INCORPORATING COLD CHAIN
FEATURE the low side piping . When the system is operating normally , pressures are maintained below the rated pressure of the system . The CO 2 system pressure becomes a safety concern when liquid becomes trapped in a portion of the system that is not rated for the full pressure at higher temperature ,” he says . “ It is therefore critical not to allow liquid
CO 2 to become trapped in the system without means of pressure relief . As the temperature of a saturated mixture rises , pressure will rise until it reaches the saturation pressure in the table above . If the refrigerant pressure exceeds the rating of the piping , valves , or other components of the system , this can lead to leaks and possibly bursting of system components .
“ Measures must be taken in system design to ensure that pressure cannot build up in any portion of the system . All components , valves , piping , fittings and joining methods are to be verified to ensure pressure ratings above the maximum anticipated system pressures .
“ On CO 2 systems , pressure relief devices must be appropriately located to allow the system to vent safely in the event of a system shutdown or other event that causes pressures above system ratings . All points within the system must be allowed to vent back to the pressure relief valves without restriction . Check valves are typically utilised to allow portions of the system to vent back to receivers , where pressure relief valves are located . Any portion of the system that cannot vent back to the receiver must have its own pressure relief valve .”
Laidlaw highlights a particular issue with CO 2 as being the formation of dry ice , which is simply CO 2 in solid form . In a CO 2 refrigeration system , there are two common conditions where this may occur .
• The first and potentially dangerous location is at a pressure relief valve . When a pressure relief valve is open , the refrigerant is undergoing a rapid drop in pressure from system pressure to atmospheric pressure . If liquid CO 2 is being released , the CO 2 release in a solid and vapour mixture causes the formation of dry ice . Therefore , pressure relief valves should not have any piping installed downstream of the valve . If the pressure drop happens inside the pipe , dry ice will form , blocking flow and preventing pressure from being released .
• The second condition where dry ice may form is when charging the system . If the system vacuum is broken with liquid , dry ice can form inside the system , again restricting flow . This condition is less dangerous because it does not cause pressure buildup beyond system ratings but should still be avoided .
AMMONIA USAGE IN COMMERCIAL COLD STORES IS INCREASING
In recent years , there has been a noticeable surge in the utilisation of ammonia as a refrigerant across various industries . Notably , ammonia emerges as a cost-effective alternative , particularly for larger capacity cooling applications , owing to its lower operational expenses , says
Zayd Fredericks , industrial refrigeration representative at Metraclark .
He explains that Metraclark has witnessed a significant increase in demand for ammonia-related equipment . According to Fredericks , this uptick in demand aligns with the growing need for efficient refrigeration solutions , especially among companies involved in cold storage , logistics , breweries , poultry and retail distribution centres .
The reason for choosing ammonia system cooling solutions can be attributed to its cost-efficiency , especially in the face of rising energy costs . Unlike traditional refrigerants like Freon , which may have lower initial capital costs but higher operational expenses , the running costs associated with ammonia are substantially lower . This cost advantage makes it an attractive option for businesses seeking to optimise their operational expenditures in the long term .
“ Despite the higher initial investment required for installing ammonia-based systems , the potential for long-term savings outweighs this drawback for many businesses . While consulting engineers often face challenges in convincing clients to invest in equipment upgrades due to concerns over upfront costs , the cost-effectiveness of ammonia presents a compelling case for consideration ,” he adds .
The trend towards increased adoption of ammonia as a refrigerant is not limited to a specific industry or geographic region , says Fredericks . “ This growth trajectory is expected to continue , driven primarily by the economic benefits and operational efficiencies offered by this natural refrigerant .”
Beyond mere sales , Fredericks emphasises understanding the benefits of ammonia , particularly in long-term operational efficiency . According to their observations , major cold storage players are strategic in their decisionmaking processes , indicating that the shift towards ammonia is not impulsive but rather a carefully planned endeavour .
The rationale behind this strategic shift varies across different sectors . While food security emerges as a primary concern for cold storage facilities , breweries and dairies , the beverage industry operates on a more predictable growth trajectory driven by consumer demand . This dichotomy underscores the importance of cultural and economic factors in shaping industry preferences .
Despite limited information on specific projects , anecdotal evidence suggests
Commencing in 2024 , South Africa embarks on the phasedown of HFCs with a gradual reduction in the volume of imported
refrigerants .
COLD LINK AFRICA • June 2024 www . coldlinkafrica . co . za 15