Thermo Scientific Cryo 740 Series, Руководство по эксплуатации и техническому обслуживанию

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7000740r7 Cryo Series 4-1 Thermo Scientific
Section 4
Troubleshooting
Caution
Servicing of the unit must be performed by qualified service
personnel only. ▲
Alarm Description Probable Cause Remedy
Excessive LN
2
use.
Frequent cycling of level control causes
excessive LN
2
loss.
Verify that the liquid nitrogen container meets static evapora-
tion rate.
Verify that a minimum of two inches is maintained between the
high and low level sensors.
Solenoid valve stuck Foreign matter in the valve seat.
Check the liquid level control panel: solenoid valve LED is off,
solenoid is open and liquid nitrogen is flowing. Turn liquid nitro-
gen off at the supply source. Thaw transfer hose and solenoid
valve. Remove coil from solenoid valve and open valve to
expose seat. Inspect seat for foreign matter. Clean seat and
re-assemble valve.
Note Use thread sealant, not teflon tape.
Tape could get inside the valve. in the open position.
▲
Controller calling for LN
2
(solenoid LED on)
Supply tank empty or shut-off valve closed. Replace supply tank.
Open shut-off valve.
Liquid not being delivered to
tank.
Defective solenoid valve.
LN
2
pressure too low (below 10 psi).
Repair or replace solenoid valve.
Controller continually overfills,
solenoid LED is on.
Defective cryo control board.
Defective liquid level probe assembly. Replace cryo control board.
Replace liquid level probe assembly
Low level shut down alarm.
(audible alarm, alarms LED, and
Low Level LED flash).
Insufficient supply of LN
2
(below 10 psi).
Malfunction of low level sensor.
Defective fill solenoid valve.
Replace supply tank or open shut-off valve.
Replace liquid level probe assembly.
Repair or replace fill solenoid valve.
Bypass shutdown alarm (audible
alarm, alarms LED, low level LED
& high level LED flash).
Insufficient supply of LN2 (below 10 psi).
Malfunction of bypass sensor.
Defective bypass solenoid valve. Replace supply tank or open shut-off valve.
Replace bypass sensor.
Repair or replace bypass solenoid valve.
Open sensor alarm (audible
alarm and alarms LED flash, low
and high level LEDs are off). Defective sensor or sensor wiring harness. Repair or replace cryo liquid level probe assembly
Figure 4-1. Alarms