Condensate Lines

[NPC5]

I have a question about line list conditions for condensate lines. Say that there is a 50# saturated steam line, and steam trap, and then a condensate line that is feeding into an open sewer. I have seen two types of conditions listed for the condensate line. One way shows the condensate line with normal operating conditions of 0 psig at 212 F. The other method uses the normal operating conditions of the saturated steam line, 50 psig at 298 F. Which of these conditions would be the correct ones to use? Thanks for the help!

 

[TD2K]

Assuming the condensate line is sized properly such that the line losses are minimal, the pressure downstream of the steam trap is essentially atmospheric so the condensate will be a two phase mixture at 0 psig and 212F. If the atmospheric portion of the line is long then I might allow 10 psi or so as the operating pressure along with the saturated steam temperature.

The pressure is really immaterial since both lines will be class 150 piping (at least in my field, we never use anything less than class 150 for condensate). The only difference between using 212F and 298F is the amount of flexibility allowed in the piping design. It's not an issue if the trap discharges obviously into a hub but if you run a few hundred feet, it can affect how much growth is allowed.

 

[rmw]

Depends on the type of trap that you are using. Some traps operate such that they sub cool the condensate approaching the trap to prevent or minimize flashing. Others pass the condensate a or very close to saturated steam temperatures (in the main line.) You need to know the temperature of your condensate coming across the trap. The rest is basic thermodynamics.

rmw

 

[TD2K]

Good point RMW.