Page 337 - Handbook of Materials Failure Analysis

334 CHAPTER 13 A concise filtergram wear particle atlas

(a) 50µm (b) 50µm
FIGURE 13.34
The varnish spherical particles from a hydro turbine oil samples (200 ): (a) a brown varnish
spherical particle; (b) a yellow varnish spherical particle.

Figure 13.35 shows the typical copper alloy wear particles. Figure 13.35a is a
copper alloy fatigue wear particle (L240 μm). The particle could be from the bearing
cage. Figure 13.35b is a copper alloy sliding wear particle (L100 μm) from an oil
filter in a geothermal steam turbine.
The oxide film can form on copper alloy wear particles by the heat affect. After
the oxidation, copper alloy wear particles appear different colors. Figure 13.36a–d
displays the copper alloy wear particles with different oxide films, coloring from
dark-brown to green.
The light-green copper alloy wear particle (Figure 13.36d) is a particle was from
an oil sample taken from the oil return line of the generator babbitt bearing. So it was
misconceived as babbitt alloy wear particle with oxide film. However, ESEM/EDS
analysis results (Figure 13.37) turned out to be a brass wear particle.

CASE 5: THE IMPENDING CATASTROPHIC WEAR IN A GEARBOX
(250 Kw) DUE TO THE OIL STARVATION
A three-stage reducer gearbox (250 Kw) in a paper mill (Figure 13.38a) suffered an
impending catastrophic wear due to the oil starvation. In the gearbox, lubrication oil
was supplied by the pipelines to each gear and bearing. When the routine wear par-
ticle analysis detected the wear issue, an emergency shutdown was implemented for
the inspection. Upon the opening the inspection window in the gearbox, the problem
was revealed; the pipeline supplying the oil to the side bearing (Figure 13.38b) had
been blocked by pulp fibers. Hence, severe wear occurred in the bearing. Owing to
the wear particle analysis, the impending catastrophic wear was remedied in a
timely manner.