Category: PRE-SEA CONTENT

A Breathing Apparatus Normally Known As The BA Set Or The SCBA (Self Contained Breathing Apparatus) Is An Equipment Used To Supply Fresh Air For Human Breathing When A Person Is Entering Any Space Where The Atmosphere Is  suspect And May Not Support Human Life.
Such Situations Arise :
1. When Entering Into An Enclosed Space.
2. When Entering Into A Space To Fight Fire.
3. When Entering Into A Space Not Enclosed But Has Been Kept Closed For A Long Period Of Time.
4. Entering Any Other Space Where The Atmosphere Is  suspect.

Breathing Apparatus Are Of Two Types :
1.The Forced Air Breathing Apparatus Which Is An Earlier Version 
2.The Compressed Air Breathing Apparatus Which Is The Later Version
        
Give A Brief Description About The Forced Air Breathing Apparatus?
The Forced Air Breathing Apparatus May Not Be Seen Very Often Today, As Most Ships Are Equipped With Compressed Air Breathing Apparatus, But Is Mentioned Here As A Matter Of Interest.
This Apparatus Consists Of A Face Mask With An Integral Speech Diaphragm, Rubber Breathing Tube, Terylene Harness Assembly With Shackle, Hemp Covered Wire Rope Life Line, Signal Plate, Air Hose And Double Acting Foot Operated Bellows
1.Fresh Air Is Provided By The Bellows And Is Drawn From The Hose By The Wearer's Own Aspiratory Effort.
2. The Equipment Is Situated In Fresh Air, To Windward Of Entry Point.
3. An Exhaling Valve Allows Escape Of Excess And Exhaled Air.
4. The Bellows Can Be Hand, Foot Petal Or Power Operated And Should Be Situated In Fresh Air.
5. A Second Person Is Required To Operate The Bellows To Supply Air To The Wearer.
6. The Air Hose Is Usually Of Sufficient Length That The Wearer Can Reach Any Compartment With The Bellows Kept On The Open Deck Near The Compartment.

Some Of The Disadvantages Of This Apparatus Are:
1. Constant Supply Of Air Is Dependent On The Second Person.
2. Air Tubing Being Long, Has To Be Trailed, It May Get Stuck Between Ladders Or Rungs, It Restricts The Wearer In His Movements Limiting His Area Of Operation.
3. The Air Tubing May Get Cut Or Can Be Damaged Thereby Endangering The Wearer During Operation.
4. The Apparatus Is Bulky.
5. Smoke Bellows Is Not A Positive Pressure Set, Therefore If It Does Not Fit Perfect Perfectly, Contaminated Air May Enter Mask.

How To Use SCBA?
Follow The Manufacturer's Instructions For Connecting The Harness To The Cylinder And Then The Air Hose To The Face Mask.  
1. Lay Down The Harness Assembly With The Pressure Regulator And The Warning Device On The Floor.
2. Open The Straps To Hold The Cylinder, So That The Back Plate Of The Harness Is Clear To Keep The Cylinder.
3. Place A Fully Charged Cylinder On The Harness Back Plate Such That The Connector Nut On The Harness Assembly Fits Into The Cylinder Head.
4. Inspect The Connector Nut To Ensure That The 'O' Ring On The Connector Nut Is Not Damaged.
5. Tighten The Connector Nut Into The Cylinder, Make It Hand Tight.
6. Place Cylinder Straps Around Cylinder, Fit The Bolts Provided On The Cylinder Strap And Tighten It.  Please Note That Securing Arrangement On Different Models Of BA Sets May Be Different.
7. Adjust Shoulder Straps And Waist Belt To Their Full Extent And As Required By The Wearer.
8. Connect The Face Mask To The Connection Provided In The Harness By Means Of The Supply Hose Attached And Quick Connecting Coupling.
9.The Self Contained Breathing Apparatus Is Now Ready To Be Used. 

What Checks To Be Done Before Using BA?
Checks That Have To Be Carried Out Before Using The Apparatus
1. On The Demand Valve There Is A Red Button Or A Lever To Ensure That The Mask Is Maintained Under Positive Pressure At All Times When Worn By The User.  Ensure That This Lever Is Kept Off.
2. Check The Cylinder Pressure. Open The Cylinder Valve Slowly But Fully And Read Off The Pressure Gauge.  Pressure Of The Cylinder Should Be No Less Than 10% Below The Filling Pressure. For Example, In Case The Filling Pressure Is 200 Bar, Then The Meter Reading Should Not Be Less Than 180 Bar.  If It Is Less, Replace The Air Cylinder With A Freshly Charged Full Cylinder. Please Note, Since The Apparatus Has A Restrictor Fitted To Protect The High-pressure Hose And Gauge, It Takes Some Time Before The Pressure Gauge Shows The Full Pressure.  Hence It Is Necessary To Wait About 10 – 15 Seconds Order To Fully Pressurise The System.
3. High Pressure Leak Test : Close The Main Cylinder Valve And Check For Leakage In The System.  The Pressure Gauge Reading Should Not Fall By More Than 10 Bar In One Minute.
4. Check Whistle Warning Unit : Switch On The Positive Pressure Facility By Hand Slowly And Listen To The Air Flow.  Keep A Watch On The Pressure Gauge. When The Pressure Gauge Shows Approximately 50 Bars (about 10 Minutes Usage Time) The Audible Alarm Will Sound. The Audible Alarm Will Continue To Sound Till The Pressure Gauge Comes To Zero.

The Above-mentioned Must Be Necessarily Carried Out Every Time Before Using The Apparatus To Ensure That The Apparatus Is In Good Working Condition.

What Maintenance Is Required For SCBA? 
Care And Maintenance Of The SCBA
1. All Maintenance Should Be Done As Given In The Manufacturer's Instruction Booklet.
2. After Use The Apparatus Should Be Cleaned Thoroughly As Necessary.
3. Check The Face Mask For Any Cracks, Wash And Disinfect The Same.  
4. The Whole Apparatus Should Be Thoroughly Dried Before Assembly.
5. If The Air Cylinder Pressure Is Less Than 5/6th Of The Maximum Rating, Change To A Fresh Fully Charged Air Cylinder.
6. Stow The Apparatus In Such A Condition That It Should Be Ready For Use Immediately.
7. Check Washers, "O" Rings Etc For Any Damage And Replace The Same If Found Defective.
            
What Do You Mean By The Term “Life Line”?
For Each Breathing Apparatus A Fire Proof Life-line Of Sufficient Length And Strength Is Provided, That Is Capable Of Being Attached By Means Of A Snap Hook To The Harness Of The Apparatus Or To A Separate Belt In Order To Prevent The Breathing Apparatus Becoming Detached When The Life Line Is Operated.
         The Life Line Is Used As A Guidance Rope For The Wearer Of The Breathing Apparatus. Life Line Is Also Used As A Means Of Communication Between The Wearer And The Attendant.  Though Modern Communication By Means Of Using A Walkie-talkie Set Is Practised, This Method Also Should Be Learned In Case Of Emergencies.
Signals When Using Life Line
(Follow The Instructions Given On Board As There Can Be Some Difference As Compared To That Stated Below)
1 Pull-I Am Alright (reply) How Are You? (sender)
2 PULLS- GIVE ME SLACK ON THE LINE.
3 PULLS- I AM COMING OUT
4 REPEATED PULLS-DANGER

Emeregency Scape Breathing Device (EEBD) / Emergency Life Support Apparatus (ELSA).
SOLAS Amendment Regulations II-2/13.3.4 And 13.4.3 Came Into Force On 1 July 2002, All Vessels Had To Be Equipped With EEBDs.
Here Are The 10 Points You Need To Know About EEBD.
1. The ELSA Is A Short Duration Compressed Air Breathing Apparatus For Escape Purposes Only.  They Are Not To Be Used For Any Other Purpose Except To Escape To A Safe Zone.
2. The ELSA Is Available In Varying Cylinder Capacities From 1.0 Litre To 3.3 Litres Having Usage Duration Between 5 And 15 Minutes.
3. The Apparatus Is Lightweight, Easy To Carry And Use And Comes In A Flame Retardant, Fluorescent Yellow Carrying Bag.
4. The Cylinders Are Usually Charged To A Pressure Of About 200 Bars.
5. Instant Action : The Constant Flow Air Supply Is Automatically Activated Upon Opening The Bag. A Quick Release Pin Is Fitted To The Pressure Reducing Valve And Attached To The Bag Via A Strap. The Action Of Opening The Bag Pulls The Strap – Thus Releasing The Pin.
6. The Combined Cylinder And Pressure Reducing Valve Is Fitted To The Cylinder And Mechanism With Fixed Orifice Outlet; The Valve Indicator And Warning Whistle Which Sounds When The Designated Duration Is Reached. A Pressure Relief Valve Protects The System From Over Pressurisation.
7. The Air Hood May Utilise A Cuboid Design For Optimum Comfort And Visibility. The Three Sided Flat Visor Provides Peripheral Vision With The Shape Helping To Alleviate The Feelings Of Restriction. The Hood Can Be Easily Flat Packed For Stowage Without Creasing The Visor Whilst Allowing Rapid Removal From The Bag For Easy Donning. The Hood Is Fabricated From PVC Coated Materials With An Ozone Resistant Elastomeric Neck Seal.
8. Warning Whistle : The ELSA Features A Duration Whistle That Is Activated When The Air Is Depleted, Indicating That The CO2 Level Within The Hood Exceeds The Performance Specification.
9. The ELSA Bag : The Bag Is Fabricated From Either A High Visibility PVC Coated Material Or An Anti-static, Black Polyurethane Material. The Bag Allows For Quick Donning, Can Be Comfortably Carried In Two Orientations And May Be Used With An Optional Waist Belt. Velcro Strips Secure The Opening With Tamper Proof Tags Supplied To Prevent Unauthorised Access. A Transparent Window Is Provided To Allow The Cylinder Contents Gauge And Activation Pin To Be Inspected Without Opening The Bag.
10. In Any Case It Should Not Be Used For Fire Fighting Or Rescue Operations.

