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SHENYANG HEAVY MACHINERY CO., LTD.
1. APPLICATION
The vertical roller mill MLS3424A is used for grinding cement raw meal and the raw material for building, chemical and ceramic industries.
2. SPECIFICATION
Plant data
Work capacity： 165t/h (wearing evening)
Feed size: ≤85mm
Feed water content: ≤12%
Wearable capability(consuming electricity guide line) ＜8.49kWh/t Out feed size: <16%R 0.09mm
Speed of grinding track: 24.5rpm
Inching speed of grinding track: 0.5rpm
Main motor Type: YRKK710-6
Power: 2100kW Voltage 6600V Speed: 994rpm Auxiliary motor Power: 45kW Speed: 1480rpm
Allowable volume of injection water into the mill (for three nozzles) : <7.5m3/h (The actual volume of injection water into the mill is determined by the craft)
Pressure of injection water: 0.3Mpa
Temperature of injection water: <25oC
Total volume of using water: 28m3/h
Total installed power: 2300kw (approx.)
Total weight (excluding electric devices and driving units):327210kg (Not including the weight of main motor、main reducer、electrical controlling device
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and DSK-1600 three gates)
2.2 Technical characteristics for each component
2.2.1 Grinding rollers
Number of rollers: 3
Diameter of roller: 2450mm
Width of roller: 800mm
Grinding power of roller（one roller） 1235kN 2.2.2 Tension device
Hydraulic tension cylinder (with accumulator): 3sets
Operating pressure: 20Mpa
Structure of oil cylinder double function cylinder
Nitrogen pre-pressure of accumulator: (0.33-0.66) ×20Mpa
Oil cylinder working pressure 20MPa Motor of hydraulic station:
Power: 7.5kW
Speed: 1450rpm
Power of electric heater: 2×2kW
2.2.3 Main reducer(Unsupplied, the purchaser should buy the main motor by
themselves according to the ordering require by bargainer)
Speed of input shaft: 994rpm
Speed of output shaft: 24.5rpm
Low pressure pump of hydraulic station:
Power: 2×15kW
Speed: 1450rpm
High pressures pump of hydraulic station:
Power: 4×15kW
Speed: 1450rpm Motor for heated oil circulating loop:
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Power: 4×6kW
Volume of cooling water through
Cooler: 45m3/h
Pressure of cooling water: 0.2Mpa
Temperature of cooling water: <28 oC
2.2.4 Classifier
Number of classifier vanes: 90
Range of speed: 9-90rpm
Motor type YP2280S—4
Power 75kW Frequency conversion range 3～100Hz
Gear nominal transmission ratio: 17.77
Cooling fan type G280—A Power 370W Speed 1400r/min
2.2.5 Sealing air fan
Type of fan: MF10-19-13No6.2A sealing fan for cement mill, Outlet : turn right 90°
Power of motor: 22kW
Speed: 2940r/min
Air flow: 3650 m3/h
Air pressure: 9000Pa
2.2.6 Overrunning clutch
Air used in cylinder: little (use when action)
Air pressure: 0.3Mpa
2.2.7 Auxiliary reducer (supplied by Flender, Germany)
Input speed: 1480rpm
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Output speed: 19.22r/min
Speed of grinding plate: 0.5r/min
3. Design and functional description 3.1 Principle of operation
The rollers of the mill are pressed by hydraulic tension system. The classifier is driven by frequency control motor, which is of variable speed. See fig. 1 for the overall design of the mill.
Three grinding rollers are fitted under the pressure frame; the grinding roller module is composed by thrusting component and splice joint module. The tension force produced by three tension rods is transmitted trough the pressure housing
Discharge outlet
Shell of classifier
Frame
Hot air inlet
Hydraulic cylinder Driving device of classifier
Lubricate oil Dynamic vane of classifier
Static vane of classifier
Feed inlet Pressure bracket Roller Air ring Table Main motor Auxiliary motor Auxiliary gear box
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onto three rollers, then to the material bed between grinding roller and grinding track, form forcing close annular body between the groundwork、tension rod、 frame 、grinding roller、 grinding track and reducer. An accumulator is fitted in each hydraulic tension system as a shock absorbing system. The grinding track is rotated by main drive through the reducer, and the grinding rollers are rotated under the action of friction caused by grinding track. The grinding track turning transmit the torque moment onto the frame trough the grinding rollers, then the
force is transmitted to the machine casing by pressure frame along circumferential direction.
The material to be ground is fed to the mill down a feed chute on one side of the mill into the grinding area where it is drawn in between the grinding rollers and the grinding track and ground by compression and friction. It is then pushed outward over the edge of the grinding track. The stream of gas flowing in all around the nozzle ring can prevent the material falling down through the nozzle and also allow the foreign bodies with high specific gravity to fall down through the nozzle and be discharged out of the mill by scraper track. The ground material to a certain degree of fineness is carried up by the stream to the classifier where the oversize is separated out by gravity and centrifugal force. The finished meal is discharged by air while the coarse particles are returned to the grinding track for regrinding.
According to tests on site, it takes the feed material about 30 time’s circulation (grinding-going up with stream-falling down-regrinding) before the material reaches the finished fineness. Therefore the mill is also a high efficient suspension dryer when grinding wet material with hot gas. The temperature goes
down from 300 ℃at nozzle ring to 100℃ at the place one meter above the vane.
This is one of reasons why the MLS3424A mill can grind cement raw meal with high moisture.
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higher grinding efficiency, shorter process flow and lower specific power consumption. Furthermore, the grinding of material is done under limited pressure.
Since the mill housing is large, low flow rate can be obtained though the inlet air volume is large. Based on this, the wear caused by injection and loss of pressure is reduced; therefore the mill can be fitted with a small capacity hot gas fan.
The grinding parts on grinding rollers and grinding track are replaceable segments which are made of wear-resistant material.
3.2 Structure of a MLS mill
You can see from fig. 1 that the major components of a MLS424A mill are: mill frame, mill foundation, grinding track, grinding rollers, tension system, classifier and sealing air pipelines.
3.2.1 Mill driver
The mill driver consists of main motor, conical planetary reducer, low-speed auxiliary reducer and auxiliary motor.
The main motor is three-phase asynchronous electric motor, air cooling, started by liquid resistance.
The first stage of conical planetary reducer is of conical gear and second stage planetary gear. The second stage is parallel shaft gear; the third stage is planet gear. The output shaft is vertically mounted. Under the bottom of the output shaft there are several babbitt thrust bearings. The reducer bears the gravity of grinding parts and the vertical component force produced by tension system. The shell of the reducer is of welding construction.
