Converting Journal Bearings to Tilting Pad Bearings to

Control Oil Whip & Vibration in a Gas Turbine

Tony DzubayRochester Public Utilities

E & O TECHNICAL CONFERENCEMemphis, Tennessee

April 20, 2005

History

• RPU - SWPC 251 B-2• Built 1974, Low Hours• Controls and Equipment Upgrade 2001• Dual Fuel, Simple Cycle, Peaking, Black

Start, 30MW

Reason for Concern

• Vibration– 1st-Critical Trips– Unpredictable Online Trips– High Average

• Not Seen Before– New Control/Vibration System

• Bentley Nevada 3300

Vibration & Exh Brg Supply Temp60 minutes, 6MW

Trip Caused by Vibration30 minutes, 6MW

Reasons for Vibration

• Oil Whip/Whirl• Journal Bearing Design• Cold Oil• Tight Clearances

Initial Attempts to Remedy

• Balance Move #1– Turbine Center Plane– Turbine Inlet Plane

• Verify/Modify Vibration Trip Limits– <95% speed – Alarm 7.0mils Trip 10mils Delay 3.0sec– >95% speed – Alarm 3.5mils Trip 5.0mils Delay 3.0sec

• Balance Move #2– Generator N.E.E.– Filtered Vibration Analyses

• Rotor Unbalance 0.7 mils• Oil Whip 0.5 – 3.0 mils

Initial Attempts to Remedy cont’d

• Check Mechanical Components– Exhaust Manifold Spring Hanger– Turbine Trunions

Possible Solutions

• Warmer Oil• Refurbish Original Bearings

– Overhaul in 1991 Show Dimensions Acceptable

• Modify Original Bearings– 160 degree to 90 degree arc of contact– Increase in Babbitt Temps– Oil Coolers had Trouble in Past

• Install Tilting Pad Bearing

Tilting Pad Bearing Design

• Kingsbury• Four-Pad Design• Type of Pad - Pivot Point

Bearing Installation

• Ease of Installation• Took 10 Days• Tools Used• Roll old Bearing Out, Roll New In• Three SWPC Staff + One RPU

Tilting Pad Bearing Performance60 minutes, 6MW

With New Bearing Installed

• Another Balance Move• Lower Bearing Drain Temps• Exhaust Bearing Much Lower• Inlet Vibration Increased• Generator N.E.E Increased

– Not enough to Cause Concern

• Able to Hot-Start Unit

Other Benefits

• Audit of Other Equipment• Need to Install New Seals Next

Outage

Questions