BUSRide Maintenance MAY-JUNE 2020 | Page 14

Enhancing
hydrogen fuel delivery system
safety and efficiency
Tube-fi tting selection ensures
leak-tight performance,
streamlines system fabrication
With multiple tanks of high-pressure, fl ammable gas on board,
safety is the top priority for hydrogen-powered buses navigating
populated city streets. Safety must be engineered into the entire
vehicle – especially its fuel delivery system. Each system component
must be tested and rated to stringent standards, with vehicle
manufacturers relying on reputable suppliers to deliver consistently
safe, leak-free systems.
Hydrogen-powered vehicle manufacturers are also relying on
suppliers to help reduce the cost of vehicle production as demand
increases. They are pressing suppliers to enhance effi ciencies wherever
possible to drive down costs.
The team at Luxfer Gas Cylinders has been focused on meeting both
safety and effi ciency requirements for its alternative fuel (AF) vehicle
customers. The world’s largest manufacturer of high-pressure aluminum
and composite gas cylinders designs cylinders for the containment,
bulk storage, and transportation of compressed natural gas (CNG)
and hydrogen used in AF vehicles, such as transit and school buses.
In addition, the company fabricates complete AF delivery systems,
including the tubing, fi ttings, valves, and other components that move
fl uid from Luxfer’s cylinders to a vehicle’s engine or fuel cells.
Luxfer has been able to enhance the safety of its hydrogen fuel
delivery systems and the effi ciency of producing them based, in part,
on its choice of an integral component – a tube fi tting that ensures
leak-tight performance and streamlines system fabrication. Tube
fi ttings are among the most critical parts of a fuel delivery system,
as any leak of hydrogen could be catastrophic. In selecting tube
fi tting technology from global fl uid systems provider Swagelok,
Luxfer has been able to create repeatable, leak-tight connections that
are not prone to failure from vibration, corrosion, or other factors.
Surprisingly, that same fi tting selection has also nearly tripled Luxfer’s
fuel system assembly throughput.
Streamlining fuel system production
Various regulatory initiatives are driving growing market
demand for hydrogen-powered vehicles and infl uencing AF vehicle
manufacturers’ focus on effi ciencies and cost reductions. For example,
Europe’s JIVE (Joint Initiative for hydrogen Vehicles across Europe)
is encouraging mainstream adoption of hydrogen-powered buses
(Figure 1). The project will deploy nearly 300 hydrogen-powered
buses in 22 European cities by 2023.
14 | BUSRIDE.COM | MAY / JUNE 2020
JIVE also aims to reduce the cost of manufacturing hydrogen-
powered buses to make them cost competitive with CNG- and
diesel-powered buses – pressuring suppliers like Luxfer to be more
economical. The company had already reduced its cylinder production
costs by about 40% when it asked Swagelok to help reduce the cost of
fabricating the hydrogen fuel delivery systems.
Luxfer’s systems feature multiple fl uid system components that
connect compressed gas cylinders to a manifold system (Figure 2). The
manifold allows the vehicle to draw hydrogen from individual cylinders
to deliver gas to a fuel cell, which generates electrical energy to run
the vehicle’s engine. Within the system, Swagelok’s products include
tubing, tube fi ttings, and valves that control where the gas goes and
how it is used.
Figure 1. Europe’s JIVE (Joint Initiative for hydrogen Vehicles across Europe) project aims to reduce
the cost of manufacturing hydrogen-powered buses by 30% while also doubling Europe’s fl eet size
of the alternative energy buses in the near-term. Image © Swagelok Company
To enhance production effi ciencies, Swagelok recommended that
Luxfer switch from the O-ring face seal type tube fi tting technology it
was using to Swagelok’s tube fi tting technology. This change provided
signifi cant effi ciencies, including reduced installation times and the
near elimination of rework following testing.
Luxfer signifi cantly reduced its installation time by switching to
Swagelok tube fi ttings. The former O-ring face seal fi ttings required
assemblers to fl ange and fl are the ends of sections of tubing to enable
secure fi tting connections. The time-consuming process involves
additional tools and multiple steps, while introducing the potential
for missteps that may lead to future system leaks if not corrected.
In addition, installers must tighten the connections by torque. The
Swagelok tube fi ttings remove these issues, as assemblers only need
to preswage a nut and twin ferrules onto a section of tubing and then
tighten the fi tting by turns.
“The ease of tightening a Swagelok tube fi tting connection allows our
assemblers to make more connections and produce more systems per
shift, providing notable effi ciencies,” said Lewis Anderson, European
alternative fuel system manager for Luxfer Gas Cylinders. “Our overall