Previous in Forum: CFM of the Fan   Next in Forum: Name for Special Threaded Ring for Adjuster?
Close
Close
Close
9 comments
Associate

Join Date: Mar 2008
Location: Cape Town (where else)
Posts: 25

Insulating Steam and Condensate Lines Together

05/11/2011 10:40 AM

While performing a steam trap survey for a customer we noticed that the condensate return line temperature was between 120 - 130⁰C (248 - 266⁰F) at different places. The condensate return line runs back to the hotwell tank at the boiler and the tank is open to atmosphere with a 3" vent pipe. The boiler is only delivering about 1000 kg/hr .

We checked the complete system and found no leaking steam traps and no steam lines tied into the condensate system.

The plant is a textile factory and the lines to each press is only 1/2" in and out at about 8 bar (116 psig).

The only thing we noticed was that at one specific area where the condensate line was at its highest there were steam and condensate lines that had been insulated together in one insulation section. In other words, the two pipes were touching each other and the insulation was wrapped around them.

Could this be the cause of the high temperature in the condensate return line?

__________________
Well, I've got to get back to work. When I stop rowing, the slave ship just goes in circles
Register to Reply
Pathfinder Tags: condensate insulation steam
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".
2
Guru
Hobbies - Fishing - New Member

Join Date: Jun 2008
Location: Raleigh, NC USA
Posts: 13529
Good Answers: 467
#1

Re: Insulating steam and condensate lines together

05/11/2011 10:57 AM

Yes. This is not only transferring heat from the steam line to the condensate line, but the insulation around both is holding the heat in, giving it nowhere to go but the condensate line. Somebody goofed.

Unwrap them and reinsulate them separately.

__________________
Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety. Ben Franklin
Register to Reply Good Answer (Score 2)
Guru
Popular Science - Cosmology - New Member Engineering Fields - Civil Engineering - New Member Engineering Fields - Nuclear Engineering - New Member United States - Member - New Member

Join Date: Aug 2010
Posts: 714
Good Answers: 37
#2

Re: Insulating steam and condensate lines together

05/11/2011 10:58 AM

It sounds like an atypical installation to me.

The only other thing I would consider is the pressure on the condensate return line. For saturated steam systems temperature and pressure go hand-in-hand, so if the pressure on the return line is ~15 psi that would correspond to saturated steam at 250F (i.e. its normal and should be expected).

__________________
Sometimes my thoughts are in a degree of order so high even I don't get it...
Register to Reply
Associate

Join Date: Mar 2008
Location: Cape Town (where else)
Posts: 25
#3

Re: Insulating Steam and Condensate Lines Together

05/11/2011 12:15 PM

The pressure is 8 psi

__________________
Well, I've got to get back to work. When I stop rowing, the slave ship just goes in circles
Register to Reply
Guru
Popular Science - Cosmology - New Member Engineering Fields - Civil Engineering - New Member Engineering Fields - Nuclear Engineering - New Member United States - Member - New Member

Join Date: Aug 2010
Posts: 714
Good Answers: 37
#4
In reply to #3

Re: Insulating Steam and Condensate Lines Together

05/11/2011 12:29 PM

Saturation temperature for 8psig would be about 235F. So it appears the "condensate return" line is absorbing some heat from the steam line to the point it is no longer a condensate return but a super-heated steam return!

I'd venture a guess it probably makes alot of noise.

__________________
Sometimes my thoughts are in a degree of order so high even I don't get it...
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 30331
Good Answers: 818
#6
In reply to #4

Re: Insulating Steam and Condensate Lines Together

05/12/2011 3:51 AM

No, it won't be superheated, as there is still condensate present.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru
Popular Science - Cosmology - New Member Engineering Fields - Civil Engineering - New Member Engineering Fields - Nuclear Engineering - New Member United States - Member - New Member

Join Date: Aug 2010
Posts: 714
Good Answers: 37
#9
In reply to #6

Re: Insulating Steam and Condensate Lines Together

05/12/2011 9:53 AM

I'm sure there is condensate present (hence my comment about there being alot of noise).

However, the bulk temperature is ~250F with a pressure of 8psig. The steam table I'm looking at says that's superheated steam. Liquid water exists in that condition only transiently until it absorbs the heat to vaporize.

RE Post #7 boiling violently in the hotwell ... it's likely the 8psig steam expanding and collapsing in the hotwell.

__________________
Sometimes my thoughts are in a degree of order so high even I don't get it...
Register to Reply
Guru

Join Date: Dec 2006
Location: Hop around Toronto, New York & Karachi
Posts: 1878
Good Answers: 19
#5

Re: Insulating Steam and Condensate Lines Together

05/11/2011 11:29 PM

Karamat is right. This happens because the pipeline installer spaced the steam and condensate line so close that that the insulation space of minimum 5" (if each line has a 2" thickness insulation) was not there.As a result, both the lines were insulated together.Nevertheless, the steam line is radiating off its heat to the condensate line.

__________________
I not only use all the brains that I have, but all that I can borrow. Woodrow Wilson
Register to Reply Score 2 for Off Topic
Associate

Join Date: Mar 2008
Location: Cape Town (where else)
Posts: 25
#7

Re: Insulating Steam and Condensate Lines Together

05/12/2011 4:23 AM

And would this be sufficient to creat steam in the condensate line and cause the small hotwell tank to boil violently?

__________________
Well, I've got to get back to work. When I stop rowing, the slave ship just goes in circles
Register to Reply
Guru

Join Date: Dec 2006
Location: Hop around Toronto, New York & Karachi
Posts: 1878
Good Answers: 19
#8
In reply to #7

Re: Insulating Steam and Condensate Lines Together

05/12/2011 8:24 AM

No, because if the hotwell is vented then irrespective the temperature will be 99.9C.

The boil violently is the Flash steam. You need to study this. Or check with USL Detectors, 35% of steam traps may be passing steam.

__________________
I not only use all the brains that I have, but all that I can borrow. Woodrow Wilson
Register to Reply
Register to Reply 9 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".
Copy to Clipboard

Users who posted comments:

ChaoticIntellect (3); ducon (2); kramarat (1); PWSlack (1); Steam (2)

Previous in Forum: CFM of the Fan   Next in Forum: Name for Special Threaded Ring for Adjuster?

Advertisement