Donning Instructions For ELSA
1. Check The Pressure Gauge – The Needle Should Be In The Green Area (about 200 Bars).  Wear The Strap Around Your Neck With The Valve Towards Your Right Hand.
2. Put Your Left Hand Through The Strap.
3. Lift Flap And Remove Plastic Hood.  Turn On The Cylinder Valve, About Two Full Turns.
4. Pull Hood Over The Head.  
5. Breathe Normally And Proceed To Emergency Escape.
6. Like The Breathing Apparatus, They Can Also Be Charged On Board.  
7. Follow Manufacturer's Instructions For Maintenance Of The Equipment.    

Normally Four Types Of Portable Extinguishers Are Used On Board For Extinguishing A Fire:
1. Foam Extinguishers
2. CO2 Extingishers
3. Dry Chemical Powder (DCP) Extinguishers
4. Water Extinguishers

Q1. Explain The Procedure To Use Foam Extinguishers ?
Foam Extinguishers Are Particularly Useful For Extinguishing Fires Of Class 'B' Type Involving Inflammable Liquids.Foam Extinguishers Are Available In Two Types – 

Mechanical Foam Extinguisher
I) It Has A Plastic Bag Filled With Foam Concentrate Over A Gas Cartridge.
Ii) The Outer Container Contains Water.
Iii) When The Seal Is Pierced By Striking The Knob, The CO2 Is Released Thereby Rupturing The Plastic Bag.
Iv) The Water And The Foam Concentrate Are Mixed And The Foam Solution Is Driven By The Pressure Of Gas Up The Tube Into The Nozzle Where It Is Aerated Into Air Foam.
V) This Extinguisher Can Be Charged On Board. Separate Foam Concentrate Packets And Gas Cartridges Are Available Along With Instructions On How To Recharge The extinguisher. Ensure Foam Concentrates And Gas Cartridges Used Are Meant For That Size Of The Extinguisher.

Chemical Foam Extinguisher
I) This Type Contains Two Containers – One The Outer Container And The Other The Inner Container.
Ii) The Inner Container Has A Solution Of Aluminium Sulphate.
Iii) The Outer Container Has A Solution Of Sodium Bicarbonate.
Iv) The Extinguisher Is Always Placed In An Upright Position. 
V) To Prevent Any Accidental Mixing Of The Liquids In The Container, A Knob Is Attached To Sealing Lead Weight Which Is Kept Locked There By Closing The Opening Of The inner Container.
Vi) When The Extinguisher Is To Be Used, The Knob Is Turned To Open Position And  the Extinguisher Is Turned Upside Down Permitting Both The Solutions To Mix.  
Vii) A Chemical Reaction Is Set Up Which Produces Foam And Carbon Dioxide Gas.  The Chemical Foam Is Released Through The Nozzle Provided.

This Extinguisher Can Be Charged On Board As Follows :
I) After The Extinguisher Has Been Discharged, Open The Extinguisher From The Top Knob, Clean Both The Inner And The Outer Containers With Fresh Water.
Ii) The Charge For The Extinguishers Comes In Packets Containing Aluminium Sulphate And Sodium Bicarbonate Powders Clearly Marked "A" And "B".  Each Charge Has Both the Packets Needed For The Extinguisher.
Iii) A Note Giving Instructions On How To Fill Is Also Enclosed.
Iv) Fill Water In The Outer Container Till The Mark Provided In The Body Of The Extinguisher.  Empty The Measured Water Into A Clean Bucket.  Empty The Packet containing Sodium Bicarbonate Into That Bucket Of Water And Stir It Well Till All The Powder Has Dissolved.  Fill The Sodium Bicarbonate Solution Into The Outer container.
V) Similarly Measure The Water Required For The Inner Container, Dissolve The Aluminium Sulphate Powder And Fill The Inner Container With The Solution.
Vi) Place The Inner Container Inside The Extinguisher Body Taking Care That Both The Solutions Do Not Mix.
Vii) Screw In The Cap Having The Lead Sealing Weight And The Knob Should Be Turned To Close Position.
Viii) Now The Extinguisher Is Ready For Use.  The Extinguisher Should Be Kept Vertical And Should Be Placed In The Stand Provided For The Same.

Q2. What Are The Advantages Of Mechanical Foam Extinguishers Over Chemical Foam Extinguishers ?
Some Of The Advantages Of Mechanical Foam Extinguishers Over Chemical Foam Extinguishers
I) Mechanical Foam Extinguishers Can Be Operated Keeping The Extinguisher Upright Whereas Chemical Foam Extinguishers Have To Be Operated Keeping The Extinguisher inverted.
Ii) Since There Is No Chemical Reaction Taking Place In Mechanical Foam Extinguishers, They Are More Reliable And There Is No Delay Waiting For The Chemical Reaction to Build Up Pressure.  The Foam Comes Out Instantly.
Iii) They Are Easier To Recharge.
    
Note:
1. Foam Extinguishers Should Not Be Used On Electrical Fires.
2.When Using On Oil Fires, The Nozzle Should Not Be Directed Into The Fire As This Will Cause The Fire To Spread.  The Nozzle Should Be Directed On To A Bulkhead Above the Burning Surface To Permit The Foam To Build Up A Blanket Which Will Flow Over The Burning Liquid And Extinguish The Fire By Smothering.

Q3 What Check & Maintenance Is To Be Carried Out In Foam Type Fire Extinguishers?
I) At Least Once A Week, Clean The Exterior Body, Check Nozzle Outlet And Vent Holes And Ensure That The Plunger Is Clean And Fully Extended.
Ii) Every Quarter – Check The Internals, Gas Cartridge In Case Of Mechanical Foam, And Stir The Solutions In Both The Containers.  Ensure That There Are No Sediments.
Iii) Operate The Extinguisher Once Every Year At Fixed Shorter Intervals And Monitor Its Performance.  It Should Project The Foam To A Distance Of 6m For A Period Of 30 Seconds.
Iv) Pressure Test The Extinguisher Every 2 Years To Manufacturer's Stated Pressure (usually 17.5 Kgf/cm2 For 2.5 Minutes).

Q4. Explain The Procedure To Use Portable CO2 Fire Extingushers.?
I) Most Suitable For Fires Involving Electrical Appliances And Inflammable Liquid And In Places Where Foam, Water Or Dry Chemical Powder Can Damage The Equipment.
Ii) Carbon Dioxide Is Kept In Liquid Form At 50 Bars Pressure At About 15ºC.
Iii) The Top Of The Extinguisher Incorporates A Piercing Mechanism To Pierce The Seal When The Extinguisher Has To Be Used.
Iv) At The Outlet There Is A Flexible High-pressure Hose Attached To A Handle And A Discharging Horn.  
A Control Valve Controls The Discharge Of The CO2. This Is Locked In Position By Means Of A Safety Pin Which Is Removed Prior To Using The Extinguisher
V) When Handling The CO2 Extinguisher Care Must Be Taken To Hold The Hose Only At The Insulated Handle Provided For That Purpose.  In Case You Hold The Extinguisher At the Hose Or At The Discharging Horn, You Will Get Cold Burns As The Liquid Carbon Dioxide Expands To Gaseous State.
Vi) Similarly The Gas Should Not Be Directed On The Exposed Parts Of The Body As An Intense Cold Is Generated While The Gas Is Discharged.
Vii)Wear Proper Hand Gloves And Personal Clothing Like Full Sleeve Boiler Suit, Prior To Using The Extinguisher.
Viii) The Fire Is Extinguished By Sweeping The Discharge Horn Across The Surface Of The Burning Material.
Ix) The Fire Is Extinguished By Virtue Of CO2 Occupying The Air Space Thus Excluding Oxygen.  This Condition Starves The Fire And As CO2 Being Heavier Than Air Settles down Displacing The Air.

