DEMM Engineering & Manufacturing - - CONTENTS -

When SKF first launched the SKF Ex­plorer per­for­mance class in 1999, it set new stan­dards for bear­ing per­for­mance. Driven by cus­tomer needs in chal­leng­ing industrial ap­pli­ca­tions, SKF has raised the bar again to pro­vide ad­di­tional wear re­sis­tance while main­tain­ing tough­ness, to po­ten­tially dou­ble bear­ing ser­vice life – par­tic­u­larly in ap­pli­ca­tions where there are high lev­els of con­tam­i­na­tion or poor lu­bri­ca­tion con­di­tions.

By com­bin­ing ma­te­rial, de­sign and man­u­fac­tur­ing im­prove­ments, SKF en­gi­neers and sci­en­tists were able to max­i­mize the ef­fect of lu­bri­ca­tion and min­i­mize the ef­fects of fric­tion, wear and con­tam­i­na­tion. The re­sult: a per­for­mance class of bear­ings that pro­vided higher load car­ry­ing ca­pac­ity and ex­tended bear­ing ser­vice life that has been con­firmed and val­i­dated by lead­ing cer­ti­fi­ca­tion bod­ies, Ger­man­is­cher Lloyd and Det Norske Ver­i­tas.

From a ma­te­ri­als per­spec­tive, SKF Ex­plorer self-align­ing roller bear­ings were characterised by an ex­tremely clean and ho­moge­nous bear­ing steel that un­der­went a unique heat treat­ment process. The pu­rity of the steel gave SKF Ex­plorer bear­ings their ex­cep­tional strength and dura­bil­ity and the heat treat­ment cre­ated the op­ti­mal com­bi­na­tion of hard­ness and di­men­sional sta­bil­ity.

The re­sult was a highly re­li­able range of self-align­ing roller bear­ings, with low fric­tion, high load car­ry­ing ca­pac­ity and min­i­mized stresses.

Since the in­tro­duc­tion of SKF Ex­plorer spher­i­cal roller bear­ings, the SKF Ex­plorer per­for­mance class has ex­panded to in­clude other bear­ing types in­clud­ing ta­pered roller bear­ings, cylin­dri­cal roller bear­ings, deep groove ball bear­ings and an­gu­lar con­tact ball bear­ings. To­day, all stan­dard spher­i­cal roller bear­ings, CARB toroidal roller bear­ings and most spher­i­cal roller thrust bear­ings are man­u­fac­tured to SKF Ex­plorer per­for­mance class spec­i­fi­ca­tions.

Heat treat­ment adds per­for­mance

Now, SKF has fur­ther im­proved the heat treat­ment for self-align­ing roller bear­ings so that they are even more wear re­sis­tant. Though this up­graded heat treat­ment can im­prove up­time for vir­tu­ally any ap­pli­ca­tion where re­li­a­bil­ity and long ser­vice life are key op­er­a­tional pa­ram­e­ters, the benefits are most ap­par­ent in industrial ap­pli­ca­tions where there are high lev­els of con­tam­i­na­tion or poor lu­bri­ca­tion con­di­tions. Typ­i­cal ex­am­ples in­clude the met­als, min­ing, min­eral and ce­ment pro­cess­ing in­dus­tries, wind power and marine, industrial trans­mis­sion and ma­te­rial hand-ling ap­pli­ca­tions.

Val­i­da­tion testing

Val­i­da­tion testing car­ried out at cen­tres within SKF and at KTH Uni­ver­sity in Stock­holm, Swe­den, showed the im­proved wear re­sis­tance and the ser­vice life gain un­der poor lu­bri­ca­tion con­di­tions in­di­cate that th­ese bear­ings can last up to twice as long as orig­i­nal SKF Ex­plorer bear­ings. For con­tam­i­nated con­di­tions, en­durance tests sim­i­larly in­di­cate a pos­si­ble dou­bling in ser­vice life when com­pared with the orig­i­nal SKF Ex­plorer bear­ings.

Re­sults in­di­cate that medium- and lar­ge­size up­graded SKF Ex­plorer bear­ings can fur­ther ex­tend the time from ini­tial spalling to through-frac­ture. The ex­tended fail­ure mode, when part of a proac­tive main­te­nance pro­gramme, can vir­tu­ally elim­i­nate un­planned down­time. The f lange strength of up­graded SKF Ex­plorer spher­i­cal roller thrust bear­ings was tested against orig­i­nal SKF Ex­plorer bear­ings. Af­ter the f langes on the orig­i­nal SKF Ex­plorer frac­tured, the up­graded SKF Ex­plorer bear­ings ran twice as long and had only de­vel­oped spalls.

Even though bear­ings in process equip­ment are not run to through-frac­ture, th­ese tests show that once bear­ing dam­age has been de­tected, up­graded SKF Ex­plorer bear­ings con­tinue to op­er­ate longer, pro­vid­ing more time to plan, or­der parts and pre­pare for a shut­down; thereby re­duc­ing down­time and its re­lated costs.

Con­clu­sion The con­tri­bu­tion that the im­proved heat treat­ment pro­vides, to ex­tend the ser­vice life of up­graded SKF Ex­plorer self-align­ing roller bear­ings, is sig­nif­i­cantly im­proved wear-re­sis­tance, which can re­sult in up to twice the bear­ing ser­vice life un­der poor lu­bri­ca­tion or se­vere con­tam­i­na­tion con­di­tions. This opens the op­por­tu­nity for end users to in­crease equip­ment up­time in some of the harsh­est and most chal­leng­ing in­dus­tries, from wind power to met­als pro­cess­ing.

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