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Maintenance
Overcoming a
Common Maintenance Myth
You must follow factory maintenance requirements to
the letter.
The people who wrote the factory maintenance requirements did so
with
certain assumptions in mind about how the equipment would be used and
under what conditions. But your application may be outside those
assumptions.
Does this mean you should disregard factory maintenance requirements?
No, and it doesn't mean you should make an "educated guess" on
modifying
those requirements either. Just as that factory team doesn't know
everything about your operations, you don't know everything about their
product. You don't, for example, handle the service and support issues
that were inputs to those maintenance requirements.
Contact the factory and discuss your application so an applications
engineer can provide you with the proper guidance and reduce your
downtime. Getting suggested changes in writing will help you assert a
warranty claim, if the need arises.
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Repair
Electrical
Troubleshooting Quiz
Beth is an operator on the plant floor. She complained
that her machine sometimes gives her a shock when she touches it.
Occasionally, her control panel just blinks out, and she has to reset
it
to get the display to come back on. What is the most likely cause of
this, and how should you check for it?
The answers to this question appear at the end of this
newsletter.
Overcoming a Common
Repair Myth
If a production machine goes down, you must send
someone to work on it immediately.
This idea is responsible for millions of dollars of lost revenue
each
year. Yes, you need to get equipment running again. But not all
equipment is created equal, and your people are spread thin. You must
establish priorities and make choices.
If Press #8 can produce 100 parts an hour and your factory needs 200
parts per day, Press #8 can be down for a long time. If your facility
can sell everything that comes off Line B, then Line B is "critical
equipment." Any revenue lost on Line B is lost forever. (Equipment can
also be critical for other reasons. For example, it's a production
bottleneck or its output is high revenue.)
Suppose the main drive motor for Line B goes down early in the day.
Replacement is a two-person job, and you have three people available at
the moment. You send all three, so one can conduct support activities
for the other two and handle all those little side tasks that slow a
job
down.
Minutes later, you get a call that Press #8 went down. The department
supervisor is screaming at you to get Press #8 up as soon as possible,
but you've just confirmed the factory won't need any more parts from it
for another eight hours -- and those are low-revenue parts anyhow.
The smart choice here is to keep that Line B repair job moving as fast
and efficiently as possible. Ignore Press #8 for at least four hours or
until Line B is up. During the wait, you will likely free up someone
else to repair Press #8. Do not pull people off of the critical job to
handle the non-critical one.
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Operation
Practical Implications
of OSHA 1926.151
This addresses fire prevention. The main concept is
pretty simple. Keep combustibles and ignition sources separated. The
rub
is this: Applying this concept is complex. That's why both OSHA and the
NEC devote considerable space to requirements for accomplishing this.
In
general, think in terms of what can burn and what can spark -- and
don't
let them come together. Some specific tips:
- When working around flammable gases or liquids, you are working in
a
"hazardous location" (defined in Article 500). Use only equipment
approved for use in that location. You could blow up an entire facility
with a penlight, so don't take anything for granted.
- Don't allow combustible materials to accumulate.
- Understand the fire characteristics of materials being stored, and
provide the proper enclosures and ventilation.
- Don't stack anything closer than three feet to overhead
sprinklers.
NEC on the Production
Floor
Walk into the typical industrial or commercial
facility,
and an hour later you can walk back out with a hefty list of Article
110
violations. In our previous issue, we discussed four common violations.
Here are four more:
- Unlocked doors on outdoor transformer enclosures
[110.31(D)].
If unqualified persons could gain access to your enclosures, lock those
enclosures. (In an actual case, kids from a nearby apartment complex
climbed over the perimeter fence). To prevent tragedy and massive
liability, study 110.31(D) closely -- and perhaps commit it to
memory.
- Insufficient working space [110.32]. In a misguided attempt
to maximize revenue per square foot, people often nitpick code
requirements to determine the absolute minimums for working space. They
fail to realize that working space is an investment, not a cost.
Cramped
working space is unsafe, and it inhibits the very maintenance that
prevents downtime. It also extends downtime by making repairs difficult
and unsafe. This is why the first words of 110.32 are "Sufficient
space."
- Using the 3-foot minimum clearance as the maximum clearance
[110.33]. OSHA and the NEC do not, as commonly misunderstood,
dictate you must provide exactly 3 feet of clearance (or maybe a
little less, if you can hold your ruler at an angle) in front of
energized parts. In fact, the minimum may be more than 3 feet
(Table
110.34(A) and OSHA 1926.403). Operational and other issues might
provide
bottom-line reasons to go beyond NEC and OSHA requirements.
- Failure to properly illuminate working spaces around electrical
equipment [110.34(D)]. People can't work safely in the dark. Tip:
Try to ensure the illumination doesn't draw its power from the
equipment
it illuminates. For example, if your facility has two service
entrances,
power the lighting for each one from a breaker at the other service
entrance. When production stops, do you want to wait while your repair
team runs extension cords and cranks up portable generators?
Manufacturers' Corner
10 Benefits of
Adjustable-Speed
AC Drives
Since motors consume a large amount of the energy
produced in this country, it's only fitting that manufacturers and
end-users continue to look for ways to cut down on the amount of energy
they consume. Automatically controlling the speed of a motor as it
relates to changing loads is much more efficient than running a motor
at
a constant (fixed) speed. That's where adjustable-speed drives (ASDs)
come into play.
The folks at ABB have developed a list of 10 benefits users realize
when
operating their motors with ASDs, including:
- Controlled starting current
- Reduced power line disturbances
- Lower power demand on start
- Controlled acceleration
- Adjustable operating speed
- Adjustable torque limit
- Controlled stopping
- Energy savings
- Reverse operation
- Elimination of mechanical drive components
For an expanded discussion on these 10 benefits, visit ABB's Drives
Portal on the Web.
Quiz Answers
Answer to
Electrical Troubleshooting Quiz
These are classic symptoms of flashover. To test for
it,
use your digital multimeter (DMM) with peak recording and measure the
potential between metallic objects in the area. To fix the problem,
install equipotential bonding (Article 250, Part V).
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