1. Rajan Bhandari Senior Lecturer
5. Boiler operation
Rajan Bhandari
Senior Lecturer

2. Objectives Start a boiler safely from cold condition.
Protect a superheater during boiler start up.
Manage routine work involved for a boiler operating onload.
Assess combustion quality of a boiler.
Deal with abnormal operating conditions of a boiler in a safe manner.

3. Overview
The lesson briefly covers the recommended general procedures for the operation of auxiliary boilers (with or without a superheater) onboard ships. It looks at normal safe operational procedures as well as emergency operating conditions. Monitoring of combustion efficiency is also covered in the text.

4. Starting up a boiler
Check that the boiler is closed-up (especially after repairs).
Check (physically) that all appropriate valves are shut or open for safe starting of the boiler.
Boiler water filled to slightly below normal level.
Starting treatment chemicals may now be added to the boiler water.
Check and clear the furnace of any flammable materials.
Ensure that the boiler uptake passage is clear.

5. Starting up a boiler
Pre-purging of furnace for a specified amount of time is necessary to clear the gas-side of flammable gases, to avoid a starting explosion!
On a cold boiler, the firing-up must not be speeded up too much in order not to overstrain the boiler material unnecessarily by quick, uneven temperature raises.
Keep the boiler vents open until a heavy steam jet is flowing out (until a boiler pressure of about 1 bar is reached).
Before the boiler is put on load, blow-through the gauge glasses, test the safety valves using easing gear and try out the safety cutouts.

6. Boiler with integral super heater
Keep superheater vent open and maintain flow

7. Flame should fill the furnace without any impingement.
Colour of flame should be moderately bright orange.
Colour of smoke as observed from the funnel should be brownish hazy.

8. Oxygen:
3 to 4% by volume (for fire tube boilers), 0.5 to 1.5% by volume (for water tube boilers with high efficiency burners)
Carbon Dioxide:
12 to 14 % by volume. Higher the reading, the better is the combustion efficiency. It must be remembered that theC02 reading changes with the fuel type / quality and the level of excess air supplied to the burners

9. Gross oil contamination
The most dangerous water contamination is heavy fuel oil entering the boiler
the boiler could be completely destroyed due to overheating of the furnace

10. Gross oil contamination
Boiler taken off load / Shutdown
Subsequently overflow the oily water through top manhole opening
Boiling out or chemical cleaning:
Alkaline soak / degreasing using Sodium hydroxide or Phosphate
Wash out
Acid clean to remove milll scale
Wash out and neutralise
Passivate with Hydrazine or Alkaline chemicals

11. Small oil contamination
Reduce the boiler load
Surface blow
Maintain Alkalinity by adding Alkaline chemicals
Add Anti-foam compound (if available)

12. Effect of oil contamination
Dark oily film in gauge glass
Foaming / priming
Overheating of boiler heat transfer surfaces
Acid formation and lowering of PH value of boiler feed

13. Effect of high water level
Reduce firing rate.
Check & confirm high water level
Operate blowdown system.
Throttle feed check valves.
If bad water hammer due to carry-over is experienced, close steam outlet valve to prevent damage to pipe lines and machinery.

14. Water level below gauge glass
Shut-off burner (if not cut-out automatically).
Take the boiler out of load.
Confirm boiler water level by blowing through gauge glass.
Ensure no internal damage due to overheating. Open and inspect internals
Do not bring-up the water level in haste until the boiler parts are cooled down.
25mm
Lowest permissible water level
Lowest visible water level
51mm
Heating surface

15. Survey of boiler accidents
Reason for boiler failure
Fire-tube
Water-tube
Mechanical, Electrical failures & Maintenance
35%
19%
Boiler water troubles
17%
36%
Personnel
16%
13%
Corrosion and erosion
11 % 9%
Installation and design deficiencies
10% 8%
Defective material 3%
Others reasons - miscellaneous
12%
Note: The above tabulation is based on a survey of 250
water-tube boilers and 400 fire -tube boilers.

16. Water tube leak- detection
Remove Castable from here
Tube plate
Water tube

17. Boiler tube leak - Plugging

18. Water tube leak- apply castable

19. Summary Start a boiler safely from cold condition.
Protect a superheater during boiler start up.
Manage routine work involved for a boiler operating onload.
Assess combustion quality of a boiler.
Deal with abnormal operating conditions of a boiler in a safe manner.