Manfred R. Mauntz

CEO

cmc Instruments GmbH

Germany

WearSens®

A new concept in oil

condition monitoring from

start up

WearSens® - Agenda

1. Introduction

2.The problem

3.Existing techniques

4.Wear and how it occurs

5.The effect of additives

6.WearSens® measurement principle

7.Monitoring system

8.Conclusions

The problem

The German Society for Tribology (GFT) estimates potential savings in friction

and wear in Germany to be around € 5 billion per year.

WearSens® can help to realise these savings.

Source: Wintus, Wind Turbine Specialists, Aichtal, Germany, WC 03034 2003

Pittings on the inner rings of the planet roller bearing after 30 months of

operation.

All known methods to detect the pittings online and by laboratory analysis

of the oil failed.

Detection techniques

Existing techniques

start working after

particle formation, after

damage is done

WearSens® comparative

data is obtained from

day 1

• Optimising load

• Indicating service

• Predicting damage

Wear and how it occurs

Source: J. P. Davim,Tribology for Engineers, Woodhead Publishing, Cambridge, UK, 2011

The old view:

Adhesive wear is based on the notion that adhesion occurs

between asperities when they touch and finally separate as wear

particles.

Micro friction model of vibrational loading in rolling-sliding contact

The new view:

Hairline crack initiation

The over rolling

direction is from

left to right.

Source: J. Gegner, W. Nierlich: Mechanical and tribochemical mechanisms of mixed friction induced surface failures of rolling

bearings and modeling of competing shear and tensile stress controlled damage initiation, International Conference

FAILURES OF ROLLING BEARING BEARINGS, Bratislava 2010

1. Passage of roller forms hairline

crack

2. Oil enters crack

3. Motion and temperature cause oil to

degrade into acids and hydrogen

4. Hydrogen causes embrittlement

5. Embrittlement leads to particle

shearing, hence pitting

Principles of WearSens®

The WearSens® unit measures three

components,

• Specific electrical conductivity k

• Relative permittivity er

• Temperature T

The values k and er are determined

independently.

Oils are electrical non-conductors.

The electrical residual conductivity of pure

oils lies in the range below 1 pS/m.

Conductivity & Temperature Conductivity is dependent on

temperature.

The conductivity k of the oil

increases with temperature.

Every liquid has a different

dependence on temperature.

The temperature dependence

of a particular oil can be

calculated by experiment.

The temperature dependence

of a particular oil plus

unknown amount of unknown

pollutant cannot be calculated.

Neural network

To compare measurements at

different temperatures conductivity

is usually expressed as a value at a

set reference temperature.

To do this in our example a self-

learning adaptive temperature

compensation algorithm* is

necessary.

*Gaussian least squares method

with risk function

Source: U. Lämmel: WI Projekt – Neuronale Netze, University of Technology, Business and Design, Wismar 2010

Bearing and Gear Test Rig

Various stress cycles

are run and speeds

and torques measured

on a bearing and gear

test rig.

Zp is the tested

bearing.

Source: B. Sauer: Versuchsanleitung Prüfstand VarioGear, Lehrstuhl für Maschinenelemente und Getriebetechnik,

Universität Kaiserslautern, 2008

Measurement of the electrical

conductivity k vs. running time t

The oil temperature

and conductivity k is

measured against the

running time.

The rate of change of

conductivity at two

different torques can

be clearly seen.

Measurement of the electrical

conductivity k40 vs. running time t

At start up with a speed frequency

of 2000 min-1 and a torque of 150

Nm, a relatively constant alteration

of the conductivity from 0.6 to 0.8

pS/m-3 per minute occurs.

After increasing the load to 330 Nm

at 3000 min–1, the change in

conductivity goes up to 3.8 pS/m-3

minute. After the load increase,

the effect on the change of the oil

conductivity appears stronger.

This data can then be used to

optimise load.

Measurement of the electrical

conductivity k40 vs. running time t

The change in ‘quality

of the machine’ during

the course of the

experiment can be

shown graphically in

the lower diagram.

NB Vibration is only

detected after

irrevocable damage

has occurred.

