FL Smidth - Mill Bearing

Mills Main bearing (fixed or movable)

Mounting, operation and maintenance

Approved date: Created by: Approved by:

Doc. No.: 21791-20-2.0

MILLS 21791-20-2.0

List of contents: Page: 1

TYPE OF BEARING ......................................................................................... 4 1.1

2

................................................................................................................... 4 1.1.1 ....................................................................................................... 4 1.1.2 ....................................................................................................... 4 CHECKING OF BEARING LINER ........................................................................ 4

3

2.1 ................................................................................................................... 2.2 ................................................................................................................... 2.3 ................................................................................................................... 2.4 ................................................................................................................... 2.5 ................................................................................................................... MOVEABILITY OF LINER .................................................................................

4

3.1 ................................................................................................................... 5 3.2 ................................................................................................................... 6 ALIGNMENT AND GROUTING OF BASEPLATE ...................................................... 6

5

4.1 Position of main bearing ................................................................................. 4.2 Alignment ..................................................................................................... 4.3 Grouting ....................................................................................................... COOLING .....................................................................................................

6 6 6 7

6

5.1 ................................................................................................................... 5.2 ................................................................................................................... 5.3 ................................................................................................................... 5.4 ................................................................................................................... LUBRICANTS ................................................................................................

7 7 7 7 8

7

6.1 Oil qualities ................................................................................................... 8 6.2 Ring-oiling bearings. ...................................................................................... 8 PREVENTION OF OIL SPILLAGE ........................................................................ 9

8

7.1 Oil scrapers. ................................................................................................. 9 7.2 Oil distribution channel. .................................................................................. 9 7.3 Seals............................................................................................................ 9 HIGH–PRESSURE OIL STARTING PUMPS ........................................................... 10

9

8.1 Mode of operation ......................................................................................... 10 8.2 Mounting of high-pressure oil pipes. ................................................................ 10 CIRCULATION PUMPS .................................................................................... 10

4 4 5 5 5 5

10 TEMPERATURE CONTROL ............................................................................... 11 11 Appendices ................................................................................................. 11 List of appendices: Appendix Appendix Appendix Appendix Appendix Appendix Appendix Appendix

2/16

1 2 3 4 5 6 7 8

Bearing liners, placing on journal ...................................................................11 Table, for 180° bearing liner .........................................................................12 180° Bearing liner........................................................................................13 Table, for 120° bearing liner .........................................................................14 120° Bearing liner........................................................................................15 Table, longitudinal clearance .........................................................................15 Longitudinal clearance ..................................................................................16 Thermo phial, positioning..............................................................................16 The information transmitted by this document is the proprietary and confidential property of FLSmidth and may not be duplicated, disclosed or utilized without written consent from FLSmidth.

MILLS 21791-20-2.0 List of figures: Figure Figure Figure Figure Figure

1 2 3 4 5

Bearing liners, placing on journal ...................................................................... 180° Bearing liner ........................................................................................... 120° Bearing liner ........................................................................................... Longitudinal clearance ..................................................................................... Thermo phial, positioning .................................................................................

11 13 15 16 16

List of tables: Table 1 Table, for 180° bearing liner .............................................................................. 12 Table 2 Table, for 120° bearing liner .............................................................................. 14 Table 3 Table, longitudinal clearance .............................................................................. 15 Text reference is made to the following instruction manuals: Assembly of pipes by means of Ermeto couplings Mills. Pump station for lubrication of mill bearings Oil level switch

27091 29491 37091

The information transmitted by this document is the proprietary and confidential property of FLSmidth and may not be duplicated, disclosed or utilized without written consent from FLSmidth.

3/16

MILLS 21791-20-2.0

NOTE! The present instruction manual is concerned with the situations, which, according to our experience of FLSmidth, are the most likely to occur. An exhaustive enumeration of all conceivable situations, which may occur during the operation of the plant/machine/equipment cannot be provided. Consequently, if a situation should arise, the occurrence of which is not foreseen in the instruction manual, and which the client is/or feels unable to handle, we would recommend that FLS is contacted without undue delay for advice on appropriate action.

