Ammonia Liquid Migration and Cold Weather Startup

Ammonia Liquid Migration and Cold Weather Startup

Author: Erik Hansen

                Those of us in the northern climates are familiar with the cruel outside conditions.  Old Man Winter lets loose his cool breathe and our backyards and driveways become frigid winter lands that make us always think…“why the hell do I live here again?!”  Those of us in the northern climates and familiar with central ammonia refrigeration systems are also met with another all-too-common inconvenience and that is liquid refrigerant migration and cold weather startup of our systems.

                Typically, in low load or no load scenarios liquid ammonia will “migrate” to the condenser on the cold rooftop.  This doesn’t really happen the way you think in that the liquid doesn’t actually move from one spot to the other.  Instead, the vapor in the cold area condenses, creating a localized lower pressure area, thus drawing more vapor from higher pressure areas, where it condenses more, and so-on.  Carlson and Stewart Refrigeration is not unfamiliar with this phenomenon and has a solution!  Let us know if you experience this issue and we can visit with you on some options.

                Another item that comes from the cold is challenges with restarting a system backup in the cold months.  Head pressure is so low, that it is often hard to “push” liquid refrigerant to the plant.  This means that the compressors that are attempting to run will trip out quickly on low suction pressure.  This whole scenario usually can be overcome given time and patience, but it can often times delay plant start times which is very much problematic and usually has the production manager impatiently waiting for the refrigeration operator to fix it.

                Once again, Carlson and Stewart Refrigeration has a solution to this and can help you with developing a strategy to address this “cold weather startup” concern so are not left out in the cold!