Does changing the gearbox from high-speed drive to low-speed drive have an impact on its vibration?
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Background: The four-unit catalytic unit consists of a flue gas turbine, a fan, a steam turbine, a gearbox, and a motor. A failure occurred in the steam turbine, causing the quick-shut valve to close; as a result, the unit’s power consumption shifted from 1000 to 2600 units instantly. At this point, the vibration at the low-speed end of the gearbox (the motor) increased sharply from below 10 to 90. Meanwhile, there is no significant increase in vibration at the high-speed end of the gearbox nor in shaft displacement at the gearbox
What is the unit behind the figure indicating that \"the unit’s power consumption suddenly changed from -1000 in power generation mode to 2600 in power consumption mode\"? Thank you!
Is your main fan driven by both a turbine and an electric motor? After the turbine stops operating, the power consumption of the motor increases from 1000 to 2600. The high-speed shaft is connected to the turbine, while the low-speed shaft is connected to the motor. After the turbine stops operating, the motor and the exhaust fan take over to drive the main fan. The load on the motor increases, and the low-speed shaft becomes the driving shaft. Has there been any change in its speed, or in the temperature of the low-speed shaft? Is the coupling between the motor and the low-speed shaft properly aligned? Are there any records from previous maintenance regarding the clearance of the bearing shells? It’s also necessary to check whether the radial alignment curve in the horizontal direction changes when the low-speed shaft takes over driving the fan. Please, any passerby who knows something about this, could you analyze and discuss it?
It changes from 1000 in power generation to 2600 in power consumption, which means a change of 3600 in power
You’re right; it’s the smoke extractor and turbine that drive the main fan, with an extra 1000 watts of power used to generate electricity for the motor； At the moment the turbine is disconnected from the grid, it is replaced by a smoke extractor and a motor driving the main fan. The rotation speed remains unchanged; in other words, the gearbox originally had the high-speed shaft driving the low-speed shaft, but now it is the low-speed shaft that drives the high-speed shaft
Can it be understood that the turbine drives the motor to produce 1000 units of work, yet now the motor has to consume 2600 units of energy to drive the turbine and the fan? It turns out that driving a low-speed shaft with a high-speed shaft is less labor-intensive, as the radial load on the bearings is smaller; whereas driving another low-speed shaft with a low-speed shaft is more labor-intensive, resulting in a greater radial load on the bearings and a thinner lubricating oil film, which causes friction with the bearing surfaces. It might be possible to increase the oil pressure in the areas where vibration occurs. If that works, the turbine’s quick-shut valve can be opened, and the opening degree of the control valves can be reduced to lower the load on the motor.