1.9 Furnace Safeguard Supervisory System

Furnace safeguard supervisory system

OBJECTIVE:

·        SAFE OPERATION OF PLANT

·        LONGEST EQUIPMENT LIFE.

·        MINIMUM ENVIROMENTAL EFFECT.

·        MAXIMUM EFFICIENCY

 

INTRODUCTION:

FSSS means furnace safeguard & supervisory system , the system which is used in almost all types of boiler. The system has been designed to offer maximum protection and to ensure the execution of a safe, orderly operating sequence in the start up and shutdown of fuel firing equipment in a boiler and to prevent errors which may be committed by an operator due to ignorance.

 

Furnace safeguard & supervisory system are as below:

1.      Furnace purging

After a boiler shutdown or a flame failure, the burner cannot be lighted up unless it is ensured that the furnace has been sufficiently purged and it is free of any combustible gases. Any indication of unburnt gases main also be linked with furnace trip, during operation.

2.      Ignition interlock

This is associated with furnace purging and also FD and ID fan running.

3.      Firing sequence

In some pulverized fuel firing system and multiple fuel firing system, in order to have save fuel burner firing, a certain firing sequence order is recommended. Interlocks are provided for proper sequence in firing.

4.      Flame supervision

Flame scanner are provided for sensing the flame of the main burner as well as the pilot burner. If the pilot burner scanner does not sense the flame one cannot open the fuel valve. Again if during operation the main scanner does not see the flame, the burners trip occurs.

5.      Explosion and implosion flaps

Excess furnace pressure can cause furnace explosion. This can occur when during operation of the boiler, the ID fan trip or there is a heavy tube leakage or sudden catching of fire of the unburnt gases after a flame blow out. Explosion flaps are provided to take care of this. but to ensure further safety boiler trip is associated very high furnace pressure.

Implosion is a reverse phenomenon of explosion. It occurs when during very high negative pressure. This may happen because of FD fan trip. Unlike explosion effect, the tube will buckle towards the furnace chamber. Though implosion flaps are prevent this, furnace trip is recommended.