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Closed
Systems Problems
Black
Iron Oxide
Black
magnetite sludge forms dense sediments
in radiators and the boiler. It clogs
pumps and reduces the flow of water
through pipes and radiators. An
advanced state of corrosion is
indicated when black water can be
drawn from a radiator air bleed,
boiler bleed or a drain cock. Black
oxide is formed in all untreated
heating system.
Red
Iron Oxide
Red
or brown rust is only formed in
heating systems when systems are
aerating. Aeration faults must be
cured when replacing failed components
to prevent further failures.
Hydrogen
Gas (Highly flammable)
Hydrogen
is a by-product of corrosion processes
and may necessitate frequent venting.
Hydrogen is often mistaken for air. It
can be detected by igniting it at a
radiator vent and it burns with a
yellow flame. Gas accumulations
depress the water level, disturbing
the flow pattern in the radiators thus
causing cold radiators.
Galvanic
Effects
Galvanic
corrosion is a well known and
contributes significantly to the
deterioration of central heating
systems. In the presence of the
copper, steel & aluminum become
"sacrificial", just as in a
consumable battery.
Some
of the ways in which galvanic
corrosion occurs are:
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Copper
pipe in electrical contact with
radiator.
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Brass
fittings
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Pieces
of copper in radiators.
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Sediments
of ferrous oxide (magnetite).
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Folds
in steel radiators - stressed
areas sacrificial.
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Impurities
Impurities
in the water can play a very big part
in central heating corrosion
processes. Corrosion rates are
increased by soldering fluxes
containing chlorides. New systems
should be pre-commission cleansed in
accordance with BS7593 to avoid such
problems
Pinhole
or Perforated Radiators
These
have occurred due to localized pitting
as a result of a combination of the
above circumstances.
Boiler
Noises
Localized
boiling can develop where there is
sludge or scale in the heat exchanger
causing very high internal skin
temperatures which results in steam
bubbles forming in the heat exchanger.
Air
in Central Heating Systems
Air
circulating in the water not only
gives rise to rapid corrosion, but
associated noise and the necessity for
frequent venting represent a nuisance.
Aeration indicates the presence of a
FAULT.
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Information
