coal system logic

SALAYA FSSS LOGIC DESCRIPTION---------------------------------------------------------------------------------------------------------------------------

3.3 Coal System Control Logic

The coal system comprises the equipment listed as follows: Mills, No.1~4 Mill discharge dampers, burner inlet isolation damper, inlet cold air isolation damper, inlet hot air isolation damper, Mill seal air damper, discharge valve sealing air damper, Mill fire fighting motor valve, Mill lube oil pump, Mill oil tank heater, Mill oil return pipe heater, Coal feeders, Coal feeder inlet dampers, Coal feeder outlet dampers. Coal feeder seal air damper.

3.3.1 Mills start sequence control

The mill starting sequence permissive conditions for the coal elevation are listed as follows: (AND)

No Mill trip conditions existCoal system firing is permitted (See 3.1.4.3);Coal elevations firing energy is OKAny seal air fan is running The Mill seal air/grindin diff press is OKThe Mill lube oil system is OKThe Mill in remote service

The mill starting sequence is:

Step 1: Open mill seal air damper Step 2: Open mill discharge dampers, inlet isolation dampers, discharge valve sealing air damper

Step 3: Open mill inlet cold air isolation damper and inlet hot air isolation damper

Step 4: Open feeder outlet damper and feeder seal air damper Step 5: Start mill

Step 6: Start coal feeder, set feeder speed min

Step 7: Open coal feeder inlet damper

When there are more than 3 burner flames at the elevation, the coal elevation is in service

3.3.2. Mills stop sequence control

The permissive condition for stopping the Mill:(AND)The relevant oil elevation is in service;

Stop the Mill sequence is:

Step 1: Set coal feeder feedrate min.

Step 2: Close inlet hot air isolation damper Step 3: Close coal feeder inlet damper

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ABB BAILEY BEIJING ENGINEER 1 of 4 4/19/2023


Step 4: Stop coal feeder

Step 5: Close coal feeder outlet damper

Step 6: Stop mill

Step 7: Close mill discharge dampers and burner inlet isolation dampers, discharge valve sealing air damper

3.3.3. Mills start permissive conditions (10HFC10AJ001)

The mill start permissive conditions:(AND)

The mill starting sequence permissive conditions are met,(see 3.3.1)The mill discharge dampers 1~4 openedBurner inlet isolation damper 1~4 openedThe mill motor bearing temp normalThe mill motor winding temp normalThe mill air powder mixture temp normalThe mill seal air damper openedThe mill fire fighting motor valve closedThe mill inlet hot air isolation damper openedThe mill inlet cold air isolation damper openedThe mill pyrite hopper inlet valve openedThe mill in remote controlThe mill breaker ready to closeNo mill control circuit fault signalNo mill local emergency stop operated signalNo mill tripped on fault signal

3.3.4 The mill emergency trip conditions

Any of the instances listed as follows will trip the Mill : (OR)

Primary air/furnace diff press LL (2/3)The mill motor bearing temp >90℃The Mill seal air/grindin diff press low delay 1 minAll the mill outlet dampers closedAll the mill lube oil pump stopped delayedThe mill lube oil press LL(2/3) delay 2sThe mill retarder bearing temp >80℃The mill shaft bearing temp >90℃The mill lube oil temp >65℃The mill oil tank temp <25℃The mill oil tank level LAt least 3 coal burners lost flame when mill runningThe mill ignition permit lost when mill runningBoth primary fans stoppedManual trip PBMFT RUNBACK(only for D,E,F)



When Mills emergency trip happened:Close mill hot air control valve and hot air isolation damperClose coal feeder outlet dampersStop coal feederStop millClose mill cold air control valve and cold air isolation damperClose mill discharge dampers 1~4Close burner inlet isolation dampers 1~4Open mill fire fighting motor valve, 10 min later close it.

3.3.5 The mill lube oil station

The mill lube oil pump (10HFV10AP001, 10HFV10AP002):Start permissive condition:(AND)The mill oil tank level not lowThe mill oil tank temp >25℃

Stop permissive condition:The mill stopped delay 120s

The two pumps are backups for each other. When the interlock switch is on, after lube oil pump running delay 25s, if the mill lube oil press low or lube oil flow low delay 3s, start another oil pump

The mill auto stop conditions: (any of the following conditions can cause the mill trip at first, 120s later auto stop the lube oil pump)

The mill lube oil press LL(2/3) delay 2sThe mill retarder bearing temp >80℃The mill shaft bearing temp >90℃The mill lube oil temp >65℃The mill oil tank temp <25℃The mill oil tank level L

The mill oil tank heater (10HFV10AN001):If the mill oil tank level not low and oil tank temp <35℃, it will auto start oil tank heaterIf the mill oil tank temp >40℃, it will auto stop oil tank heater

The mill oil return pipe heater (10HFV10AN002):If the mill oil tank level not low and oil tank temp <45℃, it will auto start oil tank heaterIf the mill oil tank temp >49℃, it will auto stop oil tank heater

The mill lube oil system is OK (one of the mill start permissive conditions) (AND)Any lube oil pump is runningThe mill lube oil press not low delay 3minThe mill lube oil temp >30℃The mill lube oil flow not lowThe mill oil station filter diff press not high



3.3.6 The coal feeder (10HFB10AF001)

Start permissive conditions:(AND)The mill start permissive conditions are metThe mill running The coal feeder outlet damper openedThe coal feeder seal air damper opened

When MFT, it will auto trip coal feederWhen mill tripped, it will auto trip coal feeder


coal system logic

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