Steam-to-water HX pressure relief, vacuum breaking, and air removal
Steam-to-water HX pressure relief, vacuum breaking, and air removal
(OP)
I am installing a steam-to-water HX with 450 F, 40-60 psig superheated steam. (Our plant has no saturated steam distribution system, so we're stuck with using superheated steam. Our HX is selected and sized for this at our design conditions.) I'm wondering about what components I need on the unit for pressure relief, vacuum breaking, and air removal. The first is essential, of course. I'd say the second is as well. As for air removal, an F&T steam trap on the condensate line can remove air, but wouldn't I also want an automatic air vent on the top to remove air especially during S/U? Also, the HX has two 3/4" connections, one on the top of the shell and one on the elliptical head near the steam inlet, which is near the top of the shell but not quite at the top? Could I put all three off of the top connection, or can/should I use the connection on the elliptical head? Thanks.





RE: Steam-to-water HX pressure relief, vacuum breaking, and air removal
RE: Steam-to-water HX pressure relief, vacuum breaking, and air removal
RE: Steam-to-water HX pressure relief, vacuum breaking, and air removal
Until you get past the superheat, your heat exchanger will behave as if it is airbound.
RE: Steam-to-water HX pressure relief, vacuum breaking, and air removal
RE: Steam-to-water HX pressure relief, vacuum breaking, and air removal
RE: Steam-to-water HX pressure relief, vacuum breaking, and air removal
By orifice trap, are you referring to the trap from the condensate nozzle (i.e., shell outlet flow)? I am intending to use a F&T trap since the condition there should be no different than if a shell-and-tube HX with saturated steam coming in and saturated condensate leaving. I don't understand why I would want to use an orifice trap unless you're referring to a different location on the HX.
RE: Steam-to-water HX pressure relief, vacuum breaking, and air removal
I am from Europe - and maybe that's why I don't get all your expressions correct but this are my comments:
- usually you vent and drain at start up with manual valves - if you want you can make this valves with actuator (electrical or pneumatic) - but that's expensive solution as needed only for start-up.
- during operation is good idea to have continuous air venting from steam space (as removal of non-condensable gasses). This is usually done at steam-condensate surface inside heat exchanger - as this inert gasses will be released exactly at this point.
- Vacuum breaker standard place is highest point of steam inlet pipe - after control valve.
RE: Steam-to-water HX pressure relief, vacuum breaking, and air removal
Go ahead, use the F&T trap, if it does not work, go back to orifice.
And please let us know the results.
Good luck and goodbye. GenBlr.