This document describes the hydraulic control system for adjusting the gap between two rollers on a roller press machine. Key points: 1. Hydraulic pumps, valves, cylinders and accumulators are used to push and retract the movable roller to control the gap. 2. The gap is adjusted through a multi-step startup process that retracts the roller to a preset minimum gap before starting material flow. 3. Once running, pressure control circuits use proportional valves to balance hydraulic pressure against material pressure and maintain the target gap setting.

1. Hydraulic control ROLCOX
of the rolls
1
Fixed Roller
Movable Roller
Left Right
Hydraulic oil tank
Pump HT 1 M 01
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2. HT 1 V 3/4 Prop. valve right
HT 1 V 1/2 Prop. valve left
HT 1 V 09 Emergency valve
HT 1 V 10
Pressure decrease valve left
( one way valve )
HT 1 V 11
Pressure decrease valve right
( one way valve )
HT 1 V 08 Retraction cylinder valve
HT 1 M 01 Hydraulic pump
HT 1 V 07 Bypass valve right
HT 1 V 06 Bypass valve left
Left Right
Retraction cylinder
Fixed Roller
Retraction cylinder
Hydraulic oil tank
Movable Roller
Press cylinder
V 09
V 08
Pump HT 1 M 01
V 07V 06
V 10 V 11
2
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V 1/2 V 3/4

3. + Bearing dist. = 0 mm
RP - Frame
Gap sensor Limit switch
Press cylinder
Fixed Bearing
3
Roller dist. = 10 mm fix
Gap = 10 mm
Movable Bearing
Next
Retraction cylinder
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measured by
Distance block

4. This is the point where the bearing distance is 0.
For the gap measuring this point is 4 m Amp.
The bearing blocks are fixed in a way that the
rollers can never touch each other physically
Fixed Roller
Movable Roller
Left Right
Distance pieces
Movble
Roller
Fixed Roller
Left Right
Distance between the bearings used as lower
limit for the pressure control.
If distance is less pressure control will be
deactivated.
Roller distance 10mm = Gap 10 mm
Roller distance 10 mm
+ Bearing dist. 15 mm
= Gap 25 mm
Gap = 10 mm
Set points 4
0 mm ( Bearing distance )L 0mm
GAP > L min Pressure control ON
normal operation
L min 15 mm ( Bearing distance )
Next
Movable Roller
Next
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GAP < L min Pressure control OFF
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Gap = 25 mm

5. L min
Movable
Roller
Fixed
RollerLeft Right
Gap = 35 mm
Movable
Fixed
RollerLeft Right
Gap = 45 mm
L2
Parameter set in the PLC. Set only once.
Range from 5.0 to 30.0 mm
Actual set point 25 mm
( Set point for material feeding )
Roller distance 10 mm
Set points
L min
+ L2 + 10 Bearing dist. 35 mm
5
Next
= Gap 35 mm
+ L2 Bearing dist. 25 mm
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L2
+ 10 mm
Until this value the rollers are pushed back
during start up the main motors.
= Gap 45 mm
Roller distance 10 mm
Next
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6. Movable
Roller
Fixed
RollerLeft Right
Gap = 65 mm maximum
Roller distance 10 mm
+ Bearing dist. > 55 mm
= Gap > 65 mm
Limit switch
Maximum distance allowed
between the bearings. ( 65 mm Gap )
Determined by a mechanical switch.
Over 65 mm gap the roller press will
stop with max. gap alarm.
Set points
6
Normal operation
Movable
Roller
Next
Next
Ok.
L2
L min
+ 10 mm
Movable
Roller
Movable
Roller

7. Movble
Roller
V 09
V 08
Hydraulic oil tank
Pump HT 1 M 01
Press cylinder
After reaching of L2 + 10 mm, the main drives will be
started one by one.
7
Start RP group
At every start the emergency valve is energized
to close the hydraulic circuit.
The movable roller will be moved
by the retraction cylinders to L2 + 10 mm = 45 mm
To release the oil of the main cylinders the bypass valves
and the pressure decrease valves are energized (opened).
This will occur with standing rollers.
Next
V 06V 06 V 07V 07
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NextNext
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V 09
Movable
Roller
Left
Fixed
Roller Right
Gap = 45 mm
Next
Next
L min
L2
+ 10 mm
V 11
V 3/4
V 10
V 1/2
V 10
V 06V 06 V 07V 07
V 3/4V 1/2
V 07V 07V 07V 07V 06V 06V 06V 06
V 11
Valve closed
Valve open

