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Safety Interlocks
WARNING
Check Safety Interlock functions periodically (every 6 months)
to confirm the interlocks will work correctly.
E
O
(EMO)
MERGENCY
FF
A manually activated button breaks a low-voltage control circuit that, in turn,
interrupts line power.
Restarting the pump(s) requires a manual reset of the
twist-lock button.
N
F
L
ITROGEN
LOW
OW
A normally open flow switch breaks when nitrogen supply to the pump (oil
bearing(s) and inter stage injection) drops below its factory set point, opening the
motor starter relay(s) and shutting down the pump.
Restoration of sufficient
nitrogen flow permits restarting the pump.
M
O
OTOR
VERLOAD
Motor overload relays protect the pump motor(s) from overheating due to
extended current draws in excess of the motor rating without tripping due to
current transients such as start up inrush current. Current (for each phase of line
power) passing through a coil heats a bimetallic element simulating motor heating
under load. Under a persistent overload condition, differential expansion of the
bimetallic element opens a contact, which interrupts the motor run circuit. A brief
cool down interval permits restarting the pump.
O
P
VER CURRENT
ROTECTION
The nearly instantaneous current rise from a line-to-line or line-to-ground short
very rapidly heats a thermal element in the circuit breaker, opening of a snap
action switch and interrupting all power to the electrical panel. Manual reset,
which requires clearing the fault condition, is necessary before restarting the pump.
The circuit breaker also serves as a lockable interrupt device for servicing the
pump system.
EBARA
CORPORATION
PM10U
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Troubleshooting
