Steam condensate return piping - cannot continuously slope down

[MinnesotaSlinger]

We are installing a 125 psig steam main through the basement of a building. The amount of ceiling space is quite limited and the run through the building is several hundred feet, so we'll have to trap at every steam main low point where it rises up before sloping to the next low point. My question though is about the corresponding condensate return line that will serve the traps on the steam line. It's typically suggested to slope a condensate line back to the flash tank (and, in our case, we have a 15 psig system we intend to serve with recovery steam), but there isn't ceiling space to continuously slope the condensate return the whole way back to the flash tank. So long as the steam line is under pressure, there will be motive force to push condensate/flash steam through the condensate line back to the flash tank without relying on gravity, but if there are any low points in the line, I'd worry about water hammer if a burst of 2-phase flow collides with condensate pooled at a low point. Is there good guidance somewhere in how to pipe a condensate return line when you can't continuously slope it down the whole way? Thanks.

 

[georgeverghese]

Agree with your concerns re slugging / water hammer / high backpressure on trap exits. Suggest setting up a central condensate collection drum within this basement at a point lower than the lowest steam trap. Pump out condensate from this drum with on-off level control into the flash drum / tank. Route the vapor from this basement low point drum through a no pocket line to this flash tank also, entering this tank through a dedicated vapor feed nozzle.

 

[EdStainless]

The potential for variable back pressure on the traps is also a serious issue.
I like Goerge's idea, can you make that work?

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P.E. Metallurgy, Plymouth Tube

 

[georgeverghese]

Another option that may be cheaper and perhaps simpler in this application is to side step the pipewall condensation issue altogether - electric trace the entire basement header, since the tracing load should be small. From steam tables, 125psig sat steam is at about 177degC, so that excludes self regulating style tracing (good for up to 120degC only), so try constant wattage HPT - parallel resistance or HTEK style - series resistance cables from Thermon (say). HPT is more reliable generally compared to HTEK, since HPT is parallel resistance. Thermon folks can walk you through this electric tracing option if you arent familiar with this. Similar constant wattage style tracing should be available from other competitors also.

 

[curtis2004]

Hi Guys,

I don't think heat tracing is going to work, because you have to keep pipe temperature to saturation temperature. This is impractical.

Do you have a space available for straight condensate line without any slope? If you have, then screw the idea of sloping it.
Just select bigger size condensate pipe and try to support it more often then required. This will reduce pipe deflection and will keep condensate flowing.
You may have your steam traps installed below condesate return line and have "a lift" from steam trap to condesate line. So your line from steam trap to condesate line will be always flooded with condesate.
What size steam and condesate lines are we talking about?

Thanks,
Curtis

 

[LittleInch]

That was my thinking also to have a dead flat line oversized so say a 6" line instead of a 2" line. All depends on flow rates and flow conditions in the pipe.

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[georgeverghese]

From my experience with heat tracing, dont see a reason why this shouldnt work - Thermon can run the heat transfer calcs (for both heat leak into the pipe and out of the pipe through insulation) and confirm. Pipe wall OD temp can be kept in the range ON at 175 - OFF at 180degC say.