Thermo Scientific ThermoFlex Manual De Instrucciones página 107

Section 3
To prevent freezing/glazing of the plate exchanger, ThermoFlex7500
CAUTION
and 10000 chillers require the use of 50/50 EG/water or 50/50 PG/
water below 10°C process temperature.

Uninhibited Ethylene Glycol/Water
Ethylene glycol is used to depress the freezing point of water and should
only be used at temperatures where freeze point suppression is required.
Ethylene glycol does not improve heat transfer and is not recommended for
use as a biocide. Because glycols lower the surface tension of water and do
not evaporate as readily as water, they may cause visible weepage past the
pump seals. If weepage cannot be tolerated use seal-less, magnetically driven
pumps where available.
uninhibited simply means that the glycol does not contain any additives to
prevent corrosion. While uninhibited ethylene glycol is acceptable for use,
the pH level must be closely monitored and the fluid may need to be replaced
more often. Since all glycols produce acids in the presence of air and the fluid
change the glycol if the pH falls below 8. Note that litmus paper will not
work to test the pH of ethylene glycol/water.
Inhibited Ethylene Glycol/Water
Inhibited glycol can help protect the wetted metals within the cooling circuit
from corrosion caused by poor water quality, ethylene glycol oxidation (low
pH) and mixed metals (electrolysis). The inhibitor works by either leaving a
barrier coating on metal surfaces to buffer them from the corrosive fluid or
by creating an oxidized layer that protects the underlying metal (passivating).
Inhibited automotive glycols are never acceptable. They use either silicates or
organic Acid Technology (oAT) as the inhibitor and these components are
not compatible with the polymers used in recirculating chillers including the
pump seals and internal hoses.
Inhibitors may also accelerate pump seal wear and seal-less, use magnetically
driven pumps where available.
Uninhibited Propylene Glycol/Water
Propylene glycol does not transfer heat as well as ethylene glycol, but can be
used when freeze point suppression is required as well as lower toxicity.
Propylene glycol does not function as a biocide and the pH needs to be
maintained the same as with ethylene glycol as it also produces acid when
oxidized.
Inhibited Propylene Glycol/Water
Inhibited propylene glycol has the same properties as uninhibited propylene
glycol and the same concerns as inhibited ethylene glycol.
3-14 ThermoFlex
Thermo Scientific