DiGiacomo, Matthew J.

Huffman, Robert A.

Texas A&amp;M Repository

USE OF SIX SIGMA® TECHNIQUES IN GAS SEAL PANEL TROUBLESHOOTING AND SEAL FAILURE ANALYSIS  BY  ROBERT A. HUFFMAN MANAGER, CENTRIFUGAL COMPRESSOR ENGINEERING GE Energy - Conmec   AND   MATTHEW J. DIGIACOMO CENTRIFUGAL COMPRESSOR DESIGNER  GE Energy – Conmec  2004 Turbomachinery Symposium Houston, TX Six Sigma® Overview Six Sigma® is a process for applying critical thinking to; solve problems, improve processes, and improve products. Six Sigma ® uses a collection of tools that have been used by other Quality Initiatives, but focuses on a process driven implementation of those tools. DMAIC is the Key Acronym > Define – Clearly Define the Problem and Expectations > Measure – Gather Data to enable Conclusions / Decisions to be made  > Analyze – Analyze the Date to make Decisions > Improve – Implement a method to Improve the Situation > Control – Establish Controls to keep from repeating the past Two Case Studies First Case Study is Trouble Shooting a DGS Panel that Experience Operational Irregularities > Buffer Gas Supply Pressure Regulator was being driven to full open due to low Delta P between buffer gas supply and buffer chamber pressures. > Customer afraid had lost the process labyrinth seal in the compressor and facing an outage to correct. Second Case Study is Trouble Shooting Multiple Dry Gas Seal Cartridge Failures > Customer experienced three outages at very short intervals to replace DGS > Failures did not appear consistent in symptoms of the failure beyond high primary vent leakage > After third failure, Conmec becomes involved to trouble shoot  Case 1 - GAS SEAL PANEL IRREGULARITIES FOLLOWING INSTALLATION OF NEW GAS SEAL ASSEMBLIES, UPON START-UP, ALARM SIGNALS LOW BUFFER GAS SUPPLY PRESSURE DELTA Step 1- Define the Problem STEP 2, GATHER DATA - Measure: PDI 1113 TRACKS SIGNIFICANTLY WITH CHANGING BUFFER GAS FLOWRATE PDI 1113 INDICATES 50-180 PSID OVER INLET PRESSURE VERSUS 1-2 PSID NORMAL THRUST LOAD AND POSITION ARE NORMAL AND STABLE PERFORMANCE, (P1, P2, T1, T2, FLOWRATE) APPEAR NORMAL FILTER DP TRACKS WITH CHANGING BUFFER GAS FLOWRATE, 1-5 PSID. PRIMARY VENT FLOWRATES APPEAR NORMAL PDT 1114 & PDI 1115 SHOW < 1 PSID OR REQUIREMENT OF >27 PSID.   VIBRATION LEVELS ARE NORMAL AND STABLE 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.   ANSWER….UNLESS A SIGNIFICANT INCREASE IN PRIMARY SEAL LEAKAGE RATE IS SEEN, NO!!* *SHORTLY AFTER THIS DECISION, AN INCIDENT WITH THE DRIVER FORCED A SHUTDOWN. STEP 2 Cont, BRAINSTORM: •DAMAGED PRIMARY SEAL BOTH ENDS. •DAMAGED PRIMARY SEAL DISCHARGE END ONLY •DAMAGED PRIMARY SEAL INTAKE END ONLY. •FAULTY BALANCE CAVITY PRESSURE INDICATOR PI 1113 •FAULTY BUFFER SUPPLY DELTA INDICATOR PDI 1115 •FAULTY BUFFER SUPPLY DELTA TRANSMITTER PDT 1115 •BLOCKED CONTROL VALVE PDV 1114 •MISSING INBOARD BUFFER CAVITY LABYRINTH SEAL •MISSING INBOARD BUFFER CAVITY LABYRINTH SEAL •BLOCKED ORAFICE PLATES FO1127 & FO1126 (ONE) •BLOCKED ORAFICE PLATES FO1127 & FO1126 (BOTH) •BLOCKED BALANCE LINE •BALANCE PISTON SEAL DAMAGE •HIGH PRESSURE SIDE DELTA TRANSMITTER VALVE BLOCKED •FLOW BYPASSING PRESSURE DELTA INDICATOR PDI 1115 & PDT 1114 •LOW PRESSURE SIDE DELTA TANSMITTER VALVE BLOCKED STEP 3 Analyze, CAUSE AND EFFECT: IN THIS CASE WE WANT TO RANK THE EFFECTS BY THEIR LEVEL OF INFLUENCE ON THE OBSERVATIONS.    