Main Bearing Analysis and Signatures for Waukesha Engines Four Corners Analyst Analyst Group, G roup, Farmington, NM 15 Nov 2011
Previous Data Research Summary • Previous paper written by Warren Laible “Early Detection of Connecting Rod Bearing Impact Vibrations in High Speed Industrial Gas Engines” – 2011 GMRC & WRI Users Users group • When the bearing material and the crankshaft crankpin journal come in contact with each other in the absence of an effective oil cushion, an impact occurs which generates a resonant ringing of the impacted parts. • When rod bearings knock, the impact event frequency is 2 times RPM (CPM). • The “ringing” frequency is usually in the 2.5 KHz to 5 KHz range (150,000 to 300,000 RPM (CPM). • Use acceleration measurements for early detection and trending of the impacts. • When velocity amplitudes increase because of a rod bearing knock, severe damage is occurring. • Oil analysis may help determine the extent of damage and the components that are affected (bearing or bushing). 2
Minimal Test Equipment
Encoder or OPT
Synch Light
Indicator / Storage device
Accelerometer
Vibration Test Points At Each Main Brg
Courtesy of Dresser Waukesha
Vibration vs. Crank-angle Display
Crank-angle related parade of all bearing test points
Crank Phased Data With Cylinder Mechanical Events 5L TDC
C Y L E V E N T S
M A I N B R G
FFT – Acceleration data Jennings C-9-E brg prob Eng Mn Brg 5 Accel
Run 1 Channel 1 F
Overall =
0.5
X: 3198.242 Y: 0.21384 3.198 KHz 191,880 CPM
s ' g
Wide bottomed, bell shaped curve
0 0
1000
2000
3000
Frequency (Hz)
4000
1.411
Waukesha Main Bearing Normal Trace
8
Waukesha 7042 – RC-Cap#3 Abnormal impacts seen in data for #2 main bearing
Abnormal impacts seen in data for #6 main bearing
9
SERVICE BULLETIN IDENT NO: 5-2328F • TOPIC: Crankshafts • SUBJECT: Crankshaft, Main Bearing, And Connecting Rod Identification And Replacement • MODELS AFFECTED: All VHP Gas/Diesel And VHP Series Four® All current production VHP series 6, 12, and 16 cylinder engines are manufactured with: • Tee-drilled crankshafts • Ungrooved lower main bearings
• Fully counterweighted crankshafts • On-center connecting rods The VHP engine has evolved through a number of different stages. It was originally manufactured with an angle-drilled crankshaft . A teedrilled crankshaft was introduced with oil passages to provide and maintain continuous connecting rod bearing lubrication. 10
Angle-Drilled Crankshafts (Original style) • The change in crankshaft drilling, together with ungrooved lower •
main bearings, provides an uninterrupted oil supply to the connecting rods. The main bearing journals of the angle-drilled crankshaft supply one lube oil passage to each adjacent connecting rod.
11
Tee-Drilled Crankshaft (current style) • The main bearing journals of the “Tee” style cross-drilled crankshaft supply lube oil to only one connecting rod. This maintains continuous connecting rod bearing lubrication.
12
Fully Grooved V’s. Ungrooved Lower Main Bearings • All main bearings for angle-drilled crankshafts are fully grooved and have a single locating tang
• The groove has been eliminated from lower main bearings used with tee-drilled crankshafts and a second locating tang has been added • NOTE: The current “ungrooved” lower main bearings actually have two small partial grooves located next to the locating tangs of the bearing
13
Load bearing effect on bearings • Ungrooved lower main bearings have more bearing surface. More surface area provides lower unit loading and greater oil film thickness. The result is an increased load-carrying ability
• The ungrooved lower bearings cannot be used with angle drilled crankshafts or with main bearing caps that have not been modified.
14
Main Bearing Selection - 6 & 12 Cylinder • Angle drilled crankshaft - Front, center, and rear main bearings •
•
•
(upper and lower) are identical. Intermediate main bearings (upper and lower) are identical. The same upper main bearing is used for angle-drilled crankshafts and early tee-drilled crankshafts (grooved, one locating tang, and with two standard oil holes). The current upper main bearing for teedrilled crankshafts is grooved, has one locating tang, and an elongated oil hole. Tee drilled crankshaft - The ungrooved front, center, and rear lower main bearing have two locating tangs, plus the short grooves and oil hole, to permit oil flow to the oil pump idler gear spindle mounted in the front main bearing cap. The intermediate lower main bearings also have two locating tangs and are ungrooved except for two small partial grooves near the tangs. 15
Main Bearing Selection - 16 Cylinder • Front and rear main bearings (upper
•
•
and lower) for angle-drilled crankshafts are identical. Intermediate main bearings (upper and lower) are identical. The same upper main bearing is used for angle-drilled crankshafts as well as for the early tee-drilled crankshafts (grooved, one locating tang, and with two standard oil holes). The current upper main bearing for tee-drilled crankshafts is grooved, has one locating tang and an elongated oil hole. All the lower main bearings for the teedrilled crankshafts have two locating tangs and are ungrooved except for two small partial grooves near the tangs 16
Waukesha Main bearing normal trace • Angle drilled Crank shaft
17
Waukesha 7042 – #2 bearing impacts Tee drilled Crank shaft
Abnormal impacts seen in data for #2 main bearing
18
Waukesha 7042 – FFT Data Tee drilled Crank shaft 1 Accel Run 1 Channel 1 FFT at 1200.0 RPM 08/23/
1.2
Overall =
1.0
2.908 g (rms)
2 Accel Run 1 Channel 1 FFT at 1200.0 RPM 08/23/
1.2
Overall =
1.0
1.313 g (rms)
3 Accel Run 1 Channel 1 FFT at 1200.0 RPM 08/23/
1.2
Overall =
1.0
0.8434 g (rms)
4 Accel Run 1 Channel 1 FFT at 1200.0 RPM 08/23/
1.2
Overall =
1.0
0.8843 g (rms)
5 Accel Run 1 Channel 1 FFT at 1200.0 RPM 08/23/2
1.2
0.8
0.8
0.8
0.8
0.8
0.6
0.6
0.6
0.6
0.6
0.4
0.4
0.4
0.4
0.4
0.2
0.2
0.2
0.2
0
0
200000
0
400000
cel Run 1 Channel 1 Time Waveform at 1200.0 RPM
28 24 20 16 12 8 4 -0. -4 -8 12 16 20 24
0
100
200
6 Accel Run 1 Channel 1 FFT at 1200.0 RPM 08/23/
1.2
Overall =
1.0
0.6266 g (rms)
0
200000
0
400000
cel Run 1 Channel 1 Time Waveform at 1200.0 RPM 0 5.6
cel Run 1 Channel 1 Time Wav eform at 1200.0 RPM
0
200000
400000
cel Run 1 Channel 1 Time Wav eform at 1200.0 RPM 0
11
12
9
10 8 6 4 2
1
0.8
-0.