The first stage of auxiliary reducer is of conical gear and the second and third stage cylindrical gear. The auxiliary drive slowly rotates the main drive via auxiliary reducer and overrunning clutch. After the starting of main drive, the overrunning clutch disengaged and auxiliary driving system shut down.
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3.2.2 Grinding track
The molten grinding track is placed and bolted on top of the reducer according to transmitting torque moment. The removable grinding liner is supported by the grinding track. The segments rest against the wedge-shaped rim on the outer edge of the grinding track. On the opposite side towards the inner hollow in the grinding track, they are fastened by clamping plates. The geometry of segments determines the inclination of the grinding rollers, the angle between the normal and vertical line at the contact point of grinding roller with segments is 15 degrees.
The nozzle ring is located between the grinding track and the mill housing. Gases flow through the inlet channel into the area underneath the nozzle ring from where they are sucked upwards through the guide channels due to negative pressure inside the mill. The material to be ground is spread to the grinding area according to pre-determined direction resulting from the gases flow above the nozzle ring and the action of pressure difference in the grinding cavity. Foreign bodies that pass the guide channels fall into the area underneath the nozzle ring where they are discharged out of the mill by a scraper. In case of material spillage the cross-section of the nozzle ring can be reduced by covering the nozzles and thus air velocity and lifting force can be increased.
3.2.3 Grinding rollers
The three stationary grinding rollers are staggered 120 degrees and fastened with their pressure brackets to the pressure housing so that their being carried in rocker mountings allows them to deflect on encountering obstacles in the grinding track.
The body of grinding roller is made of steel plate by welding .The segments of grinding liners are fastened by clamping plates, which are easy to replace. The shielding plates are mounted on the outer surface of pressure brackets to prevent the wear of bracket caused by fluid material.
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3.2.4 Tension device
Pre-loading of the grinding rollers is by hydraulic tension device. Pressure is transmitted to the rollers via the pressure frame to which pressure yokes of the rollers are fastened .The grinding force of grinding rollers is thus applied on the material bed between grinding rollers and grinding track. An accumulator is fitted on each hydraulic tension cylinder as a shock absorbing system.
Hydraulic system can also be used to lift the pressure frame. When doing this, the plates which connect the pressure frame and grinding rollers should be removed firstly and the grinding rollers should be fixed with handling tools. The pressure-relief valve of hydraulic system should be down-loaded when removing the plates which connect pressure housing and grinding rollers since the hydraulic cylinders don’t have the pressure to lift the grinding rollers when acting upward. 3.2.5 Classifier
The mill is equipped with dynamic and static classifier to suit for more abroad fineness requirements. Classifier is mounted on top of machine shell with one rotary impeller. The rotary vane will be driven by frequency control motor 、 the reducer realize infinitely variable speeds, revolution of classifier can be adjusted by frequency control motor. First time powder selection will be carried out in still grid drum at outer side of rotary impeller
The higher of the classifier speed, the finer of the finished product and vice versa. Since the fineness of the finished product is also affected by such factors as temperature humidity and air pressure. It is impossible to find out the relationship between speed of classifier and the fineness of finished product. The relationship can only be determined during commissioning.
The classifier shaft is borne in a reinforced part of the classifier housing by means of two self-aligning roller bearing and one axial bearing. The bearings have no dust caps with them since the inside of their support is in sealed state. The bottom of the classifier drive is sealed by means of the differential pressure
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between the atmospheric pressure and the negative pressure inside the mill. The bearings are periodically lubricated by grease.
3.2.6 Mill frame
The mill frame consists of frames of welded construction, the joints of
frames are welded on site, the mill frame is provided with a maintenance door, an
access door and a manhole and three equally distanced water injection devices, the mill base is welded with foundation plate and the mill frame is fastened to classifier by bolts. Wear-resistant and replaceable liners are placed on the inside wall of mill frame above the pressure frame to prevent the pressure frame from damaging the inside wall of mill frame when it moves.
3.2.7 Sealing air part
The sealing air part prevents dust leaking into the grinding roller bearing system. The sealing air produced by the sealing air fan inserted in to the grinding roller bearings through the pipes mounted upon the mill housing. A knuckle joint is fitted in the pipe in order to prevent the movement of grinding rollers to affect the connection.
Since there is negative pressure in the mill and sealing air escapes from the ring-shaped area, no dust can get into the sealing and bearing part. The pressure of sealing air is monitored by means of contact manometers and pressure of sealing air should not be lower than 5000Pa.
4. Operating
4.1 Preparations before starting the mill
When the mill has been down for any length of time, e.g. during repair work, we recommend to check the connections of each part. The oil level of the various units, the positions of various valves, etc. All supply units up to the mill feeder have to be filled with material to make sure that material is supplied to the mill as soon as the feeder is switched on. Otherwise there is a danger that the mill charge is not enough. When the mill has been emptied, sufficient material has to be fed so
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as to provide a grinding bed of about 60mm.
4.2 Main items for Checking
The following items have to be checked before starting the mill;
Check that the oil filters of hydraulic units are not blocked; check that the water pipes of oil coolers are not blocked.
Check that the pressure of hydraulic tension system is in conformance with the values specified by the manufacturer. If not it has to be set according to the instructions of the manufacturer.
4.3 Switch –on sequence
4.3.1 Open the ball valve (14) of hydraulic tension system, and then switch on the power.
4.3.2 Switch on the oil heaters of reducer and the hydraulic tension system、three–flap gate hydraulic unit.
Switch on the electricity heaters before the oil temperature of hydraulic unit of reducer reaches 35 ℃ . Switch on the electricity heaters before the oil temperatures of the hydraulic units of three–flap gate and hydraulic tension system reach 20℃. In case of low ambient temperature heat up the gear and hydraulic unit by hot air until the oil pump can be put into operation. When the
temperature indicated by contact thermometer of reducer exceeds 38oC, switch
off the heaters. When the temperature indicated by contact thermometer of the
hydraulic units of three–flap gate and hydraulic tension system exceeds 35oC,
switch off the heaters.
4.3.3 Switch on the sealing air fan motor.
4.3.4 Switch on the small oil pump in the classifier reducer.
Three minutes later, switch on the fan of motor drive and the motor drive of classifier.
4.3.5 Switch on the low pressure pump when the temperature of reducer oil exceeds
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4.3.6 Switch on the low pressure pump motor of reducer hydraulic station four minutes later and when oil outlet pressure of low pressure pump reaches 0.1MPa, switch on motor of high pressure pump.
4.3.7 Switch on the intelligent pressure transmitter (11) of hydraulic tension system. Switch on the oil pump motor (3) when the temperature indicated by the
thermometal thermometer (19) exceeds 20 . It is allowed to switch on oil ℃
pump motor only when the pressure of intelligent pressure transmitter (11) is lower than 13MPa, and it will be automatically switched on when the pressure is lower than this value during the operation of the mill, and oil pump motor (3) will be shut down and the system is in pressure- keeping state when pressure of intelligent pressure transmitter (11) is≥ 20MPa.