FLS CHECK in the instruction manual means that the FLS chief erector in charge must inspect and approve the mounted parts before mounting may continue.

1 TYPE OF BEARING 1.1 Main bearings are designed as fixed or moveable bearings. 1.1.1 A fixed main bearing, which is mounted at the drive end of the mill, serves as locating bearing. The base of the bearing is secured to the baseplate by means of screws. Between bearing and baseplate a shim is to be fitted to allow readjustment of the bearing height, in case the foundations should settle. 1.1.2 A moveable main bearing rests on rollers placed on the baseplate, so that the bearing can move according to the thermal expansion of the mill body. This thermal expansion will have to be taken into account during mounting. The maximum longitudinal expansion of the mill body is indicated on the erection drawing.

2 CHECKING OF BEARING LINER 2.1 The bearing is equipped with a moveable liner (bottom liner), which was given a true cylindric shape in shop, with a clearance in relation to the diameter of the journal. Therefore, the liner must theoretically bear along a generatrix at the bottom of the bearing, and the bearing must not be scraped for the purpose of changing the extention of the contact area in the circular direction, because this will influence tolerances and clearances. 2.2 Check that clearance "s" between journal and liner is within the values in column "Liner-trunnion, min. – max. theoretical". See Appendix 2, figs. 3A and 3B for 180° and Appendix 3, fig. 3C for 120° bearing liner. Also check the longitudinal clearance ”s1”. Values are specified in table on Appendix 4. 4/16


MILLS 21791-20-2.0 Also check that the circular edges of liner and journal have the correct roundings. Radius ”R” is specified in the table on Appendices 2 and 3, see also Appendix 4, fig. 4. Check that the axial faces of the bearing liner are provided with lubrication pockets if the mill girth gear rim and pinion(s) have helical teeth. 2.3 Check the support of the bearing by applying a thin layer of marking colour on the trunnion journal and placing the liner on the journal as shown on Appendix 1, fig. 2. The liner must indicate nearly full contact over the entire bearing length along a generatrix (theoretical contact). In practice, the contact area has a certain extension in circular direction. The contact area must be parallel to the generatrices of the liner. If the marking only shows support either at the edges of the bearing or at the centre of the bearing, (i.e. journal or liner are not absolutely cylindrical) some scraping must be done to obtain a parallel contact area (changing the cylindric shape of the bearing as little as possible). If the contact is very poor, report to FLS before beginning to scrape. FLS CHECK 2.4 It is very important that the rules for dimensions of clearance are adhered to, when the mill is filled with the full charge of grinding media and material, because too small a clearance will prevent forming of a sufficiently thick oil film between journal and liner. In other words, too small a clearance will contribute to running hot of the bearing. If a bearing runs hot, the reason may be something else than too small clearance. Therefore, to begin with, check whether the lubrication system works properly, whether the correct oil quality has been used corresponding to the service temperature of the bearing and whether the cooling water volume and the inlet temperature of the water are as foreseen, before considering to scrape the liner. If the aforementioned conditions are in order, check the size of the clearance and possibly scrape the liner sides somewhat so as to create a large clearance and a better possibility for the formation of a sufficiently thick oil film. 2.5 The area around the oil hole must be scraped down within a circle, the diameter of which is equal to ¼ of the width of the liner so that the trunnion does not touch the liner within this area, see Appendix 1, fig. 1.

3 MOVEABILITY OF LINER 3.1 The bottom liner rests in a ball socket and must be freely moveable. As the joint faces of the liner and the bottom section are spherical surfaces, the liner is able to adapt itself to the journal when the mill is placed in the bearings, although the bearings are not mounted accurately horizontal and at right angles to the mill axis. FLS CHECK


5/16

MILLS 21791-20-2.0 3.2 When mounting, smear the spherical surfaces of the liner with "MOLYKOTE" or similar approved lubricant. There is a stop on either side of the bearing which prevents the liner from turning round. There must be a clearance of 1-2 mm between liner and stop. Normally there is no movement between the spherical surfaces when the mill is operating.

