Oil film bearings

Referens-list

EZTM JSC is unique company in Russia, Commonwealth of Independent States and West Europe , providing complex supply of OFB.

OFB is used as roll support of wire rolling, section mill and rolling mills. Presence of supporting oil skim between rubbing surfaces excludes mechanical contact and defines basic characteristics of bearings:

-small rub coefficient during set working schedule  is 0,001-0,005.

-high tolerant speed;

-high tolerant capacity;

-small sensitivity to momentary dynamic  loads.

OFB production was mastered in 1950. Nowadays bearings are used at many plants of ferrous and non-ferrous metallurgy  in Russia and in 18 countries of the world. Among constant customers in 2005 the orders were placed by India, Slovakia, Ukraine, Russian plants: Severstal, NLMZ, ZSMZ, Izhstal and others.

Safe and continuous work of OFB is provided by perfect construction, high accuracy  of production of main details and forced feed of clear oil in working zone from centralized lubrication system.

Bearing production is arranged in specialized shop by well qualified specialists at unique machines of Russia and foreign.  Polishing and super finish of outer and inner diameter  is made at special machines of Japan company SHIBAURA with micron accuracy.

OFB can be supplied in scope and separately by parts as spare parts to before supplied bearings.

Basing at multi year experience in design, production and assembly of OFB, EZTM JSC specialists can provide following services:

-preconstruction consultations,

-providing of basic bearing documentation for connection with chocks and rolls at construction stage;

-coordination of working drawings before start of production of connected units,

-consultations, requirements to workrooms for bearing revision and repair;

-help in stuff teaching of assembly rules and bearing exploit;

-supervision, assembly, start to work of OFB.

OFB production quality Management system is certificated by British Institution of Standards.

Certificate of Conformance #FM90597 dt. 27.11.2004.

Bearing size is in range (nominal sliding diameter) from 140 to 1800 mm.

Every bearing is closed, assembled in chock unit, easily mounted at roll neck. Construction provides long life and minimal cost of maintenance.

Basic installation data is given in table.

OFB diameter d	Roll diameter Dmin	Dk	l			T			Load, ts, max			Turn per/ minute, max
			l/d 0,6	l/d 0,75	l/d 0,9	l/d 0,6	l/d 0,75	l/d 0,9	l/d 0,6	l/d 0,75	l/d 0,9
140	225	120	85	105		110	120		24	30		4000
180	245	150	110	135		120	130		40	50		2500
200	275	170	120	150		130	145		48	60		2000
220	290	190	130	165		140	155		57	73		2000
250	335	220	150	190		150	170		75	95		1600
275	370	240		205			180			113		1500
300	390	260		225			195			135		1500
320	430	280		240			210			154		1000
350	450	310		260	320		225	255		182	224	1000
400	520	350		300	360		245	275		240	288	1000
450	580	390		340	400		260	310		306	360	1000
500	640	430		375	450		320	360		375	450	1000
550	710	480		415	500		345	390		457	550	1000
600	770	530		450	530		360	400		540	636	1000
650	840	570		490	600		380	430		637	780	700
710	900	630		530	630		410	470		753	895	700
800	1030	710		600	710		450	505		960	1136	500
850	1090	760		640	750		470	525		1088	1275	500
900	1220	800		670	800		525	590		1206	1440	500
1000	1280	890		750	900		550	625		1500	1800	400
1120	1400	1000		840	1000		600	680		1882	2240	400
1180	1460	1050		880	1060		635	725		2077	2502	400
1320	1640	1180		1000	1180		710	800		2640	3115	400
1400	1710	1260		1060	1260		710	810		2968	3528	200
1500	1800	1360		1120	1360		720	840		3360	4080	200
1600	1900	1450		1200	1450		740	860		3840	4640	200
1700	2000	1550		1280	1500		790	900		4352	5100	200
1800	2140	1650		1360	1600		830	950		4896	5760	200

OFB are horizontal and vertical according to working conditions.

Radial loads are taken by bush leaf with babbit  layer, and axis loads- by unit with radial support frictionless bearing (fixed OFB), less support unit ( free OFB) bearing takes only radial loads and lets compensate due to bush pin movement with roll relatively to bush leaf –the heat expansion and assembly inaccuracy.

To increase OFB work long life in condition of frequent start  and speed up of mill without decrease of roll pressing force – the construction of hydraulic dynamic OFB is worked out. (HD OFB).

