Checking for water prior to startup
Before starting up a new system, it’s
a good idea to take a sample from a
low point drain into a glass jar. If the
sample is hazy, there is most likely
water in the fluid which must be
removed by a system boilout. A clear
or rust colored layer in the bottom of
the jar is pure water. Draining excess
water from any and all low point
drains will reduce the time necessary
to completely boilout the system.
*NOTE: Just because you don’t see
water in the sample doesn’t mean
that there isn’t any water hiding in
the system. |
Detecting Water After Startup
Water expands by up to 1100 times
its volume when it turns to steam,
which makes it very hard to ignore
in a closed loop thermal fluid system.
Some of the indicators are:
- Low Pump Discharge Pressure -
During a normal cold start-up, the
pump discharge pressure will
gradually decrease as the
temperature increases. If the
pump pressure drops suddenly
after the heater outlet
temperature reaches about 220°F,
water is present. Be on the lookout for any sudden change
- Pump pressure fluctuations -
Trace amounts of water (less than
300-400 ppm) will show up as
pump cavitation. Sometimes these
pressure fluctuations are
misinterpreted or ignored because
the system's heater outlet
temperature is well above
212°F (100°C).
Always remember that an 8 ounce
glass of water will displace 55 gallons
of fluid. The steam bubble will force
fluid up into the expansion tank and
out of the vent if the tank is full.
Serious injury — and possibly fire —
can occur during these incidents,
especially if an open drum is used as
the catch tank.
Boilout the system to remove water
Running the system at low heat
until
the pump pressure stabilizes will not
purge the water from the system - it
only relocates it all to the bottom of
the expansion tank. The only way to
completely remove water is to force it
to flash off as steam through the
expansion tank vent.
| *NOTE: If the system is severely
contaminated, consider completely
replacing the fluid. This will not
eliminate the need for a boilout, but it
will shorten the time required. |
To boilout a system in as fast as
possible:
Make sure that the tank
temperature stays above 212°F. If
your system is not equipped with a
warm-up (boilout) line, consider
running an insulated line with a
valve on it from the heater outlet
directly to the top of the expansion
tank. Temporarily insulating the
tank will also speed things up.
The boilout should continue until the
temperature at the pump suction is
above 220°F (105°C). Once the system
is running properly, check for water in
the bottom of the expansion tank.
Preventing contamination
by water
Water contamination is almost
always self-inflicted.
- Do not "hydro-test" a system with
water. Either pressurize the
system with very dry gas and
use soap solution to test for
leaks or pressurize the fluid after
it has been charged and look for
leaks. You’re going to have
tighten all of the flange bolts,
seals, etc. anyway when the
system has been heated up.
Note: If you are replacing a
component, make sure that the
vendor dries it out thoroughly prior
to installation.
- If fluid must be stored outside,
lay the drum on its side to
prevent water from collecting in
the drum head. If you see any
rust or water stains on the drum
head, do not use the fluid.
- Use a dedicated pump and lines
for charging fluid into the
system. Do not use this pump for
any other materials.
Note: Use only fluid from sealed
drums that have been stored
properly if you have to add fluid
directly into the piping of an
operating system. If you’re not
sure, add the fluid to the
expansion tank.
*NOTE: Use only fluid from sealed
drums that have been stored
properly if you have to add fluid
directly into the piping of an
operating system. If you’re not
sure, add the fluid to the
expansion tank. |
- Install a nitrogen blanket on the
expansion tank in a high
humidity area. Water vapor can
condense in the fluid if the tank
temperature drops below the
dew point during a shutdown. Since the change in volume when water turns to steam could be up to 1600 to 1 (or, think of a 7-ounce
glass of water expanding to 85 gallons of steam ) it doesn't
take much to affect operation. To ensure complete removal
of any residual water from a system:
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| Note:
The information and recommendations in this literature are made in good faith and are believed to be correct as of the below date. You, the user or specifier, should independently determine the suitability and fitness of Paratherm heat transfer fluids for use in your specific application. We warrant that the fluids conform to the specifications in Paratherm literature. Because our assistance is furnished without charge, and because we have no control over the fluid's end use or the conditions under which it will be used, we make no other warranties-expressed or implied, including the warranties of merchantability or fitness for a particular use or purpose (recommendations in this bulletin are not intended nor should be construed as approval to infringe on any existing patent). The user's exclusive remedy, and Paratherm's sole liability is limited to refund of the purchase price or replacement of any product proven to be otherwise than as warranted. Paratherm Corporation will not be liable for incidental or consequential damages of any kind.
Some product names of companies found in Paratherm literature are registered trademarks. This statement is in lieu of individually noting each.
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