steam condensate line design

[roberto70]

With reference to steam condensate lines design, I would have your opinion about this matter.
If line are proper designed for two phase flow according the maps (let's say annular/wave or bubble flow) there is any risk of slug flow?
For a steam condensate line be free draining is mandatory or it is simply "good practice" but not required in any design criteria/code?
Thanks
Roberto

 

[quark]

Slug flow shouldn't occur if you provide proper slope and traping. I didn't get your point about free draining. It is driven by steam pressure. I recommend you to go through the following document.

http://www.armstrong.be/pdf/N_101.pdf

 

[roberto70]

Thanks Quark.
But sloping is a requirement? If lines are designed properly and condensate network is operating in pressure, is slope required?
Thanks

 

[TD2K]

I have not seen 'slope' typically added to condensate return headers on P&IDs unlike for example, flare headers.

 

[roberto70]

In fact for flare headers slope is a typical requirement for DEP shell, for example.
For steam condensate is preferred, if possibile, but is not unusual see condensate return line at lower level of pipe racks, rising for road cross.

 

[Yorkman]

What is the pressure of the vessel that you are trying to get the steam condensate back to? Is it atmospheric? Steam can be used to lift/push the condensate but it must be at a high enough pressure to overcome what ever lift, pressure drop and or existing back pressure exists in the condensate return line. If you are relying on the steam to perform in this matter a check valve is generally installed after the trap. Also remember if it's not a free draining system condensate freeze ups due to low ambient temperatures,are a greater threat.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[roberto70]

The condensate flash drum is atmospheric, and steam users are working at 5 bar g.highest point on rack is 10 meters so there is no problem with water column head. The same condensate header collects MP steam traps discharge (30 bar g),but MP steam is strongly superheated (120°C) so that expected condensate flow rate is very low.
Minimum ambient temperature is 4°C so there is no problem with freezing.

 

[Yorkman]

The only issue that you might have is a MP steam trap failure pressurizing the condensate return header. At that point it is very likely that you will expierence the slugging or water "hammer" as the MP steam entered the return line. Of course you could have the same problem with a LP trap failure too. Regular maintance inspections on the steam traps goes without saying.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI

 

[roberto70]

A steam trap monitoring system has been forseen