Abstract: The characteristics, installation, operation and maintenance of oil-gas lubrication system of work roll bearing in Bensteel cold rolling mill are introduced, and the solutions to common faults in operation are put forward.

Key words: cold rolling mill; Work roll bearing; Oil-gas lubrication

Benxi steel CDCM unit is the introduction of domestic first pickling abrasion mill unit, with the international advanced level ‚ mill of 1 # ~ 4 # of work roll bearing (four row tapered roller bearing) adopted the REBS lubrication technology of oil and gas of the company. Rolling mill work roll bearing is a series of bearings, there are a number of friction pairs, the seal at the roll neck also needs lubrication, so the lubricating oil can be quickly permeated into each friction pair at the same time, also consider to provide bearing and roll neck seal with different amounts of lubrication; In addition, because the bearing seat is washed by the emulsion, the emulsion will inevitably invade the bearing seat and harm the bearing. REBS TURBOLUB oil and gas lubrication system can successfully solve the above lubrication problems of tandem bearings. This paper discusses the characteristics of oil-gas lubrication system and the problems that should be paid attention to in operation and maintenance.

1. Characteristics of oil-gas lubrication system design

1.1 Working principle of oil-gas lubrication technology

The continuous action of compressed air is used to drive the lubricating oil to flow continuously along the inner wall of the pipeline and form a turbulent oil and gas mixture, which is sent to the lubrication point in the way of fine oil droplets. This process is oil and gas lubrication. The compressed air is continuously supplied, and the oil is intermittently supplied. The intermittently time and oil supply can be adjusted according to the consumption of each lubricating point.

Oil and gas lubrication system is a comprehensive equipment integrating machinery, electricity and gas. The main equipment is:

(1) Fuel supply part: tank volume 500L; There are two oil supply air pumps (one for use and one for backup). The displacement of air pump is 6ml per stroke, and the normal working pressure is about 6MPa.

(2) Compressed air part: compressed air through the filter, solenoid valve, pressure reducing valve set pressure of 0.3 ~ 0.4MPa, it in the oil and gas mixing block and lubricating oil to achieve turbulent flow, compressed air pressure shall not be less than 0.2MPa.

(3) Distribution and mixing of lubricating oil: there is a progressive distributor at the outlet of the air pump, and the lubricating oil is precisely distributed into the downstream 4 groups of oil and gas mixing block after the progressive distributor, here mixed with compressed air into oil flow, oil and gas flow through the pipeline to each lubrication point.

(4) TURBOLUB sleeve modular oil and gas distributor: installed in the working roll bearing seat, the oil air is distributed to the bearing and seal parts by TUR-BOLUB oil and gas distributor in the required amount.

(5) Pipeline: the stainless steel pipe with an outer diameter of 10mm is connected to the lubrication point at both ends of the work roll bearing seat, and the pipeline layout has no effect on the transmission of oil and gas.

(6) Electronic control and monitoring device: the system is equipped with a lot of electrical monitoring equipment, to detect the flow, pressure, air pump working time, stop time and display components and system failures.

1.2 Advantages of oil-gas lubrication technology

(1) The gas-liquid two-phase oil film of oil and gas lubrication greatly improves the bearing capacity of the oil film, reduces the friction loss, improves the lubrication efficiency and the service life of the bearing.

(2) The oil and gas is continuously supplied to the bearing seat. The gas-liquid two-phase oil film generated by the oil and gas is fresh, and the bearing performance is not damaged.

(3) The compressed air passes into the bearing seat and spills out from the bearing seat, which can take away a lot of heat and effectively reduce the temperature of the bearing; At the same time, it also enhances the sealing performance of the bearing seat. The compressed air can keep the positive pressure of 30 ~ 80kPa in the bearing seat, so that the external emulsion and other dirt can not invade the bearing seat and harm the bearing.

(4) Accurate oil supply, avoid excess lubricating oil filling the bearing cavity, that is, reduce the viscous resistance, reduce the consumption of lubricating oil, will not pollute the emulsion, rolling mill and the surrounding environment like dry oil lubrication.

(5) There is no limit to the size of the lubricated equipment, the pipeline is simple and the pipeline layout is not restricted by the direction.

(6) The system has fewer moving parts, reliable operation and small maintenance, greatly reducing the operation and maintenance costs of lubricating equipment.

(7) Perfect monitoring means, high degree of mechanical and electrical integration, avoid bearing without lubrication operation, easy maintenance.

1.3 Setting system Parameters

(1) Lubrication quantity calculation formula of each bearing

By calculating the oil feeding cycle, Tp=110s was obtained. After operation and observation for a period of time, Tp= 80s could meet the requirements of equipment lubrication.

