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Maintenance
Here's a few more sets of three we thought would be
worthwhile to share with you on the topic of maintenance management.
Three Ways to
Reduce Maintenance Costs
- Use mass relamping. Changing lamps as
they fail multiplies labor costs enormously. Research mass relamping,
and consider outsourcing this function.
- Test. Scheduling PM work purely by the calendar doesn't
account for actual conditions, so it tends to raise costs. Test, so you
can follow the "If it aint broke, don't fix it" rule.
- Monitor. Power monitors, motor monitors, and similar devices
reduce maintenance labor -- they also alert you to take corrective
action before an emerging problem causes an unscheduled
shutdown.
Three Ways to be
Kind to the Training Budget
- Tie training to revenue per equipment.
The single largest training cost is avoidable loss of revenue due to
critical equipment downtime. While this cost isn't in the training
budget, tying training -- even general training -- to specific equipment
by revenue will improve the company's bottom line and help justify
training expenditures.
- Supplement formal training. Subscribing to related
newsletters and magazines fills holes in the formal training, and
refreshes the lessons learned.
- Use "Those who teach, learn." When someone returns
from formal training, assign that person the job of giving a short
presentation within 30 days. The preparation for this presentation will
strongly reinforce the learning you paid for. To make this effective,
ban the use of PowerPoint. This isn't about spending time manipulating
slides. It's about communicating.
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Repair
PLC Troubleshooting
Quiz
Based on some feedback we received following the release
of our first issue, we'll now include the answers to the quiz questions
in the same issue in which we post the questions.
For this issue,
we decided to post the same questions as last time, but also list the
answers to these questions at the end of the newsletter. This will be
our presentation format from this point forward. No peeking now!
- A system under PLC control suddenly stopped running. What is the
first thing you should check?
- If a PLC controls four valves for a mixing tank, but only one of
those valves fails to open, what (in order) are the first three things
you should check?
- You have been getting complaints about erratic operation of a
newly-installed PLC-controlled system. Valves are cycling, and there are
wild oscillations in temperature and pressure sensors. What is the most
likely cause of these problems?
The answers to these questions appear at the end of this
newsletter.
Operation
The Practical
Implications of OSHA 1926.102
This regulation addresses eye and face protection.
Anytime you feel lax about eye protection, just remember that a blind
electrician is unlikely to find work. Always wear the proper eye
protection. Review the relevant safety procedures prior to starting any
task. If you are pressed for time, remember that loss of a few minutes
on the job is recoverable, but loss of one or both eyes is
permanent.
A lack of a posted sign doesn't mean you don't need eye protection. Wear
eye protection any time you are around rotating equipment or live
electrical equipment. Equipment has no way of knowing if you are on
break, just passing through, or actually on the clock in your work area.
Even off work, this applies (hint: read the manual for your
lawnmower).
Rules of thumb:
- At a minimum, wear safety glasses any time you are on the job
site.
- Wear goggles where dangerous chemicals are present, regardless of
whether there is a known splash hazard or not. Seals do leak and
explosions do happen.
- Wear a face shield where there's the possibility of an arc flash or
arc blast. You will not have time to react.
- When in doubt, overdo protection. Goggles may seem silly if there
really isn't a splash hazard after all -- but no harm done. If acid
splashes your eyes, it's too late to put the goggles on.
Specifying a
Replacement Motor
When a motor fails, you may replace it with a new one.
If the new motor fails in six months, the typical response is to try
some other manufacturer's motor. But the manufacturer is rarely, if
ever, the problem.
To prevent repeated motor replacement, install the right replacement
motor the first time. Part of doing that is assessing the reason for
failure. For a large motor, have a motor shop do an "autopsy" and
provide advice. You may pay a premium for a shop to do this on a
moment's notice, but that's cheaper than another downtime incident and
subsequent replacement.
Some things to look for:
- Wrong insulation rating. Ensure your motor is rated for the
ambient temperature where you install it.
- Motor/drive mismatch. You may need a different drive,
different motor, or both.
- Motor/load mismatch. Maybe the motor is too small, or you are
using a Design B where a Design C belongs.
NEC on the
Production Floor
Mechanical Execution of Work [110.12]
The NEC requires installing equipment in a neat and
workmanlike manner, but it doesn't define that. It's hard to obtain a
consensus on particulars that apply to every job, but some general
considerations always apply:
- Everything clearly labeled. This reduces troubleshooting
time, and makes retrofits and upgrades much easier. For best results,
use a labeling machine -- these are easier to use than many people
think.
- Wires neatly bundled. Nothing screams "incompetent" louder
than a bird's nest of wires. Part of effective maintenance is keeping
enclosures clean -- which is about impossible with wires going every
which way. This situation impedes troubleshooting, also.
- Proper bends in wires. Every conductor has a bend radius
specification. Making sharp bends for aesthetics is unnecessary, damages
insulation, and can lead to system failure. Make your bends in smooth
curves, respecting the radius limit.
- Holes made properly. Use the right hole-making tools (e.g.,
punch and die set), so your holes have smooth and regular shapes.
Butchering out a square hole with a drill and file, for example, is
unworkmanlike and will leave an ugly hole. It's also inefficient.
- Consistency. It's just sloppy when every cabinet and junction
box is done a different way. Develop and adhere to standards for your
facility.
Manufacturer's Corner
Old Equipment: Repair or
Replace?
When you're dealing with an unreliable machine that is
hindering productivity or driving up your operating costs, this can be a
difficult question to answer. However, our friends at the Cat Rental
Stores have developed this list of factors to consider when determining
whether it's better to make repairs to that older piece of equipment or
bring in a new machine to replace it.
- Resale value. Start your evaluation process by obtaining a
quote to trade in the machine.
- Repair costs. Seek a quote for the repair including labor and
replacement parts. The machine's age may affect the cost of labor.
Maintenance on older machines can be more involved and require more work
due to limited availability of parts.
- Estimated downtime. Find out how long the repairs will take.
Lengthy delays can have a cascading effect on your work schedules and
productivity.
After gathering all this information and running the numbers, you may
decide that once repaired this piece of equipment will continue to
provide value to your business. On the other hand, you may decide
investing in this older machine will yield diminishing returns. In this
case, it would be better to put the repair money toward a new, more
efficient piece of equipment.
If you opt for replacement, your next question should be: purchase or
rent? For some help in this area, check out these past articles that ran
in EC&M.
Equipment
Leasing: Is it Right For You?
Renting
Makes Sense
Quiz Answers
Answers to PLC
Troubleshooting Quiz
- If a system under PLC control suddenly stops
running, the first thing you should check is the system power.
- If a PLC controls four valves for a mixing tank but only one of
those valves fails to open, the first three things you should check are:
signal to the valve, operation of the valve, input to the PLC for the
control loop of that valve.
- If valves are cycling and there are wild oscillations in temperature
and pressure sensors in a newly-installed PLC-controlled system, the
most likely cause is noise induction due to improper wire routing. To
fix this, separate the sensor wiring from the power wiring.
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