As chief engineer describe the procedures involved in the complete inspection of an auxiliary smoke tube boiler indicating areas of significant interest. (b) State the possible faults which might be found. (c) Suggest how internal corrosion may be prevented.

Inspection preparation: 

1. Carry out risk assessment with counter measure.
2. Check for spares and tools.
3. Inform bridge before shut down.
4. Stop machinery related to steam.
5. Stop boiler, switch off panel board, breaker and notice.
6. When boiler pressure at about 1.5 bar open vent cock.
7. Blow down water and allow time for cool down boiler.
8. Follow enclosed space checklist.
9. Open top manhole door first and then bottom door. 
10. Take out burner
11. Ventilate the boiler until 21% oxygen is achieved.

Internal inspection:  Water side inspection:

1. Check steam drum for corrosion, scaling and pitting.
2. Manhole seat and surface condition.
3. Condition of all feed, chemical feed blow down lines and inside pressure parts or chocking, security and leaks.
4. Check for freedom of expansion of drum and heater.
5. Inspect tube for corrosion, excessive deposit, flame cracking and deposit.
6. Measure thickness of scale by using commercially available. 

Gas side inspection:

1.      Check exterior of drums for signs of tube roots, leakage, corrosion and overheating.

2.      Condition of refractory.

3.      Around the burner assembly and accumulation of soot and carbon + fuel impingement.

4.      Check soot blower for distortion, worn bearing, rubbing of tubes, condition of nozzles, cracks, freedom of movement and effective lubrication.

5.      Distortion of any welded surface.

 

External inspection

• Foundation: Boiler support, bolting and securing arrangement (fixed and sliding seating, chocks, rolling stays if any etc) to be examined.
• Safety valve:
• -         The proper operation of safety v/v has to be confirmed.
  -         Safety v/v easing gear has to be examined.  

• Boiler mounting: 

1.      Soot blower

2.      Air vent cock

3.      Main steam stop v/v

4.      Feed stop and check v/v

5.      Scum v/v

6.      Water level gauge

7.      Manhole cover

8.      Pressure gauge to be calibrated.

9.      Sampling v/v

10.  Blow down v/v;         (All mountings have to be inspected)

• Alarm test:
• -         Water level high – alarm
  -         Water level low – alarm
  -         Water level too low – automatic shut down with alarm
  -         Forced draft fan flame failure - automatic shut down with alarm
  * Manual emergency shutdown: Checking for shut down the boiler FD fan and fuel oil service pump from remote area in case of fire. 
  * Log book: Review of boiler operation and feed water.
  Possible faults might be found:
  In furnace:
  *       Deformation - due to overheating of the furnace
  Causes: Scale, oil, sludge, poor circulation.
  *       Wastage
  Causes: corrosion and erosion.
  *       Crack – due to local overheating for overshoot deposit.
  Causes: rapid fluctuation of thermal and mechanical stress, results of improper starting and shutting down.
  *       Damage of manhole door gasket
  *       Bulging in refractory
  Water side:
  *       Tube crack, deformation
  Causes: Scale, shortage of water, oil in water.
  *       Corrosion: Presence of O₂ hard salt.
  Gas side:
  *       Excess carbon
  Causes: bad combustion
  *       Corrosion – due to bad quality fuel.
  *       Damage of soot blower nozzle
  Causes: erosion.
   
  
  (c) Internal corrosion may be prevented:
  1.     Keep the boiler feed water in alkaline condition.
  2.     Oxygen must be removed for transformation.
  3.     Prevent sea water ingress (leaking condenser)
  4.     Prevent oil ingress.
  5.     Keep scale free boiler water by using distill water.
  6.     Ensuring chemical reserve in the feed water.
  7.     Maintain feed water temp as high as possible so that dissolved gases will be released.
  
  
  • Actions in Case of Economizer Fire:
  ·        Inform bridge and chief engineer take the permission for slow down or stopping main engine.
  ·        Slow down main engine
  ·        If firefighting equipment if fitted on economizer it should be put in operation.
  ·        Never soot blow while economizer on fire it can cause hydrogen fire and melt down the coils stack.
  ·        If soot fire is considerably big shut down the main engine and boiler.
  ·        Spray water on external casing of the uptake to cool the affected area.
  ·        Few times starting and stopping of main engine of main engine should be done to blow out collected soot at the uptake.
  
  
  • After fire is out:
  -       After cooling down to ambient temperature open the economizer cover.
  -       Clean the inside parts of economizer
  -       Check the tubes for any damage if any repair it.