Tank shall be provided with an elastomeric EPDM bladder which separates the
system fluid from the tank walls and is suitable for a maximum operating
temperature of 116 degrees C 240 degrees F. Expansion tank acceptance
volume shall be a minimum of [_____] liters gallons as shown. Total tank
size and arrangement shall be as shown. Tank shall be provided with 862
kPa 125 psi pressure relief valve. Tank shall be provided with precharge
pressure of [_____] kPa psi as shown.
2.7.5
Heat Transfer Fluid
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NOTE: In most instances, freezing temperatures at
the project location dictate the use of an
uninhibited propylene-glycol/water solution.
USP/food-grade uninhibited propylene-glycol is a
nontoxic, noncorrosive fluid used by the food
industry, and has been approved for use with single
isolation heat exchangers in closed-loop military
solar energy systems by the Office of the Surgeon
General (DASG) in coordination with the Toxicology
Division of the Army Environmental Hygiene Agency.
The concentration to be used is a function of the
climate where the system is to be located. The
concentration should be either 30 or 50 percent,
with climates that commonly attain freezing
temperatures (those above approximately 2,222
heating Kelvin days (4000 heating degree F days))
receiving the 50 percent solution. Although
inhibited propylene-glycol is often used in
mechanical systems, uninhibited propylene-glycol is
specified for solar systems to eliminate fluid
maintenance requirements. Indicate in equipment
schedules on drawings the heat transfer fluid used,
the concentration, and the maximum operating
temperature to assure proper equipment and materials
compatibility. Water should only be used as a heat
transfer fluid when the direct circulation system is
specified. Items to be shown on the drawings
regarding the heat transfer fluid must include, if
applicable:
a. Use of uninhibited, food-grade propylene- glycol
and distilled water solution
b. 30 or 50 percent concentration
c. Note of tamper resistant seal requirement.
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[Solar collector loop fluid shall be uninhibited USP/food-grade
propylene-glycol and shall be mixed with distilled or demineralized water
to form a [30] [50] percent by volume propylene-glycol solution as shown].
[Solar collector loop fluid shall be potable water.]
2.8
CONTROL AND INSTRUMENTATION SUBSYSTEM
2.8.1
Differential Temperature Control Equipment
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NOTE: At the time of preparation of this
specification, few manufactureRs were producing
SECTION 13600A
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