Key points for equipment protection in the steel rolling production line under high-temperature conditions: Prevent overheating, reduce faults, and ensure stable production. A comprehensive guide for
Preface
During the summer high-temperature period, the steel rolling production line is constantly operating under heavy load, high temperature and high dust conditions. Coupled with the rising ambient temperature, the equipment's operating load has significantly increased: lubricating oil accelerates oxidation and fails prematurely, bearing temperatures exceed the standard, electrical components age more rapidly, and the risk of hydraulic system leakage rises. This is the peak period for equipment failures throughout the year.
Many workshops are accustomed to "repairing after problems occur". However, equipment failures under high temperatures are often sudden and highly interrelated. A single bearing burnout or a burst hydraulic pipeline can lead to the entire rolling line coming to a halt, resulting in losses far exceeding the cost of protection. The core of equipment protection in high-temperature conditions lies in "prevention" rather than "repair". By proactively identifying risks and strengthening targeted protection, it is possible to effectively reduce faults and ensure stable production.
Based on the on-site practical experience of hot rolling, cold rolling and tube rolling lines, this article systematically summarizes the key points of equipment protection under high-temperature conditions from five core dimensions: lubrication, bearings, electrical-hydraulic systems, cooling systems, and inspection and emergency response. All of these are practical on-site solutions that can be directly implemented.
1. Lubrication System: The High-Temperature Failure Hotspot, Selecting the Right Solution and Controlling Closely Are Key
Lubrication is the lifeblood of equipment. In high-temperature environments, the viscosity of grease decreases, oxidation accelerates, and the drop point is insufficient, which makes it extremely prone to lubrication failure. This is the primary cause that leads to faults in bearings, gears, and transmission components.
1. Oil selection: Suitable for high-temperature working conditions, eliminating the practice of using the same lubricant throughout the year. In high-temperature areas such as the main drive of the rolling mill, the roller conveyors, and the surrounding areas of the heating furnace, replace the lubricant with high-dripping-point and high-temperature-resistant special lubricants. Preferentially use composite lithium-based grease and polyurea-based grease, with the dripping point being higher than the maximum working temperature by more than 20℃ to prevent the lubricant from becoming thin and leaking at high temperatures.
The hydraulic system and gearbox will appropriately increase the viscosity grade of the lubricating oil based on the temperature rise situation. At the same time, they will select oil with stronger antioxidant and anti-thermal degradation properties to alleviate the problem of sudden viscosity drop and insufficient oil film strength under high temperatures.
The sealing parts and hoses in the high-temperature area should be inspected for compatibility. Ordinary nitrile rubber is prone to aging and leakage at high temperatures. The key parts should be replaced with fluorine rubber to prevent any leakage.
2. Control Measures: Perform frequent but small additions to prevent excessive lubrication
Abandon the misconception that "more grease leads to better wear resistance". Adding excessive lubricant at high temperatures will instead cause increased heat generation during mixing, accelerating the deterioration of the grease. Strictly follow the principle of "small amounts and frequent additions", shorten the filling cycle, and make appropriate and single additions to maintain the freshness of the grease.
In the summer, the lubrication system's pre-check and pressure/interval adjustment should be carried out in advance. The clogged distributors and oil passages should be cleaned to prevent local lack of lubrication and dry grinding. The manual addition points should be recorded in a ledger. At key workstations, checks should be conducted every shift and replenishment should be carried out at fixed points.
3. Oil quality monitoring: Replace when deteriorating
Conduct weekly inspections of the oil quality in the gearboxes and hydraulic stations. Observe changes in color, odor, and viscosity. If there is discoloration, sour smell, or an increase in impurities, take samples for testing immediately. If oxidation levels exceed the limit or the viscosity does not meet the standard, replace the oil promptly. Do not delay until the fixed oil replacement cycle arrives.
The fuel tanks and fuel stations should be provided with shading and heat insulation measures to prevent the fuel temperature from continuously rising due to direct sunlight exposure. In necessary cases, auxiliary cooling devices such as air cooling or water cooling should be installed for enhanced heat dissipation.
II. Bearing Components: Prevent overheating damage, guard against core faults
Roller mill bearings, conveyor belt bearings, and transmission bearings are the core components most prone to damage under high temperatures and are also the fault points causing the greatest downtime losses. High-temperature protection must be carried out meticulously and thoroughly.
