Dry Gas Seal Trouble Shooting
Dry Gas Seal Trouble Shooting
Dry Gas Seal Trouble Shooting
FILTER DP TRACKS
WITH CHANGING
BUFFER GAS
FLOWRATE, 1-5
PSID.
PERFORMANCE,
(P1, P2, T1, T2,
FLOWRATE)
APPEAR NORMAL
SHOULD WE SHUTDOWN??
LOOK AT THE KNOWN FACTS
VIBRATION LEVELS APPEAR NORMAL AND STEADY
PERFORMANCE APPEARS NORMAL
GAS SEAL LEAKAGE APPEARS NORMAL
BEARING TEMPERATURES ARE NORMAL AND STEADY.
BUFFER GAS FLOW APPEARS NORMAL THROUGH THE FILTERS
IF A SEAL HAS NO BUFFER PROLONGED EXPOSURE TO PROCESS GAS WOULD
ALLOW DEPOSITS IN THE SEAL FACES TO BUILD UP LEADING TO SEAL FAILURE.
WITH THE CONTROL VALVE FULL OPEN, THE GAS SEAL SUPPLY, (COMPRESSOR
DISCHARGE) COULD NOT GENERATE ENOUGH PRESSURE DELTA IN THE SUPPLY TO
CAUSE SEAL DAMAGE.
3 = SOME INFLUENCE
9 = LARGE INFLUENCE
IN THE NEXT STEP WE
WILL CONCENTRATE
ON THE LARGE
INFLUENCES.
PI 1113 FAULTY
FO 1126 BLOCKED
FO 1127 BLOCKED
COMPRESSOR
DISCHARGE
PRESSURE
PRIMARY VENT
FLOWRATE
THRUST BEARING
DIRECTION AND
BEARING TEMP.
CAUSES
PI 1113 READING
(BALANCE CAVITY
PRESSURE REF)
COMPRESSOR
EFFICIENCY
1 = NO INFLUENCE
INFLUENCE
EFFECT:
9 = LARGE
3 = SOME
1 = NO INFLUNENCE
STEP 3 Analyze,
CAUSE AND EFFECT:
CAUSES
9
1
1
9
3
1
1
9
1
1
9
1
1
1
COMPRESSOR
DISCHARGE
PRESSURE
PRIMARY VENT
FLOWRATE
THRUST BEARING
DIRECTION AND
BEARING TEMP.
COMPRESSOR
EFFICIENCY
PI 1113 READING
(BALANCE CAVITY
PRESSURE REF)
INFLUENCE
EFFECT:
9 = LARGE
3 = SOME
1 = NO INFLUNENCE
STEP 4, ANALYZE
FLOW BYPASSING
GAUGES CONTRIBUTED
TO THE IREGULARITIES.
THE NEEDLE VALVE WAS CLEANED AND THE BYPASS VALVE PRESSURE
TESTED. UPON RESART, SYSTEM RESPONSE WAS NORMAL
> Run ~ 450 hours and experience third High Primary Vent
Leakage Shutdown
Both DGS replace, High Leakage alarm on opposite end of
Compressor from last failure.
Case 2 - Define
Three failure events that occur at 1500, 450 and 450
approximate hours intervals
First Failure
> Inspection of DGS shows possible explosive
decompression of primary O-ring in DGS on both ends
> Barrier Seal shows damage to carbon rings and face
springs
> Oil contamination from Driver Auxiliary failure
Aux oil pump continued to run while compressor
shut down over night, no barrier seal nitrogen
buffer present.
Case 2 - Analyze
Case 3 - Summary
Multiple Root Causes were Found
> First DGS failure (1500 hours)
Slight nibbling and heavy cracking
of the primary O-Ring
DGS Shim Ring run out axial
oscillation of seal
Explosive Decompression blow
down rate several times faster
then recommended
Oil Flooding of Seals caused
initial shut down fault of GT
auxiliaries symptom
> Second DGS failure (~450 hours)
Heavy nibbling of DGS primary ORing
Sever misalignment of
compressor to GT
Root cause of misalignment
not discovered
Check of alignment records
and piping strain made