steam showing up in return in boiler

joe_14

the company i work for just got this small daycare for a acct. this is a three story building . built in 1950,was school then. it is a two pipe system witrh a boiler feed pump. the boiler feed is a little hihher than the return. it is piped with a 45  with a slow pitch to the feed tanks inlet. the distance is about 12 inchs. this has been this way for about ten years ,thats when the new boiler went in. the boiler is oversized for the building. was fired at 7.0 gph. on low fire when went to high firing rate was 11 gal gph.. boiler was short cycleing. would only run maybe a minute and reach high limt.

 i locked it into low fire now it runs a nice long cycle. but, now after the boiler runs about five minutes we are getting steam out of the vent at the recieving tank. its not flash steam  we are running the boiler at 2psi max. they said that they never noticed this before.

there are sarco steam traps at the raditors and f&t traps at the end of the feeds.. i am thinking that we have some bad traps,but i havent had any water hammering problems.



what i need to know is if i am on the right track or is there something else that could be happening. i think i could build a trap test station in the boiler room i know that this would help.



any help you can give me would be appreciated, i havent dealt with two pipe system that much. i mostly work on one pipe steam. and i would like very much to fix this. it has been a problem for a long time according to the people in the building.

also can anyone give me an idea of how to find the edr of some heating elements. most of them are 11/2 pipe with steel fins on them,most are tow rows and an average 15 to twenty lod. i would to be able to do and edr load of the building as you know thats the only way i can fire the boiler correctly.



thanks in advice i have a lot of respect for all of you and for dan and this site its GREAT.



joe g.

Unknown

Bump

Hi Joe- I'm giving you a bump as you're dropped off the front page

- Rod

joe_14

why

i am soory, but why did i get bumped . did i do something wrong.



thank you joe g

TomM

Bump

'bump' means someone does you a favor and posts to your thread, therefore moving your older message back to the top of the list.  Its a good thing, you've done nothing wrong.

.

[url=http://en.wikipedia.org/wiki/Bump_]http://en.wikipedia.org/wiki/Bump_(Internet)

joe_14

ok

thanks  i realy need some help on this one.



joe gxFiL48

Jamie Hall

There are only two ways

that steam can get into the returns on a two pipe system.  Either you have a bad trap (or traps) somewhere -- and it could be anywhere -- or there is a water seal somewhere which has gotten dewatered because the water line in the system was lowered.  My bet in this situation is that there is a bad trap or traps somewhere.  (there is no reason why a bad trap should necessarily cause water hammer, by the way).  The reason that it only shows up after the boiler has been on for a while is that only then has most of the radiation filled with steam.  Up until then, the system is condensing everything the boiler puts out.  Once it fills, though, if there is a bad trap (or missing water seal) the steam goes by into the return.



I usually use the yeouch method for finding bad traps, but IR thermometers and such are more sophisticated.  It can call for a lot of patience... but I'd start by following any returns which were warm, and see if they get warmer -- or hot!

joe_14

thanks

hi jamie; i thought that those were the only way steam could get in returns. but as i said i havent had a lot of experience with two pipe steam.

i am going to set up a trap testing station in the boiler room,that should help. and i do have a thermal raytek gun, that beats the ouch method.

thanks for you help i will keep you posted on how i make out.



joe g

Unknown

EDR Fins

Hi Joe-  For EDR on the finned heating elements, you maybe able to find something close to what you have in here. http://www.slantfin.com/documents/696.pdf

Divide the steam output number (BTUs) by 240 to get EDR.

I've also attached the Burnham Heating Helper that may have some info that you can use.



The IR guns work great on traps. "Santa" brought me one for Christmas. It takes a little time to get used to it.  Hold it close (less than a foot)  as the farther you get away from the trap, the wider area of heat it picks up. 

Bad trap stuck open = very close temperatures both sides of the trap (210 -212)

Bad trap stuck closed = radiator side hot -exit side  cool

Good trap =  radiator side 210-212+  - Exit side 180 -190.

I've only used it on thermostatic radiator traps so far so don't know how well it would work on an F/T trap though I imagine it would work similar.

- Rod

jpf321

fyi...what dan said

dan said at steam school .. the temp on F&T traps is the same the entire way through .. that is, the condensate is steam-hot .. the only way to test an F&T is to see what, if anything comes out .. at least that's what i remember him saying. 

Steamhead

Right about F&T traps and temperature

What we generally do is follow the hot pipe from the vent or tank all the way back to the source. A slight amount of leaking steam will condense in the return lines and not get as far as the vent. Since you're getting that much steam, something is leaking badly.



If the trail of steam leads to an F&T trap, rebuild or replace the trap. We like to use F&T traps that use standard 6-bolt face plates that carry both the float and thermostatic elements. These cover sizes from 3/4" to 1-1/2".



If there is a mix of trap brands in the building, change them over to one type as you go. Future maintenance is easier if you only have to keep one type of repair kit in stock for that building. In a larger building you may have to settle for two or three types.

Unknown

IR Thermometers and F&T Traps

Thanks for the info. That is very interesting. I can now see on an F&T trap where the temperature might be too close for the "touch method".  I haven't much experience with using an IR thermometer for steam but as they seem to be able to differentiate even a couple of degrees I wonder if they'd work reliably on an F&T trap as there should theoretically be a very minor difference in temperature of the inlet and outlet. I guess sometimes one can get too technical. Steamhead's method makes much more practical sense. 

- Rod

joe_14

steamhead.

i am  not sure what i am looking for when i am trying to determine how to find a bad f&t trap.  will the return line be hot in the whole system ,but hotter at the outlet of a bad f&t. can i set it up on a trap testing station. can i use an ir gun to shot temp and ehat temp diff am i looking for. sorry for being such a pain. but witrh your help i an learning every day

 with respect joe g

jpf321

TLAOSH

It's all in The Lost Art .. pages 150-156 ... you need to test them at a test station and you can't test them based on temp.