The document provides an overview of a ball and tube mill, including its operation principle, primary air systems, motor and pumps, girth gear system, and advantages and disadvantages. It describes the mill's instrumentation, including differential pressure level measurement, noise sensor level measurement, and instrumentation in the girth gear. The level measurement works by introducing air into pipes at the bottom and top of the mill to detect pressure differences indicating the coal level. A noise sensor also indicates coal level based on the noise in the mill.

2. CONTENT
• AN OVER VIEW OF
BALL&TUBE MILL
• INSTRUMENTATION
INVOLVED IN BALL&TUBE
MILL

3. AN OVER VIEW OF
BALL&TUBE MILL
• MILL OPERATION PRINCIPLEMILL OPERATION PRINCIPLE
• PRIMARY AIRPRIMARY AIR
• MOTOR &PUMPSMOTOR &PUMPS
• GIRTH GEAR SYSTEMGIRTH GEAR SYSTEM
• ADVANTAGES &ADVANTAGES &
DISADVANTAGES OF BALL&TUBEDISADVANTAGES OF BALL&TUBE
MILLMILL

4. MILL OPERATION PRINCIPLE:MILL OPERATION PRINCIPLE:

5. The
pulverized
fuel moves
through the
annular space
between the
Fixed trunion
tube and the
rotating hot
Air tube on its
way to the
classifier.
TRUNION TUBE
HOT
AIR
TUBE

6. PRIMARY AIRPRIMARY AIR
• MAIN AIR:MAIN AIR: Air that lifts pulverized coalAir that lifts pulverized coal
from the Mill shell.from the Mill shell.
• BY PASS AIR:BY PASS AIR: Mixes with the raw coal andMixes with the raw coal and
dries it before it enters the Mill.dries it before it enters the Mill.

7. Mill MotorsMill Motors
• MAIN MOTORMAIN MOTOR
• AUX MOTORAUX MOTOR
PUMPSPUMPS
• B&S PUMPB&S PUMP
• HP PUMPHP PUMP
• LP PUMPLP PUMP

8. GIRTH GEAR SYSTEM:GIRTH GEAR SYSTEM:
• A girth gear greasing system is provided forA girth gear greasing system is provided for
continuous lubrication of the girth gearcontinuous lubrication of the girth gear
when either aux /main motor is on . Awhen either aux /main motor is on . A
grease tank is provided at 0 mt in front ofgrease tank is provided at 0 mt in front of
the mill .For supplying the grease two pumpthe mill .For supplying the grease two pump
are provided either one of which is kept on .are provided either one of which is kept on .
The grease is supplied to a block in theThe grease is supplied to a block in the
girth gear greasing panel from where all 6girth gear greasing panel from where all 6
outlets going to different portion of girthoutlets going to different portion of girth
gear for spraying of grease.gear for spraying of grease.

9. ADVANTAGES &ADVANTAGES &
DISADVANTAGESDISADVANTAGES
• ADVANTAGES:ADVANTAGES:
• 1: high output up to 50 tones per hour1: high output up to 50 tones per hour
• 2: No maintenance over a long periods2: No maintenance over a long periods
• 3: no mill rejects, no problems with tramp iron3: no mill rejects, no problems with tramp iron
DISADVANTAGES:DISADVANTAGES:
• 1: high power consumption.1: high power consumption.
• 3: virtually constant power consumption at all loads, low3: virtually constant power consumption at all loads, low
load operation is there fore not economical.load operation is there fore not economical.
• 4: Unplanned stops leave the mill full of coal which under4: Unplanned stops leave the mill full of coal which under
unfavorable conditions, can ignite .unfavorable conditions, can ignite .

