BOILER SAFETY- ALARM & TRIPS

 

BOILER SAFETY DEVICES

1) Safety valve 

2) Low / high water level alarm 

3) Too low water level alarm and shut down 

4) Water level indicators 

5) Pressure gauge 

6) Low fuel oil pressure alarm

7) Low / high fuel oil temperature alarm 

8) Flame failure alarm 

9) Smoke density alarm 

10) Easy gear arrangement 

11) Air vent 

12) Force draught fan stop alarm 

13) Low / high steam pressure alarm


Shut-downs :

* steam pressure 

* Flame failure 

* Loss of control power 

* Loss of primary/FD fan 

* High water level on turbine driven plants

* Low water Level


Alarms: 

* Low water level 

* Low steam pressure 

* Low fuel oil temperature 

* Low atomizing pressure for burners 

* High uptake temperature 

* De-superheated steam temperature high



FURNACE EXPLOSION

It is instantaneous combustion of explosive or highly flammable gas, vapor or dust accumulated in a boiler setting. Often it is 

Condition-:

a. accumulation of unburned fuel 

b. Air and fuel in an explosive mixture, and 

c.  A source of ignition.

Causes-:

a. Flame failure due to liquids or inert gases entering the boiler fuel system. 

b. Insufficient purge before lighting the first burner. 

c. Human error 

d. Faulty automatic fuel regulating controls 

e. Fuel shutoff valve leaking 

f. Unbalanced fuel/air ration 

g. Faulty fuel supply systems 

h. Loss of furnace draft 

i. Faulty pilot igniters 

Preventive measures: 

a. Check the operation of the boiler periodically 

b. If a burner goes out accidently, shut off the igniter and fuel supply. 

c. scavenge the furnaces and gas passes before again attempting ignition. Determine and remedy the cause of the stoppage always. 

d. Keep burners and all allied equipment clean.


Boiler Water Low/High Level Alarm and Trip (Electrically operated)


1. The Classification Society requires that low boiler water level alarm (audio-visual) and trip must be fitted. 

2. It operates on the principle that, while unlike magnetic poles attract each other, like poles are repulsed. 

3. An external float chamber with balance connections to the steam drum is mounted in way of the drum water level. 

4. A float within the chamber then relates to this water level, and moves an attached magnet up and down in response to any changes of water level within the steam drum. 

5. Four micro switches with magnetically operated arms are fitted on the outside of the balance chamber. They are arranged so that, when an internal magnet comes level with one of these external magnets, like poles are presented, and so, repelling each other, operate the micro switch.

6. The positions of the four switches are set to correspond to predetermined water levels within the steam drum.

7. One switch will correspond to a low water level condition, and when this is reached will operate an alarm. 

8. The next switch positioned to a predetermined low low water level will trip out the fuel oil shut-off valve, so

shutting the boiler down

9.  Micro switches are also fitted to the isolating valves on the balance connections to ensure that they are fully open when the device is in operation.

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