Plumbing Connection Summer 2017

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7 8 PLUMBING CONNECTION Summer 2017
Some of the technical challenges that need to be considered
include the impact on infrastructure including distribution
pipelines. Old steel mains at high pressure are incompatible
for transporting hydrogen as embrittlement of the steel can
occur. In addition the smaller hydrogen (H2) molecule relative
to the methane (CH4) in natural gas increases the probability
of gas leaks occurring. The use of polyethylene pipelines
addresses these problems.
The impact on infrastructure downstream of household
billing meters also needs to be considered. Copper and its
alloys such as brass are believed not to be impacted upon.
However the effect on older downstream infrastructure made
of steel may need to be considered.
Hydrogen has a significantly larger (4-75%) flammability
range than natural gas (5-15%) and as mentioned earlier is
more prone to leakage given its smaller molecule relative to
natural gas. Hydrogen also has a higher flame speed which
means it is more likely to ignite back at the injector of a burner
(commonly referred to as lightback) if the appliance is not
designed correctly or if the appliance is not converted to suit.
Type A gas appliances designed for use with natural gas
are laboratory tested using a range of natural gas limit
gases prior to certification. “Nb” gas is a natural gas limit
gas which contains approximately 13% hydrogen. Hence
this limitation will have to be taken into consideration when
considering the concentration of hydrogen to include in the
blend. It is expected that a safety margin would be considered
and so therefore the concentration of hydrogen within the
natural gas would be considerably less than 13% to ensure
satisfactory performance of installed Type A gas appliances.
Hence theoretically there should be no need to make any
adjustments to the appliances provided the concentration of
hydrogen in the natural gas is less than 13%.
Injecting higher concentrations of hydrogen beyond 13%
would require for gas appliances to be modified or converted
in order to cope with the characteristics of hydrogen. This
would typically include a change in the burner head design
where burner ports are reduced in size to prevent lightback
and also a reduction in primary burner aeration and reduction
in operating pressure. An increase in the size of burner
injector orifices would also need to be considered to account
for the lower heating (calorific) value of hydrogen relative to
natural gas.
The success of a project such as this could pave the way
one day for a complete conversion of Australia’s gas network
to 100% hydrogen and a carbon free gas industry. The other
challenge will be to one day produce sufficient quantities of
hydrogen to meet demand using renewable energy sources
such as solar and wind power.
For more information refer to the following links:
about-us/media-releases/agn-to-play-leading-role-in-
australian-renewable-energy-pilot-plant
australias-gas-grid/
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