Q5. What Are The Main Drawbacks Of CO2 Type Extinguishers?
Some Drawbacks Of The Extinguisher
I) Though CO2 Is Non-toxic,but  it Can Suffocate A Person Near By And Being Heavier Than Air Will Settle Down.
Ii) If The Extinguisher Is Not Used Correctly It Could Cause Cold Burns.
Iii) Carbon Dioxide Issues Out A Dense Vapour, Which In Confined Spaces Would Impair Visibility.
Iv) The Sealing Disc Orifice May Freeze After The Initial Start There By Hindering The Flow Of Gas To The Discharging Horn.  In Such A Case Shut The Valve Or Release the Lever And Start Up Again.
V)This Extinguisher Cannot Be Recharged As Easily As The Foam Type On Board And Is Usually Recharged Ashore.

Q6. What Care & Maintence Is To Be Done In Co2 Type Extinguishers?
Care And Maintenance Co2 Type Extinguishers
I) Check That The Nozzle Outlet Is Free.
Ii) Ensure That The Safety Pin Is In Place And Secured And The Release Lever Is Not Depressed.
Iii) Weigh The Extinguisher At Least Once Every Month And If There Is A Reduction Of 10% Or More In Weight Then The Extinguisher Is To Be Recharged.
Iv) The Extinguisher Is To Be Pressure Tested Before Every Recharge.

Q7. Explain The Procedure To Use DCP Fire Extinguishers?
These Type Of Extinguishers  (usually Known As DCP Extinguishers) Are Suitable For Fighting Class B Fires Involving Inflammable Liquids And For Electrical Fires.
I)They Are Also Suitable For Class C And Class D Fires And To A Lesser Extent On Small Class A Fires.  
Ii) They Are Unsuited For Deep Seated Class A Fires As They Do Not Have The Cooling Effect.
Iii) The Dry Chemical Powder Used In These Extinguishers Comes In Varying Combinations Depending On The Purpose Of The Extinguisher For E.g. 
For Class A Fires – The Powder Is Usually Ammonium Phosphate Based.
For Class B Fires – The Powder Has A Potassium Bicarbonate Base
For Class D Fires – The Powder Is A Combination Of Sodium Potassium And Barium Chlorides
Iv) This Extinguisher Is Used Mainly For Class B Fires. The Base Is Usually Potassium Bicarbonate.  The Extinguisher Is Clearly Marked As To Which Class Of Fire It Is suitable For.
V) The Powder Interfering With The Chemical Chain Reactions Occurring In The Flames Extinguishes The Fire.  The Bicarbonate Decomposes Into Water And Carbon Dioxide.  This Decomposition Forms A Catalytically Active Surface, Which Destroys The Free Radicals Propagating The Flame Reactions.
Vi) The Extinguisher Body Contains A Receptacle Holding The Powder.
Vii) Attached To Cap Of The Extinguisher Top Is A Carbon Dioxide Cartridge, Which Is Screwed Into It And Has An Attached Piercing Mechanism.  Accidental Piercing Of The CO2 Cartridge Is Prevented By Means Of A Safety Pin, Which Should Only Be Removed When The Extinguisher Needs To Be Discharged
                    There Are Some Types Of DCP Extinguishers, Which Do Not Have A CO2 Cartridge, Instead The Extinguisher Receptacle Itself Is Pressurised Using CO2.  This Is Usually done Ashore And There Is A Pressure Gauge On The Extinguisher Where The Bottle Pressure Can Be Read Off.  The Charging Should Be Done As Per The Manufacturer's instructions.

Method Of Operation
I) Carry The Extinguisher To The Place Of Use.
Ii) Remove The Safety Pin And Strike The Knob Provided To Pierce The CO2 Gas Cartridge.
Iii) Direct The Stream Of Powder To The Base Of The Fire.
Iv)Progress Forward Moving The Nozzle Rapidly With A Side-to-side Sweeping Motion.
V) On Outdoor Locations Operate Extinguisher From Upwind Side Of Fire To Extend Effective Range Of Spray.

Q8. What Care & Maintenance Is To Be Done For DCP Type Extinguishers ?
Care And Maintenance
I) Check That The Nozzle And The Vent Holes Are Clear On A Weekly Basis.
Ii) Check That The Plunger Is Clean And Fully Extended.
Iii) Every 3 Months Check The Following :
           a)Weigh The CO2 Cartridge If Fitted And Replace It If It Is 90% Or Less Than Its Original Weight.
           b)The Piercing Mechanism Should Be Free.
           c)he Dry Chemical Powder Should Be Free Of Caking And Granulation.
Iv) Discharge The Extinguisher At Least Once A Year To Check Its Performance.  Extinguishers Can Be Discharged On A Rotation Basis.
V) If Unable To Discharge In Rotation, All Extinguishers Must Be Recharged After Every Two Years.

All DCP Extinguishers Should Be Sent Ashore To Be Pressure Tested Hydraulically Once In 3 Years.

Q9. Explain The Procedure To Use Patable Water Extinguishers ?
I) Water Extinguishers Are Most Suitable For Class "A" Fires I.e. Carbonaceous Fires In Accommodation Involving Wood, Paper And Furnishings.  In These Fires, The primary Purpose Is To Reduce The Temperature Of The Burning Material.Water Is Unsuitable For Fires Involving Burning Liquids Or Gases And Live Electrical Circuits.
Ii) Water Is The Extinguishing Media In These Extinguishers, Which Is Released In The Form Of A Jet By Means Of Gas Pressure In The Upper Part Of The Container.
Iii) The Gas Pressure Is Induced Either By Mechanical Means Or By Chemical Reaction.
Iv) In Water Type Extinguishers Where Gas Is Induced By Mechanical Means (commonly Called Water / CO2 Or The Universal Type) :
V) Water Is Stored In The Extinguisher Container And A CO2 Cartridge Is Attached To The Top Assembly.
Vi) When The Cartridge Is Pierced Open By Means Of The Plunger, CO2 Under Pressure Is Released.
Vii) This Increase In Pressure Causes The Water To Be Propelled Out With Pressure.
The Properties Of Water As A Fire-extinguishing Agent  are :

Q10. What Are The Advantages And Disadvantages Of Using Water For Fire Fighting?
Advantages
I) Water Is An Excellent Cooling Agent And Is Available In Large Quantities In The Form Of Sea Water.
Ii) It Absorbs More Heat For A Given Increase Of Temperature Than The Same Mass Of Almost Any Other Substance (It Has A High Thermal Capacity).
Iii) When Water Is Applied To Fire, It Is Converted Into Steam.  For This Steam To Form, A Great Deal Of Heat Is Extracted From The Fire, Assisting The Cooling process.
Iv) If Water At Near Freezing Temperature Is Used In Fire Fighting, Over Five Times As Much Heat Is Extracted In Converting The Water Into Steam Than Is Absorbed In the Process Of Raising The Temperature Of The Water From Freezing Point To Boiling Point.The Smothering Effect Of Steam Produced At The Seat Of Fire Assists In The Extinguishing Process
 
Disadvantages
I) Water In Copious Quantities May Have An Adverse Effect On The Ship's Stability.
Ii) When Used On Burning Oil, The Water Spray May Tend To Sink Under The Oil Thereby Causing The Fire To Erupt.
Iii)It Reacts Dangerously With Class D Substances.  Possibility Of Electric Shock If Used In A Straight Stream.  Also Reacts With Substances Such As Acids And carbides.
Iv) Sea Water Cannot Be Used On Electrical Fires As It Is A Good Conductor Of Electricity.
V)Water May Damage Electrical Equipment, Cargo Etc As It Soaks Them And May Make Them Beyond Use.

Q11. What Are The Check & Maintenance Involved In Water Type Extinguishers?
Care And Maintenance
I) On A Regular Basis (preferably Once A Week Or Fortnight) Check Nozzle Outlet And Vent Holes On Threaded Portion.
Ii) Check Whether The Plunger Is Fully Extended And Whether The Safety Pin Is In Place.
Iii) Every Three Months Dismantle The Cover Components, Check For Damage, Clean And Grease Them As Required (avoid Over Greasing), Stir The Solution In The Body (in case Of Chemical Reaction Type), Top Up The Water Quantity To Required Level.
Iv) Ensure That The CO2 Cartridge And Gas Phial Is Intact.
V) At Least Once A Year, Operate The Extinguisher To Ensure It Functions Properly.  It Must Produce A Jet Length Of 6 Mtrs For At Least 60 Seconds.
Vi) Pressure Test The Extinguisher Every Five Years As Per Manufacturer's Instructions (usually Done To 17.5 Kgf/cm2).
    
