H2Tech - Q1 2022 - 36

SPECIAL FOCUS ADVANCES IN HYDROGEN TECHNOLOGY
ance with local laws and regulations. In
Europe, for example, standard fittings
do not meet the stringent requirements
for H2
fixtures set out in Regulation EC
79. The higher the pressure, the higher a
component's performance must be. Fittings
and connections used in H2
fuel cell
components must handle both the high
pressures required for H2
storage and the
continuous vibrations created by a moving
vehicle. Some manufacturers have
addressed this challenge by developing
fittings with a twin ferrule design intended
to provide leak-tight performance despite
constant vibration and mitigate the
danger of components separating under
vibrational stress.
Avoiding leaks: Efficiency and safety.
Even the smallest H2
leak can cause
significant issues for both vehicle function
and safety. Twin ferrule compression
fittings (FIG. 3) have the lowest risk
of developing leaks when compared
with either traditional cone and thread
or O-ring face seal fittings-of the latter
two, one is connected manually (meaning
an increased chance of developing
leaks), and the other requires additional
specialized tools and multiple steps to
install (meaning a longer installation
time and more points at which an error
could occur). To install a twin ferrule
compression fitting, an assembler only
needs to pre-swage a nut, place the ferrules
onto the tubing, and tighten these
the back ferrule provides direct and axial
support to the tube gripping function.
This results in a more efficient installation
and provides leak-tight performance,
enhancing overall system safety
and saving on time and labor.
Application-specific components.
Different designs throughout the H2
fueling
ecosystem require different component
configurations. The H2
-powered
municipal bus fleets referenced earlier in
this article are an example-because the
buses have H2
storage tanks on their roofs,
Even the smallest
H2
leak can hinder a
vehicle's function and
safety. Twin ferrule
compression fittings
have the lowest risk
of developing leaks.
components by turning. The action of
the two ferrules securely grips the tube
as the compression fittings are tightened;
they require a more flexible construction
than typical long-haul vehicles. Reliable
hoses that can handle 350 bar (5,000 psi)
are therefore a better choice for bus applications
than rigid steel tubing.
As with the choice of what steel formulation
to use for tubes and fittings, not
all hoses are created equal. For example,
designers are advised not to choose polymer-core
hoses with metal overbraiding
since they will not stand up to the rigors
of this application.
Ongoing training. Since H2
fuel systems
contain hazardous, high-pressure
gas, training installers properly in fuel
delivery system assembly is crucial. They
must understand system inspection protocols,
as well as proper tube fitting installation
to prevent safety incidents.
Well-conducted training should emphasize
the following:
* Correct and efficient installation
of fittings
* Tube selection
* Tube bending (particularly
important, as the systems are
manufactured to tight tolerances)
* Tightening fittings by hand
* Verifying the installation using a
gap inspection gauge (FIG. 4).
It is recommended to take advantage
of comprehensive tube fitting training
courses provided by some manufacturers.
Likewise, fuel delivery system inspectors
should attend manufacturer-sponsored
training on how to pressure test a system
and how to identify common installation
errors and faults. Inspectors should perform
http://www.H2-Tech.com
H2Tech - Q1 2022

Table of Contents for the Digital Edition of H2Tech - Q1 2022