1 = NO INFLUENCE  3 = SOME INFLUENCE    9 = LARGE INFLUENCE IN THE NEXT STEP WE WILL CONCENTRATE ON THE LARGE INFLUENCES.   CAUSES             INFLUENCE EFFECT: 9 =  LARGE 3 = SOME  1 = NO INFLUNENCE  PI 1113 READING (BALANCE CAVITY PRESSURE REF)  THRUST BEARING DIRECTION AND BEARING TEMP. PRIMARY VENT FLOWRATE PDT 1114, & PDI 1115 READING (BUFFER SUPPLY DELTA) PDT 1108, PDI 1107 READING (FILTER DP)  COMPRESSOR EFFICIENCY COMPRESSOR DISCHARGE PRESSURE DAMAGED SEAL DISCHARGE END (EITHER ELASTOMER OR FACE DAMAGE, SINGLE OR DUAL FACE  FAILURE)  1  1  9  9  3  1  1 DAMAGED SEAL INTAKE END (EITHER ELASTOMER OR FACE DAMAGE, SINGLE OR DUAL FACE FAILURE)  1  1  9  9  3  1  1 DAMAGED SEALS, BOTH END (EITHER ELASTOMER OR FACE DAMAGE, SINGLE OR DUAL FACE FAILURE)  1  1  9  9  3  1  1  PI 1113 FAULTY  9  1  1  1  1  1  1  PDI 1115 FAULTY  1  1  1  3  1  1  1  PDT 1114 FAULTY  1  1  1  3  3  1  1  PDT 1114 & PDI 1115 FAULTY  1  1  1  9  3  1  1  PDCV 1114 BLOCKED  1  1  1  9  9  1  1 MISSING BUFFER LABYRINTH SEAL EITHER OR BOTH ENDS  1  3  1  3  3  1  1  FO 1126 BLOCKED  1  1  1  3  3  1  1  FO 1127 BLOCKED  1  1  1  3  3  1  1  FO 1127 & F0 1126 BLOCKED  1  1  1  9  9  1  1  BALANCE LINE PLUGGED  9  9  1  9  3  3  3  BALANCE PISTON SEAL DAMAGE  3  1  1  3  3  9  9 GLOBE VALVE BETWEEN PDCV 1114 & PDI 1115 BLOCKED  1  1  1  9  1  1  1 LEAKAGE BYPASSING PDT 1114 & PDI 1115 9 1 1 9 3 1 1 NEEDLE VALVE BETWEEN PI1113 & BALANCE CAVITY BLOCKED  9  1  1  9  1  1  1  STEP 4, ANALYZE CONCENTRATING ON THE HIGH EFFECTS WE ENDED UP WITH ONLY 2 LIKELY CAUSES FOR OUR OBSERVATIONS.   CAUSES             INFLUENCE EFFECT: 9 =  LARGE 3 = SOME  1 = NO INFLUNENCE  PI 1113 READING (BALANCE CAVITY PRESSURE REF)  THRUST BEARING DIRECTION AND BEARING TEMP. PRIMARY VENT FLOWRATE PDT 1114, & PDI 1115 READING (BUFFER SUPPLY DELTA) PDT 1108, PDI 1107 READING (FILTER DP)  COMPRESSOR EFFICIENCY COMPRESSOR DISCHARGE PRESSURE  FLOW BYPASSING PDT 1114 & PDI 1115  9  1  1  9  3  1  1 NEEDLE VALVE BETWEEN PI1113 & BALANCE CAVITY BLOCKED  9  1  1  9  1  1  1  Case 1 - SUMMARY, PANEL IRREGULARITIES INSPECTION OF THE COMPONENTS SHOWED DEBRIS BUILDUP IN THE NEEDLE VALVE ASSEMBLY.   FLOW BYPASSING GAUGES CONTRIBUTED TO THE IREGULARITIES.   THE NEEDLE VALVE WAS CLEANED AND THE BYPASS VALVE PRESSURE TESTED.  