1 Oil oxidation impact on Feed pump and turbine performance Presenter: Walter Bischoff.

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Oil oxidation impact on Feed pump and turbine performancePresenter: Walter Bischoff

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Fundamentals observedFundamentals observed

• Issue Reporting and Resolution Inform appropriate person of conditions adverse to quality

• Attention to detail Monitoring equipment for adverse trends Performance monitoring (See the trend from every angle)

• Assertive Engineering Drive issues to resolution

• Teamwork and Cross discipline involvement Combined efforts of Operations Mechanical Maintenance I&C Maintenance Engineering

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All stations are vulnerable to oil oxidation All stations are vulnerable to oil oxidation

• Occurs by not cycling oil and system flushing• Local deposits are undetectable by oil analysis tasks

Oil analysis monitors impurities and will not detect sludge deposit Swapping oil filters will not prevent sludge deposits FME controls will not prevent this vulnerability

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Risks associate with aged oil: OxidationRisks associate with aged oil: Oxidation

•Aged oil forms sludge deposits impacting: Oil pipe orifices Pressure control valves Bearing house inlet ports

Critical instrument connections • Potential to impact generation:

Impact pump/turbine performance Shorten bearing life

• Small bearing house inlets are more susceptible to blockage Down power to perform repairs Low oil pressure trip switches

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How does this happen?How does this happen?

•Sludge and varnish form when oxygenated reaction by-products, such as hydroperoxides and carboxylic acids, combine to form larger molecular species. •When a number of such molecules combine, the process is termed polymerization and results in the formation of large molecules of high molecular weight.•Exposure to O2 in air allows the reaction to occur. • Because the viscosity of an oil is directly related to the size of the molecules, any degree of polymerization will result in an increase in the measured viscosity. • If polymerization continues to such an extent that solid material - sludge and varnish - forms in the oil, as the molecules become too large to remain a liquid.•However this will not be detected if polymerization and sludge deposits are not within the reservoir – in the piping or sensing lines.

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Equipment overviewEquipment overview

• Hydraulic and Lubricating Oil is supplied from a reservoir through by 1 main (1 aux) oil pump.• Pressure control valves port excess oil back to the reservoir• Each RFP/T receives lubricating oil from a common source

RFP Inboard journal bearings RFP outboard journal bearings RFP Thrust bearings (2 inlets) RFPT Inboard journal bearings RFPT outboard journal bearings RFPT thrust bearings

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Hope Creek’s ExperienceHope Creek’s Experience

•Resumed Operation after a refueling outage 11/15/10•‘B’ RFP Inboard bearing metal temperature climbed to 185 degrees F

Normal operating bearing metal temperature is less than 185 degrees F Alarm / alert limit is 190 degrees F Action limit is 200 degrees F All other bearing temperatures indicated less than 180 degrees F

• No external indications of degradation No vibration data to support the rising trend No axial position data to support the rising trend No outage work was performed that could have impacted the bearing Bearing oil header pressures (local and PI) was below the normal limits.

• Indicated 13.5 psig • Normal: 15-20 psig

Other pump and turbine bearings were observed normal and consistent

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Bearing temperature trends for All 6 RFP bearingsBearing temperature trends for All 6 RFP bearings

11/24/10: notification for elevated bearing temp11/24/10: notification for elevated bearing temp

12/3/10: notification to perform troubleshooting12/3/10: notification to perform troubleshooting

12/17/10: Operations receives alarms for high bearing temperature

12/17/10: Operations receives alarms for high bearing temperature

12/22-12/23 performed Troubleshooting plan12/22-12/23 performed Troubleshooting plan

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Bearing temperature trends for All 6 RFP bearingsBearing temperature trends for All 6 RFP bearingsB RFP Bearing metal temperature for CTP > 95 % daily average period

140

150

160

170

180

190

200

12/14/05 7/2/06 1/18/07 8/6/07 2/22/08 9/9/08 3/28/09 10/14/09 5/2/10 11/18/10

Date

Rx

po

wer

an

d O

il te

mp

erat

ure

Bearing metal temp Bearing metal temp Bearing metal temp

Refueling outage 15

RF 16

EPU in process

Summer 2010 data is cooler due to down powers

Refueling outage 14

Refueling outage 13

B RFP Bearing metal temperature for CTP > 95 % daily average period

140

150

160

170

180

190

200

12/14/05 7/2/06 1/18/07 8/6/07 2/22/08 9/9/08 3/28/09 10/14/09 5/2/10 11/18/10

Date

Rx

po

wer

an

d O

il te

mp

erat

ure

Bearing metal temp Bearing metal temp Bearing metal temp

Refueling outage 15

RF 16

EPU in process

Summer 2010 data is cooler due to down powers

Refueling outage 14

Refueling outage 13

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Actions taken as a result of notificationActions taken as a result of notification

• Adverse Condition Monitoring plan• Increase bearing temperature• Reduce Rx power by 1% if temperatures exceed 200 degrees F• Remove RFP for repairs before peak generation season.

