This paper investigates the aging performance of two types of insulating mineral oils through accelerated aging experiments. One of the investigated insulating mineral oils was a naphthenic type, ...inhibited, commonly used by industry, and the other oil was a paraffinic type, also inhibited, obtained from a Brazilian company by the hydro-treating technology, here called "test oil". Both oils were aged under the same conditions, in the presence of oxygen and metallic copper at 130 °C. During the experiment, aging stage of oils was assessed through different measurements including acidity, sludge content, power factor and oxidation induction time. The results showed that the aging behavior of both oils was similar. Nevertheless, the color of the hydro-treated oil changed more slowly than that the naphthenic oil and the oxidation induction time was slightly higher. The observed performance indicates that the Brazilian paraffinic oil can be used without restriction in electrical transformers.
Compositional changes of hydrotreated naphthenic oil during ultraviolet (UV) radiation were studied in detail. First, liquid-solid chromatography was used to separate the initial oil and the ...UV-irradiated oil into three different fractions: saturates, aromatics, and polars. Then, each fraction's compositional changes were evaluated using a series of instrument technologies including gas chromatography-mass spectroscopy (GC-MS), infrared spectroscopy (IR), atmospheric pressure chemical ionization mass spectroscopy (APCI/MS), and X-ray photo electron spectroscopy (XPS), respectively. The results show that after UV radiation, the UV-irradiated sample exhibited a decrease in saturates concomitant with an increase in the aromatic and polar fractions. For saturates and aromatics, the UV-irradiated sample exhibited a decrease in alkanes, diaromatics, and polyaromatics concomitant with an increase in other aromatics. The UV light had no significant effect on the cycloalkanes. For polars, a relatively large amount of oxygen-containing compounds, such as hydroxyl, carbonyl, and carboxyl groups, was formed in the presence of UV light. XPS data show that a type of S 2pa compound in the initial oil disappears and could be converted to SO
4
2−
. No obvious changes of molecular weight distribution were observed. A part of polar compounds in the UV-irradiated oil might come from aromatic photooxidation in the initial oil.
Mineral oils used by grease manufacturers can be divided into two major groups, naphthenic oils and paraffinic oils. These categories of base oils have their own advantages and disadvantages ...depending on the applications and conditions. The most important advantages of the naphthenic oils over the paraffinic oils, with the same viscosity and similar aromatic content, are better low-temperature flowability and better solvency. The contribution of having base oils with good solvency towards the thickener is that less thickener is needed to obtain a certain consistency of the finished product. For instance, a typical NLGI grade 2 lithium based grease, based on a solvent neutral 500, group one (Gr I) oil, may contain 9-14 wt% thickener; while 6-8% thickener is required for an equivalent viscosity oil of naphthenic nature. Using blends of naphthenic oil and paraffinic group one oil have successfully been used during the past decade in India. However, the author believes that the surplus of paraffinic Gr II and Gr III base oils is one among a number of market trends that brings some great opportunities to the grease formulators, if they look for blends where naphthenic oils are regarded as part of the solution for a sustainable formulation. A number of key parameters important for the performance of the finished product could be obtained within reasonable cost.
The purpose of this work was to compare “side by side” three base oil blends where paraffinic Gr I, Gr II and Gr III, in combination with naphthenic, were used for preparation of lubricating greases. Since the target viscosity was 150 mm2/s at 40ºC, a naphthenic oil was used in order to reach this viscosity.
The overall results obtained, reveal some interesting aspects of the use of Gr II as a substitute to Gr I for preparation of greases. The outcome of this work emphasizes that blends should be regarded as a great opportunity for grease formulators who are looking for some further development of their current formulations and furthermore, the lubricating grease based on the blend of paraffinic Gr II and naphthenic oil performs better than others.
Heavy fractions (boiling point 450°C or higher) derived from alkylation products, alkyl benzenes and styrenes, (Fig. 1, Table 1), were cracked by the following two methods: Case 1: thermally ...hydrocracked in the presence of tetralin Case 2: catalytically hydrocracked on N-diatomaceous earth catalyst The cracked products were, then, nuclear-hydrogenated by Rh-C catalyst at same reaction conditions (Figs. 2, 3). Gas chromatograms of the cracked products show that the compounds produced by the two methods, respectively, remarkably different (Fig. 5). Structural parameters of the products from the two methods show that side chains are cleft but aromatic rings remain unchained during the cracking stage of Case 1 (Table 2, Fig. 6). Ring-hydrogenations of the cracked products differ greatly between the two cases as follows; (1) Hydrogen consumption during the nuclear-hydrogenation of the cracked products Case 1:5.62wt%/feed Case 2:2.06wt%/feed (2) H/C (atomic ratio) of the nuclear-hydrogenated products Case 1:1.56 Case 2:1.42 (Table 3) To go into more in details, saturates and aromatics were separated from the nuclear-hydrogenated products and analyzed. Significant results follows; (1) Yields of saturates and aromatics Case 1: saturates 85.5wt% aromatics 14.5% Case 2: saturates 18.3wt% aromatics 81.7% (2) Fraction of aromatic carbons in aromatics Case 1:0.35 Case 2:0.43 (3) Ha/H in aromatics (Table 4) Case 1:0.051 Case 2:0.148 Results of gas chromatograms of saturates and aromatics from the two cases follow Case 1: Compounds containing two aromatic rings are entirely converted to saturates and greater parts of the compounds containing three aromatic rings are also converted to saturates. Case 2: Compounds containing two aromatic rings remained and compound containing three aromatic rings were not converted to saturates. (Fig. 7) From these facts, the conclusions arrived are as follows; (1) Thermally cracked products can be easily nuclear hydrogenated. (2) The differences between the cases are remarkable in heavier fractions. The nuclear-hydrogenated products derived in Case 1 were evaluated as a traction fluid, as follows; (1) Traction coefficient of the fractions are fairly good (0.080-0.087) (2) The extent of nuclear-hydrogenation is over 90% (350°C lower fractions) (Tables 5, 6) It was confirmed that a Ru-C catalyst exhibited performances which were as good as those of Rh-C catalyst (Table 7) These data suggest that naphthenic oils can be produced from other heavy alkyl-aromatics.
