Ocena właściwości tribologicznych olejów mineralnych przeznaczonych do stosowania z węglowodorowymi czynnikami chłodniczymi w warunkach skąpego smarowania

In refrigeration compressors, the amount of oil in tribocontacts in certain situations may be insufficient. In this case, poor lubrication conditions may occur. There may also be a situation in which the areas of lubrication lack lubricant and the lubrication of the friction pairs will be carried out by only the refrigerant. The requirements related to legal regulations and concerning refrigerants result in the return to the use of natural substances such as hydrocarbons. These substances do not contribute to the enlargement of the ozone hole and the greenhouse effect. The most commonly used refrigerant in the group of low-capacity devices is R600a (isobutene). The article verifies the test method allowing one to assess lubricity properties of oils for refrigeration compressors in the mixture with a refrigerant under the conditions of poor lubrication. The article also contains the results of wear tests which allow one to assess and contrast lubricity properties of oil–refrigerant mixtures for three mineral oils of the same viscosity grade under the conditions of poor lubrication in cooperation with R600a. The tests were performed for the air, R600a, mineral oils, and oil–refrigerant mixtures.W sprężarkach chłodniczych może wystąpić sytuacja, w której ilość oleju w węzłach tarcia jest niewystarczająca, co powoduje niedostateczne warunki smarowanie. Może również zaistnieć sytuacja, w której środka smarnego zabraknie w obszarach tarcia, a smarowanie węzłów będzie realizowane tylko przez czynnik chłodniczy. Wymuszenia związane z przepisami prawnymi dotyczącymi czynników chłodniczych skutkują powrotem do stosowania naturalnych substancji, np. węglowodorów. Są to substancje, które nie przyczyniają się do powiększania dziury ozonowej oraz efektu cieplarnianego. Najpowszechniej stosowanym czynnikiem chłod-niczym w grupie urządzeń o małej wydajności jest R600a (izobutan). W artykule przedstawiono weryfikację metody badań pozwalających na ocenę właściwości smarnych olejów do sprężarek chłodniczych w mieszaninie z czynnikiem chłodniczym w warunkach skąpego smarowania. Umieszczono również wyniki badań zużyciowych pozwalających na ocenę i porównanie właściwości smar¬nych mieszanin olej–czynnik chłodniczy dla trzech olejów mineralnych o tej samej klasie lepkości w warunkach skąpego smarowania przy współpracy z czynnikiem chłodniczym R600a. Badania wykonywano dla powietrza, czynnika chłodniczego R600a, olejów mineralnych oraz mieszanin olej–czynnik chłodniczy

Mixtures of Lubricants and Ecological Refrigerants under Starved Lubrication Conditions

The presented results show that the presence of refrigerant significantly deteriorates the lubricating properties of compressor oil under starved lubrication conditions (with a small amount of oil). The change can be 40–120% compared to the properties of the oil alone. Additionally, in the group of oils that are substitutes (operational alternatives) compatible with a given refrigerant, the effect of the refrigerant on the lubricating properties varies. The differences can be as much as 25%. In order to evaluate and properly select compressor oils for the refrigerant, the lubricating properties should be tested in a mixture with the refrigerant under conditions similar to actual operation. Such an evaluation of lubricating properties is made possible by the author’s method of testing the wear of the block-on-ring friction node. The obtained rankings of lubricating properties for oils (due to the wear volume) can provide good guidelines for the suitable selection of a lubricant for refrigeration compressors (especially for new, environmentally friendly refrigerants, such as R452A). The research was carried out for mixtures of zeotropic refrigerants (R404A, R452A) with polyester oils (POE) and natural refrigerant (R600a) with mineral oils (MO). In each group of refrigerants, different mechanisms of oil–refrigerant mixture formation occur. Each refrigerant was tested with three different compressor oils recommended for each other for alternative uses in refrigeration systems

