(Urgent) Increased bearing temperatures at high and low pressure sides after starting the MAN turbine
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For the turbine in the MAN engine set, during a normal shutdown, the operating temperature of the bearings was above 50 degrees. After restarting this time, the temperatures of the bearings at both the high-pressure and low-pressure ends increased by more than 20 degrees. What could be causing this? I checked the displacement and vibration levels; there were no significant changes, and the oil temperature was also normal. What other factors could be considered to determine the cause? ? ?
Has it been over 20 degrees all along, or just since it was turned on? It is possible that the oil temperature is not high enough, which affects the formation of the oil film.
It’s more than 20 degrees higher than the temperature before driving; it used to be in the 50s, but now it’s in the 70s, while the oil temperature remains the same as before!
What size is the unit? Under normal operation, ours is around 80°C. What is your oil supply temperature? You can check the axis trajectory/axis center line to see if it’s normal What is the steam inlet temperature?
First, check the instruments – examine both the on-site instruments and those that transmit data remotely. After ruling out instrument issues, we are now looking for problems with the equipment to see if there is an obstruction in the oil circuit.
The oil supply pressure and return flow rate can be checked, as well as a oil sample analysis. Compare temperature trends with vibration and shaft displacement; for periods of over 10 days, even the slightest correlation should not be overlooked.
The temperature hasn’t gone up yet, has it? Did you touch the dashboard after parking? Generally, the temperature changes a bit after each stop, but not by as much as you mentioned. It’s quite rare for all the temperature readings to increase like in your case. If the oil temperature and pressure are normal, then it’s sufficient to just check the gauge.
I have compared everything you mentioned with the data monitored on the SCADA system, and no significant changes were observed; only these two temperature points changed. It seems that this is not related to the instruments. Let me tell you something: there was a time when, during the parking period and while the turbine was being rotated, the vibration levels at these two points increased. When the rotation speed was 80, those vibration levels reached 40–50; afterwards, they gradually decreased to lower values. Then we started the turbine to operate again, and it was after that that the vibration levels at these two temperature points rose again. I don’t know if there’s any contact
I’ll talk about the crash that happened last time; I still haven’t figured out why it occurred. When the external power supply was lost, the entire plant shut down, but the rotor turning mechanism did not start automatically. After about 20 minutes, the rotor turning mechanism finally started operating; the rotor’s vibration level continued to increase, reaching around 50–60 um. The rotor turning mechanism stopped again, and then started once more. The vibration levels of these two bearings were around 40 um. After that, the rotor turning mechanism remained active, and the vibration levels gradually decreased, until they reached the normal level of about 6 um. However, this time after starting the machine, the temperatures of these two bearings remained at around 50 degrees, which is the normal level. It was not until the machine was stopped again and started once more that the bearing temperatures of the high-pressure and low-pressure cylinders of the turbine rose to 70 degrees, which is significantly higher, but the machine continued to operate stably. If it’s stable, then there’s definitely no problem, but I don’t understand how it reached that level – could there be an issue with the tiles?
The temperature of the bearing shells is also closely related to factors such as the load and speed of the unit; when testing the machine alone, with a low amount of steam supplied, the rotor temperature is likely to remain low, which in turn affects the temperature of the bearing shells； I don’t know what the parameters of the turbine are approximately, nor whether the operating conditions during the two runs were the same. Problem of high vibration during rotor turning: It is not clear whether the rotor turning mechanism in this unit is of the impact-type ratchet type or relies on a separate rotor turning motor for continuous rotation. Additionally, some large steam turbine rotors are very heavy; high-pressure oil is required to lift the rotor when starting it to turn. Moreover, when these rotors are turned at low speeds, impacts can occur in the gearbox, resulting in high vibration and fluctuations. If it is started again, the vibration values remain essentially unchanged at the same speed; I believe there should be no problems with the rotor system. Vawen 70 should be considered in the good category. 50 is relatively low; could this be due to the unit not being under load or having a low rotational speed?