Machinery Lubrication July August 2008

HYDRAULICS AT WORK
mining shovels. This involved changing out every hose on the
machine every 18 months. So whenever a shovel was down
for planned maintenance, a portion of the hoses was
changed out, beginning with the oldest first.
The hydraulic hose supplier who devised the program was
somewhat of a hero because, prior to its implementation,
improvised hose replacement in response to in-service failures
had resulted in machine availability falling to as low as
65 percent.
When a multimillion-dollar shovel stops, so does a multimillion-dollar
fleet of haul trucks. So downtime is a major cost. But
large-diameter, multispiral, hydraulic hoses aren’t cheap either.
Not All Hoses Are Equal
I couldn’t argue with the success of the hose replacement
program; however, I did point out its fundamental flaw. It
treated all hoses equally. The 80/20 principle suggests it
would be highly unlikely that 50 percent of the hoses were
responsible for 50 percent of the in-service failures and
downtime.
So I explained to my client if he were to look at the historical
data, he should expect to see a skewed picture: that 20
percent of the hoses were causing 80 percent of the in-service
failures and downtime.
In fact, the available data revealed less than 20 percent of
the hoses were responsible for nearly 90 percent of the failures
(note that we are comparing two sets of unique data, so
the comparative split doesn’t have to add up to 100).
This discovery not only reduced my client’s hose bill (oils
spills, ingression of air and other contaminants), but the risk
associated with the introduction of human agents as a result
of unnecessary hose replacement was eliminated as well.
Conclusion
As this story illustrates, if you are applying linear thinking
to any facet of your maintenance strategy, it’s wrong. An 80
percent reduction in your maintenance costs will likely come
from 20 percent of your maintenance effort. The trick is in
identifying the significant 20 percent.
About the Author
Brendan Casey has more than 19 years experience in the maintenance,
repair and overhaul of mobile and industrial hydraulic equipment. For more
information on reducing the operating cost and increasing the uptime of your
hydraulic equipment, visit his Web site: www.InsiderSecretsToHydraulics.com.
12 July - August 2008 machinerylubrication.com Machinery Lubrication