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Fault
Reason
Does not switch
No power
Faulty signal line
Faulty electronic insert
– FEL 51 connected directly to
L1 and N
Density of liquid too low
Fork encrusted
Fork corroded
(Indication on FEL: red/yellow flashes,
FEL 58: green flashes 0.3 Hz)
FEL 51: Internal resistance of
connected relay too large
FEL 51: Holding current of
connected relay too low
FEL 54: Contacts welded together
(after short-circuit)
Switches
Min-/Max-fail-safe mode set wrongly
incorrectly
Sporadic faulty
Thick heavy foam,
switching
very turbulent conditions,
foaming liquid
Extreme RFI
Extreme vibration
Water in housing
FEL 52: Output overloaded
Switches
FEL 57,
incorrectly after
Behaviour during switch-on test
power failure
(functional test)
Endress+Hauser
Remedy
Check power
Check signal line
Exchange
– always connect FEL 51 via
external load
Set density to > 0.5 at electronic insert
Clean fork
Exchange fork and process
connection
Connect suitable relay
Connected resistor in parallel
with relay
Exchange FEL 54;
put fuse in contact circuit
Set correct mode at electronic insert
Mount Liquiphant in bypass
Use screened cable
Decouple, damp, turn fork 90°
Screw cover and cable gland tight
Reduce load,
(cable) capacitance
Observe switching behaviour of
FEL 57;
After power failure block
plant control for up to 45 s
Trouble-shooting
e
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