Cylinder Lubrication : Purpose, Properties and On-board tests

Q. Why Cylinder Lubrication Is Required?
Ans:  Cylinder Lubrication Is Required To Develop An Oil Film Between Piston Rings And Cylinder Liner To Avoid Metal To Metal Contact. In Latest Engines, With Higher Peak Pressure And Cycle Temperature Good Quality Of Cylinder Oil Is Required To Maintain An Oil Film Between The Rings And The Liner For A Long Period Of Time. Apart From Lubrication Its Other Properties Enhance Engine Performance.

Q. State, With Reasons, Five Desirable Properties Of Cylinder Oil Used For An Engine Which Is Burning Residual Fuel.
Ans: Five Desirable Properties Of Cylinder Oil Used For An  engine Which Is Burning Residual Fuel Are;
It Must Effectively Neutralise The Corrosive Effect Of Suphuric Acids Formed During Combustion Of Fuel.
It Must Prevent The Build Up Of Deposits In The Ring Grooves And In Ports Of Port Exhausted Two Stroke Engines.
It Must Be Able To Burn Cleanly, Therefore Leaving As Little As Possible Soft Deposits.
It Must Pocess Adequate Viscosity At High Working Temperatures.
It Must Form An Effective Seal In Conjunction With Piston Rings To Prevent Blow By.

Q. How An Effective Film Can Be Obtained Over The Entire Liner Surface?
Ans: An Effective Oil Film Can Be Obtained Over The Entire Surface Of The Liner By Means Of Cylinder Lubrication.
Oil Is Injected Through A Number Of Holes Drilled In The Liner, Usually Six Or Eight Of These Displaced Circumferentially Around The Liner At A Chosen Vertical Position Within The Piston Stroke. Oil Is Supplied By Pressure Pulses From Positive Displacement Mechanical Lubricators Driven From The Engine Camshaft And Regulated To Deliver Oil At A Given Rate.
Lubricator Quills Are Connected To Each Oil Hole And Contain A Non-return Valve To Prevent Blowback. To Assist In Distribution Of Oil Around The Liner Circumference, Oil Gutters Adjacent To Lubricator Points Angled Downwards To Assist Flow By Gravity Are Fitted. Lubricating Oil Is Spread Over The Length Of The Liner By The Piston Rings During Their Stroke. 

Q. How It Can Be Ensured That The Correct Quantity And Quality Of Cylinder Lubricating Oil Is Being Used?
Ans: It Can Be Assured That The Right Quantity And Quality Of Cylinder Lubricating Oil Is Used By;
The Quantity Is Controlled By Linking The Pump Drive To The Engine Throttle Setting Levers, The Oil Quantity Then Being Regulated To The Power Produced. To Ensure The Quality Of The Oil Used Is Maintained For Lubrication And Not Burnt By Hot Gases, An Accumulator Can Be Fitted To The Cylinder Lubricator Quills So That A Quantity Of Oil Will Enter Each Time The Cylinder Pressure Drops Below That In The Accumulator, Thus Ensuring Oil Does Not Enter The Cylinder When Exposed To Hot Gases.

Q. How A Representative Sample Of Lubricating Oil Is Obtained From The Main Engine System For Analysis?
Ans: To Obtain A Representative Sample Of Lubricating Oil From The Main Engine System; A Clean Sample Bottle Must Be Used, The Sample Must Be Taken From An Area On The System Where There Is A Good Flow, Not From Filters Or The Sump.
The Best Place For The Sample To Be Taken, Would Be From The Lubricating Oil Rail / Supply Line, Ideally The Sample Point Should Be A Dedicated Sample Point To Avoid Accidents. 

Q. Describe Three On Board Tests For Lubricating Oil?
Ans:
The Flow Stick Test: This Is Where The Viscosity Of The Lubricating Oil Is Tested. Two Samples Of Oil Are Used For This Test, One From The System, And The Other, Fresh New Oil. The Flow Stick Contains Two Reservoirs, One For The System Sample And One For The New Fresh Oil, These Reservoirs Are Filled And The Samples Are Allowed To Reach The Same Temperature.The Flow Stick Is Then Tilted From The Horizontal And The Oil Flows Down Two Parallel Chanels, When The Fresh Oil Reaches A Reference Point, The Flow Stick Is Returned To The Horizontal.The Distance Traveled By The Used System Oil Is Compared To That Of The New, Fresh Oil And If The Used Oil Is Between The Two Used Oil Comparison Points, The Used System Oil Is Still In Good Condition.

Water In Oil Test: The % Water In Oil Test Is Used To Give An Indication If Any Of Water In The Lubricating Oil, Here A Fixed Amount Of Oil Is Sampled From The System, Which Is 5ml And Placed In A Capsule Where There Is A 15ml Solution Of White And Reagent. A Lid Incorporating A Pressure Gauge That Is Calibrated To Read % Water In Oil Is Then Screwed Onto The Capsule To Form An Air Tight Seal. The Capsule Is Then Shaken Vigorously For 1 Minute, Then Left To Stand, Any Water In The Lubricating Oil Will React With The White Spirit And Reagent Causing A Rise In Pressure That Will Be Read On The Pressure Gauge As % Water In The Lubricating Oil

Microbiological Degradation Of Oil Test:  This Test Will Give An Indication Of An Infestation Of Microbiological Organisms In The Lubricating Oil. The Test Makes Use Of Slides That Are Coated With A Special Gel, Which Is Dipped In The Sample Of Lubricating Oil, The Slide Is Then Placed In A Test Tube, Sealed And Left To Incubate, Any Growth That Comes About In The Incubation Period Is Then Compared To A Chart To Indicate Any Infestation By Microbiological Organisms.

Q. If No Testing Equipment Was Available, Explain How The Condition Of Lubricating Oil Could Be Assessed On Board?
Ans: If No Test Equipment Is Available On Board, Lubricating Oil Condition Can Be Determined By A Few Simple Tests:
Crackle Test For Water, This Is Where A Sample Of  lubricating Oil Is Take And Placed In A Test Tube, The Test Tube Is Then Heated, Any Water Droplets Will Make A Crackling Noise Due To The Formation Of Bubbles, This Will Only Detect Small Amounts Of Water, For Larger Amounts, A Simple Settling Test Can Be Used.

TBN Can Be Tested By Placing A Drop Of Indicator Solution On To Blotting Paper, This Being Followed By A Drop Sampled Lubricating Oil In The Centre Of The Blotting Paper. A Colour Change Should Take Place Around The Surrounding Area Of The Drop I.e. If The Colour Is Red, This Shows Acid Is Present, Green / Blue Show S Alkaline Presense.
Note: Filters Will Also Give A Good Indication Of The Lubricating Oil Quality.