TECHNICAL DETAILS

Water contamination of the ammonia refrigerant is common in many refrigerating systems. The solubility characteristics of ammonia in water allow an aqueous ammonia solution to be formed which replaces the anhydrous ammonia refrigerant. In many systems this change occurs over a period of time and the effects go unnoticed. As a result the penalties experienced in coping with these unknown changing conditions become continuous and increasingly greater.

The pressure-temperature relationship for aqueous ammonia solutions is different than that for anhydrous ammonia. At a given pressure the saturated temperature for anhydrous ammonia will be lower than the saturated temperature for an aqueous solution. As the aqueous solution becomes more dilute (water content is increased), the saturated temperature becomes higher. Which results in decrease of freezing efficiency.

Consequences of Water in Ammonia Systems
• Increased power consumption
• Reduced refrigeration capacity
• Lower evap pressure at the same temperature
• Oil is broken down and creates nitro compounds
• Nitro compounds can dissolve in the NH3 and colour it
• Leaks due to embrittlement of O-rings and gaskets
• Leaks due to galvanic corrosion
• Wear and tear on valves and controls
• Sludge in the system

Measuring Water in Ammonia
Measuring water in Ammonia is easy for any trained technician to do, you can simply drain off 100mL of Ammonia from the low side, and leave it in an safe, open place to evaporate – then measure the remaining water content. Alternatively if a recirculated evaporator is operating a few degrees higher than what it’s pressure gauge indicates, this is also a sign of a water contaminated system!