Page 17 - Industrisal Technology EXTRA 3rd August 2020

The bearing pairs on the third line were being
overloaded. The premature bearing wear had
allowed misalignment with the preceding and
following lines. Subject to how long the unit was
continuing to run, the case bores and – ultimately –
the second line wheel and fourth line pinion shaft
respectively were also destroyed.”

Thrust overload
On further analysis, the prime contributor to the
failure was found to be thrust overload, which could
be seen from the asymmetrical bearing inner race
wear, (always in the same direction). This had also
worn the respective bores.Baggaley explains the
assessment: “The gear case was set up and clocked
on the horizontal borer. This confirmed that the
general accuracy of the gear case was good – parts
of both the bore pair were unworn giving us the
original centrelines. Accordingly, the line could be
re-bored oversize with a counter bore added for a
Top Hat flange.
“The low speed shaft interface was also
damaged internally where it grips the Input shaft –
unusually, the pick-up was caused at original As part of the test, paint and dispatch procedure,
installation when the parts were mated. While the internals were reset and gear contacts verified.
many high value components had been essentially The unit was spin tested with bearing temperatures
written-off, we were keen to find out whether monitored to ensure they plateau at an acceptable
refurbishment was still practically and commercially level. The lube system was also refurbished. These
viable.” particular units were upgraded. An additional large
Dana’s servicing team undertook in-depth area high efficiency filter together with a remotely
investigation, resulting in a detailed report, with monitored particulate sensor were added. The unit
fully-costed recommendations. Any damage that was tested with a throw away filter element, which
rendered parts unusable were illustrated and was then replaced with new on completion ready for
explained; reusable and replacement parts were despatch.
clearly identified, allowing for accurate rebuild costs On completion of the project, Dana were able to
to be quoted. Any optional elements and additional return the unit ready to fit, demonstrating that
recommendations were made clear to the customer. refurbishment can be possible, even for extensive
The build and refurbishment – with new and damage, and at less than half the cost of a new
existing parts – was undertaken by the service unit. With the choice between OEM gear parts or
team. Bore liners were fitted prior to installing reverse-engineered items, costs to the customer
bearings and axial floats set, checked and recorded. could be further reduced and lead-time cut

August 2020 • INDUSTRIAL TECHNOLOGY EXTRA! • p17