2019 Breeze Jan-Feb

suction temperature reached -24°F there was a flooding back of liquid to the suction accumulator that protected the compressor. Apparently there was a four degree temperature differential between the exterior surface of the suction pipe and the refrigerant flowing inside the suction line. The carry over stopped when the thermostatic expansion valve was adjusted higher to a -23°F tempera- ture. The production improved to 78 tons overnight. The thickness of the ice evaporator was starving even though ice was produced from the bottom to the top of the heat exchange surface. Refrigeration production is a combina- tion of the correct amount of boiling liquid at the correct pressure applied to clean surfaces on both sides of the heat transfer surface. Conclusion: A few lessons were learned here. First, just because it has “always been this way” does not mean that the system is being operated correctly in the first place. Operators who train in on a system as it is – and do not have the benefit of learning what the system SHOULD be doing perpetuate inefficien- cy and excess cost. The years of poor ice making cost that operation more than $50,000 in electrical costs and that doesn’t account for the ice they had to purchase from others to provide slush ice for broccoli cooling for their custom- ers. Second, it pays to enlist the support of peers to troubleshoot a problem once it is recognized. You only “know”what you know…..increasing your knowledge pool by involving others and learning together and successfully improving a situation brings reward and opportunity. Thirdly, the most complex system is a collection of smaller sub-systems. Understanding the fundamentals and having the skill to apply that fundamen- tal knowledge to determine if the system is doing what it should be is key to being a skilled operator. near the top of the heat exchange surface increased significantly. In hindsight it was apparent that the

static valve would not properly feed a vessel. What a paradox. There is an exception to this “rule” however. There are special thermostatic expansion valves that have a superheat sensing bulb that is inserted in a well that is heated by a resistance heater powered by a 24VAC power supply. The resistor is cooled by the liquid level that builds up by the liquid passing through the thermostatic expansion valve. The heating and cooling of the superheat bulb serves to maintain the liquid level in the vessel. Ingenious! The operator checked the voltage and amperage pass-

ing through the sensing bulb heater and found it to be as it was supposed to be. Thermostatic expansion valves have adjusting stems. In 1989 the “word”was that these stems were NOT to be touched because bad things happen when superheat spring stems are touched. The operator adjusted the superheat spring and noted that the temperature of the vapor leaving the surge drum reduced down toward zero degrees F. The adjustments were done in 1/8 turn increments and the change of temperature was observed until there was no further change. When the

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