FSSS (FURNACE SAFEGUARD & SUPERVISORY SYSTEM)

Furnace Safeguard and Supervisory System:

• A fully digital control system which governs mandatory requirements related to safe startup and safe shutdown of the boiler.
• Includes main boiler permissive & protection.
• Includes heavy oil & light oil firing interlocks.
• Includes permissive & protection related to mills & feeders.

Unit start up sequence

• Boiler purge operation.
• Startup of oil firing.
• Adequate Ignition permit.
• Firing of coal elevations.
• Flame sensing by scanners.

BOILER START UP

BASICS

• The boiler can be placed in service, initially or after a “Master Fuel Trip,” through FSSS.
• Furnace Purge: Before any fuel firing can takes
•  Initially, the Heavy Oil must be re−circulated and heated to obtain the proper temperature and viscosity for efficient combustion.
• After this is accomplished, the Heavy Oil Trip Valve (HOTV) can be closed and then the ‘furnace purge cycle’ can be started.
• After the furnace purge cycle is completed, the heavy oil elevation (AB, CD, EF & GH) can be taken into service.
• An oil elevation is said to be “In Service,” when at least three out of four heavy oil nozzle valves are open and the flame is sensed by the scanners.
• After the heavy oil elevation is ‘in service’, either of the adjacent coal elevation can be taken into service because “Ignition Permit” is now available for starting the Pulverizer.
• A Coal elevation is said to be “In Service” after the Pulverizer is ON, its Hot Air Gate (HAG) is open and the associated Feeder is proven (i.e., feeder ON for more than 50 seconds).
• A fire ball signal is establish when the associated fireball flame scanners sense flame & ELEVATION flame indicate is illuminated on the FSSS console in control room.

FSSS LOGIC

FSSS logics can be broadly divided into 3 sections.

• Unit logic
• Oil elevation logic
• Coal elevation logic

UNIT LOGIC

• Boiler purge logic
• Master fuel trip logic
• Oil trip valve operation logic
• PA fan logics
• scanner air fan logics
• seal air fan logics

FURNACE PURGE

Purpose:

• Complete Removal of un-burnt fuel from entire furnace

Procedure:

• A 5 or 8 or 10 minute mandatory cycle (as per OEM) in which at least one set of FD and one ID fans are run with 30 to 40% air flow, with NO Fuel input to the furnace, to ensure the removal of the un-burnt fuel left over in the furnace area after the last master fuel trip

Consequence:

                Master Fuel Trip Relays are reset

                Firing of fuel into the furnace is allowed

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