How Multiple Condition-monitoring Technologies
Produced Big Cost Savings
Over the last two years, the Deer Island Water Treatment
Plant has established an effective condition-monitoring maintenance program.
The maintenance staff has been performing vibration monitoring and spectral
analysis, oil analysis, acoustic ultrasonic detection, ultrasonic thickness
testing, laser alignment and infrared thermography tasks.
Reliability-centered maintenance (RCM2) analysis of
the plant's
primary scum pumps recommended a preventive maintenance task using acoustic
ultrasonic detection to monitor the motor and pump bearings to provide
advance warning of potential failures.
Using our ultrasonic detector, condition-monitoring
engineer Dan Parry found unacceptable noises and noise levels in 10
of the 14 primary scum
pumps, indicating potential bearing problems. Maintenance planner
Michael Costa then collected lubricating oil samples from six of the
pumps' gearboxes.
The oil analysis results showed high viscosity, indicating that the wrong
lubricating oil had been used. The oil in all of the pumps was changed
to the correct lubricant and ultrasonic monitoring was repeated. This
time, only two pumps were found with unacceptable noise levels. An alignment
check was scheduled before considering replacement of the bearings.
While checking one machine's alignment with laser
alignment technology, mechanics Bob Greatorex and Peter McGee immediately
saw that the coupling
was in bad shape and noted that the machine was badly out of alignment.
A new coupling was installed and the machine was laser aligned. Repeated
ultrasonic detection confirmed that the problems had been solved. No further
maintenance was required.
Preventive maintenance expenditures of about $280 for ultrasound,
oil analysis, coupling replacement and alignment resulted in cost savings
that
can be estimated in two ways:
1. If one machine had been allowed to run to failure, it
would have cost about $5,600 in parts and labor to completely rebuild it.
2. If more intrusive maintenance (replacement of bearings)
had been performed after the first round of ultrasonic detection monitoring,
the total maintenance
cost for one machine would have been about $3,400.
Avoided costs for this maintenance event range from $5,320
for scenario No. 1 to $3,120 for scenario No. 2 for each machine. When
applied to all
14 primary scum pumps, expending $3,920 in preventive maintenance provided
cost savings of $43,680 to $74,480, while increasing equipment availability
and reliability.
Condition-monitoring techniques used at Deer Island have provided many
such examples of the benefits and return on investment of proactive maintenance.
The Massachusetts Water Resources Authority (MWRA) is a large,
unionized public utility serving people in the Boston metropolitan area.
In 2000, the MWRA embarked on a comprehensive, multiphased asset management
initiative. Its program includes dedicated staff along with a diverse senior
management steering committee that organized early, communicated often,
and conducted research and cross-industry benchmarking. This effort allowed
for a timely implementation of best practices, resultant efficiencies and
cost-saving benefits. The MWRA program is considered to be a model in public
sector asset management.
Submitted by Nancy Ettele, Massachusetts Water Resources
Authority, Deer Island Treatment Plant
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