Page 64 - Intro Predictive Maintenance

Role of Maintenance Organization 55

Frequent measurement and feedback will revise performance to achieve the desired
levels.

3.3.4 Failures That Can Be Prevented
Failure modes, effects, and criticality analysis (FMECA) provide a method for deter-
mining which failures can be prevented. Necessary inputs are the frequency of occur-
rence for each problem and cause combination and what happens if a failure occurs.
Criticality of the failure is considered for establishing priority of effort. FMECA is a
bottom-up approach that looks at every component in the equipment and asks: “Will
it fail? And if so, how and why?” Preventive maintenance investigators are interested
in how a component will fail so that the mechanism for failure can be reduced or
eliminated. For example, heat is the most common cause of failure for electro-
mechanical components. Friction causes heat in assemblies moving relative to each
other, often accompanied by material wear, and leads to many failures. Any moving
component is likely to fail at a relatively high rate and is a fine candidate for preven-
tive maintenance. The following are common causes of failure:

Abrasion Friction
Abuse Operator negligence
Age deterioration Puncture
Bond separation Shock
Consumable depletion Stress
Contamination Temperature extremes
Corrosion Vibration
Dirt Wear
Fatigue

3.3.5 Maintenance to Prevent Failures
Cleanliness is the watchword of preventive maintenance. Metal filings, fluids in the
wrong places, ozone and other gases that deteriorate rubber components—all are
capable of damaging equipment and causing it to fail. A machine shop, for example,
that contains many electromechanical lathes, mills, grinders, and boring machines
should have established procedures for ensuring that the equipment is frequently
cleaned and properly lubricated. In most plants, the best tactic is to assign respon-
sibility for cleaning and lubrication to the machine’s operator. There should be proper
lubricants in grease guns and oilcans, and cleaning materials at every workstation.
Every operator should be trained on proper operator preventive tasks. A checklist
should be kept on the equipment for the operator to initial every time the lubrication
is done.

It is especially important that lubrication be done cleanly. Grease fittings, for example,
should be cleaned with waste material both before and after the grease gun is used.
Grease attracts and holds particles of dirt. If the fittings are not clean, the grease gun
could force contaminants between the moving parts, which is precisely what should