Issues with the drain outlet of the turbine exhaust safety valve
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Our condensing steam turbines are equipped with exhaust safety valves on the condensers; there are a total of 6 ports: for steam inlet, steam exhaust, water inlet, water drain, and two steam traps. One of these steam traps is located on the atmospheric side, while the other is on the vacuum side. According to the manufacturer’s specifications, the one on the vacuum side should be connected to a steam trap expansion tank, whereas the one on the atmospheric side should lead to the drain. What I would like to ask is: 1. Our vacuum side drain pipes are not connected to the steam trap expansion tank, but rather directly to the condenser. Since there are two condensate pumps, one in use and one as a backup, each with an exhaust port that leads back to the condenser, the construction team connected the exhaust ports of both pumps together and led them to the condenser. As a result, there is one remaining interface on the condenser, and the vacuum side drain from the safety valve is connected to this remaining interface. Is there a problem? Personally, I don’t think it’s a big issue. 2. Should the drain valve on the atmospheric side of the exhaust safety valve always be left slightly open, so that water droplets can flow out? It shouldn’t be closed completely; we closed it.
The drain port on the atmospheric side of the exhaust safety valve should remain open at all times; in other words, a small amount of water must flow out to serve as a water seal. It should not be closed, as doing so could cause water to leak out from the exhaust port.
Generally, the exhaust at the inlet of the condensate pump is connected to a pipe. As you yourself have said, connecting it directly to the condenser isn’t a big problem; it’s better to connect it to the middle or upper part of the condenser. Connecting it to the water transfer expansion tank (referred to as a flash tank in units with an inlet) serves the purpose of separating the gas and liquid phases before they enter the condenser. As long as the vacuum level is fine, that’s okay. Regarding your second question, the return flow should be fully open, but the volume shouldn’t be too large nor too small – generally, it should be around one-third to one-half of the diameter of the DN20 pipe. This is just my personal opinion for reference only
The guy upstairs covered it all very well, haha
Reply to 3# lizhenpeng: We have 2 steam turbines. One of them has the condenser equipped with 2 ports reserved for the exhaust air from the condensate pumps, while the other one has 1 such port. Actually, it doesn’t matter whether there is 1 or 2 ports; I just noticed that there was an empty spot on the drain expansion tank and wanted to find out why, so I checked the drawings and found that the connection was incorrect. Hehe
I would like to ask if it is the safety valve used for evacuating inert gases from the turbine