Detailed functionof hydraulic system in OK and atox mills.pdf

Hydraulic Function of VRM Atox Mill

1. ©2008 Eaton Corporation. All rights reserv ed.
FLSmidth
ATOX Mill Hydraulic System

2. ATOX MILL

3. HYDRAULIC FUNCTION

5. HYDRAULIC FUNCTION

6. HYDRAULIC FUNCTION

7. HYDRAULIC FUNCTION

8. HYDRAULIC FUNCTION -ACCUMULATOR

9. HYDRAULIC FUNCTION -ACCUMULATOR

10. HYDRAULIC FUNCTION –SPRING ANALOGY

11. HYDRAULIC FUNCTION -LEAKAGE
P
t

12. HYDRAULIC FUNCTION – PUMP & PLC
P
t

13. HYDRAULIC FUNCTION – PUMP & PLC
P
t

14. HYDRAULIC FUNCTION - LIFTING

15. FULL CIRCUIT

16. TANK & FILTRATION UNIT
FLEXIBLE HOSE
SHUT-OFF
VALVE
WATER
CONTROL
VALVE
PRESSURE
GAUGE
WATER
COOLER
HEATER
ELECTRIC
MOTOR
WATER STRAINER
CHECK
VALVE
FILLING
POINT
THERMOMETER
FILTER
AIR
BREATHER
EMPTYING
POINT
GEAR
PUMP
FILTER
BLOCKED
SWITCHDIFFUSER
SIGHT
GLASS
2400 LITRE TANK
LEVEL
GAUGES
DRAIN VALVE
BAFFLE

17. TANK & MAIN PUMP
FLEXIBLE HOSE
SHUT-OFF
VALVE
WITH
LIMIT
SWITCH
VARIABLE
PISTON
PUMP
FLEXIBLE
HOSE
FLOW
METER
HEATER
LEVEL SWITCHES
SUCTION
STRAINER
ELECTRIC
MOTOR
TEMPERATURE
TRANSDUCER
FLEXIBLE
HOSE
PUMP CASE DRAIN

18. CYLINDER & ACCUMULATORS
GAS PRESSURE
SWITCHES
PRESSURE GAUGE
ACCUMULATORS
CYLINDER
TO 2 OTHER
CYLINDERS
CHECK
VALVE
ORIFICE

19. CONTROL VALVES
CHECK
VALVE
CHECK
VALVE
RELIEF
VALVE
UNLOADING
VALVE
CHECK
VALVE
SOLENOID
VALVE
SOLENOID
VALVE
ACCUMULATOR
DRAIN VALVE
DIRECTIONAL VALVES
DIRECTIONAL VALVES

20. SIMPLIFIED CIRCUIT

21. SIMPLIFIED CIRCUIT
R R RFF

22. SOLENOID PILOT VALVES
A B Bx
A
B
Bx
Valves 53 & 64 ensure
that the highest pressure
in the system is used as
pilot pressure.
F FR R R

23. SOLENOID PILOT VALVES - LOWERING

24. SOLENOID PILOT VALVES - LIFTING

25. SOLENOID PILOT VALVES – DECREASING GRINDING PRESSURE

26. ROLLERS LIFTING
Y1 Y2
Rollers are lifted off
the grinding bed for mill
start-up to reduce
excessive vibration.
81 82

27. ROLLERS LIFTING
Y1 Y2
Valve 61 ensures a
minimum pressure in line
A which prevents full
discharge of the
accumulators.
81 82

28. ROLLERS LIFTED
Y1 Y2
Valve 61 is set to a
pressure 20–30 % higher
than the accumulator
pre-charge pressure.
Pump remains running while rollers are lifted.
81 82

29. ROLLERS LOWERING
Y1 Y2
With valve 61 acting as a
counterbalance valve,
the cylinders will lower
at a speed determined
by the pump flow rate.
81 82

30. ROLLERS LOWERING
Y1 Y2
Valve 61 creates a
counterbalance pressure
in line B to prevent rapid
falling of the rollers.
81 82

31. ROLLERS LOWERING
Y1 Y2
When the rollers
contact the grinding
bed, pressure builds up
in line A thus opening
valve 61 fully to relieve
the back pressure in line
B.
81 82

32. ROLLERS LOWERING
The will pump continue
to run until all of the
accumulators are fully
charged to the required
grinding pressure.
Y1 Y2
81 82

33. ROLLERS LOWERED/ OPERATION
When the accumulators
are charged, the pump
drive motor is switched
off.
Y1 Y2
81 82

34. ROLLERS LOWERED/ OPERATION: INCREASING GRINDING PRESSURE
To increase grinding
pressure, the pump is
simply switched on …
Y1 Y2
81 82

35. ROLLERS LOWERED/ OPERATION: INCREASING GRINDING PRESSURE
… which charges the
accumulators further
until the required
pressure is signalled on
the pressure sensor 44.
Y1 Y2
81 82

