Life ex­pectancy of a fan bear­ing, 2-3 or 10-15 years

DEMM Engineering & Manufacturing - - MAINTENANCE MATTERS -

What is the ex­pected ser­vice-life of a fan-bear­ing? At many plants fan bear­ing ser­vice life is con­sid­ered good if it is more than two years at the same time life cal­cu­la­tions nor­mally show 10 years and more! What if a fan bear­ing could ac­tu­ally last ten years plus?

The SKF fan shaft so­lu­tion will en­able you to up­grade your fan’s per­for­mance to achieve a longer life. The real road­block to fan speed and per­for­mance is ex­cess heat gen­er­ated by the bear­ings as a re­sult of speed, load, mis­align­ment, ther­mal elon­ga­tion and vi­bra­tions.

In­dus­trial fans and blow­ers also op­er­ate un­der nearly ev­ery con­di­tion with chal­lenges such as heat, dust, cor­ro­sive vapours, and wash-down which shorten their life. What all in­dus­trial fans have in com­mon is the need to op­er­ate re­li­ably for long pe­ri­ods of time. Pre­ma­ture bear­ing fail­ure is one of the most com­mon is­sues fac­ing fans re­sult­ing from lu­bri­ca­tion loss or con­tam­i­na­tion, shaft mis­align­ment, or ex­cess vi­bra­tion. Un­sched­uled down­time can be very costly with pro­duc­tion losses and emer­gency re­pairs par­tic­u­larly in the event of a cat­a­strophic fail­ure and where fans are dif­fi­cult to ac­cess.

THE MOD­ERN SELF-ALIGN­ING SO­LU­TION

Tech­nol­ogy de­vel­ops, ten years ago there was only one way to ac­com­mo­date ax­ial ex­pan­sion of the shaft: al­low the non-lo­cat­ing bear­ing to slide in the hous­ing. To­day, how­ever SKF of­fers an in­no­va­tive bear­ing sys­tem con­sist­ing of two self-align­ing bear­ings: the CARB toroidal roller bear­ing andd a spher­i­cal roller bear­ing.

The CARB bear­ing com­bines the self-align­ing prop­er­ties of the spher­i­cal roller bear­ing with the free ax­ial move­ment of a cylin­dri­cal roller bear­ing with the ad­di­tional ben­e­fit of a lower min­i­mum load rat­ing. By us­ing a CARB bear­ing in the non-lo­cat­ing po­si­tion and a spher­i­cal roller bear­ing in the lo­cat­ing po­si­tion the sys­tem ac­com­mo­dates ther­mal ex­pan­sion of the fan shaft within the CARB bear­ing vir­tu­ally with­out fric­tion. This sys­tem runs with lower fric­tion, tem­per­a­ture and vi­bra­tion lev­els, re­duces power con­sump­tion and en­ables higher fan speeds.

HOUS­INGS AND SEALS

SKF SNL, SAF and SONL hous­ings and seals are de­signed for use with SKF self-align­ing bear­ings, and are suit­able for the lo­cat­ing or non-lo­cat­ing po­si­tions. They max­i­mize ser­vice life by com­bin­ing stiff­ness, highly ac­cu­rate ma­chined sur­faces and an abil­ity to draw heat away from the bear­ing. SNL hous­ings are also avail­able with K7 bear­ing seat fit for ap­pli­ca­tions prone to vi­bra­tions and fret­ting.

SO­LU­TION BEN­E­FITS

When com­pared to the typ­i­cal self-align­ing bear­ing sys­tem, the SKF self-align­ing so­lu­tion pro­vides the fol­low­ing ben­e­fits: • Elim­i­nates the prob­lem of in­duced ax­ial loads

cre­ated by ther­mal ex­pan­sion of the shaft. • Re­duces fric­tion and vi­bra­tion lev­els. • De­creases heat gen­er­ated by the bear­ings. • Al­lows use of K7 fit hous­ings to

pre­vent fret­ting. • Re­duces power con­sump­tion for max­i­mum

pres­sure and air flow. • En­ables higher speed due to lower bear­ing tem­per­a­ture. On the global scene the to­tal shaft so­lu­tion is now be­com­ing a new in­dus­try stan­dard. Many cus­tomers are re­port­ing that they have gone from cat­a­strophic fail­ures sev­eral times a year to a sit­u­a­tion where the bear­ings are no more an is­sue and all ser­vice done is the con­di­tion mon­i­tor­ing. A pa­per mill in US changed to CARB set up in 2005 and are still run­ning with the same set of bear­ings. Swedish en­ergy pro­ducer, For­tum, in­tro­duced the to­tal shaft so­lu­tion in 2008 af­ter 2-3 yearly cat­a­strophic fail­ures. Af­ter the changeover the fan has not have one cat­a­strophic fail­ure in al­most 10 years.

In con­clu­sion most fans should never be in need for re­place­ment bear­ings at all!

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