4.3.8 Switch on pump motor of three–flap gate (5) and electric liquid change-over valve (19/1—3) when temperature of electric contact thermometer (2/1)
exceeds 20 . And there are three electric liquid change℃ -over valves in total,
and switch-on sequence is as follows: switch on electric liquid change-over valve(19--1), which will disengage after 1.5 seconds; after 1/6 second, switch on electric liquid change-over valve(19--2), which will disengage after 1.5 seconds; after 1/6 second, switch on electric liquid change-over valve (19--3), which will disengage after 1.5 seconds; after 1/6 second, switch on electric liquid change-over valve (19--1)… … periodically acts according to this sequence and period of action is 5 seconds.
4.3.9 Switch on overrunning clutch. When switching on high pressure pump motor of reducer hydraulic station and after two minutes later and when oil outlet pressure of high pressure pump reaches (4-15) MPa, switch on change valve 2/1 and make cylinder motion and clutch joggle 1/1 and force stroke switch to switch on.
4.3.10 If resistance thermometer temperature of static pressure bearing in reducer is
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on one minute, switch on auxiliary motor.
4.3.11 Switch on main motor. When pressure of 16 pressure switches in reducer hydraulic station exceeds (4-15) MPa and auxiliary motor is switched on over 40 seconds, and change valve (2/1) of overrunning clutch is shut down over 7 seconds, switch on main motor. When revolution of main motor exceeds output revolution of auxiliary reducer, overrunning clutch will automatically disengage, and force stroke switch (1/2) switch on 1 second, that is, switch on change valve (2/2) of overrunning clutch, auxiliary motor will disengage. In order to guarantee the safety, set pin on overrunning clutch should be plugged. Mill will be in normal operation state when all the various systems are in normal operation.
4.4 Monitoring
4.4.1 Alarming
a. When the absolute vibration speed of vibration sensor mounted on the reducer is more than 5mm/s.
b. Oil level in oil tank of reducer hydraulic station is lower than down alarming limit or higher than up alarming limit.
c. When differential pressure of rough filter in reducer hydraulic station P △
≥0.05MPa.
d. When differential pressure of fine filter in reducer hydraulic station P ≥0.05MPa.△
e. Oil temperature of low pressure oil outlet in reducer hydraulic station t＞45°C or t ＜38°C.
f. When oil pressure of low pressure oil outlet in reducer hydraulic station p<0.12MPa, it will send alarm, and at the same time spare pump motor starts, when pressure p≥0.4MPa, spare pump motor shuts down. When pressure P>0.5MPa, it will also send alarm.
g.When the temperature of resistance thermometer of five bearings in reducer is higher than 60℃.
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h.When the temperature of resistance thermometer of four static pressure bearings in
reducer is higher than 60℃.
i. Oil pressure of high pressure oil outlet in hydraulic station of reducer P≥20MPa. j. Low pressure pump motor in hydraulic station of reducer overloads.
k. High pressure pump motor of reducer hydraulic station overloads.
l. Differential pressure of heat exchanger in hydraulic station of reducer △P≥ 0.1MPa.
m. Differential pressure of oil filter (5) in hydraulic station of tensioning device △P ≥0.35MPa.
n. Oil level of hydraulic level control device (16) in hydraulic station of tensioning device is lower than alarm oil level.
o. Pressure of intelligent pressure transmitter in hydraulic station of tensioning device P ≤11.5MPa.
p. Armor thermal resistance of mill roller bearing is higher than 100℃.
q. Differential pressure of oil filter (14) in hydraulic station of three-flap gate △P≥ 0.35MPa.
r. When oil level of hydraulic level signaler (18) in hydraulic station of three-flap gate is lower than the alarm position.
s. Any pressure of intelligent pressure transmitter of sealing air (1-3) is less than 5000Pa.
t．Anyone of three hydraulic pressure cylinders in three-flap gate has no action within10 seconds.
4.4.2 Main motor shut down
a. When the absolute vibration speed of the vibration sensor mounted on the reducer is more than 10mm/s.
b. Oil level of oil tank in hydraulic station of reducer unit is lower than down limit oil level for shut down.
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c. Oil pressure of low pressure oil outlet in hydraulic station of reducer unit is less than 0.1MPa.
d. Oil pressure of high pressure oil outlet in hydraulic station of reducer unit △P≤ (4-15) MPa.
e. Temperature of resistance thermometers of five bearings in reducer unit is higher than 65℃.
f. Temperature of resistance thermometers of four static pressure bearings in reducer
unit is higher than 65 .℃
g. Oil level of oil level control device (16) in hydraulic station of tensioning device is lower than lowest oil level.
h. The pressure of pressure relay (10/4) of hydraulic tension system is not more than 10Mpa.
i. Oil level of hydraulic oil level signaler (18) in hydraulic station of three–flap gate is lower than the lowest oil level.
j. Armor thermal resistance of mill roller bearing is higher than 120℃.
k. Any pressure of intelligent pressure transmitter (1—3) in air seal unit is less than 4500Pa.
1. Anyone of three hydraulic pressure cylinders in three-flap gate has no action within15 seconds.
4.4.3 Tension device unlade a. Automatic operation
The manual two-position-four-way change valve (8) is at working position, ball valve (14) opens, switch on pressure relay (10/1) and solenoid valve (12). b. Manual operation
Switch off the solenoid valve (12), open the ball valve (14) and place the manual two-position-four-way change valve (8) in non-operation position.
4.5 Switch off sequence
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4.5.2 Switch off the main motor and the oil pump motor of three gates hydraulic unit. 4.5.3 Switch off the oil pump motor (3) of hydraulic tension system. Switch on the
solenoid valve (12). The system now begins to release pressure. Switch off the solenoid valve (12) when P=0 and the solenoid valve restores its normal position by spring. If manual operated, it will suffice to change the position of the manual two –position-four-way change valve(8) .
4.5.4 Switch off the high pressure pump motor of reducer five minutes later after the main motor is switched off.
4.5.5 Switch off the low pressure pump motor of reducer five minutes later after the high pressure pump motor is switched off.
4.5.6 Switch off he small oil pump motor of classifier reducer three minutes later after the motor drive of the classifier is switched off.
4.5.7 Switch off the sealing air fan motor. 4.5.8 Switch off power and water supply.
4.6 The lifting up and lowering down of pressure frame.
Since the hydraulic tension system is a pressure-keeping system, the oil in upper and lower chamber of cylinder can not flow freely. Therefore, the following works have to be done if the lifting up or lowering down of pressure frame is needed.
