Our laboratory specializes in analyzing the
water used in heating systems. Given our
wealth of practical experience, accumulated
over decades, our experienced technicians
can "read" the samples like a book. Most
component manufacturers and standards
institutes define quality requirements that
must be met by the heating water if
trouble-free operation is to be ensured.
Most common criteria
Residues: ideally, the water in a
system is free of residues. The corrosion
products, magnetite (black) and rust
indicate corrosion and can themselves cause
damage (clogging, erosion).
pH: determination of the heating
water's pH is an important factor. Water
with a pH of less than 7 is referred to as
"acid" while water with a pH of 7 - 14 is
referred to as "basic". Water used for
heating must be basic and is regarded as not
promoting corrosion if its pH is no less
than 8.3 and no more than 9.5. A pH that is
too high will tend to erode aluminum
components if the flow conditions are
unfavorable.
Oxygen content: the water used to
fill systems generally contains 5 to 10
mg/l. The ideal value is less than or equal
to 0.1 mg/l. However, measuring the oxygen
content is an involved process in practice
so judgments are generally based on the
other parameters.
Electrical conductivity
m S/cm: the
value should be as low as possible. A figure
of less than 1/3 of the conductance of the
water used to fill the system is regarded as
good. High electrical conductivity promotes
corrosion (electrolyte). In absolute terms,
water with a conductivity greater than 500
m S/cm is
regarded as jeopardizing the system (SWKI
Guideline 97-1). Chemical inhibitors
increase conductivity. However, the current
consensus is that a conductance greater than
1,000 m S/cm
jeopardizes the system, even when inhibitors
are used.
Iron content: the iron content
detected should be negligible. Dissolved
iron is a direct indicator of actual
corrosion phenomena in the heating system.
Hardness: as with conductivity, the
hardness of the water in the system should
be about 1/3 or less of the feed water. High
hardness in heating systems indicates that
fresh water is being fed in or that the
equilibrium has been disturbed by
inhibitors. Systems containing a large
amount of water should be filled with fully
dematerialized water if possible.
Analysis of the heating water is a
central part of an expert assessment and
should prevent bad investments. Generally
speaking, it helps in the following ways:
- Clarifying the need for corrosion
protection measures
- Clarifying the need to clean a system
- Checking the results of system cleaning
- Checking the effect of corrosion
prevention measures
