Temperature Monitoring of PEEK Bearings

May 15-19, 2016

Jie Zhou, Waukesha Bearings

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Content

Problem Statement Goal Literature Review Test Setup Results Summary and Conclusion

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Design Characteristics

High temperature resistance with excellent chemical and fatigue resistance plus thermal stability Retain mechanical properties at 250+ºC Heat distortion temperature (HDT) up to 160ºC virgin; up

to 315ºC with reinforcement Good wear resistance – low coefficient of friction and high

limiting PV properties PEEK and PEEK lining can extend bearing operating limit

PEEK

Leopard, A. J. "Tilting pad bearings-limits of operation." Lubrication Engineering 32.12 (1976): 637-644.

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Solid polymer thrust bearing for water pumps

Forms and Applications of PEEK Bearings

Combined polymer bearing for water-lubricated CHP turbine

Polymer lined thrust bearing for oil-lubricated pumps

Combined solid polymer bearing

Polymer lined tilting journal pad

Polymer lined Flexural Pivot thrust bearing for steam turbines

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Problem Statement

Bearing temperature is an important industry indicator of bearing health; however, traditional temperature monitoring methods used for babbitt bearings might not provide sufficient warning of bearing distress when used with PEEK bearings. Non-traditional methods of temperature monitoring is needed for PEEK bearings.

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Goal

To identify effective temperature monitoring options for PEEK via polymer bearing tests and determine the best method for industrial application and lab testing.

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Garner and Leopard, 1985: Review for Babbitt

Discuss temperature sensor types, position, installation, and alarm/shutdown setting for babbitt (whitemetal) lined fluid film bearings Emphasize the importance of pad temperature, not only

lubrication supply/discharge temperature Function of pad temperature is to provide safeguard of

gradual changes No monitoring benefit of maximum temperature for industrial

application Position sensors where film breakdown could occur Suggest placement of temperature sensors below the bond

line

Garner, Denis R., and A. J. Leopard. "Temperature measurements in fluid film bearings." Proceedings of the 13th Turbomachinery Symposium, College Station, Texas. 1985.

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American Petroleum Institute (API)

API standards address babbitt only

API standards recommend measuring bearing-metal temperature– API 616 Gas turbine 4.8.5.5– API 617 Axial and Centrifugal compressors 2.7.1.2– API 617 Integrally geared compressors 2.7.1.3– “Unless otherwise specified, thrust bearings and radial bearings shall be fitted with bearing-

metal temperature sensors installed in accordance with API std 670”

API 670 specifies 75% location for sensors in tilt pad bearings– 6.1.8.1.2 (tilting pad journal bearings): Either one sensor at 50/75 or two sensors at 25/75

and 75/75 – 6.1.8.2.2 (tilting pad thrust bearings): Temperature sensor at 75/75 location (75% radially and

75% circumferentially)

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Ettles et al., 2003 (PTFE vs. babbitt)

Bearing 1: 8-pad TPT, 464 mm OD; PTFE/OVA thickness: 5/40 mm

Test conditions– Up to 10.2 MPa and 41 m/s– ISO VG32 oil, flooded lubrication

Temperature– Measure lining temperature –

thermocouples (TCs) in PTFE 3 mm below the surface

– Later on, measure fluid film temperature using hole in pad surface

Results– No significant film T difference

between PTFE and babbitt – Higher power loss with PTFE

Ettles, C.M., et al. "Test results for PTFE-faced thrust pads, with direct comparison against Babbitt-faced pads and correlation with analysis." Journal of Tribology 125.4 (2003): 814-823.

Bearing 2: 8-pad TPT, 912 mm OD, spring supported; PTFE/OVA thickness: 2/38.1 mm

Test conditions– Up to 10 MPa and 28 m/s– ISO VG32 oil, flooded lubrication

Temperature – Measure pad metal temperature

below bond line Results

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Glavatskih, 2003: PTFE vs. Babbitt

Bearing– 6-pad equalized TPT, babbitt and PTFE (15% glass fiber) lined

pads, 228.6 mm OD – PTFE thickness: 1.5 mm

Test conditions– Up to 2 MPa., 1500–3000 rpm– ISO VG68 oil, flooded lubrication

Temperature– Measure metal temperature below bond line – TCs 4 mm

below the PTFE surface; 3 mm below babbitt surface– Measure collar temperature

Results– 1.5 mm thick PTFE layer leads to thermal insulation up to 23°C– Collar T similar for both bearings; T_PTFE slightly higher than

T_babbitt– PTFE leads to up to 8% power loss reduction

Glavatskih, S.B. “Evaluating thermal performance of a PTFE-faced tilting pad thrust bearing.” ASME. J. Tribol. 125.2 (2003):319-324. doi:10.1115/1.1506329.

