Issues regarding vacuum breakdown during turbine shutdown
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To break the vacuum in our parking area, do we open the start air valve of the vacuum pump? I just can’t figure out why Could the expert explain it?
I’m not quite sure which valve you’re referring to. Could it be the valve that is being evacuated in the standby evacuator (or startup evacuator)? If so, due to the negative pressure inside the surface cooler, air is drawn back through the vent pipe (via that valve) back into the surface cooler, thereby breaking the negative pressure
It’s the valve that controls the exhaust pump; if it is opened, air will enter, which will break the vacuum. But with cold air entering, won’t that increase the temperature difference up and down on the turbine shaft, causing the shaft to bend?
The temperature will drop regardless of whether cold air is introduced or not; the method to prevent shaft deformation is to turn the shaft manually
Then what’s the purpose of that damn vacuum?
To bring the turbine to a stop quickly, an important parameter during turbine testing is the coasting time – the time it takes for the rotor to stop naturally without the vacuum being broken; this is usually the longest period of time involved
In normal production, when an interlock causes the unit to shut down, even though the rotation has stopped, it is still necessary to break the vacuum first. Our supervisor says this is to prevent cold air from entering suddenly and causing the rotor to bend; only after the vacuum is broken can the rotor be rotated
After parking, breaking the vacuum is a standard procedure; if higher standards are applied, steam is used to break the vacuum, mainly to prevent air from entering the surface cooler and causing corrosion, although this is generally not done to such an extreme extent.
Looking at your address, you’re in Huainan; could it be Huaihua? Which device is it, 902?
We are quite straightforward here; we require the vacuum system to be shut down half an hour after the turbine is stopped. It’s not broken; it’s just that the injector steam, sealing steam, and vacuum pump have been turned off
We basically start dealing with vacuum breakdown right after finishing the dry gas sealing