| | | Dynamic axial load carrying capacity Bearings manufacturer with flanges on both the inner and outer ring can support axial loads in addition to radial loads. Their axial load carrying capacity is primarily determined by the ability of the sliding surfaces of the roller end/flange contact to support loads. Factors having the greatest effect on this ability are the lubrication conditions, operating temperature and heat dissipation from the bearing. Assuming the conditions cited below, the permissible axial load can be calculated with sufficient accuracy from | | The above equation is based on conditions that are considered typical for normal bearing operation: • a difference of 60 °C between the bearing operating temperature and the ambient temperature; • a specific heat loss from the bearing of 0,5 mW/mm2 °C; with reference to the bearing outside diameter surface (it D B); • a viscosity ratio k> 2. For grease lubrication the viscosity of the base oil in the grease may be used. If k is less than 2, the friction will increase and there will be more wear. These effects can be reduced at low speeds, for example, by using oils with AW (anti-wear) and EP (extreme pressure) additives. Where axial loads act for longer periods and the bearings are grease lubricated, it is advisable to use grease that has good oil bleeding properties at the operating temperatures (> 3 % according to DIN 51 817 or IP 12175/1992). Frequent relubrication is also recommended. The values of the permissible load Fap obtained from the heat balance equation are valid for a continuously acting constant axial load and adequate lubricant supply to the roller end/flange contacts. Where axial loads act only for short periods, the values may be multiplied by 2, or for axially acting shock loads by 3. To avoid any risk of flange breakage, the constantly acting axial load Fa applied to the bearing should never exceed the numerical value of • 0,0045 D1,5 for bearings of series 2 and • 0,0023 D1,7 for bearings of other series. Where the axial load acts only occasionally and for brief periods, Fa should never be greater than the numerical value of • 0,013 D1,5 for bearings of series 2 and • 0,007 D1,7 for bearings of other series | | where Fa = the occasionally acting axial load, kN D = bearing outside diameter, mm To obtain an even flange load and provide sufficient running accuracy of the shaft when cylindrical roller bearings are subjected to heavy axial loads, axial runout and the size of the abutment surfaces of adjacent components become particularly important. As to the diameter of the abutment surfaces, SKF recommends supporting the inner ring at a height corresponding to half of the flange height fig b ). For the inner ring flange, for example, the abutment diameter can be obtained using das = 0,5 (d1 + F) where das = shaft abutment diameter, mm d1 = inner ring flange diameter, mm F = inner ring raceway diameter, mm Where misalignment between the inner and outer rings exceeds 1 minute of arc, the action of the load on the flange changes so considerably that the safety factors included in the guideline values may be inadequate. In these cases, please contact the SKF application engineering service. | | |
| | | where Fap =maximum permissible axial load, kN C0 = basic static load rating, kN Fr = actual radial bearing load, kN n = rotational speed, r/min d = bearing bore diameter, mm D = bearing outside diameter, mm k1 =a factor = 1,5 for oil lubrication = 1 for grease lubrication k2 =a factor = 0,15 for oil lubrication = 0,1 for grease lubrication | | |