AAON BL-600 - Manual (Page 41)

41
Horizontal and Vertical Expansion Tanks
ASME PRE-PRESSURIZED
DIAPHRAGM EXPANSION TANKS
FOR HEATING & COOLING SYSTEMS
Vessel Description
Tanks are ASME constructed and pre-
charged. They are designed to absorb the
expansion forces and control the pressure in
heating/cooling systems.
The system’s expanded water (is contained
behind a heavy-duty diaphragm fully
compatible with water/glycol mixtures)
preventing tank corrosion and water logging
problems.
The factory set pre-charge for these tanks is
12 psig (83 kPa).
Materials
Shell – Carbon Steel
Diaphragm – Heavy Duty Butyl
Operating Conditions
Maximum Working Temperature - 240°F
(115°C)
Maximum Working Pressure – 125 psi (862
kPa)
Maintenance Steps & Procedure
Visually inspect tank for damage, which
may occur during transit.
Factory pre-charge pressure may not be
correct for the installation. Tank MUST be
pre-charged to system design fill pressure
BEFORE placing into operation. Remove
pipe plug covering the valve enclosure.
Check and adjust the charge pressure by
adding or releasing air for each application.
Note: If the system has been filled, the tank
must be isolated from the system and the
tank emptied before charging. This ensures
all fluid has exited the diaphragm area and
proper charging will occur.
If the pre-charge adjustment is necessary, oil
and water free compressed air or nitrogen
gas may be used. Check the pre-charge
using an accurate pressure gauge at the
charging valve and adjust as required. Check
air valve for leakage. If evident, replace the
Schrader-type tire valve core.
Do not depend on the valve cap to seal the
leak.
After making sure air charge is correct,
replace pipe plug over the charging valve for
protection.
Set tank in place and pipe system connection
to system. Be sure to include isolation
valve(s) and drain.
Purge air from system BEFORE placing
tank into operation. All models have system
water contained behind diaphragm.
When filling the system with water, open
valves to tank to ensure that any residual air
in the tank is displaced by water.
It is recommended that the pre-charge be
checked annually to ensure proper system
protection and long life for the vessel.