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Service Forum Ha Noi Vietnam (Oct. 2010)
Preventive maintenance of plant key components
Senior Service Engineer Udo Feldotto
Polysius Anlagenservice

Contents:
- Roller Mill Maintenance
- Maintenance on Kiln Systems
- Maintenance on Tube Mills


Roller Mill Maintenance
Subjects
• Roller pair
• Grinding table
• Tie rods and hydraulic system

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Polysius


Roller Mill Maintenance
Roller pair
Bearing assembly for rollers

Precondition for attaining an acceptable
service life of the bearing arrangement:

- correct assembly of antifriction
bearing
arrangement (in compliance with the
Polysius assembly instructions)

X

The tapered roller bearing must be
assembled with the roller body on the
auxiliary device without intermediate ring.
The dimension X has to be determined.
The length L of the intermediate ring is
calculated as follows: L = X - Z
Z is normally 0.1 mm. (Follow the instructions in the
machine manual)

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Polysius


Roller Mill Maintenance
Roller pair
Confining air system
P

The confining air fan generates an

increased air pressure in the area of
the shaft seal (roller carrier).

The increased air pressure prevents
the ingress of dust in the seal area
and thus in the area of the bearing.

Correct functioning and perfect
technical condition of the fan and the
piping must be ensured.

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Roller Mill Maintenance
Roller pair
Confining air system

Confining air fan in very bad
condition.
- The suction filters must be
free of damage.
- The suction filters must be
regularly
cleaned and exchanged.

- The exchange interval depends
on
the dust formation in the
building.
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Roller Mill Maintenance
Roller pair
Confining air system

rotating

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stationary

Positive air pressure prevents the ingress of dust
Polysius


Roller Mill Maintenance

Roller pair
Oil circulation
Circulating
oil system
lubrication

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Polysius


Roller Mill Maintenance
Roller pair
Circulating-oil lubrication
Particle filtration
Indication of filter
contamination via differential
pressure indication
Metal detector
Permanent magnet (adhesion of
metal particles)
Indication of adhesion of metal
particles
Circulating-oil lubrication is
recommended for achieving optimum
cleaning of the bearing lubricant.
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Polysius


Roller Mill Maintenance
Roller pair

Guide pin

Guide bracket

Wear at the guide brackets and guide pins can
lead to vibrations and increased wear at the sides
of the grinding table liner segments and the
grinding rollers.

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Polysius


Roller Mill Maintenance
Roller pair
5 mm

10
mm
5 mm

The gap between the guide pin and the guide brackets
has to be checked. The gap depends on the size of the
mill.
Size (examples):
RMK 27/13; gap: 5 mm
RM 57/28; gap: 10 mm

Guide pin

Gap increases > 5 mm must be compensated by underlaying
the wear segments with compensating plates.

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Polysius


Roller Mill Maintenance
Roller pair

5 mm

10
mm

5 mm

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Polysius


Roller Mill Maintenance
Roller pair

5
mm

10
mm

5
mm

Clearance guide bracket /-pin > 35 mm
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Polysius


Roller Mill Maintenance
Roller pair

Force introduction into the roller
pairs
When the roller pairs are turned (by 180° ) to achieve
uniform wear at the roller tyres, it must be ensured
that the hook is positioned in the same place (at the
same distance and direction) in which it was
positioned before the roller pair was turned.
NOTE
The tie rods are always hooked into the outer hooks.

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Polysius


Roller Mill Maintenance
Roller pair
Protocol of wear at the roller tyres
To be able to assess progressing wear, it is necessary to keep wear protocols.
Together with the rollers, a template with the relevant measuring points is supplied which are

determined according to the roller tyre contour.

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Polysius


Roller Mill Maintenance
Roller pair
Protocol of wear at the roller tyres
When the wear has attained the limit S2 , the roller tyres must
be exchanged.
Should the wear exceed this limit, roller tyre breakage cannot
be ruled out.
The value S2 depends on the size of the roller pairs

(see machine

manual)

Example: size 54/27 and S2 = 150 mm

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Polysius


Roller Mill Maintenance
Grinding table

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Polysius


Roller Mill Maintenance
Grinding Table
Table liner fastening
Wedge element
Clamping piece
Lug
Table liner segment

Dam ring heightener
Grinding table
insulation
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Polysius


Roller Mill Maintenance
Grinding table
Assembly of table liners
• Alignment of the table liner segments on the
grinding table
• Adjustment of equal gaps between segments
• At the inner radius, the table liner segments
must be in contact with the limit stops
• The lugs must be in contact on the side which is
opposite to the sense of rotation. Gaps must be
closed with packing plates
• The wedge elements must be ground until they
have the right size depending on the toleranced
casting dimensions
• The table liner fastenings must be tightened with
the specified torque
• Assembly of grinding table insulation

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Polysius


Roller Mill Maintenance

Grinding table
Wear measurement protocol of table liner wear
The supplied template shows the measuring points determined in
dependence on the grinding table contour.
The wear measurement has to be performed every 3 months.
When the wear rate is high, the interval between the wear
measurements must be shorter.

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Roller Mill Maintenance
Grinding table
Wear measurement protocol of table liner wear
S1

A

1
2
3

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Polysius

B


Roller Mill Maintenance
Grinding table
Wear measurement protocol of table liner
wear
When the wear limit S1 is attained, the table liners must be exchanged.
Table liner breakage cannot be ruled out when the wear limit S1 is
exceeded.
The value of the wear limit S1 depends on the size of the grinding table.
(see machine manual)
Example: Size 54/27 and S1 = 150 to 160 mm

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Polysius


Roller Mill Maintenance
Grinding table
Table liner fastening
Tightening torque for expansion bolts 8.1

Checking required every 6 months; checking of fastening of new table liners required
after 30 - 50, after 250 and after 500 operating hours.
• Damaged expansion bolts must exchanged.
• The tightening torques of the bolted connections items 1, 4 and 5.1 must be checked
every 6 months.
• During the first commissioning and after every repair, the following connections must
be checked after 30 to 50 operating hours:
- grinding table with gear unit
- dam ring heightener
- cover
These intervals must be observed to prevent that the liner segments on the grinding table
are dislocated. This can have serious consequential damage.

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Polysius


Roller Mill Maintenance
Tie rods and hydraulic system
Checking of horizontal roller pair position and correction

A check and, if
necessary, a correction
are always required
when
• a repair has been performed

• table liner segments and/or
grinding rollers have been
replaced or have been
subjected to build-up welding
• cylinders and/or tie rods
have been replaced
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Polysius


Roller Mill Maintenance
Tie rods and hydraulic system
Checking of horizontal roller pair position and correction
The following checks have to
be performed after the roller
pair units have been returned
into the horizontal position:
• check and, if necessary, correction
of the limit switches
• check and, if necessary,
adjustment
of the ultrasonic measuring
sensors

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Polysius


Roller Mill Maintenance
Tie rods and hydraulic system
piston accumulator
gas chamber (nitrogen N2)

piston
oil pump

hydraulic fluid (hydraulic oil)
to consumer

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Polysius