Przyczynek do wiedzy o synergii w układach tribologicznych

The article contains information about the knowledge of synergism in tribology systems. Two examples of analyses of synergism in tribology systems are presented in the article. In the first example, the interaction coefficient (synergy coefficient) was used to evaluate a set of engine and gear oils composed of special lubricating (surface-active) additives to improve the galling load – a measure of boundary layer strength, evaluated on a 4-ball apparatus. Using the interaction coefficient, a 12-element set of oils (compositions) was "separated" into three groups: synergism with additives (KS>1), sometimes strong, at KS=2, neutral interaction (KN=1), antagonism with additives (KA1), niekiedy silny, przy KS=2, współdziałanie neutralne (KN=1), antagonizm z dodatkami (KA<1). Analiza wyników badań przy pomocy współczynnika synergizmu pozwala również dobrać optymalne stężenie dodatku w oleju handlowym. W drugim z przypadków analizowano system trójczynnikowy, w którym cechą wynikową (niepożądaną) była miara zużycia mechaniczno-korozyjno-ściernego elementów metalowych. W specjalnie zaprojektowanych eksperymentach wyznaczono składowe zużycia całkowitego pochodzące od trzech czynników bazowych (mechanicznego, korozyjnego i środowiskowego) oraz od interakcji między nimi. Stwierdzono, że udział składowej sumarycznej odziaływań interakcyjnych mechaniczno-ścierno-korozyjnych wynosi od 40 do 50% zużycia całkowitego (przy 50% występuje silny synergizm KS=1)

Właściwości smarne mieszanin olejów poliestrowych z czynnikiem chłodniczym R404A w waunkach skąpego smarowania

There has been a dynamic shift towards the use of ecological refrigerants in the refrigeration industry. Currently, they must not contain fluorine and chlorine. The substances that deplete the ozone layer have already been withdrawn, and the refrigerants that increase the greenhouse effect are getting restricted. Until recently, R404A was a quite commonly used HFC refrigerant for commercial refrigeration equipment in both small and large systems. Although R404A refrigerant has considerable greenhouse effect potential, it has not been banned from use in existing refrigeration systems. The widespread use of R404A refrigerant requires appropriate compressor lubricants.In refrigeration compressors, the amount of oil in friction pairs in certain situations may be insufficient. In that event, poor lubrication conditions may occur. There may also be a situation in which the areas of friction lack lubricant and friction pairs are lubricated only by the refrigerant.The article contains a methodical selection of test parameters for polyester oils, allowing one to assess the lubricating properties of the mixtures of oils for refrigeration compressors and refrigerants under poor lubrication conditions. The article also includes the results of wear tests which allow one to evaluate the lubricating properties of oil-refrigerant mixtures under starved lubrication conditions for R404A refrigerant and polyester oils.Obecnie w chłodnictwie następuje dynamiczny zwrot w kierunku stosowania ekologicznych czynników chłodniczych. Dość powszechnie stosowanym czynnikiem chłodniczym z grupy HFC dla komercyjnych urządzeń chłodniczych zarówno w małych jak i dużych instalacjach był do niedawna R404A, co wiąże się z potrzebą doboru odpowiednich sprężarkowych środków smarnych. W sprężarkach chłodniczych może wystąpić sytuacja, w której ilość oleju w węzłach tarcia jest niewystarczająca. Wówczas mogą wystąpić skąpe warunki smarowania lub smarowanie tylko przez czynnik chłodniczy. W artykule przedstawiono metodyczny dobór parametrów badań pozwalających na ocenę właściwości smarnych olejów do sprężarek chłodniczych w mieszaninie z czynnikiem chłodniczym w warunkach skąpego smarowania dla olejów poliestrowych. Umieszczono również wyniki badań zużyciowych pozwalających na ocenę właściwości smarnych mieszanin olej – czynnik chłodniczy w warunkach skąpego smarowania uzyskanych dla czynnika chłodniczego R404A z olejami poliestrowymi

Tribocorrosion and Abrasive Wear Test of 22MnCrB5 Hot-Formed Steel

The article presents the results of research on abrasive and tribocorrosion wear of boron steel. This type of steel is used in the automotive and agricultural industries for the production of tools working in soil. The main goal of the article is the evaluation of tribocorrosion and abrasive wear for hot-formed 22MnCrB5 steel and a comparison of the obtained results with test results for steel in a cold-formed state. The spinning bowl method to determine the wear of samples working in the abrasive mass was used. Furthermore, a stand developed based on the ball-on-plate system allows to determine the wear during the interaction of friction and corrosion. After the hot-forming process, 22MnCrB5 steel was three times more resistant for the abrasive wear than steel without this treatment. The average wear intensity for 22MnCrB5 untreated steel was 0.00046 g per km, while for 22MnCrB5 hot-formed steel it was 0.00014 g per km. The tribocorrosion tests show that the wear trace of hot-formed 22MnCrB5 steel was about 7.03 &micro;m, and for cold-formed 22MnCrB5 steel a 12.11 &micro;m trace was noticed. The hot-forming method allows to obtain the desired shape of the machine element and improves the anti-wear and anti-corrosion properties for boron steel