4 ALIGNMENT AND GROUTING OF BASEPLATE 4.1

Position of main bearing To obtain correct positioning of the baseplates of the main bearing(s), proceed as follows: On the finished mill body, measure the distance between the vertical centrelines of the trunnion journals (or journal and slide ring). The measured distance plus an allowance for the longitudinal heat expansion of the mill (see erection drawing), is the distance there must be between the centrelines of the baseplates. FLS CHECK

4.2

Alignment For alignment, insert iron wedges or pieces of bar iron between baseplate and foundation, distributing them along the entire edge of the baseplate, so that there is no deflection of the baseplate when same is loaded. Place bearing bases with liners and rollers/intermediate plates on the baseplates and adjust the height accurately so that the mill is positioned horizontally at a max. deviation of 0.6 mm per metre. The vertical planes of symmetry of the bearings must be at right angles to the horizontal centre plane of the mill, also at a max. deviation of 0.6 mm per metre. Fasten the baseplate by means of the foundation bolts. Check the alignment and make a fine-alignment, if required. FLS CHECK

4.3

Grouting To begin with, grout the holes around the foundation bolts. A concrete edge must be placed along the sides of the baseplates before starting to grout under the baseplates, so as to prevent the grouting material from escaping. If the holes for grouting the baseplates are located under the bearing bases, these must be removed before starting to grout. It is very important that the cavities of the baseplates are grouted entirely with concrete (without air bubbles) on account of the supporting capacity of the bearings. The calculation of the bearings implies that no deflection can occur in any supporting parts of the bearing. FLS CHECK Up to now the grouting material has always been concrete. During recent years, however, special materials have become available for grouting machine foundations which all are characterized by a small or no shrinkage coefficient at all during setting.

6/16


MILLS 21791-20-2.0 Instead of concrete, one of these acknowledged grouting materials can be used. In case of doubt FLS should be notified or asked for advice. Having aligned the fixed bearing, secure its position on the baseplate by means of adapted or special filler pieces included in the delivery.

5 COOLING 5.1 Mills designed for dry grinding always have water-cooled bearings, whereas no particular cooling is normally provided for the bearings of mills for wet grinding, apart from the cooling caused by the passage of the stream of material through the hollow trunnion. The cooling water inlet is situated at the lowest point of the base of the bearing, and the water is forced through a pipe-and-hose connection from the base of the bearing to the moveable bottom liner, from where it flows to a sewer. A three-way cock on the inlet side is to be fitted in such a way that, when the supply of cooling water to the bearing is cut off, a connection is opened from the bearing, through the three-way cock to the sewer, so that the bearing is partly emptied of water and is thus protected against frost bursting. A regulating cock will have to be fitted in the water line, ahead of the threeway cock, for controlling the quantity of water to the bearing. 5.2 On the side on which the cooling water inlet line is located there is a pipe for venting of the water compartment of the liner (or of the water compartment of the bottom section, since old-type bearings are also provided with water cooling in the bottom section). Check that this venting line is provided with a blank-off with a 3-4 mm hole. Without blank-off the majority of the cooling water will by-pass the bearing. FLS CHECK 5.3 For the fixed main bearing the water line can be connected directly to the three-way cock for cooling water to the bearing, but for the moveable bearing there must be hose connection between the water line and the three-way cock. It is very important that the water lines inside the main bearing are fitted following the instructions given in the parts list sketch or erection drawing. 5.4 Prior to filling oil into the bearing, the water lines must be pressure-tested with the water pressure which is used at the plant. This can be done by plugging the outlet pipe for the bearing and leaving the system under water pressure for a couple of hours. Do not forget to remove the plug after testing. Check all joints so as to avoid the cooling water from leaking out into the oil reservoir of the bearing. FLS CHECK


7/16

MILLS 21791-20-2.0

6 LUBRICANTS Having mounted the bearing, fill oil into the bearings until the oil level reaches the middle of the oil gauge glass. 6.1

