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Lubrication characteristics of iron and steel metallurgical machinery (middle)

Lubrication characteristics of iron and steel metallurgical machinery (middle)

2020-05-01

(3) lubricating system of rolling steel oil film bearing: the lubricating system of rolling steel oil film bearing has dynamic pressure system, static pressure system and static pressure mixing system.The liquid friction condition of dynamic pressure bearing can be formed only when the roller rotates at a certain speed.When rolling mill start, brake or reverse, its speed change can not guarantee the condition of liquid friction, limit the use range of dynamic bearing.The static pressure bearing makes the journal float in the bearing by the static pressure, the formation of the high-pressure oil film is independent of the speed, when starting, braking, reversing or even static, can guarantee the liquid friction conditions, the bearing capacity is large, the rigidity is good, can meet any load, speed requirements, but need special high pressure system, the cost is high.Therefore, when starting, braking, reversing, low speed with static pressure system for high pressure oil.When the static pressure system is closed at high speed, the static pressure mixing system with dynamic pressure system for oil supply is more ideal.

(4) rolling oil mist lubrication and oil and gas lubrication system: oil mist lubrication with compressed air as the power to make the oil atomization, through the pipeline, condensing nozzle into the lubrication part.For gear, worm gear, especially for large, high speed, heavy load rolling bearing lubrication.It has high lubrication and cooling efficiency;And can save oil;Because the oil mist has a certain pressure (2-3kpa) and can prevent impurities and water immersed in the friction pair, so that the bearing life increased by 40%.Oil mist lubrication system includes water filter, solenoid valve, pressure regulating valve, oil mist generator, conveying pipe, condensing nozzle, control testing instrument, etc.Oil mist generator is the core device.Oil and gas lubrication is better than oil mist lubrication, it is the compressed air flow along the pipeline oil to the lubrication point.The key component of the oil and gas lubrication system is the oil and gas mixer and the oil and gas distributor.

4. Common lubricating device for rolling mill

The commonly used lubricating devices for heavy machinery (including rolling mill and its auxiliary machinery equipment) include dry oil, thin oil and oil mist lubricating devices.Domestic lubricating machinery and equipment can be basically supplied in a complete set.Introduced here is one of the main lubrication devices, its name, the performance is as follows: heavy machinery standard thin oil lubrication device (JB/ZQ4586-86) of this standard is applicable to metallurgy, heavy duty, mining and other mechanical equipment, thin oil circulating lubrication system in thin oil lubrication device, working medium viscosity grade for N22 - N460 industrial lubricants, circulating cooling device adopts column tube cooler.Nominal pressure of thin oil lubricating device is 0.63mpa;Low filtration accuracy and viscosity is 0.08mm;High viscosity is 0.12mm;Industrial water with cooling water temperature less than or equal to 30℃;Cooling water pressure is less than 0.4mpa;When the inlet temperature of the cooler is 50℃, the temperature drop of the lubricating oil is greater than or equal to 8℃.The steam pressure is 0.2-0.4MPa.The pressure ranges of the above main lubricating elements are 10MPa, 20MPa and 40MPa, among which 20MPa and 40MPa are foreign imported technology products produced by taiyuan lubricating equipment factory and Shanghai lubricating equipment factory.Other products, in addition to the above two, there are shenyang lubrication equipment factory and xi 'an lubrication equipment factory production.Thin oil system, components four production.

5. Installation and maintenance of common lubricating equipment of rolling mill

(1) installation of equipment: carefully review the piping layout drawings of lubricating device, lubricating device and mechanical equipment, review the drawings of foundation, confirm the connection and installation relationship is correct, then proceed with installation.Check the device and component before installation;The product must be certified, the necessary devices and components checked and cleaned, and then pre-installed (for more complex systems).Clean the pipeline after pre-installation;Inspect components and joints, and replace with qualified, clean parts in case of loss or damage.Cleaning method: degrease with carbon tetrachloride;Or after degreasing with sodium hydroxide, wash with warm water.Then use hydrochloric acid (mass fraction)10-15%, ulotropin (mass fraction)1%, dip or wash for 20-30min, the solution temperature is 40-50℃, and then wash with warm water.Then soak and clean the ammonia solution with the mass fraction of 1% for 10-15min. After the solution temperature is neutralized at 30-40℃, rinse with steam or warm water.Finally, dry with clean dry air, coated with anti-rust oil, to be formally installed.

(2) cleaning, pressure testing and debugging of the equipment: after the formal installation of the equipment, it is better to clean the cycle again to ensure reliability.The circulation time of dry oil and thin oil system is 8-12 hours, and the pressure of thin oil is 5-3mpa.Cleanliness is ybj84.8g, H(similar to NAS11, 12).After cleaning, the system should be tested at rated pressure holding for 10-15min.Gradually increase the pressure, timely observe and deal with the problem.After the test, according to the design instructions read the pressure relay, temperature regulation, liquid level regulation and interlock switch to adjust, then can be put into use.

