When
equipment reliability and zero breakdowns
are the goals of a
Maintenance program, the best place to start is with
“basic training.”
By Terry Wireman,
Senior Industry Analyst,
GenesisSolutions
Click here for a printable 54k pdf file
One of
the latest buzzwords sweeping through plant engineering
and
maintenance circles is equipment
reliability. When equipment reliability is the goal,
the optimum situation is zero breakdowns. While
the possibility of zero breakdowns seems unrealistic to
some, that nevertheless is the target for many
organizations, especially those with quality programs
in which the goal is zero
defects.
An informal survey of
more than 2,000 seminar attendees conducted over a
two-year period asked what situations contribute to
break are related to basic maintenance, the basics are
precisely where many maintenance training programs fail
to focus. The basics highlighted in the survey fall
within three main categories:
1) Equipment
cleanliness,
2) Fastening
procedures and
3) Proper lubrication
procedures.
The survey examined the
breakdowns and what percentages of breakdowns are
attributable to each kind of situation.
Examining these three
areas will help explain why the basics of maintenance
training are so important and why so many equipment
breakdowns are related to the neglect of basic
maintenance training.
Equipment cleanliness
Consider the reasons
usually cited for keeping equipment clean: Easier
inspections, better employee morale, easier servicing,
less wear on moving parts, less contamination of
products, and better customer impressions.
While these reasons are
valid, what about technical reasons for keeping the
equipment clean? For example, consider components such
as motors, gear cases, and hydraulic systems. Why should
they be kept clean?
One reason is heat
dissipation. If a motor becomes dirty, the surface of
the motor becomes insulated. Being less able to
dissipate heat, the motor runs hotter. Most
manufacturers’ produce temperature/life curves that show
an inverse correlation between operating temperature and
motor life. As operating temperature increases, the life
of the motor decreases. And while it is true that the
motor will not fail immediately, what if you now get six
months’ service from a motor that should give 10 years
of service? Neglecting cleanliness creates unnecessary
motor failures and unnecessary maintenance expense.
The scenario is similar
for gear cases. If they become dirty, heat dissipation
decreases. If you use the manufacturer’s suggested
lubricant, it is now the incorrect lubricant, since the
operating parameters are different. The viscosity will
be too thin and the gear cases will wear faster. The
gear case will not fail immediately, but if it fails
once every six months instead of once every six years,
unnecessary maintenance expenditures result.
Consider, too, hydraulic
systems. The reservoirs are designed with enough surface
area to dissipate the heat generated during operation.
If dirt or contamination builds up on the tank, the
hydraulic fluid retains heat. Above 1250F or
1300F, depending on the hydraulic fluid and
its additives, the oil’s life is shortened by 50%
for every few degrees of temperature rise. As the oil’s
temperature continues to increase, the fluid varnishes.
Varnish particles can travel through a hydraulic system
and cause valves and other components to jam and fail.
Again, the failures are not immediate, but occur over
time.
These are just three of
many possible examples that illustrate the importance of
keeping equipment clean. How many plant personnel,
though, actually understand the technical reasons for
cleanliness? To ensure that the maintenance activities
carried out in a facility are cost effective, basic
maintenance training must include these critical topics.
Proper fastening
procedures.
Many maintenance
technicians are familiar with the process of rebuilding
automobile engines. One of the steps is to install the
engine heads. Part of the process entails the fastening
of the heads to the block with the head bolts. This is a
critical process because it seals the engine’s
compression chambers and its fluids. When observing the
installation of the head bolts, have you ever seen a
skilled mechanic use channel locks, vise grips,
adjustable wrenches, combination wrenches, or pipe
wrenches? Of course not! A skilled mechanic uses a
torque wrench to install head bolts. Basic high school
physics taught us that screw threads are two inclined
planes wedged against each other to provide the correct
tensile stress to hold a fastener in place.
Even though this is a
basic mechanical fact, it’s unlikely that most bolts in
your facility get tightened with a torque wrench.
Instead one of the other tools mentioned earlier is
used. The result is poorly installed fasteners that
eventually work loose, vibrate, wear, and ultimately
fail—all because the basics were ignored. Every
maintenance-training program should teach basic
fastening techniques.
Notice the patterns on
the heads of the bolts or fasteners. The pattern tells
us the hardness of the bolt. Even bolts that are the
same size physically require different amounts of torque
based on their hardness. How many mechanics carry a
torque table as well as a torque wrench? For that
matter, how many of them pay any attention to the proper
hardness of fasteners for specific applications?
If someone opened the
coupling guards in your plant, how many couplings would
have bolts that are too soft? A too-soft bolt stretches
and wears. It then elongates the coupling hole. The
result is coupling failure. Again, paying attention to
the basics will result in fewer breakdowns.
Basic lubrication.
In practice, how often is
the right lubricant applied in the right amount and at
right frequency with the correct application tool? Very
seldom, yet a large percentage of mechanical failures
(bearings, chains, gears, and sometimes belts) are
lubrication related.
In the hands of a worker
not trained in its use, a power grease gun is a lethal
weapon—for equipment, that is. Typically, a worker
places one of these high-powered lubricators on a small
pillow block bearing and pulls the trigger. How does the
worker know when the bearing has enough lubricant? When
the lubricant runs out the seals is the most common
answer. But that’s the wrong answer. Most pillow block
bearings are made to be filled only about one-third
full, leaving the remaining air space for heat
dispersion.
How many different
lubricants from different vendors are in a typical
facility? Usually many and that too can cause problems.
Workers should have and use lubricant interchange
charts. When lubricants are mixed, you can get
alkaloids, acids, thinning viscosity, thickening
viscosity, coagulation—in short, a mess. Lubricant
contamination is another cause of equipment failure. The
most common contaminant is water. A water content of
just 0.002% in a lubricant can reduce the fatigue life
of an antifriction bearing by as much as 80%.
With such a minute amount
of water in a lubricant able to cause problems,
shouldn’t your workers pay attention to re-lubrication
when equipment is washed down in a sanitizing cycle or a
steam-cleaning period? Do they, or is the water left to
work its way out by it destroying the bearing in the
process? Preventing contamination includes the correct
storage of lubricants. What’s the proper way to store a
drum of oil or grease? Horizontally or vertically? The
answer is horizontally. Water can accumulate on the top
of a drum and through the normal heating and cooling of
a day be drawn down the screw threads of the bung and
into the lubricant. Two-thousandth percent (0.002%) is
not much water.
More uptime, small
investment
Just imagine the results
if you could eliminate the breakdowns in your plant that
have their root causes in lack of cleanliness, incorrect
fastening, and improper lubrication procedures. Would
your figures agree with the survey, which showed that
almost 50% of equipment breakdowns have a root cause in
one of the aforementioned areas? Would employing the
basics cut the number of breakdowns in half? If so, how
much would it cost you to get such results? Not much,
just training costs and the cost of the time to allow
workers to do the job right the first time.
Most organizations do not
stress maintenance basics, though. And in some
companies, especially those that want the operations
group to take over some of the basic maintenance duties,
the situation probably will not improve. If the
maintenance group is not doing the basics correctly now,
will involving operations personnel make any difference?
No, it will not. Training in the basics for everyone
involved in maintenance is critical to progress toward
zero breakdowns.
For More information,
Contact:
Terry Wireman,
Senior Industry Analyst
|