4.6.1 Lifting up the pressure frame (manual operation)
Place the manual two-position-four-way change valve (8) in non-operation position and close ball valve (14).
Manually start oil pump motor (3) and oil comes into the lower chamber of oil cylinder as the pressure goes up, which results in lifting up the pressure frame when the pressure frame is clamped or reaches the upper limit, the discharge valve (13) acts as a protecting element.
4.6.2 Lowering down of pressure frame by its gravity
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and close ball valve (14). It’s not necessary to start the oil pump motor (3) for lowering down the pressure frame just slowly open the cut-off valve (7/3) and the pressure frame will fall down slowly by its gravity. The falling speed is adjusted by the cut-off valve (7/3).
See fig.2 for motion depicting and linkage relation of electrical element
when staring,monitoring,closing down and lifting and descending of pressure
frame. The numbers under electrical element at this diagram are the numbers at its hydraulic system and air passage schematic diagram. See the No.10 segment for hydraulic system and air passage schematic diagram. Among the rest, for reducer hydraulic pressure station schematic diagram and three gates hydraulic pressure station schematic diagram, please see their respective specification.
5. Assembly
5.1 Assembly of foundation parts
Foundation parts comprise all parts to be placed into the foundation on which the mill together with the classifier and drive units are mounted.
5.1.1 Assembly of main equipment base
In order to be convenient for transportation, main equipment base is divided into eight pieces (foundation frame, housing support, reducer base) for delivery, and will be preassembled and marked in manufactory.
When mounting main equipment base, ground gauge and tape will be adopted for measuring center location (refer to relevant assembly drawings), bottom hinged point of tensioning device will be taken as reference during measurement, and main equipment base should be measured by gradienter so as to guarantee the level degree.
Before main equipment base is mounted, all reference points (for example: mill center) have been determined and confirmed by site engineer in charge of mounting, and must keep identical with foundation scheme drawings. Foundation surface of one time grouting should be cleaned, for example: cut steel reinforcement ribs that are higher than plane to avoid interference with main equipment base. Pad for supporting
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I-bar and shims below main equipment base will be put at appointed location of one time grouting top surface. And foundation bolt s and foundation bolt box will be put in holes reserved for one time grouting, and then grout after correct location is found, both level degree and standard height can be measured by gradienter.
Reducer base will be delivered in one piece, and distortion and surface scratch are not allowed during transportation. Before mounting, anti-rust paint or other impurities on machined surface of reducer base should be removed. Central location of reducer base and central location of main equipment base must reach superposition (that is: refer to bottom hinged point of tensioning device).
After reducer base that will be delivered in bulk and connecting plates of foundation frame are screwed, readjust and level up reducer base and screw down foundation bolts.
Then, mark on reducer base by chalk or paint, and measure by water level with tolerance of 0.05mm/m, and it can be adjusted by using pad if not reach tolerance requirements. First, measure four corners on reducer base, adjust I-bar if deviation is big, if within tolerance range, that is, measure other measured point in top plane and make a record.
After main equipment base is put into foundation, additional steel rib bunch for 30 holes with diameter of 180 on main equipment base will be hanged, and vertically pointing to foundation. Additional steel rib bunch for 12 holes with diameter of Φ125 on reducer base will be hanged, and vertically pointing to foundation.
After aforesaid work is finished, reducer base and foundation frame will be welded according to relevant assembly drawings. And supporting base of housing and foundation housing will be welded. After welding, distortion should not occur. And remeasure reducer base and level up, if distortion occurred due to welding, it is suggested to grind surface and maximum is 0.05mm/m (arithmetic average value).
When reducer base, foundation housing and housing base are mounted and finished adjustment, second time grouting can be carried out for these pieces.
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According to design requirements of drawings, distance between top plane of second time grouting and top plane of reducer base should be less than 25mm and concrete must go through sufficient vibration in vibrator so as to fill in the whole space. Notes: this is only grouting for inside of reducer base, concrete passes central grouting entrance from top and enter reducer base.
5.1.2 Assembly of motor foundation
The motor foundation is delivered to locale integrally.
Firstly, clean one time grouting concrete surface, and set foundation bolt boxes(Make sure the setting place is what drawing requests), foundation bolts and I-bar spacer and washer required by the same method of setting main machine support. Secondly, set motor foundation, and adjust its axial direction, height, center line by appropriate apparatus, then weld it on reducer foundation, and grind to smoothness after welding. Then hang tendons at 46 holes of Ф50, making them extend in base.
After finishing the above work, weld reinforcing-bar and component in foundation bed.
5.2 Assembly of mill components
Mill components are those parts which are mounted on the foundation parts. 5.2.1 Reducer
The reducer of the mill serves as a support of the grinding parts and as a means of speed reduction of the mill motor. The reducer is a very important and heavily used component of the MLS mill. The quality of main contact surface of reducer should be ensured during transport and assembly. The reducer should be conveyed integrally, and auxiliary reducer, overrunning clutch and reducer hydraulic pressure station should be conveyed singly.
5.2.2 Assembly of reducer
Prior to its assembly and transportation to the mill foundation the reducer has to be lifted by means of hydraulic pumps or other adequate lifting devices in order to be able to check whether the reducer bottom is absolutely clean and smooth. Ensure that
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the reducer is wedged and secured against dropping or skidding before the underside is checked. The reducer base has to be free from dirt and remaining protective paint. And check the reducer base for any unevenness such as hammer blows center punch marks etc.
Place the I-bar (80mm height) on the slide rails and the I-bar can be tack welded at the unimportant points on the slide rails. Then the reducer is pushed on top. And stack up enough rolling bars which diameter must be more than 60mm, and which surface must be smooth. The reducer is drawn onto reducer support by gin type tools. Put all bolt holes in order, and jack reducer up by hydraulic jack in order to shift the rolling bars out. Check that the contact surface is smooth or not again. Put down the reducer, and check the gap between contact surfaces by spacer gauge. The maximal gap shouldn’t be more than 0.05mm. The adjusting pins are embedded after adjusting the place and gap of reducer. The T type bolts are screwed down by limiting moment spanner. After assembling bolts and pins at reducer and support, wedge them by wedge iron.
Consult assembly specification of reducer for its detailed assembly instructions. 5.2.3 Assembly of hydraulic cylinders with pressure accumulators
For reasons of an improved accessibility we recommend that the three hydraulic cylinders with the pressure accumulators are mounted in the tie rod eye provided for it at the foundation housing before the mill base is assembled. Please pay attention to the distance rings.
5.3 Assembly of frame
At one hand, frame is the support of classifier and contains reducer. At the other hand, frame can guide direction of sirocco, collect and d remove impurities and heat insulating layer is also filled in the frame.
