FORCED DRAFT FAN PROTECTIONS, PERMISSIVE AND INTERLOCK

Forced Draft Fan is types of pressurized fan for providing positive pressure, supplies air to the Air-preheater, where it taking the heat from the flue gases which is coming from the Boiler Outlet.

INTERLOCK system and PROTECTION 

are mostly used in every power sector for preventions of any physical damage of equipment or human life. PERMISSIVE is also an important for startup and proper running of machines.

      

FD FAN PERMISSIVES:

1.       LUB OIL PRESSURE > 4 BAR.

2.       LUBE OIL TANK LEVEL NOT LOW.

3.       LUBE OIL TEMP ADEQUATE.

4.       ANY LUBE OIL PUMP IN SERVICE.

5.       CONTROL OIL PRESSURE > 8 BAR.

6.       BLADE PITCH AT MINIMUM POSITION (<5%) AND IN MANUAL.

7.       OUTLET GATE CLOSED.

8.       FAN BEARING TEMPERATURE NOT HIGH (<90 ⁰C).

9.       MOTOR BEARING TEMPERATURE (DE/NDE) NOT HIGH (<85 ⁰C).

10.    MOTOR WINDING TEMPERATURE (<125 ⁰C).

11.    ANY ID FAN IS RUNNING WITH BOTH I/L AND O/L GATES OPEN & OTHER FD FAN IS OFF (SECOND FD FAN WILL START ONLY IF BOTH ID FANS ARE RUNNING BOTH I/L AND O/L GATES OPEN).

HT MOTOR START PERMISSIVES SATISFIED:

Ø  NO SWGR DISTURBANCE AVAILABLE

Ø  NO MSTR TRIP OPTD

Ø  LOCAL PUSH BUTTON RELEASE

Ø  SWGR AVAILABLE

INTERLOCKS:

1.       AFTER START COMMAND.

Ø  OUTLET GATE OF OTHER FAN WILL CLOSE AND BLADE PITCH WILL GO TO MINIMUM POSITION IF IT IS NOT RUNNING.

Ø  FAN STARTS AND THEN OUTLET GATE OPENS (IF GATE IS IN AUTO).

2.       STANDBY LOP WILL START.

Ø  IF FAN IS RUNNING AND CONTROL OIL PRESURE IS  < 5 BAR AND LUB PR < 4 BAR .

 OR

Ø  IF FAN IS RUNNING AND RUNNING LOP TRIPS.

OR

Ø  LOP ON FOR >32 SEC AND CONTROL OIL PRESURE IS  < 5 BAR OR LUB PR < 4 BAR.

3.       BLADE PITCH CONTROL DOES NOT OPERATE IF CONTROL OIL PRESSURE IS < 8 BAR [HLV10CP001,002,003].

4.       FAN TRIPPING INTERLOCKS (OTHER FAN IS ON).

Ø  BLADE PITCH COMES IN MINIMUM POSITION AND CHANGES TO MANUAL CONTROL AND O/L GATE CLOSES, BOILER LOAD REDUCES TO 50% MCR ,TRIPPING COAL ELEVATION IN SERVICE MORE THAN FOUR (FSSS). 

IF ONE FAN TRIPS OTHER IS OFF THEN:

Ø  BLADE PITCH CONTROLS WILL COME FROM AUTO TO MANUAL MODE BRINGING IT TO MAX POSITION (BLADE PITCH MAX FOR OTHER FAN AND O/L GATE OPEN).

Ø  EMERGENCY SCANNER AIR DAMPER OPENS.

Ø  BOILER TRIPPING.

Ø  O/L GATE WILL REMAIN OPEN.

5.       WHEN BOTH FD FANS ARE IN SERVICE, IF ANY ONE ID FAN TRIPS, CORRESPONDING FD FAN WILL TRIP.

6.       IF BOTH ID FANS TRIP, BOTH FD FANS ALSO WILL TRIP.

7.       FD FAN CNTRL OIL PR > 8 BAR HI (IN PRIORITY 7 WILL GET RESET IF CONTROL OIL PR DROPS < 8 BAR).

 PROTECTION: 

SN	DESCRIPTION	VALUES			TIMER (SEC)
		NORMAL	ALARM	TRIP & ALARM
1.	FD FAN MOTOR BRG TEMP (DE & NDE) 0C	≤85	>85	≥90	5
2.	FD FAN BRG VIBRATION DE & NDE (MM/SEC)	≤9.9	>9.9	>19.8	10
3.	MOTOR BRG VIBRATION DE & NDE (MM/SEC)	≤9.9	>9.9	>15.5
4.	FD FAN BRG TEMP ( 0C )	<90	>90	>110
5.	FD FAN MTR WDG TEMP (0C) (1/6)	≤125	>125	>130	2
6.	POST PURGE FAN TRIP FROM FSSS	- 10	+ 75	-175 / +150	-