Q12. Explain The Procedure To Use Patable Water Extinguishers ?
The "Soda / Acid" Type Extinguisher Are No Longer In Use. The Information Has Been Provided Here Only As A Matter Of Interest.
I) In The Water Type Extinguisher Where The Gas Is Induced By A Chemical Reaction (this Type Is Commonly Known As The Soda/Acid Type):
Ii) The Container Of The Extinguisher Is Filled With Sodium Bicarbonate Solution (NaHCO3).
Iii) Near The Cap Of The Extinguisher Is A Glass Phial Containing Sulphuric Acid.
Iv) The Plunger Pierces The Glass Phial And The Sulphuric Acid Is Made To React Chemically With The Sodium Bicarbonate Solution.
V) The Reaction Produces Carbon Dioxide, Which Pressurises The Liquid Out Of The Extinguisher.
Vi) The Reaction Between Sulphuric Acid And Sodium Bicarbonate Is As Follows :
H2SO4          +         2 NaHCO3              =     Na2SO4  +  2 H2O  +  2 CO2
(Sulphuric Acid + Sodium Bicarbonate)      =     (Sodium Sulphate + Water + Carbon-dioxide )

Vii) The Water Thus Formed In The Above Chemical Reaction Is The Actual Extinguishing Agent Where As The Carbon Dioxide Acts As The Propelling Agent.
Viii) Both Type Of Extinguishers Are Normally Operated In The Upright Position By Striking The Knob To Either Pierce The Acid Bottle Or The Carbon Dioxide Seal, But there Are Some Soda / Acid Type Extinguishers Which Are Operated Upside Down.
Ix) The Gas Cartridge Type Is More Efficient And Is More Easily Recharged.
        
Method Of Operation
I) Ascertain Whether The Extinguisher Is The Upright Type Or The Turn Over Type.
Ii) Remove The Safety Pin And The Guard Cap And Strike The Plunger Piercing The Seal Or The Acid Phial.
Iii) Direct The Jet Emerging From The Nozzle To The Base Of The Fire, Keeping It Directed There Till The Extinguisher Is Completely Discharged.

Precaution Must Be Taken While Starting And Taking Generators On Load To Ensure Safety Of Machinary. Engineer Officers Must Follow The Manufacture's Instructions Given For The Operation And Maintenace Of The Machinaries. Here Are Some Basic Information Which Can Help Them In Starting And Taking Generators On Load.

Q1. How To Start A Generator?
Preparation Before Starting
A) Check That The Turning Bar Is In Place.
B) Check That The Starting Air Valve, Diesel Oil Inlet And Outlet Valves Are Open. Ensure That The Heavy Oil Inlet And Outlet Valves Are Shut. ( In Modern Generator Starting On HFO Is Also Possible)
C) Check That The Lube Oil Priming Pump Is On AUTO And Ensure That It Is Running. The Lube Oil Pressure At The Gauge Should Show Above 1.0 Kg/cm2.
D) Change Over The AUTO / MANUAL Switch Located At The Engine To MANUAL.
E) Check That All The Fuel Pump Racks Are Free.
F) Check Lube Oil Levels For The Sump, Turbocharger And The Governor Are Normal.
A) Open All Indicator Cocks. Pull Down The Fuel Lever And Lock It At The Zero Position. Blow Through The Engine.
B) Close All Indicator Cocks.
C) Move The Fuel Lever To Mid Position And Give An Air Kick With The Starting Air Lever And Release It When The Engine Fires On Fuel.
D) Increase The Fuel To The Engine Gradually. Once The Rated RPM Is Reached, The Governor Takes Over. Lock The Fuel Lever At The Maximum Fuel Position. 
E) Change Over The AUTO / MANUAL Switch To AUTO. Exhaust Pipe Leakage Should Be Checked At Regular Intervals To Avoid Chances Of Fire.

Q2.  What Checks You Should Do After Starting An A/E ?

After Starting The Generator Check The Following:
A) Check That All Lube Oil And Cooling Water Pressures Are Normal. The Lube Oil Priming Pump Must Stop Once The Engine Has Reached The Rated RPM.
B) Check The Oil Flow For The Pedestal Bearings For The Alternator.
C) Check That All Units Are Firing And The Exhaust Gas Temperatures Are Rising Evenly For All Units.
D) Ensure That There Is No Abnormal Sound / Vibrations From The Engine, Turbocharger And Alternator.
E) Check The Rocker Arm Lubrication And Ensure That The Valve Rotators For The Inlet And Exhaust Valves Are Turning.
F) Check That There Are No Oil, Water And Exhaust Gas Leaks.
G) Check The Voltage And Frequency For The Generator At The MSBD (Main Switch Board).
H) Check That There Should Not Be Any Abnormal Souding( Mechanical Knocking Etc.)

Q3. How To Take A/E On Load?

Putting The Engine On Load  (Parallel Operation)
A) Ensure Same Voltage  reading For Main Bus Bar & Incoming Generator
B) Ensure Same Frequency Of Main Bus Bar & Incoming Generator.
C) Put The Selector Switch For The Synchroscope (located At The MSBD) To The Incoming Generator.
D) Adjust The Frequency For The Incoming Generator Such That The Synchroscope Pointer Turns Slowly In FAST (clockwise) Direction By Operating The Governor Control Lever.
E) Change Over The CONTROL MODE Switch To Manual.
F) Pull Out The Air Circuit Breaker (ACB) Control Lever And Close The ACB When The Synchroscope Pointer Is At The 11-O`clock Position.
G) Increase The Load On The Incoming Generator By Operating The Governor Control In The Raise Direct
H) Share The Load Between The Generators As Required.

Q4. How To Off Load A Generator From Parallel Operation?
When The Need For Having Two Generators In Parallel Operation Is No More, One Of The Generators Can Be Stopped. Before Transferring The Load To The Generator That Is Going To Continue, Check To Ensure That Operating Parameters And Condition Is Normal For It To Take All The Load And Such That The Total Load Will Be Within The Safe Limits (leaving Allowance For Loads Of Air Compressor, Fire Pump, Feed Pump, Etc).
        By Gradually Reducing The Load Through The Governor Control Switch On The Outgoing Generator And Increasing The Same On The Other, Load Will Shift. When Close To No-load Condition, The Generator To Be Stopped Can Be Tripped Manually Or On Further Reduction Of Load, It Will Trip Automatically.
          If Required, Adjust The Frequency Of The Generator On Load. For About, 15 Minutes, Observe That The Performance Of The Generator Is Normal. Stop The Idle Generator Engine And Maintain The System On Auto-start Or Otherwise Follow The Procedures Stipulated On Your Ship.

Cylinder Head 
The individual cast-iron cylinder heads, one for each cylinder unit, are equipped with a centrally situated fuel injection valve, two inlet valves, two exhaust valves and one indicator cock. The head has a thick, bore-cooled flame plate for satisfactory control of mechanical and thermal loads and stress. The cylinder head is attached by means of 4nuts and 4 studs screwed into deep bosses in the engine frame top plate. The nuts are tightened by means of hydraulic tools. 

Inlet and Exhaust Valves 
The valve spindles are made of heat resistant material. Hard metal is welded on to the valve spindle seats. The valve spindles are fitted with valve rotators which turn the spindles a little each time the valves open. The cylinder head is equipped with replaceable seat rings for inlet and exhaust valves. The seating surfaces are hardened in order to minimize wear and prevent dent marks, on the inlet seat by induction hardening, on the exhaust seat by hard metal armouring. 

Piston 
The piston, which is oil-cooled and of the monobloc type made of nodular cast iron, is equipped with 3 compression rings and 1 scraper ring. By use of a combination of compression rings with different barrel-shaped profiles and chrome-plated running surface on all rings, the piston ring pack is optimized for maximum sealing effect and minimum wear rate. The piston has a cooling oil space close to the piston crown and the piston ring zone. The heat transport, and thus the cooling effect are based on the shaker effect arising during the piston movement. Oil from the engine's lubricating oil system is used as cooling oil. The piston is provided with a turned edge at the top due to the flame ring mounted in the cylinder liner. 

Piston Pin 
The piston pin is fully floating which means that it can turn freely in the pin bosses of the piston as well as in the connecting rod bush. The piston pin is tumed in place upwards in axial direction by two circlips (seeger rings). 
 
Connecting Rod  
The connecting rod is die-forged. The big-end has an inclined joint in order to facilitate the piston and connecting rod assembly to be withdrawn up       through the cylinder liner. The joint faces on the connecting rod and the bearing cap are serrated to ensure precise location and to prevent relative movement of the parts. The big-end bearing is of the trimetal type, i.e. steel  shells lined with tin-aluminium or lead-bronze coated with a running layer. Designed as plain type or rillentype. The bearing shells are of the precision type and are therefore to befitted without scraping or any other kind of adaption. The small-end bearing is of the trimetal type and is pressed into the connecting rod. 

