Danfoss Guidelines for water quality in Danfoss brazed heat exchangers User guide
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Danfoss A/S | Danfoss BU HEX LIC Kamnik Slovenia
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Danfoss A/S
Danfoss Heating Segment - DEN
BU HEX - Local Inspection Center Kamnik Slovenia
Guidelines for water quality in Danfoss brazed heat exchangers with plates of EN 1.4404 ~ AISI 316L
Danfoss has prepared this guideline for the water quality of tap water and district heating water used in plate heat
exchangers of stainless steel (EN 1.4404 ~ AISI 316L) brazed with pure copper (Cu), copper -nickel (CuNi) or
Stainless Steel (StS). It is important to point out that the water specification is not a guarantee against corrosion,
but it must be considered as a tool to avoid the most critical water applications.
Plate
Brazing material
Parameter
Unit
Value or concentration
AISI 316L
W.Nr. 1.4404
Cu
CuNi
StS
pH
< 6.0
o - -
o
6,0 – 7.5
+
o/- o +
7.5 – 10.5
+ + +
+
>10.5
+ o o
+
Conductivity
µS/cm
<10
+ + + + 10 – 500
+ + +
+
500 – 1000
+ o +
+
>1000
+ - o
+
Free Chlorine
mg/l
<0.5
+ + +
+
0.5 – 1
o + +
+
1 – 5
- o o o >5
- - -
-
Ammonia (NH3, NH
4
+
)
mg/l
<2
+ + +
+
2 – 20
+ o o + >20
+ - -
+
Alkalinity (HCO
3
-
)
mg/l
<60
+ + +
+
60 – 300
+ + + + >300
+ o +
+
Sulphate (SO
4
2-
)
mg/l
<100
+ + +
+
100 – 300
+
o/- o +
>300
+ - -
+
HCO
3
-
/ SO
4
2-
mg/l
>1.5
+ + +
+
<1.5
+
o/- o +
Nitrate (NO3)
mg/l
<100
+ + +
+
>100
+ o +
+
Manganese (Mn)
mg/l
<0.1
+ + + + >0.1
+ o o
+
Iron (Fe)
mg/l
<0.2
+ + +
+
>0.2
+ o +
+
* Hardness ratio
[Ca2+, Mg2+]/[HCO
3
-
]
/
0 – 0.3
+ - -
+
0.3 – 0.5
+
o/- + +
>0.5
+ + +
+
+
Good corrosion resistance
o
**Corrosion could happen when more parameters are evaluated with o
o/-
Risk of corrosion
-
Use is not recommended
* Hardness ration limits defined per experience and internal tests in Danfoss laboratory
** In case of three or more parameters evaluated with o consultancy is needed with Consultant for Corrosion & Microbiology or BU HHE Representative
Recommended Chloride concentration to avoid Stress Corrosion Cracking (SCC) in the stainless-steel plates:
Application temperature
Chloride concentration
at T ≤ 20°C
max 1000 mg/l
at T ≤ 50°C
max 400 mg/l
at T ≤ 80°C
max 200 mg/l
at T ≥ 100°C
max 100 mg/l
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