Originally Posted by
HVACRsaurus
Hey guys.
I've had situations on at least three ammonia refrigeration plants (that run positive pressure) which seem to accumulate non condensibles.
There does not seem to be a common thread between them as to why it happens.
1). I have seen it happen on a +25kpa plant which has been maintained well, with minimal opening of system (and reasonable purging of any works).*
2). I have seen a truck load of non condensibles appear almost out of the blue (and quite quickly) on a different positive pressure pant that barely had any significant works at all. On said plant I have seen the purger accrue significant purge hours & characteristic round medium sized bubbles in tattler bucket.*
3). I have also seen it happen on a +200kpa plant which requires quite regular purging.
I have done a small amount of research into the issue, questions have been raised about the possibility of the ammonia breaking down & becomming Nitrogen + Hydrogen (in their gaseous forms), however information that I have found relating to breakdown of ammonia due to temperature suggests that it only happens in the order of 450 - 500°C (unlikely temperatures for a standard two stage system).
Another possibility is that some sort of electrolytic action causes the ammonia to break down.
Perhaps others have experienced something similar - or maybe the systems that I'm talking about have other reasons a to why it's happening. Either way, for the time being, I just accept that it "seems" to happen and I watch for the tell tale signs & purge accordingly.
Mr Saurus.