Bearing Speed Factor
Calculate a bearing's speed factor, A = n·d_m, from the rotation n (rpm) and the bearing mean diameter d_m (mm, = (D + d)/2, the average of outer and inner diameters). The n·d_m factor (often in mm·rpm, or m/min times the perimeter) is the key indicator of a bearing's SPEED DUTY, and governs several application limits. It sets the operating LIMIT SPEED: each bearing (and each lubrication type) has a maximum n·d_m above which friction heating, centrifugal force on the rolling elements and dynamic effects make operation unfeasible — grease lubrication tolerates lower values, oil higher, and special systems (oil jet, mist) the highest (high-speed bearings, like turbine and machine-tool spindle bearings, reach n·d_m in the millions). The speed factor also influences the bearing type choice (balls take more speed than rollers), the lubricant and the internal clearance (fast bearings may need larger clearance to accommodate thermal expansion). Comparing the application's n·d_m with the bearing limit is an essential check in medium- and high-speed rotating machines. Enter the rotation and the mean diameter.
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Fator de velocidade (rolamento)
O fator de velocidade de um rolamento é A = n·d_m, a partir da rotação n e do diâmetro médio do rolamento d_m (= (D + d)/2). O fator n·d_m (em mm·rpm) é o indicador-chave da solicitação de velocidade de um rolamento, e governa vários limites de aplicação. Ele determina a velocidade limite de operação: cada rolamento (e cada tipo de lubrificação) tem um valor máximo de n·d_m acima do qual o aquecimento por atrito, a força centrífuga nos corpos rolantes e os efeitos dinâmicos tornam a operação inviável — lubrificação a graxa suporta valores menores, a óleo maiores, e sistemas especiais (jato de óleo, névoa) os mais altos (rolamentos de alta velocidade, como de turbinas e fusos de máquinas-ferramenta, atingem n·d_m de milhões). O fator de velocidade também influencia a escolha do tipo de rolamento (esferas suportam mais velocidade que rolos), do lubrificante e da folga interna (rolamentos rápidos podem precisar de folga maior para acomodar a dilatação térmica). Comparar o n·d_m da aplicação com o limite do rolamento é uma verificação essencial em máquinas rotativas de média e alta velocidade. Informe a rotação e o diâmetro médio.
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Static Safety Factor (Bearing)
Calculate a bearing's static safety factor, s_0 = C_0 ÷ P_0, from the static load rating C_0 (N, tabulated by the maker) and the equivalent static load P_0 (N). The static safety factor compares the bearing's ability to resist PERMANENT DEFORMATION (race indentation) with the equivalent static load it actually carries. The static rating C_0 is, by definition, the load causing a total permanent deformation of 0.0001 of the rolling-element diameter at the most-loaded contact — a small value, taken as the acceptable limit (above it, the marks cause noise and vibration when turning). The factor s_0 shows the margin: codes and makers recommend MINIMUM s_0 values per application and smoothness requirements — typically s_0 ≥ 1-1.5 for normal, quiet operation, possibly lower (0.5-1) for low-speed, undemanding applications, and higher (≥2-3) for heavy shocks or high precision. This check is COMPLEMENTARY to the life (fatigue) check: a bearing may have ample L10 life but fail by static deformation under a peak overload if s_0 is insufficient. Both checks — dynamic (life) and static (s_0) — must be met. Enter the static rating and the equivalent static load.
Reliability-Adjusted Life (Bearing)
Calculate a bearing's adjusted life for a reliability other than 90%, L_na = a_1·L10, from the reliability factor a_1 (dimensionless) and the nominal life L10 (in millions of revolutions). The standard L10 life corresponds to 90% reliability (10% failures). But many CRITICAL applications — where a bearing failure is unacceptable (turbines, aerospace, medical equipment, continuous-process machines) — require HIGHER reliabilities (95%, 99%, 99.9%). Since demanding higher reliability means accepting FEWER failures, the corresponding life is SHORTER: a_1 is below 1 for reliabilities above 90%. Typical values: a_1 = 1.0 for 90% (L10), 0.64 for 95% (L5), 0.21 for 99% (L1), 0.093 for 99.9% (L0.1). For example, to ensure 99% of bearings survive (instead of 90%), the design life drops to about 21% of L10. This is one of the 'modified life' corrections in the standards (ISO 281), which also include factors for material and lubricant quality and contamination (the more sophisticated a_ISO factor). Adjusting life for required reliability is essential in critical designs: simply using L10 (90%) would be too risky for a turbine, and too conservative for a household fan. Enter the reliability factor and the L10 life.
Bearing PV Factor
Calculate the PV factor of a bearing or self-lubricating bushing, PV = P × V, multiplying the specific pressure P (load over projected area) by the sliding velocity V at the surface. The result, in MPa·m/s, is the limiting criterion for selecting materials for non-force-lubricated bearings (sintered bronze bushings, polymers like PTFE and nylon): each material has a maximum allowable PV value, above which the friction heat cannot be dissipated and the bearing fails by melting or accelerated wear. PV is kept below the material limit with a safety margin. Enter the specific pressure and the velocity.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.