36. ROLLERS LOWERED/ OPERATION
The pump drive motor is
then switched off.
Y1 Y2
81 82

37. ROLLERS LOWERED/ OPERATION - REDUCED GRINDING PRESSURE
If a lower grinding
pressure is demanded,
New set point for
pressure sensor 44 is
set.
Y2 energises to open
valve 74 & bleed of oil
from the pressure side.
Y1 Y2
81 82

38. ROLLERS LOWERED/ OPERATION - REDUCED GRINDING PRESSURE
Y2 energises to open
valve 74 & bleed of oil
from the pressure side.
Y1 Y2
81 82

39. ROLLERS LOWERED/ OPERATION - REDUCED GRINDING PRESSURE
Solenoid Y2 de-
energises when the
pressure has dropped to
the required level.
Y1 Y2
81 82

40. ROLLERS LOWERED/ OPERATION - REDUCED GRINDING PRESSURE
A reduction in grinding
pressure could be
required for example if
there is a large lump size
on the grinding bed.
Y1 Y2
81 82

41. ROLLERS LOWERED/ OPERATION - EXCESS PRESSURE RELIEF
Pressure sensor 44
signals the excess
pressure.
Y2 energises to open
valve 74 & bleed of oil
from the pressure side.
Y1 Y2
81 82

42. ROLLERS LOWERED/ OPERATION
Solenoid Y2 again de-
energises when the
pressure has reduced to
the required level.
Y1 Y2
81 82

43. EMERGENCY STOP
Valve 56 de-energises
and thus opens at very
low pressure to unload
system pressure during a
power loss or emergency
stop situation.
Y1 Y2
81 82

44. MAINTENANCE
65
CAUTION: Open valve
65 to drain accumulators
before carrying out any
maintenance work on the
system.
Y1 Y2
81 82

45. PRESSURE SETTINGS
t
SET POINT P
S
The set-point for the
grinding pressure is set
from the Central Control
Room.

46. PRESSURE SETTINGS
P
t
SET POINT P
S
P
S + ΔP
1
The pump will charge the
accumulators to P
S + ΔP
1
then the pump drive
motor will stop.
Over a period of time,
leakage will cause the
grinding pressure to
drop.

47. PRESSURE SETTINGS
P
t
SET POINT P
S
P
S + ΔP
1
P
S - ΔP
4
When the pressure has
dropped to P
S – ΔP
4, the
pump is re-started to
charge the accumulators
back to P
S + ΔP
1 when
the cycle repeats.

48. PRESSURE SETTINGS
P
t
SET POINT P
S
P
S + ΔP
1
P
S - ΔP
4
10 – 60 min
Typically the cycle time
between pump re-starts
should be in the range 10
to 60 minutes.

49. PRESSURE SETTINGS
P
t
SET POINT P
S
P
S + ΔP
1
P
S - ΔP
4
The minimum system working pressure should
therefore always be higher than the
accumulator pre-charge pressure to ensure
that the accumulators are never fully emptied.

50. PRESSURE SETTINGS
P
t
SET POINT P
S
P
S + ΔP
1
Y2 P
S + ΔP
3
P
S - ΔP
4
If a build-up of material on
the grinding bed causes the
pressure to rise to P
S + ΔP
3
then solenoid Y2 energises
to bleed some accumulator
volume to tank.

51. PRESSURE SETTINGS
P
t
SET POINT P
S
P
S + ΔP
1
Y2 P
S + ΔP
3
Y2 P
S - ΔP
2
P
S - ΔP
4
Solenoid Y2 will de-energise
again when the pressure has
dropped to P
S – ΔP
2.

52. PRESSURE SETTINGS
P
t
SET POINT P
S
P
S + ΔP
1
Y2 P
S + ΔP
3
Y2 P
S - ΔP
2
P
S - ΔP
4
The pump compensator is
set to a pressure higher
than P
S + ΔP
3

53. PRESSURE SETTINGS
P
t
SET POINT P
S
P
S + ΔP
1
Y2 P
S + ΔP
3
Y2 P
S - ΔP
2
P
S - ΔP
4
And the system relief
valve is set at least 10 bar
higher than the pump
compensator

54. CYLINDER DOUBLE ROD SEAL
Normal connection

55. SEAL LEAKAGE TEST
The drain hose can
be removed using
the quick release
connections.

56. SEAL LEAKAGE TEST
The supplied hose can
then be used to check
for seal leakage from
the inner seal.

57. CYLINDER DOUBLE ROD SEAL
If leakage is detected,
block the drain line (to
pressurise the outer
seal) until the inner seal
can be replaced.

58. © 2008 Eaton Corporation. All rights reserv ed.
F. L. Smidth
Atox Mill Hydraulic System

59. © 2004 Eaton Corporation. All rights reserved.
F. L. SMIDTH
Atox Mill
Hydraulic System
Steve Skinner
Eaton Fluid Power
Havant, UK
November 2003
1
st
Revision November 2004
2
nd
Revision November 2005
3
rd
Revision January 2006
4
th
Revision December 2007
5
th
Revision Marts 2011 By FLSmidth NISM+JOK