Oil qualities Oil products corresponding to the FLS symbols used for lubricants appear from the FLS Key to Lubricants 36501 which is forwarded separately. To lubricate main bearings use oils types FLS EP-320 and EP-460 or FLS CY460 and EP-680 or FLS SY-460. The oils are applicable within their individual temperature range as specified below. FLS SY-460 is a synthetic oil characterized by a high viscosity index, making it less temperature-sensitive than FLS EP-680. When choosing an oil, an estimate must be made of which service temperature the oil will have. Same depends on the ambient temperature, the cooling water volume and temperature and the material temperature. Service temperature of oil

Oil quality

40-65°C

FLS EP-320

65-85°C

FLS EP-460/CY-460

85-95°C

FLS EP-680/SY-460

The oil service temperature must be measured on the upward-moving side of the trunnion. See Appendix 5. Thermo phials, with which the temperatures are measured, must be set to give alarm and stop the mill if the oil service temperature exceeds the aforementioned maximum temperatures by 5°C. If the service temperature turns out to become higher than initially estimated before start-up, the reason for that must be considered. 1. Have the above estimates regarding temperatures and cooling water volume been correct or do the actual conditions deviate? If they deviate, can anything be done to improve the conditions? 2. Are the contact in the bearings and the other mechanical conditions in order? If the service conditions cannot be improved and the mechanical conditions are in order, the oil must be replaced by one of the above oil grades suitable for the actual service temperature. It is emphasized that the temperature measured by means of the thermo phials is the decisive one. If in doubt, consult an approved oil company and report to FLS. See also instruction manual for mill maintenance. 6.2

Ring-oiling bearings. Use FLS EP-220 for oil temperatures up to 40°C. If the oil temperature however drops so low (below 30°C), that it is difficult to pull round the oil ring, FLS EP-150 should be used which is a thinner oil.

8/16


MILLS 21791-20-2.0

7 PREVENTION OF OIL SPILLAGE 7.1

Oil scrapers. Oil spillage must be avoided, because otherwise there is a risk of emptying the bearing of oil and running it hot. The oil will also spoil the foundation. At each end of the cap of the bearing there is an oil scraper, which is guided by a screw. The oil scrapers are to be freely moveable up and down and must not be fixed. The oil scrapers are reversible so that they can serve both directions of rotation. The oil scrapers tread on the machined collar at each end of the trunnion journal and serve to scrape the oil on to the journal. The machined collars must be polished smooth, free from toolmarks and rust. The scrapers are made of rubber and are easily renewable. The liner is provided with oil guards of plate (brass). Final adjustments and adaption of the guards must be made during mounting.

7.2

Oil distribution channel. Bearings for lubrication by circulation and mild steel housing are manufactured with an oil distribution channel which is welded to the bearing top section. There may be different types of oil distribution channels. It is important that the oil distribution channel is horizontal, because otherwise it may cause oil spillage and an uneven distribution of the oil on journal and liner. Therefore, always check the oil distribution channel position before putting the mill into operation. If necessary, adapt the overflow edge of the channel by grinding. Check that the four 6 mm holes in the bottom of the oil distribution channel are not obstructed. FLS CHECK It is important that the holes are clean and have free passage, because the channel must be emptied through the holes if the oil supply fails.

7.3

Seals. On either side the bearing housing is provided with a seal which prevents the oil from leaving and dust from entering the bearing. Depending on the type of bearing, there are two different designs. One design features a seal consisting of a double-lip rubber ring fitted innermost, and a felt ring fitted outermost as well as two steel rings for mounting and fastening. The seal rings must be concentric around the sealing belts of the trunnion. The max. permissible eccentricity is 2 mm relative to the bore of the bearing housing. If the eccentricity is bigger than 2 mm, an adaption must be made which normally consists of boring the holes for the fastening screws in the steel rings. In case of big eccentricity, more than 6 mm, report to FLS who will decide on which modifications must be made in this case.


