CARBÂ® toroidal roller bearings â a revolutionary ... - Acorn Bearings

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1 Product information 2 Recommendations 3 Product data Page ............. 3 Grease lubrication Page ............. 37 Lubrication CARB toroidal roller bearings can be lubricated with grease as well as oil. There is no strict rule for when grease or oil should be used. Grease has the advantage over oil that it is more easily retained in the bearing than oil and grease is better if the shaft is at an angle or arranged vertically. On the other hand, oil lubrication allows higher operating speeds and temperatures and can contribute to heat removal from the bearing position, which is particularly important where external heating is involved. Very small quantities of lubricant are required to lubricate the bearing surfaces. Since CARB toroidal roller bearings cannot be relubricated via the outer ring, lubricant has to be supplied from the side of the bearing. This is best done via a duct that opens immediately adjacent to the side face of the bearing outer ring. To force the lubricant to pass through the bearing, a drainage opening should be provided on the opposite side of the bearing (➔ fig 1 ). Grease lubrication For the lubrication of CARB toroidal roller bearings good quality rust inhibiting greases that are resistant to ageing and have a consistency of 2 or 3 are suitable. Many factors influence the choice of grease. To assist in this process, SKF greases that are suitable for CARB bearing lubrication are listed in table 1 . Lubricant supply to the bearing Operating conditions Fig 1 The correct quantity of grease For the majority of applications the following guidelines apply: • Caged CARB toroidal roller bearings should be filled with grease to approximately 50 %. In bearings that are to be greased before mounting it is recommended just to fill the space between the inner ring and the cage (➔ fig 2 ). • The free space in the bearing housing should be filled with grease to between 30 and 50 %. • Full complement CARB toroidal roller bearings should be completely filled with grease. For bearing arrangements that turn slowly but where good protection against corrosion is required, all the free space in the housing can be filled with grease as there is little risk of the operating temperature increasing. SKF grease Designation Temperature Viscosity at range 40/100 ˚C – – ˚C mm 2 /s Standard bearing LGMT 2 –30/+120 110/11 arrangements Standard bearing arrange- LGMT 3 –30/+120 125/12 ments but with relatively high ambient temperatures Operating temperatures LGHB 2 –20/+150 420/26,5 always over 100 ˚C High operating temperatures, LGHP 2 –40/+150 96/10,5 smooth operation Table 1 Shock loads, heavy loads, LGEP 2 –20/+110 200/16 vibration High demands on LGGB 2 –40/+120 110/13 environmental friendliness Recommended SKF greases Full details on the mentioned SKF greases as well as the complete range of SKF greases will be found in – SKF catalogue MP3000 “SKF Maintenance and Lubrication Products” or online at www.mapro.skf.com – “SKF Interactive Engineering Catalogue” on CD-ROM or online at www.skf.com 22
1 Product information 2 Recommendations 3 Product data Page ............. 3 Grease lubrication Page ............. 37 Table 2 Fig 2 Bearing design Bearing Maximum n × d m factor C/P ≥ 15 C/P ≈ 8 C/P ≈ 4 CARB bearings with cage 2 350 000 200 000 100 000 CARB bearings – full complement 1) 4 N.A 3) N.A 3) 20 000 2) 1) The t f value obtained from diagram 1 needs to be divided by a factor 10 2) For higher speeds oil lubrication is recommended 3) For these C/P values a caged bearing is recommended instead 2 Bearing factors and recommended maximum speed limits Relubrication CARB toroidal roller bearings have to be relubricated if the service life of the grease is shorter than the expected service life of the bearing. Relubrication should always be undertaken at a time when the existing lubricant is still satisfactory. The time at which relubrication should be undertaken depends on many related factors. These include bearing type and size, speed, operating temperature, grease type, space around the bearing and the bearing environment. It is only possible to base recommendations on statistical rules; the SKF relubrication intervals are defined as the time period, at the end of which 99 % of the bearings are still reliably lubricated. This represents L 1 for grease life. SKF recommends using experience data from running applications and tests, together with the estimated relubrication intervals provided in the next section. Relubrication intervals (t f ) The relubrication intervals t f for normal operating conditions are provided in diagram 1 . The diagram is valid for bearings on horizontal shafts under clean conditions. The value on the horizontal axis is obtained from “n × d m ” (rotational speed × bearing mean diameter) (unit: mm/min) multiplied by the relevant CARB toroidal roller bearing factor, which depends on the applied CARB toroidal roller bearing execution and loading situation. The bearing factor and recommended maximum “n × d m ” values for CARB toroidal roller bearings are given in table 2 . The t f value is then derived considering the load magnitude, given by the value of C/P. The relubrication interval (t f ) is an estimated value, valid for an operating temperature of 70 °C, using good quality lithium base greases. Different conditions are covered in detail in “Deviating conditions”. If the value of “n × d m ” approaches the limit value (> 70 %) or if ambient temperatures are high, then the use of Relubrication intervals for CARB toroidal roller bearings at 70 °C tf, operating hours 100 000 50 000 10 000 5 000 1 000 500 100 0 Bearing grease fill Caged CARB toroidal roller bearings should not be completely filled with grease; for high speed operation fill only the space between the inner ring and the cage the calculations presented in the SKF General Catalogue, section “Speeds and vibration”, is recommended to check the operating temperature and the proper lubrication method. Diagram 100 000 200 000 300 000 400 000 500 000 600 000 700 000 800 000 Bearing factor n × d m C/P ≥ 15 C/P ≈ 8 C/P ≈ 4 Example: CARB toroidal roller bearing C 2220 K The bearing has a bore diameter d = 100 mm, an outside diameter D = 180 mm and rotates at a speed n = 1 000 r/min. The load ratio C/P is 4 and the operating temperature lies between 60 and 70 °C. What is the relubrication interval? The bearing factor n × d m is obtained as follows: n × d m = 1 000 × 0,5 (d + D) = 1 000 × 0,5 (100 + 180) = 140 000. Follow a vertical line from the x-axis from the point n × d m = 140 000 until it intersects the line of the load ratio C/P = 4. The relubrication interval can then be read off on the y-axis by drawing a horizontal line from the point of intersection with 3 000 operating hours. 1 23
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CARBÂ® toroidal roller bearings â a revolutionary ... - Acorn Bearings