8. Next
V 08
Start RP group
Retraction cylinders are drawn back by springs.
After L2 will be reached in pre bin the shut off Gate will be opened
to release material flow to the rollers.
8
Next
L2 Gap = 35 mm
In case if during moving back the movable roller an oil pressure
is measured of more than 40 bar ( normal < 40 bar ), the start will
be interrupted by an alarm signal.
Fault has to be acknowledged at the roller press after checking.
Possible causes:
Material between the rollers.
Disturbance in the hydraulic circuit.
Roller can not move free.
After bearing distance is on both sides L2 the roller press group will
be released and feeding of the pre bin can be started.
Next
Next
Movble
Roller
V 09
Hydraulic oil tank
Pump HT 1 M 01
Press cylinder
V 06V 06 V 07V 07V 09
Movable
Roller
Left
Fixed
Roller Right
Gap = 45 mm
V 10
V 3/4V 1/2
V 07V 07V 07V 07V 06V 06V 06V 06
V 11
After this the movable roller will be pushed back to
L2 by the main cylinders from 45 mm to 35 mm.
This happens with running rollers.
V 08
Next
V 06V 06 V 07V 07
V 11V 10
V 1/2 V 3/4V 1/2 V 3/4
Gap = 35 mm
Pump stops and valves will be closed.

9. V 3/4V 1/2 V 3/4V 1/2
V 09
V 08
V 07V 06
Press cylinder
Left RightFixed Roller
The proportional valves will increase pressure to the
main cylinders up until the set point.
Hydraulic pump start.
9
Hydraulic oil tank
Pump HT 1 M 01
Next
Start Pressure control
After the start program is ready the pressure
control will start automatically.
After opening of the shut off gate there will get
material between the rollers.
Next
Movable Roller
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V 11V 10

10. Pressure control
By the intake behaviour of the running rollers
combined with the pressure of the column ( gap )
of material on the rollers the material flow will
tend to press the rollers apart.
Hydraulic oil tank
V 3/4V 1/2
V 08
Pump HT 1 M 01
V 09 V 07V 06
Left Right
Press cylinder
Movable Roller
Fixed Roller
When the hydraulic reaches the
value set point-tolerance
the proportional valves will be closed
and the pump will stop.
10
Pres.Set point
At this value the material counter pressure
and the cylinder pressure will be on balance.
- 10 bar
+ 10 bar
V 1/2 V 3/4
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V 11V 10

11. Accumulator
Gas ( N2 ) Pressure = 90 bar100 bar
135 bar
125 bar
115 bar
Set point 125 bar
Hydraulic oil tank
V 3/4V 1/2
V 08
Pump HT 1 M 01
V 09 V 07V 06
Left Right
Fixed Roller
Press cylinder
Movable Roller
90
bar
Start up
< 90 bar
Pressure control
Pressure variations with in tolerance will be
compensated by the N2 accumulators.
11
V 1/2 V 3/4
100
bar Next
125 bar
Next
V 11V 10

12. Note: This can happen at both sides at the same time but also
on one of both sides, depending of pressure measurement on
this side.
V 3/4V 1/2
V 10
V 08
Hydraulic oil tank
Pump HT 1 M 01
V 09 V 07V 06
Fixed Roller
Left Right
12
They will remain open until the set point
operation pressure + tolerance is reached.
After this the valves will be closed.
Pressure control
When the hydraulic exceeds the pressure (value)
set point + tolerance the proportional valves will open and the
pressure decrease valves will be opened (energized).
135 bar
125 bar
115 bar
4 m Amp
Characteristics of proportional valves.
100
%
100
%
12 m Amp
0 %
Proportion valve
pressure
increase
20 m Amp
Proportion valve
pressure
decrease
Set point
30 %
30 %
8 m Amp
V 3/4
Next
Press cylinder
Movable Roller
Next
Next
V 11V 11V 10