UPON RESART, SYSTEM RESPONSE WAS NORMAL Case 2 – Multiple Dry Gas Seal Failures Background > Natural Gas Pipeline Compressor > New Bundle installed with new DGS – Compressor ran ~ 1500 hours – Other Issues caused train to come down – Driver Auxiliary System Failure. No work done to Compressor. – On Start-up, High Primary Vent Leakage at Shutdown Level on both ends of compressor – Replace both DGS > Run ~ 450 and again experience High Primary Vent Leakage Shutdown – Both DGS replaced > 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 – Define Cont Second Failure > Discharge End DGS O-ring show’s signs of heavy nibbling and a white substance in the compressor ports, some small amount of residual oil in ports found > Barrier seal shows signs of damage to carbon ring and face springs Third Failure > Suction End DGS O-ring show’s signs of heavy nibbling, a white substance and small amount of oil in the compressor ports is found. > Barrier seal shows signs of damage to carbon ring and face springs.  Primary Seal O-Ring and Tungsten Face – As removed from Compressor Secondary Seal – As removed from Compressor Case 2- Define Cont Use of Time Line assists in sorting out the facts.  Are the failures same root cause or are multiple root causes occurring?   Use of Fishbone Diagram help Identify possible root causes – Input from all Stake Holders Case 2 – Measure & Analyze Case 2 - Analyze Case 2 – Field Inspections The Timeline, Fishbone Diagram and FMEA Tools helped to identify several possible root causes Planning of Shutdown to Inspect the machine for these root causes could then be accomplished – Down time, equipment and personnel Do not stop at first “smoking” gun – this method prepared all involved to avoid jumping to a conclusion at the first source of problem found – keep digging to rule out possible root causes or identify multiple root causes. 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 O-Ring • Sever misalignment of compressor to GT » Root cause of misalignment not discovered » Check of alignment records and piping strain made  Case 2 – Summary Cont. > Third DGS failure (~450 run hours) – Heavy nibbling of DGS primary O-Ring • Sever misalignment of compressor to GT » Root cause of misalignment not discovered » Check of alignment records and piping strain made > Other Factors found and addressed – Barrier Seal Failures – buffer gas supply regulation • Oil getting to secondary vent port but not found at primary seal face » Not a root cause but would lead to failure – Detergent cleaning of DGS  • White residue found in DGS port cavities • Testing determined that detergent used to “wash” the seals was reacting with Methanol Alcohol that was also used to wash the seals  » Not found on seal faces, could lead to a failure – practice stopped Case 2 – Summary (Improve) Seals have now logged ~2500 run hours with out signs of problem per End User > Changed Shim Rings > Changed blow down orifice size > Aligned machinery – monitored alignment Changes through first 500 hours of operation > Changed buffer supply regulation system > Stopped use of Detergent cleaning of DGS 