•Failure Mode Causal table with Troubleshooting plan• Raise Bearing oil pressure to 18 psig and monitor

• Projections made for bearing metal trends (added to POD) Predicted exceeding the action level during peak March 8th 2011

• Scoped into the next forced outage

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Projected trends based on current rate of RiseProjected trends based on current rate of Rise

Forcast data whenl B RFP inboard bearing metal temperatures will reach 'action' limit of 200 degrees F

y = 0.1347x - 5270.3

180

182

184

186

188

190

192

194

196

198

200

202

204

11/15 11/25 12/5 12/15 12/25 1/4 1/14 1/24 2/3 2/13 2/23 3/5 3/15 3/25

Time

Deg

rees

F

B RFP brg temp Linear (B RFP brg temp)

'Action' bearing temperature is 200 degrees F

Forcast data whenl B RFP inboard bearing metal temperatures will reach 'action' limit of 200 degrees F

y = 0.1347x - 5270.3

180

182

184

186

188

190

192

194

196

198

200

202

204

11/15 11/25 12/5 12/15 12/25 1/4 1/14 1/24 2/3 2/13 2/23 3/5 3/15 3/25

Time

Deg

rees

F

B RFP brg temp Linear (B RFP brg temp)

'Action' bearing temperature is 200 degrees F

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Troubleshooting the oil pressuresTroubleshooting the oil pressures

•Performed on 12/22 and 12/23 to increase oil pressures to upper part of the operating band (13 to 15 psig) and (15 to 18 psig).

Alarm / alert limit is 190 degrees F Action limit is 200 degrees F All other bearing temperatures indicated less than 180 degrees F

• Expected results were inconsistent with actual results. Different Inboard and outboard bearing temperature changes Expected similar drop in bearing temperatures. Bearing temperature rate of rise slowed from 1 degree per 10 days to 1 degree per 20 days. Predicted reaching the action limit June 8th 2011

• No vibration trends •No rising temperatures on the other bearings •Determined that oil blockage somewhere between the oil header and the bearing inlet house.

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Troubleshooting resultsTroubleshooting results

Inboard Bearing tempInboard Bearing temp

Outboard Bearing tempOutboard Bearing temp

Lubricating oil pressureLubricating oil pressure

• Inboard Bearing temp dropped by 2.5 degrees

•Outboard Bearing temp dropped by 5 degrees

• Inboard Bearing temp dropped by 2.5 degrees

•Outboard Bearing temp dropped by 5 degrees

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Projected trends based on current rate of RiseProjected trends based on current rate of RiseFigure 1

B RFP Inboard Bearing metal 10 minute average temperature with a projected trend of a 1 degree rise per 20 days

y = 0.0986x - 3811.5y = 0.0759x - 2891.4

186.5

187

187.5

188

188.5

189

189.5

190

190.5

191

191.5

12/23/10 12/28/10 1/2/11 1/7/11 1/12/11 1/17/11 1/22/11 1/27/11 2/1/11 2/6/11

Time

Bea

rin

g m

etal

tem

p F

B Brg temp after 12/21 T/S B Brg temp after 1/8 DP Linear (B Brg temp after 1/8 DP) Linear (B Brg temp after 12/21 T/S )

1/8 Down power. Bearing temp cooled (meaningless data)

Post 12/22/10 troubleshooting base trend of a 1 degree bearing temperature increase per 20 days

Trend line: Bearing temperature rate of rise is 1 degree per every 13 days.

Trend line: Bearing temperature rate of rise is 1 degree per every 13 days.

Figure 1B RFP Inboard Bearing metal 10 minute average temperature with a projected trend of a 1 degree rise per 20 days

y = 0.0986x - 3811.5y = 0.0759x - 2891.4

186.5

187

187.5

188

188.5

189

189.5

190

190.5

191

191.5

12/23/10 12/28/10 1/2/11 1/7/11 1/12/11 1/17/11 1/22/11 1/27/11 2/1/11 2/6/11

Time

Bea

rin

g m

etal

tem

p F

B Brg temp after 12/21 T/S B Brg temp after 1/8 DP Linear (B Brg temp after 1/8 DP) Linear (B Brg temp after 12/21 T/S )

1/8 Down power. Bearing temp cooled (meaningless data)

Post 12/22/10 troubleshooting base trend of a 1 degree bearing temperature increase per 20 days

Trend line: Bearing temperature rate of rise is 1 degree per every 13 days.

Trend line: Bearing temperature rate of rise is 1 degree per every 13 days.

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Planned March 2011 outage for ‘R’ SRVPlanned March 2011 outage for ‘R’ SRV

•While shut down, the station disassembled the Inboard bearing.

Bearing was normal with no signs of excessive wear Bearing clearances were within tolerance Oil inlet housing and drain was clear of debris and within spec

• The Cause: Oil Blockage Maintenance the pipe from the oil header and bearing house. There is an orifice that fits the pipe to the bearing house. The connection was pressurized with air and sludge shot out of the

pipe. The bearing was starved of oil resulting in elevated bearing

temperatures without vibrations.

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Corrective actions and lessons learnedCorrective actions and lessons learned

•Implemented a PM activity for flushing the system every 6 years regardless of turbine overhaul.

Flushing was only performed with an overhaul

• Lessons learned: Bearing metal temperatures trend up without vibration with low

lubricating oil flow. Maintain Lube Oil supply line free of sludge and residual oil residue

and perform system flushes and inlet piping inspections at a frequency that suits your station (6 years for Hope Creek).

Sludge and residual residue can accumulate even with oil strainers and sampling.

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Questions… Questions…