LUBE MATTERS 2 – WHAT MY UOA RESULTS ARE TELLING ME

Introduction

The lubricating oil for any machinery needs a variety of properties. The selection of the type and grade of lubricant to be used should be based on the relevant machine operating and service conditions. In addition to its main job of lubrication, the lubricant may be required to keep engine components clean, neutralize acids, transfer heat, fight rust and corrosion.

Since lubricating oil condition can be impacted by operating stresses and contamination, monitoring the oil quality is important. Used Oil Analysis (UOA) comprises tests carried out on a sample of the oil to monitor the physical & chemical changes and ingress of contaminants that the oil may be undergoing.

These tests are usually carried out in specialised laboratories using automated equipment’s. Only a small volume of oil is needed – LUKOIL Marine typically requires 120ml – for a full Routine Used Oil Analysis. This makes routine UOA quick, easy & economical.

What do the analysis results mean?

Normally the test method used will be according to ISO or ASTM standards specified by the OEM. The lab test report signals the condition of the oil. What those signals mean, what may have caused the change & how the change may impact the machinery is described below. The standard test methods used by LUKOIL Marine are also mentioned.

VISCOSITY INCREASE
POSSIBLE CAUSES POSSIBLE EFFECTS

-Wrong grade used/topped up

-Contamination by soot/insoluble/dirt

-Oxidation

-Nitration (mainly gas engines)

-High temperature degradation

-Extended oil drain interval

-Fuel Contamination (Residual fuel)

-Water contamination

-Coolant contamination

-Contamination by waste cyloil (2-S Eng.)

-Low oil top-up

-Engine overheating

-Bearings overheating

-Oil filter bypass

-Increased fuel consumption

-Increased operating coats

-Oil flow issues

-Sludge/deposit formation

-Air entrainment & foaming

ASTM D445-18

VISCOSITY DECREASE
POSSIBLE CAUSES POSSIBLE EFFECTS

-Wrong grade used/topped up

-Fuel dilution

-Shear of VII additives

-Poor lubrication

-Reduction in oil film thickness

-Reduction in load carrying ability

-Metal to metal contact

-Engine overheating

ASTM D445-18

WATER CONTAMINATION
POSSIBLE CAUSES POSSIBLE EFFECTS

-Coolant leak

-Internal leakage (jacket)

-Condensation

-Prolonged Low Load operation

-Rain/Sea water ingress

-Loss of lubricating properties

-Loss of bearing life

-Corrosion

-Emulsion formation

-Increased viscosity

-Foaming

ASTM E2412; ASTM D630416e1;ASTM D9513(2018)

ABNORMAL DECREASE IN BN
POSSIBLE CAUSES POSSIBLE EFFECTS

-High sulphur fuel

-Low oil consumption/top-up

-Extended oil drain interval

-Top-up with low BN oil grade

-Low load operation

-Low cylinder liner temperature

-Poor combustion

-Excess blow-past

-Water ingress (condensed water with scavenge air)

-Other water contamination (purifier, cooler, etc) leading to wash-out of additive

-Raw fuel contamination/dilution of lube oil

-Increased acid number (AN)

-Oil degradation

-Increased wear rate

-Acid build-up in oil

ASTM D2896-15 Procedure B

INCREASE IN BN
POSSIBLE CAUSES POSSIBLE EFFECTS

-Top up with high BN oil grade

-Contamination by cylinder scrape down oil (2-S Engine)

-Additive deposits

-increase in insoluble/soot

-difficulty in centrifuging

-foaming

ASTM D2896-15 Procedure B

INCREASE IN AN
POSSIBLE CAUSES POSSIBLE EFFECTS

-High sulphur fuel

-Ingress of acidic combustion products

-Overheating

-Excessive blow-by

-Additive depletion

-Oxidation by-products

-Extended oil drain intervals

-Corrosion

-Leaching

-Reduced oil life

ASTM D664-18e2 Method A

DECREASE IN FLASH POINT
POSSIBLE CAUSES POSSIBLE EFFECTS

-Contamination by fuel

-Oil degradation

-Increased flammability

-Hazard of crankcase explosion

-Viscosity drops

-Lubricity decline

FP @ 200 °C ASTM D3828-16a Method A; ASTM D3828-16a Method B; ASTM D9218

INCREASE IN SOOT
POSSIBLE CAUSES POSSIBLE EFFECTS

-Improper injector adjustment

-Defective spray pattern

-Improper air/fuel ratio

-Poor fuel quality

-Incomplete combustion

-Low compression

-Worn engine parts/rings

-Low load operation

-Leaky or dirty filters/poor centrifuging

-Insufficient capacity of filter/centrifuge

-Poor engine performance

-Poor fuel economy

-Harmful deposits or sludge

-Increased wear

-Carbon deposits

-Clogged filters, reduced filter life

-Increase Viscosity/oil thickening

-Oil gelling

ASTM D7899-13; ASTM D893-14(2018) ; ASTM E2412

INCREASE IN INSOLUBLES
POSSIBLE CAUSES POSSIBLE EFFECTS

-Wear debris

-Oxidation by-products

-Environmental debris

-Wear debris

-Leaking or dirty filters/poor centrifuging

-Fuel soot

-Additive drop-out

-Extended oil drain intervals

-Insufficient capacity of filter/centrifuge

-Filter plugging

-Poor lubrication

-Deposits

-Formation of sludge

-Accelerated wear

-Decreased oil flow

-Foaming

-Shorter equipment life

ASTM D7899-13; ASTM D893-14 (2018) ; ASTM E2412

Details about ELEMENTAL ANALYSIS, PARTICLE COUNT, and FTIR will be in later articles.

A version of this article was first published in the AUG 2021, Vol. XV; Issue. IX of MER(I).

References:

  1. CIMAC publications
  2. Tribology & Lubrication magazine, STLE (various issues)
  3. Machinery Lubrication magazine (various issues)
  4. Oil Analysis User Guide, Agat Labs Ltd.
  5. LUKOIL Marine UOA reports

About the author:

Sanjiv Wazir is a Technical Adviser with LUKOIL Marine Lubricants. He is a mechanical engineer from IIT-Bombay. He is a marine engineer and a member of the Institute of Marine Engineers. He is a Certified Lubrication Specialist from the Society of Tribologists & Lubrication Engineers (STLE), USA and is a member of the Tribological Society of India. He has contributed to MER on marine lubrication developments in the past, and on oil contamination issues under “Lube Matters”, earlier.

He can be reached at sanjiv@lukoil.com