Critically Charged Systems

Since the advent of the mandated Process Safety Management program (PSM) the industrial refrigeration sector has been faced with attempts to maintain lower refrigerant charges (re: inventories of refrigerant used in the system).  To date, most of the efforts expended focus on keeping the ammonia refrigerant charge under 10,000 pounds.  To a degree, this has largely centered around minimizing the quantity or use of gravity-flooded air-cooling evaporators or flooded shell and tube heat chillers.  While these methods will drastically reduce the total refrigerant charge, other methods can be applicable.  These typically involve re-thinking the basic premise for the use of a refrigerant and the application of specific sub-systems that are used in ammonia refrigeration systems.

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If you think you may have a problem with draining liquid ammonia from your evaporative condensers, you may want to investigate the equalizing line.  This piece of pipe is typically installed on top of the high pressure receiver.  The termination of this pipe is usually the discharge line leading to the condensers.

What follows is a brief description of how the equalizing line works.

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