Feeder Calibration

ORISSA POWER GENERATION CORPORATION LTD.IB THERMAL POWER STATION, BANHARPALI

STANDARD MAINTENANCE PRACTICEFEEDER CALIBRATION

Document No: SMP / C&I – 29

Filed At: Control & Instrumentation Dept

The purpose of the SMP - Feeder Calibration is to train and guide

maintenance personnel to ensure safe and efficient maintenance of the

system.

Responsibility: Team Leader, C&I

Other Department To Be Intimated: (Main Plant Operation, Mech. Maint)

Details of Hazards Involved

1. Dust

2. Noise

3. Fall from height

4. Electric shock

5. Falling Objects

Safety Precautions Required

1. Ensure use of PPEs while working

2. Put the feeder run switch in off position at field (local panel).

3. Put the feeder in local mode at remote panel in MCR

Permit Type: Permit To Work Order

Permit Approving Authority: Shift in charge (Main Control Room)

Isolation Procedure

1. Close feeder inlet chain gate.

SMP - Feeder Calibration 1

2. Empty the coal from feeder belt by keeping the R.C. Gate open

3. Put mill in barring and start feeder.

4. After emptying the coal from feeder belt, R.C. Gate should be made

close.

5. Open the four doors with the help of people from Mechanical

Maintenance Team and carry out the tracking & leveling.

T & Ps including special ones

1. Multi meter.

2. Watch maker screwdriver.

3. Feeder calibration kit that includes.

(i) Two nos calibration pick up unit.

(ii)Three cables.

(iii) One calibration unit.

4. Four nos. of retro-reflecting tape.

5. One no. of chalk.

6. Hand Lamp

Frequency of maintenance: Annual Outage / During Tripping / In case of

failures.

WORK INSTRUCTIONS PROCEDURE

1. Apply 4 strips of retro-reflecting adhesive tape from calibration kit to the

right-toothed segment of the feeder belt. Each strip should be oriented

vertically on the belt curb and located entirely between two flexing slits

in the curb, rather than spanning over a slit. Place the 4 strips at

approximately equal distance from each other, to assure that they are

spaced at a distance greater than one calibration probe span length from

each other.

2. Open the feeder electronics compartment.

3. The calibration should be in off position.


4. Remove the two bolts adjacent to the weigh span roller grease fittings for

insertion of the calibration probes.

5. Remove the protective caps from the calibration probes and insert one

probe into each access port in the feeder body, taking care to align the

detention pins on the probe with the machined holes in the feeder.

Although the two probes are not dedicated to a particular location, note

that the probe location nearest to the feeder inlet is designated START

OR A & the probe location nearest to the discharge is designated STOP

OR B.

6. Connect the two probe cables to the probes and to the calibration

instrument.

7. Connect the feeder cable to both the calibration instrument and the

feeder.

8. Verify that the calibration weight is off the weighing roller. Start the

feeder by placing the feeder mode selector switch (SSF) in the local

position and the local mode switch (SLF) to Run. Maintain the speed at

900 + 200 RPM. The speed setting is not critical, but the higher RPM

setting speeds up calibration procedure.

9. Set the calibration instrument as follows.

i. Mode selector switch to the belt position.

ii. Feed rate code digit switches to the same feed rate code as set on

the thumb wheel switches of the load cell amplifier card, A2, in the

feeder control cabinet electronics assembly.

iii. Event select to 4, the no. Of reflective tape markers on the belt.

10.Press the Reset button on the calibration instruments. After a delay, the

display starts to accumulate counts and stops counting after one complete

belt revolution.

A. After every cycle, the instrument stores this number and uses it as a

reference to adjust the tare signal. Press the reset button to repeat this SMP - Feeder Calibration 3

step several times, a repeatability of + 10 counts should be obtained.

This gives an indication that the instrument is operating correctly.

Poor repeatability indicates that one of the following conditions may

exist; an incorrect no. of reflective tapes may have been installed on

the belt, the tapes are closer together than the calibration probe span,

the weigh span is located beneath the drive pulley at above the inlet

belt support roller or there may be binding of one or more of the load

cell assemblies. Once repeatability is achieved, do not reset the

calibration instrument before proceeding to the next step.

11.Adjust tare as follows.

A. Place the mode selector switch to the tare position and press the reset

button. After a delay, counts are subtracted from the number stored.

During this test use a DVM to measure the voltage between test points

TP8 (Green) and TP9 (Black) on the load cell amplifier card, A2.

After one complete belt revolution, the instrument stops subtracting.

The result can be positive or negative (indicated by flashing lamp).

Positive number - Tare adjust too low.

Negative number - Tare adjust too high.

12.To adjust the tare signal, two potentiometers are provided on the load cell

amplifier card, A2 coarse adjust (R33) and fine adjust (R 34). For each, a

clockwise turn increases the signal.

13.Continue to readjust the potentiometers as necessary to obtain a tare

reading of Zero ± 5 courts.

14.Engage the calibration weight.

15.Adjust the span as follows:

i. Place the mode selector switch to the span position.

ii. Press reset and the calibration instrument display will indicate

“100.00”. After a delay, the display will start four counting cycles

and display a final number. The displayed number represents the SMP - Feeder Calibration 4

span calibration error in percent. As before display implies a

negative result.

Error Positive - Increase Span.

Error Negative - Reduce Span.

16.To adjust the span, two potentiometers are provided on the load cell

amplifier card, A2: coarse adjust (R19) and fine adjust (R20). For each a

clockwise turn increases the span.

17.Place the instrument mode selector switch in the Tare Position and

measure the voltage between test points TP8 and TP9 on the load cell

amplifier card, A2.

18.Adjust the voltage by the percentage indicated on the calibration

instrument using the span adjust potentiometer, R19 and R20. Do not

adjust the tare adjust potentiometers, R33 and R34.

19.After the span adjustment is over, disengage the test weight and remove

the calibration instrument and probes from feeder. Calibration is

completed.

20.Control Room Calibration:

Control Panel adjustment:

1. Before adjustment in control panel, the loops are to be made at following

terminals and standard weight i.e. 86.7 Kg is placed on belt.

i. TB No. 5 Terminal No. 50, 51 No coal on belt

ii. TB No. 1 Terminal No. 2,15 No coal on belt

iii. TB No. 1 Terminal No. 7,9 Remote contact from FSSS

2. After making above connections feeder is to be made ON from remote.

a. Apply 0% demand command from A/M station. Observe that feed

rate should be 12 T/H. If not, then adjust minimum rate

potentiometer R 23 of ISF card .


b. Apply 100% demand command from A/M station. Observe that

feed rate should be 60 T/H. If not, then adjust the maximum rate

potentiometer R 45 of ISF card.

3. After adjustment in control panel is over, remove all the

connecting loops and remove the standard weight from the belt.

Checks before release of Permit

1. For defects action should be taken as per the requirement.

2. After ensuring the completion of feeder calibration, the doors are to be

closed, PTW may be returned.

3. All T & Ps and manpower are removed

Revision No & Date

Prepared By Verified ByTechnical Committee

Approved ByDirector (Operation)

S. Mohanty


Documents

Feeder Calibration