Make Use of Graphics
Your maintenance reports may contain all of the
information required to justify downtime windows, budget requests,
expanded testing programs, and training. But if people don't
understand the information, the reports won't matter.
Why might people not understand? Because:
The solution? Use graphics to emphasize what's important. Your
computerized maintenance management system (CMMS)
makes this surprisingly easy.
- They are skimmers, not readers. Managers are almost always
- They don't have your technical background. What is obvious
to you may be Greek to them.
- The key points don't stand out. They're lost in a sea of
First, decide the top five points to emphasize. Look at output
increased due to X, costs reduced due to Y, and so forth. Pick the five
(more is usually not better) with the greatest financial impact.
Export the relevant data from the CMMS to an Excel workbook. Then,
select a chart format that most clearly shows the information that
supports your intended point. A Pareto analysis makes this especially
compelling. In our next issue, we'll examine how to do that.
Tip, Part 10
Overheated motors use more energy and fail sooner. The
most easily corrected cause of motor overheating is often the most
neglected cause: restricted ventilation.
Keep motor vents clean to maintain required airflow. How often you
need to clean the vents depends on how dirty the environment is.
To develop an accurate cleaning schedule, you must first establish
baseline data. Begin by taking "as-found" data. Conduct a walking
Clean the dirty vents, wait a day, and take new thermal readings. You
now have baseline data you can compare with "as-found" data on future
inspections. Add vent cleaning to your PM schedule, adjusting the
interval per thermal imaging. Some motors might require vent cleaning
weekly, others only quarterly.
- Use a thermal camera to determine the motor temperature profile.
- Note which motors have dirty vents.
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Last summer, the main drive motor on an important piece
of production equipment would simply stop in the middle of the
afternoon. Restart wasn't possible for a few hours. This affected
delivery on the customer's orders for whom your company bought that
equipment. Your plant manager just received an e-mail from that
customer's purchasing manager wanting to know your company's plan
for preventing a repeat of last summer's late deliveries. Absent a
solid plan, they will find another supplier. How can you solve this
The answer to this question appears at the end of this
The configuration of a "vendor skid" or equipment
assembly makes perfect sense at the factory but may not be optimum for
repairs in your specific application. Similarly, a contractor may
install equipment correctly but sub-optimally for facilitating repairs.
Something as simple as moving a PLC panel 8 inches to the left to allow
room to swing the lift's boom in a specific path may save precious
You can reduce repair time by assigning someone to analyze a repair
in progress and determine how configuration changes can reduce the time
to perform specific steps -- or even eliminate those steps. An
industrial engineer does this to improve efficiency of production. You
can do it to improve efficiency of repair.
People sometimes refer to "current-limiting fuses."
How are those different from other fuses?
A fuse is an overcurrent protective device that contains a
current-carrying member. Under the overcurrent conditions it's
calibrated for, that member melts and opens the circuit.
A current-limiting fuse is calibrated to limit the duration and
magnitude of the current flow under a short-circuit condition within
current-limiting range (the range of short-circuit currents the fuse
will clear in less than ½ cycle). The upper part of this range is the
maximum interrupting rating.
NEC in the
Automation is a great thing, but it has its limits. One
such limit is the automatic restarting of a motor. The NEC prohibits
this if the restart can result in injury to people [430.43].
Interpret this prohibition strictly. Another way to say it is this:
If there's any way a restart might harm a person, don't automate it.
Good candidates for automatic restart include plant air compressors
and HVAC systems. With production equipment, the possibility of injury
or equipment damage usually makes this a bad idea.
Do you review safety information for completeness,
accuracy, and applicability? Doing so may spare you months of agonizing
therapy -- or worse.
Sure, your supervisor has the responsibility of giving you safety
information for any work you perform. Your supervisor is supposed to
find out what hazards may arise from that work, and determine the means
you can use to protect yourself.
But supervisors, being human, make mistakes. Do you want to
personally pay for someone else's mistake? Probably not. Help your
supervisor and yourself by methodically reviewing the safety
your supervisor provides. One way to do this is to "walk through"
the work. At each step, ask, "What are the possible dangers I could
Electrical Troubleshooting Quiz
The timing is a great clue. Even the customer realizes
this is a "summer issue." It's possible you need a different
motor. However, before going through that expense, you need to look at
the conditions in which the existing motor operates.
Because heat is part of the problem and ventilation is how you
heat, your first step will be to implement this newsletter's Motor
Maintenance Tip (Part 10). Last summer, the motor repeatedly operated
past its heat limit and shut down. Determine how close that motor is to
its heat limit now, when ambient temperatures are lower. If the motor
"down in the guts" of the equipment, adding a duct to supply
filtered air from a cooler location may solve the heat problem.
Check the motor to see if its insulation rating is appropriate for
the thermal conditions. Consider using a larger motor (more torque
the motor doesn't work as close to its limits) with motor speed
controlled by an electronic drive (consult your motor manufacturer for
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