JPMA, Mill Coupling used in Suigar Industry. Mill coupling is installed for torque transmission from the final speed reduction gear/ Planetary Gear to the mill top roller. In spite of the numerous shortcomings of the tail bar system, it was universally used simply because there was no better alternative before the introduction of Rope coupling / JPMA Mill Coupling. JPMA Mill coupling completely replaces the conventional tail bar and square coupling assembly.

1. Manufactured and Marketed by
Jyoti Sugar Engineering Pvt Ltd.

2. Mill coupling is installed for torque
transmission from the final speed
reduction gear/ Planetary Gear to the
mill top roller.
In spite of the numerous shortcomings
of the tail bar system, it was universally
used simply because there was no better
alternative before the introduction of
Rope coupling / JPMA Mill Coupling.
JPMA Mill coupling completely replaces
the conventional tail bar and square
coupling assembly.

5. JPMA Coupling
JPMA Coupling
Tail bar couplingTail bar coupling
Tail bar coupling

6. Improves extraction performance of the mill due to
free floating of top roller.
Reduces final bagasse moisture on the last mill.
Misalignment between square end of the gear shaft
and the top roller either due to tilting of the top roller
or initial alignment error in installations is fully
absorbed by the JPMA mill coupling.
Reduced torque and power consumption at the drive side due to
reduction in losses.
The use of this coupling is particularly advantageous
when the space between the gearbox and mill is
limited.
Breakage of crown pinion and top roller is completely eliminated.
Also there will be no tail bars or square coupling breaking due to
their absence.
Negligible maintenance.

7. The coupling uses two yokes with
back sandwich plates one on each
shaft connected with Compression
strut.
Yokes are installed between in such
a way that slings transfer the loads
from the driving yoke via the
compression strut to the driven
yoke.
This configuration allows shaft and
coupling to have lateral, axial &
angular displacements.
This composite mechanism eliminates frictional resistance
(improving torque transmission efficiency), with no axial thrusts
and no bending moment loads on drive shaft.

8. Gear side Back sandwich plate & Driving yoke
Mill side Back sandwich plate and driven yokes.
A “compression plate” with head clevis
 Slings that transmit
the torque.
 Reversing mechanism
with reversing ropes.

9. JPMA can design couplings ranging from 200 kNm to 3400 kNm
Sr.No Mill size in Inches. Coupling size. kNm
1 30 x 60 550
2 33 x 66 700
3 36 x 72 900/1200
4 40 x 80 1200 /1400
5 42 x 84 1400/1600/1800
6 45 x 90 2100/2200
7 50 x 100 2400
The highest peak (for start up & jam up) is 115% of Nominal torque.
Usually we are compelled to size the coupling based on specified power
& the rated full speed of the mill. But preferably it should be on Mill size.

10. 1 West Kenya Sugars Kenya
2 Thyssen Krupp a/c Sukhari Sugar Co. Kenya
3 Kwale International Sugar Co. Kenya
4 New Halfa Sugar Factory Sudan
5 KCP, Finchaa Ethiopia
6 NHEC A/C Tendaho sugar Factory Ethiopia
7 ISJEC, Wonji Shoa sugar Factory Ethiopia
8 M&H USA Enterprise. Mexico
9 BISCOM INC Philippines
10 M&H USA Enterprise USA

11. S.No Description Tail bar Coupling JPMA Mill Coupling
1 Misalignment capability Marginal Can take axial displacement, angular
misalignment along with end float
more than Tail bar coupling & can
handle all simultaneously without
breaking.
2 Ratio of (Bending moment)/
(Drive torque)
100% ≤ 5%
3 Amplitude of the cyclic bending
Stress
105 Mpa ≤5 Mpa
4 Bearing at Gear side & Mill side Wear out faster due to
end thrust
No thrust & no wear.
5 Vibration on the driving gear
plummer block
Vibrations are
moderate to heavy
Vibrations are eliminated
6 Gear teeth Surface Due to thrust loads
gear teeth surfaces
show signs wearing
out faster
No uneven wear pattern on gear.
Normally improves after installation.
7 Extraction Performance Obstruct the free
floating of the top
roller hence extraction
is less
Does not impose any constraining
thrust on the top roller shaft. Hence
free floating of top roller & improved
juice extraction performance.
8 Bagasse Moisture Since top roller
floating is restricted
moisture in bagasse is
higher.
Due to floating of top roller final
bagasse moisture will be lower.

12. S.No Description Tail bar Coupling JPMA Mill Coupling
9 Torque & Power Consumption Tail bar & Coupling
cause loss of Torque &
Power.
Since it removes the constraint on free
floating of top roller the mill is able to
operate with reduced friction losses &
hence saving in the operating torque
requirement of the mill & hence reduction
in power consumption.
10 Misalignment between Gear Shaft &
mill shaft
Causes damages to top
roller, Crown pinion &
drive system. Abnormal
wear & tear of the final
gear
Misalignments fully absorbed by JPMA
mill coupling, as a result no significant
lateral thrust or bending moment is
transmitted to the drive system.
Abnormal wear & tear to final gear is
eliminated.
11 Mill stoppages Chokes caused by tail
bar coupling restraints
No chokes due to this coupling since top
roller floating freely.
12 Space requirement Space between Gear
shaft & Mill shaft
required more
Can be accommodated in minimum space
between Mill & Gear shaft.
13 Initial Installation cost Less Higher
14 Payback period - Considering the above advantages it
justifies the initial higher cost of the
coupling.
15 Service Factor Mechanical construction has 1.75 S.F &
Rope has minimum of 2 based on nominal
design Torque.