9/16

MILLS 21791-20-2.0 The other type of seal is designed so that it can permit an eccentricity of up to 15 mm between bearing housing and trunnion. This seal consists of a rubber profile, a felt ring, a strapping band and a retainer ring. For type of seal, see erection drawing for main bearing.

8 HIGH–PRESSURE OIL STARTING PUMPS 8.1

Mode of operation The main bearings are normally provided with high-pressure oil starting pumps, which serve as an additional safety device during starting. Moreover they are used for mills with barring gear units. High-pressure oil starting pumps are to force oil between trunnion and liner before the mill is started so as to ensure a suitable oil film during the first half revolution of the mill. Moreover, the high-pressure oil starting pump is to ensure a suitable oil film during slow barring of the mill. So as to help the oil to penetrate between trunnion and liner, a clearance has been scraped into the liner around the oil pipe, having a diameter of abt. ¼ of the liner width, see Appendix 1, fig. 1. It is not possible to specify beforehand which oil pressure will be obtained. This depends entirely on the nature of the surface of trunnion and liner. Small dents in these surfaces make the oil more easily escape, resulting in a lower oil pressure. In practice the oil pressure may vary from abt. 10 bar to about 120 bar without any risk of running the bearing hot. To ensure the aforementioned oil film, the high-pressure oil starting pump must be interlocked electrically with the main motor of the mill, so that same cannot be started before the high-pressure oil starting pumps are running. The high-pressure pumps must always operate when barring the mill!

8.2

Mounting of high-pressure oil pipes. The high-pressure oil pipes in the main bearings must be assembled with Ermeto fittings, see separate instruction manual. The pipe joints must be pressure-tested with the high-pressure oil starting pump, before the bearing top section is mounted. FLS CHECK

9 CIRCULATION PUMPS The circulation pump is a gear wheel pump yielding about 15 l/min. The oil is pumped to the bearing journal via an oil distribution channel which is welded to the inside of the bearing top section. It is important that the overflow edge of the channel is absolutely horizontal and that the four 6 mm holes at the bottom are not obstructed. (See sub-section 7.2). At one end of the oil distribution channel there is an oil level switch which is to ensure that there is still sufficient oil supply to the bearing during mill operation. Should the oil supply fail or become too low for some reason or other, the oil distribution channel will be emptied of oil through the mentioned 6 mm holes, and the oil level switch will then stop the mill and give alarm. 10/16


MILLS 21791-20-2.0 On a different type of bearing the oil level switch is placed in a flow box which is located on top of the bearing. The oil level switch function must be checked in connection with mill trial-running. See separate instruction manual for oil level switch.

10 TEMPERATURE CONTROL The bearings are provided with thermo phials, see Appendix 5. Set the temperature contacts for both bearings for the maximum service temperature of the oil used +5°C. When the alarm has sounded and the mill has stopped, find the reason before restarting the mill. See also sub-section 6.1: Oil qualities.