10. INSTRUMENTATION INVOLVED
IN BALL&TUBE MILL
• DP LEVEL MEASUREMENT IN MILLDP LEVEL MEASUREMENT IN MILL
• LEVEL MEASUREMENT BY NOISELEVEL MEASUREMENT BY NOISE
SESORSESOR
• INSTRUMENTATION IN GIRTH GEARINSTRUMENTATION IN GIRTH GEAR

11. PRINCIPLE OF DP LEVELPRINCIPLE OF DP LEVEL
MEASUREMENT IN MILLMEASUREMENT IN MILL
• The system compromises of two circuits’The system compromises of two circuits’
wiz measuring circuit and purge airwiz measuring circuit and purge air
circuit .Three sets of pipes enter on eithercircuit .Three sets of pipes enter on either
side the millside the mill
• The bottom sets of pipes are terminated inThe bottom sets of pipes are terminated in
the nozzles. While the upper pairs terminatethe nozzles. While the upper pairs terminate
in the elliptical nozzles . All pipes arein the elliptical nozzles . All pipes are
mounted on the fixed part of the mill.mounted on the fixed part of the mill.

12. PURGE AIR CIRCUITPURGE AIR CIRCUIT
• The circuit introduces periodically compressed airThe circuit introduces periodically compressed air
at high pressure for cleaning of the measuringat high pressure for cleaning of the measuring
taps .During purging the solenoid valve disconnecttaps .During purging the solenoid valve disconnect
the measuring circuit from the mill probes tothe measuring circuit from the mill probes to
isolate the measuring equipments which can notisolate the measuring equipments which can not
accept high pressure.accept high pressure.
• Purging of the DE &NDE takes place alternativelyPurging of the DE &NDE takes place alternatively
with a gap of 15 minutes after which it is reset inwith a gap of 15 minutes after which it is reset in
auto and the other set of lines are purged so thatauto and the other set of lines are purged so that
actual DP from at least one side is obtained.actual DP from at least one side is obtained.

13. MEASURING CIRCUITMEASURING CIRCUIT
• This introduces instrument air continuously in at a lowThis introduces instrument air continuously in at a low
velocity of .3 to .5 meter /sec for measuring .Dependingvelocity of .3 to .5 meter /sec for measuring .Depending
upon the level of coal in the mill different back pressures isupon the level of coal in the mill different back pressures is
applied in the different lines hence a differential pressureapplied in the different lines hence a differential pressure
will exist between the bottom (+) &upper (-) lines whichwill exist between the bottom (+) &upper (-) lines which
gives a direct indication of coal level in the mill. The (+) &gives a direct indication of coal level in the mill. The (+) &
(-) lines are connected to the transmitter DPT 601 &DPT(-) lines are connected to the transmitter DPT 601 &DPT
603 provide a 4-20 mA signal for level indication in the603 provide a 4-20 mA signal for level indication in the
UCB.UCB.
• The pressure in the buffer tank is always maintained 80%The pressure in the buffer tank is always maintained 80%
above mill pressure. The pressure transmitter continuouslyabove mill pressure. The pressure transmitter continuously
track the DP across buffer tank and mill inlet toptrack the DP across buffer tank and mill inlet top
measurement left &right lines and generates a 4-20 mameasurement left &right lines and generates a 4-20 ma
signal for the controller .The controller is given a set pointsignal for the controller .The controller is given a set point
of 80% and depending upon the difference between theof 80% and depending upon the difference between the
actual &set point it controllers the opening and closing ofactual &set point it controllers the opening and closing of
control valve DPC 601.control valve DPC 601.

14. NOISE SENSORNOISE SENSOR
• There is a noise sensor installed in theThere is a noise sensor installed in the
bottom of the mill .bottom of the mill .
• The noise in the mill indicate the level ofThe noise in the mill indicate the level of
coal .higher the noise lesser will be the levelcoal .higher the noise lesser will be the level
of coal & vice versa.of coal & vice versa.
MICRO
PHONE
AMP
LIFIER
BAND
PASS
FILTER
AMP
LIFIER
SIGNAL
TO
DDCMIS

15. SOLIN
OID
BUCKET
LIMIT
SWITCH
PSL
2 KSC
AIR
FILTER

16. THANK YOUTHANK YOU