ThermoFlex-Manual - 第51页
Section 3 ThermoFlex 3-13 Thermo Scientific T o prevent freezing/glazing of the plate exchanger , The r moFle x75 00 through 24000 chillers r equire the use of 50/50 EG/w ater or 50/50 PG/water belo w 10°C process tempera…
Section 3
3-12 ThermoFlex
Thermo Scientific
Compatibility with
Approved
Fluids
Filtered Tap Water/Single Distilled Water
Filtered drinking water and single distilled water are good choices for
recirculating chillers because the ltering/distilling process used removes
microorganisms that could create biological fouling as well as harmful
particulates and excessive minerals that could cause deposits and scaling.
Chlorine
Short term usage of tap water may not cause any adverse affects on the chiller
or your application, but in the long term problems may arise. To help alleviate
these problems Thermo Fisher Scientic recommends the use of chlorine.
The duration of time that chlorine remains in solution depends on factors
such as water temperature, pH and availability of direct sunlight. We
recommend maintaining chlorine levels at proper levels using chlorine test
strips, generally 1 to 5 ppm is adequate.
For best results, maintain the pH of the uid between 6.5 and 7.5. Do not
add additional chlorine without rst determining the concentration ratio that
already exists in the uid supply. Corrosion and degradation of the circulation
components can result from concentration ratios that are too high. Contact
our customer support for additional information.
Deionized Water
Deionized water is water that has had its mineral ions removed using ion
exchange resins. The purpose of this process is to remove the ions that allow
electrical current to ow more easily through water. This helps to prevent
electrical leaks to ground through the recirculating uid. Deionized water is
classied by the electrical resistance of the water, usually measured in
MΩ/cm, with pure water having a resistance of 18 MΩcm.
Water that has been deionized is in an unbalanced state and will leach the
missing ions from the materials it comes in contact with. The aggressive
nature of this leaching can cause pitting on metal surfaces. It should also
be noted that the deionizing process does not remove microorganisms.
Because of this, it is recommended that only applications that have a specied
requirement for deionized water should use deionized water.
In any case, only deionized water with a resistivity between 1 and 3 MΩcm is
approved for use in Thermo Fisher Scientic recirculating chillers.
Recommended Biocides and Inhibitors
Thermo Fisher Scientic offers a biocide and inhibitor package (NALCO)
premixed with 5 gallons of water or as a kit to be added to water. No other
biocide or inhibitor is recommended for use in our recirculating chillers
.
Biocides are corrosive and can cause irreversible eye damage and skin
burns. They are harmful if inhaled, swallowed or absorbed through the
skin. Refer to the manufacturer's most current MSDS.
WARNING
Section 3
ThermoFlex 3-13
Thermo Scientific
To prevent freezing/glazing of the plate exchanger,
ThermoFlex7500 through 24000 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, seal-less,
magnetically driven pumps should be used 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 uid may need to
be replaced more often. All glycols produce acids in the presence of air
and the uid should be changed 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 uid 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, magnetically
driven pumps should be used 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.
CAUTION
Section 3
3-14 ThermoFlex
Thermo Scientific
Process Fluid Permissible (PPM) Desirable (PPM)
Microbiologicals
(algae, bacteria, fungi) 0 0
Inorganic Chemicals
Calcium <25 <0.6
Chloride <25 <10
Copper <1.3 <1.0
0.020 ppm if fluid in contact with aluminum
Iron <0.3 <0.1
Lead <0.015 0
Magnesium <12 <0.1
Manganese <0.05 <0.03
Nitrates\Nitrites <10 as N 0
Potassium <20 <0.3
Silicate <25 <1.0
Sodium <20 <0.3
Sulfate <25 <1
Hardness <17 <0.05
Total Dissolved Solids <50 <10
Other Parameters
pH 6.5-8.5 7-8
Resistivity 0.01* 0.05-0.1*
* MΩ-cm (compensated to 25°C)
Unfavorably high total ionized solids (TIS) can accelerate the rate of galvanic
corrosion. These contaminants can function as electrolytes which increase
the potential for galvanic cell corrosion and lead to localized corrosion such
as pitting. Eventually, the pitting will become so extensive that refrigerant will
leak into the water reservoir.
As an example, raw water in the United States averages 171 ppm (of NaCl).
The recommended level for use in a water system is between 0.5 to 5.0 ppm
(of NaCl).
Recommendation: Initially ll the tank with distilled or deionized water
within a range of 1-3 M
Ω-cm. (It is acceptable to have the uid drop to the
Process Water
Quality and
Standards
When using the ThermoFlex chiller to circulate through aluminum, a
compatible corrosion inhibitor should be utilized to prevent galvanic
corrosion.
Fluid viscosity should be 50 cSt or less at the lowest temperature used.
Visible pump weepage may occur when compatible glycols, oils or other
additives are used. Pump weepage is considered as a normal operating
condition of mechanical seal pumps.
Additional Fluid
Information