NDT.net - April 1999, Vol.4 No.4
PACNDT '98 Table of Contents

Lubrication /Lubrication Analysis

D. Banks - Lubri-Tech Lubricants & Fuels Consultants
Corresponding Author Contact:
Email: david.banks@sympatico.ca

Predictive Maintenance/Condition Monitoring
  • What is it?
    • A periodic monitoring of the equipment systems to access their health & condition
    • Results will assist in predicting the mode and time to failure

What are the Benefits?
  • Improved maintenance planning
  • Increased equipment reliability
  • Increased fluid life ( in some instances)
  • Fewer unscheduled shutdowns
  • Reduce catastrophic failures
  • Overall improvement in product quality
  • Improved inventory control
  • Energy savings

What do we Monitor?
  • Temperature
  • Pressure
  • Flow
  • Horsepower
  • Voltage, current
  • Torque
  • Vibration
  • Fluid condition

PRINCIPLE OF LUBRICATION
Animation
Support a sliding load on a friction reducing film.
(Reduce metal to metal contact.)

Key Functions of Lubricants
  • Reduce friction/wear
  • Protect against corrosion and wear
  • Assist sealing
  • Cooling
  • Overcome effects of contaminants

The Different Lubricating Conditions
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HYDRODYNAMIC LUBRICATION
  • Ideal situation
    • No metal contact
    • No wear
  • Conditions
    • Correct viscosity
    • High speed
    • Low load
    • Adequate supply of lubricant

HYDRODYNAMIC LUBRICATION
  • Poor Lubrication
    • Metal-to-metal contact
    • Wear
    • Extreme case can cause welding of the metal surfaces
  • Conditions
    • Low viscosity lubricant
    • Low speed
    • High load
    • Lack of lubricant

BASESTOCK - LUBRICANT PERFORMANCE
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BASE OIL PROPERTIES
  • What determines a base oil's chemical composition?
  • Crude source
    • hydrocarbon types
    • sulphur & nitrogen content
    • viscosity index
    • light or heavy fractions
    • colour & odour

BASE OIL PROPERTIES
  • What determines the base oil's chemical composition
  • Refining technique
    • physical separation
    • chemical alteration

VISCOSITY INDEX
  • VI is a measure of the rate of change of viscosity Vs. temperature
  • The higher the VI, the lower the viscosity change of the oil with temperature

Viscosity / Temperature Comparison
Single Grade VS. Multigrade Oils

NEW PUMP SPECIFICATIONS

NEW PUMP TESTS
  • Both Vickers & Denison have new tests
  • Vickers 25VPF & DenisonT6C are more severe, high performance tests
  • Base stock quality critical in hydraulic fluids, 95% - 98% of formulation.
  • New XHVI stocks offer better oxidation resistance, air release & filtration properties

FLUID DEGREDATION
  • The process of fluid degradation is irreversible

HIGH TEMPERATURE
  • Temperatures in paper machine dryer sections, steel mill rolls etc, combined with water can cause the base oils to break down.
  • High molecular weight products form gums & varnishes & acids, oil reacts with oxygen
  • Yellow metals can act as catalyst and aggravate acid formation. Increases viscosity

WATER
  • Lubricants are subject to large amounts of water in some applications
  • Demulsibility important
  • Greases also subject to water contamination
  • Additive systems can be leached out
  • Reduces viscosity

CONTAMINATION
  • Wear metals
  • Paper fibers
  • Storage
    • Airborne dirt
    • All can degrade fluid life and or accelerate degradation.
    • Good filtration essential.

LUBRICANT FILMS
  • In hydrodynamic bearings "oil whip" can occur
  • Self excited destructive vibrations set up
  • Occurs at slightly less than 1/2 running speed
  • Subharmonic resonance occurs exactly at 1/2 or other exact multiple of running speed

FLUID ANALYSIS
SPECTROMETRIC ANALYSIS
  • Many commercial labs today use Inductively Coupled Plasma Spectrometer (ICP) or Direct Current Plasma Spectrometer (DCP)
  • Useful for wear metals, lubricant additives, contamination
  • Measures particles up to 10 microns

VISCOSITY
  • The key property of any lubricant

PARTICLE COUNTS
  • Can measure particles from < 2 to > 100 microns
  • Will measure metallic & non-metallic particles ISO 4406 now common

FERROGRAPHY
  • Use tool to measure size and shape of particle
  • Captures large variety of particle sizes
  • Assists in determining failure mode

TRENDING
  • Any analysis must be done over period of time
  • Trends of contamination levels, types of wear debris, viscosity change will assist in determining optimum lubricant/machine life

SUMMARY
  • There are definite benefits to be derived from have a good PdM program married with a fluid
  • analysis program.
  • Longer system life - equipment & fluid
  • Fewer catastrophic failures
  • Less unscheduled downtime
  • More efficient use of manpower
  • Lower inventory/disposal costs

    THANK YOU

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