Temperature rise monitoring: Pre-warning for excessive temperature
For the working rolls, support rolls, and main drive bearings of the key rolling machines, online temperature monitoring devices are installed. Warning thresholds are set, and abnormal temperatures will trigger early alarms. For points without online monitoring, the on-duty temperature measurement system is implemented. During high-temperature periods, the frequency of temperature measurements is increased, and at key points, measurements are conducted every 2 hours.
Pay attention to distinguish between "environmental temperature rise" and "faulty temperature rise": The uniform temperature increase caused by the overall rise in ambient temperature, with the temperature remaining stable and not continuously rising, can be alleviated by enhancing heat dissipation; if a single point temperature suddenly rises and continues to increase, accompanied by abnormal vibration, immediately stop the machine for inspection;严禁 operating with faults.
2. Clearance verification and assembly check: Compensation for thermal expansion
Under high temperatures, the thermal expansion of the inner ring and rolling elements of the bearing will cause the working clearance to decrease. If the clearance is not adequately reserved during assembly, it is highly likely to result in jamming or damage. During summer maintenance and bearing replacement, select C3 and C4 large clearance bearings based on the temperature rise of the working conditions to compensate for the clearance contraction caused by thermal expansion.
Check the heat dissipation conditions of the bearing housing, clean the accumulated dust and iron oxide on the surface to ensure the smoothness of the heat dissipation channels; for heavy-duty and high-temperature bearings, oil-gas lubrication and circulating oil lubrication can be adopted to enhance the heat dissipation and cooling effect.
3. Special Workstation Special Protection
At the near-fire workstations such as the exit conveyor belt of the heating furnace and the unloading conveyor belt, the bearings are constantly exposed to high-temperature radiation. To prevent heat radiation, heat insulation baffles and water-cooled sleeves are installed, which effectively isolate the heat and significantly reduce the working temperature of the bearings, thereby extending their service life.
Avoid allowing the cooling water to directly splash onto the bearing housing. A sudden change in temperature can cause an imbalance in the internal stress of the bearing, and it is also prone to allowing water vapor to enter and causing the lubricating oil to emulsify, which in turn accelerates the failure.
III. Electrical and Hydraulic Systems: Rapid aging at high temperatures, anti-short circuit, anti-leakage
Summer is the peak period for electrical tripping, component burning, and hydraulic pipeline burst. High temperatures accelerate insulation aging and sealant failure, with hidden dangers and high potential risks.
Electrical System: Cleaning + Cooling + Inspection in Three Steps
Comprehensively clean the cooling airways and surface dust of the electrical cabinets, frequency converters, and motors. Dust accumulation will seriously affect cooling, causing the component temperatures to soar. Check the operation status of the air conditioners and cooling fans in the high-voltage cabinets and frequency conversion rooms. Replace the filters in time to ensure that the cabinet temperatures are controlled within the rated range.
The focus is on inspecting the connection points of the terminal blocks and busbars. Under high temperatures, thermal expansion and contraction can cause bolts to loosen and the contact resistance to increase, thereby posing a risk of overheating and sparking. During the downtime, key connection points should be tightened, and infrared temperature measurement should be used to identify the hot spots.
Check the insulation performance of the motors and cables. In high-temperature and high-humidity environments, the insulation performance may decline, which could lead to short circuits or grounding faults. Ensure that outdoor motors and junction boxes are protected against rain and sunlight to prevent excessive temperature rise due to direct sunlight exposure.
2. Hydraulic System: Control oil temperature, inspect seals, and prevent explosion pipes
The oil temperature of the hydraulic station is strictly controlled. If it exceeds 55℃, forced cooling will be activated. Long-term overheating will accelerate the aging of sealing components and the oxidation of oil, leading to leakage and unstable pressure. Clean the scale and dirt in the cooler to ensure heat exchange efficiency. If the cooling water volume is insufficient, it should be promptly expanded.
Thoroughly inspect the high-pressure pipelines and rubber hoses. Under high temperatures, the rubber hoses age more rapidly. Regular pressure testing should be conducted at key areas. If bulges, cracks, or oil leakage occur, they should be replaced immediately to prevent pipeline bursts and equipment shutdown during production. At the same time, eliminate potential fire safety hazards.
