Air Bottles

Question: What Is An Air Bottle/receiver? What Is Its Purpose And Capacity For Onboard Use
Answer: An Air Bottle Is A Storage Unit Where Compressed Air, At Pressure Around 28-30 Bar Supplied By Air Compressor Is Stored. The Major Purpose Of Storing The Compressed Air In Air Receiver Is To Use It For Starting The Main Engine And Auxiliary Engine. According To SOLAS, An Air Bottle Must Be Capable Enough To Provide 12 Consecutive Starts For A Reversible Engine And 6 Consecutive Starts For A Non-reversible Engine. This Is Known As The Capacity Of An Air Bottle.

Q. What Are The Mountings On An Air Bottle?
Ans: List Of Air Bottle Mountings: 
1. Relief Valve: It Is The Most Important Mounting On The Air Bottle , Generally On Top Of The Receiver, In Case Of Excessive Or Sudden Pressure Rise More Than 10% Of The Air Bottle Capacity, These Relief Valve Lift And Release Excess Air, Then Sit Back. 
2. Fusible Plug: In Case Of Engine Room Fire If The Temp Rises Above 150 Degree C, The Fusible Plug Melts And Through A Separate Connection Releases Air Into The Atmosphere Outside Engine Room Such That, The Air Bottle Doesn't Burst And Infuriate The Engine Room Fire. 
3. Drain Valve: Generally, There Are Two Drain Cocks Fitted Adjacent To Each Other Such That If One Gets Chocked Other Can Drain The Air Bottle. 
4. Pressure Gauges: Correctly Calibrated Gauges Must Be Used And Pressure Must Lie Within 27-30 Bar Which Is Required Pressure For Starting Main And Auxiliary Engines. 
5. Main Valve For Starting Air To The Main Engine: It Is A Sluggish Opening Valve So That A Sudden Pressure Surge In The Start Air Line Is Avoided; Otherwise Start Air Line Might Burst. 
6. Valve For Start Air To Auxiliary Engines: To Supply Air To Start Auxiliary Engines. 
7. Inlet Valve From Main Air Compressor: To Fill Air Bottles/receiver. 
8. Manhole Door: Elliptical Door For Entry Of A Person For Air Bottle Inspection.

Q. Mention If There Are Any Alarms In Air Bottle?
Ans: Air Bottle Low Air Pressure Alarm Is Most Significant Alarm In The Receiver. When This Alarm Is Activated, Starting Of Main And Auxiliary Engine Is Not Possible. This Alarm Implies That There Is Not Enough Air In The Bottle.

Q. What Is Most Important Routine We Have To Carry Out Every Watch On Air Bottle And What Are Its Implications?
Ans: Every Watch During Rounds We Must Drain The Air Bottle. We Must Keep The Drain Cock Open Until All The Moisture Is Drained. If Not Drained Regularly, It May Have Disastrous Results. 
1. If Oil Carryover From Compressor Is Taking Place Then Chances Of Catching Fire Is Evident As Heat Is Only Element Left Which Is Required To Complete The Fire-triangle. 
2. If Moisture Carryover Along With Compressed Air Takes Place, This Moisture Can Corrode The Air Bottles.

Q. What Is Material Of Air Bottle And Procedure For Air Bottle Inspection?
Ans: The Air Bottle Is Made Up Of Cast Iron. The Steps Followed For Air Bottle Inspection Are As Follows: 
1. The Drain Cocks Are Opened, So That The Bottle Is Completely Drained. 
2. When The Air Pressure In The Bottle Comes Near To Zero, Than The Manhole Door Is Opened. 
3. Thorough Ventilation Is Carried Out By Using Ventilation Fans. 
4. An Enclosed Space Entry Permit Is Being Made Under The Guidance Of Chief Engineer. 
5. Oxygen Content Is Checked Inside By Oxygen Meter, Must Be Around 20.8%. 
6. Now, A Person Can Enter With A Standby Person Standing Outside. 
The Person Inside Checks: 
A. The Walls Of Bottle For Corrosion. 
B. The Bottom For Moisture Content Or Oil Accumulation. 
C. Checks The Condition Of Compensating Rings (fitted For Compensating The Strength Lost Due To Cutting Manhole Door). 
D. Checks If Any Drain Is Blocked From Inside. 
E. Safety Valve Fitting Area. 
Sometimes, Checks Can Be Carried Out From Outside By The Help Of An Instrument Called Boroscope.