L.O analysis

Given below is a medium speed trunk type main engine oil analysis report. With reference to each parameter of this report:

• Is there sufficient additive reserve in circulation oil to protect the engine?

Sufficient additive reserve
– For 4-stroke engine, standard guidance in sump is 1.3g/kW
– In this case, 7200 x 1.3 = 9360kg or 9360/0.9 = 10400L
– Present reserve is only 5000L, less than half
– Therefore insufficient additive reserve to protect the engine

• Analyze the condition of this oil from used oil test results for each parameter by comparing with SAE 30 New oil.

Viscosity
– Increased viscosity is likely due to:
A) High insoluble content
B) HFO (not gas oil) contamination
C) Oxidation due to ageing and high operating temperatures
D) Water contamination (emulsification)
* Max +40%, Min -15% of initial value as per MAN Operation Guide Book

Density
– Increased density is likely due to:
A) High insoluble content
B) HFO contamination
C) Piston blow past, leaky injectors, fuel pump plungers and barrels badly worn
D) Water contamination
* Limit +/- 5% of initial value

Flashpoint
– Reduced flashpoint is likely due to:
A) HFO contamination due to improper combustion, leaking injectors, fuel pump plungers and barrels badly worn
* Minimum 180 degrees Celcius

Water
– Presence of water with trace of chloride is likely due to:
A) Bilge leakages through sump level indicator (or through rubber diaphragm between M/E crankcase and sump tank)
B) Inefficient operation of purifier
C) Crankcase breather pipe condensation as atmosphere has saline nature
– Presence of water without chloride + increase in BN
A) Steam or J.C.W leakages
* Max 0.2%, for short period 0.5%

Trace of Chloride
– Not a sign of contamination
– Inevitable due to nature of environment
* Limit: Trace – Saline

Ash
– Increased ash is likely due to:
A) HFO leakages at Fuel Pump plungers/barrels as HFO has high ash content
B) Check sump tank for rust during batch purificaiton
* Max 2%

Base number
– Reduced base number is likely due to:
A) Insufficient oil volume in circulation
B) Improper/irregular top-up of sump
B) High acids formation due to sulphur in HFO can reduce TBN
* Max +100%, min -30% of initial value

Insolubles
– Pentene/Heptane: Indicates oxidation and metallic deposits present
* Max 2%
– Benzene/Toluene: Indicates solid contaminants present
* Max 1%
1. Equal parts of oil samples are diluted with Pentane and Benzene.
2. Pentane insolubles – Benzene insolubles = degree of oxidation
3. E.g. 3 – 1.5 = 1.5
Increased degree of oxidation above max limit, is likely due to:
A) Insufficient volume of L.O
B) Improper top-up
C) Ageing of oil

• Discuss the effect of continued usage of this oil in the system without taking any corrective measures.

Summary of analysis:
– Increased viscosity, density, water, trace of chloride, ash, insolubles
– Decreased flashpoint and base number

A) Increased viscosity and density
– Affects spreadability of L.O film
– Affects hydrodynamic lubrication -> bearings can experience higher wear
– Causes ineffective purification due to change in density without adjustment of gravity ring

B) Increased water and trace of chloride
– Increased water may lead to emulsification
– Trace of chloride may lead to high temperature corrosion if HFO containing vanadium is used

C) Increased ash
– Associated with abrasive wear and incidence of micro-seizure
– Increased scuffing

D) Increased insolubles
– Leads to L.O foaming and causes
– Pitting on bearing surfaces
– Scoring on bearing/journal surfaces
– High degree of oxidation can lead to
– Higher incidence of lacquering
– Varnish deposits occurring

E) Decreased flashpoint
– Affects cylinder lubrication oil film formation

F) Decreased base number
– Lead to acidic corrosion on liner surfaces

• What lube oil system adjustment and treatment is required for continued use of this oil and safe operation of the engine?

A) Batch purification
– Carry out at first opportunity
– Clean the sump tank
– Reduce water and insolubles content

B) Sump tank volume
– Fill up to right volume
– Regular top up not more than 10% of sump volume

C) Leakages
– Rectify fuel and water leakages

D) Replenishment
– Increase frequency of top up and decrease top-up amount
* Less than 10% of oil amount in circulation
– Do not allow TBN to drop below limit, even for a short interval

E) Follow up
– Operate M/E L.O purifier at optimum throughput
– Send L.O sample for analysis and follow up action
– Carry out elemental (spectrographic) analysis onboard if available

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Rate of Oxidation
At normal service temperatures, the rate of oxidation is insignificant.
Following 3 factors will accelerate oxidation:

A) High temperature
– Local high temperatures will arise in pistons if oil circulation is not continued for about 15 minutes after stopping engine.
– Oil should be circulated before and after opening steam/electric supply to heaters.

B) Air Admixture
– Arrange good venting of sump tank
– Ensure sufficient time for deaeration when oil is “resting” inside the sump tank. Total oil quantity should be such that oil is circulated less than 15~18 times per hour.
– Whole oil quantity should be in circulation to avoid any stagnation (sump tank design).

C) Catalytic Action
– Oxidation will be considerably accelerated if oxidation catalysts are present in the oil.
e.g. Wear particles of copper, ferrous iron and rust.
– Water is likely to condense on tank ceiling to form rust, which then fall into the oil and accelerates oxidation

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L.O sump quantity (2-stroke engine)
Sump quantity (guidance) = L.O pump capacity / 15 = e.g. 1200m3/15 = 80m3 = 80,000L

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Spectrographic analysis
– Monitor wear particles and other elements, plot trend
– Determine engine condition:
A) Bearing wear
B) Gear/chain wear
C) Liner wear
D) Fuel contamination
E) Seawater contamination

Source of metals
A) Aluminum: Piston, bearings, turbocharger casing, fuel
B) Copper: Bearing, stuffing box, pipes, cooler tubes
C) Iron: Cylinder liner, piston rings, crankshaft, camshaft, pipework
D) Nickel: Valves, cooler tubes, fuel
E) Silicon: Grit, fuel: abrasive, antifoam (organic): non-abrasive
F) Sodium: Coolant, seawater, fuel
G) Zinc: Zinc-coated surfaces, oil additive