2.0 MPa. T0 -fluid film T at the bottom of PTFE pad

Pad T75/75 and collar T75 T at 3000 rpm

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Glavatskih, 2004: PTFE vs. Babbitt Same bearing as in Glasvatskih, 2003 Present a new method: Measure fluid film temperature via

hole in pad surface and with bypassing hole– “…. compared to conventional industrial methods of

temperature monitoring, provided higher sensitivity to oil film temperature in both steady state and transient operating conditions “

– “Existing methods of temperature measurement are inadequate if applied to PTFE-faced bearings”

Glavatskih, S.B. "A method of temperature monitoring in fluid film bearings." Tribology International 37.2 (2004): 143-148.

Babbitt Bearing

PTFE Bearing

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Babbitt

Fluid film T in hole

Metal T

Glavatskih, 2004: Transient Plot for PTFE and Babbitt Bearing

T_H (fluid film) and T75/75 (metal) generally follow the same trend

PTFE

Fluid film T in hole

Metal T

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Henssler et al., 2015: PEEK with 50% Carbon Fiber

Solid PEEK (50% carbon fiber) pads Journal bearing

– 5-pad TPJ, flooded water lubrication– 1500–6000 rpm, 0.5 MPa

Thrust bearing– 8-pad TPT, flooded water/glycol lubrication– 1500–6000 rpm with 500 rpm step, Up to 3.8 MPa

Measure fluid film temperature via hole in pad surface, 75/75

Results: pass the test

Henssler, Dieter, et al. “Qualification and optimization of Solid Polymer Tilting Pad Bearing for Subsea Pump Application.” 44th Turbomachinery Symposia, 2015.

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Sumi et al., 2014: PEEK vs. babbitt Bearing

– 14-pad TPT, 727 mm OD, PEEK lined (3 mm) and babbitt lined

Test conditions– 12 MPa (steady), 20 MPa (4 seconds); 3600 rpm – Measure fluid film temperature via hole(?) in pad

surface (near pad surface) Results

– No damage after test– Compared to babbitt lined bearing, no significant

temperature or power loss difference

Sumi, Yuki, et al. "Development of thrust bearings with high specific load." ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014.

PEEK Long-term Test Bearing used in MHI internal plant since 2007

– 10-pad TPT, 553 mm OD; PEEK lined (3 mm) Test Conditions

– 3600 rpm, 0.8 MPa, Temperature

– Metal temperature– Photos also suggest fluid film temperature (hole

in pad surface) Results

– 631 start-up/shutdown, total 20,462 hours– Surface looks good

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Zhou et al., 2015: PEEK

Bearing– 8-pad 60% offset self-equalized TPT, PEEK lined,

279 mm OD Test conditions

– ISO VG32 oil, ‘Directed Lubrication’, – Load up to 16.2 MPa at 6000 and 11,000 rpm– Performance study at 1000–13,000 rpm, 0.69–6.9 MPa, max

147 m/s Temperature

– Metal temperature, TC at pivot location below bond line

Results– PEEK lined thrust bearings can operate at higher

bearing unit loads than babbitt lined bearings– PEEK lined thrust bearings can be designed up to

8.0 MPa for modern turbomachinery’s demanding load and speed requirements

– No significant power loss difference between PEEK and babbitt (1-6%)

– Observed small range of temperature variation with PEEK lined pads

– Recommend PEEK for high speed/high load applications when babbitt cannot meet the need

Zhou, Jie, et al. "Experimental Performance Study of a High Speed Oil Lubricated Polymer Thrust Bearing." Lubricants 3.1 (2015): 3-13.Zhou, Jie, et al. " Performance of a PEEK-Lined Tilt Pad Thrust Bearing at High Speeds with Oil Lubrication." 14th EDF/Pprime workshop 2015.

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Literature Review Summary

Babbitt bearing temperature monitoring: – Pad metal temperature is industrial standard practice; lab tests also use fluid film temperature

Polymer bearing temperature monitoring:– Measuring pad fluid film temperature deviates from standard practice– Measuring temperature using fluid film with instrument flush to bearing surface has not been published– No published data relating temperature to bearing distress

Material Max MPa

Max m/s

Pad / metal

Pad / lining

Fluid film /hole

Fluid film /hole with bypass flow

Fluid film / flush with surface

Garner babbitt x x

API babbitt x

Ettles 1 PTFE 10.2 41 x x

Ettles 2 PTFE 10 28 x

Glavatskih PTFE & babbitt 2 28 x x

Henssler PEEK 3.8 72 x

Sumi PEEK & babbitt 16, 20 117 x (?)

