The following thesis discusses the upgrade project of the lubrication system of the hot leveller machine, designed for levelling steel plates in steel industry. Nine main rolls are driven by three electric motors. Mechanical power transmission is implemented through the reductor and pinion stands due to the desired speed and the required torque. Continuous lubrication is required to obtain efficient, smooth and long-lasting operation of mechanical parts. The used lubricating medium is the oil which circulates through the lubrication system of the hot leveller machine. Lubrication is carried out by spraying nozzles, which are focused on gears within the gearbox.
I have discovered that the result of oil flow through the lubrication system was too high. Consequently, the safety valve was passing some oil directly back to the oil tank due to excessive pressure. This part of the oil flow has not carried out work that was useful and resulted in net loss. At that point I reduced the oil flow while using a variable frequency drive to control the rotational speed of the pump's induction motor. By reducing the frequency I consequently reduced the pump speed and hence the flow of oil which caused loss in the lubrication system.
Furthermore, I implemented two operational modes of lubrication system. During the rolling of a plate, the system maintains a normal lubrication. However, when the rolling is completed and the hot leveller is waiting for the plate to roll, the lubrication is switched to saving mode. The program was written in the Proficy Machine Edition programming tool and loaded on a Fanuc programmable logic controller (PLC). PLC detects the possible presence of a plate near the hot leveller and triggers the command to start the lubrication system in normal mode. Various settings and current states of the system are displayed on the user interface – SCADA.
In conclusion the solution resulted in the reduction of power consumption and other maintenance costs of the lubricating system of hot leveller. The system has become more efficient and more economical due to lower power consumption.
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