Cylinder Liner 
The Cylinder liner is made of fine-grained, pearlite cast iron and is fitted in a bore in the engine frame. Replaceable cast iron sealing rings are fitted between the liner and the cylinder head and between the liner and the frame. The liner is clamped by the cylinder head and is guided by a bore at the bottom of the cooling water space of the engine frame. The liner can thus expand freely downwards, when heated during the running of the engine. Sealing for the cooling water is obtained by means of silicone rubber rings which are fitted in grooves machined in the liner. The cylinder liner is of the so caIIed "stepped cylinder” type, provided with flame ring inserted in the top of the liner. 

Camshaft 
The camshaft which controls the actuation of inlet valves, exhaust valves and fuel injection pumps is driven by a gear wheel on the crankshaft through an intermediate wheel, and rotated by a speed which is half of that of the crankshaft. The camshaft is located in a high level housing in the engine frame. The camshaft runs in replaceable, identical, steel-backed bronze bushings fitted into borings of the transverse girders in the housing. The camshaft is built-up of sections, one for each cylinder unit. Each section is equipped with fixed cams for operation of fuel injection pump, air inlet  
valve and exhaust valve. The sections are assembled by bolting of the ample dimensioned and precision made flange connections, which also act as bearing journals. Except for the foremost and the aftmost ones: the sections are identical and therefore interchangeable. The foremost section is equipped with a clutch for driving the fuel oil feed pump (if mounted). The gear wheel for driving the camshaft as well as a gearwheel connection of governor are screwed on the aftmost section. The lubricating oil pipes for the gear wheels are equipped with nozzles which are adjusted to apply the oil at the points where the gear wheels are in mesh. The position of the holes is determined by direction of rotation of the engine. 

Roller Guides 
The fuel injection pumps and the rocker aims for inlet and exhaust valves are operated by the cams, on the camshaft through roller guides. The roller guides for fuel pump, inlet and exhaust valves are located in bores in a common housing for each cylinder, this housing is bolted to the engine frame. The roller runs on a bush fitted on a pin that is pressed into the roller guide and secured by means of a lock screw.

Operating Gear for Fuel Injection Pumps 
The injection pumps which are mounted directly on the roller guide housing are activated via thrust pieces from the roller guide. The roller is pressed down on to the cam by a spring, which is fixed between the roller guide and the foot plate of the fuel injection pump. 

Operating Gear for Inlet and Exhaust Valves 
The movement from the roller guides for inlet and exhaust is transmitted via the push rods the rocker arms and spring-loaded valve bridges to each of the two valve seats. The bridge is placed between the valve spindles and in the one end it is provided with a pressed-on thrust shoe and in the other end it is fitted with a thrust screw for adjustment of the valve clearance. On its top the bridge is controlled by a spherical thrust shoe on the rocker arm and at the bottom by a guide which rests in a spherical socket in the cylinder head. 

Governor 
The engine speed is controlled by a hydraulic governor. The purpose of the governor is to regulate the rate of delivery from the fuel pumps, so that the engine speed is kept within certain limits, in depending on the load. The governor is mounted on the flywheel end of the engine and is driven from the camshaft via a cylindrical gear wheel and a set of bevel gears. 

Pick-up for Engine RPM  
The pick-up for transfer of signal to the tachometer instrument for engine RPM is mounted on the flywheel end cover of the engine. A signal varying proportionally to engine RPM is created in the pick-up by the rotating toothed impulse wheel mounted on the camshaft end. 

Regulating Shaft 
The governor movements are transmitted through a spring-loaded pull rod to the fuel pump regulating shaft which is fitted along the engine. The spring-loaded pull rod permits the governor to give full deflection even if the stop cylinder of the manoeuvreing system keeps the fuel pump regulating shaft at “no fuel” position. Each fuel pump is connected to the common, longitudinal regulating shaft by means of a two-piece, spring-loaded arm. Should a fuel pump plunger seize in its barrel, thus blocking the regulating guide, governing of the remaining fuel pumps may continue unimpeded owing to the spring-loaded linkage between the blocked pump and the regulating shaft. 
Stop Screw for Max. Delivery Rate 
The bracket for stop cylinder/limting cylinder is fitted with a stop screw which prevents the fuel pumps from being set to a higher delivery rate than what corresponds to the permissible overload rating. This is effected by the arm on the regulating shaft being stopped by the stop screw. 

Mechanical Overspeed 
The engine is protected against overspeeding in the event of for instance, governor failure by means of an overspeed trip. The engine is equipped with a stopping device which starts to operate if the maximum permissible revolution number is exceeded. The overspeed tipping device is fitted to the end cover of the lubricating oil pump and is driven through this 

Q.1 What Is The Purpose Of Main Engine Fresh Water Cooling System?
Ans: Main Engine Fresh Water Cooling System Has Very Significant Functions As Combustion Of Fuels And Friction Between Moving Parts Gives Rise To The Temperature Of Components Of The Engine.
 
Q.2 Descibe The Components Of Fresh Water Cooling System?
Ans Here Is A Pictorial Representation Of Fresh Water Cooling System.  
As You Can See In The Diagram Above, The Primary Components Are As Follows:

i) Header Tank/ Expansion Tank:  The Expansion Tank Is A Water Storage Tank, Provided At Maximum Height Possible Such That A Constant Head Is Maintained On The System. Any Loss Of Water Through Leakage Etc Are Maintained By This Tank. It Is Also Known As Make Up Water Tank.

iii) Cooler: The Water Which Enters The Main Engine To Cool It, In Return Becomes Hot. Thus A Cooler Is Required To Cool  it And Make It Ready For Use Again. The Cooler Can Be Sea Water Cooler Or Fresh Water Cooler, Depending On The Medium Used As Cooling System On Ship. Most Of The New Ships Are Central Cooling Systems And Use Fresh Water As A Cooling Medium.

iii) Circulating Pump: The Circulating Pump Is A Centrifugal Pump, Generally Called As Jacket Water Circulating Pump Onboard. This Pumps The Water Cooled From Cooler Into The System Towards Main Engine. Generally The Discharge Pressure Is 2-3 Bar.

iv) Pre-Heater: A Pre-Heater Is Provided Such That Water Is Maintained At Around 60-65 Deg Celsius. If Temperature Is Found To Be More, Cooling Water Is Bypassed Through The Pre Heater. It Happens Generally In The Colder Regions Or When The Ship Is In Port, Main Engine Is Not Getting Heated Up And Fresh Water Generator Is Also Not Working. Hence The Water Coming From Cooler Is Colder And Needs To Be Heated Up. So When At Port, Engine Staff Opens The Pre Heat Steam, To Maintain The Main Engine Jacket Temperature Around 80-85 Deg Celcius. 

v) Air Separator/ De-Aearator: It Is An Important Component In The System As It Removes The Air Formed/ Accumulated In The System, This Happens Due To Heating Up Of Water. Oxygen Tends To Evolve From The Boiling Process, If It Is Not Removed, An Air Lock In Then System Is Likely To Happen.

vi) Fresh Water Generator: Fresh Water Generator Acts A Cooling Component, Which Cools The Heated Up Water From Main Engine Through Its Evaporator, Which Basically Is A Plate Type Heat Exchanger. The Cooling Medium Which Is Sea Water Takes Up The Heat And In Turn Gets Heated Up.

Q.3 What Are The Conditions Which Arise Due To Lack Of Cooling?
Ans: Following Are The Conditions Which Arise Due To Lack Of Cooling,
I) Expansion Of Components Reduces Clearance Between Moving Parts Causing The Following. 

Ii) Restriction To The Flow Of Lubricating Oil:
Reduction In Cooling Effect, And Increase In Frictional Drag Due To Loss Of Lubricant Film. The Above In Turn Lead To Further Rise In Temperatures And Further Expansion Of Components Thereby Worsening The Operating Conditions.

Iii) Chances Of Seizure Due To Reduction In Working Clearances, And Due To Changes In Shape Of Components With Limited Allowances For Expansion. Changes In The Shape Of Components, Such As, Pistons And Cylinder Liners Lead To A Loss Of Sealing Between Parts For Compression And For Retention Of Exhaust Products With The Combustion Space.

Iv) Stresses Increase When Components, Such As, Cylinder Heads, Cylinder Blocks Cannot Expand Freely.

Q.4 Why And Where Water Is Prefered As A Coolant Instead Of Lubricating Oil?
Ans:  As Compared To Lubricating Oils, Water Has Negligible Effect On Frictional Drag Between Two Components In Contact And It Does Not, On Its Own, Prevent Corrosion Of Components. 
          Thus, Water Is Used Where Only Cooling Is Desired And Lubricating Oil Is Used Where Cooling, Reduction In Frictional Drag, And Prevention Against Corrosion Is Required. 
 
Cooling Water Is Used For Cooling Cylinders Liners, Cylinder Cover, Exhaust Valve And In Some Cases Pistons Of The Engine.