5.3.1 Assembly of frame
Because of restricting of transportation condition, the frame is disassembled to six segments and conveyed to locale. But it should be preassembled at production
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plant, and bolting plate should be saved in order to spotting when welding on site. Each segment is carried on support of main machine, and set well according to the method which drawing requests. The six segments of frame are bolted at position of bolting plate by bolt. Then the frame is azimuth adjusted and localized spot welding.
5.3.2 Adjustment of frame
The frame is now aligned axially and centrally to the mill center. The longitudinal and crosswise axis with the fixed axes of the mill foundation and gearbox is plumbed by means of a sounding lead. It is of major importance that the center of the frame corresponds to the center of the reducer. The permissible tolerance amounts to a maximum 0.5mm.
5.3.3 Welding of mill frame
Once the mill frame is aligned it is welded the six parts together according to corresponding drawing, rubdown the inferior extremity of the weld bond, cut off the plywood, then weld the frame on the main equipment base. Erenow, weld insulation bed and weld ported air ring bracket according to the drawing.
5.3.4 Pouring of main equipment base
After aforesaid work is finished, that is, pouring of the whole foundation should be intact and foundation should be provided with smooth surface.
After pouring concrete, heat insulating material should be mounted in the heat insulating layer of the frame, and it should be paid attention that bolt head must not be exposed outside the plane, otherwise scraper will be scratched.
5.4 Assembly of grinding track
The grinding track is delivered in one part. Once the grinding track is brought to the mill foundation it is to be placed on a stack of wooden beams or ties which should have a height of approximately one m.
5. 4. 1 Assembly of grinding track seat
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before assembly, and the rabbet dimension is measured again, then the assembly bolt pins are screwed on grinding track seat. At this time, the grinding bowl is hoisted and set on reducer by hoisting equipment. The maximal space between grinding track and reducer is 0.1mm before screwing down bolts. The grinding track seat couldn’t be declining in order to prevent disable of rabbet plate. Finally bolts are screwed down by limiting moment spanner.
5. 4. 2 Assembly of sealing cone
The sealing cone should be assembled after assembling grinding track well. Firstly bolt each part on grinding bowl by bolt, then carry out welding.
5.4.3 Assembly of scraper
As an assembly part, after scraper is assembled well, it should be screwed down on grinding track by bolt. At this time adjusting the gap between scraper bottom and heat insulating layers should be noticed.
5.5 Mounting of tensioning pole bracket and frame flange
According to the drawing requirements, weld the tension pole bracket firstly, and in accordance with the location marked in the drawing, the frame flange which are divided into three parts will be connected by using spring column pin and some flanges below classifier, then mount it on the frame, after adjustment, it will be welded on the frame. Before this, asbestos cord for seal should be put between flange below the classifier and frame flange and then dismantle bottom of classifier and carry out welding.
5.6 Assembly of grinding track liner
The grinding track liner is a wearable part of mill. It bears corrosion which is brought by milling force when mill running.
The contact between liner outside grinding track and grinding track seat should be well. The contact surface between liner and clamping plate should be smooth.
The grinding track and liner should be cleaned before assembling liner. The adjusting pins should be embedded the corresponding holes according to drawing
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after cleaning. Then the T type bolts are embedded. It should be noticed that the gaps between several liners at circle are approximately identical. Then the clamping plate should be assembled and screwed down by limiting moment. Finally several wedge washers are added to the gaps between liners.
After finishing the above work, the shield at middle of grinding track should be assembled according to drawing.
5.7 Assembly of nozzle ring
For transportation reasons the nozzle ring is dispatched in three parts, after arrived, weld the three parts together and adjust the position, then assemble back block.
Once these works have been completed the nozzle ring is brought in to the mill and placed onto the nozzle ring supports mounted on the mill base. The nozzle ring is centrally aligned with the grinding bowl, adjust height、level and center position. A divided square ring supplied loosely which is to decrease the air gap between nozzle ring and grinding track, adjust the radial position, and welds the ring on the inner cone of the nozzle ring finally.
After adjusting position, wedge it by slide wedge and weld the slide wedge on the wall of the bracket. Weld nozzle ring bracket、skims and nozzle ring together, finally seal the nozzle ring and bracket by sealing cord, put on the clamping plate.
5.8 Assembly of pull rods
The pull rods and some associative components are delivered in bulk; some coupling fastening pieces have to be greased before delivering. When assembling, firstly input the pull rod into the pull rod seat of the bracket, then a screw thread is enclosed for screwing the sleeves on the pull rods and pistons, and the upper slide rest is joined with pressure frame by splice joint.
5.9 Assembly of grinding rollers
The tree grinding rollers are displaced by 120 degrees but are mounted stationary; any grinding roller has rotation around its mandrel, but has not revolution. In fact, the
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position of the grinding roller has already decided by the position of the assembled tension device.
The grinding rollers are assembled completely with bearing system, grinding roller segments and pressure yoke but are delivered without oil filling. In case a longer delivery time is foreseen or requested by the customer (a min. 1 year before commissioning) the bearings are preserved.
A single conic assembly ring is included in the delivery of the three grinding rollers. This assembly ring is not to be employed for the assembly works but is an auxiliary tool to be used for a possible repair of the bearing system or for the changing of the radial shaft sealing rings. Furthermore a suit of handling tool which is used to assemble grinding roller is delivered at the same time.
5.9.1Assembly of pressure brackets on the roller axles
Before the grinding rollers are mounted into the mill, if the grinding roller and roller bracket are delivered as spare parts, you should assemble the roller bracket on the grinding roller. Firstly, put the closed type sealed cap adown, clean out the dirt on the constructional surface, pull the bracket to the locating surface, screw down the guard board by bolts. When placed guard board, you should collimate the lubricant hole and oil plug.
5.9.2 Assembly of grinding roller into the mill
The assembly of the grinding rollers into the mill requires a grinding roller support. The grinding roller support is assembled according to drawing “Assembly Device”.
Lift the grinding rollers into the mill by means of steel cables of the same length hung in the hooks which are cast at the pressure brackets. When assembling the grinding rollers try to place them in such a way on the grinding plate that roller tire center and grinding track center are congruent.
Once the grinding roller is placed on the grinding plate hang the grinding of the installation device into the supports at the pressure yoke. Ensure that the grinding
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roller is inclined by 15 degrees. A secure position of the grinding rollers on the grinding plate necessarily requires a locking of the grinding roller on the grinding plate with wooden wedges.
5.10 Pressure frame
The pressure frame transmits the pressure onto the grinding rollers. The pressure brackets of the grinding rollers are supported below the pressure frame and connected with it by articulation parts. At each corner of the pressure housing a pull rod with fork-shaped piece is connected. Its three-part design and the articulated suspension of the pull rods ensure an even pressure distribution on the three grinding rollers. For transportation reasons the pressure frame is usually delivered in three parts.