2 Installation, operation and maintenance Points

When installing and using the oil-gas lubrication system in Bensteel cold rolling mill, it draws lessons from the practical application experience of other mills and takes many improvement measures to ensure the normal operation of the oil-gas lubrication system. The brief summary is as follows:

(1) The quality of compressed air is particularly important for the stable operation of the oil-gas lubrication system. The compressed air is too dirty, and pollutants are easy to block the oil-gas distributor, which brings great harm to the system. As a result, a secondary filter with automatic blowdown was added to the installation. The filter AFF22B-10(3μm) and the oil mist separator AAM550-10(0∙3μm) were passed through with filter blocking indicators to determine the extent of filter blocking and the timing of filter replacement. Through the filtration of the two stages of the filter, the dust, water and oil in the compressed air are basically removed, the filtering effect is very ideal, and the failure caused by the dirty compressed air has not occurred.

(2) Improve the pressure and flow of compressed air. Compressed air is a natural coolant, because the compressed air can maintain a certain positive pressure in the bearing seat, and there is a large pressure difference between the positive pressure in the bearing seat and the compressed air pressure fed into the bearing seat, the larger the pressure difference can continue to cool the bearing, the greater the flow of compressed air, the better the cooling effect. Therefore, by adjusting the reducing valve of the system, the compressed air pressure is increased to 40KPa; The diameter of the compressed air pipeline is increased to improve the compressed air flow and pressure difference, so as to enhance the cooling effect of the bearing.

(3) Stainless steel pipes are used for oil and gas pipelines, which can reduce the workload of overhaul and maintenance and avoid the occurrence of box burning faults. Because the oil and gas pipeline in the rolling mill stand area is in contact with the emulsion steam for a long time, if the carbon steel pipe is used, the pipeline will be corroded and damaged for a long time, resulting in leakage, so that the lubricating oil reached the lubrication point is insufficient, resulting in the burning of the box.

(4) Since the increase in production yield = (annual output increased by 300,000 t) and the rolling speed also increased accordingly, the air pump was fed once in 60s instead of once in 80s according to the actual needs, so as to increase the lubricating oil amount to the bearings and improve the cooling effect accordingly.

(5) All seals should be selected and the selected oil compatible material, generally preferred fluorinated rubber or nitrile rubber.

(6) To maintain the cleanliness of the quick joint at the bearing seat, no dirt can enter, otherwise the dirt will make the quick joint inserted not in place, the oil circuit is blocked or the opening is too small, resulting in insufficient oil into the bearing and resulting in the burning of the box. In addition, the dirt will block the filter screen in the bearing seat so that the amount of oil into the bearing is not enough and lead to the burning box.

(7) Strengthen the assembly quality of bearing seat, avoid due to poor assembly of bearing seat or stolen goods into, resulting in oil and gas lubrication is not smooth or insufficient oil and lead to the burning of the box.

(8) to strengthen the daily point inspection, daily check normal air pressure, hydraulic system, flexible ‚ distributor action whether each connected all the way the transparent plastic tube of the mixture of oil and gas blocks for oil and gas, and whether the formation of vortex flow and turbulent flow state. If the flow of oil and gas is too fast, without forming a vortex of oil flow, it means that the pipeline is too long, the pressure loss is large, and the lubrication effect is not good. If the flow rate of oil and gas is too slow, it indicates that the system may be blocked, causing the oil circuit is not smooth. At this time, we should pay attention to check whether the oil and gas distributor, quick joint, bearing seat filter and air filter are polluted and blocked, and whether the quick joint is inserted in place.

(9) Check whether there is leakage in the system pipeline during scheduled repair (after the quick connector at the bearing seat is disconnected, if there is oil and gas flow in the transparent plastic pipe connected to the oil and gas mixing block, it indicates that there is leakage in the pipeline), whether the joint is deformed, and whether the rubber hose is worn. Contaminated quick joints need to be cleaned in time, and damaged hose, joints and pipes need to be replaced in time.

(10) If it is shut down for maintenance for a long time (annual repair, overhaul, etc.), the compressed air source should be closed so that the pneumatic pump can not output lubricating oil (above 6MPa), so as to prevent the failure of lubricating oil backfilling into the compressed air pipeline caused by the closure of the pipeline outlet (quick plug).

3 Closing remarks

In order to ensure the stable operation of the oil-gas lubrication system, the system has been improved from the aspects of design, manufacturing, installation, maintenance and so on. After the improvement, the oil-gas lubrication system is basically in the "zero fault" operation state. Oil and gas lubricating system put into use after ‚ improved the lubrication of work roll bearing state, statistics show that the modified lubrication system of oil and gas fuel consumption is 1/10 of the grease lubrication in fuel consumption, basically eliminated the loss caused by poor lubrication bearing, casing deformation and roll neck adhesion failure, achieved good economic benefits.

References:

[1] Shanghai Leibers Lubrication Technology Co., LTD. REBS Oil and Gas Lubrication System User Manual [M].

[2] Run Tonghai, HE Lidong · Gas-Liquid Two-Phase Fluid Cooling and Lubrication Technology and Its Application [M]· Harbin: Harbin University Press, 1995.