Thermo Scientific NESLAB EX Series Installation, Operation And Maintanance Manual page 48

EX Compatibility with
Recommended Fluids
Filtered/Singled Distilled water
This fluid is recommended primarily because it has all microorganisms that cause biological fouling
removed through vaporizing and condensing the water. However, distilled water does not remain pure
for very long when exposed to the atmosphere. Air-born spores can contaminate the water and
activate algae growth. Chloramine-T is a compatible algaecide that can be used to combat growth but
a more effective maintenance plan would include switching out the fluid with newly distilled water every
six months. The particulates that have been filtered out in the process are also preventative in keeping
the system "clean" of contaminants. Distilling water that contains an additive could increase the
concentration of that additive in the water.
50/50 Uninhibited Ethylene Glycol/Water
Ethylene glycol is used to depress the freezing point of water as a coolant. We recommend not
using the uninhibited (no corrosion additives) above 60°C because it breaks down into acidic by-
products faster at high temperatures. These acidic by-products, especially carbonic acid, are
corrosive to copper. The inhibitors are used to control the corrosion rates by passivating the metal
surfaces with an inert film. Uninhibited ethylene is more corrosive to copper that plain water so
therefore it is not recommended unless it is required for the application.
50/50 Inhibited Ethylene Glycol/ Water
Inhibited glycol can be used to increase the operating temperature range of the fluid but should not
be used as a "pre-mixed anticorrosive" solution. Again, this fluid does break down over time at high
temperatures. Industry standards use a pH standard of 8 to determine when the fluid has become
®
corrosive. Dowtherm is an ethylene based product that contains dipotassium phosphates in a 4%
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concentration. The recommended use of Dowtherm is mixing with distilled or deionized water or
water that contains less than 25 ppm chloride and sulfate and less than 100 ppm total hardness of
CACO3. The general term, inhibited glycol/water, is too close to meaning inhibited water. Inhibited
water can have many types of additives including chromate that will foul the cooling system very
quickly.
50/50 Uninhibited Propylene Glycol/ Water
Although the use of this propylene glycol is similar to ethylene glycol, propylene glycol is consid-
ered "safe" to use in the food industry. Propylene is less dense than ethylene and therefore will
have a tendency to weep more through mechanical seals.
50/50 Inhibited Propylene Glycol/ Water
Same issues as with uninhibited propylene and uninhibited ethylene glycol.
Deionized Water (1-3 MOhmcm, compensated)
This water has had the conductive ions that cause galvanic corrosion between dissimilar metals
removed. However, since this is not the normal state of water, when it is too pure deionized water
is aggressive to metal. The leaching of metallic ions from the metal surface is seen in pitting.
NEVER use flammable or corrosive fluids with this unit. Do not use automotive anti-
freeze. Commercial antifreeze contains silicates that can damage the unit. Use of
automotive antifreeze may void the manufacturer's warranty.
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