to select and bend tubing correctly and install fittings properly, while keeping up with demand. Tube bending training is particularly important because hydrogen fuel delivery systems must be manufactured to very tight tolerances. Therefore, Luxfer’s assemblers need to know how to create repeatable tube bends so each subassembly fits precisely inside a vehicle on the production line. The fitting installation training is critical to ensure assemblers properly tighten fittings to enhance the safety of the fuel delivery systems. It includes hands-on instruction for tightening fittings by hand, as well as instruction on how to verify the installation using a gap inspection gauge. “All our operators go through the Swagelok installation course,” said Alex Millwald, bus systems production manager for Luxfer Gas Cylinders. “The training gives us the confidence that our assemblers have the knowledge and the competency to develop safe, reliable, leak- tight assemblies.” Luxfer’s fuel delivery system inspectors also attend an inspection training course that teaches attendees to identify common installation errors and faults and demonstrates the proper way to pressure test the systems. Using a testing panel Swagelok designed for Luxfer, inspectors perform functional tests at various pressures to monitor for leaks and system integrity. Inspectors use the same type of panel in their daily operations before shipping systems to customers. Fueling hydrogen-powered vehicle growth As hydrogen vehicle demand and use increases, safety, efficiency, and cost reductions will be consistent themes for the industry. The vehicles require reliable fuel storage, actuation, and delivery systems and components to ensure safety for operators, passengers, and anyone within close proximity of a vehicle. In addition, suppliers and manufacturers need to reduce costs by streamlining system and vehicle production, which may mean finding more economical alternative solutions like Swagelok’s tube fittings. “All our customers will ask for some kind of technical advantage or price saving if we make a request to change a part,” said Millwald. “With the Swagelok EC 79 certification and the tube fittings that we get from them now, we get both. It is a big win-win.” Gavin Pettifer is sales manager for Swagelok Company. He can be reached at [email protected]. BUSRIDE.COM | 15