Regular inspections of the sealing components of the hydraulic cylinder and valve group should be conducted. Any internal or external leakage should be dealt with promptly. The sealing performance deteriorates more rapidly at high temperatures. Small leaks that are not addressed in time may escalate into major failures.
IV. Cooling System: Self-check the heat dissipation core first. Don't wait until it fails before carrying out repairs.
Roller cooling, equipment water cooling, and turbinate water system are the core for cooling the production line in summer. Once the cooling capacity drops, the temperatures of rollers, bearings, and equipment will rise in a chain reaction, leading to concentrated failures.
Water pipeline network: Clean and maintain smooth flow
Comprehensively clean the cooling nozzles and water collection pipelines of the rolls, remove the blockages caused by scale and iron oxide, ensure that the flow and pressure of the cooling water meet the standards, and prevent uneven cooling at certain areas from causing abnormal hotness of the rolls, out-of-control plate shape, and damage to the roll surface.
Check the water quality of the turbid ring and the clean ring. If the suspended solids or oil pollution exceeds the standard, deal with it promptly to prevent the nozzles from being continuously clogged; maintain the filtration device and the oil removal device properly to ensure the stability of the cooling water quality.
2. Cooling Equipment: Efficiency Enhancement and Capacity Expansion
Comprehensive maintenance and inspection of cooling towers and heat exchangers are carried out. The water scale on the packing and the dust on the fan blades are cleaned. The operating conditions of the fans and pumps are checked to ensure that the heat exchange efficiency meets the standards. During peak high-temperature periods, backup cooling equipment can be activated to reduce the water supply temperature.
Recheck the key cooling points to verify the cooling water volume. Focus on the critical areas such as the rolls, bearing seats, and gearboxes. According to the temperature rise in summer, appropriately increase the cooling water volume to meet the heat dissipation requirements under high-temperature conditions.
3. Eliminate cooling dead zones
Identify and address areas with excessive heat in equipment, such as transmission gearboxes, main motors, and hydraulic stations. If the original cooling capacity is insufficient, temporary wind-cooling or water-cooling auxiliary measures can be added to eliminate the cooling dead zones.
Ensure that the cooling water pipeline is well insulated to prevent the water inlet temperature from rising due to high ambient temperature, thereby weakening the cooling effect.
V. Daily Inspection and Emergency Response: Eliminate Faults at the Incubation Stage
1. Special Inspection for High Temperature, Emphasizing Key Points
Develop a special inspection schedule for high temperature conditions in summer, clearly defining core items such as temperature measurement, vibration measurement, oil inspection, and cooling inspection. Increase the inspection frequency during high-temperature periods and focus on monitoring during the mid-shift and night shifts to prevent the expansion of faults due to lax night duty.
The inspection process involves the combination of "observation, touching, listening and measuring": Check for any leaks, smoke or color changes; Feel the temperature and vibration to see if they are abnormal; Listen to the running sound to see if there are any abnormal noises; Use temperature gauges and vibration meters for precise detection, and do not rely on experience for judgment.
2. Prepare spare parts in advance
For high-temperature-related failures, prepare high-temperature lubricating grease, seals, bearings, electrical vulnerable parts, high-pressure hoses, etc. as spare parts in advance. Store the key spare parts nearby to ensure quick replacement in case of a failure, thereby reducing the downtime.
Emergency tools and repair equipment should be inspected in advance to ensure they are in good condition. This is to enable a quick response in case of unexpected failures.
3. Peak Production and Load Management
During extreme high-temperature periods, the production schedule can be appropriately adjusted based on order requirements, avoiding full-load production during the peak temperature hours and reducing the equipment operating load. For those that cannot be managed through peak avoidance, mandatory cooling measures should be taken for key equipment, and forced production under excessive temperature and load conditions must be strictly prohibited.
Conclusion
The protection of equipment under high-temperature conditions is not a "special task for summer", but rather a meticulous management process that runs throughout daily operation and maintenance. Selecting the right lubricants, maintaining bearings properly, conducting detailed inspections of electrical systems, ensuring adequate cooling, and conducting thorough inspections - by implementing each of these basic tasks effectively, we can significantly reduce high-temperature failures and maintain the production line's stable operation.
In the current era where industries are competing in terms of efficiency and cost, every time there is a reduction in unplanned downtime and every day of stable production, it represents a tangible improvement in efficiency.
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