1. The exhaust temperature is 50 to stop the condensate pump, in fact, it is just an experience, it is a relatively safe experience, and all aspects are considered. If your power plant doesn't mind this, you can stop the condensate pump for 30 minutes.
2. The source of this 50 is: the condenser of the old unit in the past is used copper pipe, the cooling water is raw water, the copper pipe is not welded in the front and rear water chamber tube plate connection (is thermal expansion), the temperature is greater than 50, it is easy to make the copper pipe at the front and rear water chamber tube plate stretch out, the expansion mouth is loose, and the circulating water (raw water) will leak into the condensate water system to cause water pollution.
However, no matter whether the previous copper pipe or the current stainless steel pipe is expanded, it is either thermal expansion, or one end is stuck (inserted with a round bar with a large friction coefficient, artificially stuck), and the other end holds a semicircular drill bit (with frosted) to expand the stainless steel pipe; After the expansion of this end, the two people swapped positions and continued to expand on the other side. After the expansion of all pipe bundles is completed, the condenser is filled with water at a high level to check for leakage.
3. Furthermore, consider that the exhaust temperature of the low-pressure cylinder is too high, which will easily lead to the heated expansion of the exhaust cylinder, cause eccentric changes, cause dynamic and static friction, and may also cause the expansion difference to exceed the limit. In addition, after the unit is stopped, it is in a cranking state, and the condensate is recirculated, which is conducive to reducing the cylinder temperature! Otherwise, the temperature of the low-pressure cylinder of the steam turbine will rise, which will easily cause the cylinder and rotor to deform. ButSince they are ready to stop the condensate pump, they must have stopped and opened the brake long ago, and it must be in a cranking state. At this time, it is indeed alarmist to say that the expansion difference becomes larger and causes dynamic friction! However, there is a theoretical basis for the low-pressure cylinder foundation to be lifted, resulting in a smaller radial clearance. However, the exhaust temperature of 50 and 90, or even 120, has a very limited effect. However, it is best to control the exhaust temperature below 80.
4. In fact, as long as the circulating water is not interrupted, there will be no problem with the cooling pipe bundle. The most feared is the interruption of cooling water, and do not rush into the circulating water before the temperature of the exhaust cylinder is greater than 50. The temperature difference between the inside and outside of the tube bundle is large, and the thermal stress is large, which damages the tube bundle and even leaks.
5. The air-cooled unit does not involve the problem of condenser tube bundle leakage, but generally follows the provisions of 50 stop operation of the condensate pump, mainly to prevent the exhaust temperature from rising, and has also encountered that after the condensate pump is out of operation, the exhaust temperature rises to 110, and finally the condensate pump is started.
6. Say a thing that actually happened: the unit is operating normally, and the A feed pump is running, but the feed pump A thin oil station is defective. After switching to B feed pump operation, stop A feed pump, and the commissioning personnel require 1h to stop the thin oil station, and then eliminate the shortage. But 20 minutes later, the maintenance personnel asked for an invoice to be eliminated. Stop the thin oil station, the bearing temperature rises from 38 to 72, then stop the shortage, and start the thin oil station. After 1 h, the deficiency disappeared normally.
This example tells us: when the condensate is cooled, the exhaust temperature is 50, so stop the condensate pump, which may be 80, which is acceptable; If the condensate cools down and the exhaust temperature is 90, then stop the condensate pump, maybe 110, it is unacceptable, and the condensate pump has to be restarted, so why bother.