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Predicting Compressor Failure

Good Housekeeping

The most important factor in predicting compressor failure can be found by the cleanliness of the Oil. Virgin oil is clean, nonconductive and the primary insulator against voltage leakage to ground. Equipment manufacturers for the most part put together very clean systems and when properly maintained can last a long time. Service technicians do their part by taking all the right steps when opening systems for repair. But despite every precautionary measure taken by the manufacturer and service company, changes in the oil can occur beyond our control.

Refrigerant/Oil will combine and breakdown into water, acid, acid byproducts along with metal and metallic salts from corrosion and wear. These compounds will be found dissolved in the Oil Phase. The protection one would assume from driers is limited. Driers reach an equilibrium at about 20% capacity rejecting further moisture adsorption. The point at which drier material no longer serves to protect a system can be linked to the gradual increasing amounts of contaminant build up in the Oil.

Tools to predict changes in compressor oil have been around for the longest time, however you seldom see them on a service truck. My favorite has been the Megohmmeter, but how many technicians own or actually use a megger. Probably less than 1%.

Lower on my list is the compressor oil acid test. The acid test is no great predictor. A positive acid test only tells you, "your oil has no viscosity, your driers are filled to capacity and your compressor is nearly wasted". Few technicians really understand that acid build up is the consequence of years of neglect. Besides how many technicians are willing to do an acid test on a hermetic compressor. Not in my lifetime. Maybe if the semi has a crankcase drain plug. But the results of an acid test won’t tell me if a tornado is coming through town; it will only tell me the tornado has hit, and the town is leveled.

A good housekeeper wants to keep his customers running trouble free. Favorable referrals from satisfied customers build a foundation for every successful contractor. The housekeeper who keeps sweeping dirt under the rug will eventually build a pile high enough to smell.

Remodeling the Kitchen

We set out to develop an easy oil test that would have the same predictive value as the megaohmmeter. The oil test needed to detect elemental amounts of contamination in the bulk oil. In order to meet our goal, we looked for any new promising technology.

Everyone is familiar with dyes that sense pH - the infamous acid test. However, very few know about dyes that sense voltage (electrochromes), or dyes that sense light (photochromes), and there are also dyes that sense heat (thermochromes).

Duracell uses a green voltage indicating dye as their battery tester, a very successful product innovation.

A German mirror manufacturer developed a remarkable light sensitive dye. The dye darkened under bright sunlight then became more transparent as light diminished. First used on sunglasses and later used to coat rear view mirrors on luxury cars.

The science of dye chemistry was open to investigation in light of many new discoveries.

This Old House

Dyes that sense moisture have been in liquid line sight glasses for many years, but these dyes are not all they are built up to be. They have too broad a range to be practical or even remotely reliable. If you get a ton of water in a system, the color will change on the sight glass, but for the most part, your system can be very wet and still register a dry color reaction. Remember, with sight glass moisture indicators, you are relying on a dye technology developed before the television.

The New Yankee Workshop

Recently, a dye chemist was experimenting with coloring hazardous solvents. The aim was to identify solvents by their color. Sort of like why we color code Refrigerant tanks. He dyed some pure acetone red, as the acetone adsorbed moisture from the air, the dye began to darken to violet. Another moisture sensitive dye? Not quite, he was observing the acetone lose dielectric strength.

Hence the discovery of a brand new class of indicator dyes.

Mineral, Alkyl benzene and Polyol Ester oils all must have a very high dielectric strengths in order to insulate the compressor windings from voltage leakage to ground. It does not take much moisture to decrease the dielectric strength of Refrigeration Oil. Add some acid or dissolve a little metal in the oil and you’ve got a liquid conductor. We perfected dye derivatives which will produce color shifts at the slightest change in oil purity.

We initially calibrated the color chart of our Oil Test against readings obtained by a megaohmmeter on working compressors. However, when we compared the megger readings against a chemical oil analysis, we found a lot of fault in our old reliable megaohmmeter. It was obvious, my favorite instrument did not register changes in the oils composition quite as good as once thought. The megaohmmeter was registering good Oil in situations where we knew, from a chemical assay, the Oil was bad. The Oil Test was recalibrate to more closely match the laboratory results.

Better Homes than Yours

If you are a contractor who regularly sends out oil samples for wear analysis, you will find our oil test correlates accurately with the lab report. Furthermore, with our tester you get your results right on the spot.

We realize the majority of contractors never look to the oil for diagnosing system operation. The lack of interest lies in the hassle of obtaining an oil sample. With our test you simply "milk" the suction line for one drop of oil. All too easy…Whenever you can provide your present or potential long-term customer added service, you gain an important leg up on the competition.

For further information read our Checkmate Manual. The manual will explain how to use the Oil Test and interpret the results for corrective action.

Addendum

We tried a New Room Addition

The same dye derivatives used to indicate bad compressor oil; could also be used as a contamination indicator for vacuum pump oil. By adding a certain violet dye to a stock vacuum pump oil, the oil will eventually turn dark blue after about 2-3 systems evacuations. Great, an intelligent oil which tells you when it’s collected to much gunk and needs to be changed. Problems arose thereafter; since dyes that are capable of dissolving in oil tend to be acidic.

Corrosion and seal damage was prominent after a couple hundred operation hours. We could stop the metal corrosion by boosting the oil with inhibitors and antioxidants, but the seal shrinkage proved far too extreme to overcome.

We have postponed our new room addition for now, but will redraw some plans later.