Main Steam Line Condensate

[robinxie]

Hi,everyone,

I need a thought about Main Steam Line Condensate. I have a 4.5km buried steam line @ 150psi. Beside this pipe lays a 15psi condensate line. I want to trap this main to the condensate pipe (Now the condensate just be drained to U/G). The load in the steam line is 90% for heating, 10% for domestic hot water. So in winter, it is under full load, in summer, it is very few flow.
How could I do that? Will it cause any problems if I tie-in the steam trap to the condensat line directly? Or I have to use flash tanks? Too many small flash tanks be needed, I do not think it is worth it.
Any help will be appreciated.

Robin

 

[ccfowler]

robinxie,

You have not provided enough information to permit a really coherent answer, so I'll just offer these thoughts.

What is the configuration of your system?

How big are the lines?

What is the function of the condensate line? Is it now returning condensate from the loads (heat exchangers) but not the condensate from traps?

Is the condensate line flowing full?

What about the risks and effects of a trap failure blowing steam straight through to the condensate line?

What about the chemistry (corrosivity) of the condensate in the line vs. the condensate from the traps?

Is the condensate from the traps worth recovering or must it be recovered for some other reason?

 

[robinxie]

ccfowler,

Thank you for your response. I do not have enough information yet. But what about the condensate line is full, and there is certain risk if the trap is failed?
Thank you again.

Robin

 

[ccfowler]

robinxie,

A 150 psig steam flow of potentially very significant volume dumping into a 15 psig condensate system seems like a dandy risk of commotion and damage in the condensate system. Even without a failed trap blowing through, there is still the matter of the hot condensate flashing into relatively large volumes of vapor in the 15 psig system. Can the condensate piping system and attached components withstand such flows and the resulting pressure surges and water hammer?

Dumping the trap flow from a 150 psig steam system into a 15 psig steam system for conservation of fluid and energy is a common practice. The flash steam becomes a part of the 15 psig steam flow, and the residual condensate simply joins the condensate flow into the traps of the 15 psig system. Simply dumping the trap flow into a 15 psig condensate system is another matter entirely.

How valuable is the trap flow from the 150 psig system vs. the cost of its safe recovery? Unless there is some compelling reason to recover this flow, it is not likely to be economically justifiable. You will have to determine the relative values for your system.

 

[robinxie]

Thank you very much, ccfowler.

Robin

 

[PeteBennett]

Agreed, dumping from main line at 10 Barg into 1.5 Barg could cause the condensate line to back pressure on traps further down line, even with non return valves, they may not be able to over come it. With 10Barg, which is about 100m of motive pressure do you not have any atmospheric vessel near by, such as a condensate pump header or vessel?

If you do recover it, with the flow fluctuations, what use would it be? What sort of flow rate are we talking about? Main line trapping is about 10% of max load (double on start up which is used for trap sizing.

There are also various bits of kit on the market these days that can solve the trap blowing issue, unluckilly can't recommend one cos I work for a company that makes them, thus can't advertise.

Sizing the flash units is a doddle, I can e-mail various charts etc if it would help?

 

[robinxie]

Thanks, PeteBennett. Yes, it would help. Please email to rxie@caltech.ca. Thanks again.

Robin

 

[quark]

Pete!

I generally use the data given by Spirax and Armstrong for flash vessels. If your charts are more descriptive, I would request for a copy at builblock1@yahoo.com

Thanks and Regards,

 

[PeteBennett]

Sorry quark, no more descritive as I do work for Spirax Sarco but thought it a bit off to metion it (sounds like a sales pitch otherwise)

A question for you though as you have been on this site longer than me, and Robin sorry for ambushing your string, is there a specifc group for steam issues?

 

[quark]

Threads often come up in the following forums.

forum794 - Boiler and Pressure Vessel Engineering
forum124 - Chemical Plant Design
forum135 - Chemical Engineering and Other Topics

and sometimes in
forum391 - Heat Transfer and Thermodynamics Engineering

One favour if you could do, can I have some design data/charts regarding ThermoCompressors please

Regards,

 

[steam4]

Quark,

Try the Schutte&Koerting website:

http://www.s-k.com/pr_termo.htm

Dave