On the operating and design parameters of condensate water pipes
Thread Content
This post was last edited by kele135 on 2020-8-20 at 21:52. I am currently working on pipeline data tables, and I have many questions regarding the operating parameters of the steam condensate pipelines behind steam traps; I hope fellow users can help answer them! 1. I used to think that steam and condensed water were only related by phase change; for example, saturated steam at 7 bar and 170°C would turn into saturated condensed liquid at 7 bar and 170°C after passing through a steam trap. This idea is wrong, right? If the back pressure behind the steam trap is 2 bar, then there should be saturated condensate at around 2 bar and 133°C behind the valve, right? 2. Building on the previous point, if the back pressure behind the steam trap is 2 bar, then the operating pressure of this condensate pipe will be 2 bar, with an operating temperature of 133°C. The pipeline data sheet also requires the maximum operating temperature and maximum operating pressure to be filled in. Do these values refer to the operating parameters of the steam before the water supply valve, namely 7 bar and 170°C? Should I just add a margin to the working parameters directly? 3. Determination of the pressure pipeline category: According to the latest definition of pressure pipelines, since the operating temperature is higher than the standard boiling point of water, then the condensate pipeline with a pressure of 2 bar and a temperature of 133°C falls under the category of pressure pipelines, right? Since the GC3 grade has been removed, is it appropriate to classify the aforementioned pipeline as GC2 grade? 4. Going a step further: The pressure in the condensate pipeline gradually decreases due to resistance. Assuming good insulation and constant operating temperature, if the pressure drops to 1 bar, is it necessary to consider the pressure increase caused by the flashing of the condensate? Does the maximum operating pressure need to take into account flashing?
1. The temperature behind the valve depends on factors such as whether the steam trap is under-cooled, how well the pipes are insulated, and the back pressure; it isn’t necessarily saturated – a two-phase state is also possible. Of course, as a value for the pipeline specifications, 2 barg at 133°C is acceptable. 2. You can also use 7 barg at 170°C. 3. Pipes with a diameter of DN50 or larger are considered pressure pipes, classified as GC2. 4. Flashing does not cause an increase in pressure; this is a misconception. Finally, please don’t ask too many questions at once – the experts here have little time and no patience to deal with that
Thank you, the answer was very clear and straightforward...
Pay attention to the pressure in the condensate recovery tank; it affects the pressure behind the check valve. For example, with the same pressure before the valve but different operating pressures of the recovery tank, the pressure after the valve will be different. The condensate flashes after the valve, and the outlet temperature is essentially the same as the temperature before the valve. The operating pressure before the valve depends on the pressure at the steam inlet. If there is no control valve at the steam inlet, then it is the main steam pressure ； If there is a control valve, it is the pressure behind the control valve. Many factors need to be considered when selecting a strainer.