This document provides instructions for calculating mill settings for a sugar cane mill. It defines key terms like mean effective diameter and work openings. It lists required data like crush rate, fiber percentage, roller dimensions, and speed. Formulas are provided to calculate the fiber rate and determine the discharge, feed, and trash plate work opening sizes based on this data and adjustment ratios from provided tables. An example calculation is shown for a specific mill. The resulting recommended mill settings for the discharge, feed, and trash plate openings are presented in a table.

1. J E G A D E E S H . M
E N G I N E E R
I N D I A N C A N E P O W E R L I M I T E D
MILL SETTING

2. DEFINITIONS :
Mean effective diameter of Top Roller D
= (Outside diameter of roller - Depth of grooving)
Work Opening : Actual opening between any two points on the
surface of the two rollers in their common
axial plane when the mills are in operation.
Mill Setting opening : Actual opening between PCD to PCD of concerned
opening rollers, when mills are at rest and empty.

3. DATA REQUIRED FOR MILL SETTING
C = Crush rate desired in tons (Metric)/hr.
f = fibre % cane
D = Mean effective diameter of Top Roller (mm)
L = Length of the roller (mm)
n = Speed of rotation (rpm) {To be determined based on
No. of rollers in mill tandem, crush rate, preparatory
index, specific fibre loading, power availability at setting
speed etc.}

4. PROCEDURE FOR CALCULATION OF MILL SETTING
V = Mill Roller surface speed
 x D x n
V = ------------- m/min.
1000
Calculate fibre rate 'F' as per formula given below:
F = C x f x 0.166 Kg / min.

5. Calculate the discharge work opening as
per formula given below:
F x 63429.6
Discharge work opening = ---------------------- mm.
S x V x L
Where ‘S’ denotes the Fibre Index to be read from Table – 1.
Actual Discharge Work Opening = (Discharge work opening – Roller
Rise) mm.
The 'Roller Rise' considered for the mills shall be taken as per Table 2.

6. Mills 12 Roller Tandem 15 Roller Tandem
2nd of `B’ Tandem 38 40
3rd of `B’ Tandem 45 46
4th of `I’ Tandem 52 52
TABLE – 1
Values of Fibre Index ‘S’
Mill No. 12 Roller Tandem 15 Roller Tandem
Roller Trash Roller Trash
2nd of `B’
Tandem
7 8 7 8
3rd of `B’ Tandem 6 7 6 7
4th of `I’ Tandem 5 6 6 6
TABLE – 2
ROLLER RISE

7. Calculate the Feed work opening as per formula given below:
Feed work opening = Discharge work opening X (Ratio of feed
to discharge opening) mm.
The Ratio of Feed to Discharge opening for the mills shall be taken as per
Table 3.
Actual Feed Work Opening = (Feed work opening – Roller Rise) mm.
Mills 12 Roller Tandem 15 Roller Tandem
2nd of `B’Tandem 2.00 2.05
3rd of `B’Tandem 2.15 2.10
4th of `I’Tandem 2.20 2.15
TABLE – 3
Ratio of Feed to Discharge Opening presumed for calculations

8. Calculate the Trash plate work opening as per formula given
below:
Trash Plate work opening = Feed work opening X (Ratio of trash
plate to
feed opening ) mm.
The Ratio of Trash Plate to Feed opening for the mills shall be taken as
per
Table 4.
Actual Trash Plate Work Opening = (Trash Plate work opening – Roller
Rise)mm.

9. Mill No. 12 Roller Tandem 15 Roller Tandem
2nd of `B’Tandem 1.70 1.75
3rd of `B’ Tandem 1.80 1.80
4th of `I’Tandem 1.80 1.85
TABLE – 4
Ratios of trash plate to feed opening presumed for calculations

10. SPECIMEN CALCULATIONS

 DATA

 Crushing Rate (c) : 250 Tons (Metric) of Cane per hour (TCH)

 Fibre % Cane (f) : 13%

 Roller Length (L) : 78 1/8 inches

 Mill Size (D x L) : 39 inches O.D. x 78 1/8 inches

 Speed selected (n): 5.5 r.p.m.

 Now calculate the factor 'F' for the above conditions
  x D x n 3.1416 x 915 x 5.5
 V = --------------- m/min. = ------------------------
 1000 1000
 = 15.81 m / min.

11. Calculate factor 'F' as per formula given below:

 F = C x f x 0.3733 lb / min.

 = 250 x 13 x 0.166
 = 539.5 Kg / min.

12. Calculation of Discharge work opening
 F x 63429.6
 Discharge work opening = -----------------mm.
 S x V xL
 For value of ‘S’ see table - 1
 539.5 x 63429.6
 = ------------------------
40 x 15.81 x 1980

 = 27.3 mm


13. Calculation of Feed work opening
 Feed work opening = Discharge work opening X
 (Ratio of feed to discharge
Opening)
 For value of ‘Ratio’ see TABLE-3

 = 27.32 x 2.05

 = 56 mm

14. Calculation of Trash plate work opening
 Trash Plate work opening= Feed work opening X
(Ratio of trash plate
to Feed Opening)
 For value of ‘Ratio’ see TABLE-3

 = 56 x 1.75

 = 98 mm.

15. Mill No. Feed Side Opening
(mm)
Discharge Side Opening
(mm)
Trash Plate
Opening
(mm)
2nd of `B’
Tandem
56 27.3 98
3rd of `B’ Tandem 50 23.8 89.8
4th of `I’ Tandem 45 21 83.7
The discharge, feed and trash plate openings for all the four mills are
tabulated below.

16. Mill No. Feed Setting =
Actual opening- roller
rise
Discharge Opening =
Actual opening- roller
rise
Trash Plate Setting =
Actual opening- roller
rise
2nd of
`B’
Tandem
56 – 7 = 49 27.3 – 7 = 20.3 98 – 8 = 90
3rd of `B’
Tandem
50 – 6 = 44 23.8 – 6 = 17.8 89.8 – 7 = 82.8
4th of `I’
Tandem
45 – 6 = 39 21 – 6 = 15 83.7 – 6 = 77.7
The ‘Mill Settings’ for all four mills can be calculated as given
below:
Mill Settings in mm
The mill settings calculated should be rounded off for practical adjustment
purpose.