Inner rings of the tested

cylindrical roller bearing

The damaged inner ring of the tested roller bearing at the end of the

experiment.

Laboratory analysis of the oil samples

Probe 1 Probe 2 Probe 3

Fresh oil

30

Minutes

before end

End of test

WEAR

Eisen Fe mg/kg 1 1 2

Chrom Cr mg/kg 0 0 0

Zinn Sn mg/kg 0 0 0

Aluminium Al mg/kg 0 0 1

Nickel Ni mg/kg 0 0 0

Kupfer Cu mg/kg 0 0 0

Blei Pb mg/kg 0 4 4

PQ-Index ok ok ok

POLLUTION

Silizium, Staub Si mg/kg 1 1 1

Kalium K mg/kg 0 0 1

Natrium Na mg/kg 2 2 3

Wasser % <0,10 <0,10 <0,10

Probe 1 Probe 2 Probe 3

Fresh oil 30 Minutes

before end End of test

OIL CONDITION

Viskosität bei 40°C mm2/s 22,22 22,15 22,1

Viskosität bei

100°C mm2/s 4,18 4,26 4,18

ADDITIVE

Kalzium Ca mg/kg 59 68 57

Magnesium Mg mg/kg 8 6 6

Bor B mg/kg 1 0 0

Zink Zn mg/kg 244 254 246

Phosphor PB mg/kg 224 224 214

Barium Ba mg/kg 0 0 0

Molybdän Mo mg/kg 0 0 0

Schwefel S mg/kg 1835 1795 1719

ADDITIONAL TEST

Neutralisationszahl

mgKOH/

g 0,24 0,20 0,29

State of the art

Formation of pittings after 30 months on the inner rings of

the planet roller bearing with 5 machines in Uckermark

Oil laboratory tests could not diagnose these symptoms.

Source: Wintus, Wind Turbine Specialists, Aichtal, Germany, WC 03034 2003

WearSens® extend the wear reserve

With the WearSens® admissible wear can be controlled. Left picture

shows the usual time development of the wear reserve of a machine.

Conventional condition monitoring cannot prevent the failure.

With the WearSens® in the right picture you can extend the wear

reserve of the machine.

Without WearSens® With WearSens®

Time curve of the relative permittivity er

Additive effect on permittivity

The additives contribute to

the permittivity value.

As they are consumed by

pollutants the permittivity

falls.

Once consumed the

pollutants themselves

cause the permittivity to

rise again.

Use of this data indicates

the need for additive

addition or oil change.

Additive effect

Some oils contain as much as 40% additives to catch particles, water

and other ‘undesirables’. The effect of the additives is not immediate.

WearSens® is able to measure the effects on the bearings before the

additives take effect. At the same time WearSens® will detect the

depletion of the additives.

Permissible working ranges

WearSens® data

allows users to

draw clear

boundaries of

acceptable and

unacceptable

operating ranges

Web based, decentralised

monitoring system

The measuring signals

can be transmitted to

a web-based condition

monitoring system via

LAN, WLAN or serial

interfaces of the

sensor system.

Summary

• WearSens® measures components of

the specific complex impedance of

oils.

• Metal abrasion, broken oil

molecules, acids, oil soap all

contribute directly to the pollution of

the oil and to the conductivity of the

oil.

• The dielectric properties of the oil

are particularly determined by the

water content (in the case of simple

oils) or by the consumption of

additives.

Benefits

• Thus WearSens® online

condition monitoring system

can

• Optimise load vs wear –

run the turbine hard when

the grid is open, extend life

at other times

• Advise timely preventative

maintenance on demand

rather than rigid inspection

intervals

• Reduce downtime

The result – increased efficiency, cost savings

Conclusions

WearSens® with 1 inch tube

connection

• WearSens® works from Day 1

• WearSens® works before

damage occurs

• WearSens® works before

• Vibration technology

• Particle monitoring

technology

• Laboratory analysis

WearSens®

Thank

you!

Any

Questions? Source: Windenergie-Agentur Bremerhaven/Bremen e.V. (WAB), 2011