Question: What Is A Fresh Water Generator? What Is Its Purpose Onboard?
Answer: A Fresh Water Generator Is Equipment Used Onboard For Production Of Fresh Water From Sea Water. It Also Serves The Purpose Of Cooling The Hot Jacket Cooling Water At Around 85 Deg Celsius To 65 Deg Celsius. Generally The FWG Is Stopped, When Engine Attains Maneuvering Rpm, Because Further Cooling Of Jacket Water Is Not Required.
        A Fresh Water Generator Uses The Heat Of Jacket Cooling Water Of The Main Diesel Engine To Evaporate The Sea Water Under High Vacuum, Through The Bilge Of The Separator, The Brine Is Separated From The Vapor, And Then The Separated Vapor  Enter Into The Condenser Where They Are Condensed By The Cooling Sea Water In The Condensable Tube. By The Means Of The Salinometer, The Condensed Is Sent To The Fresh Water Tank When It’s Salt Content Is Less Than The Settled Value, Otherwise, It Is Sent Back To The Heat Exchanger To Evaporate Again.
In Addition, As The Fresh Water Generator Is Fitted With A Steam Ejector At Option, It Can Also Produce The Fresh Water Based On The Steam Of The Auxiliary Boiler When The Ship Berths At Dock And The Main Diesel Engine Stops Working.

Q. Explain The Working Principal Of FWG?
Ans: The Major Factor That Makes FWG Effective Is Evaporation And Condensation Of Water At Lesser Temperature, This Reduction In Saturation Temp. For Vaporisation And Condensation Is Due To Reduction In Saturation Pressure By Generating Vacuum Within The Chamber. It Is Generated By The Help Of An Air Ejector, Which Extracts The Air From The Chambers. An Air Ejector Works On Bernoulli's Principle And Continuity Equation. Heated Jacket Water At Around 85 Deg Celsius Enters The Evaporator And Transfers Its Heat To Cold Sea Water Supplied By The Ejector Pump. The Sea Water Flashes Off At Lesser Temperature And Pressure Due To Reduction In Its Saturation Pressure In Presence Of Vacuum. This Flash-off Water Vapour Passes Through Demister Plate Which Restrict The Passage Of Wet Vapour. This Water Vapour Now Reaches Into Condenser Chamber, Here Also The Sea Water Supplied By Ejector Pump Is Used To Condense The Water Vapour, Due To Reduction In Saturation Point, The Reduction In Condensation Temperature Also Take Place And Condensation Takes Place .The Condensed Water Passes Through A Salinometer Which Measures The Ppm Of Salt Present In Water. If It Is More Than 1-2 Ppm It Is Passed Back To Evaporator Chamber. Otherwise It Passed Towards Distillate Pump Via The Chemical Dosing Tank, Where Vaptreat Is Added At Regular Intervals To Remove Impurities. Distillate Pump, Pumps It Out Of The Fresh Water Generator And Is Passed To The Fresh Water Storage Tanks.

What Is Purpose Of Fitting FWG On The Ship?
Purpose Of FWG On Board
1. Production Of Fresh Water From Sea Water For Human Consumption With A Quality Demand Equal To World Health Organization (WHO).
2. Produce Fresh Water In Ample Flow For The Daily Demand.
3. To Make The Ship Independent Of Water Supply From Source Of Water Of Unknown Quality.
4. To Produce Fresh Water At Lowest Costs, As The FWG Unit Utilizes The Waste Heat From The Engine Jacket Cooling Water.
 
Explain General Working Principle Of A FWG?
A Controlled Amount Of Sea Feed Water Is Led To The Inside Of The Heat Exchanger Tubes, Where It Is Heated By The Surrounding Engine Jacket Cooling Water (Or From The Other Heat Sources). The Sea Feed Water Evaporates Under Vacuum To Reduce The Evaporation Temperature, Thus Avoiding Scale Formation Inside The Tubes.
The Generated Vapour Pass To The Separation Compartment Where The Sea Water Drops Are Separated As Brine.
The Dry Fresh Water Vapours Raise To The Condenser, In Which The Tubes Are Cooled Inside By Water, There They Are Condensed Outside The Tubes And By Gravity Is Falling To The Collecting Shell Of The Condenser  And Flows To The Suction Pipe Of The Fresh Water Pump.

Briefly Explain The Function Of All The Parts/equipments Found In FWG System?
Ejector Pump:
It Is A Normal Centrifugal Pump Which Supplies The Necessary Service Water To The Ejector And The Preheated Sea Feed Water To The Heat Exchanger.

Sea Feed Water System:
By Means Of The Correct Ejector Pump Pressure And An Orifice, The Correct And Controlled Amount Of Sea Feed Water Is Supplied To The Plant.The Spring Loaded Diaphragm Valve Secures That The Plant Is Not Flooded With Sea Water When  It Is Out Of Service.

Heat Exchanger:
It Exchanges The Latent Heat In Engine Jacket Cooling Water (Or From Other Heat Sources) To The Sea Feed Water.
Separator: A Deflector Plate Secures That No Sea Water Drops Pass On To The Condenser, As The Excess Of Boiling Feed Water From The Heat Exchanger Tubes Is Hold Back Drained Off. The Brine Accumulated In The Bilge Of The Separator Where It Is Led To The Brine Ejector.

Brine Ejector:
It Takes Out All Excess Of Sea Feed Water (Brine) And Secures That The Separator Is Not Flooded.

Air Ejector:
It Evacuates The Plant And Takes Out Continuously The Air Gases As To Maintain A Low Evaporation Temperature.

Condenser:
It Exchanges The Latent Heat In The Produced Fresh Vapours To The Cooling Water So That The Vapours Are Condensed And Accumulated In The Bottom Of The Condenser ‘s Shell.

Fresh Water Pump/Distillate Pump
It Is A Normal Centrifugal Pump Which Draws Out The Produced Fresh Water And Pumps It Into The Storage Tanks Of The Ship.
Salinometer System And Flow Meter: By Means Of An Ejector, A Salinometer, And Solenoid Valve, Produced Fresh Water With Too High Sea Salt Content Will Be Led Back To The Feed Water System.The Flow Meter Indicates The Accumulated Fresh Water Produced.

Q. What Are The Safeties In A FWG?
Ans: Safeties In A FWG Are: 
1. Vacuum Breaker For Releasing The Vacuum At The Time Of Shutting Down. 
2. Relief Valve For Releasing The Excess Pressure. 
3. High Salinity Alarm: It Is Fitted To The Salinometer As It Measures Higher Salt Content In The Water Produced, It Sounds The Alarm. 
4. Temperature Guage.

Q. Where Does The Ejector Pump Takes Suction From, What If Ejector Pump Fails And We Have To Run FWG?
Ans: Ejector Pump Has A Separate Sea Water Suction I.e. A Separate Sea Chest. In Case The Ejector Pump Fails And We Need To Run The FWG, There Is A Separate Line From Fire And General Service Pump As The Discharge Pressure Of This Pump Is Around 3-4 Bar And Ejector Pump Discharges At Pressure Not Less Than 4 Bar. Main Sea Water Cannot Be Used In This Case Because Msw Pump Has Discharge Pressure Around 1-2 Bar.

The Function Of A Ship's Electrical Distribution System Is To Safely Convey The Generated Electrical Power To Every Item Of Consumer Equipment Connected To It. Probably The Most Obvious Element In The System Is The Main Distribution Centre, I.e. The Ship's Main Switchboard. The Main Board Supplies Bulk Power To Motor Group Starter Boards (often Part Of The Main Board), Section Boards And Distribution Boards. Protection, E.g. Circuit-breakers And Fuses, Strategically Placed Throughout The System Automatically Disconnects A Faulty Circuit Within The Network. Transformers Interconnect The High Voltage And Low Voltage Distribution Sections Of The System.

The Operational State Of A Distribution System Is Indicated By The Monitors For Power, Voltage, Current And By Protection Relays For Over Currents And Earth-faults At Each Main Control Centre. Study The Electrical Power Diagrams For Your Own Ship To See If You Can Relate Them To The Actual Equipment They Represent.
 
The Vast Majority Of Ships Have An Alternating Current (a.c.) Distribution System In Preference To A Direct Current (d.c.) System.
 
The Required Electrical Services Are Broadly Considered As Main And Emergency Supplies.

The Ship's 'Electrical Distribution System For Ships' Is Called A Radial Or Branching System. This Distribution System Has A Simple And Logical Structure. Each Item Of Load Is Supplied At Its Rated Voltage Via The Correct Size Of Cable And Is Protected By The Correctly Rated Protection Device.

Q1. Why A.C  network Is Installed On Ship? Also Explain What A.C System Is Used On Board?
An A.c. Network Is Cheaper To Install And Operate Than A D.c. System. In Particular A.c. Offers A Higher Power / Weight Ratio For The Generation Distribution And Utilisation Of Electricity. Simple Transformers Efficiently Step-up Or Step-down A.c. Voltages Where Required. Three-phase A.c. Is Effectively Converted Into Rotary Mechanical Power In Simple And Efficient Induction Motors.
 
