Insulate condensate pipes? Yes or no?

RayWohlfarth

I am sort of torn with whether to recommend insulating condensate pipes for steam breweries. I know @DanHolohan recommends insulating them to reduce carbonic acid but I wonder if the condensate pumps can handle the temperatures. The picture is the disclaimer Armstrong has for the proper operation of the condensate pump. This isn't a slam on Armstrong Im assuming they all would have the same effect.

Assuming a 12 psi steam pressure for a brewery steam boiler, the steam temperature would be 243 degrees F This would make the condensate temperature about 223 degrees F @ atmospheric pressure which would flash to steam. Just curious about your thoughts. I am wondering if the insulation would be doing a disservice

Thanks

Jamie Hall

The problem -- and you are right, it's not confined to Armstrong -- is one of cavitation at the pump inlet at the higher temperatures. The comment in the disclaimer is rather mild, considering...

There really are only two solutions. Either raise the total pressure at the inlet, so the pump doesn't cavitate, or lower the fluid temperature. If you had a way to lower the pump two or three feet from the water level in the condensate tank, that would probably be enough (I'd have to run some numbers to check, that's a rough estimate) if you cou9ld drop the return temperature to 212 or so -- atmospheric. On the other hand, if the condensate really is at or close to 220, you might look at ways to maintain some pressure in the condensate tank to do the same sort of thing. But that would give back pressure on your condensate lines...

hmm. Let me think some more.

Dave Carpentier

Just throwing a completely uneducated idea out there..
Would there be a way to have a coil of cold water around the condensate pipe at some nominal distance from the pump ?

ChrisJ

Dave Carpentier said:

Just throwing a completely uneducated idea out there.. Would there be a way to have a coil of cold water around the condensate pipe at some nominal distance from the pump ?

You would then be paying to cool the condensate you went out of your way to keep hot.  The issue is the water boiling in the pump.



@Jamie Hall. How about reciprocating pumps instead of centrifugal?


If the condensate is going through a space that you want heated or a space where the heat ends up in an area you want heated id leave it exposed.

Jamie Hall

Well, recips are less sensitive to cavitation -- as are progressive cavity types -- but they are expensive to buy in any size and, except for some diaphragm types (which don't like high temperatures) are maintenance nightmares...

RayWohlfarth

I was wondering if the elevated boiler feed tank would be better than one at floor level.

Jamie Hall

yes

ChrisJ

Instead of pumping condensate, push it using compressed air in cycles

Jamie Hall

ChrisJ said:

Instead of pumping condensate, push it using compressed air in cycles

That would work... be a bit complicated. There are also steam injectors: https://en.wikipedia.org/wiki/Injector which work just fine.

JohnNY

Dave Carpentier said:

Just throwing a completely uneducated idea out there..
Would there be a way to have a coil of cold water around the condensate pipe at some nominal distance from the pump ?

There are several ways to do this smartly. We have run condensate lines through heat exchangers to warm hot water recirculation loops. They work to re-heat the water as it makes its way back to the water heater. We've also run hydronic floor heating loops off of condensate fed heat exchangers.
Where a boiler is being used, the result is cooler condensate making its way back to the receiving tank.

Keep in mind, much of the talk on this forum centers around residential heating systems. There are many commercial/industrial systems out there that, as a matter of process, dump all their hot condensate down the drain. It's those systems that tend to create the most opportunity to reclaim their otherwise lost energy.

EBEBRATT-Ed

@RayWohlfarth

The higher the condensate tank the more head on the pump which help. But it's not just cavitation it's seal life.

I haven't delt with this in a while, but I thought B& G had pumps that would pump high temperature water.


Steam driven condensate pumps are available from Armstrong, Sarco, Shipco etc

Pumpguy

For the high temperature condensate discussed in this thread, I would suggest looking into 2 FOOT NPSH type condensate pumps.

These pumps are very similar to conventional centrifugal type condensate pumps except in addition to the normal centrifugal type impeller, they also have an axial flow propeller mounted just ahead.

SHIPCO is one of at least two manufacturers I know of that makes these pumps. SHIPCO says theirs can handle condensate up to 210*F.

Pumpguy

Jamie Hall said:

yes

I agree. Just be sure only the receiver tank is elevated. You would need the pumps located well below the tank to get the needed NPSH.

RayWohlfarth

Thanks everyone i appreciate the expertise