Algae

icy78

Got a 4 story office building with approx 20 VAV boxes with 30% propylene.
 These are low gpm reheat coils of .6 to 1.2 gpm. They all have automatic balancing valves. 
. This is what I found in one of them on the top floor. Its thick and slimy.
  I found a problem with the extank and have fixed that.
  However, definatly for many weeks, possibly months and maybe years,  the boiler relief has popped, draining back into the glycol makeup tank, while the pressure has dropped below atmospheric up by the open auto vents and allowed air to enter, before the makeup can catch up.
  So my conjectured senario is the above, and that caused /allowed algae to grow.
 It that probable? Also there is a bag side stream filter that gets   black muck in it. They say theres usually that much twice a year. So say ½ cupful each time.
  There is also a pic of water treatment report, which says things are all good, which I dont know how to decipher.
The office heat line is this system. 
I think this needs a good flushing and chemical cleaning and new glycol. Altho I want to talk them into straight water. It's been converted to glycol after there were 2 separate instances of coil burst due to lack of low SAT shut down in the old RTUs.
(New rtus now and it would not be a big deal to add redundant shutdowns.)
Anyhow, really needing input on how to proceed, or to read.
Thanks!

Report from this year this month.

Jamie Hall

Oh just lovely. It surely does need a good biocide cleaning. the whole system -- because those biofilms which you are seeing where you can see them will also be all through the piping as well. There are a number of approved biocides; some of them are less hazardous than others. Chlorine -- in high concentration -- works, but there are others which are better.

The system will have to be circulated, biocide introduced, allowed to work, then you will have to flush the dickens out of it and do it again. And, probably again.

Some o those biofilms are quite hazardous to human health, so it might be best to find a specialty company to do the work -- and guarantee it.

EBEBRATT-Ed

Yes, glycol degrades when it contacts air and causes all sorts of issues and water treatment is not my thing so I will leave that to others.

You going to have to flush and clean and may have hazardous waste to dispose of. There are companies that do that

icy78

Thanks guys. Kind of what I was thinking.
Wondering if @Hotrod has any thought too.
    I think this type of situation is rare maybe?

EBEBRATT-Ed

@icy78
Not rare. I don't know the installed life of glycol but i think its only 5 years or so an it has to be maintained

I have seen systems get screwed up when the glycol goes bad

Solid_Fuel_Man

Man I hate glycol.....

icy78

Solid_Fuel_Man said:

Man I hate glycol....

No kidding! Pump losses, heat transfer losses, mess, biologicals, expense. And now ALGAE.

jumper

DOW wanted customer to send samples regularly and then DOW sold stuff that kept inhibitor functional. That was for chilled water closed systems. Cooked glycol is probably worse.

DowCorning offered superior (they said) silicone thermal fluids. Then the silicone boob debacle dampened DowCorning's appetite to innovate.