Steam Traps to Control Sump Temperature

[RJB32482]

Hi Guys,
There is an old project that I have been assigned to dealing with controling our sump temperature during the winter months. The proposed packaging ddelt with having a steam trap control the temperature. It is a 80 psig steam line. Is the principal that condesate would build up in the line before the steam trap, then occasionally open up to let condesate out? This condesate should then heat up the sump.

Thanks

 

[TBP]

The trap discharging to the sump will certainly add heat, but how much heat will be driven by whatever is condensing the steam ahead of the trap. A trap is simply an automatic valve. It'll open when it sees air or water, and will close when it sense steam, and that's all. You may get just the right amount of heat, not enough heat, or too much heat in your sump. The trap will simply open when it senses condensate, with no regard for sump temperature.

 

[RJB32482]

Thanks for the info. Will just blocking the path of the steam with the trap make air and condesate and open up the steam trap?

 

[TBP]

Another way to look at traps, is that they hold the steam back until it gives up it's latent heat. Traps will be on the outlet of coils, heat exchangers, on drip legs, etc. Something else, other than the trap, will cause the steam to actually condense - another fluid flow in a HX or coil, or just heat loss through insulation on a steam main. If you have 50 feet of uninsulated say, 6" uninsulated steam main ahead of a drip trap, that trap will need to handle far more condensate than if the line had 2" of insulation on it. You'll get a little bit of condensation due to heat loss through the trap body, but that amount will be dwarfed by the other factors.

 

[RJB32482]

Thanks for the good info. Could the sump temperature be controlled by an automatic valve (opens when the thermocouple gets to a certain low temperature) where steam is before the automatic valve? Then a trap could be connected to the leg also to remove condesate from the line when the steam is not on? What would be the problems with this type of system?

Thanks again.

 

[TBP]

You can install a temp control valve on a steam line to the sump, and have the sensing element in the sump. You might need to get this elaborate, or just the trap discharge may take you where you need to go. (It sounds like it's the easiest thing to try - a few feet pipe and a couple of fittings?

It's pretty hard to tell what's the best way to go without seeing the installation. If it's not a big sump, and/or it doesn't get really cold, you might want to check out a small electric immersion heater.

 

[RJB32482]

OK, one more question. If I wanted to manually control the temperature of the sump (temp low alarm operator operates manual valve for steam), would I need a steam trap for the line if the valve would just block the steam path (no path for the steam to escape? I'm new with steam lines and would not know how built up condesate would effect other factors (piping, etc.).

Thanks

 

[TBP]

You need a way for the air that is in the line, and the condensate that will form, to get out, so that (more) steam can get in. If the steam line sits full of condensate long enough, the condensate will cool, and freeze nicely, right along with the sump water. This is over and above the potential for some "interesting" water hammer possiblities.

The other extreme, is that the steam line will be manually put in service on a low temp condition, and will be forgotten. You could literally boil the sump water, which is wasting energy, and will very likely kill your sump pump.

Spirax Sarco, Armstrong, Hoffman, etc have some excellent literature on steam systems. The local reps are also usually keenly interested in having their products used correctly, and will typically be happy to provide on the scene help.