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Paratherm continues the series with this seventh
installment, "Water in Thermal Fluid Systems -- Part
2 of 3 -- Removal". Among the topics addressed in future
TipSheets will be types of heating for process applications,
thermal fluid selection and analysis, system selection,
design, installation, maintenance and troubleshooting,
and cost/benefit analysis.
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You found out the hard way that you have water
in the system. You tracked down and eliminated
the source. If you had significant free-liquid
water, you drained as much as possible from the system
low points.
So you run with the vent open until
the pump stops cavitating and figure you're home free.
Right?
Maybe.
Any steam that does not vent to atmosphere
will condense in the expansion tank (ever wonder why
pinhole leaks develop in the bottom of an expansion
tank?). Because they are covered with fluid, these small
droplets will remain undetected on the bottom of the
tank until they--
1. --get pulled into the main loop
as the system cools down.
2. --turn to steam when they get hit
with hot fluid during a fast start-up.
Since the change in volume when water turns
to steam is about 1000 to 1 (or, think of
a 7-ounce glass of water expanding to 55 gallons of
steam ) it doesn't take much. To ensure complete removal
of water from a system:
1. Keep the expansion tank temperature
above 212°F to prevent any vapor condensation.
2. Add nitrogen to the expansion tank's
headspace to sweep the water vapor from the tank as
it is generated.
The boilout should continue until the
temperature at the pump suction is above 212°F.
Once the system is stable, check for water at all the
low point drains in the expansion tank.
Next month's tip Water in Thermal
Fluid Systems -- Part 3 of 3 -- Prevention ,
will cover keeping water out of your system. With that
edition, TipSheet will offer a comprehensive technical
data sheet on detecting, preventing, and removing water
in thermal fluid systems. Can't wait? Call us at 800-222-3611,
or email info@paratherm.com
For full technical data on Removing Water From The
System, go to:
Technical Data
Sheet: Water in Thermal Oil Systems; Detection, Removal,
and
Prevention
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