Use of Six Sigma Techniques in Gas Seal Panel Troubleshooting and Seal Failure Analysis

Texas A&M University

USE OF SIX SIGMA® TECHNIQUES IN GAS 
SEAL PANEL TROUBLESHOOTING AND SEAL 
FAILURE ANALYSIS 
 
BY  
ROBERT A. HUFFMAN 
MANAGER, CENTRIFUGAL COMPRESSOR ENGINEERING 
GE Energy - Conmec  
 
AND  
 
MATTHEW J. DIGIACOMO 
CENTRIFUGAL COMPRESSOR DESIGNER  
GE Energy – Conmec 
 
2004 Turbomachinery Symposium 
Houston, TX 
Six Sigma® Overview 
Six Sigma® is a process for applying critical thinking to; solve 
problems, improve processes, and improve products. 
Six Sigma ® uses a collection of tools that have been used by other 
Quality Initiatives, but focuses on a process driven implementation 
of those tools. 
DMAIC is the Key Acronym 
> Define – Clearly Define the Problem and Expectations 
> Measure – Gather Data to enable Conclusions / Decisions to be 
made  
> Analyze – Analyze the Date to make Decisions 
> Improve – Implement a method to Improve the Situation 
> Control – Establish Controls to keep from repeating the past 
Two Case Studies 
First Case Study is Trouble Shooting a DGS Panel that Experience 
Operational Irregularities 
> Buffer Gas Supply Pressure Regulator was being driven to full 
open due to low Delta P between buffer gas supply and buffer 
chamber pressures. 
> Customer afraid had lost the process labyrinth seal in the 
compressor and facing an outage to correct. 
Second Case Study is Trouble Shooting Multiple Dry Gas Seal 
Cartridge Failures 
> Customer experienced three outages at very short intervals to 
replace DGS 
> Failures did not appear consistent in symptoms of the failure 
beyond high primary vent leakage 
> After third failure, Conmec becomes involved to trouble shoot  
Case 1 - GAS SEAL PANEL IRREGULARITIES 
FOLLOWING 
INSTALLATION OF 
NEW GAS SEAL 
ASSEMBLIES, 
UPON START-UP, 
ALARM SIGNALS 
LOW BUFFER GAS 
SUPPLY PRESSURE 
DELTA 
Step 1- Define the 
Problem 
STEP 2, GATHER DATA - Measure: 
PDI 1113 TRACKS 
SIGNIFICANTLY 
WITH CHANGING 
BUFFER GAS 
FLOWRATE 
PDI 1113 INDICATES 
50-180 PSID OVER 
INLET PRESSURE 
VERSUS 1-2 PSID 
NORMAL 
THRUST LOAD AND 
POSITION ARE 
NORMAL AND 
STABLE 
PERFORMANCE, 
(P1, P2, T1, T2, 
FLOWRATE) 
APPEAR NORMAL 
FILTER DP TRACKS 
WITH CHANGING 
BUFFER GAS 
FLOWRATE, 1-5 
PSID. 
PRIMARY VENT 
FLOWRATES 
APPEAR NORMAL 
PDT 1114 & PDI 1115 
SHOW < 1 PSID OR 
REQUIREMENT OF 
>27 PSID.   
VIBRATION LEVELS ARE 
NORMAL AND STABLE 
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.   
ANSWER….UNLESS A SIGNIFICANT INCREASE IN PRIMARY 
SEAL LEAKAGE RATE IS SEEN, NO!!* 
*SHORTLY AFTER THIS DECISION, AN INCIDENT WITH THE DRIVER FORCED A SHUTDOWN. 
STEP 2 Cont, BRAINSTORM: 
•DAMAGED PRIMARY SEAL 
BOTH ENDS. 
•DAMAGED PRIMARY SEAL 
DISCHARGE END ONLY 
•DAMAGED PRIMARY SEAL 
INTAKE END ONLY. 
•FAULTY BALANCE CAVITY 
PRESSURE INDICATOR PI 1113 
•FAULTY BUFFER SUPPLY 
DELTA INDICATOR PDI 1115 
•FAULTY BUFFER SUPPLY 
DELTA TRANSMITTER PDT 1115 
•BLOCKED CONTROL VALVE 
PDV 1114 
•MISSING INBOARD BUFFER 
CAVITY LABYRINTH SEAL 
•MISSING INBOARD BUFFER 
CAVITY LABYRINTH SEAL 
•BLOCKED ORAFICE PLATES 
FO1127 & FO1126 (ONE) 
•BLOCKED ORAFICE PLATES 
FO1127 & FO1126 (BOTH) 
•BLOCKED BALANCE LINE 
•BALANCE PISTON SEAL 
DAMAGE 
•HIGH PRESSURE SIDE DELTA 
TRANSMITTER VALVE BLOCKED 
•FLOW BYPASSING PRESSURE 
DELTA INDICATOR PDI 1115 & PDT 
1114 
•LOW PRESSURE SIDE DELTA 
TANSMITTER VALVE BLOCKED 
STEP 3 Analyze, 
CAUSE AND EFFECT: 
IN THIS CASE WE WANT 
TO RANK THE EFFECTS 
BY THEIR LEVEL OF 
INFLUENCE ON THE 
OBSERVATIONS.   
 1 = NO INFLUENCE 
 3 = SOME INFLUENCE   
 9 = LARGE INFLUENCE 
IN THE NEXT STEP WE 
WILL CONCENTRATE 
ON THE LARGE 
INFLUENCES.   
CAUSES 
 