5.10.1 Assembly and welding of the pressure frame
The pressure frame has already been assembled once, numbered and stress-relieved by the manufacturer. In order to ensure perfect welding on site the three-part pressure frame was assembled by the manufacturer. In such a way that the distance between the individual parts provides for a good root weld joint.
Distance pipes are included in our scope of supply in order to enable you to keep the exact distance on site; you should pay attention to the sign of the manufacturer, and then weld the pressure frame together according to corresponding drawing. After welding, cut off the redundant sections on the distance pipes by gas welding and burnish the cut.
Before the pressure frame is brought into the mill, the footstep、ball and socket、 splice jointing base of the tension device must be assembled and keep the interface contacting well, assemble the splice jointing base on the frame.
5.10.2 Adjustment of the pressure frame
Firstly, assemble the adjusting plate and wearing plate of the three corners, bring the pressure frame into the mill by three isometric wire cables, and collimate the pressure frame and cylindrical roller on grinding roll by adjusting the handling tool. After the pressure frame is completely adjusted, splice joint the grinding roll bracket
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and pressure frame by six connecting plate.
After the work has completely done, center the pressure frame and adjust the clearance between the pressure frame and frame.
5.11 Hanging the pull rods into the pressure frame
The hanging is to be carried out according to drawing tension device.
The assembled pull rods have to be inserted into fork-shaped pieces by means of a winch or a grab host, and then the articulation support with ball is inserted and locked with locking plate and shackle.
5.12 Assembly seal air piping
It is of no importance for the further assembly whether the inner sea air piping that goes with the grinding rollers or the outer seal air piping that goes with the sea air fan is assembled first.
5.12.1 Assembly of the seal air pipelines within the mill
Insert the seal air pipelines that go with the grinding rollers into the wear bushings of the flange bearings with the end carrying the articulated inner rings that have been assembled by the manufacturer. The other end carries the elbow joint and articulated bearing that has been assembled by the manufacturer. This end is screwed tight with the pressure brackets of the grinding rollers. Don’t forget the sealing element.
5.12.2 Assembly of the seal air pipelines outside the mill
Fix the collecting piping at the mill frame by provisionally screwing the welded clips to the underside of the mill frame flange. Now the three connecting pipes of the collecting piping have to be fitted to the flange bearings and the flanges have to be welded to the piping.
After the completion of these works assemble the seal air fan with the suction filter and drive motor according to the arrangement plan. When doing so align the fan horizontally and vertically, nipped by special pipe clamps in proper position. Weld each pipeline and elbow. In order to reduce the mainframe’s disturbance which cause
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by the libration of the fan, using a tube.
Access three measuring pipelines and three pressure transmitters, the direction of pipeline and the position of frame can be decided by the user.
The measuring pipes are connected by welded flange and splice jointed flange of the frame.
5.13 Assembly of hydraulic pipeline for tension device
Pipe clamps in hydraulic pipeline of tension device should be carried to locale in bulk.
The pipe clamps with base are disposed on the outside of the bottom of the frame according to the graphics or field situation, every pipeline muse be bent according to the field situation. All pipelines must be cleaned before assembling. Once all the pipe work has been completed the whole piping system has to be flushed with hydraulic oil in order to prevent any rust.
5.14 Assembly of classifier
5.14.1 Assembly and mounting of classifier bottom part
In order to be convenient for transportation, the classifier bottom part are
divided into several parts, but it is required to be pre-assembled with the frame in the manufacturing plant and make marks. Weld connecting angle steel and screw the parts with bolts, and can be deliver to site after dismantling. First: assemble flanges of every part and frame flanges, and then bolts and spring column pin, before this, asbestos rope for sealing should be put between flanges below the classifier and frame flanges, then screw them by using angle steel for connecting and bolts and carry out welding, cut angle steel after welding and welded grooves and cut opening should be ground flat.
5.14.2 Assembly impeller
The impeller is carried to locale in the whole part, then fix vanes on impeller, fasten by boils, put the impeller on the appropriate height of the trigonal frame.
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Bottom Part”).
Like the classifier bottom part the classifier top part is also delivered in several parts and assembled and welded on the ground or on the classifier bottom part according to the numbers indicated. Screw bell housing to classifier bearing according to drawing. Place it into the classifier, align it concentrically, mount reinforcement and strutting and weld tightly. Observe welding instructions on the drawing ‘Classifier Top Part’.
Then assemble the speed gearbox and the motor drive.
5.15 Assembly of mill actuating device
According to drawings “Foundation Plan” 、“Slide Rails” and “Motor Support”. 5.15.1 Assembly of coupling main motor and reducer
The machine use diaphragm coupling, made in CHINA. Please observe their mounting and operating instructions.
5.15.2 Assembly of auxiliary reducer and overrunning clutch
An overrunning clutch (claw clutch) serves as a coupling between auxiliary reducer and main motor; it should enclose the distance ring on the motor shaft before assembling the overrunning clutch.
The central position of assistant reducer is adjusted by washers, and then assembles the overrunning clutch.
Drilling pin holes between the assistant drive base and main engine foundation, then drive into pins after well adjusting the assistant reducer.
5.15.3 Assembly of main motor
Once both coupling halves (one flexible coupling and one overrunning clutch) which have been supplied for the main motor are assembled on the shaft ends of the main motor, the main motor can be mounted. It is lifted on the motor support by means of a hoist or any other adequate lifting tool and is aligned. The adjusting of central height is accomplished by washer, but the position of axial direction is adjusted by the round holes in the base. It is better to use thick washer not several thin
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washers when there is fair-sized warp. In order to adjust the position of the main motor, we can assemble casual adjusting bolts in several directions to adjust the position, and then they are dismantled after well adjusting.
Eventually, after all assembly works at the mill actuating device have been completed, use taper pins or dowel pins in according to mounting instructions of manufacturer, then the coupling guards have to be mounted and fastened.
5.16 Assembly of indicator
Each indicator is assembled under the three tension studs of the tension device, in order to control and master the height of layer in the mill.
The pointer is fastened on the tension stud by bolt, the position of the pointer is confirmed with the zero position on site, then arranges the circumference position in term of easily observed. After arrangement, make screwed hole on the frame.
5.17 Mounting of temperature measuring device for mill roller
Temperature measuring device for mill roller is to monitor temperature changes on bearings of mill roller so as to protect mill roller bearing.
Screw temperature measuring elements of temperature measuring device into mill roller shafts, and its conductive wire is laid from roller bracket and along air sealing pipeline.