11 Appendices Appendix 1 Bearing liners, placing on journal

Figure 1 Bearing liners, placing on journal


11/16

MILLS 21791-20-2.0

Appendix 2 Table, for 180° bearing liner 180° liner Diameters Bearing

2) Trunnion H8

0

Liner bore

+1,000

Rounding, Fig.4

1) LinerMandrel Min.-max. theoretical

Liner Trunnion Min.-max. theoretical

To be measured , see Fig.3

R 3) Trunnion

+0,670 500 +0,600

0,05-0,14

0,29-0,40

A

12

13

Mandrel

R Liner

500

500

550

0 550 -0,110

+1,000 550 +0,800

+0,670 550 +0,600

0,05-0,15

0,30-0,41

A

12

13

650

0 650 -0,125

+1,000 650 +0,800

+0,670 650 +0,600

0,05-0,16

0,31-0,44

A

12

13

800

0 800 -0,125

+1,200 800 +1,000

+0,890 800 +0,800

0,03-0,12

0,30-0,40

B

12

13

1000

0 1000 -0,140

+1,200 1000 +0,800

+0,890 1000 +0,800

0,03-0,12

0,30-0,40

B

12

13

1100

0 1100 -0,165

+1,200 1100 +1,000

+0,900 1100 +0,800

0,03-0,12

0,30-0,41

B

12

13

1200

0 1200 -0,165

+1,400 1200 +1,000

+1,100 1200 +1,000

0,03-0.12

0,36-0,47

B

12

13

1400

0 1400 -0,195

+1,500 1400 +1,300

+1,120 1400 +1,000

0,06-0,18

0,46-0,60

B

12

13

1600

0 1600 -0,195

+1,600 1600 +1,300

+1,200 1600 +1,000

0,04-0,15

0,32-0,44

B

17

18

-0,110

500

Clearance “s” between

+0,800

Table 1 Table, for 180° bearing liner 1) These clearances to be adhered to and made in shop. 2) There are old trunnions with slightly differing tolerances; but the difference in clearance liner – trunnion is so small that it is of no practical importance. 3) If the fixed bearing is to absorb axial loads from countershaft with skew gears, the rounding on the trunnion is made with radius R10 and the liner with R15 in order to improve the lubrication of the axial surface.

12/16


MILLS 21791-20-2.0

Appendix 3 180° Bearing liner

Figure 2 180° Bearing liner


13/16

MILLS 21791-20-2.0

Appendix 4 Table, for 120° bearing liner 120º liner Bearing

Diameters Trunnion

Liner bore

Clearance “s” between Mandrel

H8

1) Liner-mandrel

Liner-trunnion

Min.-max.

Min.-max.

theoretical

theoretical

Rounding, Fig.4

To be measured, see Fig,3

R

R

2)

Liner

Trunnion

1200

0 1200 -0,165

+1,400 1200 +1,200

+1,100 1200 +1,000

0,02-0,07

0,21-0,28

C

12

13

1400

0 1400 -0,195

+1,500 1400 +1,300

+1,120 1400 +1,000

0,03-0,10

0,24-0,32

C

12

13

1600

0 1600 -0,195

+1,600 1600 +1,300

+1,120 1600 +1,000

0,04-0,12

0,25-0,35

C

17

18

1800

0 1800 -0,230

+1,800 1800 +1,000

0,29-0,41

C

17

18

2000

0 2000 -0,230

+2,000 2000 +1,630

0,34-0,46

C

17

18

2240

0 2240 -0,280

+2,240 2240 +1,800

0,39-0,54

C

17

18

2500

0 2500 -0,280

+2,500 2500 +2,060

0,44-0,60

C

17

18

2800

0 2800 -0,330

+2,800 2800 +2,260

0,50-0,68

C

17

18

3150

0 3150 -0,330

+3,150 3150 +2,610

0,58-0,78

C

17

18

Table 2 Table, for 120° bearing liner 1)

These clearances to be adhered to and made in shop.

2)

There are old trunnions with slightly differing tolerances; but the differences in clearance liner – trunnion is so small that it is of no practical importance.

3)

If the fixed bearing is to absorb axial loads from countershaft with skew gears, the rounding on the trunnion is made with radius R10 and the liner with R15 in order to improve the lubrication of the axial surface.

14/16


MILLS 21791-20-2.0

Appendix 5 120° Bearing liner

Figure 3 120° Bearing liner

Appendix 6 Table, longitudinal clearance Axial clearance between liner - trunnion, Fig.4. Bearing width

Clearance

B

S1

above

up to

Min.-max. theoretical

180

250

0,170-0,427

250

315

0,190-0,481

315

400

0,210-0,529

400

500

0,230-0,577

500

630

0,260-0,650

630

800

0,290-0,735

800

1000

0,320-0,820

1000

1250

0,350-0.935

1250 1600 0,390-1,085 Table 3 Table, longitudinal clearance For rounding radius R, see Figures 2 and 3.


15/16

MILLS 21791-20-2.0

Appendix 7 Longitudinal clearance

Figure 4 Longitudinal clearance

Appendix 8 Thermo phial, positioning

Figure 5 Thermo phial, positioning

16/16


FL Smidth - Mill Bearing

Recommend Documents