Naphthenic crudes regularly used to manufacture insulating oils are rapidly being depleted. More plentiful paraffinic crudes should be substituted to supply the world's future needs for electrical ...equipment. Research on paraffinic insulating olis has been conducted throughout the world, although such oils have seen only in the smaller service in Canada, Europe, Japan and few other countries. However, not so much information has been developed about the suitability of paraffinic insulating oils containing pour point depressants in modern high voltage transformers. Recent trends in power transformer design increase in both capacity and voltage with a reduction in overall size. These increased requirements for higher reliable insulation of power transformers urge the need to improve the quality of insulating oils. For example, the currently limited oxidation characteristics of oil need be more stable, to suppress the static electrification of oil caused by oil flow. This study was undertaken in an attempt to evaluate the effect of transformer oils on the degradation of paper. Further, the tendencies of gas evolution of oils under degradation and high electric stress are also studied. Additionally, dielectric tests of model insulation systems were studied. Three paraffinic oils shown in Table 1, were examined. Two commercially available pour point depressants, one-an alkylated polystyrene, the other-ethylene propylene copolymer were used. As a comparative oil, a blend of naphthenic oil and alkylbenzene was used. There appeared to be little difference among types and amounts of combustible gases produced from either a paraffinic or a naphthenic oil when tested by high voltage oil gap tests or thermal degradations (Table 3, Figs. 9 and 10). In other studies, such as dielectric tests of papers and model insulation systems, there are essentially no differences in charging tendency for the two types of oils tested under the degradation test (Figs. 12-18, Tables 4-8). It was concluded that it might be possible to replace naphthenic oils with paraffinic oils for large power transformers in future.
In the past, electrical insulating oils for transformers and associated electrical equipment have been manufactured from naphthenic crude oils. The availability of naphthenic oils, however has ...declined in recent years. In this situation, Middle East crude oils which occur in much greater quantities, they are promising source of future insulating oils. Unfortunately, non-naphthenic oils from Middle East crudes (paraffinic oils) have higher pour points than those of naphthenic oils due to their higher wax contents. Thus, a study of low temperature characteristics was carried out on straight paraiinic oils as well as on the same oils to which pour point depressants had been added. A series of tests were developed to evaluate oxidation stability, copper corrosion and hydrogen gas absorption. Sample oils having different composition were prepared. These tests were prepared by altering the refining conditions of the oils. The sulfur content of parafinic oil closely correlated with the oxidation stability (Fig. 3) and copper corrosion (Fig. 6). The amount of aromatics in paraflinic oil had greater effects on the oxidation stability (Fig. 4) and hydrogen gas absorbing ability (Fig. 7). Blends of alkylbenzene and paraffinic oils were also investigated, as shown in Figs. 5 and 7. In conclusion, paraffinic oils refined to contain approximately 20% of aromatics and 0.1 to 0.3wt% of sulfur to which 30vol% of alkylbenzene had been added showed excellent anti-corona, anti-corrosion, oxidation, and electrical properties.
To evaluate the long term service characteristics of non-naphthenic transformer oils from Middle East Crudes (paraffinic oils), accelerated tests in 10kVA distribution transformers were carried out. ...The aging tests were carried out at oil temperature of 105°C for 20 months to compare the performance among naphthenic and paraffinic oils. Three paraffinic oils were examined, as shown in Table 1. Also, two naphthenic oils are shown, which were adopted for the sake of comparision. Periodically, electrical tests were performed on the transformers and oil samples were analyzed. The results of these tests were compared with changes found in laboratory oxidation tests. No appreciable difference in the behavior of the transformers and the changes in oil quality during aging was noted in the accelerated tests of distribution transformers among the five oils tested (Figs. 2-5). The pour point of EPC-containing oil was not altered by the aging process used here. The change of electrical properties during aging tests in small distribution transformers showed the same tendencies with those of laboratory stability tests in milder oxidation conditions (Table 3). In conclusion, paraffinic insulating oils containing an appropriate pour point depressant and alkylbenzene, were confirmed to be suitable alternative for naphthenic insulating oils currently on the market.
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