Requirements On The Coolant - KEB COMBIVERT F5 Series Instruction Manual

Annex
Table 1.5.2 Electro-chemical voltage series / standard potentials against hydrogen
Material
Aluminium
Manganese
Zinc
Chrome
Iron
Cadmium
C.1.3

Requirements on the coolant

The requirements on the coolant are depending on the ambient conditions, as well as from
the used cooling system. General requirements on the coolant:
Standards
VGB
Cooling water direc-
tive
pH-value
Abrasive
ces
Copper cuttings
Hard water
Soft water
Frost protection
Corrosion
tion
Special requirements for open and half-open cooling systems:
GB - 38
generated Ion Standard po-
Al
3+
Mn
2+
Zn
2+
Cr
3+
Fe
2+
Cd
2+
TrinkwV 2001, DIN EN 12502 part 1-5, DIN 50930 part 6, DVGW work
sheet W216
The VGB cooling water directive (VGB-R 455 P) contains instructions
about common process technology of the cooling. Particularly the in-
teractions between cooling water and components of the cooling sys-
tem are described.
Aluminum is particularly corroded by lixiviums and salts. The optimal
pH value for aluminum should be in the range of 7.5... 8.0.
substan- Abrasive substances as used in abrasive (quartz sand), clogging the
cooling circuit.
Copper cuttings can attach the aluminum and this leads to a galvanic
corrosion. Copper should not be used together with aluminum due to
electro-chemical voltage difference.
Cooling water may not cause scale deposits or loose excretions. It
shall have a low total hardness (<20°d) especially carbon hardness.
Soft water (<7°dH) corrodes the material.
An appropriate antifreeze must be used for applications when the
heat sink or the coolant is exposed temperatures below zero. Use
only products of one manufacturer for a better compatibility with other
additives.
protec- Additives can be used as corrosion protection. In connection with frost
protection the antifreeze must have a concentration of 20...25 Vol %,
in order to avoid a change of the additives.
Material
tential
-1.67 V Copper
-1.05 V Carbon
-0.76 V Silver
-0.71 V Platinum
-0.44 V Gold
-0.40 V Gold
generated Ion Standard po-
Cu
2+
C
2+
Ag
+
Pt
2+
Au
3+
Au
+
tential
0.34 V
0.74 V
0.80 V
1.20 V
1.42 V
1.69 V