2023 RETA Breeze March-April

Q A THE BEST OF RETA’S Q & A By James Marrella

over think the issues at hand. Second, we need to ask a very simple question as we maneuver through our decision process. The question? “Does this make sense?”And third, when it’s all said and done; “It is what it is.” Like it or not, you have to accept the results or have someone else prove your results are right or wrong. Okay with that behind us, let’s figure out what we want. The question at hand is how much refrigerant was released during a given time period from a liquid solenoid that was dripping four drops per minute (dpm)? Fairly straight forward. This is where we apply our first ground rule; “not to over think the issues”. Thus, the question at hand is how much is a drop of a given liquid? In our case ammonia. To answer this question I went surfing and back to school: 1U.S. Geological Survey’s (USGS) Water Science School. What I’m looking for is a “Drip calculator” (Figure 1): You know how much water does a leaking faucet waste? Even though our answer relates to water, we need to start some-where and this is where our second ground rule comes into play. “Does it make sense?” During my big adventure I learned a few things. First, there is no scientific definition of the volume of a faucet drip, but the folks who made up this drip chart

to use 1/4 milliliter (ml) as the volume of a faucet drip. With that said let’s get started. By these drip estimates of liquid dripping at 30 drops per minute (dpm) for one month you will have lost a total of 54 gallons of that liquid. Now, if we convert gallons per month to days we will have lost a total of 1.8 gallons per day over a 30-day month. See where I’m going? Now let’s convert 1.8 gallons per day to per hours. That equals 0.075 of a gallon per hour. Now, let’s convert the amount to per minute and that number equals 0.0013 of a gallon. Not done yet - we need to do one more thing; our answer is based on 30 drops per minute. We must divide 0.0013 of a gallon by 30 and then multiply by four, which equals, are you ready for this, our four drops per minute will give us 0.0001734 gallon per minute of a liquid. However, that is only one-half of our answer. Let’s assume that the solenoid was dripping for 24 hours. Total drip time would equal 1440.0 minutes, multiply that by our four drops per minute and that equals 0.2497 of a gallon. But we are not done yet. Our answer is based on a pure liquid with no flashing of the liquid as it hits the atmosphere. Again, let’s apply our first rule and for the sake of argument, assume that 25 percent of our liquid flashed off as it left the confinement of the refrigeration system, thus our new total is 0.312 gallons. Now, let’s convert all that over to pounds. You stated that it was sub-cooled liquid. Let’s assume the liquid was at +35°F which equals 5.39 lbs. per

The following Question and Answer (Q&A) last appeared in the RETA Breeze, March / April. 2010 and is still current today.

QUESTION: Ammonia releases: I have the calculation for leaks by IIAR, is there one for drips/drops? I have a 1/2” liquid line (SCHPL), 148psi that was dripping about four drops per minute. I’m trying to determine how much was lost from the time the solenoid was turned on until the leak was found and stopped. ANSWER: What a great question! Believe it or not I just completed calculations for a very similar “fugitive emission” issue. But, before we get into that, let’s establish some ground rules and the understanding when we do anything out of the unusual we need to be prepared to defend our action or better yet defend our thought process. In cases like yours I like to apply Marrella’s 1st and 2nd laws that influence our little world of industrial refrigeration; they are as follows: Marrella’s 1st Law: Anything complex can be broken down into simple elements. Marrella’s 2nd Law: Nothing is as simple as it seems. Now, for the ground rules: first, we need to apply some common sense and try not to

did (Webster Massachusettes). After measuring a number of kitchen and

bathroom sink faucets, for our calculations below (numbers are rounded), we are going

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