Spot weld single pipe clamp on the air sealing piping, conductive wire of temperature measuring device goes into piping clamp and finally come out from the hole drilled at site which is at nearby of the frame, which connects air piping with mill.
It should be paid attention to when mounting temperature measuring device for mill roller, its guiding piping should be put on top of pipes of air sealing piping to prevent from erosion by wind and raw material.
6. Commissioning and test run 6.1 Commissioning personnel
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between supplier and customer.
1) Number of commissioning engineers, electric engineers and mechanical engineers.
2) Number of fitters, electric technicians and operators.
6.2 Equipment for commissioning and performance tests to be provided by the customer
1) A minimum four U pipes to measure the negative pressure in the plant (up to
1,500 mmH2O).
2) Pilot tube with inclined-tube manometer for air volume measurement
3) Electric thermometers (measuring range up to +500℃) for temperature measurement of gas, surfaces, and material.
4) Measuring sockets in the pipelines for measurements 1-3, to be fitted according to the instructions of the Pferffer commissioning engineer.
5) Sampling socket in the handling equipment collecting dust from cyclone and separator.
6) Screen for the screening of the feed material (5-150mm screen hole size). 7) Screen for the screening of the finished product (jet stream type screen, 63/90/200 micorons acc. To DIN).
8) Equipment to measure feed moisture and residual moisture.
9) Devices and equipment to weigh the feed material and to calibrate the weigh belt feeders.
10) Measuring instrument to measure real power or current measuring pliers (preferably real power measuring instrument).
11) Standard filter’s tools and possibly light –duty tackles. 12) Standard electrician’s tools.
6.3 Commissioning
6.3.1 Commissioning sequence
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the following.
1) Essential condition;
The commissioning of the mill may only be started by the engineer in charge of the commissioning once the assembly of the entire grinding plant is completed. In addition, the marginal prerequisites mentioned above have to be fulfilled. As it has been stated in the assembly instructions the entire measuring equipment is to be connected and all lubrication points provided with oil and grease. The electric assembly has to be completed, the wiring checked and the power supply ensured. 2) Preliminary adjustment
The mill remains disengaged until shortly before the mill is fed with material. The preliminary adjustment starts with an inspection of the plant by the commissioning engineer together with the customer’s chief commissioner and the engineers responsible for the machine and Electric assembly. The purpose of this inspection is to familiarize the engineer in charge of the commissioning with the local conditions within the plant and with the arrangement of the individual machines, drives and measuring points.
Subsequently the commissioning engineer determines the measuring points from where the variation of pressure within the plant is to be monitored during the commissioning by means of U-tube manometers. Corresponding measuring sockets are to be applied at these points. Furthermore, the position of the measuring sockets for the gas flow is determined with the help of a pressure head.
The commissioning engineer inspects the mill, i.e. who measures the roller position and the pressure housing according to the corresponding form
The commissioning engineer checks the oil at all hydraulic units grinding rollers and the gearbox. All points to be greased with lubricants are checked.
After the completions of these works the individual machines are put into operation, i.e. the machines are switched on without being interlocked with each other. The direction of rotation of the drive motors is being checked and the function of the
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machines supervised locally. When commissioning these individual units consult the operating instructions of the corresponding manufacturer. It is to be ensured that all fans have to run in fro a certain period of time. During this running-in the bearing temperatures are to be permanently checked. The hydraulic units are to run in for a certain period of time, too. Take care that there are no leakages. The unions are to be retightened, if necessary. Circulate the gearbox oil for the main gearbox oil supply for some time. Check the filters once and again. Check the claw clutch fro smooth functioning and set limit switches.
Put tension system in operation by putting pressure on the system, checking the tightness and by setting the pressure switches. The commissioning engineer determines the tension pressure at which the mill is to be started. The nitrogen pressure of the pressure accumulators is to be checked and set. See corresponding instructions! Set safety valves correspondingly. In any case observe the commissioning instructions of the manufacturer
Regarding the classifier drive, check the direction of rotation of the classifier drive motor when the classifier is disengaged. Also check the safety switch at the manual valve for proper functioning. Fill the piping (pressure pipeline) to go with the hydraulic motor with oil. Check the zero-position and the final position of the actuator. Now the unit may be put into operation. Check the speed of the classifier and adjust the safety valve during the running –up of the classifier. Check the automatic return movement of the actuator when switching off the motor. In any case the instructions of the manufacturer have to be observed.
3) Interlocking tests
All machines that have just been operated separately are now to be switched from the central switch panel in the correct sequence. Check all interlocking conditions indicated in the interlocking plans. It s to be guaranteed that during these interlocking tests all pressure switches, flow meters, limit switches etc. have to switch several times in order to enable the testing of all possible switch conditions within the plant.
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The complete plant is to be run several times under this condition. It is sensible to have the tests carried out not only by the commissioning engineer but also by the future operating personnel
These interlocking tests have to be carried out with greatest care. The engineer in charge of the commissioning has to ensure that all tests are carried out without any hurry to avoid any mistakes and to guarantee an impeccable operation of the complete interlocking system. Al defects in the interlocking are to be remedied and the interlocking has t be checked again. After the completion of these interlocking tests the plant is heated up several times (by means of the hot gas generator) in order to be able to check the operation of the plant under normal operating temperature. All units are to run for several hours. Qualified personal is to permanently supervise the plant on the spot.
4) Preparation for the commissioning of the plant with material
Before the operation of the mill with material may be stated, a certain initial material charge has to be brought into the mill. For this purpose the material has to be filled into the mill feed bins (initially only partly later on more and more) and conveyed via the transporting equipment to the mill. It is then fed in the area between air guide cone and housing. This area is to be filled as much as possible. Now the material has to be filled in the mil centre and in the grinding track. First a layer of approximately 30-50mm is to be filled onto the grinding track between the grinding rollers. Then the rollers have to be brought over the material by suing the auxiliary drive. It is absolutely necessary to take care that during the turning of the track no personnel stays in the mill and that the reducer oil supply functions perfectly.
By this means a grinding bed of 70 mm is brought onto the grinding track, depending on the mill size. This grinding bed is meant to prevent the machine from emptying during the first minutes of the start-up. Now all feed conveyors are to be emptied via a corresponding chute. Later on they are to be charged again with the amount of material the commissioning engineer determines for the first start-up. Prior
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to this last filling the calibration of the metering units has to be completed. 5) First start-up of the mill
Prior to the first start-up the plant is to be heated very carefully. Try to quickly reach a temperature of approximately 100℃ measured downstream of the mill and keep it for about 1 to 1.5 hours. During this beat-up all units within the grinding plant have to be in operation and supervised.
