VENTILATION


All mechanical refrigeration codes have a minimum required rate of ventilation for both normal occupancy and during ammonia releases. Note that these are minimum prescribed values and increasing above and beyond these values will make the room safer in an emergency. Examples were given where high ventilation rates in some plant rooms allowed maintenance mechanics to enter without being threatened by significant ammonia leaks. It was pointed out that there must be make-up air dampers that will allow an equal volume of fresh air to enter or a negative pressure can develop that will make opening doors difficult or impossible. It was discussed that ammonia detectors should be placed in a way that is representative of the leak in the room and not in the entering fresh air stream, which could prematurely shut off ventilation and make an unsafe condition.


It was mentioned that in colder climates preheating the


incoming air would be required, so the higher flow rates should be limited to emergency fan operation during higher ammonia concentrations of 300ppm and above.


An excellent suggestion was to carry out a smoke test in the


mechanical room to ensure that all working areas are provided fresh air in the event of a refrigerant release.


WHY IS AMMONIA STILL USED AS A REFRIGERANT?


Tere have been close to 100 refrigerants that have entered the industrial refrigeration market in the last 50 years and all of them come with their own set of problems, including increased costs, high undetected leak rates, premature compressor wear, ozone depletion, and global warming, to name a few. Most of the alternatives that have been employed over the years are extremely harmful to the environment. It was noted that all refrigerants are dangerous and there have been many fatalities because of the “safe” alternatives. It is imperative that all equipment rooms have proper leak detection and ventilation and that operators be trained on the hazards posed by the refrigerant in the system they oversee.


Some of the significant reasons why ammonia will continue to be Most efficient refrigerant


used as a primary refrigerant are as follows: •


• Least expensive refrigerant • Lowest leak-rate refrigerant • Has zero ozone depletion


• Has zero global warming potential


• A reliable refrigerant requiring minimal instrumentation • Only self-alarming refrigerant due to its pungent odor • Returns to natural elements within 72 hours of being released


WHAT DIRECTION ARE PEOPLE TAKING INTERNATIONALLY?


At the 2016 Atmosphere America Convention, the majority of those polled agreed that low-charge ammonia or Ammonia/ CO2 was the best choice for natural industrial refrigeration that isn’t harmful to the environment.


During the 2016 Atmosphere America Convention held in Chicago in June 2016, a vote was taken to determine the best direction forward for industrial refrigeration. Tis annual conference is attended by industry leaders from around the world with the mandate of promoting the use of natural refrigerants that are not harmful to the environment. Te consensus on the best way forward was a combined 83 percent on low-charge ammonia or ammonia/CO2.


Which technology is the future for industrial refrigeration? Low-charge ammonia


60% Amonia/CO2 C02 transcritical


Hydrocarbons 2%


Other 0% CONSTRUCTION PRACTICES


It is important to keep the ammonia inside the system and to prevent leaks. In the past, many leaks came from leaking valve packings and flanges.


Seal capped valves prevent packing leaks, but it is imperative


that the tools be in the room to take the caps off and to close the valves quickly.


Installing fully welded valves will reduce leaks caused by


leaking flanges affected by expansion and contraction during normal operating cycles.


LIMITED-CHARGE CHILLERS


Most ammonia ice rink refrigeration plants that have been installed in North America have been a traditional shell and tube design. A shell and tube chiller can require an ammonia charge of over 700 pounds for a single ice rink. Modern flooded plate and frame and plate and shell chillers are more expensive but can reduce the ammonia charge to less than 150 pounds, and with direct expansion chillers it is even possible to reduce the ammonia charge to less than 100 pounds.


LEAK-ACTIVATED ISOLATION VALVES


Installing leak-activated isolation valves provides a high level of safety in that up to 95 percent of the refrigerant charge can be securely held inside the chiller until the situation can be investigated and rectified.


DRAINING OIL POTS


Te safest way to drain an oil pot is to close the liquid feed to the pot and leave the vent line between the pot and the top of the chiller open. Let the pot sit for several days and all the liquid ammonia will evaporate out of the oil. When the oil pot reaches room temperature, close the vent and you can safely drain pure


SPRING 2018 13 15% 23%


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