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PLUMBING CONNECTION
AUTUMN 2015
PLUMBERS UNDER PRESSURE
A
fter 50 years in the plumbing industry I am still
surprised by the lack of understanding when it comes
to gas.
Particular concerns include the servicing of gas
appliances, operating gas pressures and the volume of gas
supplied to an appliance. The situation is made worse by
authorities issuing wrong information.
I served my apprenticeship with a large Melbourne-based
builder, working on multi-storey buildings and large factory
complexes before joining the Gas & Fuel Corporation of
Victoria (G&F) in 1976.
Initially, I was a gas appliance service fitter and foreman/
supervisor in general field applications. Next came six years
with Technical Services, working in association with the G&F
Scientific Services division.
At Technical Services I supervised a team of service fitters
that inspected gas appliances for approval and certification
to Australian Standards, and for G&F appraisal.
Other duties included investigating fires and explosions
for any involvement of gas, and field survey work on
appliances for wear and tear after a number of years’
service. The latter was a form of quality control – identifying
potential problems and suggesting preventive design
features for new appliances.
After ensuring we had a safe working area, the first
things we checked in relation to any gas appliance were the
operating pressure and volume of gas (correct pipe sizing).
If these are not correct, several operational problems can
arise.
G&F field manuals advised that the supply pressure at
the outlet of the gas meter had to be between 1.2kPa and
1.3kPa.
This was to ensure an inlet pressure of I.13kPa at the
appliance control valve. The operating pressure was then
set according to the badge plate of the appliance – in
compliance with approval/certification under the Australian
Standard for that appliance.
THE MINIMUM
Clause 5.2.5 and Table 5.1 of AS/NZ 5601 1:2013 clearly
state that the minimum natural gas operating pressure at
the inlet to an appliance is 1.13kPa.
Note that in a domestic situation where a Type A appliance
is installed, a pressure of 1.13kPa is to be available to the
first appliance control valve device other than a manual
shut off valve. This pressure must also be available to every
appliance in the installation with all of them operating fully
at the same time.
Appendix F of the Standard, “Sizing consumer piping”,
requires the minimum supply pressure from the meter (as
noted in Tables F6, F10 and F23) to be 1.25kPa – as stated
in the G&F field manual.
Without a minimum outlet supply pressure from the gas
meter of 1.2kPa it is impossible to achieve pressure of
1.13kPa at the inlet to a control device.
SYSTEM CODE
The Essential Services Commission (ESC) in Victoria has
released Version 11 of the Gas Distribution System Code,
which came into force on October 13, 2014 (www.esc.vic.
gov.au).
To my bewilderment, this code and versions back to
Version 9 (effective January 2009) require that distribution
companies provide a supply outlet pressure of only 1.1kPa
for meters commonly termed domestic (up to a capacity of
6m³/hr).
CONFLICTING REQUIREMENTS FOR PRESSURE AND VOLUME MAKE IT HARD TO ENSURE SAFE TESTING AND
ADJUSTMENT OF GAS INSTALLATIONS.
ROGER LAMBIE
OUTLINES THE ISSUES.
A:
Shut Off Valve.
B:
N.G. Inlet pressure to be no less than
1.13KPa at this point.
C:
Control Device.
GAS MATTERS
ROGER LAMBIE
A
B
C