Bell & Gossett A01500I Pressurized Expansion Tanks (ASME) - Manual (Page 3)

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OPERATING INSTRUCTIONS
1. Check the expansion tank pre-charge before the system is filled with
water. The charge is 12 psig unless noted otherwise on the tank label.
Check to make sure this is the correct precharge pressure specified for
the system. Precharge should match system fill pressure at point of
tank installation. If increasing precharge, the tank must be connected
immediately to the system. The tank should not be isolated at this
condition. Failure to do so could result in damage to the bladder and
void all warranties.
2. If the tank pre-charge pressure needs to be changed on a dry system
follow the following procedure:
a. Check the expansion tank air pressures at the precharge connection
with an accurate tire type pressure gauge. The pre-charge
connection is the same kind of connection found on automobile
tires.
b. If the pressure is low, charge the tank with nitrogen gas or with oil-
free compressed air. Check the pressure frequently during this
process as you would when filling a tire with air.
3. If, after the system has been filled with water and operating, it is found
that the expansion tank pre-charge must be changed use the following
procedure:
a. Turn off the heat source and allow the system water to cool
to ambient temperature.
b. Close the lock-shield valve in the tank-to-system piping.
c. Open the drain valve or TPV to empty the water from the tank.
d. Check the tank air pressure at the pre-charge connection with
an accurate tire type air gauge.
e. Refer to 2b above.
f. Close the drain valve, open the lock-shield valve and turn on
the heat source.
g. Relock the lock-shield valve.
SERVICE INSTRUCTIONS
1. Check the expansion tank periodically for signs of external leakage or
corrosion, If found, the tank must be replaced.
2. If the tank fails to hold the pre-charge pressure it could be the result of
one of the following.
a. Leakage of air valve. Do not depend on the valve cap to seal leak.
1. Refer to items 3a thru 3d under operating instructions to
prepare the tank so that the air valve core can be changed.
2. If only gas escapes, unscrew the air valve core and replace
with a tire type/Schrader valve core. If liquid escaped refer
to 2b below.
3. Refer to 3e thru 3g under operating instruction to complete
the service procedure.
b. The bladder or diaphragm is leaking as indicated by liquid on
the gas side or the inability of the tank to maintain its gas
cushion. If the tank is a diaphragm type, the tank must be
replaced. Diaphragm tanks can be identified by the model
numbers beginning with a “D” and the absence of a large
flanged opening to remove the bladder. If the tank is a bladder
type, the bladder can be replaced as follows:
1. Refer to items 3a thru 3c under operating instructions to
prepare the system for replacement of the bladder.
2. Depress the center valve core stem on the air side of the
tank, as with a tire valve, to slowly vent off the air or gas
charge.
3. Remove the bolts from the flanged cover to gain access to
the bladder. Series B-LA tanks must be disconnected
from the system. Remove the bottom drain plug to drain fluid.
4. Pull the bladder from the tank through the flanged opening.
5. Make sure all flange surfaces are clean and free of
corrosion so that the new bladder will seal properly. If
corroded, the tank must be replaced.
6. Install the new bladder in the tank by stuffing through the
flange opening in the reverse manner that the old bladder
was removed. The Partial Acceptance tank has a support
pipe, which the bladder will fit around. Insert the new
bladder into bottom of the tank. To make system connection,
align elbow with hole in skirt.
7. Replace the flanged cover and tighten the bolts in a
crisscross pattern. Take care not to exceed the allowable
torque of the bolts. Screw in drain plug.
8. Refer to item 3e thru 3g under operating instructions to
place the system back in operation.
9. Check for gas leaks around the flange connection. If leaks
are found, lightly tighten bolts in a criss-cross pattern,
again being careful not to exceed the allowable torque of
the bolts. If leaking continues, the expansion tank will have
to be replaced.
DANGER: Signs of leakage or corrosion are indications
the tank may explode. Periodically check the expansion tank for
signs of external leakage or corrosion. If found, the tank must be
replaced. Failure to follow these instructions will result in serious
personal injury or death and property damage.
WARNING: Improper use of air charging valve during venting of
air pressure from tank will create a hazardous condition due to
the escape of high velocity gas and/or liquid. Depress the center valve
core stem, as with a tire valve, to slowly vent off gas pressure. Do not
remove the valve core until pressure in the expansion tank has reached
zero. Failure to follow these instructions could result in serious
personal injury or death and property damage.
IMPORTANT: Expansion tank cannot be properly air charged other
than at ambient temperature.
WARNING: Residual system pressure is a serious hazard when
attempting to replace tank bladder. Make sure that all fluid has
stopped draining from the drain valve and the system pressure is zero.
If leaking continues from the drain valve, the lock-shield isolation valve
must be replaced before proceeding. Failure to follow these
instructions could result in serious personal injury or death and
property damage.
DANGER: Excessive pressure can cause tank to explode.
Exercise care when filling a tank with air so the pressure does
not exceed that required or does not exceed the working pressure of
the tank as stamped on the nameplate. Failure to follow these
instructions will result in serious personal injury or death and property
damage.
WARNING: Removing the bladder housing cover with an air
charge or pressure still in the tank can cause the cover to be
blown off. Make sure that all gas charge pressure and system pressure
is removed from the tank before loosening or removing cover bolts.
Failure to follow these instructions could result in serious personal
injury or death and property damage.