Greičio koeficientas yra terminas, kuris padeda apibrėžti greičio, kuriuo sukasi guolis, santykį su guolio dydžiu. Yra du pagrindiniai šio faktoriaus apskaičiavimo būdai. Pirmasis yra žinomas kaip DN vertė, kuriai naudojamas guolio vidinis skersmuo, padaugintas iš greičio, kuriuo jis sukasi. Antrasis metodas yra žinomas kaip NDm vertė. Norėdami apskaičiuoti greičio koeficientą, naudojamas vidutinis guolio dydis, dar vadinamas žingsnio skersmeniu, ir sukimosi greitis.
Rūšis |
Darbinės temperatūros, ºC |
Lašėjimo temperatūra, ºC |
Pagrindas |
Panaudojimas, savybės |
Molyduval Supravit LM 2PMV |
-30 iki +150 |
190 |
mineral Li |
Didelių greičių riedėjimo ir slydimo guolių NLGI 2 tepalas.Prailginti tepimo intervalai (net amžino sandarinimo sutepimui). Ypač tinka esant įrangos vibracijai, pulsacijai, svyravimams. Slopina triukšmą net prie didžiausių apsukų. Gelsvas. KP2K-30 Senuoju Supravit 52 LM pavadinimu |
Molyduval Supravit 14 CM |
-50 iki +105 |
150 |
Min Ca |
Ypač vandens nuplovimui atsparus aukštasūkis tepalas kalcio tirštiklio pagrindu. K2G-50; ISO-L-XEBHA 2. Rusvas. |
Molyduval Supravit 55 LM |
-55 iki +110 |
190 |
mineral Li |
Žematemperatūrinis, ypač nuplovimui šaltu ar karštu vandeniu atsparus NLGI 2 tepalas greitaeigiams riedėjimo ir slydimo guoliams, reduktoriams, mažiems varikliukams, instrumentams. Gelsvas. KP2G-50 |
Molylub Fett MTS 2 |
-50 iki +150 |
190 |
mineral/PAO Li |
Pusiau sintetinis, vandeniui atsparus tepalas su aukšto slydimo frikcijos komponentu greitaeigiams riedėjimo ir slydimo guoliams, dirbantiems tiek aukštose, tiek žemose temperatūrose. K2N-50; ISO-L-XEDHA2 |
-60 iki +240 |
200 |
sintet PAO Li |
Sintetinis, antifrikcinis, žemo klampumo PAO bazinės alyvos pagrindo tepalas apkrautiems greitaeigiams riedėjimo ir slydimo guoliams. Ilgaamžis, atsparus nuplovimui, gera antikorozinė apsauga. Ypač elektros variklių ir medienos pramonės staklių guoliams. Kreminis. KPHC2N-60; ISO-L-XEDIB2 |
|
-54 iki +150 |
190 |
sintet Ester |
Sintetinis, ekstremalių svyruojančių temperatūrų aplinkoje dirbančių sunkiai apkrautų greitaeigių guolių ir pavarų tepalas. Baltas. KEP2G-54 |
|
Molyduval Supravit LE 2M |
-60 iki +140 |
190 |
sintet Ester+ MoS2 |
Sintetinis, antifrikcinis, aukštų slėgių ir smūginių apkrovų veikiamų greitaeigių guolių bei dantračių tepalas su molibdeno disulfidu. Juodas. KPFE2K-60; ISO-L-XECEB2 |
-54 iki +150 |
190 |
Min+ PTFE |
Minkštesnė NLGI 1 konsistencija. |
MOLYDUVAL Supravit 52 LM yra glotnus, triukšmą slopinantis, didelių greičių riedėjimo ir slydimo guolių tepalas. Sukurtas žemo klampumo nešančiojo skysčio pagrindu jis idealiai tinka didelėms apsukoms. Sudėtyje inkorporuoti antikoroziniai priedai, kurie užtikrina papildomą apsaugą nuo rūdžių, esant drėgmės ar purvo patekimui į tepimo kanalus. Specialūs AW priedai ir kietieji baltieji tepikliai savo ruožtu saugo nuo dėvėjimosi bei mažina trintį.
