Mills Operation

8/3/2019 Mills Operation

1/11

MILLS OPERATION


2/11

Bowl Mill Operational Features

Pre Start

Drive coupling must be properly aligned andlubricated

All areas requiring lubrication should be checked

for proper lubricant and levels

Motor be bumped to check for proper rotation. Setting of roll to ring clearance

Run the pulveriser with all rolls elevated by

the journal stop bolts

Ensure the rolls are not contacting therotating ring

Lower one roll at a time by backing out the

jack bolt until the roll begin to touch the

rotating ring


3/11

Raise the roll to just clear the bowl by approximately

two flats on the jack screw bolt head (Ring to roll

clearance - About 3 mm)

Repeat the same for all rolls Carry out this each time when rolls and/or ring are

replaced

Spring settings

Springs must be adjusted for proper compressionand position

Compression must be set with a hydraulic lock

device

Tightly lock the lock nuts holding spring

compression so that they will not move during

operation


4/11

Position the spring so that there is slight clearance

between spring seat and journal head (0.5 mm)

Periodically check spring setting for proper

compression on each spring All the three springs must be equally loaded

If they are vastly different unequal loads are applied to

mill drive shaft causing excessive bending with

possible damage to vertical shaft worm gear drive

For extended period of low load operation special

settings are required


5/11

CLASSIFIER VANE SETTINGS.

The vanes should be fully closed

Measure each vane lever from a fixed point to ensure that

all vanes will be in same position when set the same

number on the classifier vane scale.

After checking the vane position the pointer is set at the

middle of the scale for initial start up

Repeat this procedure after each major overhaul.


6/11

LUB OIL

Check the oil level and temperature in the gear

case regularly.

Check oil level in the journal during shutdown of the mill.

While checking the oil on dip stick look for

contaminants in the oil.

Collect oil sample once in a month and send it

for analysis.

If the oil is contaminated drain oil from gear case

Flush with new oil/solvent

Refill the oil.

NOW THE PULVERISER IS READY FOROPERATION


7/11

PULVERISER INTERLOCK START PERMISSIVES

MILL DISCHARGE VALVES ARE OPEN

SEAL AIR VALVE IS OPEN

COLD AIR DAMPER IS OPEN

R.C.FEEDER INLET DAMPERS ARE

OPEN

TRAMP IRON HOPPER VALVE IS OPEN

D.C.POWER TO FSSS IS AVAILABLE

BURNER TILT IN HORIZONTAL

POSITION AND BOILER AIR FLOWADJUSTED BETWEEN 30 TO 40% OF

FULL LOAD AIR FLOW

MILLOUTLET TEMP. IS LESS THAN

930C

P.A.PRESSURE IS ADEQUATE

EITHER A MINIMUM OF 3 NEXT

IMMEDIATE HO/LO NOZZLE VALVES

ARE OPEN OR NEXT IMMEDIATE

ELEVATION MILL IS WORKING AT

GREATER THAN 50% LOAD AND

BOILER LOAD IS GREATER THAN 30%


8/11

PULVERISER INTERLOCK

WHEN MILL IS STARTED IMPULSE SHALL BE

GIVEN FOR

PERMISSION TO OPEN HOT AIR GATE

PERMISSION TO START R.C. FEEDER

PERMISSION FOR REGULATORS IMPULSE TO ACT ON

HOT AIR DAMPER


9/11

Allow the pulveriser to run for several

hours without load. Check lubricant flow and temperature.

Check bearing for noise and vibration

Recheck the rolls are not hitting the ring.

Pulveriser warming.


10/11

PULVERISER INTERLOCK

HOT AIR GATE HOT AIR GATE WILL OPEN ONLY IF MILL IS ON

IF THE HOT AIR GATE IS OPEN IMPULSE SHALL BE GIVEN TO

RELEASE HOT AND COLD AIR DAMPER CONTROL TO REGULATE

HOT AIR GATE WILL CLOSE AUTOMATICALLY AFTER 30 SEC.

UNDER ANY OF THE FOLLOWING CONDITIONS

MILL IS TRIPPED

MILLOUTLET TEMP. IS VERY HIGH

R.C. FEEDER STOPS WITHIN 5SEC. OF ITS START

WHEN HOT AIR GATE IS CLOSED IMPULSE SHALL BE GIVEN FOR

OPENING THE COLD AIR DAMPER PROVIDED IF THE MILL IS ON


11/11

R.C. FEEDER INTERLOCK

START PERMISSIVES

NO BOILER TRIP CONDITION PREVAILS

ELEVATION A.C. AND D.C. ARE AVAILABLE

IGNITION ENERGY IS AVAILABLE

MILL IS ON

HOT AIR GATE IS OPEN

FUEL AIR DAMPERS ARE CLOSED

NO STOP SIGNAL

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Mills Operation