-1
2.4
200
0
400000
3
0.8
100
200000
5
2.4
0
0.2
0
7
4.0
0.8106 g (rms)
-2
4.0
-3
5.6
-5
7.2
-7
-8
8.8
-9
10
0
100
200
-4 -6
0
100
200
0
100
200
7 Accel Run 1 Channel 1 FFT at 1200.0 RPM 08/23/
1.2
0.8
0.6
0.6
0.4
0.4
Overall =
0.5893 g (rms)
Clear once per revolution seen in waveform data
0.2
0
200000
0
400000
cel Run 1 Channel 1 Time Waveform at 1200.0 RPM
13 11 9 7 5 3 1 -1 -3 -5 -7 -9 11
0
400000
7.2
1.0
0.2
200000
cel Run 1 Channel 1 Time Waveform at 1200.0 RPM
29 25 21 17 13 9 5 1 -3 -7 11 15 19 23 27 31
0.8
0
0
Overall =
1.0
0
100
200
0
200000
400000
cel Run 1 Channel 1 Time Waveform at 1200.0 RPM
6.8 6.0 5.2 4.4 3.6 2.8 2.0 1.2 0.4 0.4 1.2 2.0 2.8 3.6 4.4 5.2 6.0 6.8
0
100
However the Spectrum does not show excessive energy, and should be trended over time
200
19
Waukesha 7042 - #6 bearing impacts Tee drilled Crank shaft
Abnormal twice per revolution impacts seen in data for #6 main bearing
20
Waukesha 7042-GL Tee drilled Crank shaft
Abnormal once per revolution impacts seen in data for #5 main bearing 21
Review of Event crank angle v’s model Engine type
Location
3521 GSI
Conoco
6
5
345/705
2895 GU
EOG
6
5
345/705
2
215/575
4
315/675
5
290/650
3
300/660
4
320/680
Polar Star
5
290/650
EOG
2
215/575
Conoco
2
215/575
Conoco
2
215/575
4
310/670
5
290/650
2&6
300 / 660
5790 GL
Conoco
# of Cyls.
12
Conoco 7042 GSI
7042 GL
Conoco
Exterran
12
12
Exterran Red Cedar
7044 GSI
Bearing #
Event degree
Aera
6
80/251/440/610
Galleon
2
205/565
3
300/660
4
300/660
Conoco Galleon
12
Impact degree delta
360
22
Summary of bearing testing • Waukesha angle drilled crank shafts exhibit the normal bearing • • • • • • • • •
characteristics Waukesha Tee drilled crank shaft main bearings can have both once per turn and twice per turn impacts on newly overhauled engines The Tee style crank impacts may decrease over time, but will not fully disappear The bearing impacting impacts can be normally seen in mains #2 through #6 Normally only one bearing will have impacting Impacts will be observed at exactly 360 degrees apart The first impact will be between 200 and 345 degrees The second impact will be between 560 and 705 degrees RPM does affect the impacting and can move it from bearing to bearing The Impacting will reduce as oil pressure is reduced. 23
Waukesha Bearing characteristics • These impacts do not seem to be due to a bearing fault • Current thinking is that as the oil hole in the crank rotates from
• • • • •
•
the grooved part of the bearing into the solid part a hydraulic shock is present. This also happens when oil hole moves from solid bearing to the grooved hole. Hydraulic shock of the bearing shell is caused by compression or contraction of the lubricating oil being squeezed after the groove closes and pushes back against the crank. These knocks have been seen to lower in amplitude over time. Always follow up with oil analysis for any suspect bearing Reducing oil pressure can eliminate impacting, but will not have an affect on a real bearing failure event Reducing RPM can also change events
Windrock thanks E.Clark (Signet), D.Robbins (Exterran), C.Ricord & A.Althoff (Red Cedar), J Lewis (Conoco) and Warren Johnson (TF Hudgins) for their help with this study. 24