13. Instructions on Pre-installation work required for Mill
coupling
Shaft squares should be new or built up and machined square to a
tolerance of +0 to 0.2 mm.
The square and end-faces of the shafts to be connected by the
coupling are to be drilled and tapped to match the round sandwich
plates and each supplied with suitable high-tensile steel bolts.
For ease of installation, it will be useful to make up two 400 mm long
steel rods with thread suiting to square end shaft at one end 50 mm
long to suit the holes drilled in the ends of the shafts.
Check that the friction pads are correctly fitted to the front and rear
faces of the hub plates.
Pre-check the fit of the hub-bores on their respective shafts and grind
the bores where necessary to ensure 4-line contact on the shaft
squares. Contact lines should be approximately 40 mm from the
corners after tilting to approx. 15 deg.

14. S. No Item Quantity
1 One pair of main driving ropes, Polyester
slings
1 working set / Mill coupling i.e
12 Nos or 8 Nos.
2 Wear pads 60 mm X 20 mm - 16 Nos.
3 Hex head screws M20 X 75 mm long - 16 Nos.
4 Pair of 13mm reversing ropes each with two
“cross by” clamps
- 2 Nos.
- 12 Nos

15. Care to be taken during installation of JPMA
Mill coupling

16. After installation of Mill coupling please observe
no wear & tear what so ever of the gear bearing.
Power consumption of the mill is reduced by 25
kW.
mill top roller started floating more freely there by
improving extraction performance of the mill &
vibrations on the driving gear Plummer blocks are
completely eliminated.
Completely eliminates frictional resistance caused
by tail bar.
No signs of pitting or uneven wear due to thrust
load on gear teeth surface.

17. With free floating of top roller mill operates at the
design settings & optimum hydraulic pressure &
consequently perform efficiently.
The mill couplings are built to transmit torque &
allow axial, angular& lateral misalignments of the
shaft w/o damaging the parts. These feature result
in reduction in crushing ,axial & bending loads,
which are harm full for all mill & gear components.

18. Slide the appropriate square bore Rear sandwich plate onto the shaft square, with chamfer side first
until it comes up hard against the back of the square.
Slide on the appropriate Yoke until it is hard up against the square bore sandwich plate already fitted.
Screw the two 400mm long steel rods into the two uppermost holes drilled in the end of the shaft.
Using the rods as a guide, slide on the appropriate round outer sandwich plate until it comes up hard
against the inside of the hub.
Loosely fit four bolts through the holes in the round plate and nip up hand tight but do not tighten to
full seating – torque at this stage.
Check that the plate does not come up and against the end face of the square shaft. (the gap should
be approximately 5 mm). If it does, please check dimensions and ensure that components have not
been mixed up. If there has been a mistake in manufacture, revert to us to check dimensions and
make recommendations about corrective action.
If all is well, remove the two threaded rods and replace with bolts and nip up. Also fit the two other
bolts. Note: do not tighten at this stage.
If the mill shaft YOkE has been fitted on the floor, install in the mill (you may have to turn the gear
shaft/gearbox by hand until the gear shaft/gearbox side yoke is vertical) or Using the same procedure
as above install the second YOkE on other square.
Turn both the gear shaft /gearbox and mill shafts until the yokes form an X, with the tongues of the
heads facing one another at the top and bottom.
Install one main driving rope between the lower heads to be connected. The rope should hang
loosely in the form of a cradle.
The COMPRESSION STRUT now needs to be installed between yokes in such way that slings transfer
the load from the driving yoke via the compression strut to the driven yoke.
Rotate the driving and driven shafts into a flattish cross-formation, such that the driving pins (on the
gearbox yoke) are nearly touching the driven pins on the mill yoke, when driving forward. The
reversing brackets should nearly touch one.

19. Before installing the compression-strut, first fit two pins onto one end, installing three/two
Polyester slings around each pin. Note, immediately before fitting the pins, liberally apply
Molybdenum -Disulphide Grease inside the strut clevis-holes and the inside of the spools.
Secure the pin using cap-screws provided.
Using a sling from each top pin, suspend the compression-strut vertically and lower it
through the gap between the yokes.
When through the gap, fit the lower pins on the compression strut, installing three/two slings
into each clevis (as above, don’t forget to grease clevises and spools).
Bar the drive backwards to make the cross more equal, and fit the pins into the lower yoke-
ends, at the same time fitting the nearest three slings from the compression-strut into the
clevises in the yoke ends.
Repeat this procedure in fitting the upper slings to the opposite yoke ends.
Make sure ALL the slings are not twisted and lie flat inside the spools (they are made
generally rectangular in shape).
Bar the drive forward to lightly tension the slings before following the next step.
INSTALL THE REVERSING ROPES by passing them twice through the reversing-brackets
at the backs of opposing yoke-heads, in the form a flattish oval, before fitting the Crosby
Clamps. Do not make them too tight or else they will not permit any misalignment without
themselves breaking.
Torque-up the high-tensile steel bolts in the front sandwich-plates to their relevant seating
torque (provided by the supplier).
Drive the mill forward lightly and check security of all bolts.
Clean the exposed pin-ends of grease and fit the back-up polyester –slings in parallel with
the already-fitted main driving slings, and fit the retaining plates. Note, the back-up slings
should be slack.

20. Sr. No. Description
With
Rope
coupling
Without
Rope
coupling
1 Plant Capacity tch 273
2 Fiber % 15
3 Season days 150
4 Mill Size 40' x 80' 4 Nos
5
Input power at Shaft kW / hr 1100
As per mill
Programme
6 Overall Efficiency % 0.85 0.77
7 Cosumed Power kW / hr 1294 1429
8 Savinig Power kW / hr 134
9
Total Power Saving per
Season kW 484034
10 Total Cost Saving Rs 2420168 @ 5 Rs/kW
11 JPMA Coupling Cost Rs 6000000 4 Nos
12 Pay Back Period Yrs 2.5
Pay back period