MOLYDUVAL Supravit 52 LM lengvai tepamas siurbliu, sudėtyje neturi triukšmą guoliuose galinčių kelti dalelių. Todėl guoliai dirba tyliau ir tepalas gali būti naudojamas tiksliesiems prietaisams.
Choosing a High-speed Grease
Wes Cash, Noria Corporation
Most industrial facilities have bearings that rotate faster than normal processing equipment. When it comes to lubricating these pieces of equipment, not all lubricants behave the same way.
For grease-lubricated components, the effects of the grease on the bearings can lead to increased heat, drag and ultimately premature failure. By properly selecting a grease that can handle these higher speeds, you can help minimize any potential failures caused by mismatching the lubricant to the application.
High-speed Applications
During my frequent plant visits, I often am asked about the temperature at which bearings should operate. Inevitably, the bearings that seem to be running the hottest are the ones that rotate the fastest. For example, on a recent trip, I inspected an overhanging fan. This fan was belt-driven at a 1-to-1 ratio from a large electric motor.
The speed of the motor was set at 1,750 revolutions per minute (rpm). Since there was no reduction or increase in pulley size, it is safe to assume the speed of the bearings was quite similar. These bearings were greased with a product that was much too thick for them, leading to the generation of excess heat and shortening the bearing life. By matching the grease properties more closely to the bearing needs, you can help prolong the life of the bearing.
While this example paints a picture of a type of machine in most plants (fans), it is common to find high-speed applications in other components as well. For instance, some pumps that are directly coupled to a motor and have grease-lubricated bearings may spin in excess of 2,000 rpm.
The same holds true for certain mixers, agitators and blowers. These components may suffer if a multi-purpose grease is simply applied without much regard to the needs of the bearing. To understand what the bearing requires in terms of lubrication, you must first learn how to determine the speed factor of a bearing.
Calculating the Speed Factor
The speed factor is a term that helps define the relationship of the speed at which a bearing rotates with the size of the bearing. There are two main ways to calculate this factor. The first is known as the DN value, which uses the bearing inner diameter multiplied by the speed at which it rotates. The second method is known as the NDm value. This uses the bearing’s median size, also known as the pitch diameter, and the rotation speed to calculate the speed factor.
The speed factor can help you determine a variety of lubricant properties, which you can then utilize to select the proper lubricant. Among these properties would be the viscosity of the oil and the National Lubricating Grease Institute (NLGI) grade of the grease for the application.
Viscosity
The most important physical property of a lubricant is the viscosity. Viscosity is what determines how thick or thin the lubricating film will be based upon the load, speed and surfaces in contact. This must be matched to the needs of the bearing. Most general-purpose greases have a base oil viscosity of around 220 centistokes. While this type of grease may work fine for moderate speeds and loads, when the bearing speed increases, the viscosity must be reduced accordingly.
There are many ways to calculate viscosity. By utilizing the speed factor mentioned earlier, you can use standardized charts to identify an appropriate viscosity for the bearing at the operating temperature. In the previous example of the fan bearing, the NDm value of the bearing was 293,125, which led to a base oil viscosity of approximately 7 centistokes. The bearing was operating at around 150 degrees F.
With a standard viscosity index of 95, this equates to an ISO 22-32 base oil viscosity. If you were to use a standard multi-purpose grease, this bearing would receive about 10 times the viscosity needed. Although some excess viscosity isn’t necessarily a bad thing, this level would be a bit extreme.
Excessive viscosity can lead to excess heat generation and increased energy consumption. Both of these are detrimental to the health of the bearing and the lubricant. The hotter the bearing runs, the lower the viscosity of the grease becomes.