AAON LN-140 - Manual (Page 40)

40
Alignment
Alignment is unnecessary on close-coupled
pumps as there is no shaft coupling.
Split-coupled units are accurately aligned at
the factory prior to being shipped and do not
need re-aligning when installed.
Pump Operation
Starting Pump
Ensure that the pump turns freely by hand,
or with some mechanical help such as a
strap and lever on larger pumps. Ensure that
all protective guarding is securely fixed in
position.
The pump must be fully primed on start up.
Fill the pump casing with liquid and rotate
the shaft by hand to remove any air trapped
in the impeller. On split coupled units, any
air trapped in the casing as the system is
filled must be removed by the manual air
vent in the seal flush line. Close-coupled
units are fitted with seal flush/vent lines
piped to the pump suction area. When these
units operate residual air is drawn out of the
pump towards the suction piping.
‘Bump’ or energize the motor momentarily
and check that the rotation corresponds with
the directional arrow on the pump casing. To
reverse rotation of a three phase motor,
interchange any two power leads.
Start the pump with the discharge valve
closed and the suction valve open, and then
gradually open the discharge valve when the
motor is at operating speed. The discharge
valve may be ‘cracked’ or open slightly at
start up to help eliminate trapped air.
When stopping the pump: Close the
discharge valve and de-energize the motor.
DO NOT run the pump against a closed
discharge valve for an extended period of
time. (A few minutes maximum)
Star-Delta motor starters should be fitted
with electronic/mechanical interlocks that
have a timed period of no more than 40
milliseconds before switching from star
(Starting) to delta (Run) connection yet
allow the motor to reach full star (Starting)
speed before switching to delta (Run).
Should the pump be noisy or vibrate on
start-up a common reason is overstated
system head. Check this by calculating the
pump operating head by deducting the
suction pressure gauge value from the
discharge gauge reading. Convert the result
into the units of the pump head as stated on
the pump nameplate and compare the
values. Should the actual pump operating
head be significantly less than the nameplate
head value it is typically permissible to
throttle the discharge isolation valve until
the actual operating head is equal to the
nameplate value.
Any noise or vibration usually disappears.
The system designer or operator should be
made aware of this soon as some adjustment
may be required to the pump impeller
diameter or drive settings, if applicable, to
make the pump suitable for the system as
installed.
Do not run pumps with discharge
valve closed or under very low flow
conditions.
CAUTION
Check rotation arrow prior to
operating the unit.
CAUTION