The Majority Of Ships Have A 3-phase A.c., 3-wire, 440 V Insulated-neutral System. This Means That The Neutral Point Of Star-connected Generators Is Not Earthed To The Ship's Hull. For Continental European Vessels, A 380 V, 3-phase System Is Common.

Ships With Very Large Electrical Loads Have Generators Operating At High Voltages (HV) Of 3.3 KV, 6.6 KV And Even 11 KV.  where Equipment Weight Saving Is Important. Distribution Systems At These High Voltages Usually Have Their Neutral Points Earthed Through A Resistor Or Earthing Transformed To The Ship's Hull.

Q2. What Frequency Is Used On Board ? Also Explain How Low Power Supply Is Achived.
The Most Common Power Frequency Adopted For Use On Board Ships And Offshore Platforms Is 60 Hz. This Higher Frequency Means That Motors And Generators Run At Higher Speeds With A Consequent Reduction In Size For A Given Power Rating.

Lighting And Low Power Single-phase Supplies Usually Operate At The Lower Voltage Of 220 V A.c. Although 110 V A.c. Is Also Used. These Voltages Are Derived From Step-down Transformers Connected To The 440 V System.

Q3. What Do You Mean By Distribution System?
The Distribution System Is The Means By Which The Electrical Power Produced By The Generators Is Delivered To The Various Motors, Lighting, Galley Services, Navigation Aids, Etc. Which Comprise The Ship's Electrical Load.

Q4 How Electricity Is Routed To Final Load?
The Electrical Energy Is Routed Through The Main Switchboard, Then Distributed Via Cables To Section And Distribution Boards Then Ultimately To The Final Load Consumers.

Q5 What Are The Protection Provided In The Electrical System?
The Circuit-breakers And Switches Are The Means Of Interrupting The Flow Of Electric Current, And The Fuses And Relays Protect The Distribution System From The Damaging Effects Of Large Fault Currents.

What Do You Mean By A Pump?
A Pump Is A Device That Transfers Energy To A Fluid Passing Through It. In Practice, Pumps Change Both The Velocity And The Pressure Of The Fluid Passing Through It, The Ratio Of These Energy Changes Depends Upon The Type And The Speed Of The Pump In Use. 

What Are The Main Types Of Pumps?
Main Types Of Pumps
1. Displacement Pumps
2. Kinetic Pumps

What Do You Mean By Displacement Pump? Also Briefly Explain Types Of Displacement Pump.
1. Displacement Pumps
In Displacement Pumps The Volume Of The Pump Chamber Is Alternately Increased To Draw The Liquid In (suction) And Then Decreased To Force The Liquid Out (delivery). This Is Done By A Reciprocating Motion Of A Piston Or Plunger Within A Cylinder, Or By A Rotary Motion Of Specially Designed Vanes, Gears Or Rotors. 
Positive Displacement Are Provided Fitted With Relief Valve Safeguard The System

Types Of Displacement Pump?
i) Reciprocating Pump: A Reciprocating Pump Has 'to And Fro' Motion Provided By A Direct Acting Steam Driven Piston, Or Through Mechanisms That  convent Rotary Motion To Reciprocating Motion (e.g. Cranks, Eccentrics Etc.).Due To Fluctuating Motion Of The Piston, The Delivery And Pressure Is Not Steady. To Improve The Overall Performance, The Pump Is Arranged As Double Acting And Fitted With An Accumulator (air Vessel) On The Discharge Side Of The Pump To Achieve A Near Steady Pressure. 
Reciprocating Type Pumps Are Suitable For Delivering Smaller Quantities Of Liquids At High Pressures. They Are Self-priming And Can Handle High Suction Lifts. However Their Construction Is Complicated And Uneconomical Except For Limited Applications E.g. Bilge Pumps, Stripping Pumps, Etc.

ii) Rotary Pumps
 Rotary Types Of Displacement Pumps Are Commonly Used On Board Ships In Place Of Reciprocating Pumps.
A Rotary Pump Continuously Scoops The Fluid From The Pump Chamber By Means Of Gears Or Screws, Or Vanes Etc. When Rotated, Liquid Gets Trapped In Small Pockets Created By The Moving Element And It Gets Transferred From The Suction Side To The Delivery Side.

Types Of Rotary Pumps

a) A Gear Pump Has Intermeshing Gears Or Lobed Members Enclosed In A Suitably Shaped Housing. The Efficient Of These Pumps Depends Upon The Accuracy With Which The Component Parts Are Machined And Fitted I.e. Working Clearances. Gear Pump Is The Simplest Type Of Positive Delivery Pumps And Most Commonly Used On Board Ship For Handling Small Quantities Of Fluids -usually Oils, E.g. Lubricating Oil Transfer Pumps, Auxiliary Diesel Engine Lubricating Oil Pump, Oil Separator Pumps Etc. Delivery Rate Depends Directly Upon The Speed Of The Pump. 

B) A Lobe-pump Like A Gear Pump And Was The Earlier Type Of Mechanical Pumps Used For Supercharging Of Main Engine. Now You Will Find It Being Used A Sewage Pump.

C) A Vane Type Pump Operation Is Also Based On The Principle Of Increasing The Size Of The Cavity To Form A Vacuum, Allowing The Space To Fill With The Incoming Liquid, And Then Forcing The Fluid Out Of The Pump Under, Pressure By Diminishing The Volume.

        The Sliding Vanes Or Blades Fit Into The Slots In The Rotor. Ahead Of The Slots And In The Direction Of Rotation, Grooves Admit The Liquid Being Pumped By The Vanes, Moving Them Outward With A Force Of 'locking Pressure That Varies Directly With The Pressure That The Pump Is Operating Against. The Grooves Also Serve To Break The Vacuum On The Admission Side. The Operating Cycle And The Action Of Centrifugal Force And Hydraulic Pressure Hold The Vanes In Contact With The Casing. 
       This Type Of Pumps Are Most Suitable For Variable Displacement Requirement E .g. Hydraulic Steering System, Hydraulic Winches Etc. 

iii) Screw Pump: It Is Most Suitable For Viscous Fluids And Is Commonly Used For Medium To Heavy Duty Requirements. (e.g. Main Engine Lubricating Oil Pump, Cargo Pumps, Oil Transfer Pumps Etc.  Screw Pumps Are Broadly Classified By The Number Of Screw Rotors Employed E.g.   

Types Of Screw Pump
a) Single-screw– Rotating Within A Accurately Bored Cylinder -mono-pumps As Commonly Known For Marine Application Has One Power Rotor Within A Semi-flexible Stator, And This Type Can Handle Highly Abrasive Liquids And Can Also Pump Liquids Containing Fairly Large Solid Particles.
b) Two-screw– Either With Intermeshing Contact, Or Separately Driven And Synchronised To Run With Positive Clearance.  
C) Three-screw -with Three Screw On Parallel Axis. The Central Screw Is Power Driven And Drives Two Outer Idler Screws. The Assembly Of Three Screws Is Usually Supplied In A Single Element.     

What Do You Mean By Kinetic Pumps (Roto-dynamic)?
Centrifugal Pumps Are Most Common Type Of Pumps On Board Ships. Almost All Of The Pumps On Board For Seawater Or Fresh Water Are Of Centrifugal Type. They Come In Various Sizes And Arrangements Of Flow And Stages And Design Of Impellers And Casings.
Flow: Radial, Mixed, Or Axial 
Stage: Single Stage, Multiple Stage
Impellers: Open Or Closed Impellers
Drive: Horizontal Or Vertical Drive.
On Some Ships, Even The Main Engine Lubricating Oil Pump Is Of Vertical Centrifugal Type Located Within The Oil Sump And Driven By Electric Motor Above The Tank Top. These Pumps Are Called Submersed Type Pumps.

Explain Operating Procedures For Displacement Pumps?
Starting:  
Precaution: Never Start A Displacement Pump Without Ensuring That All Valves On The Discharge Line Are Open.  
1. Attempt To Turn The Pump Shaft Manually To Ensure It Is Not Seized.  
2. Ensure That The Cocks To The Pressure Gauges Are In Line For Indicating The Pressure And Not Open To The Atmosphere.  
3. Open Appropriate Valves On The Discharge Side Where The Liquid Has To Go. 
4. Open Appropriate Valves On The Suction Side. 
5. When Provided With A Manually Controlled Valve (bypass) To Regulate Pressure, Release The Spring Load To Start The Pump At A Reduced Load. 
6. Start The Pump And Observe For Abnormal Sounds, Load On The Motor, Or Excessive Pressure Build Up. (stop The Pump Immediately In Case Of Any Abnormality) 
7. If The Liquid Being Drawn Is From A Distant Tank Below The Level Of The Pump, The Pump Will Take Some Time To Draw The Liquid. There Will Be A Change In The Running Sound When The Liquid Reaches The Pump. If The Liquid Is Cold The Pump Is Likely To Vibrate And Cause An Abnormal Noise.  
8. Observe Pressure As The Pump Picks Up Liquid. Adjust Pressure Regulating Valve To Increase The Discharge Pressure To Normal. Observe Leakages At Pump Gland, Valves, And Along The Pipeline. 
9. Incase The Pump Is Having Difficulty In Drawing The Liquid. Stop The Pump And Check Suction Filter. Clean If Necessary. Heat The Liquid In Tank If The Temperature Is Low. 

