SEAL
EALS & BEAR
EAR INGS
FEA
FEAT R E ATURE
Bearing failu re in ele ctricmotors THE FIVE MOS
MOST COMMON C , MMON CAUSES AND WHAT YOU CAN DO ABOUT THEM
ANDWHAT YOU CAN DO ABOUT THEM F
or industries reliant on machinery driven by electric motor s, bearing failure can be a major source of downtime and expense. Phi l Burge, fro m FKS offers advice – based on decades of co-operation with motor manufacturers and users – to maximise bearing service life.
Each of the five key factors identified has characteristic forms of damage and leaves its own special imprint on the bearing. In the event of bearing failure you can read these signs to determine the root cause of the damage and then take steps to prevent its recurrence. Better still by addressing the main issues in advanc e you can avoid problems in the firs t place.
, 1. Electri al erosi 1. Electrical erosion
Electrical erosion results from current arcing from one bearing ring to the other through the rolling elements in the bearing. Typical effects include pitting on bearing surfaces and in raceways, as well as rapid lubricant degradation and a shortened life for the bearing. The severity of the damage depends on the arc current’s energy and duration.
A cost-effective solution is to use specially developed bearings in which one of the rings has an insulating ceramic coating, such as INSOCOAT bearings fromSKF. For even greater electrical insulation, hybrid bearings are availabl bearing rings engineered frombearing-grade steel, with rolli froma high-insulation, bearing-grade, silicon nitride cerami c material.
ng elements produced e. These incorporate
2. Inadequate or contaminated lubrication A lubricant film of the required thickness and viscosity must be maintained to prevent damaging metal-to-metal contact and protect against corrosion. Contaminants entering the bearing through damaged seals or incorrect installation will degrade the lubricant and, in the case of
2. adequate or contam ated l bri ati 3. Vibrati n damage 3. Vibration damage
particulates, directly produce frictional damage. Seals should be checked for effectiveness, and if contamination cannot be avoided the lubricant should be renewed more Follow the manufacture
grease or oil grade selection, quantity and relubrication interval, or refer to bearing
manufacturers’ tables and formulae. These choices will depend on factors including operating temperature and speed, load, contamination potential and exposure to severe vibration or shock .
4. Improper installation and set-uption and set-up 4. proper i stal
Bearings will suffer mechanical damage if they are incorrectly mounted, or if they are handled without due care prior to, or during, installation. The first step is to ensure the area is free of contaminants before starting the installation. Keep the bearings in their protective packaging until the moment you mount them.
tools can be obtained for coldmounting, while for hot mounting – which is uired by larger bearings – you should seek appropriate heating equipment. Do mmer or other hard object to force a bearing or housing into place, nor shoul d g force be applied through the rolling elements .
5. Insufficient bearing load suf ent bearing l ad less they are preloaded, bearings must always be sub bjjected to aminimum
ad if they are to performwell. Light loads can lead to skidding of the rolling ments, which produces smearing damage on themand their raceways. This ue is particularly important in the case of cylindrical roller bearings as these nd to be used for the heaviest loads. Bearings operating at high speeds, or with pid accelerations or changes in load direction, also need special consideration. ormulae for calculating the required minimum load can be found in technical ides, or requested from bearing manufacturers. The minimum load may have be increased when starting up at low temperatures.
,
www.skf.com T: 01582 490049
skf.com / FACTORYEQUIPMENT FACTORYEQUIPMENT FACTOR ORY EQUIPME QUIPMENT | OCTOBE OC BER 201 2017 23 23
At set-up, bearing components are precision-engineered with sub-micron levels of fit- tolerance. Through prolonged use, especially at rapid rotation speeds and under high stress, wearmay alter their shape and dimensions – creating deviations fromthe initial fit. Poor lubrication, or operation of bearings outside their original specification, will speed up wear rates. Use of conditionmonitoring equipment including a vibration analyser is essential to early identification of these problems.
, ,
r’s recommendations on frequently.
A related issue is that transporting amotor can damage its shaft, resulting in displacement of the bearing and, consequently, introduction of vibration. Before transpo axially with a U-shaped piece of flat steel and preload the ball bearing at t Then, using a strap, load the bearing r adially at its drive end .
he non-drive end . rt, lock the shaft
SKF,
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200 |
Page 201 |
Page 202 |
Page 203 |
Page 204 |
Page 205 |
Page 206 |
Page 207 |
Page 208 |
Page 209 |
Page 210 |
Page 211 |
Page 212 |
Page 213 |
Page 214 |
Page 215 |
Page 216 |
Page 217 |
Page 218 |
Page 219 |
Page 220 |
Page 221 |
Page 222 |
Page 223 |
Page 224 |
Page 225 |
Page 226 |
Page 227 |
Page 228 |
Page 229 |
Page 230 |
Page 231 |
Page 232 |
Page 233 |
Page 234 |
Page 235 |
Page 236 |
Page 237 |
Page 238 |
Page 239 |
Page 240 |
Page 241 |
Page 242 |
Page 243 |
Page 244 |
Page 245 |
Page 246 |
Page 247 |
Page 248 |
Page 249 |
Page 250 |
Page 251 |
Page 252 |
Page 253 |
Page 254 |
Page 255 |
Page 256 |
Page 257 |
Page 258 |
Page 259 |
Page 260 |
Page 261 |
Page 262 |
Page 263 |
Page 264 |
Page 265 |
Page 266 |
Page 267 |
Page 268 |
Page 269 |
Page 270 |
Page 271 |
Page 272 |
Page 273 |
Page 274 |
Page 275 |
Page 276 |
Page 277 |
Page 278 |
Page 279 |
Page 280 |
Page 281 |
Page 282 |
Page 283 |
Page 284 |
Page 285 |
Page 286 |
Page 287 |
Page 288 |
Page 289 |
Page 290 |
Page 291 |
Page 292 |
Page 293 |
Page 294 |
Page 295 |
Page 296 |
Page 297 |
Page 298 |
Page 299 |
Page 300 |
Page 301 |
Page 302 |
Page 303 |
Page 304 |
Page 305 |
Page 306 |
Page 307 |
Page 308 |
Page 309 |
Page 310 |
Page 311 |
Page 312 |
Page 313 |
Page 314 |
Page 315 |
Page 316 |
Page 317 |
Page 318 |
Page 319 |
Page 320 |
Page 321 |
Page 322 |
Page 323 |
Page 324 |
Page 325 |
Page 326 |
Page 327 |
Page 328 |
Page 329 |
Page 330 |
Page 331 |
Page 332 |
Page 333 |
Page 334 |
Page 335 |
Page 336 |
Page 337 |
Page 338 |
Page 339 |
Page 340
