Damage Examples

Below are examples of electric discharge damage

D10000 – Damage to tilt-shoe bearing by short-circuited homopolar-generation loop within bearing.

D10001 – Thrust shoe severely damaged by currents (frosted area). The wedge-shaped area at leading edge (right) is the only remaining original surface. At the white triangle at trailing edge, outside diameter, the babbitt is completely gone and spark erosion has progressed into the steel backing. Metal lost at this point is 0.085″. The dark area is oil cake. Bearing was close to failure.

D10002 – Surface of thrust bearing shoe which shows damage due to spark erosion. Note how babbitt surface has been progressively eroded going from right to left. Original babbitt surface is at lower right.

D10003 – Surface of thrust bearing shoe which shows damage due to spark erosion (same item as d 10 002). Note how babbitt surface has been progressively spark eroded going from left to right. Babbitt has been completely removed at lower right corner.

D10008 – Typical spark-tracks on a thrust bearing shoe.

D10009 – Fixed pad thrust bearing showing moderate amount of frosting due to spark erosion. Unit was equipped with OEM carbon brushes.

D10010 – Boundary between “Frosted” area and original surface as seen through 30x microscope. Same bearing surface as shown in d 10009.

D10049 – Fixed pad (tapered land) thrust bearing surface damaged by spark erosion. Full view of bearing. Same bearing as shown in d 10009.

D10051 – Spark tracks on tilting pad journal bearing.

D10054 – Thrust bearing pad, damage due to shaft currents.

D10055 – Enlargement of d 10054.

D10040 – Tilt pad journal bearing with spark tracks.

D10045 – Tilt pad journal bearing with spark tracks.

D10004 – Typical frosting on bearing and seal area. This case is unusual in that frosting extended around only 1/2 of the circumference.

D10005 – Severely pitted outside surface of rotor damaged by shaft currents.

D10006 – Spark-pit on shaft journal surface (enlarged).

D10011 – Turbine rotor that became magnetised to extent that nails and a small mirror could be hung from blades. Magnetism was due to an inadvertent rub between rotor and stationary parts.

D10012 – Ball bearing. Inner race damaged by currents. The surface of the small grooves shows fine frosting due to spark erosion.

D10038 – Spark erosion on anti friction bearing.

D10039 – Spark erosion on anti friction bearing.

D10052 – Spark erosion damaged coupling teeth.

D10060 – Gear damage (frosting) due to spark erosion.

D10061 – Gear damage (frosting) due to spark erosion.

D10062 – Gear damage (frosting) due to spark erosion.

Severe spark tracking in bushing seal of syngas compressor (38,000 hp, 11,000 rpm).

Bearing shoes (steel) welded to bearing cage during final episode of self-excitation and consequent thrust bearing failure. Ammonia plant, air compressor turbine, 10,000 hp, 8,000 rpm.

Shaft current damage on a gear wheel.

Spark pitting on a gear wheel key.

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