Stopping The Pump: 
1. Stop The Motor. 
2. Shut All Valves On The Suction And Discharge Side. 
3. Open Bypass Valve. 
4. Clean The Suction Filter If The Pump Has Drawn Oil From Dirty Tank Or The Last Part Of Oil Tank.  
5. Record Operating Time, Pressure, Tank Levels As Per Standing Instructions On Board.

Explain The Operation Of Centrifugal Pump?
All Types Of Centrifugal Pumps Depend On Centrifugal Force For Their Operation. Centrifugal Force Acts On A Body Moving In A Circular Path, Tending To Force It Away From The Axis Of Rotation. In The Centrifugal Pump, Vanes Or Impellers Rotating Inside A Close Fitting Housing Draw The Liquid Into The Pump Through The Central Inlet Opening, And By Means Of Centrifugal Force The Liquid Is Thrown Outward Through A Discharge Outlet At The Periphery Of The Housing. The Vacuum Created Thereby Draws Water Into The Casing Through The Inlet Opening. The Process Continues As Long As The Motion Is Provided To The Rotor And As Long As Supply Of Liquid Is Available. In The First Practical Centrifugal Pump, The Rotor (impeller) Was Built With Straight (radial) Vanes. Curved Vanes Were Introduced In Later Type Of Pumps Having Curved Casing With A Volute & Such Pumps Are Called Volute Pumps. (Definition: The Volute Type Casing Or Housing Form A Progressively Expanding Passageway Into Which The Impeller Discharges The Water.)
       The Head At Which A Centrifugal Pump Can Operate Effectively  is Limited. The Double Admission Can Be Adopted For Higher Heads. Great Advantage Of Double – Admission Type Of Pump Is That The Impeller Is Balanced Hydraulically In Axial Direction.

What Are The Main Advantages Of Multistage Pump Over Single Stage Pump?
Single Stage Pumps Are Suitable For Low To Moderate Head. For Higher Heads, Multi-stage Pumps Are Used. In A Multi-stage Pump, The First Stage Receives The Water Directly From The Source Through The Admission Pipe, Builds The Pressure Up To The Correct Single-stage Pressure And Passes It To The Next Stage Where The Pressure Is Further Increased Until The Fluid Is Delivered From The Final Stage As Desired. 

What Are The Major Components Of Centrifugal Pumps?
Major Components Of A Centrifugal Pump Are:
I) Casing Or Housing, 
Ii) Impeller And Wearing Rings 
Iii) Stuffing Box Assembly 
Iv) Bearing And 
V) Drive Shaft. 
        Pump Casing Is Cast And For A Vertical Pump Is Usually Split Axially. For Horizontal Pump The Casing Is Either Split Diagonal Or Built Up Of Radial Pieces, Which Are Assembled On A Shaft In Sequence. The Volute-shaped Housing Is Proportioned To Produce Equal Flow Velocity Around The Circumference And To Reduce Gradually The Velocity Of The Liquid As It Flows From The Impeller To The Discharge Outlet. The Objective Of This Arrangement Is To Change Velocity Head To Pressure Head. Single Or Multi-stage Pumps May Have Single Admission Or Double Admission. The Chief Disadvantage Of The Single-admission Pump Is That The Casing Provides Inlet And Delivery Passages And Accommodates Guides For Impeller And Shaft (bearing And Wear Rings). Casing Also Acts As A Support For Parts And Provides Stuffing Box For A Shaft Seal Or A Gland. The Choice Of Material For Casing And Other Parts Of The Pump Depend Upon The Fluid Passing Through The Pump, (sea Water, Fresh Water, Oils, Acid Etc. And Whether Hot Or Cold). Cost Is An Important Factor In The Choice Of Materials Keeping In Mind The Reliability. Impellers Govern The Efficiency Of The Pump. They Are Designed To Meet A Given Set Of Operating Conditions. The Number Of Vanes In Impeller Vary From One To Eight Or More Depending Upon The Type Of Service, Size Etc. Impellers Are Sub Classified As:
1) Open Type, 
2) Semi-open Type And The 
3) Enclosed Or Shrouded Type As Shown Below. Enclosed Impellers Are Most Efficient.

Explain Operating Procedures For A Centrifugal Pump?
Starting:     
1. Open The Suction Valve Completely. Keep The Discharge Valve Closed At This Stage,
2. Open The Air Vent And If The Water Comes Out From It, Close It (pump Is Full Of Water And Is In 'primed' State).
3. If The Pump Is Of The Self-priming Type With An Attached Vacuum Pump, Keep The Air Vent Closed And Open The Check Valve On The Vacuum Pump Line.
4. Start The Motor (pump)
5. When The Discharge Pressure Has Risen, Open The Discharge Valve Gradually. (For A Self-priming Arrangement, Close The Check Valve Connecting To The Vacuum Pump.)
6. Changeover Suction And Discharge As Required Gradually.
7. Monitor Suction And Discharge Pressures, Load On The Motor, Vibrations, And Leakages Through Valves And Glands. If Necessary 'nip Up' The Gland.

Starting The Pump With Closed Discharge Valve Reduces The Starting Current On The Motor And Prevents Damage To The Pump Parts. Since Centrifugal Pump Is Not A Positive Displacement Type, There Is No Danger Of Build Up Of Excessive Pressure. Pump Casing And Parts Have Been Designed To Withstand Maximum Pressure The Pump Can Produce In This Case.
In Case The Pump Looses Suction, Prime It As Soon As Possible. Avoid Running The Pump Without Liquid Even For Short Periods To Minimise Wear Between The Impeller And Its Guide Ring (wearing Ring).

Stopping The Pump:
1. Incase Of A Pumps Used For Bilge Or Ballast Line, Before Stopping The Pump, Run The Pump 'sea To Sea' For Some Time To Flush The Pump And The Pipe Line Of Contaminated Water.
2. Close The Discharge Valve
3. Stop The Motor
4. Close Suction Valves And All Other Valves That Were Opened For Use. 
Record Starting And Stopping Times As Per Ship Board Instructions And Practices.

1. The Most Important Thing That Will Help You Onboard Is Your Knowledge, Hence  you Must Have Basic Knowledge Of IC Engines, Purifiers, Compressors, Refrigeration Cycle And Plant, Marine Boiler, Steering Gear, Auxilliary Machinery, Pumps, Framo (for Tankers), Basic Automation, Marine Electro Technology.

2. How Can You Acquire The  knowledge?
You Need To Read Books During Your Pre-sea Years, And Remember Just Getting Placements Is Not Enough, If You Are Not Good At Things, You Will Face A Lot Of Problems On Board. Mentioned Here Are The Books You Need Be Thorough With.
For Internal Combustion Engines:
(i)  Reeds 
(ii) D.K Sanyal
(iii) Lambs Question Answers

All Of These Books Are Good, But It Would Be Better If You Stick To One And Read It Thoroughly Before You Switch To Other, So That You Get The Grasp Of The Topics. In Case You Need Any Assistance Regarding Any Topic , Its Always Advised To Look Up To Internet Or Visit Marinelookout And Find Your Answers. 

For Marine Auxiliary Machinery:
(i) HD Mcgeorge.(it Is The Bible For This Subject)
(ii)J.K. Dhar (if You Find Difficulty With Any Topic In McGeorge)

For Marine Boilers: 
(i) GTH FLannagan(best Book Throughout Your Career)
(ii) Milton.

3. Things You Need To Learn Onboard.
Always Keep In Mind While Your Training You Are Onboard To First Learn Then Earn. Some Of The Things You Need To Learn Onboard.
(i) Pipe Line Tracing (eg.  Bilge , Sludge , Fuel Oil Transfer Line, Fuel Oil Service Line, Lub Oil Transfer Line, S.w.cooling Line, Starting Air Line, Fire Line, Bilge & Ballast Line, Ows Line)
(i) Starting And Stopping Of Every Machinery. For E.g Purifier, Compresser, Freshwater Generator, A/E Etc.
(iii) How To Take Bunker And Internal Transfers.
(iv) Sludge/ Bilge  transfer And Shore Discharge Procedores

4.You Should Be Familarised With Recordkeeping,
I) Engine Room Log Book
Ii) Garbage Record Book
Iii) Oil Record Book
Iv) 4/E And 3/E Paper Works

5. You Should Be Well Versed With Terms Like
I) Bunkering 
Ii) Sludge Transfer 
Iii) Bilge Transfer
Iv) Sounding

At Last, Follow Safety Procedures. Keep Your Mind Always Alert And Aware In The Engine Room To Avoid Any Accidents.