Once the plant is heated this way increase the exhaust gas temperature to approximately 110-120℃ and switch in the mill auxiliary drive. Set the gas volume downstream of the mill to the gas volume determined by the commissioning engineer. After the auxiliary drive has been running for the appropriate time (approx. 1 min., this is also to be determined by the commissioning engineer) the main drive is switched on.
The commissioning engineer decides at what time the material feed is to be started. Usually immediately after switching on the main drive the material feed may be started in order to prevent an emptying of the mill. During this period all units, especially the power consumption of the mill man drive, the vibration monitoring and the mill exhaust gas volume are to be observed. An attempt is to be made at arriving as quickly as possible at a normal and continuous operation. This includes an increase in the hot gas volume within a short period of time to meet the heat requirement of the mill.
The mill is run for a certain period of time with the output determined by the commissioning engineer (this output is to le approximately 20-30% below the guaranteed output). Carry out exhaustive measurements within grinding plant during this period of time. Ensure that the plant is thoroughly supervised on the spot by competent personnel.
After the mill has been in operation for approximately 50 hours the plant is meticulously inspected. During this inspection all unions within the grinding plant are to be checked. The unions of the wear parts at the grinding bowl and grinding rollers
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and the unions of the grinding bowl on the gearbox are tightened to the stipulated torque. All oil fillings have to be checked. Check grinding rollers and pressure frame. Measure again grinding rollers and pressure frame.
6) Output test
On the basis of the operating results which have been obtained during the first trial run the engineer determines the proceedings for the output tests. In these tests the grinding output is increased to the guaranteed output. Once the guaranteed, output has been reached. A date convenient to the final customer is agreed upon and the acceptance test is carried out. Subsequent the acceptance record is signed.
With the acceptance test being carried out the complete plant is once again meticulously inspected by the commissioning personnel and finally handed over to the operating personnel.
Leaflet: Commissioning of MLS3424A Grinding Plants 1) Position of grinding rollers
a. Check obliquity
b. Check position of the center 2) Check oil filling of grinding rollers 3) Seal air
a. check direction of rotation of seal air fan b. check pressures
c. check sea air switch off 4) Tension hydraulics
a. check nitrogen pressure of accumulators b. check oil level
c. check oil level indicator
d. set limit switch at shut off-valve e. set four way cock to operating position f. check direction of rotation of oil pump motor
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g. test pressure of tension hydraulics h. se t safety –valve
i. check and set minimum and maximum switches j. set throttle at pressure manometer
5) Mill reducer
a. Control oil level
b. Check immersion heater electrically, if any
c. Set and check minimum and maximum contact at contact thermometer. d. Switch on oil filter
e. Measure amount of cooling water f. Vent oil cooler
g. Check direction of rotation of oil pump
h. Check oil flow control instrument for proper functioning i. Check oil level in segmented thrust bearing
j. Check electric interlocking with main and auxiliary drive 6) Overrunning clutch
a. Check claw clutch for smooth functioning b. Set stroke
c. Check solenoid valve
d. Set and check master pressure gauge 7) Auxiliary drive
a. Check gearbox oil level b. Check direction of rotation
c. Observe switching sequence and interlocking auxiliary drive-coupling –main drive
8) Main drive (individual)
a. Check direction of rotation b. Trial run with starter
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9) Classifier
a. Check grease filling of classifier bearing b. Check direction of rotation of driving motor c. Check direction of rotation of cooling motor d. Check oil level of planetary reducer
e. Switch unit on
f. Check direction of rotation of classifier
g. Check electric interlocking together with complete plant 10) Set all flaps in the pipeline
11) Mill fan
Put into operation according to instructions of the manufacturer 12) Air valve
Put into operation according to instructions of the manufacturer 13) Turn mill by means of auxiliary drive
a. Check again inclination of rollers b. Set grinding bed indication 15) MPS vertical roller mills
Tension hydraulics for grinding rollers
The operating pressure of the tension hydraulics is to be in a certain relation to the nitrogen pre-pressure in order to prevent damages at the rubber bladder of the nitrogen accumulator. The operating pressure for normal operation is to be limited to:
P=3 x Pst as maximum value P=1.5 x Pst as minimum value
Pst =nitrogen pressure P = operating pressure
15) Measurement of grinding roller position See figure 7
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7.1 Trouble removing
7.1.1 Mill running roughly
Heavy rumbling (extremely strong vibrations) means imminent danger to the mill reducer. Therefore the mill has to be shut down immediately. Rough run may be caused by too little material or by overloading the mill.
7.1.2 Fill level of feed bin too low
In case the mill has to be stopped because of the feed bin containing too little material there is a danger that the conveyors feeding the mill also run out of material. In this case these supply units up to the mill feeder must be fed with material without delay. Otherwise the grinding bed will become thin very fast and the mill will start rumbling. This might damage the reducer very badly.
7.1.3 Start-up of mill without grinding bed
after repair work or if grinding bed due to lack of material supply was as less as 0-30mm prior to shutdown.
The mill has to be filled with material as follows: a. Gear oil pump on.
b. Adapt overrunning clutch. c. Seal air fan on.
d. Auxiliary drive on.
e. Rotary lock or three –flap gate lock on. f. Switch on supply devices.
7.1.4 Filter outage
In case high dust emission is shown on the indicator, mill output must be reduced or the mill must be shut down.
7.1.5 Outage of feeding device
In case one feeding device is out of order the grinding plant may still be operated for a few minutes. However, mill supply by the remaining feeding devices must be increased to such an extent that the mill does not run out of material.
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In case the supply units from the pre-bin to the mill are out of order the grinding plant must be switched off before differential pressure and power consumption of mill motor reach the minimum value.
7.1.6 Outage of mill fan
In case of outage of discharge devices of cyclone or filter the plant has to be switched off immediately. In no case must the mill be kept running because the cyclones would be clogged very fast and it is difficult to empty them.
7.1.7 Fine material feeding unsmooth
The mill must be stopped when segregator and filter discharge port break off. 7.1.8 Outage of hot gas supply from kiln
In case the exhaust has fans of the kiln are out of order the grinding plant should be shut down since otherwise the mill will be overcharged and start rumbling.
7.1.9 Differential pressure too high
Feed to be reduced very much immediately. Watch differential possible causes: a) Material feed too high due to malfunction of control of feeding devices. b) Nozzle ring located at the periphery of the grinding bowl is clogged. c) Air volume in mill too low or inconstant.
d) Setting of classifier much too fine. 7.1.10 Differential pressure too low
Possible causes:
a) Outage of material feed. b) Wrong indication.
This is the case if the remaining pressure indications ahead and downstream of the mill are o.k. Mill operation may be continued. However, feed has to be changed from automation to manual operation. 7.1.11 Tension pressure dropping
Possible causes:
