Reunión con la Dra. Elizabeth Fordham, Misión de la OCDE

Table 17.1 (a) Bearing damage and corrective measures

●

Flaking

Flakes form on the surfaces of the raceway and roller elements. When the flakes fall off, the surface

becomes rough and uneven.

¡Excessive loads, fatigue

life, improper handling

¡Improper mounting ¡Insufficient precision of shaft or housing ¡Insufficient clearance ¡Contamination ¡Rust ¡Improper lubrications

¡Softening due to abnormal

temperature rise

¡Select another type of

bearing. ¡Reconsider internal clearance. ¡Improve precision of shaft or housing. ¡Improve operating conditions. ¡Improve method of

assembly and handling.

¡Check bearing periphery. ¡Reconsider lubricant and

lubrication method.

●

Seizure

Bearing heats up, becomes

discolored and eventually seizes up.

¡Insufficient clearance

(including clearances made smaller by local deformation) ¡Insufficient lubrication, improper lubricant ¡Excessive load (excessive preload) ¡Roller skew ¡Softening due to

abnormal temperature rise

¡Reconsider lubricant type

and quantity. ¡Reconsider internal clearance (enlarge internal clearance). ¡Prevent misalignment. ¡Reconsider operating conditions. ¡Improve method of

assembly and handling. Description Causes Corrective measures

17

Table 17.1 (b) Bearing damage and corrective measures

●

Meandering wear patterns

Meandering or irregular wear of raceway surface by rolling elements

¡Insufficient precision of

shaft or housing.

¡Improper mounting

¡Insufficient rigidity of shaft

and housing

¡Shaft sling due to

excessive internal clearance ¡Re-check internal clearance. ¡Reconsider machining precision of shaft or housing. ¡Reconsider rigidity of

shaft and housing.

●

Cracking and notching

Localized flaking and cracking.

¡Excessive shock load ¡Improper handling (use of

steel hammer and impact of large foreign particles)

¡Surface deformation due

to improper lubrication

¡Excessive interference ¡Large flaking

¡Friction cracks

¡Insufficient precision of

counterpart (fillet radius too large)

¡Reconsider lubricant

(prevent friction cracks).

¡Reconsider proper

interference and material.

¡Reconsider operating

conditions.

¡Improve method of

assembly and handling.

●

Cage damage

Rivets become loose or break off. Cage becomes damaged.

¡Excessive moment load ¡High-speed rotation or

excessive rotation fluctuation

¡Improper lubrication ¡Impact of foreign matter ¡Excessive vibration ¡Improper mounting

(misalignment)

¡Reconsider lubricant and

lubrication method.

¡Select a different type of

cage.

¡Investigate rigidity of shaft

and housing.

¡Reconsider operating

conditions.

¡Improve method of

assembly and handling. Description Causes Corrective measures

17

Table 17.1(c) Bearing damage and corrective measures

●

Smearing and scuffing

Surface becomes rough with small deposits. "Scuffing" generally refers to roughness of the bearing ring ribs and roller end faces.

¡Improper lubrication

¡Invasion of foreign matter ¡Roller skew due to

bearing misalignment

¡No oil on rib surface due

to excessive axial load

¡Excessive surface

roughness

¡Excessive sliding of

rolling elements

¡Reconsider lubricant

and lubrication method.

¡Improve sealing performance. ¡Reconsider preload. ¡Reconsider operating conditions. ¡Improve method of

assembly and handling.

●

Rust and corrosion

Surface becomes partially or fully rusted. Rust may also develop on rolling

element pitch lines.

¡Improper storage ¡Improper packaging ¡Insufficient rust

preventative

¡Invasion of moisture, acid,

etc.

¡Handling with bare hands

¡Take measure to prevent

rusting while in storage.

¡Inspect lubricant on

regular basis.

¡Improve sealing

performance.

¡Improve method of

assembly and handling.

●

Fretting

There are two types of fretting: the type where rust-colored wear powder forms on fitting surfaces, and the type where brinneling indentation forms on the raceway along the pitch of the rolling elements.

¡Insufficient interference ¡Small bearing oscillation

angle

¡Insufficient lubrication

(unlubricated)

¡Fluctuating load

¡Vibration during transport

or when not operating

¡Select a different type of

bearing.

¡Reconsider lubricant and

lubrication method.

¡Reconsider interference

and apply lubricant to fitting surface.

¡Package inner and outer

rings separately for transport.

17

Table 17.1(d) Bearing damage and corrective measures

●

Electrolytic corrosion

Pits form on raceway and develop into ripples.

¡Electric current flowing

through raceway

¡Create a bypass for

current.

¡Insulate the bearing.

●

Dents and scratches

Impact of solid foreign matter.

Scoring during assembly, gouges in surface due to impact.

¡Solid foreign matter ¡Dents caused by flakes ¡Impact or dropping due to

improper handling

¡Misalignment when

assembling

¡Improve method of

assembly and handling.

¡Improve sealing

performance

(to prevent foreign matter from getting inside).

¡Check bearing periphery

(when caused by metal shavings).

●

Wear

The surface becomes worn, resulting in dimension change. Wear is often

accompanied by roughness and damage.

¡Foreign matter in the

lubricant

¡Insufficient lubrication ¡Roller skew

¡Reconsider lubricant and

lubrication method.

¡Improve sealing

performance.

¡Prevent misalignment.

Decomposed

layer White layer Tempered layer

17

Table 17.1(e) Bearing damage and corrective measures

●

Creep

Surface becomes mirror finished due to slipping of the inner and outer surfaces. Sometimes accompanied by discoloration or scuffing.

¡Insufficient interference of

fitted parts

¡Insufficient sleeve

tightening

¡Abnormal temperature rise ¡Excessive load

¡Reconsider interference. ¡Reconsider operating

conditions.

¡Reconsider machining

precision of shaft and housing.

●

Surface matting

Surface luster disappears, and surface becomes matted and rough. Surface becomes covered with tiny dents.

¡Foreign matter

¡Improper lubrication

¡Reconsider lubricant and

lubrication method.

¡Improve sealing devices ¡Clean lubricating oil

(with filter)

●

Peeling

Patches of minute peeling

(approx. 10

μ

m). Accompanied by innumerable cracks that have not yet peeled.

(Tends to form on roller bearings.)

¡Foreign matter

¡Improper lubrication

¡Reconsider lubricant and

lubrication method.

¡Improve sealing

performance

(prevent foreign matter from getting in).

¡Perform warm-up

operation prior to work. Description Causes Corrective measures

17

●

Transition of NTN Technology (Introduction of "Technical Review")

NTN technology has developed along with advancements in various industries based on rolling bearings. There is practically no industry that can exist without the use of bearings, beginning with the steel industry in the postwar reconstruction period, and including railway cars, automobiles, aircraft, high-speed communications and environment-related industries. Some of these are covered inNTNTECHNICAL REVIEW (formerly "Bearing Engineer").

 Bearing Tips

 Bearing Tips Bearing Tips

One-Point Advice  No. 60 January, 1992 Precision bearings Inaugural Issue October, 1950 No. 10 December, 1954 No. 20 December, 1959 High-speed bearings No. 29 December, 1964 No. 42 May, 1972 Aircraft bearings No. 50 October, 1984 No. 61 June, 1992 Automobile bearings/parts No. 62 March, 1993 Industrial machine bearings No. 64 June, 1995

Precision devices and products No. 63 June, 1994 New materials /  surface improvement No. 65 October, 1996 Automobile products No. 66 August, 1997

In document ACTA DE LA SESION EXTRAORDINARIA (página 169-173)