HD OFB differs from OFB only by construction of bush leaf.

In HD OFB, bush leaf has special pockets at working surface, where oil is fed under high pressure through throttle ( -700 atmospheres and more) from special system of lubrication. Oil under high pressure balances outer load when motionless rolls and low rolling speeds.

HD OFB comprises hydraulic dynamic and hydraulic static principles of oil layer creation, which separates rubbing surfaces, i.e. in such bearings the work at any speed is provided, including zero speed also.

Vertical OFB are used in section and wire mills working stands with vertical rolls. Such OFB differ from OFB for horizontal rolls only by sealing arrangement from roll barrel side and oil feed and sink channels placement.

Liability and long life of OFB greatly depends on lubrication systems.  OFB lubrication system consists of pump station, piping with fittings and devices, including mechanisms and devices, providing heat and filtration, cooling and feed of oil in heating main, and also collection and dreg of waste oil fed from OFB in sink main in deposit tank.

OFB enter oil pressure  0,8-1,2 kg/cm².

Oil temperature at enter 38-40*C

                         at exit (max) 115*C

Lubrication system is for group of stands, OFB which work at one sort of oil.

Rolling mill can be served by several lubrication stations.

All lubrication systems are equipped with control-measure devices, alarm and block of stand electric motors.

Information is given at mill control panel and at device installation panels.

If deviation of given parameters happens the preventing and emergency alarm is given in lubrication system (by signal and light).

Press-tank provides oil feed  in bearings when pumps fail to work for a time, needed for mill full stop. Electric motors of stands main drive is blocked with pump motors in such way that its start is possible only if full intactness of lubrication system ( when its turned on and provides normal pressure).

HD OFB lubrication system except above said system of low pressure must include system of high pressure.

In high pressure system must be included pumps of high pressure  (up to 1000 atmospheres), check and safety valves, control devices, piping and throttle system.

Special oils И-ТП-С are used for lubrication in rolling mills. Depending on kinematical velocity with temperature 40*C the oils of such brands as И-ТП-С 46,220,320 and 460 are used (kinematical velocity mm/s) 41,5-50,5; 198-242; 288-352 and 400-520.

1. deposit tank
2. pump with electric motor
3. disk filter
4. cassette filter
5. pressure tank
6. heat exchanger
7. working stands OFB
8. piping and fittings
9. magnet filter
10. system control panel, control-measuring and signal devices.
11. alarm device at mill panel
12. separator

SEAL ASSEMBLY FOR OFB WITH V-SHAPE CUFFS

New construction is worked out of seal assembly for OFB dia. 140…400 mm, preventing oil leakage from bearing and liquid leak into its cooling roll. V-shape butt cuffs are used in such construction in connection with nozzle from non-corrosive steel and fixed at bush pin. Such seal assembly are more liable than the assembly used in earlier constructions  with textolite and bronze rings and has long life period. Benefit of new seal is in easy change of seal cuffs when revision and repairs: for such operation one doesn’t need any special devices and qualified specialists.

Assembly are fully interchangeable on chocks and rolls with existing units of OFB, produced before by EZTM JSC. To change old seal units for new one, one should order:

-back cap with seal

-back nozzle

-oil-catch ring

When you order new seal, please note number of general drawing  OFB or back cap, to let us control interchangeability of caps.

NEW CONSTRUCTION OF BACK CAP SEAL FOR OFB OF BIG SIZE

Principle of present seal work is analogous to one which is in OFB construction, produced by companies Morgan Constraction; Schloemann Siemag, Davy Mckee: basic radial cuff  has 2 elements preventing leakage of oil from bearing and leak in of water , maze seal and butt end, preventing from getting inside water and scale.

Seal assembly of our construction has following difference:

-radial cuff is made from two symmetric parts that greatly simplifies its production and will let in future to different materials, corresponding to surrounding where it works: oil and water.

-radial cuff with the help of bolt nozzle is strongly fixed on bush pin, that excludes its expansion under centrifugal force and oil leakage on inner surface.

-butt cuff contacts not with roll surface but with inner surface of nozzle , that lets harden it, cover special coating, increasing long life.

-Maze seal protects not only radial cuff, but front butt cuff also, that exclude direct get of scale at working edge of butt cuff and highly increases long life.  

Cap surface which is in contact with radial cuffs is chromed.