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26
Fig. 26 - W
ater quality standar
d values for cooling water
, chilled water
, mid-range temperatur
e water and make-up water
++
NOTES
*
The nomenclatur
e of items, defi
nition of terms and units shall comply with the JIS K 0101. The units and values in ( ) ar
e conventional ones put her
e for r
efer
ence.
**
The mark X indicates factors af
fecting the corr
osive or scale-forming tendency
.
***
When temperatur
e is high (above 40°C), corr
osiveness generally incr
eases. Especially
, when ir
on/steel surface has no pr
otective film and is in dir
ect contact with water
, it is desirable to take adequate countermeasur
es against corr
osion, such as addition of corr
osion inhibitor and
deaeration tr
eatment
****
For the cooling water system using a closed-type cooling tower
, the water quality standar
d for the mid-range temperatur
e water sysem shall be applied to the closed-cir
cuit r
ecir
culating/spray water and its make-up water
, while the water quality standar
d for the r
ecir
culating
cooling water system shall be applied to the spray water and its make-up water
, r
espectively
.
++
City water
, industrial water and gr
ound water shall be used as sour
ce water
, and demineralized water
, r
eclaimed water
, softened water
, etc. shall be excluded.
+++
The 15 items listed above show typical factors of corr
osion and scale pr
oblems.
Cooling water systems****
Chilled water systems
Mid-range temperatur
e (20-90°C) water systems***
Tendency**
Lower mid-range temperatur
e
water system
Higher mid-range teperatur
e
water system***
Recir
culating
water
Make-up
water
Once
thr
ough
water
Recir
culating
water (T 20°C)
Make-up water
Recir
culating
water
(20<T<=60°C)
Make-up
water
Recir
culating
water
(60<T<=90°C)
Make-up
water
Corr
osive
S
ca
le
-f
o
rm
in
g
Standar
d items (see footnotes)
pH (25°C)
6.5 - 8.2
6.0 - 8.0
6.8 - 8.0
6.8 - 8.0
6.8 - 8.0
7.0 - 8.0
7.0 - 8.0
7.0 - 8.0
7.0 - 8.0
X
X
Electrical conductivity (25°C)
mS/m
<= 80
<= 30
<= 40
<= 40
<= 30
<= 30
<= 30
<= 30
<= 30
X
X
µS/cm
<= 800
<= 300
<= 400
<= 400
<= 300
<= 300
<= 300
<= 300
<= 300
Chr
oride ion
mg Cl
-
/l
<= 200
<= 50
<= 50
<= 50
<= 50
<= 50
<= 50
<= 30
<= 30
X
Sulfate ion
mg SO
4
-2
/l
<= 200
<= 50
<= 50
<= 50
<= 50
<= 50
<= 50
<= 30
<= 30
X
Acid consumption (pH 4.8)
mg CaCO
3
/l
<= 100
<= 50
<= 50
<= 50
<= 50
<= 50
<= 50
<= 50
<= 50
X
Total har
dness
mg CaCO
3
/l
<= 200
<= 70
<= 70
<= 70
<= 70
<= 70
<= 70
<= 70
<= 70
X
Calcium har
dness
mg CaCO
3
/l
<= 150
<= 50
<= 50
<= 50
<= 50
<= 50
<= 50
<= 50
<= 50
X
Ionic silica
mg SiO
2
/l
<= 50
<= 30
<= 30
<= 30
<= 30
<= 30
<= 30
<= 30
<= 30
X
Refer
ence items (see footnotes)
X
Iron
mg Fe/l
<= 1.0
<= 0.3
<= 1.0
<= 1.0
<= 0.3
<= 1.0
<= 0.3
<= 1.0
<= 0.3
X
Copper
mg Cu/l
<= 0.3
<= 0.1
<= 1.0
<= 1.0
<= 0.1
<= 1.0
<= 0.1
<= 1.0
<= 0.1
X
Sulfide ion
mg S
2-
/l
Not detected
Not detected
Not detected
X
Ammonium ion
mg NH
4
+
/l
<= 1.0
<= 1.0
<= 1.0
<= 1.0
<= 0.1
<= 0.3
<= 0.1
<= 0.1
<= 0.1
X
Residual chlorine
mg Cl/l
<= 0.3
<= 0.3
<= 0.3
<= 0.3
<= 0.3
<= 0.25
<= 0.3
<= 0.1
<= 0.3
X
Fr
ee carbone dioxide
mg CO
2
/l
<= 4.0
<= 4.0
<= 4.0
<= 4.0
<= 4.0
<= 0.4
<= 4.0
<= 0.4
<= 4.0
X
Ryzner stability index
-
6.0 - 7.0
-
-
-
-
-
-
-
-
X
X