The Influence of Surface Preparation of the Steel during the Renovation of the Car Body on Its Corrosion Resistance

The article presents the influence of the applied method used for removing the varnish coat on the corrosion resistance of the car body sheet. The tests were carried out on samples prepared from factory-painted car body elements with pearlescent, metallized and acrylic varnish. Removal of the varnish coat was performed by sandpaper grinding, glass bead blasting, disc blaze rapid stripping, soda blasting and abrasive blasting with plastic granules. The average thickness of the factory-painted coating depending on the type of lacquer ranged from about 99 to 140 µm. On the other hand, after removing the varnish, the thickness of the protective zinc coating ranged from 2 to 12.7 µm. The highest values of the zinc coating were obtained for samples in which the varnish was removed by the method such as soda blasting and abrasive blasting with plastic granules. For these two methods of surface preparation, the damage to the zinc layer protecting the steel against corrosion is the smallest and the percentage of zinc in the surface layer ranges from 58% to 78%. The final stage of the research was to test the samples after removing the varnish coat in a two-hour exposure to the corrosive environment in a salt spray chamber. Samples with the surface prepared by grinding with sandpaper reached the level of surface rusting Ri 5, while in the case of soda blasting and the use of plastic granules, no corrosion centers were observed on the surface of the car body sheet

The Analysis of Polyethylene Hip Joint Endoprostheses Strength Parameters Changes after Use inside the Human Body

The influence of dynamic loads resulting from human motor activity and electrocorrosion inside the human body on the strength parameters of artificial joint elements has not yet been investigated. Hip joint arthroplasty is the most common surgical procedure in the world that allows doctors to remove pain and restore motor skills in people with severe hip diseases, after accidents, and in the elderly. Based on the reports, this article assesses changes in the number of implanted endoprostheses in the years 2005–2019 and determines the trends and estimated changes in the number of implanted hip prostheses in the following decades. The study assesses changes in selected strength parameters of UHMW-PE polyethylene inserts of hip joint endoprostheses during their use in the human body. The research was carried out on appropriately collected samples from UHMW-PE cups removed from the human body with a known history and lifetime from 4 to 10 years. Patients’ body weight ranged from 735 [N] to 820 [N], and the declared physical activity was similar in the entire research group. As part of the research, the values of changes in dynamic modules and the mechanical loss coefficient were determined in relation to the share of the crystalline and amorphous phases of artificial UHMW-PE cups, removed from the human body after different periods of exploitation under similar operating conditions. The analysis of selected strength parameters was performed at a temperature of 40 °C, which corresponds to the working conditions inside the human body. On the basis of numerical studies, the influence of changes in material parameters on the deformation of the artificial acetabulum during the patient’s motor activity, which is one of the causes of fatigue destruction, was determined

The Analysis of Polyethylene Hip Joint Endoprostheses Strength Parameters Changes after Use inside the Human Body

The influence of dynamic loads resulting from human motor activity and electrocorrosion inside the human body on the strength parameters of artificial joint elements has not yet been investigated. Hip joint arthroplasty is the most common surgical procedure in the world that allows doctors to remove pain and restore motor skills in people with severe hip diseases, after accidents, and in the elderly. Based on the reports, this article assesses changes in the number of implanted endoprostheses in the years 2005&ndash;2019 and determines the trends and estimated changes in the number of implanted hip prostheses in the following decades. The study assesses changes in selected strength parameters of UHMW-PE polyethylene inserts of hip joint endoprostheses during their use in the human body. The research was carried out on appropriately collected samples from UHMW-PE cups removed from the human body with a known history and lifetime from 4 to 10 years. Patients&rsquo; body weight ranged from 735 [N] to 820 [N], and the declared physical activity was similar in the entire research group. As part of the research, the values of changes in dynamic modules and the mechanical loss coefficient were determined in relation to the share of the crystalline and amorphous phases of artificial UHMW-PE cups, removed from the human body after different periods of exploitation under similar operating conditions. The analysis of selected strength parameters was performed at a temperature of 40 &deg;C, which corresponds to the working conditions inside the human body. On the basis of numerical studies, the influence of changes in material parameters on the deformation of the artificial acetabulum during the patient&rsquo;s motor activity, which is one of the causes of fatigue destruction, was determined