(3) equipment maintenance: site users must make efforts to understand the equipment, devices, component drawings, instructions and other data, from the technical grasp of the use, maintenance and repair of the relevant data, in order to use maintenance and repair.Common accidents and treatment in lean oil stations and dry oil stations: a. bearing heating of lean oil pump (slider pump) : the cause is that the bearing clearance is too small and the lubricating oil is insufficient.B. The pressure of oil station increases suddenly: the pipeline is blocked and blocked. Check the pipeline and take out the plug.C. The thin oil pump is hot (slider pump) : if the clearance of the pump is improper, adjust the clearance of the pump;Oil viscosity is too large, reasonable choice of oil;Improper pressure regulation, more than the actual pressure, reasonable adjustment of the system pressure;Oil pump joints leakage caused by volume loss and heat, tighten the joints, and check the seal to prevent leakage.E. Dry oil station bearing heating: small clearance of rolling bearing;The shaft sleeve is too tight, the worm gear contact is not good, adjust the bearing clearance, repair the shaft sleeve, grind and close the worm gear.F. Hydraulic reversing valve (ring type) returns oil, the pressure gauge does not work: the oil line is blocked, disassemble the valve to clean, check, make the oil line unblocked.G. Pressure operated valve push rod operates at very low pressure: check valve is abnormal, check spring and steel ball, and clean, repair or replace.H. Dry oil station pressure gauge can not hold the pressure: the safety valve is broken, the piston of the oil feeder is not well matched, the piston of the reversing valve is not well matched, the piston gap of the oil pump is too large, repair the safety valve, replace the bad oil feeder, exhaust the air;Replace plunger and grind plunger clearance.I. Joint and welding oil leakage: the reason is that the flange end face is uneven, there is no pad at the joint, the pipe is short when connected, welding mouth and sand hole, remove the repair flange end face, put the pad bolts, put an extra pad and lock, remove the pipe and reweld.Oil mist lubrication system failure analysis: oil mist pressure drop: the air supply pressure is too low, check the air source pressure, readjust the pressure reducing valve;Excessive water is accumulated in the water separation filter and the pipeline is not unblocked. Drain water, clean or replace the air filter;Oil mist generator blocked, remove valve body, clean and purge;Oil mist pipe leak, repair.Oil mist pressure rise: the air supply pressure is too high, adjust the air pressure reducing valve;If the pipeline has u-bend, or the slope is too small, condensate oil can block the pipeline, eliminate u-bend, increase the pipeline slope or install drain valve;Pipe is not clean, condensing nozzle is blocked, check and clean.Oil mist pressure is normal, but atomization is not good, or blowing pure air, the oil level does not drop: add wrong lubricating oil, viscosity is too high, oil change;If the oil temperature is too low, check the temperature regulator and electric heater for proper operation;Oil suction filter blocked, clean or replace;Plug the nozzle, remove the nozzle, clean and check;Low oil level, replenish to normal oil level;Oil gauge needle valve open too large, close or completely close the oil gauge needle valve;Air needle valve open too large, compressed air directly to the pipeline, adjust the air needle valve.The lubricating oil film bearings of rolling mill oil film bearings belong to a family of sliding bearings and are in a state of full fluid lubrication under working conditions.Oil film bearing is based on the principle of fluid dynamic pressure lubrication, that is, depending on the relative motion of the shaft and bearing elements, with the help of the viscosity of lubricating oil and the action of fluid dynamic pressure formed by the wedge clearance of oil in the bearing pair, the bearing bearing oil film is formed.As bearing oil film and oil film pressure, rise to balance load, isolation, shaft and shaft sleeve, solid friction between the metal into the inside of the liquid molecular friction, reducing friction and wear to a minimum, and thus can satisfy the bearing pressure at maximum range, impact resistance, change speed and the precision of rolling and the service life of the structure size and requirements.According to the design of Reynolds equation, the rolling pressure, rolling speed, bearing clearance and lubricating oil viscosity are matched to form an uninterrupted stable bearing oil film, so as to achieve liquid dynamic pressure lubrication, so as to satisfy the friction and lubrication of the rolling mill in different operating states.That is, the lubrication of semi-dry friction and edging friction when starting, stopping, turning forward and reversing, the lubrication of mixed friction in impact load or a lot of water, the liquid friction and lubrication when normal operation and full load, continuous operation.

Therefore, oil film bearing lubrication, often in the following three forms:

(1) when starting or stopping, although there is lubricating oil between the shaft and the bearing, the hydrodynamic lubrication has not yet formed or gradually disappeared due to the movement speed is equal to zero or close to zero, the shaft and the bearing must be in direct contact, at this time in the state of edge medium lubrication or even semi-dry friction.

(2) in the operation of rolling mill, mixed lubrication may be produced due to vibration, excessive water intake, insufficient oil supply or problems with oil quality.

(3) when the rolling mill runs normally and smoothly, it presents fluid lubrication.Therefore, the lubrication characteristics of oil film bearings are the above three cases of alternating mixed lubrication.In order to meet the needs of high speed, heavy load, automation, large scale and high output of iron and steel enterprises, solve the lubrication requirements of rolling mill oil film bearings, and meet the increasingly demanding working conditions, the lubricating oil used in rolling mill oil film bearings -- oil film bearing oil came into being.

Performance requirements of oil film bearing oil

The lubrication characteristics of the rolling mill oil film bearing determine that the oil film bearing oil must meet its performance requirements in order to ensure the normal operation and continuous production of the rolling mill. Therefore, the oil film bearing oil shall be:

(1) excellent viscosity-temperature performance (high viscosity index), when the bearing temperature changes greatly, can still achieve the normal lubrication of all lubrication parts.

(2) excellent anti-emulsification performance (namely water), in the long-term use can quickly separate the water in the oil.

(3) good wear resistance and extreme pressure performance, operation oil mixed with a small amount of water, can still form an oil film to maintain heavy load and wear resistance.

(4) good anti-wear, anti-rust, anti-foam performance, prevent the lubrication system from corrosion, blocking the oil path, resulting in wear and lack of oil supply.

(5) good oxidation stability, cleaning and filtering.Smooth the oil path of the lubrication system to ensure normal lubrication.


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