Sumi (LT) PEEK 0.8 83 x? x

Zhou PEEK & babbitt 16.2 147 x

Temperature Measurement Method

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The Current Study

Present fluid film temperature in PEEK bearings using sensor flush with pad surface Present fluid film temperature in PEEK bearings using hole in pad

surface located below surface Study options for indicating bearing distress

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Test Rig

750 kW total power ISO VG32 oil 5678 L reservoir 1136 lpm oil pump Individual oil control to all bearings

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Test Trial 1: Measuring Pad Fluid Film Temperature ViaSensor Flush with Pad Surface

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PEEK Lined Pocket Feed TPT

Pocket Feed TPT with 8 PEEK lined steel pads Bearing OD 279 mm 4 pads with TC flush with pad surface,

measuring fluid film T 4 pads with TC embedded in pad backing

material, measuring pad metal T

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Temperature During Performance Test

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0% 20% 40% 60% 80% 100% 120% 140% 160%

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Bearing Load Factor (%)

Fluid Film T at 1000 rpm

Metal T at 1000 rpm

Metal T at 13,000 rpm

Fluid Film T at 13,000 rpm

Steady state test from 1000 to 13,000 rpm Both fluid film T and metal

T changed with load and speed, as expected

PEEK lined pads

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Performance Test: 13,000 rpm

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Metal, 75/75, Pad 7

Fluid Film, 75/75, Pad 1

Bearing Load

PEEK lined pads

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Performance Test: 1000 rpm

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Metal T , 75/75, Pad 7

Fluid Film T, 75/75, Pad 1 Bearing Load

0%20%40%60%80%100%120%140%160%180%

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2300 2400 2500 2600

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Temperature During Ultimate Load Test

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1000 1020 1040 1060 1080 1100 1120 1140 1160 1180 1200

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Fluid Film T, 75/75, Pad 3

Fluid Film T, 75/75, Pad 6

Metal T, 75/75, Pad 2

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Summary: Test Trial 1

Temperature Monitoring– Both fluid film temperature and metal temperature tracked the gradual change of bearing

load and speed– Fluid film temperature (flush with pad surface) swiftly tracked the sudden load change (in

1000 rpm test)

Distress Indication– Caution advised if planning to use fluid film sensor flush w/ pad surface under very high load– Capability of metal temperature of PEEK lined bearing to indicate stress Film temperature sensor resulted in test stopping

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Test Trial 2: Measuring Pad Fluid Film Temperature ViaHole in Pad Surface

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PEEK Lined CQDL TPT with Hole

CQDL (Self-Equalizing ‘Directed Lubrication’) TPT with 8 PEEK lined steel pads 4 pads with TC measuring metal T 1 pad with 75/75 TC measuring fluid film T with hole

in pad surface 11,000 rpm

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Performance Test: 11,000 rpm

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Bearing Load Factor (%)

Fluid film (hole) T

Metal T

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Performance Test: Transient Change in Oil Inlet Temperature During ‘Warm-up’

869

933

886949

888 960

500 600 700 800 900 1000 1100 1200 1300 1400 1500

CQDL Pad Temperature at 8400 rpm & 26% Load

Inlet T

Fluid film (hole) T, 75/75

Metal T, 75/75

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Summary: Test Trial 2

Temperature Monitoring– Both fluid film(hole) temperature and metal temperature tracked the gradual change of

bearing load– Fluid film (hole) temperature had a shorter response time than metal temperature, as

expected Distress Indication

– Caution advised if instrument exposed to fluid film pressure– Not tested yet (prior to annual meeting)

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Test Trial 3: Bearing Distress Indication

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Distress Indication

Using pad fluid film temperature to indicate bearing distress has not been demonstrated– Fluid film (flush with pad surface): TC localized, misleading temperature reading; TC inaccurately indicated unacceptable

temperature change Measuring fluid film (flush surface) temperature not a reliable solution for high load

application – Fluid film (hole): Initial trial sensor unreliable No test data indicating bearing distress

Next : Distress indication using pad metal temperature– Ultimate load test of CQDL TPT with 8 PEEK lined steel pads– 4 pads with TC in metal only– Transient date from ‘ultimate’ load test at 6000 and 11,000 rpm

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PEEK Lined CQDL TPT: Ultimate Load Test at 6000 rpm

200%

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Metal T, 75/75

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PEEK Lined CQDL TPT: Ultimate Load Test at 11,000 rpm

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Bea

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(F)

Elapsed Time (seconds)

Load

Metal T rise over inlet, 75/75

Inlet T trend

PEEK lined pad metal temperature can track change of operating conditions, as in Pocket Feed TPT

Metal temperature indicated distress and the test rig was shut down to prevent rig damage

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Summary and Conclusions Polymer pad temperature measurement:

– Two options: material temperature and fluid film temperature– Five methods: lining material, metal backing material, fluid film (flush with pad), fluid film

(hole), and fluid film (hole) with bypass flow Both material temperature and fluid film temperature can be used to monitor PEEK pads and

track gradual change of operating condition, based on published test data Fluid film (flush with pad surface) method offer fast response, but not suggest for very high

load/high speed application. Fluid film (hole) method also has quick response. Distress indication to be validated via

additional testing Pad metal temperature can indicate bearing distress, as validated by test Recommendation

– Industrial applications: pad metal temperature is a reliable method for bearing health monitoring and an indication of bearing distress

– Lab testing: combination of metal temperature method (ultimate load) and fluid film temperature method (fast response)