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DAMAGED SEAL DISCHARGE END 
(EITHER ELASTOMER OR FACE 
DAMAGE, SINGLE OR DUAL FACE  
FAILURE) 
 
1 
 
1 
 
9 
 
9 
 
3 
 
1 
 
1 
DAMAGED SEAL INTAKE END (EITHER 
ELASTOMER OR FACE DAMAGE, SINGLE 
OR DUAL FACE FAILURE) 
 
1 
 
1 
 
9 
 
9 
 
3 
 
1 
 
1 
DAMAGED SEALS, BOTH END (EITHER 
ELASTOMER OR FACE DAMAGE, SINGLE 
OR DUAL FACE FAILURE) 
 
1 
 
1 
 
9 
 
9 
 
3 
 
1 
 
1 
 
PI 1113 FAULTY 
 
9 
 
1 
 
1 
 
1 
 
1 
 
1 
 
1 
 
PDI 1115 FAULTY 
 
1 
 
1 
 
1 
 
3 
 
1 
 
1 
 
1 
 
PDT 1114 FAULTY 
 
1 
 
1 
 
1 
 
3 
 
3 
 
1 
 
1 
 
PDT 1114 & PDI 1115 FAULTY 
 
1 
 
1 
 
1 
 
9 
 
3 
 
1 
 
1 
 
PDCV 1114 BLOCKED 
 
1 
 
1 
 
1 
 
9 
 
9 
 
1 
 
1 
MISSING BUFFER LABYRINTH SEAL 
EITHER OR BOTH ENDS 
 
1 
 
3 
 
1 
 
3 
 
3 
 
1 
 
1 
 
FO 1126 BLOCKED 
 
1 
 
1 
 
1 
 
3 
 
3 
 
1 
 
1 
 
FO 1127 BLOCKED 
 
1 
 
1 
 
1 
 
3 
 
3 
 
1 
 
1 
 
FO 1127 & F0 1126 BLOCKED 
 
1 
 
1 
 
1 
 
9 
 
9 
 
1 
 
1 
 
BALANCE LINE PLUGGED 
 
9 
 
9 
 
1 
 
9 
 
3 
 
3 
 
3 
 
BALANCE PISTON SEAL DAMAGE 
 
3 
 
1 
 
1 
 
3 
 
3 
 
9 
 
9 
GLOBE VALVE BETWEEN PDCV 1114 & 
PDI 1115 BLOCKED 
 
1 
 
1 
 
1 
 
9 
 
1 
 
1 
 
1 
LEAKAGE BYPASSING PDT 1114 & PDI 
1115 9 1 1 9 3 1 1 
NEEDLE VALVE BETWEEN PI1113 & 
BALANCE CAVITY BLOCKED 
 
9 
 
1 
 
1 
 
9 
 
1 
 
1 
 
1 
 
STEP 4, ANALYZE 
CONCENTRATING ON THE HIGH EFFECTS WE ENDED UP WITH ONLY 2 
LIKELY CAUSES FOR OUR OBSERVATIONS.   
CAUSES 
 