13. Pressure control
When the hydraulic gets beneath the pressure (value)
set point – tolerance the proportional valves will be
opened and the pump will start.
V 3/4V 1/2
V 08
Hydraulic oil tank
Pump HT 1 M 01
V 09 V 07V 06
V 10 V 11
Fixed Roller
Left Right
Press cylinder
Movable Roller
13
This will remain so until set point operation pressure – tolerance
has been reached.
After this the valves will close again and pump will stopped.
In this example on one side.
135 bar
125 bar
115 bar
Characteristics proportional valves.
100
%
100
%
12 m Amp
0 %
4 m Amp
Proportion valve
pressure
increase
20 m Amp
Proportion valve
pressure
decrease
80 %
80 %
18,4 m Amp
V 3/4
Next
Next
Next
V 11
V 10

14. A certain deviation is due to non homogenate mixture
of raw materials (coarse, fine, wet, dry).
Gap (l) Gap (r)=
V 3/4V 1/2
V 08
Hydraulic oil tank
Pump HT 1 M 01
V 09 V 07V 06
V 10
Left Right
Fixed Roller
Gap (r)
Gap (l)
Gap(l) Gap(r) =- Gap(diff)
Gap(diff) > Gap(diff)toll.
Correction will be done first on the side with the bigger
gap by pressure increasing.
Correction is permitted until operation pressure + 5 bar.
14
If this value is exceeded the skewing will be corrected.
Gap correction
A deviation in gap width between left and right
in permitted until a preset value.
This will remain so until gap - difference - tolerance
has been reached. Set point 4 mm.
After this the valves will close again and pump will stop.
Presscilinder
Movble
RollerPresscilinder
Movble
RollerPress cylinder
Movable Roller
V 1/2
Next
Next
Next
V 11V 10

15. V 3/4V 1/2
V 10
V 08
Hydraulic oil tank
Pump HT 1 M 01
V 09 V 07V 06
Movble
Roller
Gap (r)
Right
Fixed Roller
Left
Gap (l)
If skewing is after this correction still not within
tolerance limits, at the side with the smallest gap,
pressure will be released.
15
Gap correction
This will remain so until gap - difference - tolerance
has been reached. Set point 4 mm.
After this the valves will close again.
PresscilinderPress cylinder
Movable Roller
V 3/4
Next
Next
V 11V 11V 10

16. V 1/2 V 3/4
After this correction pressure control will be reactivated.
If pressure difference between left and right exceeds a
preset maximum ( 30 bar ) an alarm will be generated
and pressure will be released at both sides.
Gap (diff) < Gap (diff)toll. ( 4 mm )
V 08
Hydraulic oil tank
Pump HT 1 M 01
V 09 V 07V 06
V 1/2 V 3/4
Left Right
Fixed Roller
L(r)L(l)
Presscilinder
Movble
Roller
16
Gap correction
and Pressure Control
Press cylinder
Movable Roller
Next
Next
V 11V 11V 10V 10
Next

17. Current control
By means of to much adjusting of operation pressure or
due to changing material properties
the electrical load of the main drives can become to high.
If this load exceeds a preset maximum the pressure will
be reduced.
V 08
Hydraulic oil tank
Pump HT 1 M 01
V 09 V 07V 06
Left Right
Fixed Roller
17
After this the pressure control will be reactivated.
V 1/2V 1/2 V 3/4V 3/4
This will last until the movable roller reaches
L2 + 10 mm = 45 mm gap
or until the drives get below operation load.
Press cylinder
Movable Roller
Next
V 11V 11V 10V 10
Next

18. V 10
V 11
RP Group stop
The Pressure decrease valves will open,
the proportional valves will open,
and the emergency valve will open.
Hydraulic oil tank
Pump HT 1 M 01
Left Right
Fix Roller
18
Press cylinder
Movble
Roller
Fixed Roller
Movable Roller
V 08
V 09 V 07V 06
V 1/2V 1/2 V 3/4
V 09
The rollers will due to material pressure move apart
until L2 is reached on both sides or after time limit.
Roller press will stop after 30 sec.
At a stop of the roller press (desired or undesired)
the RP - slide gate will close and
stopped the material feed to the RP.
Next
The Pressure decrease valves will close,
the proportional valves will close,
and the emergency valve will open.
Next
Next
V 11
V 3/4
V 10V 10

19. Roller press
Dosing Gate
min. Pos.
open
Open
the
Dosing
Gate
Dosing
Gate in
Movable
Roller
Fixed
Roller
19
close
RP - Bin
Slide Gate.
opened
max. Pos.
Dosing
Gate
Last

20. 20