Hitachi RCUE40AG2 Service Manual page 156

Maintenance
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CAUTION
In the beside data, only
chilled circulation water is
defi ned, however, stable
index of 6~7 should be
kept in other cases.
pag. 154
SMGB0003 rev.0 - 11/2006
Acid consumption (pH4.8) = M alkali level
It shows the volume of hydroxide, carbonate and bicarbonate in water. It is a base of
saturation index calculation or prevention of corrosion, rusty water and line formation.
All hardness, calcium hardness
The volume of calcium ion and magnesium ion in water is indicated with mg/l
corresponding to the calcium carbonate . Hardness by calcium ion is called calcium
hardness. This is a cause of line trouble related with temperature, pH, and electrical
conductivity.
Ionic silica
When metallic corrosion products (FE, Zn etc) increase in water, silica produces
compound products reacting with metallic corrosion products, which helps that line is
found easily.
Iron
Iron exists in water as a bicarbonate, a chloride, a hydrosulfate,a hydroxide, iron
bacterium and an organoiron salt, and is a cause of rusty water or line trouble.
Copper
Copper is often melt from copper pipes. Copper is a promoting factor of corrosion
against iron pipes or galvanized steel pipe.
Sulfi de ion
It is a sulfi de dissolved in water. When pH is decreased, sulfi de is dissolved to produce
H S, which causes a heavy corrosion on many metal materials.
2
Ammonium ion
When ammonium exist in water, copper and ammonium react together to produce
complex salt, which leads to copper evolution and fi nally to the corrosion. The volume
of ammonium, producing copper and complex salt, is equivalent in NH
+OH . When water pH value increases, the volume of ammonium also increases, and
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the danger to corrosive becomes higher.
Chlorine residual
It is chlorine remained in the water which has been chlorinated, and is a cause of
corrosion of copper etc.
Free carbon dioxide
It is carbon dioxide gas dissolved in water, and is a cause of iron corrosion or action on
concrete.
Ryzner Stability Index (RSI))
It is a measure of the grade of water corrosion and line production. It is calculated by
the following formula.
RSI = (9.3+A+B-C-D) x 2 –E
A: Dissolved matter index=0.1 (electrical conductivity≒5~50mS/m)., 0.2 (electrical
conductivity≒50~150mS/m)
B: Temperature index <Chilled water>=2.4, <Warm water>=1.6
C: Calcium hardness index = log (calcium hardness) – 0.4
D: Oxygen consumption (pH4.8) index = log[Oxygen consumption (pH4.8)]
E: pH value
RSI < 6: Possibility of line production
6≦RSI < 7: Stable area
RSI≧7: Possibility of corrosion
+ H O ↔NH
+
3 2 4