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9 
 
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1 
 
9 
 
3 
 
1 
 
1 
NEEDLE VALVE BETWEEN PI1113 & 
BALANCE CAVITY BLOCKED 
 
9 
 
1 
 
1 
 
9 
 
1 
 
1 
 
1 
 
Case 1 - SUMMARY, PANEL IRREGULARITIES 
INSPECTION OF THE 
COMPONENTS SHOWED 
DEBRIS BUILDUP IN THE 
NEEDLE VALVE ASSEMBLY.   
FLOW BYPASSING 
GAUGES CONTRIBUTED 
TO THE IREGULARITIES.   
THE NEEDLE VALVE WAS CLEANED AND THE BYPASS VALVE PRESSURE 
TESTED.  UPON RESART, SYSTEM RESPONSE WAS NORMAL 
Case 2 – Multiple Dry Gas Seal Failures 
Background 
> Natural Gas Pipeline Compressor 
> New Bundle installed with new DGS 
– Compressor ran ~ 1500 hours 
– Other Issues caused train to come down – Driver Auxiliary 
System Failure. No work done to Compressor. 
– On Start-up, High Primary Vent Leakage at Shutdown Level 
on both ends of compressor 
– Replace both DGS 
> Run ~ 450 and again experience High Primary Vent 
Leakage Shutdown 
– Both DGS replaced 
> 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 – Define Cont 
Second Failure 
> Discharge End DGS O-ring 
show’s signs of heavy 
nibbling and a white 
substance in the compressor 
ports, some small amount of 
residual oil in ports found 
> Barrier seal shows signs of 
damage to carbon ring and 
face springs 
Third Failure 
> Suction End DGS O-ring 
show’s signs of heavy 
nibbling, a white substance 
and small amount of oil in the 
compressor ports is found. 
> Barrier seal shows signs of 
damage to carbon ring and 
face springs. 
 
Primary Seal O-Ring and Tungsten Face – As 
removed from Compressor 
Secondary Seal – As removed from Compressor 
Case 2- Define Cont 
Use of Time Line assists in 
sorting out the facts. 
 
Are the failures same root 
cause or are multiple root 
causes occurring?  
 
Use of Fishbone Diagram 
help Identify possible root 
causes – Input from all Stake 
Holders 
Case 2 – Measure & Analyze 
Case 2 - Analyze 
Case 2 – Field Inspections 
The Timeline, Fishbone Diagram and FMEA Tools helped to identify 
several possible root causes 
Planning of Shutdown to Inspect the machine for these root causes could 
then be accomplished – Down time, equipment and personnel 
Do not stop at first “smoking” gun – this method prepared all involved to 
avoid jumping to a conclusion at the first source of problem found – keep 
digging to rule out possible root causes or identify multiple root causes. 
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 O-
Ring 
• Sever misalignment of 
compressor to GT 
» Root cause of misalignment 
not discovered 
» Check of alignment records 
and piping strain made 
 
Case 2 – Summary Cont. 
> Third DGS failure (~450 run hours) 
– Heavy nibbling of DGS primary O-Ring 
• Sever misalignment of compressor to GT 
» Root cause of misalignment not 
discovered 
» Check of alignment records and 
piping strain made 
> Other Factors found and addressed 
– Barrier Seal Failures – buffer gas supply 
regulation 
• Oil getting to secondary vent port but not 
found at primary seal face 
» Not a root cause but would lead to 
failure 
– Detergent cleaning of DGS  
• White residue found in DGS port cavities 
• Testing determined that detergent used 
to “wash” the seals was reacting with 
Methanol Alcohol that was also used to 
wash the seals  
» Not found on seal faces, could lead 
to a failure – practice stopped 
Case 2 – Summary (Improve) 
Seals have now logged ~2500 run hours with out 
signs of problem per End User 
> Changed Shim Rings 
> Changed blow down orifice size 
> Aligned machinery – monitored alignment 
Changes through first 500 hours of operation 
> Changed buffer supply regulation system 
> Stopped use of Detergent cleaning of DGS 


English

https://oaktrust.library.tamu.edu/bitstream/1969.1/163267/1/cs9.pdf

Use of Six Sigma Techniques in Gas Seal Panel Troubleshooting and Seal Failure Analysis

Abstract

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Texas A&M Repository

Texas A&M University

Use of Six Sigma Techniques in Gas Seal Panel Troubleshooting and Seal Failure Analysis

Abstract

Similar works

Full text

Available Versions

Texas A&amp;M Repository

Texas A&M University

Texas A&M Repository